Comparison of reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen based on expression of estrus, pregnancy outcomes, and cost per pregnancy

摘要

Our objective was to evaluate reproductive managementprograms for submission of Holstein heifers forfirst insemination with conventional or sexed semen.In experiment 1, nulliparous Holstein heifers (n = 462)were submitted to a 5-d progesterone-releasing intravaginaldevice (PRID)-Synch protocol [d 0, GnRH +PRID; d 5, PGF_(2α) − PRID; d 6, PGF_(2α); d 8, GnRH +TAI] and were randomly assigned for PRID removalon d 5 or 6 of the protocol followed by timed artificialinsemination (TAI) with conventional semen. DelayingPRID removal decreased early expression of estrusbefore scheduled TAI (0.9 vs. 12.2%), and pregnanciesper AI (P/AI) did not differ between treatments. Inexperiment 2, nulliparous Holstein heifers (n = 736)from 3 commercial farms were randomized within farmto 1 of 3 treatments for first AI with sexed semen: (1)CIDR5 [d −6, GnRH + controlled internal drug release(CIDR); d −1, PGF_(2α) − CIDR; d 0, PGF_(2α); d 2, GnRH+ TAI]; (2) CIDR6 (d −6, GnRH + CIDR; d −1,PGF_(2α); d 0, PGF_(2α) − CIDR; d 2, GnRH + TAI); and(3) EDAI (PGF_(2α) on d 0 followed by once-daily estrousdetection and AI). Delaying CIDR removal decreasedearly expression of estrus before scheduled TAI (0.004vs. 27.8%); however, CIDR5 heifers tended to havemore P/AI at 35 (53 vs. 45 vs. 46%) and 64 (52 vs. 45vs. 45%) days after AI than CIDR6 and EDAI heifers,respectively. Overall, CIDR5 and CIDR6 heifers hadfewer days to first AI and pregnancy than EDAI heiferswhich resulted in less feed costs than EDAI heifers dueto fewer days on feed until pregnancy. Despite greaterhormonal treatment costs for CIDR5 heifers, costs perpregnancy were $16.66 less for CIDR5 than for EDAIheifers. In conclusion, delaying PRID removal by 24 hwithin a 5-d PRID-Synch protocol in experiment 1 suppressedearly expression of estrus before TAI, and P/AI for heifers inseminated with conventional semen didnot differ between treatments. By contrast, althoughdelaying CIDR removal by 24 h within a 5-CIDR-Synchprotocol in experiment 2 suppressed early expressionof estrus before TAI, delaying CIDR removal by 24 htended to decrease P/AI for heifers inseminated withsexed semen. Further, submission of heifers to a 5-dCIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared withEDAI heifers.