Re-evaluation of Dietary Methionine Requirement by Plasma Methionine and Ammonia Concentrations in Surgically Modified Rainbow Trout, Oncorhynchus mykiss

Bae, Jun-Young; Ok, Im-Ho; Lee, Seunghyung; Hung, Silas S. O.; Min, Tae Sun; Bai, Sungchul C.

doi:2011.24.7.974

Article

Poultry and Laboratory Animal Nutrition

Asian-Australasian Journal of Animal Sciences 2011;24(7): 974-981.
https://doi.org/10.5713/ajas.2011.10189 Published online June 21, 2011.

Re-evaluation of Dietary Methionine Requirement by Plasma Methionine and Ammonia Concentrations in Surgically Modified Rainbow Trout, Oncorhynchus mykiss

Jun-Young Bae, Im-Ho Ok, Seunghyung Lee, Silas S. O. Hung, Tae Sun Min, Sungchul C. Bai

Abstract

This study was designed to re-evaluate the dietary methionine requirement by means of the plasma methionine and ammonia concentrations in surgically modified rainbow trout, Oncorhynchus mykiss. A total of 35 rainbow trout averaging 505??.5 g (initial body weight, mean??SD) were randomly distributed into seven groups with five fish in each group. After 48 h of feed deprivation, each group of fish was fed one of seven L-amino acid based diets containing 0.5% cystine and graded levels of methionine (0.25, 0.40, 0.50, 0.60, 0.70, 0.80 or 0.95% of diet, dry matter bases) by intubation at 1% body weight on dry matter basis. Blood samples were taken at 0, 5 and 24 h after intubation. Post-prandial plasma free methionine concentrations (PPmet, 5 h after intubation) and post-absorptive plasma free methionine concentrations (PAmet, 24 h after intubation) of fish fed diets containing 0.60% or higher methionine were significantly (p<0.05) higher than those of fish fed diets containing 0.50% or lower methionine. PPmet and PAmet in fish fed diets containing 0.60% or higher methionine were not significantly different except PPmet of fish fed diet containing 0.95% methionine. Post-prandial plasma ammonia concentrations (PPA, 5 h after intubation) of fish fed diets containing 0.70% or higher methionine were significantly higher than those of fish fed diets containing 0.60% or lower methionine, and PPA of fish fed diets containing 0.25 and up to 0.60% methionine were not significantly different from each other. Broken-line model analyses on PPmet, PAmet, and PPA indicated that the dietary methionine requirement of rainbow trout was between 0.59 (1.69) and 0.67 (1.91) % of diets (% dietary protein bases) when the diets contained 0.5% cystine.

Keywords: Methionine; Rainbow trout; Requirement; Intubation; Plasma; Ammonia