By: Katie Allen, K-State Research & Extension News
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 K-State Research and Extension.
A defined and shorter breeding and calving season could help producers to more accurately time vaccinations, such as a scours prevention vaccination, which needs to be given at a specific interval prior to 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 could help producers save time and money on herd inputs.
Johnson said as producers consider keeping back replacement heifers and rebuilding their 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 percent 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’re probably not getting adequate nutrition, Johnson said, which is generally the primary reason why 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 different from mature cows
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 her body condition at the time of calving, if she is gaining weight after calving and if she experienced calving difficulty, Johnson said. A body condition score of 5 for a mature cow and 6 for a first-calf heifer are what she recommends 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 the herd to the environment
Johnson recommends that producers plan to provide their highest quality forages to the cow herd after calving and through breeding. But even this might not help cows breed back early, she said, if the quality of feeds can’t keep up with how much milk those cows produce.
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 (EPDs) could help producers who are planning to keep his daughters with more sustainable levels of milk production as replacements.
Commit to culling
Johnson said producers might consider keeping a few extra replacement heifers in their system so they are able to rebuild the herd while keeping the option open to cull out those that are late-bred.
"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.