Eficiência reprodutiva de fêmeas nelore ressincronizadas 22 dias após a inseminação artificial em tempo fixo (IATF)

Abstract

This work aimed to evaluate the reproductive efficiency of Nellore females in a resynchronization program with fixed-time artificial insemination (FTAI). In this experiment, 195 animals of different categories of the Nelore breed were evaluated. The animals were kept on pasture (Brachiaria sp.) feeding, receiving mineral supplementation and water ad libitum and the inclusion criterion adopted was pubescent heifers and calving females at least 45 days old. On day 0 (D0) an intravaginal device impregnated with 0.5 g of progesterone (P4) (DIB®, Zoetis) was introduced and 2 mg of estradiol benzoate (EB) (Bioestrogen®, Biogénesis Bagó) was applied intramuscularly (IM). After 8 days (D8) the device (P4) was removed and 2.5 mg of prostaglandin (PGF2α) (Lutalyse®, Zoetis), 300UI of equine chorionic gonadotropin (eCG) (ECEGON®, Biogénesis Bagó) and 0.4 mg of estradiol cypionate (E.C.P. ®, Zoetis). The animals were inseminated between 48 and 54 hours after removal of the intravaginal device (P4). On the 22nd day after insemination, a new (FTAI) protocol was started in all females without a previous diagnosis of pregnancy, with the introduction of the device (P4) and application of 1 mg of (BE). On the 30th day (D30) the diagnosis of transrectal pregnancy was performed (US; Mindray, DP-50 Vet, 5MHz transrectal linear transducer) and device removal (P4) was performed in all animals. The animals that did not confirm pregnancy received 2.5 mg of (PGF2α), 300UI of (eCG) and 0.4 mg of (EC) intramuscularly and were inseminated again between 48 and 54 hours. The same protocol was followed for the second resynchronization. On the 15th day after the 3rd FTAI, the animals were transferred to the bull and remained there for 60 days. The pregnancy rate in the first (FTAI) was 39,6%, first resynchronization 44,4%, second resynchronization 40,7%, with accumulated (FTAI) of 79,2%, closing the EM with 95.3% pregnancy with TAI + Taurus.