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Anestrus in Beef Cows

Anestrus means a cow is not showing heat or cycling. In beef herds it is most often tied to nutrition, calving condition and the time since calving.

What anestrus is

A cow in anestrus has no regular estrous cycles. She will not show heat, and she cannot be bred successfully until cycling resumes. The estrous cycle in a normal cow averages about 21 days.

Anestrus is common in the weeks after calving, when cows normally pause to recover. It becomes a problem when the pause is long enough to push the cow out of your breeding season.

The length of the pause varies. It depends on condition, age, suckling and season, so two cows in the same pasture can resume cycling weeks apart. Some anestrus is normal and brief, so judge it against your calendar. The question is whether the cow will be cycling in time to rebreed within your season.

Common causes in beef cows

The leading cause is poor body condition, often from inadequate feed during late pregnancy and early lactation. Other factors include suckling by the calf, young age, the stress of a first calf, disease and, in heifers, being too light at breeding.

Environmental stress, heat and poor-quality forage can contribute. Cows that calve late in the season have less time to recover before breeding.

Older cows can also lose condition fast in a hard winter, so do not look only at the young ones.

• Low body condition at calving or after
• Suckling effect from the calf
• First-calf heifers still growing
• Stress, illness or poor forage
• Late calving date

Nutrition and condition

Body condition score on the 1 to 9 scale helps you judge where cows stand. Cows that calve too thin often take longer to resume cycling. Feeding after calving has limits, so it is best to get condition right before calving.

Work with a nutritionist or extension specialist to plan feed for each group, including first-calf heifers. Ask for condition targets that fit your breed, region and forage.

First-calf heifers need extra attention because they must support their own growth, milk and rebreeding at the same time.

The role of the calf and management

Suckling slows the return to cycling in beef cows. Some herds use temporary calf removal or other management approaches. These affect calves and cows, so talk to your vet about what fits your herd and about welfare considerations.

Do not use hormone products without veterinary direction. Treatment plans, products and timing are the vet's decision, and withdrawal times must be followed exactly.

Be careful with any shortcut. Shortcuts that save a little money on feed can cost a whole calf crop.

• Ask your vet about management options
• Do not use hormones without a veterinarian
• Protect calf welfare and nutrition
• Record each cow's calving and breeding dates

Diagnosing the cause

Your veterinarian can examine cows to see whether they are cycling and rule out disease or reproductive tract problems. Records of calving dates and condition help find a pattern.

If many cows are anestrus, the cause is probably nutritional or managerial. If just a few, look at each individual.

Records of calving date and condition help. A cow that calved thin and late is a likely candidate, while a cow that calved on time and in good condition and still does not cycle needs a closer look.

Prevention

Plan feed so cows reach calving in good condition. Calve in a window that matches forage. Use a defined, short breeding season. Develop heifers properly so they calve at a good age and size. Cull cows that repeatedly fail to cycle on time.

Check bulls too, since a poor bull can be mistaken for anestrus cows.

Plan the weaning date with your vet and nutritionist. Cows that stay in good condition through late lactation are better placed to rebreed the next year. Keep notes on the cows you suspect and review them at pregnancy check, when you can see which ones stayed open.

Common mistakes and what to ask

Mistakes include waiting too long to check cows, blaming genetics before nutrition and using hormones without a vet.

Ask your vet: Are these cows cycling? What is the likely cause? What management changes would help? Ask your nutritionist for a feeding plan before calving, and your extension office about calving season timing.

More in Breeding, Genetics & Reproduction

• Cystic Ovaries in Cattle
• Fertility and Body Condition
• Nutrition and Rebreeding
• Calving Distribution Analysis
• Calving Season Planning
• Calving Ease and Dystocia