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National Council for Scientific Research, Zambia,2
Abstract
The estrous cycles of 40 ranch cows, maintained under two planes of nutrition, were studied for a full calendar year. Of the animals on the low plane of nutrition (LP), 55% had stopped cycling by the end of the experimental period. The incidence of silent ovulation in the LP group was significantly higher than in the group of animals under normal plane of nutrition (NP). No seasonal effects were observed on either the length of the estrous cycle or estrous period in the NP group.
When a group of 34 heifers were compared to NP cows, it was found that the duration of estrus in heifers was shorter (P<.05).
1 The authors are indepted to Mr. D. K. Dutta-Roy, for the statistical analysis and to Messrs. Y. Kapyanga and the late J. Nguluwe for their technical assistance.
2 Physiology Laboratories. P.O. Box 49, Chilanga, Via Lusaka, Zambia.
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