عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Effect of two fattening systems were studied on feedlot performance and carcass characteristics of using of 66 Fars native male kids in different ages. Six kids were slaughtered at the first day of experiment and sixty kids were divided into two groups. The first group were kept in feedlot in individual pens and the second group grazed on rangeland, and after 3 months, were kept in feedlot in individual pens. The fattening period for first and second groups were 9 and 6 months respectively. Eight kids from each system were slaughtered randomly at the 6, 9 and 12 months of age, for recording carcass characteristics. Live body weights in each age class were different (P<0.01) between two systems. Daily weight gains changes in periods of 3 to 6, and 6 to 9 months of age in two systems and were different (P<0.01), but for period of 9 to 12 months of age were not different (P>0.05). Feed conversion ratios in period 6 to 9 months of age were different (P<0.01) between two systems, but was not differed in period 9 to 12 months of age (P>0.05). Cold dressing percentages at 6 and 9 months of age were different (P<0.05) between two systems. Valuable carcass cuts (leg, shoulder and loin) percentages in each age were the same between two systems (P>0.05). Carcass lean and bone percentages in each age were the same between two systems (P>0.05). Carcass fat deposited percentages at 6 months of age were different (P<0.05), but were not different at 9 and 12 months of age between two systems (P>0.05). Live body weights, daily weight gains, feed conversion ratios, dressing percentages, Carcass lean, fat deposited and bone percentages in each age were different (P<0.01) between two systems. Average live body weight of kids at 6 months of age after 3 months of range grazing (system 2) were 18.54 kg and average live body weight of kids at 6 months of age after 3 months of fattening (system 1) was 25.5 kg. Live body weight of grazing kids decreased at the beginning of grazing on range and after that had low gain on range, and also had low gain in feedlot. Therefore, feedlot in system 1 had better efficiency. With increaseing the age, feedlot efficiency decreased in two systems and internal fat and carcass fat deposited percentages increased along with carcass quality decreasing. Fattening of kids just after weaning (system 1) in a period of three months is suggested.