Defined breeding season: Simple yet important strategy

Introduction

Albert Einstein is often credited for saying, “Everything should be made as simple as possible, but no simpler.” So, what does Einstein have to do with breeding beef cows?

The simplest recommendation we can offer to cow-calf producers is to have a defined breeding season length, which in turn sets calving season length. Open-ended access to the herd sire can lead to year-round calving, and no consistent plan for when to wean and market calves.

Defined breeding season

Having a defined breeding season, which also then sets the calving season, offers several advantages. Cows are closely grouped at a similar stage of production to balance rations and implement herd health practices. Shorter calving seasons concentrate the time demands for extra labor and attention to calvings, ensuring calves get off to a good start. There is also greater potential to market a uniform group of feeder calves based on their age and weight. 

Defined breeding seasons can range from 45 to 90 days; longer seasons of 120 to 180 days are also observed. If we assume an average estrous cycle length of 21 days and cows are cycling at the beginning of the breeding season, a 45-day breeding season provides cows with two opportunities to become pregnant. Longer breeding seasons spread out calving but offer more opportunities for cows to breed. 

Despite the upsides of controlling breeding and calving season length, a 2017 USDA survey found 58% of farms do not have a set breeding season (defined as removing the bull for 30 days or more). Differences existed by herd size, with the following reporting not having a defined breeding season:

• 64% of farms with one to 49 cows 
• 44% of farms with 50 to 199 cows 
• 26% of farms with 200-plus cows 

Determine length of breeding season

This “simplest recommendation” is not specific, though, and does not inform the length of the defined breeding season once a producer has changed his or her management practices to remove the bull. Differences in how calves are marketed and options for cows that do not conceive make this decision unique to every farm. This can become a balancing act of testing how short you can go, without going too short. 

While the advantages outweigh the negatives, Beard, McCarthy and Mulliniks from the University of Nebraska Extension beef team point out how shortening the defined breeding season can come at the expense of having to market more cows due to reproductive failure. A shorter defined breeding season requires you to be at the top of your management game and pay attention to details like body condition scores, nutrition and pasture management, minimizing the incidence of dystocia and retained placentas, and more. 

Questions all farms should ask include:

• What are the marketing options for cows that do not conceive during the defined breeding season? 
• Is there an opportunity to introduce a second breeding season for fall calving? 
• Are there opportunities to continue breeding but market pregnant cows that fall outside of your desired calving season? 
• Do you have a marketing plan for open cows? 

Each farm needs to assess the pros and cons of shorter vs. longer defined breeding seasons. For example, a farm that markets all feeder calves may opt for a more aggressive, shorter breeding season to more closely group and optimize the value of feeder calves. Conversely, a farm that retains ownership and direct-markets may have opportunities to capture value from later-born calves resulting from a longer breeding season. In both examples, consideration should be given to what opportunities do or do not exist to market cows that fail to conceive in the defined breeding season. 

Track reproductive performance against changes you make to breeding season length. For example, first-calf heifers may have a harder time conceiving during a shorter breeding season. In that case, you need to assess whether changes to management can improve reproduction, or if a longer defined breeding season better suits your herd.

Consider the long-term value of placing selection pressure on cows that do not perform in your environment by removing cows that do not conceive during the defined breeding season.