COMPARISON OF PROTOCOLS FOR TIMED ARTIFICIAL INSEMINATION BY ONE OR TWO ARTIFICIAL INSEMINATIONS AND BY RESYNCHRONIZATION OF OVULATION IN BOS TAURUS INDICUS COWS

Abstract

The goals were to compare the conception rate in cows subjected to timedartificial insemination (TAI) with one AI, two AIs, or resynchronization (RES), and verify the effects of POF (preovulatory follicle) diameter on the CR. Two hundred and seventyfour cows (Bos taurus indicus) were assigned. In the group with one AI (1AIG; n=88), cows were subjected to intravaginal P4 and EB (2mg, IM) on day zero (D0); PGF2α (500μg, IM) on D7; P4 removal on D8; EB on D9; TAI and ultrasonography for POF diameter measurement on D10; PD (pregnancy diagnosis) and natural service on D41; bull removal on D90; and final PD on D110. The same protocol was used in the two AI (2AIG; n=88), except a second AI 20h after the first AI. The resynchronization group (RESG; n=98) was subjected to the same protocol as 1AIG, except a PD was performed on D40, and the non-pregnant cows received the P4 device and EB; PGF2α on D47; P4 removal on D48; EB was administered on D49; TAI was performed on D50; PD was performed, and bulls were introduced on D80; bulls’ removal on D110; final PD on D160. CR of 50, 58, and 73.4% were observed in 1AIG, 2AIG, and RESG, respectively, increasing to 85.2, 88.6, and 87.7% after natural service. The POF diameter at the first TAI was 12.8, 12.1, and 12.7mm in 1AIG, 2AIG, and RESG, respectively, and 12.6mm in RESG and 13.6mm in 2AIG (P=0.031) at the second AI. Groups 1 and 02 inseminations remained with bulls for 49 days and resynchronization for 30 days. In conclusion, RESG yielded a higher CR than TAI with one or two AIs. AI with follicles larger than 12.1mm resulted in a higher CR.