|Rawles, Steven - Steve|
Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2006
Publication Date: 9/29/2006
Citation: Subhadra, B., Lochmann, R., Rawles, S.D., Chen, R. 2006. Effect of fish-meal replacement with poultry by-product meal on the growth, tissue composition and hematological parameters of largemouth bass (micropterus salmoides) fed diets containing different lipids. Aquaculture. 260:221-231. Interpretive Summary: Interest in largemouth bass has grown beyond sport fishing to raising largemouth bass for seafood markets. There are no commercial feeds specifically for largemouth bass and the nutritional requirements of largemouth bass are poorly understood. This lack of information is a major roadblock to expanding production of this fish. We previously showed that growth of largemouth bass fed diets containing 10% fat from different sources (canola, chicken, or fish oil) or combination of sources (canola + chicken oil (1:1) or menhaden fish oil + chicken oil (1:1)) was nearly the same as growth of largemouth bass fed a commercial trout diet. In that trial, protein in the test diets was provided by a mix of fish meal and poultry processing by-product meal. In this second trial, we completely removed the fish meal from the test diets and replaced it with poultry by-product meal and 12% blood meal. The amount and sources of fats in the test diets remained the same as in our first trial (listed above). These test diets without fish meal were fed to groups of small largemouth bass (3.4g) for 12 weeks. A commercial trout diet was fed to another group of largemouth bass as a means of comparison. Nutrient levels in the trout diet were similar to nutrient levels in the test diets. Weight gain, feed consumption, feed conversion, and protein efficiency were lower in largemouth bass fed the test diets than in largemouth bass fed the trout diet. Among fish fed the test diets performance was not affected by the source of fat. Blood work indicated that all measurements of fish health were somewhat degraded in largemouth bass fed the test diets when compared to fish fed the trout diet. Also, some parts of the immune response needed for fighting disease were lower in largemouth bass fed the test diets when compared to fish fed the trout diet. The poor performance of the test diets without fish meal may be due to nutrients in the poultry by-product and in blood meal being less available to largemouth bass. Another possible reason is that the fish may not have liked the taste of blood meal in the diets, causing them to eat less and grow less than fish fed the trout diet. These results argue against the complete replacement of fish meal with a mix of poultry by-product meal and blood meal in diets for largemouth bass.
Technical Abstract: We previously showed that growth of largemouth bass (LMB) fed a diet containing different lipid (canola, chicken, or fish oil) or combination of lipids (canola + chicken oil (1:1) or menhaden fish oil + chicken oil (1:1)) was comparable to growth of LMB fed a commercial trout diet when protein in the test diets was provided by a combination of fish meal (FM) and poultry by-product meal (PBM). In this trial, practical diets contained poultry by-product meal (PBM) in place of fish meal, on a digestible-protein basis, and 12% blood meal (BM). The lipid sources were the same as in our previous trial (listed above). Lipid comprised 10% of each diet. Diets were fed to groups (n=4) of juvenile LMB (3.4g) for 12 wks. A commercial trout diet (Silver cup') was fed to another group of fish as a positive control. There were no differences in survival among treatments. Weight gain (23.8+1.8 g), survival (92+4 %), FI (44.3+4.1 g), FCR (2.1+0.1) and PER (1.3+0.04) of LMB did not differ among the replacement diets. However, weight gain (38.5+1.5), FI (53.9+1.1), and PER (1.6+0.1) of LMB fed the SC diet was higher and FCR (1.4+0.1) was lower than that of fish fed the test diets. There were no differences in hematocrit, hemoglobin, or mean corpuscular hemoglobin concentration among fish fed the test diets. Fish fed any of the diets containing some fish oil had higher alternative complement activity than fish fed the diet containing only chicken oil. There were no differences in serum lysozyme activity among fish fed the test diets. However, all hematological parameters were higher (better) in fish fed the trout diet. Regardless of lipid source, the complement and lysozyme activity were much lower (poorer) in LMB fed PBM-based diets than in our previous study when LMB were fed diets containing some FM. The amino acid composition of the PBM was similar to that of fish meal. However, the availability of some essential amino acids from PBM to LMB may have been limited. Poor diet palatability caused by the blood meal in the diet also may have reduced feed intake and fish performance. Therefore, complete replacement of FM with PBM in the diet may compromise the performance and health of juvenile LMB.