Comparison of Sumatra sheep and three hair sheep crossbreds. II. Reproductive performance of F1 ewes.

摘要

196 Sumatran, Java fat-tail [Indonesian Fat-tailed] X Sumatran (E1), Virgin Island [Virgin Islands White] X Sumatran (H1) and Barbados Blackbelly X Sumatran (B1) ewes were mated to rams of the same breed type. The ewes were first exposed to rams at10 or 13 months of age and reproductive performance was monitored until each ewe had reared 2 litters. Data from 363 lambings and 563 lambs were collected. Mean age at 1st and 2nd lambing was 516 and 733 days, respectively. Litter size at birth ranged from 1 to 5 lambs with a mean of 1.55, and preweaning mortality was 11.7%. There were no significant effects of breed type on age at lambing, lambing interval, litter size or mortality. The mean birth weights of lambs born to the Sumatran, E1, H1 and B1 ewes were 1.45, 1.62, 2.03 and 2.10 kg, respectively, with weaning weights of 8.5, 9.2, 11.7 and 12.1 kg. The differences among breed types were significant (P<0.001) except for H1 and B1, which were similar. Litter size affected (P<0.001) birth weight, weaning weight and pre-weaning mortality. A dam productivity index (DPI) for each ewe was calculated from the total weight of lamb weaned at the first 2 lambings divided by a measure of age. DPI averaged 16.0, 18.1, 21.5 and 24.2 kg for Sumatran, E1, H1 and B1, respectively (P<0.001). Average body weight of ewes at 2nd lambing was 22.0, 24.4, 27.2 and 28.1 kg for Sumatran, E1, H1 and B1, respectively. Productivity expressed in terms of weight of lamb weaned per unit body weight of ewe was 0.73, 0.74, 0.79and 0.86 for Sumatran, E1, H1 and B1 breed types. DPI was slightly higher for ewes mated at 10 months of age than at 13 months.