INTERACTION EFFECT OF DIETARY CRUDE PROTEIN AND ORGANIC ACIDS ON GROWTH PERFORMANCE, CARCASS CHARACTERISTICS AND IMMUNE ORGANS OF BROILER CHICKS

Document Type : Original Article

Authors

Animal Production Department, Faculty of Agriculture, Suez Canal University, Ismailia 41522, Egypt.

Abstract

An experiment was designed to investigate the effect of feeding two crude protein levels (PL): Required protein level (RPL), 2% lower (LPL) and two organic acids (OA; citric, CA and fumaric, FUA) each at 0, 1.5 and 3% of the diet on the productive performance of broiler chicks (0-6 wks of age). Two hundred eighty-eight one-day old unsexed chicks (Cobb 500) were randomly divided into 12 treatments of 3 replicates (8 chicks each). Three types of corn-soybean meal diets were fed. Starter diet (0-3 wks of age; contained 23 and 21% crude protein, CP), grower diet (4-5 wks of age; contained 20 and 18% CP) and finisher diet (the 6th wk of age; contained 18 and 16% CP). Diets were formulated to be isocaloric (3200 Kcal/Kg diet). Average daily gain (ADG) and average daily feed intake (ADFI) were significantly increased for most periods with RPL diets. Feed and caloric conversion ratios (FCR and CCR) were significantly improved with RPL (starter) or LPL diets (finisher). Crude protein conversion ratio (CPCR) was improved (P<0.05) with LPL diets during all periods. Dressing, meat %, and meat to bone or fat ratios were increased (P≤0.05) and abdominal fat % was decreased with RPL diets while LPL diets increased bursa and proventriculus %. Bursa % was significantly increased due to CA addition. The highest ADFI and the worst (P<0.05) FCR, CPCR and CCR were recorded with 0% OA diets compared with 1.5% or 3% diets. The highest significant dressing % and meat: fat ratio and the lowest (P<0.05) abdominal fat % were obtained with 1.5% OA diets. Diets supplemented with 3% OA significantly improved thymus %. Significant differences in growth performance and carcass criteria due to the combined effects of PL, OAT and OAL were obtained. Diet of RPL+ 1.5% CA increased (P<0.05) ADG (starter and finisher), percentages of giblets, liver, dressing, meat: fat ratio and decreased abdominal fat. However, RPL+1.5% FUA diets significantly improved ADG (grower and total periods), FCR, CPC and CCR. The highest values of thymus and bursa were reported with RPL+ 3% CA diet. No mortality was recorded with RPL or LPL+1.5 CA or FUA diets.

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