Effect of dietary protein levels and feeding rates on growth performance, production traits and body composition of Nile tilapia, Oreochromis niloticus (L.) cultured in concrete tanks

Abstract

A 28-week feeding trial was conducted in concrete tanks with Nile tilapia, Oreochromis niloticus (L.) with an average initial weight and length of 61.9 � 6.03 (g ¢sh � 1 )a nd 17.6� 0.45 (cm ¢sh � 1 ), respectively, to examine the eiect of two protein levels and three feeding levels (% body weight (BW) day � 1 )o n growth performance, production traits and body composition. Twelve 4-m 3 concrete tanks (2 � 2 � 1.25 m, long, width and height) were each stocked with 100 ¢sh and fed diets containing either 25% or 30% crude protein at rates of 1%, 2% and 3% BW daily (2 � 3 factorial experiment). The results revealed that there was no signi¢cant increase in growth rate with increasing dietary protein levels, whereas there was signi¢cant increase in growth rate with increasing feeding levels (P � 0.05). The same trend was also observed for mean BW (g), mean body length (cm), production rate (kg m � 3 ), speci¢c growth rate (SGR % day � 1 ), feed conversion ratio (FCR), condition factor (K) and survival rate (%). The best ¢nal mean BW (g), ¢nal mean body length (cm), SGR (% day � 1 ), FCR, K, production rate (kg m � 3 ) and survival rate (%) were recorded in groups of ¢sh fed with 25% dietary protein at the 2% feeding level.Whole ¢sh fat and energy contents were not signi¢cantly in£uenced (P40.05) by protein levels and feeding levels. Protein and ash contents were signi¢cantly (P � 0.05) in£uenced by feeding level, but not by dietary protein level. Economic evaluation indicated that dietary protein 25% (diet A) at the 2% BW day � 1 feeding level was the most cost-eiective and aiordable feed strategy for farmers. We conclude that a 25% protein diet fed at 2% BW day � 1 is recommended for adult Nile tilapia reared in concrete tanks.