Effect of timing of Cosynch on fertility of lactating Holstein cows after first postpartum and Resynch timed-AI services.
To compare two intervals from the PGF(2alpha) injection to the second GnRH injection+timed artificial insemination (TAI) of Ovsynch, lactating Holstein cows received their first postpartum TAI after Presynch + Ovsynch (n=352) and second and greater postpartum TAI after resynchronization of ovulation using Ovsynch (Resynch; n=458). Each week, cows housed in each of four breeding pens were randomized by breeding pen to receive the second GnRH injection of Presynch + Ovsynch or Resynch and TAI either 48 h (Cosynch 48; n=382) or 72 h (Cosynch 72; n=428) after the PGF(2alpha) injection of Ovsynch or Resynch. Overall, pregnancies per AI (P/AI) did not differ for cows receiving Cosynch 48 (29%) versus Cosynch 72 (33%). Furthermore, treatment did not affect P/AI for cows receiving first postpartum TAI after Presynch + Ovsynch, for cows receiving second and greater TAI after Resynch, or the proportion of female calves born. In conclusion, delaying the second GnRH injection and TAI from 48 to 72 h after the PGF(2alpha) injection of Ovsynch did not affect P/AI or calf sex ratio. The lack of a difference in fertility between these Cosynch protocols may offer more flexibility for implementing a systematic synchronization protocol when a Cosynch strategy is used.
Sterry
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RA
Department of Dairy Science, University of Wisconsin, Madison, WI 53706, USA.
Jardon
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PW
Fricke
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PM
D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004334:Drug Administration Schedule; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D005298:Fertility; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D049590:Postpartum Period; D011247:Pregnancy; D012744:Sex Ratio
D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost