Performance of hair breeds and prolific wool breeds of sheep in southern Illinois: effect of breed of service sire on lamb production of Suffolk and Targhee ewes.

The effects of year, age of ewe, sex of lamb, breed of ewe, and breed of service ram on fertility, prolificacy, lamb survival, lamb weaning weight, and ewe productivity of Suffolk and Targhee ewes mated to Finnsheep, Combo-6, Booroola Merino, St. Croix, and Barbados rams were estimated. Matings were in four consecutive years using three rams per breed of service ram each year, with a total of 758 ewe-year observations. There was a significant effect of year on fertility, prolificacy, and ewe productivity. Two- and three-year-old ewes had lowest (P < .05) fertility rates, whereas 3-, 4-, and 5(+)-yr-old ewes had higher (P < .01) prolificacy and ewe productivity than 2-yr-old ewes. Ram lambs were .9 kg heavier (P < .01) at weaning than were ewe lambs. Suffolk ewes gave birth to .13 more (P < .05) lambs per ewe lambing, and their lambs were 1.4 kg heavier (P < .01) than lambs from Targhee ewes. Ewes mated to St. Croix and Barbados rams had higher (P < .10) fertility rates than ewes mated to Finnsheep rams. Lambs sired by Barbados, Finnsheep, and St. Croix rams had higher (P < .05) survival rates to weaning than lambs sired by Booroola Merino rams. The heaviest (P < .01) lambs at weaning were those sired by Finnsheep and Combo-6 rams. Ewes mated to hair-breed rams had greater (P < .05) performance for the fitness traits of fertility and lamb survival but lower (P < .01) lamb weaning weights than ewes mated to wool-breed rams.(ABSTRACT TRUNCATED AT 250 WORDS)