A cow carries her calf for about 283 days, or roughly 40 weeks, with most breeds landing anywhere from 279 to 292 days. That one number drives the whole calving season: when to pregnancy check, when to change the ration, and when to start watching the pasture twice a day. This cattle pregnancy week by week chart splits those 283 days into three trimesters with day and week markers, so you can find where your cow stands today and what to do next.
Want dates instead of day numbers? Enter the breeding date in our cattle gestation calculator to get the expected calving date and the full 279 to 292 day window for your herd.
Want the deep dive instead? This page is the fast scanning chart: one table, three trimesters, the dates that matter. For breed-by-breed gestation lengths, the biology behind each trimester, and full calving management, read our complete cattle gestation guide.
283-Day Pregnancy at a Glance
T1
T2
T3
Days 1 to 93
Confirm pregnancy
Days 94 to 187
Steady growth
Days 188 to 283
Rapid growth & calving
The 283-Day Chart by Trimester
| Stage | Days / Weeks | What Happens | What to Do |
|---|---|---|---|
| Trimester 1: Days 1 to 93 (Weeks 1 to 13) | |||
| Early embryo | Days 1 to 27 (weeks 1 to 4) | The fertilized egg divides and travels to the uterus, and implantation finishes in the first weeks. This is the highest risk window for silent early embryo loss, so a cow that bred is not yet a pregnant cow. | Hold feed and routine steady. Avoid unnecessary hauling, vaccines, or medication changes. Wait for a confirmed check before counting her in the calving group. |
| First pregnancy check | Days 28 to 45 (weeks 4 to 7) | A PAG blood or milk test reads pregnant from day 28. Ultrasound works from around day 30 and rectal palpation from about day 35. | Book whichever check fits your setup. Results here drive culling, rebreeding, and your projected calving count. |
| Organ formation | Days 46 to 93 (weeks 7 to 13) | The placenta fully takes over and the calf's organs form. The calf is still small, so the cow shows no visible signs. | Maintain body condition on the normal ration. Nothing needs changing yet. |
| Trimester 2: Days 94 to 187 (Weeks 14 to 27) | |||
| Mid gestation | Days 94 to 140 (weeks 14 to 20) | The calf grows steadily but slowly. The cow looks and acts completely normal, which is exactly the point of this stretch. | Consider a mid pregnancy recheck to catch any cows that lost a pregnancy after the first check, especially in herds with a history of late embryo loss. |
| Growth builds | Days 141 to 187 (weeks 20 to 27) | Bone and muscle develop and the calf starts putting on real weight. A slight belly may show on thin or young cows. | Score body condition now. This is your last easy window to bring thin cows up or trim down overconditioned ones before the final push. |
| Trimester 3: Days 188 to 283 (Weeks 27 to 40) | |||
| Rapid growth | Days 188 to 259 (weeks 27 to 37) | Most of the calf's birth weight arrives in this stretch, and the cow's energy and protein needs climb with it. | Step up feed quality gradually. Sort first calf heifers from mature cows if you manage calving ease differently. |
| Udder and countdown | Days 260 to 283 (weeks 37 to 40) | The udder fills and swells over the final 2 to 3 weeks, and the ligaments around the tail head soften in the last days before labor. | Move her to the calving area around day 270 and start checking at least twice a day as the udder tightens. |
The Final Weeks: What to Watch
Three signals tell you calving is close, and they arrive in a reliable order. First the udder fills over the last 2 to 3 weeks, sometimes so tight it looks shiny. Next the ligaments on either side of the tail head soften and drop, usually in the final 24 to 48 hours. Last comes behavior: the cow separates from the herd, paces, or lifts her tail during early contractions. A thick mucus string from the vulva means the process has started.
Move her to the calving area around day 270 so she settles in before labor, then check at least twice daily. Our cattle calving calculator counts down to her due date and flags the day to move her. For the full picture of what calving itself looks like, hour by hour, read our guide to the signs a cow is about to give birth.
Feeding Changes Through the Three Trimesters
Trimesters 1 and 2 are maintenance work: good forage, steady minerals, no dramatic changes. The calf grows slowly enough that pushing feed early just fattens the cow, and overconditioned cows have more calving trouble than fit ones. The real shift happens after day 188, when fetal growth accelerates and energy and protein needs climb week by week. Increase ration quality gradually rather than all at once, keep water and mineral always available, and target a body condition score around 5.5 to 6 at calving. First calf heifers deserve the best feed you have, because they are still growing themselves while growing a calf.
When to Call the Vet During Calving
Cattle calve without help the large majority of the time, but a few situations are time critical. Call if you see strong straining for 30 minutes with no progress, only feet and no nose showing, one leg back, or any presentation that looks like just tail or spine. A foul smelling discharge before calving, or a cow that starts labor signally early (before about day 270), also warrants a call. The general rule: if you are asking yourself whether to call, the cheapest answer is the phone call.
Planning the whole breeding season rather than one pregnancy? Our cattle breeding calendar guide maps when to breed for the calving window you want, the cattle breeding hub collects the season calculators in one place, and printables offers charts you can hang on the barn wall. For breed-level gestation differences, see the complete cattle gestation guide.
Sources & References
- Merck Veterinary Manual: Bovine reproduction and gestation milestones
- Iowa State University Extension: Beef cow pregnancy checking and calving management
- Penn State Extension: Dairy cattle gestation and transition cow nutrition
- Cornell University College of Veterinary Medicine: Bovine reproductive physiology