News from the Midwest Sectional Meetings, March 16-18, 1998, Des Moines, Iowa
Contacts:
James Kinder, University of Nebraska (402)472-6438
Vicki Miller, IANR science writer, (402)472-303
NU Research Shows Insert Helps Synchronize Beef Cows’ Reproduction
LINCOLN, Neb — Producers are eager for better ways to manage beef cattle reproduction. Getting cows and heifers into heat and successfully bred at about the same time shortens the breeding season and makes artificial insemination more practical.
Several university and federal animal scientists are jointly testing an intravaginal insert that may fit that bill. The insert effectively synchronized heat, or estrus, in cows and heifers and induced estrus in some animals, a University of Nebraska study showed.
"It dramatically improved the pregnancy rates in our heifers," said Jim Kinder, a beef reproductive physiologist in NU’s Institute of Agriculture and Natural Resources. That probably was due to the large number of heifers that hadn’t initiated estrus at the time of treatments.
The T-shaped insert contains progesterone, the natural reproductive hormone cows produce that prepares them for pregnancy. The device is simple to insert and remove, requires no incisions, and had a 98 percent retention rate in this study, he said.
Manufactured by InterAg, a New Zealand company, the insert is not yet approved for U.S. use. Nebraska researchers teamed with university colleagues at Oklahoma State, Missouri, Florida, Illinois, Rutgers, and U.S. Department of Agriculture scientists at the Miles City, Mont., research station to test the insert. Researchers will submit combined findings to the U.S. Food and Drug Administration as part of the process for getting the insert approved for estrus cycle control in beef cattle.
"We’re hoping for FDA approval in five years," Kinder said.
NU graduate student Leslie Ehnis and Kinder tested the insert in a study involving 150 cows that had recently calved and 123 heifers approaching their first estrous cycle. They compared the effectiveness of the insert coupled with an injection of prostaglandin, another natural hormone, to a prostaglandin shot alone and an untreated control group of cows and heifers.
The insert was placed in cows and heifers for seven days with the prostaglandin injection on the sixth day. Ehnis began twice daily estrus detection two days after removing the insert and artificially inseminated twice daily for 31 days.
Heifers receiving the insert/prostaglandin treatment began estrus sooner than those receiving prostaglandin alone or no treatment. The insert also boosted heifer pregnancy rates compared to the other treatments during the first four days, but didn’t significantly improve pregnancy rates among cows during the period.
Within the four days following treatment, 55 percent of the insert/prostaglandin treated heifers became pregnant compared with 5 percent of prostaglandin-only heifers and none of the untreated heifers.
Researchers focused on pregnancy rates during the first four days after treatment because this period best indicates the treatments’ effectiveness. The four days after treatment also are important because they represent the potential for shortening the breeding cycle, which would make artificial insemination more practical and less time- and labor-intensive.
While the insert would be used mainly to synchronize estrus, it has the added benefit of inducing estrus in some animals, Kinder said. "In heifers and cows that haven’t initiated estrus, the advantage with the insert is that you will induce estrus in some animals."
Only about 20 percent of heifers in this study had initiated estrus when the treatment started because they were in relatively low body condition.
"The insert dramatically improved pregnancy rates in the heifers, partly because the insert induced estrus," Kinder explained. He expects results from other states may be less dramatic, but thinks the insert would be effective on heifers in better condition.
While some estrus synchronization methods use hormones that cows don’t naturally produce, Kinder said, the insert employs all natural substances in concentrations no greater than cows produce.
"It’s important that we’re not putting anything synthetic into the system."
Controlling beef cattle’s reproductive cycle is important to improving beef products’ quality, consistency and predictability, Kinder pointed out. Artificial insemination offers the genetic control to meet that need. However, beef producers don’t widely use artificial insemination because it’s labor intensive unless reproductive cycles are synchronized.
"If we’re going to control the genetics in cattle to produce a more consistent, predictable product, we’re going to have to use artificial insemination," Kinder said. "What we’re all about here is trying to develop a better method for controlling reproductive function to make artificial insemination more practical."
Ease of use and effectiveness are among the intravaginal insert’s advantages compared to other estrus synchronization methods, Kinder said. For example, ear implants require an incision for removal. Feed additives are less consistent because different animals eat varied amounts of feed, which means they get different doses of hormone, making withdrawal time more variable.
Ehnis presented the Nebraska research results Tuesday (March 17) at the Animal Society of Animal Science Midwest Section meeting in Des Moines.
InterAg helped fund this research and Nebraska’s portion of the study was conducted in cooperation with IANR’s Agricultural Research Division.
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