PROBLEMS OF SEXUAL CYCLICITY AND FERTILIZATION OF HEIFERS AND COWS
In long-term experiments on 5080 heifers and 8700 cows of dairy breeds, they studied the usefulness of sexual cycles and the fertility of animals. In experiments on 60 heifers, it was found that the average duration of heat is 49–51 hours, and of sexual hunt – 12.3 hours with natural pairing of heifers, 12.8 hours – using a bull-probe and 14.2 hours – with artificial insemination. Ovulation took place 10–12.3–14.9 hours after the end of the hunt, respectively, and the fertilization rate from the first insemination was 86.3–79.0–73.7%.
Under the conditions of farms, the fertility of heifers was within 64.5–77.6%. Younger heifers fertilized better when they reached a live weight of 350 kg. 83% of heifers had full sexual cycles, and metrorrhagia was found in 25% of animals.
In cows 77% of animals had complete sexual cycles and the fertilization rate from the first insemination was 48–61%. Metrorrhagia was recorded in 29% of cows with hypofunctional processes in the uterus and ovaries.
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