Cliff Lamb (left) and Rick Funston talked about nutrition’s role and the role of body condition in reproductive performance.

RENO, Nev. (Feb. 6) — Four speakers came together for the Cattlemen’s College session “Beef Briefs: The Bottom Line on Reproduction.” With expertise from four states, the speakers took turns and also worked together to put on the session about reproduction.
Fixed-time artificial insemination (FTAI) in heifers and cows. Dave Patterson, University of Missouri (MU), focused on synchronization strategies for heifers and cows. Starting with heifers, Patterson asked the question, how do long-term and short-term CIDR®-based products compare in heifers?
“Until recently, there have been no comprehensive studies in estrous cycling and pre/peripubertal beef heifers studying the long-term protocol for (CIDR Select) and short-term CIDR-based protocols (Co-Synch + CIDR),” he said. Patterson explained the results of a recently completed study comparing the short-term and long-term CIDR protocols.

MU’s Dave Patterson provided an overview of some fix-time AI protocols and their success in heifers and cows.

The short-term CIDR protocol consisted of administering gonadatropin-releasing hormone (GnRH), then inserting a CIDR. On Day 7 the CIDRs were pulled and the heifers received a prostaglandin (PG) injection. They were AI-bred 54 hours later.
The CIDR Select protocol began with insertion of the CIDR for 14 days. Nine days later, heifers were administered GnRH, followed seven days later with a PG injection. Seventy-two hours later, the heifers were AI-bred.
Results showed pregnancy rates to the long-term CIDR protocol proved to be approximately 15% higher in both cycling and pre/peripubertal heifers.
Patterson then shared a study on cows that looked at pregnancy rates following synchronization with Co-Synch + CIDR and timed AI fixed at 55 hours or 66 hours after the PG injection. Among cows exhibiting estrus, the study reported a 65% pregnancy rate to FTAI at 54 hours and an 81% pregnancy rate to FTAI at 66 hours. Among females that did not show estrus, FTAI at 54 hours resulted in a 54% pregnancy rate and FTAI at 66 hours resulted in a 58% pregnancy rate.
Patterson concluded that significantly more cows exhibited estrus prior to FTAI when performed at 66 hours vs. 54 hours, and cows that exhibited estrus prior to FTAI had higher fixed-time AI pregnancy rates than cows that did not exhibit estrus.
Consider body condition. Cliff Lamb from the University of Florida reminded producers to consider body condition’s role in reproductive performance.
Studying the effects of body conditioning score (BCS), Lamb compared a BCS 7 and a BCS 5 female, then reduced the feed intake. The females then reached a BCS 3. Wanting to know how each would recover, it was shown there were some nutritional memories. Females formerly a BCS 7 had to recover to a BCS of 6 to start cycling again, while those that started at a BCS 5 didn’t have to recover as much to begin cycling.
Nutrition before birth. Reproduction is the single most important factor for profitable beef production,” stressed Rick Funston, University of Nebraska
That stated, Funston wanted to know if nutrition before birth affected the animals. He shared a study in which March-calving cows were split into two groups — one with calves weaned in August and one with calves weaned in November. In each of those groups there were subgroups, with those that were fed protein supplements and those not fed supplements.

Sandy Johnson provided and update on gender-sorted semen.

After three years, the supplemented group had higher birth weights, weaning weights, adjusted weights and pregnancy-check rates. Providing supplementation before birth did have an effect on the animal.
Gender-sorted semen. Sandy Johnson of Kansas State University finished the session by providing the audience an update on gender-sorted semen. Johnson began by explaining a few of the drawbacks to the technology.
“Sexed-semen will not be from the highest demand bulls,” Johnson said. “With 63% of the semen cells wasted in the sorting process, it costing $30 over unsorted semen and fertility at only 70% to 90% under excellent conditions, semen will not be used from high-demand bulls. But technology will improve down the road.”
— by Mathew Elliott

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