Efecto del tratamiento con GnRH en protocolo de sincronización de celo con progestágenos e inseminación artificial a tiempo fijo en vacas en sistema doble propósito.

There is little information on fixed-time artificial insemination protocols (FTAI) in dual-purpose system (DPS) cows in the tropics. The objective of this research was to determine the effect of body condition (CC), time of the year (EA), herd (H) and application of GnRH at the time of IATF on first service gestation (GPS) and total gestation (GT) in VSDP. The study was developed with 433 Bos taurus by Bos indicus bulls in 5 cattle production units (UPP) in the tropical zone of central Veracruz, Mexico. The bellies were selected based on CC and EA, GPS and GT were diagnosed by transrectal palpation at 40 and 90 days of IATF, respectively. The protocol for IATF: day 0 IVD insertion and 2mg estradiol benzoate. Day 8 IVD removal, 25mg prostaglandin f2 ἀ, 1mg estradiol cypionate, 400 IU eCG. Day 10 (48hrs removed DIV) IATF and GnRH (buserelin acetate 0.0008g) and remained in natural mating after IATF. A completely randomized design and a generalized linear model assuming a binomial distribution of the variables gestation rate at first service and total gestation rate were used. The effects of H, E and CC were significant (p<.01). Yes vs. no GnRH affected GPS and GT percentage 0.70 ± 0.07 vs. 0.58 ± 0.09 and 0.82 vs. 0.68, respectively. A higher percentage of GPS was found in dry season than in rainy season 0.69 ± 0.08 vs. 0.58 ± 0.06. Animals with CC 4, 3.5, 3 and 2.5 presented GPS 0.68 ± 0.00, 0.69 ± 0.07, 0.67 ± 0.08 and 0.57 ± 0.07, respectively. It is concluded that applying GnRH at the time of IATF improved GPS and GT in herds with females in body condition 2.5 to 4.