Submitted to: Journal of Animal Science Supplement
Publication Type: Proceedings
Publication Acceptance Date: April 2, 2003
Publication Date: June 22, 2003
Citation: CASAS, E., FREKING, B.A., LEYMASTER, K.A. EVALUATION OF DORSET, FINNSHEEP, ROMANOV, TEXEL, AND MONTADALE BREEDS OF SHEEP: PRODUCTIVITY OF F1 EWES IN FALL BREEDING SEASONS. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. Vol. 81(Suppl. 1):67. 2003. Technical Abstract: Objectives were to estimate effects of sire breed (Dorset, Finnsheep, Romanov, Texel, and Montadale), dam breed (Composite III and northwestern whiteface), mating season (August, October, and December), ewe age (1, 2, and 3 yr), and their interactions on productivity of F1 ewes. A total of 1,799 F1 ewes produced 3,849 litters from 4,804 exposures to Suffolk rams during 35-d mating seasons. Conception rate and ewe longevity were determined. Litter size and weight at birth were recorded and litter size and weight at weaning and 20 wk of age were analyzed separately for dam- and nursery-reared litter mates. Total productivity through 3 yr of age for each ewe entering the breeding flock was calculated as the sum of 20-wk weights for dam- or nursery-reared lambs. Interactions of sire breed x mating season, sire breed x ewe age, and mating season x ewe age were generally significant. Interactions of sire breed x mating season were often due to changes in rank as well as magnitude, indicating the importance of matching sire breeds to specific mating seasons. Litter size at birth of Dorset-, Texel-, and Montadale-sired ewes was not affected by dam breed; however, Finnsheep-sired ewes out of northwestern whiteface dams were more prolific than Finnsheep-sired ewes out of Composite III dams and the opposite situation existed for Romanov-sired ewes. Least-squares means of sire breeds (P < 0.001) for total productivity of dam-reared lambs were 98.5, 103.5, 106.9, 124.6, and 154.9 kg for Texel, Dorset, Montadale, Finnsheep, and Romanov, respectively. Superior productivity of Romanov-sired ewes was due to greater conception rates and litter sizes for each mating season and ewe age, as well as greater ewe longevity. Total productivity of F1 ewes by Composite III dams (125.6 kg) was greater (P < 0.001) than ewes born to northwestern whiteface dams (109.7 kg). Experimental results provide comprehensive information about the appropriate use of these breeds in crossbreeding systems.