Effect of Onset of Fattening Period on Performance of Lori Lambs in Two Fattening Systems

Sixty Lory male lambs with average live weight of 28 ± 1.5 and average age of 105 ± 10 days were used to measure the effects of feed restriction on intake, growth rate and carcass characteristics. Animals were randomly divided into two equal groups of a control and a treatment (restricted), each having 30 lambs. After a period of adaptation to hand feeding, the control group divided to 3 sub-groups (replicates) of 10 lambs and fed ad libitum. The restricted group also divided in 3 replicates and fed on a natural pasture for 11 weeks (restriction period) and then received the same ration as the control group for following 17 weeks (re-alimantation period). Animals were weighed weekly and the amounts of consumed feed were measured daily. Six lambs from each group were slaughtered at the end of restriction period and six lambs of each group also were slaughtered at the end of experiments to determine the body and carcass characteristics. During restriction period (11 weeks), the live weight of animals in restricted group reduced by about 4.72 kg (about 14.85 percent of their initial weight), on average. But the animals in control group gained about 15.15 kg live weight. After three weeks re-alimentation, the feed intake of restricted group increased and was 18.5 % more than Control group and was significantly (P 0.05) higher by the of experiment. During re-alimentation period, the growth rate of restricted animals was about 1.6 times of that in control animals (276 versus 168 g/gay). After restriction period, the slaughter weight, carcass fat content, warm and cold carcass weight and fat-tail weight were significantly (P 0.05) lower than control animals. At the experiment, the ratio of meat production was higher in restricted animals. The measurable fat content ratio in fat-tail was lower. In addition, at the end experiment, the total fat content in restricted animals was significantly (P 0.05) lower than control animals (5.71 versus 6.65 kg). However, the final weight of restricted animals was lower than control animals, but the difference was not statistically significant. These results showed that 11 week restriction period had not considerable effect on final slaughter weight of lambs.