Optimization of timing of insemination of dairy heifers inseminated with sex-sorted semen

摘要

We hypothesized that delaying by approximately12 h the artificial insemination (AI) of heifers withsex-sorted semen increases pregnancy per AI (P/AI).Holstein heifers (n = 1,207) were fitted with a collarcontaining an automated estrus-detection device (HRLDntags, SCR Engineers Ltd., Netanya, Israel) at 10.7± 0.02 mo of age. Once they reached 330 kg, heiferswere enrolled in an ovulation synchronization protocol(5-d Cosynch + controlled internal drug release; Zoetis,Parsippany-Troy Hills, NJ). Study personnel recordedthe heifers that were in estrus according to the Data-Flow II software (SCR Engineers Ltd., Netanya, Israel)twice daily at 0500 and 1500 h from the day of thefirst PGF_(2α) (Estrumate; Merck Animal Health, Madison,NJ) injection to 72 h later. Heifers enrolled in theconventional (CONV) and early sex-sorted (SSEarly)semen treatments detected in estrus at 0500 and 1500h were AI at 0600 and 1600 h of the same day, respectively.Heifers enrolled in the late sex-sorted (SSLate)semen treatment detected in estrus at 0500 and 1500h were AI at 1600 h of the same day and 0600 h of thefollowing day, respectively. All heifers not detected inestrus by 72 h after the first PGF2α injection received aGnRH (Fertagyl; Merck Animal Health, Madison, NJ)injection at 0500 h. Heifers in the CONV and SSEarlytreatments were AI at fixed time at 0600 h, whereasheifers in the SSLate treatment were AI at fixed timeat 1600 h. Among heifers detected in estrus, the rangesof the interval from the onset of estrus to AI were 3.6 to28.5 h, 0.0 to 25.5 h, and 9.4 to 36.8 h for the CONV,SSEarly, and SSLate treatments, respectively. Amongheifers AI at fixed time, the ranges of the intervalfrom the GnRH injection to AI were 0 h for heifers inthe CONV and SSEarly treatments and 8.5 to 11.7 hfor heifers in the SSLate treatment. The P/AI at 62± 1 d after the first AI was greater for CONV (63.1± 2.6%) compared with SSEarly (43.3 ± 2.6%) andSSLate (44.8 ± 2.7%). A greater percentage of heifersenrolled in the SSEarly (65.8 ± 2.5%) and SSLate(70.0 ± 2.5%) treatments produced a live female calfcompared with the CONV treatment (40.5 ± 2.7%).When the values of 1-d-old female and male calves wereUSD $0 and the cost of replacement heifers was $750,the cost of raising heifers from enrollment to calvingwas lesser for the CONV treatment than the SSEarlytreatment, but SSLate treatment did not differ fromCONV and SSEarly treatments. When the values of a1-d-old female calf ≥$130 and 1-d-old male calf ≥$30and the cost of replacement ≥$1,000, no differenceswere observed among treatments in the cost from enrollmentto calving. We conclude from this experimentthat the P/AI with sex-sorted semen is not improvedwhen insemination is delayed by approximately 12 h.