A modified presynchronization protocol improves fertility to timed artificial insemination in lactating dairy cows.
To compare 2 hormonal protocols for submission of lactating dairy cows for timed artificial insemination (TAI), nonpregnant lactating Holstein cows (n = 269) >60 d in milk were randomly assigned to each of 2 treatments to receive TAI (TAI = d 0). Cows assigned to the first treatment (Ovsynch, n = 134) received 50 microg of GnRH (d -10), 25 mg of PGF2alpha (d -3), and 50 microg of GnRH (d -1) beginning at a random stage of the estrous cycle. Cows assigned to the second treatment (Presynch, n = 135) received Ovsynch but with the addition of 2 PGF2alpha (25 mg) injections administered 14 d apart beginning 28 d (d -38 and -24) before initiation of Ovsynch. All cows received TAI 16 to 18 h after the second GnRH injection. Ovulatory response after each GnRH injection for a subset of cows (n = 109) and pregnancy status 42 d after TAI for all cows were assessed using transrectal ultrasonography. Based on serum progesterone (P4) profiles determined for a subset of cows (n = 109), P4 concentrations decreased for Presynch cows after the first 2 PGF2alpha injections, and Presynch cows had greater P4 concentrations at the PGF2alpha injection on d -3 compared with Ovsynch cows. Although the proportion of cows ovulating after the first and second GnRH injections did not differ statistically between treatments (41.1 and 69.6% vs. 35.9 and 81.1% for Ovsynch vs. Presynch, respectively), pregnancy rate per artificial insemination (PR/AI) at 42 d post TAI was greater for Presynch than for Ovsynch cows (49.6 vs. 37.3%). Parity, DIM, and body condition score (BCS) at TAI did not affect PR/AI to TAI. These data support use of this presynchronization protocol to increase PR/ AI of lactating dairy cows receiving TAI compared with Ovsynch.
Navanukraw
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Department of Animal and Range Sciences, North Dakota State University, Fargo 58105, USA.
Redmer
D A
DA
Reynolds
L P
LP
Kirsch
J D
JD
Grazul-Bilska
A T
AT
Fricke
P M
PM
D000818:Animals; D001823:Body Composition; D002417:Cattle; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D005298:Fertility; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D007774:Lactation; D010062:Ovulation Induction / Q000662:veterinary; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D013997:Time Factors; D016896:Treatment Outcome
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost