|Rawles, Steven - Steve|
Submitted to: Aquaculture Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/6/2009
Publication Date: 5/20/2010
Citation: Metts, L.S., Rawles, S.D., Brady, Y.J., Thompson, K.R., Gannam, A.L., Twibell, R., Webster, C.D. 2010. Amino acid availability from selected animal and plant derived feedstuffs for market size sunshine bass (Morone chrysops X M. saxatilis). Aquaculture Nutrition. p.1-8. Interpretive Summary: Accurate diet formulations are essential for the commercial production of hybrid striped bass. However, limited information is available regarding nutrient digestibility and amino acid availability of readily-used practical ingredients for different sizes of this fish. Two digestibility trials were conducted with market-size (1.5 lb or larger) hybrid striped bass to determine the nutrient digestibility and apparent amino acid availability in six common feedstuffs. In the first trial, three animal proteins were compared and included menhaden fish meal, pet-food grade poultry by-product meal, and feed-grade poultry by-product meal. In the second trial two plant-proteins, dehulled soybean meal and distiller’s dried grains with solubles, were compared with anchovy fish meal. These particular products were chosen in order to advance efforts to replace ocean derived fish meals (e.g., anchovy and menhaden) in aquatic animal feeds with promising plant and animal by-products. Distiller’s dried grains with solubles (DDGS), for example, is currently under intense scrutiny as a feed supplement for farm animals because of its increasing supply from the biofuel industry. Market size fish were chosen for this study because there are very few published reports of digestibility estimates in this particular size of hybrid striped bass. Our results show that the availabilities of essential amino acids in soybean meal and the two poultry by-products appear comparable to both of the tested fish meals in market size hybrid striped bass. This means that soybean meal and both grades of poultry by-product meal may potentially replace fish meal in hybrid striped bass diets with careful diet formulation. However, DDGS provided the lowest availabilities for several essential amino acids and should be used with caution in commercial diets. This information will assist feed mills and fish producers in formulating more efficient, economical diets for grow-out hybrid striped bass.
Technical Abstract: Accurate diet formulations are essential for the commercial production of hybrid striped bass. However, limited information is available regarding nutrient digestibility and amino acid availability of readily-used practical ingredients for different size classes of this taxon. Therefore, two trials were conducted with market-size (867 g) hybrid striped bass to determine the nutrient digestibility and apparent amino acid availability of six common feedstuffs. The animal protein feedstuffs tested in trial 1 were menhaden fish meal (MEN), pet-food grade poultry by-product meal (PBM-pet), and feed-grade poultry by-product meal (PBM-feed), while two plant-protein feedstuffs, dehulled soybean meal (SBM) and distiller’s dried grains with solubles (DDGS), were compared with anchovy fish meal (ANCH) in trial 2. Apparent digestibility coefficients of protein (ADC-CP) were significantly (P < 0.05) different among test ingredients in trial 1 as protein digestibility of MEN (86%) was significantly higher (P < 0.05) than that of PBM-feed (75%), but was not significantly different from that of PBM-pet (78%). Protein digestibilities in trial 2 were not significantly different among test ingredients and averaged 76%. % for ANCH, SBM, and DDGS. Some apparent amino acid availability coefficients differed among feedstuffs for both trial 1 and trial 2. MEN provided higher amino acid availabilities for alanine, aspartic acid, glutamic acid, lysine, valine and tryptophan (99%, 98%, 94%, 96%, 99% and 108%, respectively) when compared to PBM-feed (73%, 50%, 69%, 80%, 77% and 91%, respectively) and PBM-pet (79%, 66%, 81%, 81%, 78% and 99% respectively). Glycine, histidine, leucine and proline availabilities in MEN (95%, 96%, 100% and 98%, respectively) were significantly (P < 0.05) higher than those of PBM-feed (64%, 82%, 82% and 57%, respectively), but were not significantly different from PBM-pet (85%, 92%, 89% and 80%, respectively). For trial 2, apparent amino acid availabilities for cystine, isoleucine, lysine and tyrosine were significantly higher (P < 0.05) among treatments fed SBM (100%, 87%, 93% and 97%, respectively) and ANCH (37%, 95%, 92% and 84%, respectively) compared to treatments fed DDGS (-13%, 52%, 62% and 62%, respectively). Overall, amino acid availability in soybean meal and the two poultry by-products appear comparable to MEN and ANCH and corroborate their high value as potential replacements for fish meal in sunshine bass diets. However, DDGS provided the lowest availabilities for several amino acids and should be used with caution. This information will assist feed mills and fish producers in formulating more efficient, economical diets for grow-out hybrid striped bass.