Comparison of Dorper and Polypay as maternal sire breeds for reduced input lamb production Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cz30pw861

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  • During years 2005, 2006, and 2007 ewes of predominantly Polypay breeding were bred to either Dorper or Polypay rams for spring lambing. Ewes were assigned to single-sire mating groups based on age and genotype. Internally generated replacements were added to the flock for the 2007 lambing season and bred to rams within their own sire breed. Litter size was recorded for ewes and lambs were weighed at birth and weaning. Inventory at weaning was used to determine lamb survival. Internally generated replacement females were weighed at approximately one year of age. Dorpermated ewes gave birth to 0.14 more lambs than Polypay-mated ewes, suggesting a ram breed effect on litter size (p <.10). Polypay-sired internally generated replacement females had a mean litter size of 0.30 lambs greater than Dorper-sired generated ewes did (p <.05). Polypay-sired lambs were significantly heavier than Dorper-sired lambs at birth (0.2 kg, p <.05), but similiar in terms of mean weaning weight. No significant difference in lamb survival was observed between the two sire breeds. Polypay-sired replacement females were slightly heavier (2.9 kg) than Dorper-sired replacements as yearlings (p <.10). Due to their advantage in litter size, Polypay-sired females would be expected to generate more profit for commercial sheep producers than would Dorper-sired ewes. Dorpers would still remain a viable ram breed for commercial production in Western Oregon due to their comparable growth rates assuming lamb pelt quality could be maintained through selective breeding.
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