Effect of different levels of dietary protein and choline supplementation on production traits, slaughter parameters, hematology and intestinal morphology in broilers

A total number of 288 one-day-old male broiler chicks (Ross 308) were used to investigate the effect of different levels of protein and choline supplementation in the diet on production traits, carcass parameters, hematology and intestinal morphology. This experiment was conducted in a completely randomized design as factorial experiment (3 × 2). Experimental treatments consisted of three levels of protein (control or recommended level, medium or 1.5 units lower than recommended level and low or 3 units lower than recommended level) and 2 levels of choline supplementation (0 and 1000 mg/kg diet). The results showed that the use of low-protein group reduced body weight gain, villus height and villus height/cryt depth ratio in the jejunum and increased feed conversion ratio in broilers (P<0.05) when compared with control group. The higher relative liver weight and lower red blood cell counts were also observed in the medium-protein group compared with control group (P<0.05). The effect of choline supplementation and interaction between protein levels and choline supplementation in the diet on growth performance, blood hematological parameters and intestinal morphology were not significant. However, choline supplementation tended to increase carcass yield (P=0.087) and to decrease the relative liver weight (P=0.089). According to the results of current study, reducing the dietary protein level, especially 3 units lower than recommended level, negatively affected the production traits and intestinal morphology; but the use of choline supplementation in these diets has no positive effect in broiler chickens.