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Educator discusses cattle rebreeding success during Farm and Ranch Days

by Wyoming Livestock Roundup

University of Wyoming Sublette County Extension Educator Dagan Montgomery spoke to attendees on Feb. 8 during the Fremont County Farm and Ranch Days in Riverton about cattle rebreeding success in heifers who have had their first or second calf. 

During his presentation he shared some research and studies from several sources which offered tips and best practices to help alleviate some of the issues producers have with replacement heifers. 

Importance of rebreed 

“Reproduction is four times more impactful and profitable than any other production trait,” said Montgomery. “There is a two- and one-half year development period where producers are putting in input efforts before they get any kind of return on their investment when they go to market with the first calf from a replacement heifer.” 

Many producers in Wyoming are familiar with rebreed timelines. For replacement heifers, ranchers will typically breed at 12 to 14 months of age. She will birth her first calf at 22 to 24 months of age. The goal is to then rebreed her at least 82 days or less after her first calf, explained Montgomery.

He noted the reason why producers see one-third or more of their opens as first- and second-calf heifers is due to their longer postpartum interval (PPI) or the extended period from calving to first ovulation.

“Our goal as producers should be to shorten this PPI as much as we can,” he said. 

He added it’s important to remember heifers calving late don’t have a lot of recovery time and are therefore a lot more likely to fail their rebreed or continue calving late throughout their life. 

Overcoming challenges and BCS scores

One of the biggest issues with replacement heifers is they have a higher energy demand than older cows, he shared, and the replacement heifer’s first priority is to recover from birth and then provide milk for the calf they just had. Only if these needs are met can her body afford to be rebred. 

“One of the easiest ways to monitor growth is to make sure they’re gaining as they should by keeping track of body condition scores (BCS),” said Montgomery. “It’s the most influential factor in determining how soon a heifer is going to cycle again after she has calved.” 

He explained ranchers don’t have to go through every animal and write down a BCS number next to their identification tag, but he encouraged producers to pay attention to the herd’s overall BCS and make sure nothing is slipping below a BCS of five or six. 

Additionally, he shared there’s a misconception when it comes to BCS. He mentioned some believe it’s better to have heifers that are thinner, at a lower BCS, during gestation, so when they go to have their calf, it will be smaller, and thus, easier to deliver.

“This really isn’t the case, because genetics is the main thing that’s going to determine how big the calf is when it’s born,” said Montgomery. “All we will do is cause her to be in a weakened state during labor. It’s going to be a lot harder for her to gain weight and keep lactating and get to where she needs to be weight-wise for the next breeding season.” 

He shared a great resource for a three-step BCS guide for range cattle published by UW Extension, which can be found at by clicking on “Publications” and searching “Body condition scoring.” 

Early weaning 

According to Montgomery, calves can be weaned as early as eight weeks old. They can be put on solid feed and don’t need milk, if done correctly. 

“Early weaning can lead to a heavier, healthier replacement heifer by breeding season, increases conception rates and reduces overall forage needs because she doesn’t have a calf to nurse and will stop lactating sooner,” he said. 

However, due to nutritional and health requirements, it’s really labor intensive to separate calves at this age, especially on extensive ranches common to Wyoming, he mentioned. 

“This can be a last-ditch effort if producers have high-end heifers that have gone through a bad year, are really thin and producers need to get them back into the cow herd,” he said. “But, weaning first calves at four to six months is a lot easier and more achievable for most ranchers. This can still provide more days of rest and is going to lead to a better BCS for the heifer by the time she calves for the second time the following spring, placing her in a better position to be at good BCS for breeding in the summer.” 

He said another option some producers have utilized would be to take calves at three months of age, put them into a contained feedlot situation and get them to a higher weight by the time they are seven months old. 

“If it’s something a producer can pencil out and make work, this may be another option,” Montgomery shared. 

Key points 

Montgomery shared with attendees several beneficial key points. 

He has found it can be beneficial to keep replacement heifers separated from the rest of the cow herd. It not only helps focus on their higher nutritional needs, but it can also help breeding success. 

“Separating first- and second-calf heifers from the main cow herd can be extremely beneficial under the right circumstances,” he said. “It can allow a producer to pair a specific calving-ease expected progeny difference bull with their first- or second-time heifers and having them separated can help ranchers pay attention specifically to the BCS of replacements.” 

He noted one of the biggest benefits of having them separated is the ability to keep a good eye on those replacement heifers when calving.

“Roughly 80 percent of an operation’s calving difficulty in the herd will often come from those first- or second-calf heifers,” mentioned Montgomery. “If a first- or second-time replacement heifer needs assistance, and they get help within the first hour of labor, it will help them with breed-back rates later in the fall.” 

In closing, he noted each operation will need to pencil out what will work best for them, but keeping an eye on BCS and providing extra supplementation when needed can help replacement heifers turn into great cows down the road. 

Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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