D-cloprostenol and dinoprost tormetamine at the time of artificial insemination in Nelore heifers: luteal dynamics and pregnancy rate

The aim of this study was to evaluate the effect of combining Dinoprost tromethamine and D-cloprostenol in a fixed-time artificial insemination (FTAI) protocol on ovulation, fertility and pregnancy rate in Nelore heifers. A total of 28 Nelore heifers were evaluated. On D0, they received an intravaginal progesterone (P4) device and an intramuscular (IM) injection of 2 mg of oestradiol benzoate (BE). On D7, an application of 2mL of dinoprost tromethamine, on D9 the P4 device was removed and 0.3 mL of oestradiol cypionate (eCP) and 1.5 mL of equine chorionic gonadotrophin (eCG) were administered, on D11 all the females were inseminated and randomly divided into three groups: T1, T2 and T3. The control (T1; n = 8), in which the animals received 2 mL of saline IM; T2 (n = 11), received 2 mL of dinoprost tromethamine IM; and T3 (n = 9), received 2 mL of D-Cloprostenol IM. Follicle diameter was assessed on D0, D7, D9, D11 and corpus luteum (CL) diameter on D12. Gestation diagnosis (GD) was carried out 30 days after artificial insemination (AI). Non-parametric variables were analyzed using the Friedman test, with a significance level of 5%. The pregnancy rate was different between treatments (p < 0.05), being higher in T3 when compared to T1 (55.55%) vs. (12.5%), as well as T2 (55.55%) vs. (27.27%). There was no interaction between treatments in terms of follicle diameter at D11 and CL formation. It was concluded that the use of two doses of PGF2α (dinoprost tromethamine and D-cloprostenol) was efficient in synchronizing small follicles (< 10mm) and increasing pregnancy rates.