While the beef industry has worked together to come up with a standard protocol for fixed-time AI in cows and heifers, that’s not where researchers have stopped. They continue to look for additional information to improve beef production.
One of the things University of Missouri researchers discovered as they looked at heifer development is the importance of identifying the fertility response of heifers before breeding, said University of Missouri researcher David Patterson during a recent webinar from the National Cattlemen’s Beef Association.
We want to “really work toward developing the concept that in order to obtain success with AI programs and heifers. It's probably a good idea to determine how many of your heifers are cycling and are they fed back, ready to synchronize,” Patterson said. “With our program in Missouri, all heifers are required to go through a pre-weaning exam that's referred to as a reproductive tract score. It is a direct assessment of reproductive development.”
Heifers are ultrasounded or palpated transrectally to be assigned a score of 1 to 5. A score of 1 or 2 would indicate a pre-pubertal heifer that is more than 30 days from reaching puberty, with 5 being the heifer is in the luteal phase (somewhere between day 6 and 16) of a heat cycle.
Fast-forward to about 8:00 to hear Patterson's comments.
Timing of these exams are critical—they should be performed four to six weeks before breeding. Synchronization should start only when more than half of the heifers have RTS of 4 or 5, he added.
“One of the things that I think is interesting about the timing of these … is that they very effectively coincide with the start of one of the long-term progestin-based protocols,” Patterson said.
In many cases prebreeding booster vaccinations are administered at the time reproductive evaluations are performed and track scores are assigned, setting up the synchronization protocol timeframe.
“Our veterinary practitioners across the state are getting much more involved with pre-breeding evaluations or reproductive management in general,” he said. “So when the pre-breeding exams are performed, basically it's one-stop shop.”
Learn more by watching the player above.