Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 2/14/2007
Publication Date: 7/10/2007
Citation: Leymaster, K.A. 2007. Evaluation of Dorper, Dorset, Katahdin, and Rambouillet crossbred ewes in high- and low-input production systems [abstract]. Journal of Animal Science. 85 (Supplement 1):458-459. Abstract #671.
Technical Abstract: The primary objective was to evaluate wool (Dorset, Rambouillet) and hair (Dorper, Katahdin) dam breeds for their ability to complement Romanov germplasm as crossbred ewes managed in distinct production systems. Romanov ewes were mated with 18 rams of each dam breed to produce crossbred ewes for evaluation through 3 yr of age in two production systems. In the high-input system, labor and harvested feed were provided for sheep in confinement facilities and ewes were limited to rearing two lambs with additional lambs reared artificially. Ewes in the low-input system lambed on pasture and were responsible for rearing all lambs. No labor or supplemental feed were provided before weaning. A total of 830 crossbred ewes produced 1,962 litters and 5,311 lambs from 2,172 multisire exposures to two terminal sire breeds (Suffolk, Texel). Fertility rate (FR), number born (NB), lamb losses between birth and 24 wk (LOSS), number at 24 wk (N24), and 24-wk litter weight (LTRWT) were analyzed as a trait of the ewe. Effects of year of birth, dam breed, production system, sire breed, ewe age and their two-way interactions were estimated. Random effects of sires of crossbred ewes and repeated effects of ewes across ages were fitted. Ewe age affected all traits and often interacted with dam breed and production system (P < 0.05). The interaction of dam breed x sire breed on FR (P < 0.05) was due to change in rank as well as magnitude. Suffolk-sired litters had greater LOSS and lesser N24 than litters by Texel rams (P < 0.05). Interactions of dam breed with production system were not detected. The high-input system had greater (P < 0.05) values than the low-input system for NB, N24, and LTRWT24 and approached significance for FERT and LOSS. Main effects of dam breed were detected (P < 0.05) only for NB and N24, with Katahdin crossbred ewes producing the most lambs, followed by Dorset and Dorper and then Rambouillet. Other key traits need to be considered before use of these dam breeds is recommended.