This study was carried out to assess effect of mutual mating and some environment and genetic factors on reproductive and production performance of Barri and Tehami sheep owned by the regional central highlands research station, Dhamar, Yemen ( 2001 – 2008). 380 sheep records were studied and analyzed. Average values of mutual mating at birth and weaning of 50% Barri + 50% Tehami were 2.74, 2.59 kg and 11.43, 12.28 kg respectively and were significant (p<0.05) influenced by mutual mating and genetic factors. While for 75% Barri + 75% Tehami, same averages were (2.33, 2.31 kg) and (9.32, 10.9 kg) as compared to pure Tehami sheep (2.21, 8.66 kg). Average daily growth rate from birth to weaning were 123, 122, 107 and 93 g/d/lamb for 50% Barri sheep, 50% Tehami, 75% Barri and 75% Tehami respectively as compared to average weight of pure Tehami breed ( 86 g/d/lamb). Daily growth rate and weight at birth and weaning were influenced significantly (p<0.05) by birth year and season. No effect was observed with season factors. Results revealed that mutual mating between Tehami and Barri for new generation (50% and 75% characteristics) of both breeds improved the average weight at birth, weaning and daily growth rate as compared to pure Tehami breed. No significant effect of genetic factor on twin rate was observed. Finding could be used as a tool for improving the breading management of sheep in study area and other similar geographical regions.

Key Words :Sheep, Barri, Tehami, Reproductivity, Production, Central Highlands