Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 7, 2000
Publication Date: June 1, 2000
Citation: Freking, B.A., Leymaster, K.A., Young, L.D. 2000. Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: I. Effects of ram breed on productivity of ewes of two crossbred populations. Journal of Animal Science. 78:1422-1429. Interpretive Summary: Differences among breeds of sheep in performance for economically important traits are genetically based and can be exploited through strategic use in crossbreeding systems. This study comparing Dorset, Finnsheep, Romanov, Texel, and Montadale provides information to help producers identify breeds or create new composite populations that meet targeted levels of performance for specific production-marketing situations. In general, differences between these breeds of ram on traits recorded to weaning were consistent regardless of breed of ewe, except for conception rate. When penned with ewes of two breeds, Romanov rams preferentially mated with ewes of the Composite III breed compared to northwestern whiteface. Effects of breeds of ram and ewe on number born and litter birth weight depend on the season of mating. Therefore, it is important to use genetic resources in appropriate mating seasons if performance is to be optimized. Ewes giving birth to Romanov-sired litters produced more lambs at birth with greater survival to weaning.
Technical Abstract: Effects of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds for performance as sires were estimated. The objectives were to evaluate the effects of ram breed, ewe breed, season of mating, and the two-way interactions. Rams were single-sire mated with ewes from two crossbred populations to produce lambs over a 3-yr period. Ewes were assigned to one of three distinct 35-d mating seasons initiated each year in August, October, and December. A different sample of six rams per breed was used each yr across all three seasons, with each ram penned with ewes of both breeds. Traits evaluated and number of ewe records were: conception rate and litter weaning weight per ewe exposed (n=3,261); number born, litter birth weight, average birth weight, number weaned, and litter weaning weight of ewes lambing (n=2,751). Ram and ewe breeds interacted (P<.01) for conception rate and litter weaning weight per ewe exposed, implicating mating preferences of Romanov rams. Effects of ram breed on number born an litter birth weight interacted (P<.05) with season. The largest litters within each ram breed were associated with the October mating season. Breed of ram differences affected per ewe lambing productivity measurements (P<.01). Differences between ram breeds for ewe productivity were noted with increased number born and improved survival of crossbred progeny to weaning for Romanov-sired litters. On a per ewe exposed basis, Romanov- sired litters produced either the largest or the smallest values for litter weaning weight depending on the breed of ewe. These experimental results have inference to these ram breeds when used as sires in different crossbreeding systems. Structured mating systems involving these breeds could be used to target a specific production situation.