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 milk production of Awassi and Booroola-Awassi crossbred ewes, kept indoors, 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 heterozygous at the FecB gene. Mean ovulation rate increased by 1.5 to 1.6 corpora 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 survival 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 milk 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 Awassi milk production and there was no significant difference in milk production between BC1(B+) and BC1(++) ewes. The relatively low milk production of the Booroola Awassi crosses suggests that heterosis and recombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb production in the Awassi without affecting its milk production.