Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 23, 2004
Publication Date: July 1, 2004
Citation: Leymaster, K.A., Casas, E., Freking, B.A. 2004. Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: Reproduction of F1 ewes in spring mating seasons. [abstract] Journal of Animal Science Supplement. 82(Suppl. 1):390. Paper No. 647. 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 (March and May), ewe age (4, 5, and 6 yr) and their interactions on reproductive traits of F1 ewes. A total of 1,099 F1 ewes produced 1,754 litters from 2,330 exposures to Suffolk rams during 42-d mating seasons. 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 lambs. Total productivity from 4 to 6 yr of age for each ewe entering the breeding flock was calculated as the sum of 20-wk weights for dam-reared lambs. Interactions of sire breed x mating season, ewe age x mating season, and ewe age x dam breed were often significant. Interaction of sire breed x dam breed on conception rate (P < 0.01) was due to change in rank as well as magnitude. Averaged over mating seasons, Romanov x Composite III ewes had the greatest conception rate (93%) and Montadale x Composite III the lowest (64%). Interactive effects of sire breed and mating season on conception rate (P < 0.001) were due to differences in magnitude, with Romanov-sired ewes being most consistent between seasons (92% in March and 89% in May). Sire breed affected litter size at all ages (P < 0.001), ranging from 1.40 lambs at birth for Texel to 2.09 for Romanov. Differences between dam breeds in total productivity of dam-reared lambs were not detected, whereas ewes exposed in March (78 kg) were more productive (P < 0.01) than May (68 kg). Means of sire breeds for total productivity were 47, 65, 70, 70, and 111 kg for Texel, Montadale, Dorset, Finnsheep, and Romanov, respectively (P < 0.001). Superior reproduction of Romanov-sired ewes was due to greater conception rate and prolificacy at each mating season and ewe age. Use of Romanov crossbred ewes would increase fertility during spring mating, an important constraint of the sheep industry.