Reproduction: More Than Just Breeding Cows

8/24/2013 7:00 AM
By Jessica Rose Spangler Reporter

Reproduction efficiency affects everything else, according to nutrition expert James Ferguson.

“Decreased efficiency decreases the number of replacements, increases disease costs because of bringing in new animals,” he said.

Basically, reproduction affects the checkbook in more ways than just the semen bill.

Ferguson, a professor at the University of Pennsylvania School of Veterinary Medicine, presented “Reproductive Management Strategies for a 25 percent Pregnancy Rate or Higher” on Aug. 9, part of the Pennsylvania Dairy Futures Analysis Friday webinar series.

The Pennsylvania Dairy Futures Analysis was a joint project of the Center for Dairy Excellence, Penn State Extension Dairy Team, University of Pennsylvania and St. Joseph’s University School of Food Marketing.

After examining multiple areas of the “typical” Pennsylvania dairy farm, the group released its full report in June 2013.

When it comes to reproduction, Ferguson believes Pennsylvania dairy farmers are missing the mark.

The average pregnancy rate is 17.6 percent with cows being open for a minimum of 146.6 days. The average heat detection rate is 46.4 percent.

The conception rate for the first breeding is 42.7 percent, the second breeding 43 percent, and the third 41.7 percent. Nineteen percent of animals being culled left for reproductive reasons, with an overall culling rate of 36 percent.

“Heat detection rates have been constant over the last few years,” Ferguson said. “It’s not great because half the cows are not being detected. It’s too low, just unacceptable. Farmers can be over 70 percent with good strategies and programs.”

If conception rates fall below 30 percent, breeding techniques and semen handling need to be reviewed. Ferguson also recommends having breeders review their skills annually at a training school.

So what benchmarks should dairy farmers strive to reach?

According to Ferguson, “the goals for reproduction are to minimize losses and maximize returns.”

Pregnancy rates should be greater than 20 percent for minimum losses and more than 30 percent for maximum returns. Days open should be fewer than 140. Pennsylvania’s average cull rates are pretty close to the national par of 30 to 35 percent.

“With pregnancy rates below 20 percent, reproductive losses are very steep, six times greater than if it was above 20 percent,” he said. “They still happen (above 20 percent), but they’re small.”

A reproductive loss equates less milk production per day, which results in longer dry periods — more than 70 days — and fewer calves born each year.

If cull rates are at 20 to 25 percent — lower than the Pennsylvania average — there aren’t enough replacements entering the herd to maintain the current herd size, unless animals are purchased.

Less milk produced also equates to the obvious less milk being shipped, resulting in less income.

“Sexed semen can help, but at an increased cost with decreased conception,” Ferguson said. “Most Pennsylvania farms are capable of a 25 percent pregnancy rate with a few changes.”

Currently, the average number of days until first insemination is 91.5, higher than the goal of 60 to 80 days, depending on the farm’s voluntary waiting period.

Eighty percent or more of cows should be inseminated within 21 days of the voluntary waiting period.

“The majority of cows, it’s safe to say, have started cycling by 50 days. I’m comfortable with a 50 day voluntary waiting period with a maximum days to first service by 70,” he said.

Dairy farmers also need to monitor the distribution of their days until first service. The use of graphs and charts can be helpful. Farmers can use either visual heat detection or a PreSynch/Ovsynch program and achieve basically the same results, as long as pregnancy diagnosis occurs regularly.

“Control days between inseminations that are longer than 48 days. The goal is to have less than 15 percent repeat inseminations,” Ferguson said. “There should be consistent pregnancy diagnosis ever one to two weeks prior to 42 days post insemination to control the proportion of cows reinseminated.”

Farmers who are using PreSynch/Ovsynch and PostSynch should have almost no cows open 48 days after first insemination. Pennsylvania herds on that protocol average 4 to 6 percent open after 48 days, which equates to natural embryo loss.

Conception rates should be more than 40 percent. To achieve this, farmers need to minimize postpartum problems, including metritis, retained placentas, ketosis, displaced abomasums, mastitis, high somatic cell counts and lameness.

Less than 40 percent of cows should experience postpartum problems. The higher the incidence of issues, the lower the conception rates.

Some of those problems can be attributed to transition cow feeding, which also correlates with body condition losses. Cows should lose less than 1 unit of body condition within 30 days of calving.

The accuracy of heat detection also comes into play.

“If she’s not in heat, she doesn’t get pregnant,” Ferguson said. “Five to 15 percent of cows are bred when they’re not in heat.”

With a voluntary waiting period of 60 to 80 days, most cows will have gone through at least one estrus cycle already.

“The first ovulated oocyte is not very fertile. There’s not a lot of progesterone. If you’re going to be inseminating on the first (heat), expect lower fertility. The second is better,” he said. “By the third, expect normal ovulation and fertility.”

No matter what voluntary waiting period a herd has or what heat detection method farmers are using, consistency is key. Farmers should define a program and stick to it each week or bi-weekly.

“Weekly or bi-weekly pregnancy diagnosis isn’t to find bred cows, but to find open cows,” Ferguson said. “If you find open cows, they need to be entered into the program to ensure breeding within 21 days or you just wasted your money on the diagnostic test.”

No cows should be left out of the program unless they’re not going to get bred at all and will eventually be culled.

“Cows you think might not be ready for the program aren’t totally infertile; 20 to 25 percent will still become pregnant,” Ferguson said.

Farmers also need to be continually monitoring performance, specifically bi-weekly or monthly insemination rates and quarterly conception rates.

“Conception rates are in the rearview mirror. We’re always looking back to see what happened,” Ferguson said. “Insemination rates are timely and happening now. It’s critical to monitor insemination rates because they drive the system and can be dealt with now.”

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