Factors affecting fertility in a flock of dorper sheep

Abstract

The present study was based on 1427 matings and lambing records of a flock of Dorper sheep kept at Ol'Magogo farm which is situated in the medium potential zone of Kenya. Genetic and non-genetic sources of variation in number of lambs born per mating were estimated. Of all the non-genetic factors considered seasons, pre-mating body weight, year x season interaction and years (in order of their importance) influenced number of lambs born signifi cantly. Generally in all years more lambs were born when conception took place during a wet season than during a dry season. Number of lambs born per mating fluctuated greatly within seasons between years, with the largest deviations observed within the dry season. Pre-matinq body weight influenced number of lambs significantly, one percent more lambs were born per kilogram increase in body weight. Age, ram, lambing interval, year x age and age x season interactions did not have significant effects on number of lambs born per mating. The additive genetic variation in number of lambs born per mating was estimated as 9 % using a half-sib analysis. From the present study it was concl uded that for this flock, ewes can be mated at an earlier age and that three lamb crops every two years appears feasible under proper management. If selection of ewes for fertility is anticipated, their reproductive performance should be compared within seasons and years.