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Optimizing use of sexed and beef semen in dairy heifers
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Our objective was to evaluate reproductive management programs for submission of Holstein heifers for first insemination with sexed semen. Nulliparous Holstein heifers (n = 736) from three commercial farms were randomized within farm to one of three treatments for first AI with sexed semen: 1) CIDR5 (d -6, GnRH +CIDR; d -1, PGF2a -CIDR; d 0, PGF2a; d 2, GnRH+TAI); 2) CIDR6 (d -6, GnRH +CIDR; d -1, PGF2a; d 0, PGF2a -CIDR; d 2, GnRH+TAI); and 3) EDAI (PGF2a on d 0 followed by once daily estrus detection and AI). Heifers detected in estrus 24 h before TAI (d 1) were inseminated and the protocol was discontinued. All heifers were inseminated with sexed semen (ABS Sexcel™ Sexed Genetics, DeForest, WI) from sires that were randomly allocated between treatments within each farm, and AI technicians were blind to treatment at AI. Heifers were followed for 84 d after first service to determine days to AI and pregnancy. Actual farm costs (US$) were used for hormonal treatments, detection of estrus, semen and AI, pregnancy diagnosis, and feed ($1.70/heifer/d) to calculate cost per pregnancy. Feed costs for nonpregnant heifers or heifers moved to a bull pen during the 84-d breeding period (n=112) were allocated to the feed costs for heifers that became pregnant during the 84-d breeding period. Pregnancy outcomes were analyzed using the GLIMMIX procedure of SAS with farm included as a random effect in the model. Costs were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and farm as a random effect in the model. Delaying CIDR removal decreased early expression of estrus before scheduled TAI (0.004%vs. 27.8%); however, CIDR5 heifers tended to have more P/AI at 35 (52.9% vs. 45.3% vs. 45.8%) and 64 (51.8% vs. 44.8% vs. 44.9%) d after AI than CIDR6 and EDAI heifers, respectively. Overall, CIDR5 and CIDR6 heifers had fewer days to first AI and pregnancy than EDAI heifers which resulted in less feed costs than EDAI heifers due to fewer days on feed until pregnancy. Despite greater hormonal treatment costs for CIDR5 heifers, costs per pregnancy were $16.66 less for CIDR5 than for EDAI heifers. In conclusion, delaying CIDR removal by 24 h within a 5-CIDR-Synch protocol suppressed early expression of estrus before TAI, but tended to decrease P/AI for heifers inseminated with sexed semen. Further, submission of heifers to a 5-d CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared to EDAI heifers.
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