Compared DIB monodose and CIDR in pregnancy rate early Nelore heifers submitted to TAI

Introduction Nelore heifers at breeding at 14 months of age has become a strategy to increase productivity on cow/calves farms in Brazil. Some factors such as weight, genetics, cyclicity and the type of protocol can affect results. This study aimed to evaluate the pregnancy rate in early Nelore heifers will TAI synchronized with different devices progesterone (P4). The studies were conducted in three different farms (A, B and C) in the state of Mato Grosso, totaling 860 heifers with an average age of 15.1 ± 2.1 months. All animals were previously induced into cyclicity device with P4 and then TAI (Rodrigues, 2014). In D0 protocol heifers were randomized to receive the following treatments: 1) CIDR: CIDR 1st use; 2)CIDR4: 3rd or 4th CIDR use; 3)DIB0,5N: DIB0,5 and 4)DIB0,5 DIB0,5 (Zoetis, SP, Brazil), plus 2.0 mg of estradiol benzoate im (2.0 ml Gonadiol®, Zoetis, SP, Brazil) in; D7 in the administration of 12.5 mg im PGF2a (2.5 mL Lutalyse®, Zoetis, SP, Brazil); D9 removal of the device with application of 0.5 mg of cypionate im estradiol (0.3 mL ECP®, Zoetis, SP, Brazil) and 1.0ml of Novormon (200IU of eCG, Novromon, Zoetis, Brazil) in treatments CIDR1 and DIB0,5N only; IA at the D11. On the farm C the heifers were treated in resynchronization (2aIATF). Cyclicity was evaluated in heifers 472 12 days after induction/begin TAI protocol, where 54,0% had CL presence on ultrasound. Pregnancy diagnosis was confirmed 30 days after TAI. Pregnancy/IA (P/AI) was determined by dividing the number of pregnant cows for the total inseminated cows. Random variables were analyzed with PROC GLIMMIX the SAS program. Interactions with P > 0.2 were removals the initial model. There were no interactions between farms, lots, bulls or inseminator in P/IA. There was no interaction between cyclicity and treatments on P/AI heifers with presence of CL had similar pregnancy than without CL (39.2% 85/217, 91/255 35.7%, respectively).The P/IA in heifers treatments CIDR1, CIDR3 and DIB0,5N (78/214:36.4%, 84/125:39.0% and 61/208:44.3%, respectively) were similar and higher than in treatment DIB0,5 (61/208:29.3%). It follows that the early P/IA in Nelore heifers synchronized with DIB0,5 or CIDR are similar, however synchronization with new P4 devices requires the addition of eCG to the protocol.