A critical A.I. schedule

A webinar hosted by Valley Agriculture Software tackled an important topic for the dairy industry: timing A.I. relative to synchronized ovulations or increased activity.

Dr. Paul Fricke, a faculty member in the Department of Animal and Dairy Science at the University of Wisconsin-Madison, presented his findings based on his research.

Dr. Fricke’s goal is to improve the reproductive efficiency of dairy cattle by applying knowledge gained through scientific research to develop practical management strategies and assess new reproductive technologies.

Effective timing of A.I. relative to synchronized ovulation or increased activity on fertility and lactating dairy cows, according to Dr. Fricke, is dependent on four elements.

“When troubleshooting the conception rate problems on farms, we need to look at four buckets: timing of A.I., A.I. efficiency, male fertility and female fertility,” he said.

Dr. Fricke made the following three points in his presentation. Correct timing of insemination is critical for good fertility. Protocols result in poor fertility because insemination occurs too early relative to ovulation. And finally, the insemination window for optimal fertility is approximately 13-23 hours after the second generation of double ovsynch or resynch protocol, or after an alert based on an activity monitoring system.

A big factor in determining the timing of A.I. Dr. Fricke said is the timing relative to estrus or ovulation. Ovulation occurs 27-28 hours after the first standing event of estrus.

“If you can detect the first standing event of estrus, you want to inseminate before ovulation,” Dr. Fricke said. “You do this because you have to allow time for sperm capacitation and transport; this allows for the AM/PM rule.”

The AM/PM rule refers to the practice of observing a cow in estrus and inseminating 12 hours later. It was first implemented after data from a study in 1943, which showed that conception rates were lower when breeding too close to estrus compared to breeding at the start or middle of estrus.

“I want to kill off the AM/PM rule,” Dr. Fricke said. “If we’re just watching for estrus on balance, you’re going to breed too late if you strictly adhere to AM/PM.”

Another issue Dr. Fricke discussed was synchronized grading programs with ovsynch and co-synch.

“These came along in the mid-1990s,” Dr. Fricke said. “The first paper on ovsynch was published in 1995. Through this they developed the 16-hour window from (gonadotropin-releasing hormone) injection to insemination. I think that was their best estimate of what it should be.”

Through his presentation, Dr. Fricke displayed graphs that showed the results from a study about the 16-hour interval.

At a Wisconsin farm, with groups of 150 cows, cows were bred immediately after injection, and at 8 hours, 16 hours, 24 hours and 32 hours from injection. It was determined that conception rates at 8 hours, 16 hours and 24 hours were 41%, 45% and 41%, respectively.

“Based on this data, 16 hours appears the best,” Dr. Fricke said. “When you dive into the statistics, there is no difference between breeding at 8, 16 and 24. Thirty-two hours was definitely much worse.”

With this information, dairy farmers have used a co-synch protocol to help achieve timely A.I. without needing estrus detection. A drawback is that breeding can be done too early. One study demonstrated a conception rate of 27% with a co-synch protocol compared to a 36% rate with an ovsynch protocol. The rates also change depending on whether the semen used was conventional or sexed.

“One of the mistakes that’s made is trying to use sexed semen the same way as conventional semen,” Dr. Fricke said. 

Dr. Fricke developed an observational study of three farms in the upper Midwest using a double ovsynch protocol for first breeding. The study used GnRH in the afternoon and breeding in the morning.

“Sixteen hours was the interval we wanted, but the breeders didn’t want to come back to the farm,” Dr. Fricke said. “So, we moved the group to a 24-hour interval, essentially breeding later. We saw a 14% decrease in fertility at the first pregnancy check, and a 17% decrease at the recheck. We learned there that we don’t want to change the timing of insemination.”

In fact, Dr. Fricke stated that with a double ovsynch protocol, it was important to keep the standard timing of the second GnRH injection and timed A.I. if using sexed semen.

“The biggest thing I can say is stop using a co-synch protocol,” Dr. Fricke said. “If you’re doing A.I. protocols, you have to deal with biology and you have to put semen in the cows at the right time relative to that synchronized ovulation.”

This was further illustrated by his findings in another observational study. During this study, Dr. Fricke observed three sets of data — one randomized controlled experiment and two large observational studies — all dealing with the timing of A.I. with conventional and sex sorted semen.

The three sets of data were displayed through six Wisconsin farms that added a double ovsynch protocol, with randomized cows getting a co-synch protocol either at breeding, at the timed A.I. or at 16 hours from estrus.

“We found the co-synch protocol at a 36% conception rate compared to the double ovsynch at a 46% rate when breeding at the right time,” Dr. Fricke said. “The study featured 2,225 cows on six dairies and the co-synch yielded poor fertility.”

Another observational study featured two farms with a double-ovsynch protocol. Insemination at this farm was handled 13-23 hours relative to the last GnRH treatment. The findings were similar to another study from a Texas farm that depicted peak insemination time of the 13–23-hour window following the last GnRH treatment.

“You can put semen, sexed or conventional, 13-23 hours from GnRH and it’s flat across those time periods,” Dr. Fricke said. “If you want to breed cows on the correct time, you might need to generate lists twice a day when using a (radio frequency identification).”

Of those RFID herds, breeding 0-2 hours after an estrus alert, Dr. Fricke’s observations saw a 38% conception rate, and a 49% conception rate at 15-16 hours following the alert. Those results were with beef conventional semen and female sex sorted dairy semen.

By using the GnRH treatment, ovulation was a much tighter window than the onset of activity. This showed that optimal timing of breeding following GnRH is 13-23 hours.

“When you inseminate too early, you have decreased fertility because sperm sits in the female reproductive tract too long,” Dr. Fricke said. “It’s a sperm problem essentially when breeding too early.”