Effects of dietary methionine hydroxy analogue supplement on growth, protein deposition and intestinal enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)

Abstract

A total of 900 juvenile Jian carp (Cyprinus carpio var. Jian) (8.24 ± 0.03 g) were fed practical diets containing graded levels of methionine hydroxy analogue (MHA) (0, 5.1, 7.6, 10.2, 12.7 and 15.3 g kg⁻¹ diet) for 60 days to investigate the effects of MHA on growth, protein deposition and intestinal enzymes activities. Per cent weight gain (PWG) significantly increased with increasing levels of MHA up to a point (P < 0.05), and thereafter declined. Feed efficiency was the highest when MHA level was at 5.1 g kg⁻¹ diet. Feed intake (FI) significantly enhanced with dietary MHA level up to a point (P < 0.05), beyond which it plateaued. Patterns of differences in protein production value, lipid production value, intestosomatic index, folds height, lipase, chymotrypsin, γ-glutamyl transpeptidase, Na⁺, K⁺-ATPase, creatinekinase, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase activities were the same as that in PWG, whereas the trend of plasma ammonia content was opposite. Hepatopancreas protein content, trypsin and amylase activities followed the same trend as that of FI. The optimal supplemental level of MHA for fish meal and miscellaneous meals-based diet (6.9 g methionine kg⁻¹ diet) for PWG was 8.2 g kg⁻¹ diet by the quadratic regression analysis.