Breeds and lines of sheep suitable for production in challenging environments

Implications The resistance of unimproved, indigenous fat-tailed sheep breeds and their composites to ticks and heat make them suitable when challenge conditions are high. Within-breed selection in Merinos resulted in lines resisting challenges from internal parasites, blowfly strike, and sheep lice. Lamb survival benefitted from selection for number of lambs weaned per ewe mated, being able to resist cold stress during a winter lambing season. Variation between breeds as well as between animals within breeds can thereby be exploited to allow the better adaptation of sheep to challenging environments.