Establishing reproductive momentum in replacement heifers

Make sure you take steps to get the most of your investment

Developing replacement females is an investment that can take years to earn back, making it essential to set them up early for reproductive success.

Kathy Larson, research economist at the University of Saskatchewan, discussed the financial considerations of developing replacement females in a Beef Cattle Research Council webinar, including whether to purchase heifers or retain them from your own calf crop.

“Part of that decision needs to involve cost of production,” she said. Depending on these costs, retaining replacements may be as expensive as buying heifers. When calculating the cost of each option, Larson recommends including opportunity costs, which is the revenue given up by choosing one option over another.

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“When you retain heifers to develop into replacement females, you’re essentially forgoing weaned calf sales, so you gave up the revenue you could have received had you sold them,” she explained. “I want you to consider both the cash and opportunity costs of taking a female from a weaned calf to a bred heifer.”

For example, Larson noted that a “heifer’s value as a weaned calf accounts for approximately 60 per cent of her development costs,” which is considered an opportunity cost.

Using a calculation of estimated production costs against predicted calf revenue, Larson illustrated that it can take an average of five to six weaned calves for a female to earn back the cost of developing her into a bred heifer. This will vary with calf prices and production costs.

“Cost of production varies widely between operations, so go through the exercise of figuring out what your cost of production is, and then figure out what your females need to wean in order to recoup your investment.”

Knowing this, setting up heifers for success in their first breeding season is crucial to begin earning back this investment. “I think it’s important to follow recommended practices to give your heifers the best shot at recouping their development costs,” she advised.

Dr. John Campbell, veterinarian and professor at the Western College of Veterinary Medicine, recommends creating reproductive goals to meet challenges specific to heifers. Campbell, who collaborated with Larson on this webinar, referred to heifers as a “high-risk group” for reproductive loss compared to mature cows.

“A lot of disease investigations I go to, the heifers are more severely affected if it’s a reproductive loss problem,” he said. “They have lower levels of immunity, they’re probably more susceptible to infectious diseases and they’re still growing and they’re a lot more susceptible to nutritional challenges.”

Due to this, it’s an absolute necessity for heifers to receive a pre-breeding vaccine for infectious bovine rhinotracheitis and bovine viral diarrhea. If buying replacements, Campbell recommends knowing the vaccination protocols of the herd of origin.

“Closer to the breeding season, usually 30 to 60 days prior to the breeding season, is the ideal time to get that done to provide maximum protection to the fetus.”

There are certain biological challenges in successfully breeding a female.

“If we took a perfectly fertile bull and perfectly fertile heifer and we put them together when that heifer’s cycling and they mate successfully, there’s only about a 60 to 70 per cent likelihood of a calf being born from a single mating,” he said. “If we have poor fertility caused by body condition issues or nutritional deficiencies or something else going on, that number is going to drop significantly.”

Another challenge is the post-partum delay before a cow begins cycling again, 50 to 60 days on average. However, heifers can take about 80 to100 days after their first calf to begin cycling.

“That’s if body condition scores are good, there’s no mineral deficiencies (and) everything else is taken care of,” Campbell added.

This extended post-partum interval needs to be taken into consideration when planning the breeding season. With gestation at around 280 days, “cows have to conceive within about 83 days of calving if they’re going to calve around the same time every year,” he explained. This is particularly important if the goal is to front-load the breeding season by having 65 per cent of the females bred in the first cycle, allowing for a more uniform calf crop and heavier calves at weaning.

Producers also need to factor in the age when a heifer reaches puberty. “We’re establishing their reproductive momentum the first time they calve, and so in order to have them conceive early… a high percentage of those heifers have to reach puberty close to the start of the breeding season,” said Campbell.

Evaluating heifers for reproductive soundness before the breeding season can be useful. “It’s a management strategy that I don’t think a lot of producers do, but I do think it’s a reasonable one,” he said. “We would just do a physical exam on these, palpate the reproductive tract and subjectively evaluate if that heifer is cycling.”

Heifers need to be bred early in their first two breeding seasons to hit that window of opportunity. “We want them to conceive early in the next breeding season for a second pregnancy, and that’s the challenge because of this delayed time before they start cycling after their first calf,” said Campbell, adding that this is the case even with healthy, fertile females.

A heifer that calves in the first 21 days of the calving season may only have two opportunities to be bred to calve around the same time next year. For a heifer that calves later in the season, “she’s not going to start cycling until the very last part of the breeding season, so she’s maybe only going to have one opportunity to be bred, if that.”

Given the extended post-partum interval, Campbell recommends breeding heifers earlier than mature cows to hit this target and establish their reproductive momentum. “You might want to consider breeding them for the 20 to 30 days prior to the cow herd.”

Selecting heifers that were calved earlier in the breeding season also increases the likelihood that they will hit puberty before breeding begins. Campbell discussed a large-scale 2014 study that included 2,000 heifers in South Dakota and 16,000 heifers at the U.S. Meat Animal Research Center at Clay Center, Nebraska. In comparing heifers born in the first 21 days of the calving season to heifers born in the next 21 days, researchers found that the females that calved earlier generally stayed in the herd longer than those born later.

“They tended to continue to calve in the first 21 days of the calving season, and they weaned heavier calves every year for six subsequent calvings because they tended to calve earlier,” said Campbell. “It ended up being almost an extra calf over a lifetime productivity. That’s not the first study that’s shown that, but it’s probably one of the biggest ones and most dramatic ones that has demonstrated the benefits of having those heifers calve early.”

With these benefits for lifetime productivity, it’s worth making the most of an investment in a replacement female by establishing reproductive momentum early.

“We need them to calve early just to give them a fighting chance to calve again as a second-calver. We need to select them so that they’re going to become pregnant early in the first breeding season. That probably means selecting them from the cows that calve early,” he said.

“We’d like them to have a calf with little or no assistance, rebreed early in that second breeding season and then hopefully stay in the herd for a longer period of time and wean heavier calves.”

About the author

Field editor

Piper Whelan is a field editor with Canadian Cattlemen. She grew up on a purebred, Maine-Anjou ranch near Irricana, Alta., and previously wrote for Top Stock, Western Horse Review, and various beef breed publications.

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