The Effects of Shearing and Level of Feeding on Fertility of Rams

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Abstract
Groups of approximately 20 rams and 80 ewes in 1953 and similar groups in 1954 were each divided as lambs into two lots, one of which received roughage plus grain (a fattening ration) and the other only roughage. All were sheared in April and half of each group of rams was resheared at monthly intervals until breeding was completed. Breeding was from August 20 to October 20, when the sheep were yearlings. Each ram was mated to two ewes from each lot. One of these two ewes was slaughtered at three days and the ova recovered to determine fertilization; the remaining ewe was slaughtered at 40 days to determine embryo survival. In addition, various semen characteristics were studied during the breeding period. The sheared rams had a significantly higher fertilization rate than the unsheared rams. Likewise, a significantly larger proportion of ewes bred to the sheared rams had normal embryos at 40 days of gestation than did those bred to the unsheared rams. No difference in fertilizing ability was found between the rams on the two feeding levels. The sheared rams had significantly lower rectal temperatures than the unsheared groups in both years but the rams which received only a roughage ration had signficantly lower body temperatures only in 1954. No significant relationship was found between various measures of semen quality and fertility in either year though the group with the highest fertility in each year (sheared, roughage-only group) also had the best semen quality each year.

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