Heifers are the future of the cow herd. These young females represent genetic progress, years of investment, and the foundation of the herd’s long-term productivity. But as most ranchers know, despite their potential, they’re also the most demanding to manage. During and after their first pregnancy, proper nutritional management is critical to ensure heifers recover in time to be rebred and remain productive members of the herd.

After delivering their first calf, heifers face a unique set of challenges. The post-calving period is the most nutritionally demanding time in a beef cow’s production cycle—and even more so for a first-calf heifer. They’re both nursing a calf, which demands large amounts of energy, as well as recovering from calving, which at this point is the most stressful event they’ve likely yet experienced. It is important to remember that they are also still growing themselves and must prepare for rebreeding—all while competing with mature cows for resources if they’re run in the same herd.

Because energy is prioritized by the body for basic maintenance first, followed by lactation, growth, and finally reproduction, any shortfall in energy intake can delay or prevent a return to heat. If their nutritional needs aren’t met during this critical window, their likelihood of successfully being rebred that summer will be diminished, and the consequences can ripple through your herd’s reproductive success and bottom line for years.

Heifers vs. mature cows: comparing nutritional needs

On a total pounds of energy and protein basis, the requirements of heifers and mature cows are similar at the same stage of lactation. But the difference lies in intake capacity (Table 1).

Simply put, mature cows can eat more. They have larger rumens and better feed efficiency, which gives them an edge when forage quality is marginal. First-calf heifers, on the other hand, have limited intake—especially around the time of calving. Research from the University of Nebraska shows that intake drops by about 17% in the three weeks leading up to calving, only rebounding to more normal levels roughly a week after calving. That means the diet needs to be more nutrient-dense to meet their energy and protein needs in a smaller volume of feed. In other words, the overall percentage of the diet made up of protein and energy needs to be higher for first-calf heifers than with mature cows. This is why it is a good idea to separate heifers from mature cows leading up to calving, if possible, to manage them on a more nutrient dense feed regimen to avoid underfeeding heifers or overfeeding mature cows.

Assessing body condition to monitor nutrition

Keeping first-calf heifers in adequate body condition is critical. Ideally, they should calve in a body condition score (BCS) of 5 or 6 and maintain that through the breeding season. Lower BCS animals will have a longer postpartum interval (PPI), or the time between calving and coming back into heat. The longer her PPI, the less chance she will have to be bred by the desired time frame. If she is to continue calving year to year, she needs to be rebred within a window of 60 to 85 days.

Unfortunately, many producers see heifers lose weight and fall below this BCS threshold between calving and breeding, reducing their chances of conceiving early—and pushing them into a late calving cycle or out of the herd altogether.

Note: A common misconception is that a first-calf heifer at a lower BCS (below a 5) will lead to a lower birthweight calf and, therefore, fewer calving difficulties. This is not true. Birth weight is influenced more by genetics than BCS and will only decrease slightly if a heifer is kept underweight. Not only can a low BCS worsen calving difficulty and weaken the heifer, but it can also jeopardize her ability to breed back.

(For a better look at how to monitor BCS, refer to the University of Wyoming Extension’s “3-Step Body Condition Scoring (BCS) Guide for Range Cattle: Implications for Grazing and Reproduction” found at wyoextension.org/publications.)

Supplementing a higher nutritional demand

Providing high-quality forage is important, but forage alone often won’t meet minimum nutritional needs—especially in Wyoming herds calving in late winter or early spring. For instance, hay with 58% total digestible nutrients (TDN) and 11% crude protein (CP) might look decent on paper due to the relatively high CP, but it falls short of the 62% TDN required to support lactation and reproduction in first-calf heifers.

That’s why strategic supplementation is critical on Wyoming ranches, where harsh winters and late springs often prevent sufficient forage production from lining up with calving. Energy and protein dense feeds such as distillers’ grains, gluten feed, 20% protein cubes, or alfalfa hay can be used to bridge the gap. Depending on hay quality and supplement type, it may take two to three pounds per head per day of additional energy and protein to meet requirements. Feeding loose by-product supplements can be a challenge in a pasture setting, but studies show that supplement processed into cubes or “cake” shows little wastage.

Alfalfa is a very common supplemental feed in Wyoming. Alfalfa can be a sufficient source of protein and energy when fed with grass hay or pasture. However, it is important to note that alfalfa can still fall below requirements for both TDN and CP. Therefore, it is critical to test each lot of alfalfa hay for nutritive value before relying on it to fill in for what grass hay lacks. For more information on testing hay, refer to “Hay Testing for Cattle: Understanding the Results” available at wyoextension.org/publications. It is also worth noting that much of the CP in alfalfa hay is made up of rumen degradable protein (RDP), rather than rumen undegradable protein (RUP), as is found in higher quantities in by-product feeds. RUP is more efficiently converted to muscle and structural growth and therefore feeds like distillers’ grains or beet pulp may be more beneficial to the first-calf heifer.

Minerals, while often overlooked, are also key components of a balanced diet. With a solid base diet, a good mineral program is essential for reproductive performance and milk production. For a growing heifer that is now producing milk for her calf, mineral supplementation can be critical, especially if forage is lacking.

The payoff is getting it right

**Table 1. Comparison of feed requirements of mature cow and first-calf heifer
	*Cow	*Heifer
Weight	1,200	1,000
TDN, lb.	12.8	12.9
CP, lb.	2.1	2.1
Intake	23.0	20.8
%TDN	55.7	62.0
%CP	9.1	10.1
*Average milk production   **based on the 2016 NRC

 

First-calf heifers that are fed and managed correctly after calving are far more likely to rebreed on time while providing for the calf, stay on the right calving schedule, and become long-term, productive members of the herd. Those that don’t get the nutrition they need are more likely to fall behind or drop out entirely.

Heifers require more labor and feed inputs than their mature counterparts. But when managed correctly, the investment pays off and heifers turn into dependable cows that will raise heavy calves and calve on schedule for years to come. Understand the increased nutritional requirements of the heifer herd, monitor BCS throughout the production cycle immediately before and after calving, and develop a supplement program to meet the heifer’s needs. This will optimize their ability to get rebred and remain a productive part of the beef herd in years to come.

 

The University of Wyoming Beef Team Needs Your Help!

The UW Extension Beef Team started in 2024 as a group of University of Wyoming Extension educators and specialists with an interest in aiding ranching and the state’s beef industry. Our mission is to support Wyoming beef producers in building resilient, profitable operations by providing innovative solutions and fostering sustainable practices through education, outreach, and collaboration. Our plan is to work as a group to provide you as the rancher with relevant and relatable information based on scientific research as well as educational programming that focuses on the topics and challenges most important to Wyoming operations.

In order do this, we are asking for the help of any willing Wyoming producers. You can do this by completing a brief survey at https://bit.ly/3CyaTFK?r=qr. This survey will help us understand not only what key topics ranchers around the Cowboy State would benefit from learning more about, but where in Wyoming each of these topics is more or less prominent, to allow us to tailor programming by region and operation size.

For more questions or suggestions for the UW Extension Beef Team, email Dagan Montgomery at dmontgo8@uwyo.edu. We appreciate your help!

Dagan Montgomery is the University of Wyoming Extension agriculture and natural resources educator serving Sublette County. He can be reached at dmontgo8@uwyo.edu or (307) 367-4380.