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Evaluation of Luteolysis and Estrous Synchronization by a Prostaglandin Analog (Luprostiol) in Brahman Cows and Heifers^1,2,3,4,

Texas A&M University Agricultural Research and Extension Center, Overton 75684

Abstract

A trial was conducted to evaluate the ability of a prostaglandin analog, Luprostiol (LP), to synchronize estrus in Brahman cows and heifers. Animals were injected with either 0, 3.75, 7.5, 15 or 30 mg LP or 500 µg cloprostenol (CLP) on d 8 or 9 after estrus (d 0). All concentrations of LP (>0 mg) and CLP caused luteolysis in cows and heifers, as indicated by a decline (P < .01) in serum progesterone concentration after injection. Animals receiving 0 or 3.75 mg LP had a longer (P < .04) interval to estrus after injection than did animals in other treatment groups. The proportion of animals exhibiting estrus by 120 h after injection was influenced by dose of LP (P < .0001; 0, 3.75 mg < 7.5, 15 and 30 mg and CLP) but not by age. Cows had a lower (P < .01) progesterone concentration than heifers on d 10, 11 and 12 after LP-induced estrus. Progesterone concentration was lowest (P < .01) on d 10, 11 and 12 after LP-induced estrus in cows given 15 mg LP or CLP. First-service conception rate was similar between cows and heifers, but it was lower (P < .01) in animals given 15 or 30 mg LP. Both estrogen and LH concentrations were decreased (P < .01) at the time of estrus by the 15 and 30 mg of LP. Luprostiol can cause luteolysis and estrous synchrony in Brahman cattle. Because the higher doses of LP (15 and 30 mg) suppress subsequent corpus luteum function and fertility, 7.5 mg LP is the appropriate dose for use in Brahman cows and heifers.

¹ Journal Paper TA 23972, Texas Agric. Exp. Sta.

² This study was a contribution to the Western Regional Research Project W-112, Reproductive Performance in Domestic Ruminants.

³ This study was supported in part by a grant from Norden Laboratories, Inc., Lincoln, NE.

⁴ The authors wish to thank D. J. Bolt, USDA-ARS, Beltsville, for supplying standards and antisera for the FSH assays, and J. J. Reeves, Washington State Univ., Pullman, for supplying LH antisera.

⁵ Present address: Cincinnati Zoo and Botanical Garden, Cincinnati, OH 45220.