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Reproductive strategies for beef cattle

Progressive Cattleman Staff Tony Okon Published on 23 December 2011
AI samples are withdrawn from a dewar

Reproductive technology presence in the beef industry is low because of time, labor, cost and lack of facilities.

However, University of Idaho beef specialist John Hall said 97 percent of beef producers will admit that these reproductive strategies work.

“Only 7.9 percent of the operations in the U.S. use estrus synchronization and some of those ranches are using estrus synchronization with natural service,” Hall said.

Hall, speaking at the Applied Reproductive Strategies in Beef Cattle – Northwest, in Boise, Idaho, on Sept. 30, said there are two crucial factors influencing the reason to adopt estrus synchronization and A.I. in beef cattle.

“We have the tools and technologies to overcome or at least manage a number of the factors influencing the success of estrus synchronization and A.I.,” he said. Hall’s second reason is “the management, production, genetic and final product benefits are significant.”

“One key strategy is for cows to be physiologically ready by managing to increase the percentage of females cycling at the beginning of the breeding season and designing synchronization systems that induce cycles in anestrous females,” Hall said.

“Pregnancy rates greater than 90 percent in a controlled breeding natural service program are a good indicator of readiness for A.I.,” added Hall.

Nutrition also plays a key role in females cycling at the beginning of breeding season.

According to Amin Ahmadzadeh, professor in the Department of Animal and Veterinary Science at the University of Idaho, nutritional management involving proper weights of gain and targeted bodyweights present a greater opportunity to decrease the time interval to onset of puberty and increase reproductive efficiency.

Another important issue to go along with females cycling at the beginning of the breeding season is dealing with postpartum anestrus.

“A major limitation to the success of rebreeding after each calving is the presence of postpartum anestrus in the cow herd,” Ahmadzadeh said.

Suckling and BCS, or body condition score, have an influence on postpartum anestrus as well. “Cows with body condition scores less than 5 (1 = emaciated and 9 = obese) are at a greater risk for prolonged intervals to return to first estrus than cows with a greater body condition score,” Ahmadzadeh said.

Management protocols have been developed to help cope with the suckling factor, which increases postpartum anestrus, he said.

One practice is 48-hour calf removal, which should be combined with some methods of estrous synchronization. Another practice would be once-daily suckling, which appears to be more beneficial with first-calf heifers.

“It’s counterintuitive to say a successful natural service program is key to an A.I. program, but it really is,” Hall said.

A tight calving season with high pregnancy rates during the breeding season is important before adding an A.I. program. “This is a good indicator that cow fertility and herd management are ready for A.I.,” Hall said.

According to David Patterson, professor in the Division of Animal Sciences at the University of Missouri, effective estrus synchronization programs offer multiple advantages:

  • Cows or heifers are in estrus at a predicted time, which facilitates A.I., embryo transfer or other assisted reproductive techniques.
  • The time required for detection of estrus is reduced, thus decreasing labor expense associated with estrus detection.
  • Cattle will conceive earlier during the breeding period.
  • A.I. becomes more practical.
  • Calves will be older and heavier at weaning.

“Expanded use of A.I. and adoption of emerging reproductive technologies for beef heifer and cows require precise methods of estrous cycle control,” Patterson said.

However, Patterson included in his report that the tools are available for producers to ensure “high-quality” U.S. beef.

Hall said the human variable is an important consideration in optimizing an A.I. program. “By taking a ‘we’ll try it and see how it works’ attitude, an operation is headed down the road to poor performance.”

“All involved should understand the basic procedures, animal handling principles and benefits of the program,” Hall said. He also said the value of good technical assistance should not be underestimated.

According to Hall, one of the most significant barriers to a successful A.I. program is effective estrus detection.

“Producers do a good job identifying cows that are really in heat but fail to find a significant portion of females that are actually in estrus.”

“If electronic estrus detection aids are used, we’ll pick up a lot more cows and do a much better job,” Hall said.

The availability of Gonadotropin-releasing hormone (GnRH), new controlled drug-release devices and the availability of systems that synchronize ovulation eliminate the need for estrus detection.

“Positive impacts of a successful estrus synchronization and A.I. program included tighter calving distribution, increasing the percentage of calves born early in the calving season, reduced dystocia and increased product quality and calf value,” Hall said.

Hall said beef producers shouldn’t be concerned that estrus synchronization and A.I., especially fixed-time A.I., could result in an overwhelming number of calves born on a single day.

Hall will see no more than 20 percent of calves born on any single day out of the 300-plus cows he’ll breed by A.I. in a day or two at his research station.

“Using estrus synchronization and A.I. repeatedly over a period of years shifts a greater percentage of calves born to the early portion of the breeding season,” Patterson said. Increased weaning weights and calf value increase when more calves are born early in the breeding season.  end_mark

PHOTO:

TOP: Successful A.I. programs depend on several key factors such as heat detection, herd health and herd management.  Staff Photo.

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