Fixed-time artificial insemination and reinsemination of beef cows treated with and without equine chorionic gonadotropin
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beef cattle
reproductive efficiency
gestation rate
artificial insemination
meat bovinos para carne
eficiencia reproductiva
tasa de gestación
inseminación artificial

How to Cite

Espinoza Villavicencio, J. L., Palacios-Espinosa, A., Ortega-Pérez, R., Guillén-Trujillo, A., & Manríquez-Hirales, E. (2021). Fixed-time artificial insemination and reinsemination of beef cows treated with and without equine chorionic gonadotropin. Nova Scientia, 13(27).


Introduction: the objectives were to evaluate estrus and gestation in Bos taurus cows, treated with a fixed-time artificial insemination protocol (FTAI) that included or not equine chorionic gonadotropin (eCG). Cumulative gestation with resynchronization at 30 days after the first FTAI was also evaluated.

Method: the cows were divided into: Treatment 1 (n = 60), synchronized with 2 mg of estradiol benzoate and an intravaginal device (IVD) of progesterone (1.3 g) on ​​day 0; IVD was removed on day 8 and 25 mg of prostaglandin F2-alpha, 1 mg of estradiol cypionate and 300 IU of eCG were injected; 48-52 hours later the FTAI was performed. Treatment 2 (n = 50) consisted in the same protocol, not including eCG. Ovulation was resynchronized in cows that were no pregnant in the pregnancy diagnosis, performed 30 days after the first FTAI. The same protocol applied in Treatment 1 for the first FTAI was used in all animals. The second FTAI was performed 40 days after starting the program. Body condition score (BCS) was classified as low (< 2.5), moderate (2.5 to 3.5) and high (> 3.5). On the day of the FTAI, the preovulatory follicle diameter (DFP) was classified into three categories (DFP1: < 11 mm; DFP2: 11 to 14 mm; DFP3: > 14 mm).

Results: the gestation percentage was different between treatments (p = 0.04; 73 % Group 1 and 53 % Group 2). The proportion of cows in estrus before the FTAI was 75 % in the eCG treatment and 57 % in the control (p = 0.04). Cows with DFP2 and DFP3 registered a higher gestation rate (p = 0.03) than DFP1. The percentage of pregnancies was higher (p = 0.04) in cows with moderate and high BCS. Overall gestation in the first FTAI was 63  %. The gestation percentage with the second FTAI was 51.61 %, accumulating 82.1 % in 40 days.

Conclusion: eCG increased the proportion of cows in estrus and gestation; and resynchronization allows the accumulation of an additional percentage of pregnant cows.
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