To get spring calves, you need to breed your cows in summer. Based on an average 283-day gestation, breeding in June produces March calves, breeding in July produces April calves, and breeding in August produces May calves. The exact dates you choose depend on your climate, your forage base, and how early or late you want calves hitting the ground.
Breeding Dates by Target Calving Month
Cattle gestation averages about 280 to 283 days, though individual cows can range from 253 to 300 days. Bull calves tend to run a few days longer than heifers. Using the standard 283-day figure, here’s how the calendar breaks down:
- March calves: Breed June 1 through June 23
- April calves: Breed July 1 through July 23
- May calves: Breed August 1 through August 23
These windows assume a roughly 45-day breeding season, which is a practical target. Research from the University of Nebraska found that a 45-day breeding season achieved 89% pregnancy rates, compared to 84% for a 30-day season and 94% for a 70-day season. A shorter, tighter window gives you a more concentrated calving period, which means less time spent checking cows at night and a more uniform calf crop at weaning.
How Climate Shapes Your Calving Date
Where you ranch matters more than any rule of thumb. In the northern Great Plains, calving in late winter (January) increases calf sickness by 4% and death loss by 2% compared to March or May calving. That’s a strong argument for pushing your breeding dates into late June or July so calves arrive after the worst cold has passed.
In the Southeast, the calculus flips. Heat and humidity during summer breeding can reduce conception rates, so some producers in that region shift breeding earlier to avoid peak summer temperatures. Operations running Brahman-influenced cattle have more flexibility here, but the principle holds: pick a breeding window where neither the cows nor the calves face extreme weather stress.
Producers on federal grazing allotments in the western states often breed earlier, targeting late February or March calving. The goal is to have older, more developed calves by the time cows move to shared summer range. If that’s your situation, you’d be breeding in late May or early June.
Why Later Spring Calving Costs Less
The biggest financial lever in choosing a calving date is harvested feed. A cow that calves in February is lactating through winter, when she’s eating hay and supplement. A cow that calves in May is lactating on green grass, which costs almost nothing beyond the land itself.
Data from a long-running study in Miles City, Montana, puts numbers on this. Harvested feed costs were $185 per cow for February calving, $180 for April calving, and just $70 for June calving. That’s a $110 per cow annual savings by shifting from early to late spring. When you factor in calf revenue, net return over harvested feed costs was $429, $452, and $567 for February, April, and June calving cows, respectively.
The tradeoff is weaning weight. At a common weaning age of 190 days, February-born calves averaged 485 pounds, April-born calves hit 472 pounds, and June-born calves weighed 440 pounds. The gap between February and April is only 13 pounds, though, which often doesn’t offset the extra feed cost. The sweet spot for many operations lands somewhere in the March-to-April calving window, where you’re past the worst weather, approaching the forage flush, and still getting respectable weaning weights.
Breed Heifers Three Weeks Earlier
First-calf heifers need more recovery time after calving before they can breed back. Their period of infertility after delivering a calf often runs 80 days or longer, compared to around 50 to 60 days for mature cows. If you breed heifers on the same schedule as the rest of the herd, many will come up open the following year.
The solution is to start your heifer breeding season several weeks ahead of the mature cow herd. Research shows that breeding heifers to calve three weeks before the cows produces nearly as much benefit as a six-week head start. With that three-week cushion, more heifers get pregnant in the first 21 days of the next breeding season, more stay pregnant through a 60-day season, and total weaning weight improves. If your cows start breeding July 1, put the bull in with your heifers around June 10.
Bull Power and Ratios
A concentrated breeding season only works if you have enough bulls to cover your cows in that window. The general guideline is to match a young bull’s age in months to the number of cows he can handle. A 12-month-old bull can cover about 12 cows, an 18-month-old bull around 18 to 19 cows, and a two-year-old up to 25. Mature bulls in good condition should handle 25 to 35 cows per season.
Get bulls breeding soundness tested at least 30 days before turnout. A bull that fails the exam in mid-June leaves you scrambling if your breeding window opens July 1. Having a backup plan, whether that’s a spare bull or access to AI services, protects you from losing an entire calf crop to one bad exam.
Nutrition in the 100 Days Before Calving
The last 60 to 90 days of gestation are when fetal growth accelerates dramatically. Compared to mid-gestation, a cow’s energy needs increase by 20% and her protein needs rise by 10%. She needs to gain at least 100 pounds during this period to support the calf without losing her own body condition.
For spring-calving cows, this critical window falls in winter. If you’re targeting March calves, you need to be increasing feed quality and quantity by December. Mineral supplementation matters here too: copper, selenium, zinc, and vitamins A and D all support fetal immune system development. Extended cold, wet, or windy weather lasting more than five days can push a cow’s energy requirements up another 10 to 20% on top of the late-gestation increase.
Body condition score is your best management tool. Evaluate your herd at 100 days before calving, which is the last realistic opportunity to add condition to thin cows. Cows scoring below a 4 on the 1-to-9 scale are significantly less likely to cycle during the next breeding season. Your target at calving is a BCS of 5 or better. Separate thin cows from the main herd early and feed them accordingly, because trying to add condition in the last 30 days before calving is expensive and largely ineffective.