Dietary glycine supplementation improves the growth performance of 110- to 240-g (phase II) hybrid striped bass (Morone saxatilis ♀× Morone chrysops ♂) fed soybean meal-based diets

Abstract

We recently reported that supplementing glycine to soybean meal (SBM)-based diets is necessary for optimum growth of 5- to 40-g (phase I) hybrid striped bass (HSB). The present study tested the hypothesis that supplementing glycine to SBM-based diets may enhance the growth of 110- to 240-g (phase II) HSB. HSB (the initial body weight of approximately 110 g) were fed an SBM (58%)-based diet supplemented with 0%, 1%, or 2% of glycine, with l-alanine serving as the isonitrogenous control. There were four tanks per dietary group, with four fish per tank. The fish were fed their respective diets to apparent satiation twice daily. The feed intake and body weight of fish were recorded daily and every 2 wk, respectively. At the end of the 56-d feeding trial, plasma and tissue samples were collected to determine amino acid concentrations and histological alterations, and tissues were used to measure the oxidation of l-glutamate, l-glutamine, l-aspartate, and glycine. Results showed that dietary supplementation with 1% and 2% glycine dose-dependently increased (P < 0.05) the concentration of glycine in the plasma of HSB by 48% and 99%, respectively. Compared with the 0%-glycine group, dietary supplementation with 1% glycine did not affect (P > 0.05) the feed intake of HSB but increased (P < 0.05) their final body weight, weight gain, and gain:feed ratio during the whole period by 13%, 29%, and 21%, respectively. Compared with the 1% glycine group, dietary supplementation with 2% glycine increased (P < 0.05) the feed intake, final body weight, and weight gain of HSB by 13%, 7%, and 14%, respectively. Compared with the 0%-glycine group, fish fed with the 1%-glycine and 2%-glycine diets had a greater (P < 0.05) villus height in the proximal intestine, when compared with the 0%-glycine group. Collectively, these results indicated that SBM-based diets did not provide sufficient glycine for phase II HSB (110 to 240 g) and that dietary glycine supplementation is essential for their optimum growth and intestinal structure.

Dietary glycine supplementation enhances syntheses of creatine and glutathione by tissues of hybrid striped bass (Morone saxatilis ♀ × Morone chrysops ♂) fed soybean meal-based diets

“…Notably, GSH is the most important non-enzymatic antioxidant in animals, whereas creatine helps to store ATP in the form of phosphocreatine for physiological processes such as muscle contractions, protein synthesis, and nutrient transport. Emerging evidence indicates that the endogenous synthesis of glycine may not meet the demand of farmed animals (e.g., HSB and growing pigs) under various nutritional and physiological conditions [ 13 , 14 , 27 ]. Although SBM has a balanced profile for most AAs, this feed ingredient contains much less glycine than fishmeal [ 19 ].…”

“…Likewise, dietary supplementation with GSH improves the growth, anti-oxidative capacity, disease resistance and gut morphology in juvenile Atlantic salmon [ 33 ], common carp [ 47 ], triploid rainbow trout [ 48 ], shrimp [ 49 ], and crabs [ 50 ]. Furthermore, dietary supplementation with 1% or 2% glycine prevented the occurrence of submucosal and lamina propria hemorrhages in the proximal intestine of Phase-I HSB (weighing 5 to 40 g) [ 13 ], while improving the intestinal structure of both Phase-I HSB and Phase-II HSB (weighing 110 to 240 g) [ 14 ]. Taken together, these findings indicate that the maximal growth, maximal antioxidative responses, and optimal health of fish (including HSB) require sufficient synthesis and availability of GSH.…”

“…The fish used for the present research were the cohorts of fish from our published studies involving two phases of feeding [Phase-I (approximately 5–40 g) and Phase-II (approximately 110–240 g)] supplemented with 0%, 1% and 2% glycine [ 13 , 14 ]. The composition of the diets has been reported previously [ 13 , 14 ].…”

“…The fish used for the present research were the cohorts of fish from our published studies involving two phases of feeding [Phase-I (approximately 5–40 g) and Phase-II (approximately 110–240 g)] supplemented with 0%, 1% and 2% glycine [ 13 , 14 ]. The composition of the diets has been reported previously [ 13 , 14 ]. The diets contained approximately 44% crude protein and 9.6% lipids on a DM basis that met the National Research Council (NRC)-recommended nutrient requirements for HSB [ 17 ].…”

“…A major challenge facing the global HSB industry is to reduce the cost of production through the use of plant-sourced protein feedstuffs as an alternative to fishmeal [ 11 ]. We recently reported that supplementing 1% or 2% glycine to soybean meal (SBM)-based diets is necessary for the optimum growth of 5- to 40-g (Phase-I) [ 13 ] and 110- to 240-g (Phase-II) [ 14 ] HSB. It is possible that the formation of GSH and creatine contributes to the beneficial role of glycine in fish growth [ 15 ], but currently little is known about these metabolic pathways or their nutritional regulation in aquatic animals.…”