Market costs for replacements are at an all-time high, ranging between $3,000 and $4,000 per head. Iowa State University Extension calculated heifer raising costs in 2024 to be just over $2,600 for 24 months. The difference in the expenses provides a financial opportunity for dairy farms that can raise their own replacements. Heifer inventories need to ensure that herd size is maintained. The amount of heifers needed on the dairy to maintain herd size is highly impacted by age at first calving and herd culling rates.
Age at First Calving
Heifers are unique to the farm in that they are the future of the dairy farm but do not provide income to the farm until they have their first calf. The optimal first calving age ranges between 22 and 24 months. According to Iowa State estimates, reducing the age at first calving by a month will save the dairy $93 per heifer. However, research has shown that calving too early (< 21 months) would hurt profitability in the long run because heifers would not reach their full milk production potential.
Proper growth rates are extremely important to reach optimal age at first calving. Body weight determines when heifers reach puberty, around 45 to 50% of mature weight. Too low of average daily gain can delay puberty, which then will have a snowball effect by delaying time to first breeding and age at first calving.
Delaying the age at first calving costs money and increases the heifer inventory needed to maintain herd size. A herd of 100 milking cows needs 5 to 6 more additional heifers for every two-month increase of age at first calving when their culling rate is 30%.
Culling Rate
To no surprise, the rate at which animals leave the herd has a significant impact on the replacement inventory. A herd of 100 milking cows with an age of first calving of 24 months needs an additional 4 to 5 heifers with every 2% increase in culling rate. Therefore, increasing the culling rate from 22% to 32% would require 22 additional heifers to keep the milking herd size at 100.
High market prices for heifers can significantly increase farm income for farms with excessive replacements. However, heifer inventories should be monitored closely. Small changes in culling rate and age at first calving significantly impact the number of replacements needed.
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