Progestogen Treatment in Relation to Time of Insemination and its Effect on the Breeding Efficiency of Dairy Cows

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Abstract
The effect of routine therapy with 500 mg of 17-a-hydroxyprogesterone-17-n-caproate (PC) alone or in combination with 0.5 mg of estradiol valerate (PC + EV), on breeding efficiency was determined with 594 Holstein and 282 Guernsey female reproductive cycles. In three controlled trials the drug was injected intramuscularly at 0, 2, 10, or 14 days after artificial insemination on the first and (if necessary) the second insemination during a reproductive cycle. When PC was administered at zero day, breeding efficiency values were 20.7% lower for Holsteins and 13.5% lower for Guernseys than for the controls. When PC was administered 2 days after insemination, the breeding efficiency of the Holsteins was almost equal (3.1% lower) to that of the controls, though it was markedly lower (15%) for the Guernseys. Such early treatments showed a detrimental effect on breeding efficiency. When PC was administered alone or in combination with EV at 10 days to both breeds and at 14 days to Holsteins only, breeding efficiency values were only slightly below those of the control groups, except for the PC + EV group treated at 10 days, in which the Holsteins averaged 17.7% below their controls. No beneficial effects were observed in any of the treatment groups. Other comparative analyses of the data revealed no conclusive evidence that the treatments were causing prolonged injurious effects on the reproductive system.