When to inseminate a heifer: age and weight
If a heifer is already 12 months old but has not reached her average weight, it's important to determine the cause. We evaluate her genetics (which dam and sire she was bred from)—if this is the case, she should be nursed. Until what age? Statistically, the best percentage of productive insemination (over 75%) is achieved in heifers aged 14-16 months (by 20 months, the percentage of productive insemination drops by approximately 35%). This means we nurse her to 14-16 months and inseminate her. If the underweight is due to illness, the animal is culled.
At insemination, the heifer should have a body condition score of 3.0, and by the time of calving, heifers will weigh approximately 85-90% of an adult cow (the latter is better), with a body condition score of 3.5-3.75. For insemination of heifers, it is recommended to select semen from proven bulls with "easy calving" characteristics and small fetuses.
Farmers are gradually shifting to later insemination times due to changes in the recording system. The emphasis is now on productive lifespan, and one of the key indicators is the amount of fat and protein produced throughout the cow's productive life. Cows inseminated at 16-18 months (for Holsteins) live longer, and they produce more fat and protein over their lifetime.
This technology is beneficial for farms with proper feeding and good management.
For farms where cows live for two or three lactations, it is more profitable to inseminate earlier.
Insemination timing depends on the farm situation, breed, feed quality, technology and management, and the goals set.
✅Conclusion: Therefore, at the time of the first insemination, the heifer should be over 12 months old and have a body weight of 60-70% of the adult body weight of a given breed. Over-insemination with age, as well as overfeeding, will complicate insemination, the conception rate will decrease, and the number of culled barren heifers will increase.