Effect of reusing intravaginal progesterone implant on sexual behavior and pregnancy rate in dairy Gir heifers (Bos taurus indicus).

Abstract:

T90
Effect of reusing intravaginal progesterone implant on sexual behavior and pregnancy rate in dairy Gir heifers (Bos taurus indicus).
R. R. Vicentini¹, A. P. Oliveira², R. Veroneze³, A. Ujita⁴, L. El Faro*⁵. ¹Federal University of Juiz de Fora (UFJF) Juiz de Fora, MG, Brazil, ²Agricultural Research Company of Minas Gerais State (EPAMIG Oeste) Uberaba, MG, Brazil, ³Federal University of Vi�osa (UFV) Vi�osa, MG, Brazil, ⁴University of S�o Paulo (FZEA/USP) Pirassununga, SP, Brazil, ⁵Institute of Animal Science (IZ) Sert�ozinho, SP, Brazil.

The reuse of progesterone implants on reproductive protocols may be an alternative to reducing expenditures since it does not affect the reproductive success of females. The aim of the study was to observe the effect of the intravaginal progesterone implant reuse on mating receptivity and pregnancy rate in dairy Gir heifers (Bos taurus indicus) kept on pasture. The experiment was conducted at Campo Experimental Get�lio Vargas of EPAMIG (Agricultural Research Company of Minas Gerais State, Uberaba, Brazil). Fifty-seven heifers were submitted to fixed-time AI (d 0: 2.0 mg of estradiol benzoate + slow-release progesterone implant impregnated with 1 g of P4 + 19 g of excipient, d 7: 0.52 mg of PGF_2α; d 9: Intravaginal implant withdrawal + 1 mg estradiol cypionate + 300 IU equine chorionic gonadotropin; d 11: AI + 2.0 mL of GnRH), divided into 2 treatments. G1 (n = 28) received a first-use intravaginal progesterone implant and G2 (n = 29) received a second-use intravaginal progesterone implant. Every 10 min, during a period of 36 h, the mating receptivity behavior of the heifers was recorded. Observations started 12 h after implant withdrawal (d 9) ending at the time of AI (d 11). Transrectal ultrasound shows that all animals had ovulated. The diagnosis of pregnancy was performed 30 d after AI by ultrasound. Statistical analyses were performed using the SAS. Among the 57 heifers observed, 46 (G1: n = 22; G2: n = 24) expressed mating receptivity behavior; however, no sexual reception behavior was observed for 11 animals (G1: n = 6; G2: n = 5). The length of sexual receptivity was similar between the groups (P > 0.05), which G1 = 7.20 � 4.20 h and G2 = 7.6 � 5.7 h. The non-expression of mating behavior was attributed to the occurrence of silent heat, which can be defined as the occurrence of ovulation with no signs of heat. There was pregnancy rate of 39.28% (n = 11) for G1 and 41.37% (n = 12) for G2, which did not differ statistically (P > 0.05). We concluded that the reusing of the progesterone implants apparently did not affect the sexual behavior and pregnancy rate in dairy Gir heifers.

Keywords: reproduction, reproductive protocol, Zebu cattle.

Biography: Lenira El Faro is Animal Scientist, with MSc in Genetics and Animal Breeding by Paulista State University Julio de Mesquita Filho and DSc in Animal Science by the same institution. Currently, she is a researcher at Institute of Animal Science of S�o Paulo State and professor at the Graduate Program in Sustainable Animal Production of the same institute. Lenira has interest on new phenotypes, dairy cattle, quantitative genetics, genetic evaluation and genetic parameters.