Influence of management system on litter size, lamb growth, and carcass characteristics in sheep

Three management systems (winter, spring, and late summer) distinguished by season of lambing and management practices were compared for litter size b orn and weaned and growth and carcass characteristics of lambs. Three sire breeds (Cheviot, Rambouillet, and Suffolk) and three dam breeds (Florida Na tive, Native-X, and Synthetic-X) were used in 698 matings over a 3-yr perio d. System affected (P < .01) litter size born. Spring lambing yielded more lambs (1.62) than winter (1.49) and late summer (1.12). The winter-born lam bs were lighter but fatter (P < .05), and spring-born lambs were leaner wit h higher leg conformation and carcass quality scores. The late summer-born lambs were not different from spring-born lambs. Wethers had higher (P < .0 1) weights off test than ewe lambs (43.9 vs 42 kg) but had lower (P < .01) leg conformation scores, percentage kidney and pelvic fat, yield grade, and dressing percentages. Dam breed effects were significant (P < .05) for ave rage preweaning daily gains with 249 +/- 5, 201 +/- 9, and 191 +/- 9 g for progeny of Native-X, Florida Native, and Synthetic-X, respectively. Single- born lambs had higher daily gains (P < .05) than twins in a preweaning peri od in all management systems and higher postweaning and lifetime daily gain s for winter and spring management systems.