Effects of ewe breed and management system on efficiency of lamb production: I. Ewe productivity.
Performance of 1/2-Suffolk, 1/2-Rambouillet (Western) and 1/2-Suffolk, 1/4-Rambouillet, 1/4-Finnsheep (1/4-Finn) ewes was compared in three different lamb production systems over 3 yr. System 1 (56 ewes) involved late fall lambing over 84 d. System 2 (51 ewes) involved January and February lambing for 60 d. System 3 (47 ewes) involved March and April lambing for 45 d. Pregnancy rates for yearling ewes were lower in System 1 in yr 1 (50.7% vs 87.4% for Systems 2 and 3) but differed little among systems for older ewes or in remaining years. Average pregnancy rates for 2-yr-old and older ewes were 89.5, 94.0 and 85.7% for Systems 1, 2 and 3, respectively. When the pregnancy rate was adjusted to a 45-d lambing season, means for older ewes were 78.6, 89.5 and 85.7% for System 1, 2 and 3, respectively. Ewe breeds did not differ in their pregnancy rates. Prolificacy (lambs born per ewe lambing) was higher for 1/4-Finn ewes (1.83 +/- .06 vs 1.55 +/- .07) and was higher in System 3 (1.86 +/- .06) than in Systems 1 (1.60 +/- .07) or 2 (1.63 +/- .05). Body weight at breeding in postyearling ewes was less in System 3 (64.3 kg); than in Systems 1 or 2 (average of 73.1 kg). Breeds did not differ in weight at 1 or 2 yr of age, but Western ewes were 2.1 +/- 1.1 kg heavier as 3-yr-olds.(ABSTRACT TRUNCATED AT 250 WORDS)
Notter
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Dept. of Anim. Sci., Virginia Polytechnic Institute and State University, Blacksburg 24061.
McClaugherty
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D000822:Animal Husbandry; D000818:Animals; D001835:Body Weight; D001947:Breeding; D005260:Female; D005298:Fertility; D016018:Least-Squares Analysis; D011897:Random Allocation; D012621:Seasons; D012756:Sheep / Q000235:genetics / Q000502:physiology*; D014935:Wool / Q000254:growth & development