Select Synch and Co-Synch protocols using a CIDR yield similar pregnancy rates after a fixed-time insemination in suckled Bos indicus × Bos taurus cows.

Primiparous and multiparous suckled Bos indicus × Bos taurus cows were used to compare a Select Synch + controlled internal drug release (CIDR) and timed artificial insemination (AI) protocol (SSC) to a modified CO-Synch + CIDR protocol (COS). Five separate groups of cows were utilized (n = 659) and within a group, cows were allotted to two treatments on the basis of body condition score (BCS) taken 10 days before and days postpartum at CIDR insertion (Day 0). Blood samples were collected on Day -10 and 0 for assessment of circulating concentrations of progesterone to determine estrous cycling status.

Evaluation of two progestogen-based estrous synchronization protocols in yearling heifers of Bos indicus × Bos taurus breeding.

Yearling Bos indicus × Bos taurus heifers (n = 410) from three locations, were synchronized with either the Select Synch/CIDR+timed-AI (SSC+TAI) or 7-11+timed-AI (7-11+TAI) treatments. On Day 0 of the experiment, within each location, heifers were equally distributed to treatments by reproductive tract score (RTS; Scale 1-5: 1 = immature, 5 = estrous cycling) and body condition score. The 7-11+TAI treatment consisted of melengestrol acetate (0.