Cattle Breeding Calendar: Heat, AI, Calving, Weaning
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A cow carries her calf for roughly 283 days (the figure the app uses; Nebraska Extension puts it at 280 to 285), cycles every 21 days when she is not pregnant, and must be pregnant again within roughly 80 to 85 days of calving if you want a calf every 365 days. Every step in between has a date, and a missed heat costs three weeks. This calendar puts the timings in order, cites where each figure comes from, and shows what to write down. Your vet knows your herd, so follow their advice where it differs.
The heat cycle
A cow who is not pregnant comes into heat about every 21 days, with 18 to 24 days normal, and standing heat averages about 18 hours, with a range of roughly 6 to 30 hours (Alabama Extension). The signal is short, which makes heat detection the hardest part of breeding.
Signs of heat, in order of reliability:
- Standing to be mounted. Penn State Extension calls this the best sign that a cow is in heat (Penn State).
- Mounting other cows while refusing to be mounted.
- Clear mucus from the vulva.
- Restlessness and nervousness.
- A drop in milk yield in dairy cows.
Penn State advises checking in the early morning, again in the early evening and, if possible, later that evening, and watching for several days either side of the expected date (Penn State).
Record every heat you see, even if you do not plan to breed her. Three observed heats show her own cycle length, so you can predict the next one.
Timing the service
The cow ovulates roughly 25 to 32 hours after standing heat begins, so breeding about 12 hours after you first see her standing puts sperm in place before the egg is released (Penn State). This is the AM/PM rule:
- Standing in the morning: breed that evening.
- Standing in the evening: breed the next morning.
The rule assumes good heat detection. If you cannot watch at least twice a day, ask your AI technician or vet how to set the timing for your herd.
Artificial insemination gives you access to sires you could not afford to own, but it depends on accurate heat detection and a technician you can reach. A bull does the detecting for you, at the cost of feeding him all year and limiting your genetics to what he carries.
The calendar
Day 0 is the service date. Ranges reflect the sources linked below the table.
| Stage | Timing | What to do |
|---|---|---|
| Heat observed | Before day 0 | Record the cow and the time |
| Service | About 12 hours after standing heat starts | Record sire or semen and date |
| Return to heat | About 21 days after service | If she returns, she is probably open |
| Pregnancy check | Ultrasound from about 28 days; palpation from about 6 to 8 weeks | Record the result and who checked |
| Recheck | Around day 60 | Some early pregnancies are lost |
| Late-pregnancy feed | Final 2 to 3 months | Raise feed quality and check body condition |
| Dry off (dairy) | About 60 days before calving | Give her time to recover before the next lactation |
| Calving pen ready | About 2 weeks before the due date | Clean, dry and easy to watch |
| Calving | About 283 days after service | Normal range is about 280 to 285 days |
| Colostrum | Within the first hours | Ask your vet for a target volume |
| Rebred | By about 80 to 85 days after calving | Needed for a 365-day interval |
| Weaning | 3 to 8 months of age | Depends on forage and cow condition |
Sources: gestation and rebreeding window from University of Nebraska-Lincoln; pregnancy testing from Clemson Extension; dry period from Agriland; weaning from Oregon State Extension.
Check every cow for pregnancy
An open cow that everyone assumes is pregnant eats for months and produces nothing. Clemson Extension says ultrasound can detect pregnancy as early as 28 days, and that rectal palpation can be done accurately six to eight weeks after breeding (Clemson).
The same source notes that about 5% of cattle found pregnant at day 30 lose the pregnancy by day 60. Ask your vet whether to recheck.
A cow found open early can be rebred the same season. A cow found open late costs you a year.
Calving
Most calvings need no help. Plan for the exceptions.
Before. Move her to a clean, dry, sheltered pen about two weeks before the due date. In late pregnancy the calf grows fastest, so feed quality and body condition matter now. Know who you will call if she needs help.
During. University of Illinois Extension says healthy cows generally calve unassisted within the first 30 minutes of stage two, and heifers within 60 minutes. If it takes longer, consider assisting or calling a vet (Illinois Extension).
After. Manitoba Agriculture says a calf needs 100 to 200 g of antibodies (IgG) from colostrum, and that its ability to absorb them falls sharply after 12 hours and ends by about 24 hours (Manitoba Agriculture). Its advice is 2 litres in the first hour, and to step in with bottle or tube feeding if the calf has not nursed within 2 to 3 hours. Follow your vet on volumes for your breed.
The cow should pass the placenta within 12 hours. After that it counts as retained, and she needs a vet (Illinois Extension).
Weaning and rebreeding
Oregon State Extension says calves nursing cows are weaned between 3 and 8 months, and that older is usually better. It also says calves can be weaned early when forage is short or the cow is thin, which protects her condition for rebreeding (Oregon State).
Nebraska puts the anestrus period after calving at 40 to 60 days under ideal conditions (University of Nebraska-Lincoln). A cow that has not returned to heat by then is usually a feeding problem before it is a fertility problem. Body condition at calving is the first thing to check, and your vet can help you score it.
What to write down
For each cow, each season, record four things:
- Every heat observed, including ones you skip.
- Service date and sire.
- Pregnancy check result and date.
- Calving date, whether she needed help, and the calf's outcome.
From those you can work out calving interval, which sires give easy calvings, and which cows keep costing you a season. For the wider habit, see the farm record keeping guide. For what culling and calving intervals do to the numbers, see is livestock farming profitable.
Tracking it in Livestock Manager
Livestock Manager has a breeding project for each mating. This is what it does for cattle:
- Parents. You pick the mother and father from batches that track individual animals, so those animals need a profile with sex set. Our lesson on adding animals to a batch shows how.
- Status and due date. You set a breeding status such as Mated, Inseminated, Pregnant or Open. The expected due date fills in automatically at 283 days for cattle, and you can edit it.
- Task schedule. A switch creates an automated schedule with reminders. For cattle it covers pregnancy confirmation at day 30, a second check at day 60, a nutrition adjustment at day 200, calving pen preparation at day 260, a pre-calving check at day 270 and the expected calving date at day 283. Our lesson on farm tasks and reminders shows how they work.
- Events. You log events on the project, and the event types include on heat, artificial insemination, pregnancy check, not pregnant, dry off and weaning.
- The birth. Record Results takes the live and dead calves and lets you add them to an existing batch, create a new batch, or create a profile for each calf. Calves inherit lineage from both parents.
- Pedigree. Each animal's pedigree page shows sire, dam and offspring.
Some breeding features, such as Record Results and the PDF and CSV reports, depend on your plan. The app needs an internet connection. If you also keep goats, the same project type covers goats too; see the goat farming guide.
Frequently asked questions
How long is a cow pregnant?
About 283 days, or roughly nine months and ten days. Nebraska Extension puts gestation at 280 to 285 days, so normal calvings fall within a few days either side. Count from the service date and treat the date as an estimate, not a deadline.
How often does a cow come into heat?
A non-pregnant cow cycles about every 21 days, with 18 to 24 days considered normal. Standing heat lasts about 18 hours on average, with a range of roughly 6 to 30 hours, so checking two to three times a day is what catches it.
When should I inseminate a cow after seeing heat?
The common extension rule is to inseminate about 12 hours after you first see her standing to be mounted. A cow seen in the morning is bred that evening, and one seen in the evening is bred the next morning. Your AI technician or vet may adjust this for your herd.
When can I check whether a cow is pregnant?
Ultrasound can detect pregnancy from about 28 days after breeding, and rectal palpation is accurate from about six to eight weeks. Some pregnancies are lost after an early positive, so ask your vet about a recheck.
When should calves be weaned?
Beef calves are typically weaned between 3 and 8 months of age. Older is usually better, but calves can be weaned earlier when forage is short or the cow is thin.
