Management is far from over after heifers calve
Producers who raise their own replacement females invest a significant amount of time and money to develop them to the point they are first-calf heifers. While getting those first calves on the ground is quite an achievement, the need to closely manage the females is far from over. In fact, the greatest challenge may still be ahead.
“It should be recognized by most experienced producers that first-calf heifers are the hardest to get bred back. That is largely because they are not only recuperating from calving, but they are dealing with the stress of caring for a newborn for the first time, producing milk for the first time, and still growing,” David Lalman, Ph.D., professor, and extension beef cattle specialist at Oklahoma State University, said.
A critical driver in reproductive success of beef cows is the postpartum interval (PPI), the time between calving and resumption of the estrous cycle. “Years of research data clearly show that first-calf heifers have a one to four-week longer PPI, when other factors are held constant,” Lalman said.
According to Lalman, longer PPI in first-calf heifers suggests that fewer would be cycling by the beginning of the breeding season, a greater percentage would become pregnant later in the breeding season, and (or) more would be open after a 60-to-90-day breeding season. Additionally, most first-calf heifers in a commercial setting should weigh about 80 to 85 percent of their expected mature weight after they calve the first time. “Consider first-calf heifers are still growing at the same time they are on this steep learning curve, and you can understand why their fertility is more fragile than a mature cow,” Lalman said.
Managing First-Calf Heifers
The proper management of first-calf heifers plays a critical role in their ability to breed back for a second calf. “First and foremost, years of research clearly indicates that the most critical factor in breed-back success of first-calf heifers is their body condition the day they calve. Thin condition at calving compounds the extended PPI problem in first-calvers while good body condition at calving minimizes the PPI. This is why extension specialists and scientists advocate to manage first-calf heifers to calve in a body condition score of 6 on a scale of 1 to 9,” Lalman explained.
Next, heifers should be managed to maintain condition after they calve. “Second to condition at the time of calving, weight and condition change after calving influences the PPI as well as first-service conception rate,” Lalman stated. Ideally, first-calf heifers would be managed to experience a stable or slight positive plane of nutrition after they calve. “The last thing you want them to experience is rapid weight and condition loss,” Lalman added.
Beef extension specialists recommend producers separate first-calf heifers from the mature cow herd if possible. When treated like mature cows or run with them, the first-calf heifers generally lose weight. The first-calf heifers’ higher nutrient demands per body weight coupled with their lack of dominance when competing with older cows for feed or supplement, puts them at a nutritional disadvantage.
“If they are getting a supplement as a group, they are just not going to get their fair share,” Lalman stated. “So, it is common for them to lose weight and condition post-calving, unless they are managed separately.”
Impact on Calves
If a first-calf heifer calves in thin condition or loses weight and condition after calving, then not only could it impact her ability to breed back but it also could affect the health of her calf. A first-calf heifer’s plane of nutrition influences milk yield and the concentration of immunoglobulins in her first-milk or colostrum. These immunoglobulins are critical in establishing the calf’s early immune system. If the heifer is in good condition at calving and maintaining or slightly gaining weight after calving, her milk production and milk nutrient content will be close to optimal.
However, if the first-calf heifer is struggling nutritionally, so will her calf. “If she is losing weight, milk yield goes down, milk immunoglobulin concentration and nutrient composition goes down. Taken together, the influence of nutritional status of the dam on calf health is clear; if the mother is undernourished and losing condition, her calf is going to be undernourished,” Lalman said.
Proper Care Pays Off
Extension beef cattle specialists suggest producers prioritize ensuring first-calf heifers receive adequate nutrition. A first-calf heifer should calve in good condition and producers should implement strategies to help the first-calf heifer hold her good condition until she weans her calf.
Taking special care of first-calf heifers will pay off for producers in the long run. “Once you get them to the pregnant heifer stage, you have invested a lot of time and money in their development. Now is not the time to pull the rug out from under them from a nutritional standpoint. That can result in a 60 or 70 percent pregnancy rate,” Lalman said.
In contrast, it is a good idea to challenge replacement heifers during the early development stage, between weaning and first breeding. “For example, keep more heifers than you expect to need for replacements, develop them to weigh about 60 percent of their expected mature weight by the beginning of the first breeding season, then expose them to a short breeding season. Keep the heifers that get pregnant and sell the ones that do not get pregnant,” Lalman said. This strategy ensures that retained heifers are fertile and a good fit in your production system, while minimizing development costs. But once they are pregnant, producers should manage these young cows to calve in good condition and maintain good condition through that second breeding season.
