The aim of this study was to evaluate the efficiency of artificial insemination (AI) services in Holstein x Brahman cows under a heat induction programme. Three experiments were carried out. In Exp. 1, a retrospective analysis of the efficiency of AI insemination of 41 000 cows treated with the combination of progesterone and oestradiol benzoate or equine chorionic gonadotropin (eCG) was carried out. In Exp. 2 it was evaluated 863 cows inseminated after heat induced with progesterone and oestradiol benzoate to know the physiological events that occur before and after service in herds with a high incidence of anoestrus. Gynaecological examinations and determination of progesterone in milk were performed. The purpose of Exp. 3 was to improve the effectiveness of AI services for cows in postpartum anoestrus treated with progesterone and oestradiol benzoate combined with a technique to iden...

El estudio se realizó durante seis meses en un rebaño de 5817 vacas hipocuprémicas (<10.0 µmol/L de cobre en suero sanguíneo) en anestro. Los animales fueron distribuidos en cuatro grupos: Grupo I (n=2984): se indujo el celo con aplicación de progesterona y benzoato de estradiol siguiendo el esquema de administración de progesterona en dosis de 60, 90 y 90 mg vía IM a intervalos de 48 h seguido de 1 mg de benzoato de estradiol 48 h más tarde e inseminadas a las 48 y 56 h del tratamiento; Grupo II (n=1314), tratado como el Grupo I. pero se suplementó con una inyección subcutánea de cobre (50 mg); Grupo III (n=1070), solo recibió el suplemento de cobre; Grupo IV: (n=449) control, sin tratamiento hormonal ni suplemento de cobre. Los grupos suplementados con cobre presentaron niveles normales del mineral al término del estudio; asimismo, presentaron tasas de preñez de 24.5%...

The objective of this research was to determine the effect of Estradiol Cypionate (ECP), at the time of withdrawal of the Progesterone vaginal device or Estradiol Benzoate (EB), 24 hours later on the pregnancy rate in heifers inseminated at fixed time (FTAI). Seventy-two Bos indicus x Bos taurus crossbred heifers of body condition 3.0 to 3.5 (Scale 1 to 5), body weight between 300 to 400 kg were selected. The animals were divided into three groups A, B and C. All animals were synchronized to estrus using EB + Progesterone (DIB 0.5) + Prostaglandin F2-Alpha. Ovulation was induced by administering 0.5 and 1 milligram estradiol cypionate to groups A and B on day zero when the progesterone vaginal device was removed. To group C, 1 milligram of Estradiol Benzoate was administered 24 hours after the end of progesterone treatment. The administration of ECP at a dose of 0.5 milligram, showed the...