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Effect of dietary lysine and genetics on growth and indices of lysine catabolism in rainbow trout (Oncorhynchus mykiss)

Gatrell, S. K., Barrows, F. T., Grimmett, J. G., Cleveland, B. M., Blemings, K. P., Silerstein,J.T.
Aquaculture nutrition 2017 v.23 no.5 pp. 917-925
Oncorhynchus mykiss, ammonia, condition factor, enzyme activity, essential amino acids, excretion, feed conversion, genetic traits, hepatosomatic index, lipid content, lysine, messenger RNA, metabolism, nitrogen, oxidation, oxygen consumption, soy protein, soybean meal, trout
The level of the essential amino acid lysine is of concern in trout feed. The objective of this study was to investigate the response of different families of fish to lysine-deficient (LD) versus lysine-adequate (LA) soy protein-containing diets. For each treatment combination, there were 5 replicates. As expected, feed efficiency (P<0.0001) and thermal growth coefficient (TGC, P<0.0001) were improved in fish fed the LA compared to the LD diet. Hepatosomatic index (HSI, P<0.01) and lipid content (P<0.01) were higher for fish consuming the LD compared to the LA diet. There was no effect (P>0.05) of diet on lysine a-ketoglutarate reductase (LKR) activity, LKR mRNA abundance or lysine oxidation. There was a family effect on feed efficiency (P<0.0001), TGC (P<0.0001), and condition factor (P<0.05) and a trend for differences in oxygen consumption (P<0.07) across families while consuming the LD diet; however, there was no effect on ammonia excretion, HSI, lipid content, efficiency of nitrogen or lysine retention or indices of lysine catabolism. One family in particular had more favorable feed efficiency and thermal growth coefficient when fed the LD diet, indicating that it may possess an enhanced genetic potential for performance when consuming lysine-deficient, soybean meal containing diets.