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The effects of maedi-visna virus infection on productivity in ewes |
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| Authors: | I. R. Dohoo D. P. Heaney R. G. Stevenson B. S. Samagh C. S. Rhodes |
| Affiliation: | 1 Animal Pathology Division, Agriculture Canada, 2255 Carling Avenue, Ottawa, Ontario, K1A 0Y9, Canada 2 Animal Research Centre, Agriculture Canada, Ottawa, Ontario K1A 0C6, Canada 3 Animal Pathology Laboratory, Agriculture Canada, Sackville, New Brunswick, Canada 4 Animal Disease Research Institute, Agriculture Canada, Ottawa, Ontario, Canada 5 Department of Herd Medicine and Therlogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada |
| Abstract: | A total of five data sets obtained from four separate sheep flocks were used to evaluate the effects of subclinical maedi-visna virus infection (as determined by serological procedures) on productivity in ewes. In general, infection with maedi-visna virus had a detrimental effect on productivity. Infection resulted in a reduction in conception rates, with the odds of an infected ewe conceiving being only approximately 0.67 times those of a non-infected ewe. For ewes which did conceive, there was no detrimental effect of infection on the number of lambs born. The birth weights of lambs born to middle-aged (3–4 years) infected ewes were 3–6% lower than the weights of lambs born to non-infected ewes of the same age. There was very little apparent effect of infection in younger (1–2 years) and older (5 + years) ewes: some factors which may have biased these results are discussed. Lamb weights at 25–50 days of age appeared to be reduced by maedi-visna infection in the ewe but the results were not statistically significant. |
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