One Year, One Calf
A dairy cow should give birth to one calf every 12 months. A cow carries her calf for about 280 days, so she must conceive within about 85 days of calving to keep to this target. A calving interval of 12–13 months gives the most milk and the most calves from each cow over her lifetime. Every missed heat delays the next calving by 21 days.
Buffalo: gestation is about 310 days, so a 13–14 month interval is a practical target.
Key Target
| Parameter | Target |
| First service of heifer | 15–18 months of age or 250–280 kg body weight |
| First calving | About 24–27 months |
| Heat cycle | 21 days (heat lasts about 18 hours) |
| First service after calving | 60–90 days |
| Conception after calving | Within about 85 days |
| Gestation (cattle) | About 280 days |
| Dry period | 60 days before the next calving |
| Calving interval | 12–13 months |
The Yearly Cycle
| When | What to do |
| When | What to do |
| Calving (Day 0) | Give the calf colostrum within one hour. Check that the placenta drops within 12 hours. Keep the cow clean, comfortable and well fed. |
| Day 1–45 | Raise concentrate gradually as milk yield rises. Watch for milk fever, ketosis, retained placenta and uterine infection, and call the veterinarian early. |
| Day 45–60 | Watch for the first heat and record it. Have the cow examined if there is any abnormal discharge. |
| Day 60–90 | Inseminate in heat using the AM–PM rule. Aim for conception by about Day 85. |
| 21 days after AI | Watch for a return to heat. If the cow returns, rebreed in that heat. |
| 60–90 days after AI | Confirm pregnancy with a veterinarian. Examine and rebreed open cows without delay. |
| About Day 305 | Dry off the cow, 60 days before calving. Feed the dry-cow ration and deworm. Give 1.5–2 kg extra concentrate in the last two months and move her to a clean calving pen a week before calving. |
How to Achieve
- Detect heat early. Observe the cows for 30 minutes in the early morning, evening and at night. Keep a record of every heat date.
- Inseminate on time. Use quality semen and a trained AI technician, and follow the AM–PM rule.
- Feed for reproduction. Give a balanced ration with green fodder, 30–50 g mineral mixture daily and clean water. Avoid cows that are too thin or too fat at calving.
- Protect health. Vaccinate and deworm on schedule, control mastitis and ticks, and treat post-calving problems early.
- Keep records. Note calving, heat, AI and pregnancy diagnosis dates, the semen used, and the dry-off date for each cow.
Common causes of delayed calving
| Problem | What to do |
| Missed or silent heat | Observe the herd two to three times a day and keep heat records. |
| Poor nutrition or mineral deficiency | Provide a balanced ration, green fodder and mineral mixture every day. |
| Uterine infection after calving | Get cows with retained placenta or discharge checked early. |
| Wrong AI timing | Follow the AM–PM rule and use a trained technician. |
| Repeat breeding (3 or more failed services) | Get a complete veterinary examination before the next service. |
| Heat stress | Give shade, fans or sprinklers and plenty of drinking water. |
Benefits
- More calves and more milk from each cow over her lifetime.
- Lower cost per litre because there are fewer unproductive days.
- Steadier income and a regular supply of quality replacement heifers.
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