In a normal double-ovsynch program, a shot of prostaglandin F2a (PGF) is given, followed by a gonadotropin releasing hormone (GnRH) 48 to 56 hours later, and is then followed with artificial insemination 16 hours after. So, from that perspective, things line up really nicely for shot administration after milking on either a 2x or 3x milking herd. It’s that pesky 16-hour window of the timed A.I. breeding that throws things off for 2x herds. Often, the decision has to be made whether a farm will breed early, breed late, or get the cows in an extra time.
On our operation, we give the PGF shot at our afternoon milking, followed by the GnRH shot at our evening milking 56 hours later, and then breed during the following day’s afternoon milking (about 16 hours).
For those who don’t have as flexible a schedule, the question becomes how much flexibility can we have without damaging fertility?
Three takeaways from protocol manipulation
“Research indicates a degree of flexibility exists in this timing,” dairy science professor Alan Ealy of Virginia Tech explained. “Optimal conception rates could be maintained when inseminating between 13 and 23 hours after the final GnRH injection.”
He left readers with three takeaways from this research.
1. Don’t inseminate too early or too late.
2. Use the 13-to-23-hour post-GnRH window.
3. Adjust for sexed semen with care.
“Timing of insemination is even more critical when using seed semen,” Ealy detailed. “The current recommendation is to delay A.I. to better align with the shorter lifespan and fertilization window of sexed sperm. For estrus-based breeding, inseminate at 18 to 20 hours post-estrus instead of the traditional 12 hours.” If not using estrus detection methods, Ealy suggested inseminating 22 hours post-GnRH instead of 16.
The author is a dairy farmer in Kansas and a former associate editor at Hoard’s Dairyman. Raised on a 150-cow dairy near Valley Center, Kansas, Maggie graduated from Kansas State University with degrees in agricultural communications and animal sciences.