REPRODUCTIVE-PERFORMANCE AND MILK-PRODUCTION OF THE IMPROVED AWASSI BREED AS COMPARED WITH ITS CROSSES WITH THE BOOROOLA MERINO

Ovulation rate, embryo survival, lamb production, lamb survival and mi lk production of Awassi and Booroola-Awassi crossbred ewes, kept indoo rs, were compared. Awassi were non-carriers while Booroola X Awassi (F -1) and about half of 3/4 Awassi-1/4 Booroola (BC1) ewes were heterozy gous at the FecB gene. Mean ovulation rate increased by 1.5 to 1.6 cor pora lutea per ewe ovulating and prolificacy by 0.7 lambs born per ewe lambing in F-1 and BC1 (B+) ewes as compared with Awassi. Embryo surv ival rates in BC1 ewes with two, three and four ovulations were 0.83, 0.68 and 0.71, respectively. Lamb survival rates at 1 day of age were 0.93, 0.90 and 0.77 and average birth weight teas 4.9, 4.0 and 3.0 kg for lambs born as singles, twins and triplets, respectively. Average m ilk production of the Awassi tons 506 l per ewe per lactation. F-1 and BC1 ewes produced respectively proportionately 0.48 and 0.63 of the A wassi milk production and there was no significant difference in milk production between BC1(B+) and BC1(++) ewes. The relatively low milk p roduction of the Booroola Awassi crosses suggests that heterosis and r ecombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb productio n in the Awassi without affecting its milk production.