Data representing 1928 lambing records were analysed to study the effects of inbreeding and cross-breeding on lamb survival to the ages of 7, 30, 120 and 180 days. The sheep flock consisted of two native breeds, Barki (B) and Rahmani (R); and the imported Fleisch Merino (M) as well as the crosses M x B and M x MB. Analysis was made by fitting a least-squares linear model that included the main effects of year and season of birth, sex, age of dam, type of birth, inbreeding of the lamb (F o ) and the dam (F d ) and breed group and the interactions season x type of birth, season x F o and season x breed group. Lambs were classified into six groups according to the magnitude of the inbreeding coefficient: F «£ 0-05, 0-05 < F «S 0-10, 0-10 < F s£ 0-15, 0-15 < F ^ 0-20, 0-20 < F s£ 0-25 and F > 0-25. The average inbreeding coefficient in the flock was 0-12 and 0-08 for the lambs and their dams, respectively.Sex of lamb and age of dam had no significant effect on lamb survival at any age while single-born lambs had a higher (P < 0-01 or P < 0-05) survival than twins at all ages except 7 days. Inbreeding of the lambs showed significant effect at 7 and 120 days.

No abstract

No abstract