Hormonal induction of ovulation and artificial insemination in suckled beef cows under nutritional stress

Theriogenology
Guilherme de Medeiros BastosPaulo Bayard Gonçalves

Abstract

The objective was to develop a program for inducing estrus (followed by insemination) of suckled beef cows under nutritional stress (poor body condition). A total of 123 cows, from 60 to 75 days postpartum, were classified according to their body condition score (BCS; range from 1 to 5, in increments of 0.5) and allocated into two groups. On Day 0 (without regard to stage of the estrous cycle), cows (n = 59) in the hormone induction (HI) treatment group were given an intravaginal device (IVD) containing 250 mg of medroxiprogesterone acetate (MAP) and an i.m. injection of 2.5 mg estradiol benzoate (EB). On Day 6, these cows were given 500 IU eCG i.m. and calves were weaned for 96 h. The IVD were removed on Day 7. Cows detected in estrus by 45 h after IVD removal were inseminated 12 h after standing estrus; cows not in estrus by 45 h after IVD removal received an i.m. injection of 100 microg gonadorelin (GnRH) and were inseminated 16-18 h later. In the control group (C), cows (n = 64) only had their calves weaned at Day 6 (for 96 h), with estrus detection and AI from Days 6 to 11. Overall, the BCS ranged from 2.0 to 3.0. In the treatment group, estrus and pregnancy rates in cows with BCS 2.0 (20 and 30%, respectively) was lower (...Continue Reading

References

Jun 23, 1984·The Veterinary Record·O M Kerr, W J McCaughey
Jul 1, 1983·Journal of Reproduction and Fertility·C BernardR D Lambert
Apr 1, 1993·Domestic Animal Endocrinology·M L DayW F Pope
Sep 16, 2000·Theriogenology·Y Yavas, J S Walton
Sep 16, 2000·Theriogenology·Y Yavas, J S Walton
Aug 22, 2001·Biology of Reproduction·J E FortuneA M Turzillo

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