Providing younger mothers with the right nutrition is key to rebreeding success

Getting first-calf heifers rebred can be a challenge, but it’s not impossible.

University of Missouri Extension Livestock Field Specialist Randall Weidmier said first-calf heifers are still maturing when they have their first calf, so their nutritional needs differ than that of mature cows.

A first-calf heifer is expected to breed, carry a calf and produce enough milk to support that calf by the time she is about 2 years old, yet she will not reach full maturity until about the age of 4, Weidmier said. He added that a first-calf heifer at peak lactation requires about 60 percent TDN (Total Digestible Nutrition), when a mature cow requires about 3 percent less.

“It’s what we call the partitioning of energy,” Weidmier said. “In a mature cow, they really don’t have that partitioning to body weight gain. The energy used for body tissue synthesis is used fairly inefficiently; it takes a lot of energy to put on a pound of gain on an animal. Usually the rule of thumb is that it takes 4 pounds of TDN per pound of gain. The heifer has a given amount of energy coming into her diet and she’s going to partition that for the most important things. Unfortunately, Mother Nature says reproduction is not the most important of those functions, and Mother Nature just kind of sets them up so they won’t self destruct and says, ‘you won’t be reproducing this year.’”

First-calf heifers are at the lower end of the pecking order in a herd, so older cows may push them away from hay and feed sources. Mature cows can also eat more feed compared to younger females. Research conducted at the University of Nebraska reported in the 2004 Nebraska Beef Report indicates that a first-calf-heifer within three weeks of calving experiences a 17 percent decrease in daily feed intake. Intake is re-established to more “normal” levels by about one week after calving.

“That’s why we recommend separating those animals out, so that they can be fed separately, and not have the competition and have a diet that more closely matches their requirements,” Weidmier said. “It does pay dividends if you can separate those first-calf heifers out and they can be fed separately. If you have that better lot of hay, it would be more efficiently used with those first-calf heifers than to go to the mature cows.”

He added that many producers do not have the facilities or time to separate herds.

“We just run those cows and heifers together and then we find out that only 60 percent of those first-calf heifers rebred,” Weidmier said. “A lot of times, if you are trying to make genetic improvements in your herd, those first-calf heifers are actually your best genetics. It’s a shame not to put the resources into them so that they can express their genetic potential.”

Since it is nearly impossible to monitor the intake of each animal, producers can evaluate how their first-calf heifers are holding up by evaluating body conditions.

“A lot of times we can’t weigh them, so we just have to use the Body Condition Scoring system. The BCS system says we can have a mature cow calve at a score of 5, then her chances of rebreeding in an 80-day window are fairly high,” Weidmier said. “For the producers I work with, I recommend to have heifers have their BCS at 6 when they calve. That gives them a little bank account, about an 80-pound bank account, to work with in case they aren’t getting adequate nutation from the diet, which is kind of common. If producers just get into the practice of doing that when they go out as a few heifers or cows go by, think ‘What would I score that cow? What would I score that heifer?’ and be mindful of that. You might say, ‘I need to put a few more resources into them.’”

First-calf heifers will often need more time to recover after calving, so it’s beneficial for the initial breeding to be earlier than the mature herd.

“The Beef Herd Improvement Federation recommends that,” Weidmier explained. “If we can start breeding those heifers 21 days, a full cycle, before the mature cowherd, they can catch up on that postpartum interval. That means you have to have a lot of your heifers in puberty by 13, 14 months of age and that is quite a challenge at times.”

Heifers born earlier in the calving season are a little more likely to breed and are offspring of the most fertile cows. This makes them a little more mature for earlier breeding.

While many producers want those heifers to become mothers at the age of 2, waiting a little longer to breed first-time heifers may be a better option.

“There has been some studies where it does help improve the overall productivity of the herd if we can give those heifers an extra six months,” Weidmier said. “That kind of works in our part of the country because so many of our producers have a spring and a fall herd. Moving those spring-born heifers to the fall herd would give them an extra half a year to develop and they wouldn’t have the nutritional stress a 2-year-old would have.”

Weather conditions should also be considered a factor during the rebreeding process, and recent bitter cold weather could result in slow conception.

“The wet hair coat of an animal can affect how much energy they have to have to maintain their body temperature,” Weidmier said.

“With a good winter coat, which most of our cattle have this time of year, our lower critical temperature is about 32 degrees. What that means is (the temperature) can get down to 32 degrees and (a cow) not have to burn any extra energy. Once that coat is wet and loses its insulation factor, that jumps all the way up to 59 degrees. In cold, wet conditions like we have had this winter, it takes 7 more pounds of hay to deal with the weather. Then when you have cows wading through the mud, it’s been shown that their dry matter intake can drop and start losing condition pretty quickly. That will just be extenuated with those heifers.”

To keep condition up in heifers, Weidmier said adding a little feed will go a long way.

“Although hay prices are just astronomically high, we had a good corn crop,” he said. “Eric Bailey, the state Extension beef specialist, was down a while back and he showed the producers that it was costing 16 to 18 cents per pound of TDN with hay. With a lot of the corn byproducts, like distillers dried grain and corn gluten meal and those types of things, the cost per pound of TDN was only 12 cents; considerably less than TDN coming from hay. That’s helped a lot of producers this year by substituting the hay with these high-energy corn byproducts because it has been a real blessing.”


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