Productivity of Sardi, D’man and their crossbred ewes mated to terminal sires

Abstract

Reproductive performance of 165 contemporary non-prolific Sardi (S), prolific D’man (D) and ¼-D, ½-D and ¾-D crossbred ewes mated to Ile-de-France (IF) and Mérinos Précoce (MP) rams, and growth and survival of their 209 lambs were analysed in order to assess the performance in a terminal crossbreeding system. Breed group of ewe had a significant effect on the litter size and ovulation rate, but not on embryo survival. The lowest litter size and ovulation rate were recorded for Sardi ewes, the highest for D’man and ¾-D ewes, and the other breed groups were intermediate, with an increase tendency as the proportion of D’man genes increased in the ewe genotype. Moreover, litter weight at birth and litter size at 60 days were affected by breed group of ewe, but conception rate and litter weight at 60 days were not influenced. Litter weight at birth of purebred and crossbred D’man ewes was the heaviest and that of Sardi breed was the lowest. Litter size at 60 days was the lowest for Sardi ewes, the highest for purebred D’man ewes and intermediate for crossbred D’man ewes. Sardi ewes weaned 0.49, 0.53, 0.88 and 1.05 lambs less than ¼-D, ½-D, ¾-D and purebred D’man ewes, respectively. Except conception rate on which service ram breed had a significant effect, the other reproductive traits were unaffected. Conception rate of ewes sired to MP rams was 19% lower than that of ewes mated to IF rams.Breed group of dam influenced significantly lamb weight at birth, at 30 days and at 60 days, but not lamb survival prior to weaning. Lambs born to Sardi and ¼-D crossbred dams had the highest weights, those from D’man and ¾-D dams had the lowest weight, and those from ½-D ewes were intermediate. Extreme differences between weights of lambs from different breed groups of dams were 0.78kg at birth, 1.72kg at 30 days, and 2.00kg at 60 days. Breed of sire had a significant effect on lamb weight at 30 days only. Lambs sired by IF rams were 0.62kg heavier at 30 days than those sired by MP rams. It was concluded that in a terminal sire production, using ¼-D, ½-D and ¾-D crossbred ewes would be better than the use of non-prolific purebred ewes, since this system takes advantage of increased reproductive capacity in the ewe with sensible increase in lamb performance.