Timed artificial insemination in crossbred mares: Reproductive efficiency and costs

Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF_2α ) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycles). The CAIG was subjected to CAI, involving follicular dynamics and uterine oedema monitoring with ultrasound examinations (US), and administration of hCG (1,600 IU) when the dominant follicle (DF) diameter's ≥35 mm + uterine oedema + cervix opening. The AI was performed with fresh semen (500 × 10⁶ cells), and embryo was recovered on day 8 (D8) after ovulation. In TAI, mares received 1.9 g PRID on D0. On D10, PRID was removed and 6.71 mg dinoprost tromethamine was administered. Ovulation was induced on D14 (1,600 IU of hCG) regardless of the DF diameter's, and AI was performed with fresh semen (500 × 10⁶ cells). On D30 after AI, pregnancy was confirmed by US. The pregnancy rate was 80.0% in TAIG and 82.3% in CAIG (p > .05). The TAI protocol resulted in 65% reduction in professional transport costs, and 40% reduction in material costs. The TAI was as efficient as CAI, provided reduction in costs and handlings, and is recommended in mares.