Effect of dietary lysine and genetics on growth and indices of lysine catabolism in rainbow trout

Authors: GATRELL, STEPHANIE - West Virginia University; Silverstein, Jeffrey; Barrows, Frederic; GRIMMETT, JUANITA - West Virginia University; Cleveland, Beth; BLEMINGS, KENNETH - West Virginia University

Submitted to: Aquaculture Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2016
Publication Date: 5/1/2016
Citation: Gatrell, S.K., Silverstein, J., Barrows, F., Grimmett, J., Cleveland, B.M., Blemings, K.P. 2016. Effect of dietary lysine and genetics on growth and indices of lysine catabolism in rainbow trout. Aquaculture Nutrition. doi: 10.1111/anu.12459.

Interpretive Summary: Due to the recent worldwide expansion of aquaculture production, it is clear that the future supply of fishmeal, the primary protein source for carnivorous fish, will not meet its demand. To alleviate the need for fishmeal, plant products, such as soybeans, have been evaluated as potential replacements. Although soybean meal incorporation in the diet may decrease fishmeal dependence, numerous studies have found decreased growth of carnivorous fish consuming diets containing soybean meal. Two challenges that use a soybean meal-based diet presents are 1)the possibility of a lysine deficiency, which can be overcome by lysine supplementation, and 2)relatively high concentrations of dietary carbohydrates. Little is known about lysine metabolism in rainbow trout. Understanding lysine degradation may prove important in investigating any genetic variation in lysine metabolism, as well as optimizing lysine utilization, potentially decreasing the need for lysine supplementation. Since the replacement of fishmeal by soybean meal is desirable, the influence of genetics on growth and lysine metabolism needs to be re-evaluated for fish consuming a plant-based feed. Therefore, we aimed to identify any genetic effects on growth or lysine metabolism in rainbow trout fed a lysine-deficient diet. As expected, there was a diet effect on growth, thermal growth coefficient, and hepatic somatic index, but there was no effect of diet on indices of lysine metabolism. These data suggest that trout may not be able to respond to dietary lysine deficiencies by sparing endogenous lysine stores. However, there was a single family that exhibited a numerically more favorable feed efficiency and thermal growth coefficient when fed the lysine deficient diet, indicating that there is genetic variation in the response to a lysine deficient diet. Therefore, genetic influences on growth and efficiency should be taken into consideration when implementing nutritional programs with the incorporation of soybean meal as a protein source.

Technical Abstract: 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.