PSIII-33 A new approach to resynchronize beef cows and perform two Timed Artificial Inseminations 24 days apart

We aimed to compare the pregnancy rate from 1stTAI and 2ndTAI performed 24 days apart and pregnancy between cows that showed or not estrous on the end of 2nd TAI protocol. Were used 190 lactating cows (Angus: 114; Brangus: 53 and Santa Gertrudis: 23). On the first day of synchronization (D0), insertion of a new CIDR® (Zoetis) plus the 100µg of Cystorrelin®(Merial) treatment, on D7 25mg of Lutalyse® (Zoetis) and CIDR withdrawal. 72 hours after CIDR removal 1stTAI was performed plus GnRH treatment. After 14 days from 1stTAI, all the cows received an one time used CIDR. The pregnancy diagnosis was performed 22 days after 1stTAI, using a subjective visual evaluation of CL blood flow (BF). Pregnancy diagnosis was performed by ultrasonography Color Doppler (MicroMaxx®). Cows with an area of CL≥3cm² and/or ≥25% CL BF were diagnosed as pregnant and underwent CIDR removal without further treatment. Those diagnosed as non-pregnant underwent CIDR removal and received one Estrotect™ (Rockway-Inc.), 25mg of Lutalyse treatment and submitted to 2nd TAI 48h after CIDR removal (D24) plus the 100µg of Cystorrelin. On D31 considered pregnant cows on D22 were examined by US B-mode D31 to verify false positive and effective pregnancies. On D55, cows were submitted to US B-mode to verify the 2ndTAI pregnancy rate. Statistical analysis were performed using GLIMMIX procedure from SAS. The pregnancy on D22 was 48.5% (87/190) and the false positives were 14.9% (13/87). There was no difference on pregnancy 31 days after 1stTAI (38.9%; 74/190) vs. 2nd TAI (32.0%; 33/103; P = 0.24). Cows were more likely to be pregnant on D55 compared to cows that: showed Estrous: 42.9% (21/49) vs. No Estrous: 22.2% (12/54; P = 0.03). In conclusion, the pregnancy rates were the same at 1st to 2ndTAI. And cows that showed estrous had more pregnancy at 2ndTAI.