Postweaning performance and carcass characteristics of crossbred ewe lambs produced in accelerated or annual lambing systems.

Weaning, postweaning and carcass characteristics of ewe lambs were analyzed to determine if significant interactions occurred among management options. Management options considered were type of lambing system, choice of maternal and terminal sire lines and month of birth within lambing system. In general, significant interactions were not observed, suggesting production (output) characterizations for the postweaning period can be extended across management options. The experimental protocol associated with the types of lambing system resulted in a highly significant effect of lambing system upon all characteristics, especially in relation to age, weight and feed consumption characteristics prior to slaughter. Suffolk-sired lambs tended to be heavier for most weight characteristics, fatter and have higher carcass quality and leg conformation scores relative to Columbia-sired lambs. Differences of fraction of Finn sheep (Finn, .50 vs .25) of the dam were not noted, with the exception of weaning weight (21.2 +/- .28 and 22.2 +/- .27 kg, respectively) and carcass quality and leg conformation scores. Within the annual lambing season, lambs born in March and April were heavier at weaning, consumed less feed and required less weight gain to attain market weight than lambs born in May. Lambs from the May lambing had significantly higher gross feed efficiency ratios. Within the accelerated lambing system, the lambs born in January to February period tended to be heavier than lambs from the other lambing periods. Observed differences among month of lambing within lambing system for other characteristics were not consistent.