Use of equine chorionic gonadotrophin in heifers embryo receptors to evaluate the increment of endogenous progesterone in the inovulation day in relation to pregnancy rate

Abstract

The experiment was carried out to evaluate the influence of pregnant Mare Serum Gonadotrophin (eCG) administration in embryo receptors on the formation of accessory corpus luteum and correlation with the pregnancy rate. Sixty-four beef cattle heifers -18 to 30 months old were used, ½ Simental, with 400 kg of average live weight. The heifers were evaluated through rectal palpation between days 7 to 12 after heat detection, considered as heat base. In this interval from 7 to 12 days after the heat, defined as zero day (D0), the animals identified with physiological corpus luteum were divided in four treatments. The animals in treatment 1 (control, n=21) received physiologic solution intramuscle (IM); in treatment 2 (n=16) received 200 IU of eCG (FOLLIGON - Intervet), IM; in treatment 3 (n=14) received 400 IU of eCG IM; and in treatment 4 (n=13) received 600 IU of eCG IM. Two days after (D2) eCG application all the animals received 2.0 mL of prostaglandin F2 alpha (PROSOLVIN - Intervet). Following, the animals' heat manifestation was observed, and, seven days after heat detection, the animals were evaluated for ultrasonography to select females able to receive frozen embryos. Twenty-three days after inovulation, the pregnancy diagnostic was detected through ultrasonography. There was no statistic difference (p > 0.05) for pregnancy rate. These results show that eCG used in receptors of frozen embryos neither improved the receptors' performance rate, nor the pregnancy rate.