Effect of breed and season on production and response to infections with gastro-intestinal nematode parasites in sheep in the highlands of Ethiopia

Abstract The effects of breed (Menz and Horro), season (wet and dry), and the breed by season interaction on production and response to naturally acquired gastro-intestinal (GI) nematode parasite infections (predominantly Longistrongylus elongata and Trichostrongylus spp. and a small proportion of Haemonchus contortus ) of lambs in the highlands of Ethiopia were investigated. A total of 2395 Menz and 1966 Horro lambs, born from five lambings in the wet season and five lambings in the dry season, were recorded in the study from birth to 12 months of age. These were the progeny of 43 Menz and 41 Horro rams. Horro lambs were significantly ( P P P >0.001) packed cell volume (PCV) than the Horro lambs at 3 and 12 months of age, possibly indicating a better adaptation of the Menz to a high altitude environment. The Menz lambs had significantly ( P