Effect of quantitative feed restriction and subsequent refeeding on the performance and carcass traits of broilers.

摘要

This experiment was performed to investigate the effect of different approaches of feed restriction and the implication of realimentation in alternative weeks on chick performance and carcass traits. The restriction approaches involved restriction of nutrients, protein and energy and feed intake. 180 day-old Hubbard chicks were weighed and randomly allocated into six experimental groups of 30 chicks each in two trials. Birds in the first group (control) were fed a broiler grower diet containing 20% crude protein (CP) and 3200 kcal ME/kg ad libitum. The diet was offered throughout the experimental period from hatch to 7 weeks old. Chicks of the other five groups were offered the same diet in the starting stage (0-3 weeks). For the second and third groups (trial I), restriction was applied on the dietary CP level, keeping the C/P ratio as that of the control. The CP% was reduced by 5% for group 2 to reach 19 and 3050 Kcal ME/Kg diet and by 10% for group 3 to reach 18% and 2900 Kcal ME/kg diet. In the last three groups, 4, 5 and 6 (trial II), the reduction was not evaluated on the nutrient density but on feed intake, restricting the intake to 80, 70 and 60% of that consumed by the control group, respectively. As a trial to overcome the negativity and to get advantage of the compensatory growth phenomenon, the restriction weeks were interrupted by weeks of ad libitum feeding of the control diet on an alternative basis. On the 4th and 6th weeks was the restriction and on the 5th and 7th was realimentation. Liveweight gains of birds fed energy-protein restricted diets were reduced by 22% in the second and 32.5% in the third group at 6th weeks of age compared to the control, while energy-protein realimentation at 5th week of age resulted in an increase of weight gains by 7.3 and 3.8%. The weekly body weight gain and relative growth rate of birds submitted to food restriction at 4th and 6th weeks of age was significantly (P<0.05) lower when compared to the birds fed ad libitum. Birds were restricted to 80% had the highest gains and best feed conversion ratio followed by 70 and 60% treatments, where the weight gains reached 135.4, 129.4 and 105.2% of that recorded in the control at 5th week of age. No difference between treated groups and control in carcass dressing value and weights of internal organs were observed. However, the abdominal fat content was decreased in slaughtered restricted-refed birds. It is concluded that birds restricted-refed to 80% of the ad libitum intake and those fed 19% CP and 3050 kcal ME/kg had a nearly similar final body weight to that of the control one. Incomplete body weight recovery was obtained with the other groups of high feed restrictions..