ARS | Publication request: Effects of carnosine supplementation to an all-plant protein diet for rainbow trout(Oncorhynchus mykiss)

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2011
Publication Date: January 17, 2012
Repository URL: http://riley.nal.usda.gov/nal_web/digi/submission.html
Citation: Snyder, G.S., Gaylord, T.G., Barrows, F., Overturf, K.E., Cain, K.D., Hill, R.A., Hardy, R.D. 2012. Effects of carnosine supplementation to an all-plant protein diet for rainbow trout(Oncorhynchus mykiss). Aquaculture. 338-341:72–81.

Interpretive Summary: It is predicted that global trout production will increase 51% and fish meal use for these feeds will have to decrease 35% by 2020. There have been numerous studies identifying the effects of replacing fish meal with plant meals, terrestrial animal meals or seafood processing waste on the growth performance of rainbow trout. These studies have demonstrated that alternatives to fish meal are either lacking in various nutrients or contain amino acid profiles not optimized for fish eating fish, or contain anti-nutritional factors that result in reduced growth when used to supply a large portion of dietary protein for aquafeed. Carnosine is a compound found in high levels in fish meal, but is not present in plant based ingredients. A 9 week study was conducted by feeding plant based diets supplemented with carnosine and other specific amino acids. Some metabolic changes were noted in these fish, but growth of fish fed plant based diets was not increased by supplementing with carnosine.

Technical Abstract: Fish meal may contain “unknown growth factors” that have yet to be identified for their physiological role. Carnosine is a histidine-ß-alanine dipeptide found in muscle and nervous system tissue which has been demonstrated to have biological activity, but its physiological role is not well defined. A 9-week feeding study was conducted comparing diet FM, a 100% fish meal protein control diet, to fish fed three plant protein diets: diet SPI, 100% of the fish meal replaced with soy protein isolate; diet SPI+AA, diet SPI supplemented with methionine, lysine, threonine and glycine to diet FMlevels; and diet CSN, diet SPI+AA supplemented with carnosine. Feeding diet SPI resulted in significant differences in feed conversion ratios (FCR), percent gain and protein retention efficiencies relative to fish fed diet FM. Feeding diets SPI+AA and CSN resulted in FCRs, percent gains and protein retention efficiencies that were not significantly different from fish fed diet FM. Fish fed diets SPI, SPI+AA and CSN resulted in reduced muscle ratio (MR) and feeding diets SPI+AA and CSN resulted in increased intraperitoneal fat ratio (IPFR) relative to fish fed diet FM. Supplementing carnosine to an all-plant protein diet resulted in elevated plasma carnosine and increased muscle free pool anserine. Feeding diets SPI, SPI+AA and CSN resulted in reduced muscle development and increased calpain induced proteolysis. In conclusion, carnosine supplementation did not significantly improve the 100% plant protein diets in regard to the measured growth characteristics above the amino acid supplemented treatments and other unidentified factors may be limiting in the diet causing the reductions in MR and elevated