Hormonal induction of ovulation and artificial insemination in suckled beef cows under nutritional stress.
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 (P < 0.05) than those with BCS 3.0 (50 and 66.6%, respectively), but did not differ (P > 0.05) from BCS 2.5 (23.3 and 47.6%). In C group, only 2 of 66 cows were detected in estrus and bred (neither was pregnant). In conclusion, the program for induction of ovulation using MAP, EB, eCG and GnRH increased the pregnancy rate in beef cows in poor body condition, enabling AI to be done in a 63-h interval.
de Medeiros Bastos
Guilherme
G
Laboratory of Biotechnology and Animal Reproduction, Department of Large Animal Clinic, Federal University of Santa Maria, CEP 97105-900, RS, Brazil.
Brenner
Ricardo Heitor
RH
Willke
Fabrício Wollman
FW
Neves
Jairo Pereira
JP
de Oliveira
João Francisco Coelho
JF
Bragança
José Francisco Manta
JF
Machado
Sérgio Abreu
SA
Porciúncula
Patrícia Marafon
PM
Gonçalves
Paulo Bayard Dias
PB
D000282:Administration, Intravaginal; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000833:Animals, Suckling; D001823:Body Composition; D002417:Cattle / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004971:Estrus; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D006728:Hormones / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary*; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage; D010062:Ovulation Induction / Q000662:veterinary*; D011247:Pregnancy; D014886:Weaning
D006063:Chorionic Gonadotropin; D006728:Hormones; C074283:estradiol 3-benzoate; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D017258:Medroxyprogesterone Acetate