GENETIC EVALUATION OF EWE PERFORMANCE IN OUTAOUAIS-ARCOTT AND SUFFOLKSHEEP AND THEIR CROSSES

Ewes from a newly developed sheep breed in Canada, the Outaouais Arcot t, consistently out-performed Suffolk ewes in prolificacy at birth and at 42 d of age by 0.37 lambs at first parity and by 0.55 and 0.41 lam bs, respectively, over all parities. In contrast, mean litter weights of Suffolk and Outaouais ewes did not differ at these times. Additive genetic effects in prolificacy and litter weight tended to favour the Outaouais breed over the Suffolk breed at first parity. Corresponding values over all parities were significant, favouring the Outaouais, fo r both prolificacy and litter weight at 42 d of age. Suffolk ewes exce lled in maternal genetic effects for litter weight for all parities at birth and 42 d of age. Reciprocal cross ewes of the Outaouais and Suf folk breeds were similar (P > 0.05) in prolifacacy and litter weight. In general, crossbred ewes consistently exceeded Suffolk ewes in proli ficacy but were not significantly different from Outaouais ewes. Thoug h not always significant, crossbred ewes exceeded the average of their purebred parents in prolifacacy and litter weight. Furthermore, estim ates of heterosis were always positive, and the 19% value for litter w eight at 42 d of age at first parity was significant. This study, cond ucted over 6 yr, demonstrates the superiority of the Outaouais breed f or production of commercial crossbred ewes to perform in a moderately intensive, semi-confinement operation. This superiority exists in addi tion to the previously-established ability of the Outaouais ewe to pro duce large litters in an 8-mo breeding cycle.