Effect of dietary protein concentration on feed intake, body mass gain and carcass traits of Rhode Island Red chicken

Abstract

The effect of dietary crude protein (CP) concentration on dry-matter intake (DMI), body mass gain (BWG) and carcass traits of Rhode Island Red (RIR) chicken was determined through a 12-week feeding trial (10−93 days of age) in southern Ethiopia. Diets were formulated to contain 140 (T1), 160 (T2), 180 (T3), 200 (T4) and 220 (T5) g CP kg-1 DM from maize, wheat bran, soybean, sunflower cake, Niger seed (Guizotia abyssinica) cake, salt, rear premix, lysine and methionine. ME (14.36−14.84 kJ kg-1 DM) and other nutrients in diets were similar. Ten chicks were randomly distributed to each of four replicates of five treatment diets in a completely randomized design. Chicks were raised in groups, and the feed offer and refusal measured daily. Body mass was measured weekly. At the beginning of the experiment, four male (1 per replicate) and four female (1 per replicate) chicks whose body mass was closest to the mean body mass of their respective groups and sexes, were selected per treatment, fasted for 12 h, weighed, slaughtered and parts of the carcass weighed. Differences in DMI and BWG of chicks fed different levels of dietary CP were not significant. Diet T2 was as efficient as the higher CP diets but more efficient than T1 in DM utilization. Chicks fed on diet T2 had significantly (P<0.05) higher total non-edible offal (TNEO) than those fed on T1, and TNEO of chicks fed on diets T3, T4 and T5 were in between. Differences in carcass mass were not significant (P<0.05) among treatment groups. Chicks fed on diet T1 had significantly (P<0.05) higher dressing percentage than those on diets T3 and T5, but similar to those on diets T2 and T4. The highest net return was from diet T2, but it was close to T1. Mortality of chicks was observed only in T1 (2.5%) and T5 (12.5%). The results suggest that 160 g CP kg-1 DM is optimum for growing RIR chicks in tropical climates from 10−93 days of age.