Effects of different dietary crude protein contents on growth performance and visceral organ mass in fattened Awassi lambs

Abstract

This study was conducted to investigate the effects of different crude protein (CP) feeding strategies on the growth performance, food intake and visceral organs weights of Awassi lambs during fattening. Forty eight weaned male Awassi lambs were randomly divided in 4 equal groups according to the diet regimen: whereas the CP content remained constant during the whole 16 week fattening period in diets distributed to the first 3 groups, 12%, 16% and 18% respectively, it was gradually and monthly decreased from 20% to 14% in the diet distributed to the 4th lamb group. The body weight gains and the food intakes in lambs fed with the decreasing CP content diet compared to the other groups were markedly and significantly increased since the 8th week and the 5th week respectively, although these 2 parameters were moderately delayed around the 12th week until the end of the experimental fattening period in all lambs. In addition, the food efficiency was significantly enhanced in animals receiving diets with the decreasing CP content or high protein content (18%). The hot and chilled carcass weights as well as the visceral organ (lungs, kidneys and liver) relative weights were also more elevated in these 2 groups while the kidney fat proportions were significantly decreased. These results show that a gradual decrease in the dietary protein content (from 20% to 14%) during fattening markedly improves the growth performance and the visceral organ mass in lambs, leading to an important reduction in the meat production cost.