Calves born in the first 21 days of the calving season are often the heaviest in their contemporary group at weaning, and that advantage often carries through to harvest, if the producer retains ownership. The shorter the calving period, the more uniform those calves are going to be, said Sandy Johnson, beef cattle specialist for Kansas State University Extension.
A defined and shorter breeding and calving season could help producers more accurately time vaccinations, such as a scours prevention vaccination, which needs to be given at a specific interval before calving, Johnson said. Tightening the season also reduces the variation in nutritional requirements within the herd at any one point in time. All of this can help save time and money on herd inputs.
Johnson said as producers consider retaining replacement heifers and rebuilding herd numbers, they should use the opportunity to shorten the breeding and calving season by controlling the duration of bull exposure to the herd, breeding first-calf heifers earlier than mature cows, matching herd genetics to the environment and making committed culling decisions.
Control bull exposure
According to Johnson, well-managed herds achieve pregnancy rates of 90% or greater with 60-day breeding seasons.
"A lot of people, for management purposes, would rather leave the bulls out until they take cows off grass," she said. "I can understand that, but in a way, that's what starts them down this path of allowing later-calving cows to stay in the herd. In most cases, those later-calving cows are not fitting into your system for some reason."
If cows aren't consistently calving early in the season, they probably aren't getting adequate nutrition, Johnson said. This is generally the primary reason cows calve late. The second reason might relate to when they calve as a first-calf heifer.
"First-calf heifers always take longer to resume cycling," she said. "They may take anywhere from two to three weeks longer than their mature cow herd counterparts if they are getting all they need to eat and even longer if they are not, which is often the case."
Treat first-calf heifers differently
For a cow to calve at the same time every year, she has 82 days to re-breed after calving, Johnson said. A typical cow with adequate nutrition takes about 50 days to start cycling again, while a first-calf heifer will take closer to 70 days. Therefore, producers should consider breeding and calving first-calf heifers before the mature cow herd.
Many factors influence the period of time a cow takes to recover from gestation and breed back, including body condition at the time of calving, if she is gaining weight after calving, and if she experienced calving difficulty, Johnson said. She recommends a body condition score of 5 for a mature cow and 6 for a first-calf heifer to keep the herd healthy and breeding back in a timely manner.
"When they calve late as a first-calf heifer, that's a lifetime disadvantage," she said. "We know those that calve during that first cycle as a first-calf heifer carry that advantage forward, and those cows often have an additional calf in their lifetime than those that calve later."
Match herd to environment
Johnson recommends producers plan to provide their highest quality forages to the cow herd after calving and through breeding. However, even this might not help cows breed back early if the quality of feeds can't keep up with how much milk those cows produce, she said.
Cows will first use available nutrients to produce milk, and if nutrient intake is in excess of milk production, then they can put nutrients towards reproduction, she said. If cows are bred to produce a high quantity of milk, reproduction is delayed until the cow is consuming more energy than she needs to produce milk or reaches a positive energy balance.
"We don't all have the same resources as we go across the state," Johnson said. "If we can't get cows re-bred early in our breeding season, part of that message says we don't have the right genetic package for the resource base that we have."
Using bulls with lower milk expected progeny differences, or EPDs, could help producers planning to keep his daughters with more sustainable levels of milk production as replacements.
Commit to culling
Producers might consider keeping a few extra replacement heifers in their system so they can rebuild the herd with the option open of culling out those that are late-bred, Johnson said.
"Use a timely pregnancy diagnosis and strict culling, meaning tell yourself, 'She's pregnant, but she's late. I'm going to market her in a bred cow market, but she's not going to stay in my herd,'" Johnson said.
More information about how to shorten the breeding and calving season can be found in the Kansas State University Department of Animal Sciences & Industry Beef Tips newsletter.