Effect of cysteine and dietary protein levels on striped mullet (Mugil cephalus) performance

Nader E. El-Tawil, Talaat N Am

Abstract

This experiment was conducted to study the effect of cysteine (CYS) and different dietary protein levels on growth performance, survival rate, feed utilization and body composition of striped mullet (Mugil cephalus) fry (2.1g initial body weight). Six experimental diets were formulated to contain three levels of protein (16, 20 and 24%) each supplemented with or without 1% cysteine. Diets were isocaloric (4.25 kcal gross energy/g diet). Each diet was fed in triplicate groups of 10 fish each twice daily to apparent satiation for 10 weeks. The results showed that growth performance was significantly affected by increasing dietary protein level and supplemented cysteine in the fish diet (P<0.05). Fish fed CYS-diets showed significantly higher growth performance parameters and better feed utilization than fish fed on other diets. Moreover, fish fed CYS-diets containing 24% protein were significantly higher in growth performance values compared to other treatments. Survival rate increased significantly (P< 0.05) with increasing dietary protein level and supplemented cysteine in the fish diet. These results suggest that balancing fish diets containing 24% crude protein supplemented with 1% cysteine level, has significant impacts on growth performance and the feed utilization outcomes of striped mullet (Mugil cephalus) fry.