Using rainbow trout, Oncorhynchus mykiss (Walbaum), ol approximately 50 g, a 63 day feeding trial was undertaken to evaluate the efficacy of individual and multiple amino acid supplements in diets where soyabean meal was used as the principle protein source. Iso-nitrogenous diets (45% crude protein) were formulated where the control diet (F) contained tishmeal as the reference protein and a solvent extracted soyabean meal (S) replaced approximately 66% of this protein source. The soyabean containing diets were then supplemented with crystalline amino acids thus; methionine only, dual supplemented with two methionine and lysine levels and finally, a supplement comprising methionine, lysine, tryptophan, threonine, arginine and histidine. The results showed that soyabean meal (SBM) was inferior to the reference protein when SBM was used to replace 66% of the fishmeal and that no significant restoration in growth, feed efficiency and apparent net protein utilization was obtained by either methionine only or dual methionine and lysine supplementation. However, by comparison with the fish fed the unsupplemented. single and dual supplemented diets, multiple amino acid incorporation was associated with significantly improved percentage weight gain, specific growth rate and marginal improvements in apparent net protein utilization. However, performance was not equal to that of the fish fed the fishmeal based control diet. The results are discussed with respect to the level of each of the essential amino acids (EAA) as a proportion of the total EAAs (A/E index) of test diets by reference to the whole body tissue amino acid profile of rainbow trout.
Semi-purified diets containing J9% crude protein and 5% lipid were used to identify the qualitative requirement of African Ctitiish, Chmas gariepimts (Burcheli). for niacin and to characterize the pathologies associated with a deficiency of this vitamin. After 48 days of feeding. C. c]ariepiuus supplied with the unsupplemented diet had developed severe deficiency symptoms and were subsequently withdrawn from the growth study. Niacin deficiency was characterized by feed refusal, listlessness. weight loss, poor feed utilization and high mortality. The skin overlaying the lateral line of the deficient fish became haemorrhagic and this clinical sign was accompanied by severe anaemia. After 126 days of feeding, iish fed diets containing 17.0 mg niacin kg"' had also developed a dermopathy, but without anaemia or high mortality. The feeding of diets containing less than J 3.1 mg niacin kg" ^ resulted in suhoptimal feed efficiency and poor protein utilisation. Allometric analysis of proximate composition indicated that carcass moisture, protein and ash were influenced by fish size, and not by dietary niacin content. However, significantly more lipid per unit of weight gain was deposited in the carcasses of fish fed the unsupplemented diet than in fish fed diets containing 17.C)mgkg '. The indicators used in the present study could not be applied lo accurately determine a value for niacin requirement. However, until a more accurate assessment is performed, it is recommended that diets for C. cjariepimis contain not less than J3.1mg nicotinic acid kg" feed.•£ 1998 Blackwell Sfience Ltd 791
A 65‐day study was undertaken to evaluate the utilization of lysine‐supplemented wheat gluten meal as a protein source for rainbow trout, Oncorhynchus mykiss (Walbaum). The performance of the trout fed wheat gluten was compared to that of trout where protein was principally supplied using fish meal and full‐fat soyabean meal. Six isonitrogenous diets (approximately 45% crude protein) were formulated. Thus, the reference diet (FS) was based on fish meal and full‐fat soya bean meal while a further five diets were formulated with a mixture of wheat gluten and wheat middlings used to isonitrogenously replace approximately 75% and 57% of the full‐fat soya and fish meal respectively. Crystalline l‐lysine representing 0.00%, 0.29%, 0.58%, 0.87% and 1.16% of the complete diet was then added to the wheat‐gluten‐based diets. Optimal performance in terms of weight gain and apparent net protein utilization was achieved by the fish fed a wheat‐gluten‐based diet supplemented with lysine (0.58%) yielding a digestible lysine level of 1.9% of the complete feed. Within the range of supplements provided, lysine digestibility was high. However, at the highest levels of supplemental lysine the relationship between uptake and supplement level was not linear. Additionally, arginine digestibility was not affected by the level of lysine supplementation. However, amongst the wheat‐gluten‐based diets, optimal performance was associated with a lysine: arginine ratio of 1.1: 1.
Despite a lysine: arginine ratio of approximately 1.1: 1, the overall performance of the fish fed the fish‐meal‐soya‐based reference diet was poorer than expected. The results are discussed with respect to optimal patterns of gross and digestible amino acids, lysine‐arginine antagonism and the possible relationship between antinutritional factors and the poor performance of the fish fed the fish‐meal‐soya‐based reference diet.
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