Evaluating Texel-, Suffolk-, and Columbia-Sired Offspring: I. Prolificacy, Survival, and Preweaning Growth Traits Under a Forage-Based Lambing System1

A terminal sire study was conducted over a 2-yr period to evaluate production traits of Texel-sired offspring compared with Suffolk- and Columbia-sired off-spring in a pasture-lambing system. Polypay x Dorset crossbred ewes were mated to Texel, Suffolk, or Columbia rams for a 35-d breeding season commencing in December of each year. The ewes were wintered outdoors on alfalfa hay (54.5% TDN and 16% CP; as-fed basis) at a level to meet their NRC (1985) requirements. The ewes were not fed any concentrate during late gestation or lactation. A total of 279 lambs were born with an average of 1.7 lambs per ewe. Prolificacy, litter birth, and weaning BW (WBW) were largely unaffected by sire breeds (SB). Birth BW (BBW), WBW, and 60-d adjusted WBW (Adj-WBW) of lambs sired by Texel rams were 5.3, 24.5, and 18.4 kg, respectively, and were comparable with lambs sired by Suffolk rams (5.4, 24.7, and 18.4 kg, respectively) but were greater (P<0.05) than those for lambs sired by Columbia rams (4.7, 22.0, and 16.2 kg, respectively). Preweaning ADG for lambs also showed a similar trend (P<0.05) and were 238, 237, and 209 g, respectively, for lambs sired by Texel, Suffolk, or Columbia rams. However, survival rate (SR) to weaning for lambs sired by Texel, Suffolk, or Columbia rams did not differ. As litter size increased, lamb BBW, WBW, Adj-WBW, ADG, and SR all decreased (P<0.001). In the pasture-lambing system, an estimated $19.21 in feed cost per ewe per year was saved as compared with a more intensive shed-lambing system. It was concluded that Texel rams, used in a forage-based lambing system, sired offspring that performed equal to those of Suffolk sires and better than those sired by Columbia rams. In addition, as litter size increased, lambs had lesser BBW and SR as compared with single-born lambs, which indicated that highly prolific ewes might be less suitable for pasture-lambing systems such as the one used in this study. Finally, a pasture-lambing system as described may greatly reduce ewe feed costs as compared with more intensive shed-lambing systems.