Reproductive performance in Bos indicus and Bos taurus vs. Bos indicus heifers submitted to an ovulation synchronization protocol: influence of breed, progesterone concentration and treatment with equine chorionic gonadotropin

Abstract

The aim of this study is to investigate the influence of progesterone concentrations in combination with eCG administration on reproductive performance between Bos indicus and Bos taurus vs Bos indicus influenced heifers. A total of 1200 heifers (n = 600 Bos indicus and n = 600 Bos indicus x bos taurus) will be used. Ultrasonography will be performed at the beginning of the experiment to access presence of a CL. Heifers containing a CL will be used in the experiment, and will be synchronized as follow: d 0, heifers will receive a new or a third-use CIDR insertion and 2 mg of estradiol benzoate (EB), followed by dinoprost thromethamine (PGF; 12.5 mg) administration on d 7, and CIDR withdrawal concomitant with ECP (0.5 mg) and eCG (0 or 200 IU within CIDR use) administration on d 9. And TAI will be performed on d 11. Heifers without a CL will be treated with the protocol proposed by Rodrigues et al., (2013), being evaluated by ultrasonography 12 days after the end of the induction treatment. Heifers with a CL will be synchronized with the protocol describe above, with the exception of the will be use a third use CIDR and PGF2± at day 9. Blood samples for serum progesterone concentration will be collected at days 9 and 18 and ultrasonography on days 9 and 11 to record the diameter of the largest follicle present on the ovaries. The pregnancy diagnostic will be performed at 30 days of gestation. (AU)