It’s all about control
As spring calving draws to a close and pastures are greening up, many producers are thinking about the summer breeding season. Planning next year’s calf crop, many ranchers aim to bring new genetics to their cowherds through artificial insemination (AI). Following estrus synchronization protocols is one management tool cattlemen rely on to efficiently and easily settle replacement heifers and lactating cows before turnout time.
For Lori Repenning, DVM, rancher at Blacktop Farms in Mitchell, S.D. and animal science instructor at Mitchell Technical Institute (MTI), the breeding season offers a chance for her to give her students practical learning in a realistic setting. Each year, she has students join her and her husband Steve on the ranch as they breed their Angus and Hereford cattle, following a synchronization protocol to bring them into heat.
“We use the 14-day CIDR on our heifers with heat detection and timed AI on the rest,” said Repenning. “It works well for us because we freeze brand and work them on day one of the protocol. It requires a little planning as it is a 33-day program from start to finish. We have done 7-day CIDRS. too. Many years ago we used MGA, but you have to be very diligent feeding your progesterone to insure that everyone gets a daily dose.”
Rick Funston, University of Nebraska-Lincoln (UNL) professor and beef reproductive physiology specialist, said no matter which protocol a rancher chooses, success or failure is determined in the little details.
“It’s important to have an understanding of the synchronization program you choose and the products and labor needed to implement it,” said Funston. “I’ve heard from many producers over the years who have given the wrong shots or bred too far outside of the ideal window. This totally messes up any program.”
Mike Smith, University of Missouri professor of animal sciences spoke at a recent Applied Reproductive Strategies for Beef Cattle conference held in Joplin, MO, about the variables and mistakes that producers fail to control when trying to follow a specific program to synchronize cattle for AI.
“Many people have the idea that the good things they do in management will compensate for the mistakes they make, but the mistakes you make end up canceling out the good things you do,” said Smith, who listed several factors producers need to optimize including… “The number of healthy, cycling females at the beginning of the breeding season; careful attention to sire selection; implementation of an appropriate estrus synchronization protocol; low-stress cattle handling; purchase of high-quality semen; proper semen handling and insemination technique; good nutritional management before and after fixed-time artificial insemination.”
Warren Symens, of Symens Brothers Limousin in Amherst, S.D., is gearing up to breed 123 Limousin replacement heifers this spring following the melengestrol acetate (MGA) – prostaglandin (PG) program.
According to Funston, “Under this protocol, heifers expressing estrus in the first 72 hours following the prostaglandin injection are identified, removed from the herd, and artificially inseminated 12 hours later. At 72 hours, heifers not expressing estrus are given an injection of Gonadotropin Releasing Hormone (GnRH) and immediately artificially inseminated.”
“We’ve tried a lot of different protocols over the years with varying levels of success, and I think using MGA in a dry lot setting is a good option for us,” said Symens. “We have the lots, the bunk space and the facilities to manage the heifers’ feed intake, plus it’s fewer times the heifers have to go through the chute. We also lost some pasture this year, so having these heifers in the lot will allow us to easily catch them again in the next cycle before turning a clean-up bull in with them.”
When breeding replacement heifers, Funston said a common mistake producers make is feeding the group too hard before breeding.
“One of the most important things that producers need to keep in mind is to always have cattle that move into a system or environment where they will continue to gain equal or more than they did in the previous step,” recommended Funston. “For example, it’s problematic if heifers are dry-lotted and gaining over 2 lbs./day and then moved to grass right away after breeding where they won’t gain nearly as much. The worst case scenario is to have really fat heifers and then move them to grass where they don’t gain. It’s advantageous to have heifers on a lower ration gaining 1-1.5 lbs./day in a dry lot setting, and they will continue to make those gains once they are moved to grass.”Keep in mind that following breeding, heifers need to be moved within five days after fixed time AI or wait until 45 days to reduce stress and risk of the animal not settling.”
Prepping for the breeding season takes some research, organization and good planning. Producers need to get the AI kit ready, order semen, make breeding decisions, purchase medicine for various protocols, line up labor to help bring in cows to breed, and have a game plan for post-breeding. Typically, replacement heifers are bred earlier than calving cows, and there are a few different considerations for synchronizing lactating cows, particularly first-calf heifers.
“We use the 7-day CIDR for first- and second-calf heifers,” said Repenning. “This, along with better nutrition, has really helped keep our young cows calving early and therefore decreased the fallout of late calving young cows. We do breed most of our mature cowherd on natural heats. We follow the rule of if we detect heat in the morning, we breed them that evening, and visa versa.”
“We heat detect and AI the majority of our cow herd when they come into heat naturally,” said Symens. “The pairs are on grass, and we strive for stress-free handling. The most difficult part is having labor around to help bring the cows in to breed, and the timing of turnout in relation to available grass. We have never bred first-calf heifers. We have them sorted off for calving and to manage their feed intake a little more closely, and it’s just easy for us to turn a bull in and get them bred back on that first cycle.”
Repenning said that it’s important to have reasonable outcome expectations for any protocol, but there are certain things folks can do to improve conception rates.
“Plan ahead. Order semen early to get the bulls you want to use. Have supplies ready before starting the breeding season. Have cows in proper body condition scores of 5 and 6. We also
are big believers in Multimin, an injectable trace mineral. Studies have shown a 5-12% increase in conception rates using Multimin,” said Repenning.
According to Sandy Johnson, Kansas State University (KSU) livestock specialist, and Jeff Stevenson, KSUS professor of animal sciences, “Pregnancy rates (number pregnant per number exposed) after a 60-day breeding season should be 85-90% before considering an intensive synchronization and AI program. Lower fertility may indicate that some other aspect of management, such as nutrition or health, is less than optimal and would reduce the success of an AI program.
Being mindful of the many variables producers can work to optimize and control, Funston said of the many protocols ranchers can choose from, the 7-day CIDR works great.
“If we are working with lactating cows, a 7-day CIDR works as well as anything,” said Funston. “CIDRs are also an amazing tool at getting those younger, higher risk females to come out of anestrus and get cycling again; the progesterone exposure gets things going faster. I’ve had producers even use CIDRs to move up late-calving cows. The CIDR can be used as soon as 20-30 days postpartum, and can move the cattle up two or more cycles. Many don’t even AI after the CIDR, they just turn a bull in to ensure those cattle get bred back sooner.”
As the breeding season begins and producers choose which protocols to follow, cattlemen should keep in touch with a veterinarian, Extension educator, or nutritionist to help determine the best course of action for getting cattle settled.
Online resources can also be utilized such as those developed by the Beef Reproduction Task Force, a multi-state Extension project focusing on applied reproductive strategies in beef cattle. These resources can be found at beefrepro.unl.edu and include tools such as: an estrus synchronization planner, AI calculator, 2016 estrus synchronization protocol chart for heifers and cows, tips for heat detecting, and more.
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