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Effect of protein to energy ratio on growth performance and body composition of red tilapia reared i

Thu, 29 Jul 2010 22:35:00 +0000 — Thu, 29 Jul 2010 22:35:00 +0000

INTRODUCTION The "red" tilapia has become increasingly popular because its similar appearance to the marine red snapper gives it higher market value. The original red tilapias were genetic mutants. The first red tilapia produced in Taiwan in the late 1960s, was a cross between a mutant redish-orange female Mozambique tilapia and a normal male Nile tilapia. It was called the Taiwanese red tilapia. Another red strain of tilapia was developed in Florida in the 1970s by crossing a normal coloured female Zanzibar tilapia with a red-gold Mozambique tilapia. A third strain of red tilapia was developed in Israel from a mutant pink Nile tilapia crossed with wild Blue tilapia (Popma and Masser, 1999). Jauncey and Ross (1982) found that optimum dietary protein level for fish was affected by balance between dietary protein and energy, amino acid composition, digestibility of dietary protein, the physiological status of the fish and the level of food intake. Fish require energy for growth, activity and reproduction. The rate of energy utilization is called metabolic rate. Factors affecting the metabolic rate in fish are temperature, species, age or body size, activity, physical condition, body functions and water chemistry parameters such as oxygen or carbon dioxide saturation, pH and salinity (Wilson 1977). Providing the exact amount of energy in the diet of fish is important, because if the useful energy is too high the consumption of protein and other nutrients may be restricted and growth is retarded. Furthermore excess of energy may produce fatty fish. This can be undesirable especially if it reduces the dress-out yield and decrease the durability of the frozen fish (Lovell, 1989). On the other hand, when the diet is deficient in energy, dietary protein will be used as an energy source (Cowey, 1980). The more protein is used for energy, the more ammonia is produced, and the more energy is lost as heat (Cho and Kaushik, 1985), consequently, less protein will be retained in the fish body. Therefore, the proper balance between dietary protein and energy is therefore essential in fish feed formulation. The aim of the present investigation is to find the optimum protein and energy (P/E ratio) required for the best growth performance, feed utilization, and proximate analysis of red tilapia fry and fingerlings. MATERIALS AND METHODS The present study was carried out at the Laboratory of Fish Nutrition, Faculty of Agriculture Banha University. Experimental Fish Red tilapia fry and fingerlings were obtained from a finfish hatchery owned by GAFRD at Abu Telaat, west Alexandria. Fish were adapted for two months by gradually decreasing water salinity and finally reared in fresh water. For each experiment, 27 rectangular Tank 100×40×50 cm (200 liter for each) were used to represent 9 treatments (3 replicates for each treatment), and each Tank was stocked with 40 red tilapia fry (0.70 - 0.82 g, the first experiment) or 20 fingerlings (9.06 - 9.43 g for the second one). Nine experimental diets were formulated to contain 3 protein levels, 25, 30 or 35%, within each protein level 3 energy levels were tested 2400, 2800 or 3200 kcal ME/kg diet, therefore 9 diets with different protein/energy ratios were obtained and fed to red tilapia fry and fingerlings in two separate experiments. Formulation of the experimental diets is illustrated in Table 1. For the first experiment, fry were given the diets at a daily rate of 20% (during the 1st month) and then gradually decreased to 10%(2nd month). In the second experiment, red tilapia fingerlings fed the experimental diets at a daily rate of 10% (during the 1st month), 7%(2nd month) and 4% (during the last two months) of the total biomass during the experimental period 6 day/week (twice daily at 9.00 am and 3.00 pm) and the amount of feed was bi-weekly adjusted according to the changes in body weight throughout each experimental period (60 or 75 days for the first and the second experiments, respectively). Calculation: Specific growth rate (SGR) = 100 Where:- Ln = the natural log, W1 = initial fish weight; W2 = the final fish weight in "grams" and t = period in days. Weight gain (WG) = final weight (g) - initial weight (g) Feed conversion ratio (FCR) = feed ingested (g)/weight gain (g) Protein efficiency ratio (PER) = weight gain (g)/protein ingested (g) Chemical analysis: Moisture, dry matter (DM), ether extract (EE), crude protein (CP), crude fiber (CF) and ash contents of diets and fish were determined according to the methods described in AOAC (1990): dry matter after drying in an oven at 105°C until constant weight; ash content by incineration in a muffle furnace at 600°C for 12 hrs; crude protein (N×6.25) by the Kjeldhal method after acid digestion; and ether extract by petroleum ether (60-80°C) extraction. At the end of the experiment, three fish were randomly taken from each aquarium (9 fish for each treatment) and exposed to the chemical composition of whole fish body according to the methods of AOAC (1990). Statistical analysis The statistical analysis of data was carried out by applying the computer program, SAS (1996). RESULTS AND DISCUSSION Growth performance of red tilapia fry and fingerlings: At the end of the experiment increasing dietary protein and energy level, contents significantly increased BW and BL, weight gain (WG) and specific growth rate (SGR) of red tilapia fry and fingerlings. These results may indicate that, protein requirements for red tilapia fry and fingerlings reared in tanks lie above 25% crude protein and these results are in complete accordance with those reported by Cruz and Laudncia (1976). They showed that the dietary protein requirements of tilapia for fast growth at a size of 10-30 g lie between 25 to 30%. Viola and Zohar (1984) showed also that, increasing dietary protein level for hybrid tilapia ( O. niloticus × O. aureus ) from 25% to 30% or 35% significantly increased growth rate. Also, El-Dahhar (1994), found that WG of O. niloticus fry and fingerlings linearly increased with increasing diet crude protein contents. Abdel-Hakim and Mustafa (2000) found that dietary protein requirements for Nile tilapia, O. niloticus reared in cages and depending only on artificial feeds lie between 28-30%. Also, Abdel-Hakim et al., (2001) demonstrated that, increasing dietary protein level from 25 to 30% significantly (P<0.05) increased fish BW, BL and SGR of Nile tilapia, O. niloticus reared in tanks. Also, Wafa (2002) with hybrid tilapia ( O. niloticus × O. aureus ) and Soltan et al., (2002) with Nile tilapia ( O. niloticus ) found that, BW, BL and WG increased significantly (P<0.001) with increasing dietary protein from 25 to 30%. Al-Hafedh (1999) found that, SGR of Nile tilapia was significantly increased as diet protein level increased from 25-45% (with increment of 5%). Also, Ogunji and Wirth (2000) with the same fish specie found that, SGR increased with increasing dietary protein level from 7.3 to 44.24%. On the other hand, Clark et al., (1990) found that SGR of Florida red tilapia did not differ significantly when fish fed diets contained 20, 25 or 30% crude protein. Concerning the effect of dietary energy level on average BW, BL, WG and SGRTables 2 and 3 show that, BW, BL, WG and SGR of red tilapia fry and fingerlingssignificantly increased with increasing dietary energy level from 2400 to 2800 and 3200 kcal ME/Kg. These results indicated that, energy requirements for red tilapia fry and fingerlings reared in tanks must be above 3000 kcal/kg diet, excess energy may produce fatty fish, reduce feed consumption (reducing total protein intake) and inhibit proper utilization of other feedstuffs. Therefore, it is critical to obtain the proper protein to energy (P/E) ratio in a diet for the most economical production of tilapia (Shiau and Haung,1990). The greatest final BW (13.41 g), BL (8.57 cm) WG (12.60 g) and SGR (4.68) for red tilapia fry were achieved with the diet contained 35% protein and 3200 kcal ME/kg. This diet presumably contained the most appropriate P/E ratio of 110.3 mg protein/kcal. Also the lower final BW (6.22 g), BL (6.23 cm), WG (5.42 g) and SGR (3.42) were achieved with the diet contained 25% protein and 2400 kcal ME/kg (P/E ratio of 105.6 mg protein/kcal). Similar results were also obtained for red tilapia fingerlings (Table 3) where the greatest final BW (34.67 g), BL (12.01 cm), WG (25.31 g) and SGR (1.75) for red tilapia fingerlings were achieved with the diet contained 25% protein and 2400 kcal ME/kg (P/E ratio of 105.6 mg protein/kcal)., also the lower final BW (23.28 g) , BL(9.59 cm), WG (14.22 g) and SGR (1.26) were achieved with the diet contained 25% protein and 2400 kcal ME/kg (P/E ratio of 105.6 mg protein/kcal). Results obtained in the present study are relatively consistent with Jauncey (1982) who found that, the maximum growth of S. mossambicus was obtained with diets of P/E ratio of 116.6 mg protein/kcal. Mazid et al., (1979) obtained the maximum growth for tilapia zilli fed a diet contained 35% protein with a P/E ratio of 103 mg protein/kcal. Ross (1982) found that, the optimum protein-energy ratio was 78-90 mg protein/kcal for tilapia mossambicus fed 30-35% protein diets and 3836-3860 kcal ME/kg. For Nile tilapia, Soltan et al., (2002) found that the highest BW, BL, WG and SGR were achieved with the diet contained 30% protein and 3000 kcal ME/kg (P/E ratio of 100 mg protein/kcal) and the lowest BW, BL, WG and SGR were achieved with the diet contained 20% protein and 3600 kcal ME/kg (P/E ratio of 55.5 mg protein/kcal). Similar results were obtained with blue tilapia, O. aureus, (Winfree and Stickney, 1981), O. niloticus (Teshima et al., 1985; Siddiqui et al., 1988 and El-Sayed and Teshima, 1992), Tilapia zilli (El-Sayed, 1987), hybrid tilapia, O. niloticus × O. aureus (Shiau and Huang, 1990). Feed utilization: Feed intake: Feed intake (FI) during the experimental period were 13.55, 14.90 and 15.71 g/fish for red tilapia fry fed diets contained 25, 30 and 35% protein, respectively with significant differences between these means (Table 4) and the same trend was also observed with red tilapia fingerlings (Table 5) where increasing in dietary protein content from 25 to 30 or 35% significantly increased FI. These results indicated that, as protein content in red tilapia fry diets increased, FI will be significantly increased. El-Dahhar (2000) reported that, feed consumption increased as dietary protein increased for tilapia fry. Also, Soltan et al., (2002) indicated that, increasing dietary protein from 20 to 25 or 30% in Nile tilapia diets significantly increased feed consumption. On the other hand, Cisse (1996) found that, a change in protein contents from 20 to 30% for tilapia fish did not have any significant effect on the quantity of feed consumed. With regard to the effect of dietary energy content, results presented in Tables (4 and 5) indicated that, increasing energy content in tilapia diets significantly increased FI and this subsequently followed by increase in all growth parameters such as BW, BL, SGR and WG of red tilapia fry and fingerlings. El-Dahhar and Lovell (1995) described that excess energy in tilapia diets may reduce feed consumption. Our results support those of Winfree and Stickney (1981) and Jauncey (1982) in that tilapia regulate their food consumption according to energy intake. For fry and fingerlings red tilapia fed the diet contained 30%CP and 3200 Kcal ME/kg diet (P/E ratio of 110.3 mg protein/kcal) consumed the higher amount of feed whereas fish fed the diet contained 25% CP and 2400 kcal ME/kg (P/E ratio of 105.6 mg protein/kcal) consumed the lower amount of feed (12.15 g/fish). Wafa (2002) found that, hybrid tilapia ( O. niloticus × O. aureus ) increased with increasing P/E ratio from 80 to 100 mg protein /kcal and decreased when P/E ratio increased to 120 mg protein /kcal. Feed conversion ratio: Results of Table (4 and 5) indicated that, feed conversion ratio (FCR) was improved with increasing dietary protein level in red tilapia fry and fingerlings. Siddiqui et al., (1988), Cisse (1996), Abdel-Hakim et al., (2001) and Soltan et al., (2002). Al-Hafedh (1999) came to the same results that FCR of Nile tilapia was improved with increasing dietary protein level. El-Dahhar (1994) found that, FCR was significantly improved with increasing dietary protein level for both O. niloticus fry and fingerlings and the significant improvement in FCR was achieved when dietary protein level increased from 17 to 30% for fry and 17 to 22 for fingerlings. It could be seen that, increasing dietary energy content from 2400 to 2800 and 3200 Kcal ME/kg improved the FCR from 1.91 to 1.73 and 1.67, for fry (Table 4) and from 2.03 to 1.82 or 1.73 for fingerlings (Table 5) for the three dietary energy levels, 2400, 2800 and 3200 Kcal/kg diet, respectively. The diet contained 35% CP and 3200 kcal ME/kg (P/E ratio of 110.3 mg protein/kcal) showed the best improvement on FCR (1.25 and 1.54) and the diet contained 25% CP and 2400 kcal ME/kg diet (P/E ratio of 105.6 mg protein/kcal) showed the worst values for FCR (2.39 and 2.24) for red tilapia fry and fingerlings, respectively. These results mean that, the diet with P/E ratio of 110.3 mg protein/kcal considered as the most suitable diet tested in the present study for tilapia fish. Wafa (2002) found that, hybrid tilapia ( O. niloticus × O. aureus ) fed the diet with P/E ratio of 100 showed the best FCR (3.22) followed by those fed the diet contained 80 mg protein/kcal ME (3.27) while fish fed the diet contained 120 P/E ratio recorded the poorest (P<0.05) FCR values (3.44). Also, Soltan (2002) found that the best FCR was obtained with tilapia fish group fed an experimental diet contained 30% CP and 3000 Kcal ME/kg diet (P/E ratio of 100 mg protein/kcal). Protein efficiency ratio: As described in Tables (4 and 5), averages PER were significantly different and being 1.79, 1.70 and 1.98 for red tilapia fry and being 1.81, 1.67 and 1.83 for fingerlings fed the diets contained 25, 30 and 35% crude protein, respectively. Results of PER indicated that, increasing dietary protein significantly increased PER for red tilapia (Table 4) while PER had no clear trend in fingerlings. Abdelhamied et al., (1997) and Twibell and Brown (1998) found that, PER was unaffected by increasing dietary protein from 25 to 35% for O. niloticus . On the other hand, Siddiqui et al., (1988) found that, PER decreased with increasing diet protein level from 20 to 50% for Nile tilapia. Also, El-Ebiary (1994) found that, increasing dietary protein level up to 35% and feeding rate up to 4% decreased the values of nutrients (protein and energy) utilization in Nile tilapia and its hybrid. Increasing energy content of red tilapia fry and fingerlings from 2400 to 2800 or 3200 kcal/kg diet significantly (P<0.05) increased PER of red tilapia fry from 1.70 to 1.88 and 1.89 (Table 4) and from 1.61 to 1.81 and 1.91 for fingerlings (Table 5). PER values were improved for fry and fingerlings fed the diet contained 35% CP and 3200 kcal ME/kg diet (P/E ratio of 110.3). Wafa (2002) found that, hybrid tilapia ( O. niloticus × O. aureus ) fed diets contained 80 or 100 mg protein/kcal recorded the same (best) PER (1.14) whereas, those fed the diet contained 120 mg protein/kcal showed the poorest PER (1.04). Soltan et al., (2002) reported that, the best PER for Nile tilapia was recorded for fish group fed the diet contained 30% CP and 3000 Kcal ME/kg (P/E ratio of 100) and the lowest was recorded for the diet contained 25% CP and 3000 Kcal/kg (P/E ratio of 81.7). Proximate analysis of red tilapia fry and fingerlings: As shown in Table (6) moisture content of fry at the end of the first experiment ranged between 70.88 and 72.99% and the differences between these percentages were not significant. It is observed also that, increasing dietary protein level from 25 to 30 and 35% significantly decreased protein contents in whole fry bodies from 54.65 to 51.99 and 48.12, and significantly increased fat content from 30.24 to 30.84 and 35.53% (Table 6) and the same trend was also observed for red tilapia fingerlings where increasing dietary protein significantly increased protein and decreased fat content of red tilapia fingerlings (Table 7). In general, fish fed the high protein diet gained the highest crude lipid content in their bodies which can only be explained by an imbalance in the diet. Similar results were obtained by Abdel-Hakim et al., (2001) who found that, increasing dietary protein level from 25 to 30% decreased the percentages of protein from 55.58 to 52.24%. Also, Al-Hafedh (1999) found no significant influence of dietary protein level (25 to 45%) on body protein content of Nile tilapia but the lipid content decreased with increasing protein level and no clear trends in ash content were observed. As described in Table (6) it is observed that increasing dietary energy content from 2400 to 2800 and 3200 kcal ME/kg diet significantly decreased protein and ash but increased fact content of red tilapia fry fed the experimental diets for 8 weeks and the same trend were also obtained for tilapia fingerlings fed the same experimental diets for 10 weeks (Table, 7) and these results were supported by Buckely and Groves (1979), Shiau and Huang (1990) and Soltan et al., (2002). They found that, body lipid increased as dietary energy increased while the moisture, protein and ash contents decreased. Similar results were also reported with Mozambique tilapia (El-Dahhar and Lovell, 1995). Protein content in whole fish bodies ranged between 55.34 to 59.34% and fat ranged between 25.33 to 30.44% and ash ranged between 12.23-15.44% for red tilapia fry fed the different experimental diets that contained different P/E ratios (Table 6). The different experimental diets that contained different P/E ratios also had a significant effect on the percentages of protein, fat and ash content of red tilapia fingerlings (Table, 7). It could be concluded that diet containing 35% crude protein and 3200 kcal ME/kg (P/E ratio of 110.3 mg protein/kcal) considered the most suitable diet for red tilapia fry and fingerlings reared in tanks. by Soltan, M. A. ; Eid, A.H. and Mohamed, K.A

The continuing demand for sustainable fishmeal and fish oil in aquaculture diets

Thu, 29 Jul 2010 22:27:00 +0000 — Thu, 29 Jul 2010 22:27:00 +0000

Throughout its history, aquaculture has made use of fishmeal and fish oil to feed not only carnivorous and omnivorous fish, but even herbivorous fish, particularly in their early stages when they need high protein levels. The reason why they have proved so popular in aquaculture is that both fish-meal and fish oil have unique nutritional properties. In the case of fishmeal these properties include a high protein level, ideal amino acid profile, high digestibility, lack of anti-nutritional factors, high palatability and wide availability. For fish oil they include high palatability, rich in essential omega 3 fatty acids and limited other users. This has meant that these two marine derived ingredients have been shown to consistently produce the most economically efficient diets, while also resulting in healthy animals which in turn yield healthy seafood products. However, as aquaculture expanded worldwide, it absorbed increasing volumes of both fishmeal and fish oil. This has led some people to the view that the future growth of aquaculture will be limited by a shortage of marine ingredients. Conversely, others have predicted that concern over the sustainability of fishmeal and fish oil, as well as rising prices, will result in decreased use of these ingredients in aquafeeds in the future. In this article I intend to examine the drivers behind the use of fishmeal and fish oil and try and answer the question as to what role they will play in future aquaculture diets. Production Production of fishmeal and fish oil has remained relatively stable over recent years (see Figure 1). Since 1980 annual fishmeal production has varied between five and seven million tonnes while that of fish oil has been between 1 and 1.5 million tonnes (see Figure 2). The clear drops in production in1998 and 2003 were caused by El Niños in South America which caused sharp reduc-tions in catch from fisheries in this region, notably that of anchovy, the world’s single largest fishery. The more recent decline since 2004 has been caused principally by two factors one being the move to more precautionary quota setting, particularly in Europe and South America and the second being the increasing use of species such as mackerel, herring and even anchovy for direct human consumption. The setting of more precautionary quotas may in time result in higher catches, but the trend towards increasing use of catches for human consumption is likely to persist. Therefore, the outlook for future availability of fishmeal and fish oil is that supplies are likely to remain tight, particularly since there are unlikely to be any new resources to be exploited. However, the one growth area in terms of supply is the use of fisheries by-products such as viscera, heads, frames and filleting waste for the production of fishmeal and fish oil. The higher prices now being achieved for protein meals and food/feed oils, plus increasingly stringent rules on the disposal of fisher-ies waste, has resulted in more and more of this raw material being made available for processing. IFFO now estimates that nearly 25% of the global production of fishmeal comes from fisheries waste – this includes meals coming from aquaculture by-products. Table 1 shows the production of fishmeal by country in 2007 with an indication as to the main raw material sources used.In conclusion, on the supply side pro-duction of fishmeal and fish oil is likely to remain relatively constant except for periodic downturns due to El Niños in the South Pacific. Consumption Since the early days in the 1950s, fishmeal has been developed and promoted as a high protein feed ingredient in complete diets for farmed animals, initially in the diets of poultry and pigs (see Figure 3). But by the 1980s intensive aquaculture, particularly salmon and trout farming, had started to grow strongly and require significant volumes of fishmeal. By 2008 nearly 60 percent of global supplies of fishmeal were being used in aquaculture while pig usage had decreased to 31 percent and poultry was under 10 percent. The very rapid drop in the fishmeal usage in poultry diets since the 1980s can be attributed to nutritionists finding alternative ingredients that gave equivalent performance at a lower cost. The reduction in its usage in pig diets was much slower because most of the fishmeal was in weaner diets for young pigs, and this has proved much harder to replace. Sprayed dried milk proteins are obviously good alternatives but their price is usually even higher than that of fishmeal. So this increasing market-share being taken by aquaculture has led some to speculate that growth in aquaculture will soon be constrained by the availability of fishmeal. However, this rather simplistic view treats aquaculture as a single market. This is a bit like regarding agriculture as a single market but, as we have already seen, there are different drivers in the case of poultry and pigs. Looking at a breakdown in the consumption of fishmeal by aquaculture (see Figure 4) we can see that the three main markets are salmonids (29 percent) crustaceans (28 percent) and marine fish (21 percent). These, of course, can be further broken down into different markets with varied drivers – particularly in the case of marine fish which covers a whole range of different species being farmed under many and diverse farming regimes. We can look at the largest grouping, salmonids, in a bit more detail; during the period 2000-2008 the global production of all farmed salmonids grew by around 47 percent (from 1.5 to 2.2 million tonnes) while the use of fishmeal in this market grew by only around seven per-cent (770,000 to 820,000 tonnes). The contrast in these figures is explained by the progressive replacement of fishmeal with other protein rich ingredients, following extensive research by the salmon feed companies. So while the industry has grown strongly and so has aquafeed production, the demand for fishmeal has only grown slightly. This demonstrates clearly that production growth is possible without increasing fishmeal usage, so long as there is nutritioal research to identify alternative ingredients and optimum inclusion levels. Much of the increased use of fishmeal in aquaculture has been in feed for species for which there has been less nutritional trial work conducted than for salmonids. However, with time, this work will be completed, allowing pro-duction to grow without demanding more fishmeal. This research will be driven by the cost benefit to be gained by replacing the fishmeal with cheaper alternatives whilst not impairing performance. The same argument holds true for fish oil During the 1950s and 1960s fish oil was used largely for the production of marga-rines by hydrogenation of the fatty acids. However, with the growth of salmon farming and the realisation that high oil content enabled feed con-version ratios to be reduced and protein levels decreased, greater quantities of fish oil were being used for feed. By 1990 around 16 percent of fish oil was used in aquaculture feeds while 60 percent was still used in margarine (see Figure 5). Two critical things then hap-pened, firstly more and more margarines were produced from vegetable oils, as this was seen as more healthy. Secondly salmon farming production really took off. The result was that the price of fish oil fell with the loss of the margarine market. This made it doubly attractive to the salmon feed industry as it was both cheap and ideal for inclusion in feeds. The result was that by 2000 around 75-80 percent of the global production of fish oil was being used in aquaculture while less than five percent was going for direct human consumption, with the remainder being used in industrial processes such as paints and tanning. Again since 2000, despite the strong growth in the salmon industry, the total amount of fish oil being used in salmon feed has remained at much the same level of around 550,000 tonnes per annum. The exact amount at any one point in time has been determined by the price of fish oil as compared to alternative oils. In recent years there has also been a strong growth in the direct human consumption of fish oil in capsules and functional foods, however despite this strong growth it still only represents 10-12 percent of the market. Price The main alternative to fishmeal in aquaculture diets is soymeal and the main alternative to fish oil is rapeseed oil. It is therefore of interest to look at the long-term trends in the price of these four raw materials (see Figure 6). For most of the period 1999 to 2006 the price of fishmeal remained in the US$400-600/tonne area but then, mostly as a result of strong demand from China, the price suddenly increased to around US$1200 causing shockwaves through the market. This can be clearly seen in the ratio of fish-meal price to soymeal price. This rose to unprecedented levels, greater than 6:1, following years of being around the historic level 3:1. However, what then followed was a classic market correction as inclusion levels were adjusted downwards in almost every feed contain-ing fishmeal. The result was a sharp drop in price at the same time as the price for soymeal was increasing. Consequently, since the begin-ning of 2008 the price of fishmeal has been rela-tively low when compared to the price of soymeal, indicating that once again fish-meal represents good value for money and supply is, if anything, above required demand. There is certainly no evidence here that there is insufficient supply to meet the demand of a growing aquaculture industry. A similar picture can be seen when we look at the price of fish oil, except that in late 2002 the price of fish oil rose sharply at the onset of an El Niño (at a time when the price of other oils was dropping), but as can be seen in the price comparison with rapeseed oil, the ratio soon fell back to the historic figure of around 1:1 (see Figure 7). In 2008 the price of all oils rose globally and this was particularly true of fish oil. This led many feed formulators to replace fish oil with vegetable oils. However, in late 2008 it became apparent that the disease problems in the Chilean salmon industry were more serious than many had thought and production volumes have declined sharply. Given the importance of the salmon feed market to fish oil, the combined effect of substitution and reduced demand resulted in the price decreasing rapidly. Soon the ratio of fish oil to rape oil hit a low of 0.5:1. However, once again market forces resulted in a rapid move back to fish oil again, particularly in salmon diets. As was the case with fishmeal, there is no evidence that the aquaculture industry has been restrained by the availability of fish oil. Since fish have a relatively low nutritional requirement for the omega-3 fatty acids EPA and DHA which are found in fish oil, it is clear that even in salmon diets most of the energy can be supplied in the form of vegetable oil. So market forces will continue to determine the demand for fish oil. The biggest concern with this approach is, however, that the farmed products produced using dietary vegetable oil, rather than fish oil, are going to be much lower in the healthy very long chain PUFAs, EPA and DHA. Given the growing body of scientific evidence as to the importance of higher intake of these fatty acids and the consumers’ growing realisation that seafood is one of the best sources of EPA and DHA, aqua-culture could endanger the healthy image of its products with the indiscriminate and excessive substitution of marine oils with vegetable oils. Sustainability One of the growing questions that has to be answered by any raw material before inclusion into aquaculture feed is: does it derive from a sustainable source? This question is equally valid when asked of soymeal and palm oil as it is of fishmeal and fish oil. The immediate question is what does sustainable mean, particularly in the context of fisheries and fisheries management. The most widely accepted international agreement on fish-eries is the Code of Conduct for Responsible Fisheries adopted by the FAO Conference at its Twenty-eighth Session in October 1995. This code of conduct explicitly states that it was developed to provide anecessary framework for national and international efforts to ensure sustainableexploitation of aquatic living resources in harmony with the environment. Most of the world’s fishmeal and fish oil comes from countries that are signatories to the code, but it is clear that some countries have made more effort to implement it than others. The outcome has been that there is a growing demand for fishmeal and fish oil that demonstrably comes from fisheries that have been managed using the key principles of the FAO Code. Another impor-tant issue has been well publicised reports of fishmeal being adulterated with other protein sources such as poultry offal meal, and even the use of protein mim-ics like melamine. These reports have mostly come from Asia where in some areas there have been fewer controls on quality. Given the impor-tance of these two issues, IFFO decided in 2008 to develop its own Global Responsible Supply Standard (GRSS). This Standard aims o reassure the value chain that the raw material used is from a fishery managed under the key principles of the FAO Code and that high standards of manufacturing were employed to ensure feed safety and purity. The intention of the GRSS is not to create another eco-label, but to be a business-to-business scheme to give reassurance to the value chain. The Standard has been developed with the help of a range of different stakeholders including retailers and environmental NGOs. To be compliant the fishery will have to be assessed by a third party and the factory will have to undergo a physical audit to ensure the agreed standards are met. The development of the GRSS is nearing completion and it is hoped that product will be on the market before the end 2009. This will then give retailers, processors, farmers and feed producers the means to demonstrate that the marine raw materi-als they use in the production of their farmed seafood are responsibly sourced and produced. Conclusion Fishmeal and fish oil have been and will continue to be vital ingredients in many types of aquaculture diets. Although sup-plies are likely to remain tight the various sectors of aquaculture will be able to grow by complementing the marine ingredients with ingredients from other sources. This will result in lower inclusion levels of both fishmeal and fish oil. Increasingly they will become strategic ingredients used at critical times in the life cycle. The issue of responsible raw material sourcing and production of fishmeal and fish oil will become progressively more important and will be managed through independently-audited certification schemes such as IFFO’s Global Responsible Supply Scheme. by Andrew Jackson - International Fishmeal and Oil Organisation

An attempt to improve the reproductive efficiency of Nile tilapia brood stock fish

Thu, 29 Jul 2010 22:22:00 +0000 — Thu, 29 Jul 2010 22:22:00 +0000

Tilapia aquaculture is and will continue to be an important fish, particularly for the lesser-developed countries in the tropics. Nile tilapia ( Oreochromis niloticus) are considered as the most common and popular fish in Egypt. Egypt, a country where, arguably, the farming of tilapia has its roots, where tilapia culture is believed to have originated some 4000 years ago. Tilapia consist 36% of the Egyptian production from fish culture and occupy the 10th order concerning the world production from aquaculture. Hence, Egypt produces 20% of the world tilapia capture and 12% of the world farmed tilapia. The culture of O. niloticus in Egypt has recently developed into a major industry. This industry, however, is still growing in a remarkable way with apparent intend towards intensification that pressurizing the need of enormous number of seeds. Many limitations associated tilapia fry production under the prevailing Egyptian conditions were described by El-Gamal. Also, brood stock husbandry and spawning techniques are constantly upgraded as Egyptian hatcheries require a high number of good quality eggs to satisfy the needs for aquaculture, so rigorous management of large numbers of brood stock are necessary for mass production of eggs and fry due to the complex reproductive biology and asynchronously spawning with relatively small number of eggs produced per spawning. Accordingly, the development of more elaborated forms of brood stock management is crucial to improve fry yield and system efficiency. Today, it is widely accepted that effective seed production demands a thorough understanding of the special husbandry and particular nutritional requirements of brood stock fish which significantly affect fecundity, survival, egg size and egg and larval quality. The objective of the present research was to study the possibility of improving reproductive performance of Nile tilapia fish using some feed additives. MATERIALS AND METHODS The present study was carried out during Nile tilapia hatching season of 2008 (June and July) in two phases, the first was to study the effects of three commercial feed additives on females (Therigon®, Nuvisol Hatch P® and Gibberllic acid) and fourth one (L - carnitine) on males brood stock, concerning their gonads characteristics and some reproductive traits. The second phase was to select treatments of both 0.5 g Therigon® and 2 g Nuvisol Hatch P® / Kg diet (for females ) and 700 mg L - carnitine / Kg diet (for males ) to apply in a mating trial to be evaluated via hatchability. Experimental management of the 1st phase: A field study was conducted in a private earthen pond fish farm located at Alabhar belonging to Alhamol, Kafr Alshiekh governorate. Fourteen Habas (each 3 m width × 6 m length × 0.5 m water depth and 1 m total depth) were constructed in a two Feddans earthen pond. The first ten Habas were stocked with females brood stock of one year (yearlings) Nile tilapia fish (average body weight of 150 g) from the same farm. The other four Habas were stocked with males brood stock of (the same age as the females, but of an average body weight of 200 g) Nile tilapia fish from the same farm also. Each Haba was stocked with twenty fish. This study was a feeding trial to test the effects of some commercial dietary supplements on Nile tilapia ( O. niloticus ) propagation. The experimental feeding began on the 20th June till the 8th of July, where the feed was offered to fish twice daily, at a daily feeding rate of 3% of the fish biomass in each Haba. The feed additives were purchased from the local market and added directly to a mash diet, which was purchased also from the local market (contained 90.31% dry matter, 80.88 % organic matter, 23.81% crude protein, 5.47% ether extract, and 9.43% ash) after the proximate analysis according to AOAC [8] and moistened to be pelleted via a hand mincer. The feeding continued for males and females before mating. Water of fish rearing in each individual Haba was tested daily for some water quality parameters including water temperature, pH value, and dissolved oxygen concentration. Dietary treatments during the 1st phase: Fish were fed on a basal ration (BR) with or without (control) the tested feed additives (as illustrated in the following Table 1) which were: 1- Therigon® powder for veterinary use, manufactured by Adwia Co., S. A. E. 10th of Ramadan city, Egypt. Each 1 g contains Alpha - Amino - p - hydroxyhydrocynnamic acid, 1000 g package as GnRH stimulant (Batch No. 0601116). 2- Nuvisol Hatch P®, imported by Khirat Alnile Co., 27 Alferdos Buildings, Flat 43, Nasr city, Egypt from Newtrix Co., Belgium, in 500 g package. Each 1 Kg contains the following vitamins (in mg): B1 4000, B2 5000, B3 4000, B6 2000, B9 1000, B12 20, PP 10000, Biotin 50, and L - carnitine 30000. 3- Gibberllic acid (C19 H22 O6), type analysis, Art. 3930, M. W. 346.38, M. P. 225 °C, GA3 content 90 %, 1 g package, Batch No. 43124, imported from Lobal Chemie, Pvt. LTD, 2042 Bombay, India. 4- L - carnitine powder from Mebaco, Egypt. Table1: Explanation of the experimental diets during the 1st phase Diets Haba's No. & sex Basal ration (control femeles) 1, ♀ Basal ration + 0.5 g Therigon®/ kg diet , ♀2 Basal ration + 1.0 g Therigon®/ kg diet 3, ♀ Basal ration + 2.0 g Therigon®/ kg diet , ♀ 4 Basal ration + 1 g Nuvisol Hatch P® / Kg diet , ♀5 Basal ration + 2 g Nuvisol Hatch P® / Kg diet , ♀6 Basal ration + 3 g Nuvisol Hatch P® / Kg diet , ♀ 7 Basal ration + 20 mg Gibberllic acid / Kg diet ♀ 8, Basal ration + 40 mg Gibberllic acid / Kg diet 9, ♀ Basal ration + 60 mg Gibberllic acid / Kg diet ,♀10 Basal ration (control males) 11, ♂ Basal ration + 700 mg L - carnitine / Kg diet 12, ♂ Basal ration + 900 mg L - carnitine / Kg diet 13, ♂ Basal ration + 1100 mg L - carnitine / Kg diet , ♂14 Criteria measured at the end of the 1st phase: After the 19 days feeding trial of the separate sexes of brood stock, three fish from each experimental Haba were catched to collect blood, seeds (eggs), and milt for different measurements and determinations. Tri sodium citrate was used as an anticoagulant for blood collection. Blood determinations for follicle stimulating hormone (FSH), luteinizing hormone (LH) and progesterone hormone were done using commercial colorimetric kits (Diamond, Diagnostic, Egypt), and milt analyses (count, motility, forward, sluggish and dead percents) were done too. Experimental management during the 2nd phase: Six Habas (similar to those used in phase one, in the same earthen pond, at the same private farm) were used in the second phase (beginning from the 9th of July) of this study. The Habas were stocked with 9 females and 3 males each (sex ratio 3 ♀: 1 ♂) to test the best treatments from phase one as following in Table 2: Table 2: Explanation of the experimental reproductive trait during the 2nd phase: ♀ × ♂from the 1st phase Haba's No. ♀fed on Basal ration (BR) × ♂ fed on BR 1 ♀ fed on BR × ♂ fed on BR + 700 mg L - carnitine / Kg diet 2 ♀ fed on BR + 0.5 g Therigon®/ kg diet × ♂ fed on BR 3 ♀ fed on BR + 0.5 g Therigon®/ kg diet × ♂ fed on BR + 700 mg L - carnitine / Kg diet 4 ♀ fed on BR +2 g Nuvisol Hatch P® / Kg diet × ♂ fed on BR 5 ♀ fed on BR +2 g Nuvisol Hatch P® / Kg diet × ♂ fed on BR + 700 mg L - carnitine / Kg diet 6 The level 0.5 g Therigon® / Kg diet was chosen for its high value of FSH (Table 7), 2 g Nuvisol Hatch P® / Kg diet was chosen for its high value of progesterone (Table 7). On the 22nd July, the fry were collected and counted. Throughout this phase also, water quality parameters were measured daily as in phase one, at 9 - 11 am. Statistical analysis: Data collected were statistically analyzed using SAS [9], when ANOVA-test was significant (P ≤ 0.05), least significant difference was calculated [10] to differentiate between means. RESULTS As shown from Table 3, there were no significant differences among all Habas concerning the tested water quality parameters. Therefore, the data were presented as overall means ± standard errors (SE). The tested parameters showed very suitable water conditions for rearing tilapia. Table 3 Mean values of some quality parameters of the Habas' waters used for rearing Nile tilapia brood stock in an earthen pond throughout the experimental course. Dissolved Oxygen, mg / l The pH values Temperature, °C Item 5.70 ± 0.11 7.50 ± 0.06 29.4 ± 0.19 Mean ± SE Data of the studied females' reproductive traits are illustrated in Table 4. Except GSI, the other tested parameters showed significant (P ≤ 0.05) differences among treatments. The significantly heavier body weight (288.9 ± 23.8 g) after the 19 day-study was realized by the fish in the 8th Haba (20 mg gibberllic acid / Kg diet) followed by Haba No. 6 (2 g Nuvisol Hatch P® / Kg diet) without significant difference between both Habas (6 & 8). The best (P ≤ 0.05) ovaries weight (11.5 ± 0.07 g) was recorded in fish of the 4th Haba (2 g Therigon® / Kg diet); yet, there were no significant differences among all treatments and the control. Egg number per fish was the highest (935.5 ± 120.2 and 926.0 ± 12.7) significantly (P ≤ 0.05) by the 5th and 3rd Habas' fish (treated with 1 g Nuvisol Hatch P® / Kg diet and 1 g Therigon® / kg diet), respectively. Yet, the egg number / Kg fish weight (fecundity) of these fish groups in Habas No. 5 and 3 did not differ significantly (P ≥ 0.05) with the control, which was better (P ≤ 0.05) than all the other treatments. Moreover, the lowest (P ≤ 0.05) egg diameter was reflected by the fish groups of Habas No. 6 and 5, being 0.96 ± 0.06 and 1.25 ± 0.00 mm. Otherwise, all other treatments were significantly similar to the control. Table 4: Females' sexual parameters of brood stock Nile tilapia as affected by the dietary supplementations for 19 days feeding trial in Habas in an earthen pond (means* ± SE). GSI*** Egg diameter, mm Egg No./Kg BW** Egg number / fish Ovaries weight, g Fish weight, g Haba No. 4.71a ± 0.31 1.55a ± 0.12 4341a ± 224.8 769.3b ± 34.4 8.45ab ± 1.35 178.1b ± 17.1 1 4.26a ± 0.76 1.55a ± 0.12 3267bcd ± 491.1 689.0bc ± 99.0 9.00ab ± 0.90 211.7b ± 5.70 2 4.03a ± 0.38 1.55a ± 0.12 4114ab ± 360.1 926.0a ± 9.00 9.25ab ± 1.75 227.0b ± 22.1 3 5.14a ± 0.70 1.67a ± 0.00 3037cde ± 286.8 698.3bc ± 14.3 11.5a ± 0.05 227.0b ± 32.1 4 4.02a ± 0.59 1.25b ± 0.00 4171ab ± 445.0 935.5a ± 85.2 9.00ab ± 1.20 224.5b ± 3.50 5 4.42a ± 0.38 0.96c ± 0.04 2161ef ± 138.2 519.0de ± 74.2 10.7ab ± 1.75 239.0ab ± 19.1 6 3.49a ± 1.44 1.67a ± 0.00 2423def ± 163.7 537.5d ± 12.6 7.5ab ± 2.50 223.2b ± 20.3 7 3.28a ± 0.83 1.67a ± 0.00 2191ef ± 176.8 630.0bcd ± 14.1 7.90ab ± 0.40 288.9a ± 16.9 8 3.30a ± 1.22 1.67a ± 0.00 3376bc ± 93.9 602.0cd ± 0.00 5.95b ± 2.35 178.5b ± 4.96 9 4.41a ± 0.40 1.67a ± 0.00 1754f ± 68.5 391.5e ± 12.6 10.1ab ± 0.05 223.9b ± 15.9 10 * Means with the same letter within the same column don't differ significantly (P ≥ 0.05). **: BW=body weight. ***: GSI = gonado - somatic index = gonads weight (g) × 100 / fish weight (g). Tables 5 and 6 present data of males reproductive traits tested including testes weight and GSI as well as milt quality parameters. Although there were no significant differences among treatments and the control; yet, the control was more pronounced in fish weight, testes weight, GSI, and sperms count than the treatments. But the motility and dead percentages were better in fish group of Haba No. 12 (700 mg L - carnitine / Kg diet) followed by Haba No. 13 (900 mg L - carnitine / Kg diet) concerning motility, forward, sluggish and dead percentages. Table 5: Males' gonado - somatic index of brood stock Nile tilapia as affected by the dietary supplementations for 19 days feeding trial in Habas in an earthen pond (means* ± SE). GSI** Testes weight, g Fish weight, g Haba No. 1.425 ± 0.01 4.050 ± 0.05 283.05 ± 0.85 11 0.965 ± 0.32 2.350 ± 0.95 236.10 ± 22.3 12 1.035 ± 0.12 2.550 ±0.05 250.00 ± 33.0 13 0.915 ± 0.24 2.450 ± 0.75 263.55 ± 14.0 14 *:Means don't differ significantly (P ≥ 0.05). **: GSI = gonado - somatic index = gonads weight (g) × 100 / fish weight (g). Table 6: Data of some quality parameters of milt (using Hämocytometer slide) collected from the tested males brood stock Nile tilapia as affected by the dietary supplementations for 19 days feeding trial in Habas in an earthen pond. Dead, % Sluggish, % Forward, % Motility (viability), % Count, × 106 Haba No. 35 45 20 55 660 11 25 40 35 75 450 12 30 40 50 60 350 13 30 45 35 45 390 14 Data of serum sexual hormones of the experimental fish are presented in Table 7. Females fish of the 3rd and 5th Habas reflected lower concentrations of (FSH) but higher concentrations of either (LH) or progesterone hormone, comparing with the other Habas' fish. This is in good accordance with the fecundity which was given in Table 4. Also, male fish of the 12th and 13th Habas (Table 7) had sera with higher levels of FSH, LH, and testosterone comparing with the other treatments. This also confirms the previous results of the milt analysis for its quality parameters (Table 6). Table 7: Data of blood sera analysis for sexual hormones of the tested Nile tilapia brood stock fish as affected by the dietary treatments for 19 days during rearing in Habas stocked in an earthen pond. Progesterone (♀) / testosterone (♂), ng / ml LH, u / ml FSH, u / ml Haba's No. & sex 0.014 19 32 1, ♀ 0.110 18 91 2, ♀ 0.080 19 13 3, ♀ 0.060 61 83 4, ♀ 0.130 52 14 5, ♀ 0.140 48 63 6, ♀ 0.009 27 16 7, ♀ 0.006 84 72 8, ♀ 0.003 26 14 9, ♀ 0.017 28 84 10, ♀ 2.780 59 48 11, ♂ 4.310 76 89 12, ♂ 5.140 89 78 13, ♂ 1.010 38 24 14, ♂ The following Table 8 shows that all pretreatments for males and females brood stocks of Nile tilapia positively affected propagation (2nd phase of the experiment, mating), i. e total count of the offspring produced. Yet, the 4th Haba (in which the females were pretreated with 0.5 g Therigon® / Kg diet and the males were pretreated with 700 mg L - carnitine / Kg diet, for 19 days before mating or fertilization) gave the highest total count of the offspring comparing with the other Habas. But, the 3rd, 5th, and 4th Habas were the best economically, since they were responsible for 43.5, 31.7, and 25.3 % superiority than the control (1st Haba). Table 8: Total count of the offspring produced at the end of phase two as affected by the dietary pretreatment of the brood stock in phase one and economic efficiency. Economic efficiency Consumed feed price, LE Fry price, LE/1000 Fry count Haba's No. Relative Absolute* 100.0 48.77 2.44 119.0 3400 1 78.74 38.40 3.19 122.5 3500 2 143.5 70.00 2.00 140.0 4000 3 125.3 61.09 2.75 168.0 4800 4 131.7 64.22 2.18 140.0 4000 5 100.1 48.80 2.94 143.5 4100 6 * Economic efficiency = Income from buying the produced fry in LE / feed costs of the brood stock during the pretreatment in LE, where the local price of 1000 fry was 35 LE and for 1 Kg diet without additives was 2.2 LE. DISCUSSION The quality of fish rearing water did not influence by the experimental treatments, and was suitable for rearing Nile tilapia brood stock according to Abdelhamid [11]. Reproductive performance of fish is influenced by many factors, e.g. feeding regime including dietary protein [12-14] and vitamin [15, 16] levels, feeding rate [17], and hatchery management [18], as well as endocrine regulation [19-24]. Other environmental conditions may also affect, including photoperiod and water temperature [25-27] as well as water depth [28] The fish farming industry has been more focused on the quality of eggs or larvae rather than that of sperm, even though the quality of both gametes may affect fertilization success and larval survival. Sperm quality in farmed fish may be affected by different components of brood stock husbandry, during collection and storage of sperm prior to fertilization or the fertilization procedure. Motility is most commonly used since high motility is a prerequisite for fertilization and correlates strongly with fertilization success [29]. Gibberellins (GAs) are involved in a wide range of plant developmental processes. Of all the plant hormones the GAs represent perhaps the most diverse group, with currently 126 different structures known [30]. Gibberellins are tetracyclic diterpenes that are found in plants and fungi. A few of the identified to date are known to be active hormones that are involved in seed germination, seedling emergence, stem elongation, fertility, and flower and fruit development. The gibberellin receptor has not yet been conclusively identified. GAs act in stem growth via an enhancement of both cell division and cell elongation. Gibberellins get their unusual name from the fungus Gibberella fujikuroi , from which they were first isolated [31]. GA3 is naturally widespread than the other gibberellins which have sexual influences [32]. GA3 has a pesticide effect [33], and also carcinogenic effect on rectal protozoon [34] and Egyptian toads' liver [35]. But, [36] clearly demonstrated that it was essentially nontoxic by various routs of applications for different animal species. Yet, it promotes growth of rats, poultry, pigs, and calves [37, 38] as well as it improves laying hens' production, concerning egg production, egg mass and hatchability [39, 40]. Gibberellins have an estrogenic effect on animals [41]. It increased blood protein significantly, but affected different organs weight and their histology in chickens [42]. In fish, GA3 at low levels improved Nile tilapia growth and gonado-somatic index [43], since it is a nitrogenous compound [37] with estrogenic effect; where it increased the percent of egg production, hatchability and ovary and oviduct relative weight significantly [44]. So using natural GA3 instead of the synthetic estrogen is safer and environmentally friend therefore should be considered. L-carnitine is a naturally occurring amino acid derivative (dipeptide amino acid), synthesized from methionine and lysine. L-carmitin, a betaine derivative of β - hydroxybutyrate, could be biosynthesized in plant and animal cells via lysine, methionine, and some vitamins like B6, C, nicotinic acid and folate [45]. It is an essential cofactor of fatty acid metabolism (it provides energy by transporting long and medium chain fatty acids to mitochondria to act as fuel). Deficiency in carnitine is associated with male infertility. Since L-carnitine provides an energetic substrate for the spermatozoa in the epidydimis, contributes directly to sperm motility and may be involved in the successful maturation of the sperm. Carnitine lowers triglycerides and raises the high density lipoprotein levels. L-isomer of carnitine is more effective than DL - isomer [46]. Cellular parameters of the seminogram have been previously shown to correlate with L-carnitine concentration in the seminal fluid. Carnitine is involved in maintaining an active oxidative phosphorylation (OXPHOS). Therefore, it was strongly suggested that relationship between carnitine secretions, seminal quality and OXPHOS activities could be because of a parallel response to the same regulatory event [47, 48]. L-carnitine improved semen quality and histological characteristics of the testes [49]. Generally, a low level of L-carnitine enrichment provides several protective effects in fish reared under intensive pond-culture conditions [50-52]. Pituitary homogenate induced artificially maturing and increased both serum testosterone and estradiol [53]. Gonadotropin-releasing hormones (GnRHs) bind to the specific receptor on the gonadotrophs to activate the synthesis and release of gonadotropins (follicle stimulating hormone or FSH and luteinizing hormone or LH), which in turn control gonadal maturation, gametogenesis and gamete release [54, 55]. Not only do teleosts exhibit the highest variety of GnRH variants, but recent data and whole genome analyses indicate that they may also possess multiple GnRH receptor [56]. Synthetic analog of gonadotropin-releasing hormone was used for inducing ovulation and enhancing spermiation in brood fish [57]. Moreover, territorial males of African cichlid, Haplochromis burtoni , characterized by aggressive and reproductive activity, have significantly larger hypothalamic gonadotropin-releasing hormone (GnRH)-containing neurons and larger testes than nonterritorial males [58]. Dietary inclusion of 1 g Nuvisol Hatch P® / Kg diet and 1 g Therigon® / kg diet before mating realized good females reproduction performance. Also, dietary supplementation with 700 and 900 mg L-carnitine / Kg diet before mating gave better results of males' reproductive performance. But, because of the high feed cost due to the additives cost, 0.5 g Therigon® / kg diet as pretreatment for ♀ only (3rd Haba of the 2nd phase, mating), 2 g Nuvisol Hatch P® / Kg diet as pretreatment for ♀ only (5th Haba of the 2nd phase, mating), followed by 0.5 g Therigon® and 700 mg L-carnitine / Kg diet for ♀ and ♂, respectively (4th Haba of the 2nd phase, mating), respectively were the best economically. It could be recommended to use such commercial feed additives for improving reproductive performance of Nile tilapia brood stocks to offer enough seeds for fish farms .It is recommend also to make other trials on different other additives at economical levels. by A. M. Abdelhamid, A. I. Mehrim, Manal I. El-Barbary and M. A. El-Sharawy

Advances in fish health management: Vaccination of tilapia against streptococcus agalactiae

Thu, 29 Jul 2010 21:53:00 +0000 — Thu, 29 Jul 2010 21:53:00 +0000

World tilapia production has risen from 830,000 tonnes in 1990 to 1.6 million tonnes in 1999 and again to 2.5 million tonnes in 2005 (Josupeit, 2007). China is the world's largest producer of the tilapia, producing over one million tonnes in 2005, followed by Egypt (300,000 tonnes), Indonesia, Philippines (200,000 tonnes each) and Thailand (100,000 tonnes). By 2010, world tilapia production is expected to reach 3.5 million tonnes (Josupeit, 2007). Risks from diseases With increases in production come increases in risk of loss, particularly from diseases. The most significant disease causing losses in Tilapia culture is Streptococcosis . Streptococcal diseases of fish are becoming more common and when they do occur, significant losses can result. Some aquatic Streptococcal species may cause disease in humans in unusual circumstances. They do not usually affect healthy people. In addition to bacteria in the genus Streptococcus , there are several other closely related groups of bacteria that can cause similar disease, including Lactococcus, Enterococcus , and Vagococcus . Streptococcal infections in fish can cause high mortality rates up to 75% over a period of 3 to 7 days. Some outbreaks, however, are more chronic in nature and mortalities may extend over a period of several weeks, with only a few fish dying each day. Issues with Streptococcus A typical history suggesting that Streptococcus may be the cause of disease in a group of fish might include reports of abnormal swimming behaviour, often described as spiraling or spinning. Any time fish are observed behaving in an unusual manner, Streptococci should be considered as one of the possible causes; however, not all infected fish show abnormal behaviour. Affected fish may exhibit one or more of the following clinical signs, depending upon the species: erratic swimming (such as spiraling or spinning); loss of buoyancy control; lethargy; darkening; uni- or bilateral exophthalmia ('pop-eye' in one or both eyes); corneal opacity (whitish eyes); haemorrhages in or around the eye, the gill plate, base of the fins, vent/anus, over the heart or elsewhere on the body; ascites (dropsy/bloating) and ulcerations. In some cases, the fish may show no obvious signs before death. Of the signs listed above, haemorrhage, pop-eye, spinning, and rapidly progressing mortalities are among the most frequent observations. Most recently , Streptococcus agalactiae has become an important pathogen of tilapia in Asia and the Americas (Klesius et al., 2005). It is this pathogen that is responsible for much of the mortality in Thai tilapia culture in recent years (Tan et al., 2007). According to Maisak et al., (2008), of 60 isolates from infected tilapia from different areas of Thailand, 53 were S. agalactiae (88%) and only 7 (12%) were S. iniae. Some symptoms appear different from those in S. iniae infections, in particular the presence of blisters/abcesses on the jaw (Plate 1) and on the caudal area (Plate 2), whilst others are extremely similar eg, melanisation of the skin (Plate 3) and lesions of the skin (Plate 4). The taxonomy of the genus Streptococcus is complex and one of the results of this complexity is that a vaccine for S. iniae may not prove efficacious in the prevention of S. agalactiae infection. This has been clearly demonstrated by Evans et al., (2005); there appears to be very little or even no cross-protection between these species. Plate 1 Plate 2 Plate 3 Plate 4 Protection with injection vaccine In the present series of studies, an injectable vaccine was developed for the protection of tilapia against S. agalactiae infection in Thailand. Its safety and efficacy were established during this study and the commercial implications of having such a vaccine available for use are discussed. In a series of laboratory scale trials, the holding facility used is described in the diagram. Water from a supply canal is first pumped into a settlement tank. After settlement, the water is passed through a series of four sand filters to remove particulate material into a reservoir tank. Water is treated with chlorine to eradicate any potential pathogens from the culture water. Residual chlorine is removed using strong aeration. Water can then be used to supply the fish holding tanks. Water is also supplied to the challenge facility (Plate 5) which contains 12 net cages each. These net cages hold the replicates for each treatment. During the safety component of the experiment, water is allowed to flow through the system, but during the challenge phase, the water exchange was terminated and challenge water was passed to the sterilising tank. Prior to discharge of the water, a chlorine treatment was applied. This ensured there was no discharge of potential pathogens into the environment. Plate 5 Trial groups Three trial groups were used. These were control (untreated, positive control (injected with saline) and test (injected with vaccine). There were three replicates for each group holding 20 fish each. In the first phase of the trials, fish used in the experiment were of 2 strains; Thai Red and GIFT. The average body weight of the test fish was 20g. At termination of the experiment, red fish weighed 30g. Fish were fed daily at 1% of body weight and any moribunds or mortalities were removed for examination. In the second phase of the trials, fish used in the experiment were of the following strains; Genomar, Chitralada, Nam Sai, Thai Red and GIFT. The average body weight of the test fish was 20g. At termination of the experiment, fish weighed 30g. Fish were fed daily at 1% of body weight and any moribunds or mortalities were removed for examination. Vaccine The vaccine was a sterile, formalin killed adjuvanted vaccine containing two strains of S. agalactiae . Cell density of each strain within the vaccine was 5x 1011cells/ml. The two strains used were isolated from moribund tilapia sourced from 2 locations in Thailand; Nakhon Pathom and Prachinburi. The vaccine was stored at 2ºC under refrigeration until required. Safety . Safety studies were conducted over 56 days. Controls were not injected, but a positive control was present which was injected with 0.1ml of saline solution. The vaccine group was injected with 0.1ml of vaccine applied intra-peritoneally ( Plate 6 ) by a Kaycee multi-jector after anaesthetization of the fish. At the start of the experiment fish were first sedated using 0.1g/l Phenoxyethanol. Fish are then returned to their respective tanks. At the start of the challenge period, all surviving fish were injected with 0.2ml of pathogen in Tryptic Soy Broth. Plate 6 Efficacy After the 56 day safety study, surviving fish in all treatments were anaesthetised with phenoxyethanol, then fish were challenged by intra-peritoneal injection of live pathogen (0.2ml of 1.3x109 CFU/ml); this dose was considered optimal for this size of fish in previous research by Janenuj (pers.comm.) The pathogen was isolated from moribund tilapia from a farm in Prachinburi by the Aquatic Animal Health Research Institute in Kasetsart University, Bangkok, Thailand. Pathogen identification was carried out using API Strep from the same institute The pathogen challenge solution was prepared in Tryptic Soy Broth and contained 1.3 x 109 Colony Forming Units/ ml broth (prepared by IQA LAB, Bangkok, Thailand. Mortalities were monitored daily and recorded, and the appearance of symptoms was similarly recorded. The experiment was terminated 14 days after challenge. Actual survivals were calculated along with RPS values. The pathogen was re-isolated from moribund fish and compared with the challenge organism using API Strep at AAHRI, Kasetsart University, Thailand. Results In 6 separate trials this tri-valent S. iniae vaccine proved to be extremely safe 56 days post-injection, with survival values ranging from 97% to 100% ( Figures 1 and 2 ). Safety by intra-peritoneal injection route could therefore be considered safe (Clark et al., 2009a, 2009b and 2009c, in press) Again, in 6 separate challenge trials using a high dose of live pathogen isolated from infected tilapia Oreochromis niloticus ( 1x109 CFU/ml), survival rates of vaccinated fish, both single and double treated doses, were high. Typical safety data is shown in Figures 3 and 4 . RPS values were high in both experiments ( Figures 5 and 6 ) but from Figure 7 it is noteworthy that in fish of the same size injected with the same dose of the same pathogen, RPS values are variable. It was obvious from this data that different strains of tilapia displayed different susceptibility characteristics towards S. agalactiae infections. RPS Values for the vaccine ranged from a low of 41 to a high of 71 depending on the severity of the infection and the strain of tilapia. Vaccination of fish species in Asia will become the industry norm in the not too distant future. In many ways it will mirror events in the salmonid industry some 20 years ago. Whilst high value marine species such as grouper merit attention in terms of vaccine development (Clark and Chansue, 2009d), so too do more commonly cultured lower value species such as tilapia and catfish. Vaccination options In these preliminary studies carried out over a 2 year period, it can be seen that Streptococcosis in tilapia can be controlled via injection vaccination. RPS values can be high although they are masked to some degree by genetic variability. Re-infection studies using a re-isolate produced the same symptoms in infected fish ( Plate 7 ), and in a more recent trial in brood stock cages, the injection vaccinated fish exhibited survivals of 65% 6 months post-vaccination compared to 49% in the Control. This vaccine is still being improved but has already demonstrated significant cost-effectiveness to the farmer. While some may question labour costs, fish stress etc. as barriers to injection vaccine use, other forms of this vaccine are being tested. An immersion form is under test, although thus far it is not as successful as the injectable route. Immersion RPS values tend to produce RPS values 2x lower than injectable forms (Evans et al., 2004), and this in part could be due to low antibody response values in fish serum compared to those in mucous in injection vaccinated fish (Delamare-Deboutteville et al., 2006). Oral vaccination is considered the optimal vaccine delivery system but this too is problematic, particularly in terms of an optimal vaccine delivery system. As seen in one commercial trial with the tilapia, however, an oral vaccine form has produced a similar survival result after 6 months of cage culture to an injectable form, around 69% being achieved. This experiment is in need of repetition to ensure consistency, but there are strong grounds for optimism in this case. Plate 7 However, whilst vaccination may well be a prime tool in prevention of disease, it should not be viewed as a panacea for all illnesses. Numerous other tools are available to help prevent disease and disease vectors. Finally one should consider why pathogens such as Streptococcus agalactiae have become problematic wherever tilapia is cultured. There are large movements of fish between countries and it should not be surprising that pathogens move with the fish. If a large ecto-parasite such as the skin fluke Benedenia can be moved from country to country via marine fish fry, something as small as Streptococcus can be moved too. This is particularly true in the case of Streptococcus as it can "hide" within white blood cells of the fish (Zimmermann et al., 1975). In conclusion, vaccination has a good future as a tool in fish disease management and control in tilapia, and in either immersion, injectable or oral forms (or combinations thereof), will become a cornerstone for further development of the industry. Diagram 1 Caption: An illustration of the holding facility and water treatment system Figure 1. Mean % survival of Thai red tilapia ( O. nilotica ) to day 56 during a vaccine safety test (2007) Figure 2. Mean % survival of gift 7 tilapia (O . nilotica ) to day 56 during a vaccine safety test; (2007) Figure 3. Mean % survival of Thai red tilapia (O. nilotica ) to day 14 during a pathogen challenge (2007). Figure 4. Mean % survival of gift 7 tilapia (O . nilotica ) to day 14 during a pathogen challenge (2007). Figure 5. Mean RPS of Thai red tilapia (O . nilotica ) to day 14 during a pathogen challenge (2007). Figure 6. Mean RPS of gift 7 tilapia (O . nilotica ) to day 14 during a pathogen challenge; 2007. Figure 7. A summary of RPS values in tilapia (O. n ilotica ) corrected to control zero (2007/2008). by John S. Clark, Warren A. Turner, Angus MacNiven and Nantarika Chansue

Health & nutrition developments in the rearing of marine fish larvae

Thu, 29 Jul 2010 21:42:00 +0000 — Thu, 29 Jul 2010 21:42:00 +0000

Changes in ideas and product utilisation can yield significant survival and growth benefits for fish larvae. Combining nutritional and health strategies in rotifers and Artemia nauplii enhanced fish larvae growth in trials in Thailand. Thailand has long been regarded as the pioneer in the rearing of larval marine fish in the South East Asian region, particularly with the Sea Bass, Lates calcarifer. A rtificial propagation was successfully demonstrated by Wongsomnuk and Maneewongsa (1972). Since then, the industry has grown in Thailand with many hatcheries scattered along its eastern seaboard, particularly in Chachoengsao, Chonburi and Rayong. Current production estimates are around 800 million 1-inch fry/annum, many of which are exported to Malaysia, Taiwan and more recently Vietnam for further grow out in cages and ponds. In general, hatchery survivals are fairly low when compared to those of their European counterparts. Hatcheries tend to be smaller and are less capital intensive, with labour being mainly non-technical. General hatchery standards of hygiene tend to be lower and the level of technical expertise with respect to larval nutrition and health is sparse. However, despite rampant low overall survival rates, the industry is still a highly profitable one. Similar with so many other aquaculture sectors, small changes in routine and product utilization can yield significant differences in survival and growth benefits. Manipulation of health and nutrition The simplest area to manipulate and improve upon in terms of fish larval health and nutrition is in the field of bio-encapsulation using first rotifers then Artemia nauplii. Traditional enrichment methods involve concentration of the living food organism in a suspension of nutrients such as essential fatty acids(EFAs) and/or vitamins. As these two food organisms are filter feeders, they concentrate these nutrients within their tissues. After harvesting, they are fed to fish larvae which benefit from the enhanced nutrient profiles. There are, however, disadvantages clearly associated with this process. In the case or rotifers exposed to 12 hour enrichment at recommended dosages, high rotifer mortalities are commonplace. Reducing product density reduces product uptake by the target animal and only reduces rotifer mortality rate. This mortality is clearly seen as an accumulation of foam on the surface of the enrichment vessel. Furthermore, microscopic examination of the rotifers after 12 hour enrichment reveals the rotifers to be very sluggish in their rates of movement compared to non enriched rotifers and this may well result in further rotifer mortality in the fish larval rearing tanks. In the case of Artemia, the disadvantages may well be considered greater. With 12 hour enrichment times from Instar 2, the nauplius grows rapidly and may well become too large and fast moving for the intended predator fish. Again, there can be naupliar mortality in the enrichment vessel and a concomitant increase in the risk of disease transmission from dead or dying nauplii. With new enrichment techniques optimising filter feeding particle uptake, the time element can be reduced to a mere 1-2 hours. This leads to reduced labour inputs and easier scheduling of hatching and feeding operations. The nutritional quality of the prey organism is extremely high. In the case of rotifers there is no significant mortality in the enrichment vessel and the prey organism mobility remains high and in the case of nauplius, growth is limited, therefore the nauplius remains small. Fish larvae therefore find it much easier to capture smaller prey moving within their reactive perceptive fields (RPF) of vision. The risk of contamination is considerably reduced in such a practice. In summary the short time enrichment process is less work for the hatchery operator and increases nutritional quality for the fish larvae. Artemia enriched for 4 hours with new enrichment Rotifers enriched for 2 hours with new enrichment What should be used as enrichment materials? Traditionally this has been heavily skewed in favour of EFAs and vitamins. It is now possible to manipulate individual EFAs depending on the requirement of particular species or particular life stages of a species. As examples, some cultured organisms require EPA whilst others require higher levels of docosahexanenoic acid (DHA) or arachidonic acid (ARA); these can all be controlled and manipulated for the benefit of the target fish/shrimp. Short term enrichment can, however, be applied to a much wider spectrum of nutrients such as proteins and minerals. In terms of health, it has always been accepted that vaccination is out of the question, although recent work by Shoemaker and Klesius (2005) has shown that immune cells do exist and function in catfish fry as young as 10 days old. There are lessons to be learnt from studying immunity in higher vertebrates and extrapolating these to fish larvae. One such area is passive immunity. It is possible to prepare micro-encapsulated suspensions of natural immune products and concentrate them in rotifers and Artemia nauplii. Such products have been shown to significantly enhance larval fish survival in recent trials in Thailand, Malaysia and Vietnam. In the critical early days of larval development, these tools will be of great benefit in the future. Whole artemia gut showing health products in a micro-encapsulated form droplets in tissues and gut (Photo 1). Quality artificial feeds As in other situations, cheap does not often mean good. To rear the best quality fry one must use high quality feeds. What looks good to the operator e.g. in terms of colour, may not mean anything to the fish, which most likely sees in shades of grey. By the same token, what feed smells good to the operator may not smell good to the fish. Acceptability and palatability go hand in hand but may not necessarily be enhanced by the same compounds. A good illustration of this was observed in a large sea bass hatchery in Thailand. Fish had been weaned onto one commercial feed and then were offered Skretting Gemma feed as an alternative. There were no problems in acceptability or palatability. The same could not be said vice versa. Combining health and nutrition strategies Recently trials were run in Thailand rearing larval sea bass from first feeding on a combined health and nutrition strategy developed by the respective companies of the authors. The chosen hatchery was Talaythai hatchery in Ang Sila, Chonburi and involved four million hatch fry. Monitoring of the trial was done by representatives of both companies and by a team of aquatic veterinarians under the direction of Associate Professor Nantarika Chansue of the Aquatic Veterinary Medicine Department of Chulalongkorn University. Both rotifers and Artemia nauplii were enhanced nutritionally and boosted with a variety of natural health components in a micro-encapsulated form (Picture 1 & 2). This test was conducted against a conventional enrichment process. This process was implemented for a 20 day period following initiation of first feeding. Stocking densities were 40 larvae/litre and rotifer density was maintained initially at 20/ml. Feeding of enriched Artemia nauplii was initiated at Day 12 with an initial density of 1/ml. Daily feeding began with twice a day and by Day 14 it was increased to 7 times/day, beginning at 6am every 2 hours until 6 pm. Weaning using a conventional feed against a Skretting Gemma feed regime was initiated at Day 15 until the end of the test. Results showed a large difference in survival (80% against 30%) which is almost certainly due in the first instance to the natural enhancement of the larval immune system (Figure 1). No antibiotics or probiotics were used in the course of this trial. Therefore their influence could be negated. The influence of improved quality feed became increasingly evident as the trial progressed, and therefore feed built on the advantage provided by improved health . Animal size in the test group was considerably bigger (Figure 2). This was observed as early as Day 2 by Prof. Chansue and her team. The team noted the larvae were longer and deeper bodied (Figure 3), and that cranial diameter was larger in test fish; of most interest to the team were the obvious differences in dentition in the 2 groups of early larvae, with test larval dentition being more advanced than in controls (Figure 4). Figure 1. Mean body weight (mg) of sea bass larvae. Figure 2. Mean body depth (mm) of sea bass larvae. Figure 3. Mean body length (mm) of sea bass larvae. Species Expansion Since carrying out this initial trial, 2 repeat trials have been conducted at the same hatchery with similar results. In more recent trials with red snapper and tiger grouper in Malaysia the same system has been shown to produce excellent survival and growth in the test larvae. The same is true for larvae of the cobia and orange spotted grouper reared in trials in Vietnam. The overall intention is for the two companies to apply this joint health and nutrition package to hatcheries in every country throughout the region. A similar program for shrimp larvae is in the pipeline. Cranial diameter was larger in test fish fed natural health components in a micro-encapsulated form (left) as compared to control fish (right) fed via a conventional enrichment process (Photo 2) Advanced dentition in test group (below) as compared to control group (above) (Photo 3). by John S. Clark - Bayer HealthCare - Animal Health; and Arjen Roem - Skretting Asia