EFFECT OF LOW-PROTEIN IN ISO-ENERGETIC DIETS ON PERFORMANCE, CARCASS CHARACTERISTICS, DIGESTIBILITIES AND PLASMA LIPIDS OF BROILER CHICKENS

Abstract

This study was conducted to determine the effect of low or high proteindiets with constant ME on growth performance, carcass characteristics, digestibilities andblood parameters of Cobb Avian 48 broilers from 1 to 34 d of age. A total number of 2080one-day-old chicks were housed randomly in 16 pens and divided into two experimentalgroups, each group divided into 8 replicates and each replicate has 130 birds/ pen. All birdswere fed pre-starter diet (CP, 23% and ME, 2950 kcal/kg) for 4 days then the birds weredivided into two experimental diets which were formulated to have 2 levels of CPrespectively, in each phase: 22 and 21% CP with 3050 kcal/kg in the starter phase (5 to 10d); 20 and 19% CP with 3100 kcal/kg in the grower phase (11 to 25 d); and 19 and 18% CPwith 3180kcal/kg in the finisher phase (26 to 34 d). Digestible Lysine was maintained at1.22, 1.12, and 0.96% of the diet in the starter, grower, and finisher periods, respectively.Body weight gain, feed intake and feed conversion as well as thigh and liver weights werenot influenced by changing protein level in the diets. However, carcass weight and breastmuscle weight were increased significantly (P≤ 0.05). On the other hand, abdominal fatweight was deceased (P≤ 0.05) by feeding low protein diet. Although, dry matter and crudefat utilization were not affected, while, crude protein and crude fiber utilization wereimproved by feeding low protein diets. Plasma GOT, GPT and total cholesterol were notchanged, while; plasma HDL was increased by feeding low protein diets. Furthermore, itwas observed a decrease in muscle and liver MDA by feeding low protein diets, indicatingthe improving of the anti-oxidative activities by decreasing the protein content in broilerdiets. Economic efficiency was improved by feeding low protein diets compared to highprotein diets. In conclusion, feeding Cobb Avian 48 broilers on 1% lower protein diets thanthe strain recommendation, at constant ME, with the same amino acids levels had notadversely affected the growth performance, carcass parameters and liver functions, while;dietary crude protein and crude fiber utilization were improved.