A long-debated topic in the dairy industry has been breeding heifers. When is the right time? Should we look at age? Should we look at size? What method is the most financially sound? Generally speaking, your heifers should represent the best genetics on your farm, in addition to being the most fertile group. Breeding heifers at the right time can allow farmers to take full advantage of this valuable resource.

Data from over 13,000 dairy farms indicated that the average calving age for DHIA herds ranged from 25 to 27.3 months across breeds (Dairy Records Management Systems, DRMS). The minimum age at first calving was 20 months; the maximum age was 30 months. The same research followed the heifers through their first lactation, and those that calved in earlier (less than 24 months of age) had higher milk production and components. Evidence from older studies indicated that heifers that calved at older ages produced more milk in their first lactation, but when lifetime yields were calculated, heifers calving at younger ages produced more lifetime milk.

Dr. Paul Fricke with the University of Wisconsin-Madison put together a great comparison of calving heifers at three different ages: 20 months, 24 months, and 32 months. The heifer calving at 20 months would hit puberty at 9 months and conceive around 11 months of age. Her non-lactating time is much shorter, which saves money on the front end. However, her mammary development is impaired and results in lower milk production in the long run, thus losing money on the back end. Heifers that calve at 19 to 21 months can have a higher risk of dystocia and metabolic disorders.

A heifer that conceives around 14 months will calve at 23 to 24 months. She will spend 2 years as a non-lactating animal but will be at an optimum age to have a good first lactation and strong subsequent lactations. Calving at this age also benefits future reproductive performance. Another benefit is that it increases the asset turnover ratio and financial efficiency of the dairy because fewer replacements are needed to meet internal replacement needs.

A heifer that conceives at 23 months will calve at 32 months and spend over two and a half years as a non-lactating animal. Each day calving is delayed beyond 24 months costs $1.50 to $3.00 per heifer. While waiting until 32 months to calve in heifers does not seem likely, waiting until just 27 months could cost a farm $135 to $270 per heifer. Even calving at 25 months has the potential to cost $45 to $90 per heifer. It may not seem like much, but multiplied by dozens of heifers over several years, it can quickly add up.

All of the collective data points toward the ideal age to breed heifers, but there is another piece to the puzzle. There are also size recommendations to consider when breeding heifers. As mentioned above, puberty in heifers usually occurs around 9 months of age. However, the onset of puberty is size- and development-related, so it may occur earlier or later than 9 months. Puberty depends on a heifer's nutrition and average daily gain. Puberty, therefore, may be delayed or accelerated based on how heifers are fed and managed.

One tool farmers can use to track their heifers' growth is body condition score. Using the 5-point scale, a BCS of 2.5 to 2.75 is ideal for heifers from 3 months of age to puberty. After puberty, and up to the time of breeding, a BCS of 2.75 to 3.0 is desirable for optimal fertility. At calving a body condition score of 3.25 to 3.5 is acceptable. Using size measurements, general recommendations for Holstein heifers for breeding are a weight of 875 pounds and a wither height of 50 inches. For calving, general recommendations for Holstein heifers are 1250 pounds and 55 inches.

Heifers are an important part of any successful dairy operation. They serve as replacements, help advance genetics, and their fertility is vital to successful reproductive management. By recognizing the economic impact of calving heifers at the right time, dairy farmers can ensure they are capturing the most profit from this valuable group.