Developing heifers to target weight improves pregnancy rates, longevity

Managing heifers nutritionally can be challenging for producers, and it is incredibly important for the productivity of the heifer later in life, comments an Idaho Extension specialist.

“Certainly we’ve got a lot of opportunities to influence the nutrition of heifers are various times of their lives, whether they are pre-weaning or post-weaning, but the other challenge we have is that there’s a lot of different environments in which we have to raise cows. She has to work as a cow, so that also influences how we develop those heifers,” says University of Idaho Beef Extension Specialist John Hall.

Time of pregnancy

Hall emphasizes that a pregnant heifer is not the same as an early pregnant heifer.

“There’s a significant advantage in getting those heifers pregnant early in the breeding season,” he says, citing research from the U.S. Meat Animal Research Center by Cushman, et. al. in 2013. “Those heifers that became pregnant in the first 21 days of the breeding season had greater longevity, stayed in the herd longer, produced more calves in their lifetime and produced more pounds of calf.”

“Getting those heifers to breed early in their first breeding season is the key to lifetime productivity,” Hall comments. “Certainly one of the ways we can control that is through nutrition.”

Nutritional impacts

Ensuring that heifers are pregnant early begins prior to weaning.

“The pre-weaning phase is not a phase we have a lot of control over,” Hall says. “It tends to be influenced by the milk production of the dam and the forage availability during the time of year that the calf is on its mother.”

He continues, “We do know from research that those animals that are heavier at weaning are the ones that tend to come into heat sooner and breed more effectively throughout the course of the year.”

At the end of the day, heifers that gain more from birth to weaning also tend to breed early in the breeding season.

As a result, early weaning can have positive impacts on heifers because producers have more control over the heifer’s diet at that point.

Hall notes that, after looking at several studies, heifers that are weaned between 90 and 100 days, then put on a high-concentrate or high starch diet and managed the same as their counterparts often reach puberty earlier and have higher pregnancy rates.

“That tells us that the pre-weaning phase is a critical time in the heifer’s life,” Hall says. “That nutrition that she is exposed to can affect her subsequent reproduction for the rest of her life.”

“It’s key for us, as managers, to keep track of that,” he adds.

Pre- and post-weaning

“The pre-weaning phase is a critical phase for the heifer,” Hall says. “It’s an important phase in terms of her reproductive life and one we don’t have a lot of management strategies for, but it’s certainly one we have to think more strongly about.”

However, post-weaning phases of the heifer’s life is the one that producers have control over, and it has also been studied intensively.

Looking at research, Hall says that many studies have clearly demonstrated that limiting nutrition can delay puberty, which increases the likelihood that they will have trouble getting pregnant, resulting in long-term reduction in reproductive rates.

“On the other hand, if we have a program in which rates of gain are better for heifers, we see those heifers perform well,” he explains. “These studies gave us the recommendation that heifers need to gain between 1.25 and 1.75 pounds per day from weaning until breeding to reach the proper weight.”

Feeding strategies

Another aspect that studies have looked at is the merit of feeding heifers in a big group compared to in several smaller groups by weight.

“If we split them into two separate groups and feed them according to their size, studies have shown that not only do those lightweight heifers have an advantage, but we have also grown them most appropriately for their target weight,” Hall explains.

The result, he adds, is higher pregnancy rates across the herd.

“When we have big heifers and little heifers in the pen, the big heifers get over-fed, and they get more fat,” he says, noting that, at the same time, smaller heifers are underfed.

Staggered feeding

Feeding heifers can be expensive, but Hall notes that they do not have to be fed on a steady plane from weaning until breeding.

“Can we kind of rough them through the winter when the weather is cold and it’s expensive to feed and then push them along before spring comes?” he asks. “There’s a number of different studies, but across all those studies, it didn’t matter whether it was slow, even gain or slow, then fast gain before the breeding season in a stair-step method. There’s no statistical difference between the heifers.”

As long as heifers reach their target weight, Hall says it is less important how the heifers get there.

In some fairly new data, Hall also says that there are may be advantages to using a stair-step method to feeding heifers, though the research needs to be done to confirm that research.

“From the dairy industry, we now see that the stair-step method prevents adipose tissue in the udder, so, therefore, it allows milk production to be better,” Hall comments. “There does seem to be some advantage over an even gain methodology.”

“As managers, we can use that to our advantage to decrease feed costs, increase profitability and still maintain heifer productivity,” he notes.

Hall spoke during the 2016 Applied Reproductive Strategies in Beef Cattle Workshop, held in Des Moines, Iowa on Sept. 6-7, 2016.

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at saige@wylr.net.