Evaluation of reproductive and economic outcomes of dairy heifers inseminated at induced estrus or at fixed time after a 5-day or 7-day progesterone insert-based ovulation synchronization protocol

The objectives of the current experiment were to evaluate the reproductive performance and economic outcome of 3 synchronization strategies for first artificial insemination (AI) of dairy heifers. Holstein heifers from 2 herds (site A, California, n = 415; site B, Idaho, n = 425) were assigned to 1 of 3 treatments. Heifers assigned to the AT on estrus (ATE) treatment received an injection of 25 mg of PGF(2 alpha), at enrollment (d 0) and every 11 d thereafter until AT occurred. Heifers assigned to the CIDR5 treatment received a controlled internal drug release insert (CIDR) containing 1.38 g of progesterone, which was removed 5 d later concomitantly with an injection of 25 mg of PGF(2 alpha), and received fixed-time AT (TAI) concomitantly with an injection of 100 mu g of GnRH 53 to 60 h later. Heifers assigned to the CIDR7 treatment received a CIDR insert, which was removed 7 d later concomitantly with an injection of 25 mg of PGF(2 alpha), and received TAI concomitantly with an injection of 100 p,g of GnRH 53 to 60 h later. Heifers were observed for estrus and inseminated up to 98 and 73 d after enrollment in sites A and B, respectively. Thereafter, heifers were moved to pens with bulls and considered failure to conceive to AT if still not pregnant at the end of the observation period. Economic outcomes were based on cost of synchronization protocol (CIDR treatment = $11, PGF(2 alpha), or GnRH treatments = $2.5/treatment, estrous detection = $0.80/heifer per day), rearing cost ($2.75/heifer per day), and economic loss if a heifer did not conceive to first AT ($150). Input cost of the reproductive programs = synchronization protocol cost + semen cost + rearing cost + replacement cost. Pregnancy per AT (P/AI) 38 +/- 3 d after first AT was greatest for ATE heifers (61.1%) followed by CIDR5 (44.8%) and CIDR7 (35.7%) heifers. Furthermore, P/AI 73 +/- 7 d after first AT was greatest for ATE (58.8%) and tended to be greater for CIDR5 (42%) than for CIDR7 (34.1%) heifers. The percentage of heifers that had spontaneous luteolysis from CIDR insertion to CIDR removal was reduced for CIDR5 compared with CIDR7 (13.8 vs 31.8%). Pregnancy rate was greatest for ATE heifers but did not differ between CIDR5 [adjusted hazard ratio (95% confidence interval) = 0.75 (0.63, 0.90)] and CIDR7 [adjusted hazard ratio (95% confidence interval) = 0.65 (0.54, 0.77)] heifers. Consequently, rearing cost and input cost of ATE heifers ($67.1 +/- 4.4 and $107.1 +/- 7.0, respectively) were reduced compared with CIDR5 ($86.9 +/- 5.1 and $143.4 +/- 8.1, respectively) and CIDR7 ($98.3 +/- 5.1 and $156.5 +/- 8.2, respectively) heifers, but no differences were observed between CIDR5 and CIDR7 heifers.