Reproductive performance and productivity of Menz and Horro sheep lambing in the wet and dry seasons in the highlands of Ethiopia

Abstract

Ewe reproduction and productivity were studied in the highlands of Ethiopia in Horro and Menz ewes mated to lamb in both the wet and dry seasons from June 1992 to May 1997. The data included a total of 4890 mating records of which 2516 were Menz ewes and 2374 Horro ewes, with 2360 matings in the wet season and 2530 in the dry season. Menz sheep had a significantly higher (P < 0.001) weaning rate (lambs weaned per ewe mated) than the Horro ewes (0.73 versus 0.57, respectively) and ewes which lambed in the wet season had a significantly higher (P < 0.001) weaning rate than those that lambed in the dry season (0.76 versus 0.53, respectively). Menz ewes showed their superiority in weaning rate over the Horro ewes more clearly when lambing in the wet season (0.85 versus 0.67, respectively) than when lambing in the dry season (0.59 versus 0.47, respectively). Overall flock productivity was expressed in terms of potential offtake of yearling sheep from flocks of Menz or Horro ewes lambing in either the wet or dry seasons. Both in terms of number of yearling sheep for sale and total live weight for sale, the offtake of a flock of Nlenz sheep in this environment was approximately three-fold greater than a flock of Horro sheep when they lambed in the wet season and approximately two-fold greater when they lambed in the dry season. Season had no effect on offtake in Horro ewes, but the Menz ewes lambing in the wet season had about a 1.5-fold greater offtake than Menz ewes lambing in the dry season. In the first 3 years of the study (1992-1995), oestrous synchronisation was used at each mating. Oestrus was synchronised with intravaginal sponges containing 40 mg flugestone acetate (FGA). Most of the ewes (83% ) came in oestrus after hormonal treatment and out of these 81% were synchronised and mated within 5 days after sponge removal. The percentage of ewes synchronised was 10% higher after treatment in the wet season than in the dry season (P < 0.01) and 7% higher for Menz sheep than for Horro sheep (P < 0.01). Of the ewes that eventually lambed, 73, 17 and 10%, respectively, conceived at the first, second and third or subsequent oestrus with an average 1.5 services per pregnancy.