Submitted to: The Shepherd
Publication Type: Popular Publication
Publication Acceptance Date: 8/12/2005
Publication Date: 9/14/2005
Citation: Leymaster, K.A., Freking, B.A., Casas, E. 2005. Experimental results to take to the bank. The Shepherd. 50(9):11-14.
Technical Abstract: Objectives were to estimate effects of sire breed (Romanov, Finnsheep, Dorset, Texel, and Montadale) on survival, growth, and carcass traits of crossbred lambs and on reproductive traits of 1-, 2-, and 3-year-old crossbred ewes in fall breeding seasons (August, October, and December ) and of 4-, 5-, and 6-year-old crossbred ewes in spring breeding seasons (March and May). A total of 102 purebred rams of the five breeds produced 4,320 crossbred lambs. A total of 1,799 crossbred ewes produced 5,603 litters and 9,697 lambs. Romanov and Finnsheep crossbred lambs had higher survival to weaning than crossbred lambs by Dorset, Texel, and Montadale, whereas differences among all crossbred types in weight at 20 weeks of age were slight. When compared at a common carcass weight of 63 pounds, Romanov and Finnsheep crossbred lambs had lower dressing percentages than other crossbreds. Crossbred lambs by Dorset and Montadale had the least fat depth at the 12th rib and the longest carcasses. Carcasses of Texel crossbred lambs were most compact, being shortest in length and having the largest rib-eye area. Finnsheep crossbred lambs had the smallest rib-eye area, followed by Romanov crossbred lambs. Crossbred ewes by Dorset and Montadale were the heaviest at three years of age and ewes of the other crossbred types were similar in weight. The percentage of ewes lambing after fall mating fell into four groups: Romanov crossbred ewes had the highest percentage lambing, followed by Finnsheep, then Texel and Dorset, and crossbred ewes by Montadale were lowest. As expected, crossbred ewes by Romanov and Finnsheep produced the greatest number born per ewe lambing. Romanov crossbred ewes had the heaviest litters at 20 weeks of age per ewe lambing for both dam- and nursery-reared lambs, followed by Finnsheep, then Dorset and Montadale, and finally Texel. Romanov and Montadale crossbred ewes stayed in the flock at a higher rate than crossbred ewes by Finnsheep, Dorset, and Texel. Differences among crossbred types in percentage of ewes lambing after spring mating were significant. In March breeding, percentage lambing was 92% for crossbred ewes by Romanov, 91% for Finnsheep, 90% for Texel, 88% for Montadale, and 83% for Dorset. In May breeding, a more challenging month, percentage lambing was 89% for Romanov, 72% for Finnsheep, 62% for Dorset, and 52% for both Texel and Montadale. The 20-week litter weight of dam-reared lambs per ewe lambing was heaviest for crossbred ewes by Romanov, intermediate for Finnsheep, Dorset, and Montadale, and lowest for Texel. Romanov and Finnsheep crossbred ewes produced the heaviest litters of nursery-reared lambs. These experimental results provide conclusive information about the appropriate use of these five breeds in terminal crossbreeding systems. Rams of the Texel breed should be used as terminal sires to complement characteristics of crossbred ewes. Dorset and Montadale may best be used to cross with prolific breeds to make crossbred ewes. Romanov and Finnsheep should provide the reproductive foundation for maternal lines used in terminal crossbreeding systems. Romanov crossbreds had superior performance for lamb survival, percentage of ewes lambing, number born, and length of seasonal breeding. We strongly recommend greater industry use of Romanov crossbred ewes as maternal lines in terminal crossbreeding systems, especially for annual or accelerated production systems that breed in the spring.