Production of fine-wool ewes on yearlong rangeland in West Texas. II. Effects of supplemental feed and breeding frequency on reproductive rate.

Reproductive rate was compared in once-a-year and accelerated lambing ewes given various winter supplemented feed treatments during a 4-yr study. The study involved 165 commercial Rambouillet ewes. The accelerated lambing ewes had a lower attrition rate (P = .20) and final weight (P less than .05) and produced more lambs (P less than .01), lighter weight lambs at birth (P less than .05) and weaning (P less than .01), a lower frequency of twins (P less than .05) and an equal total weight of weaned lamb (P greater than .25) compared with once-a-year lambing ewes. Significant effects of feeding were detected only in a higher attrition rate in fed vs control ewes (P less than .02) and in a higher twinning frequency in fed vs control ewes (P less than .05). It is suggested that attrition rate is positively associated with twinning frequency. Accelerated lambing failed to substantially increase total lamb production, primarily because fall-lambing ewes failed to rebreed for summer lambs in spite of supplemental feed and as a result, continued in a fall lambing pattern.