بررسي اثر دو نوع جيره غذايي تحت شرايط تنش گرمايي بر عملكرد دو سويه نيمچه گوشتي

Evaluation of Two Feeding Systems in Heat Stress Conditions on Performance of Two Starin Broilers

To evaluate the effect of heat stress and dual feeding system on the two strain of broiler performance, eight hundred one-day old chicks from two starin (Arian and Ross) were used in a factorial experiment. Treatments were two types of feeding system namely dual feeding program and control (standard) and two ambient temperatures (36°c and 24°c). Chicks were raised in normal condition up to 21 days of ages and then divided into two equal groups and reared either in heat stress or in normal ambient temperature. The main experimental period was four weeks. During the first week of study, in the stress group, the temperature was raised by 2°C daily and remained constant at 36°C. Broilers were exposed to stress from 10 AM until 17 PM every day. Control or stressed group was assigned to either standard diet or dual feeding system. High protein fraction of dual feeding system was offered daily from 19 PM to 10 AM and low-protein fraction offered from 10 AM till 17 PM daily. During the first week of the study, due to gradual increase in temperature the effect of heat stress and broiler starin on animal performance were not significant (P>0.05). During second week of the study, weekly feed intake was significaently (P<0.05) higher in Ross than Arian (0.54 vs 0.52 kg, respectively). Dietary regime significantly influenced the weekly feed intake (1.03kg for control and l.11 kg for dual feeding) during second week of study. There were significant effect of starin and feed regime (P<0.05) on broiler growth (0.54kg for Ross vs 0.52kg for Arian and 0.52kg for control diet vs 0.54kg for dual feeding) at the third week of study. Feed conversion ratio was statistically affected by dietary regime (P<0.01) in the first two weeks, but in the third week, only starin significantly affected the feed conversion ratio(l.95 for ross vs 2.07 for Arain). In general using dual feeding program had an advantage of decreasing the adverse effect of heat stress. The growth rate of Ross starin was lower than Arian in this study.