For years, the dairy industry has chased one headline target: calving heifers at 22–24 months of age. The logic is clear — earlier calving can boost lifetime productivity, cut rearing costs, and reduce the carbon footprint per litre of milk produced. But as farms race to hit the benchmark, a critical question is gaining attention: are we measuring success by the calendar, while overlooking the development of the heifer herself?
Because reaching the right age means little if heifers are not truly ready to perform.
In some cases, the drive to reduce age at first calving has resulted in underdeveloped heifers entering the milking herd. Survey data from the University of Reading found that fewer than 54% of first-lactation heifers achieve more than 85% of the milk yield of an average third-lactation cow. This highlights the gap between simply meeting a calving-age target and achieving optimal lifetime performance.
The financial consequences of underdeveloped heifers can be significant, including lower milk yields, poorer longevity, and increased replacement costs. Yet the foundations of these issues are often established much earlier in life.
Success begins at birth. Effective colostrum management and timely administration are essential to ensure adequate IgG transfer and the development of a strong immune system. Poor immunity can have lasting effects on calf health, growth, and future productivity.
Rumen development is equally critical. Calves are born functionally as a monogastric, with an undeveloped rumen that relies on early nutritional stimulation to mature correctly. High-quality starter pellets are fundamental during this stage, particularly those formulated with appropriate levels of non-fibre carbohydrates (NFCs). Adequate starch intake promotes rumen papillae development, improves feed efficiency, and supports stronger growth rates and future milk performance.
Research from Calf Notes (Quigley, J. D., Jr. (2021), has shown that calves should consume 15kg of NFC from a starch-rich starter feed before weaning to support the development of a fully functioning rumen. Failure to achieve this intake increases the likelihood of a post-weaning growth check.
This post-weaning check is often where heifers begin to lose momentum. Reduced growth rates during this stage can restrict skeletal development, delay target weight achievement, and ultimately limit lifetime productivity. While many heifers may still reach the appropriate age for serving and calve at 24 months, too many fail to achieve the recommended target of 55% of mature body weight by their bulling period.
Developing heifers successfully is about far more than simply hitting a calving deadline. It requires maintaining consistent growth and nutrition from birth through weaning and right up to the bulling period. Yet too many heifers lose momentum along the way — particularly during the summer months when they are turned out to grass and often receive less attention nutritionally.
In reality, how many farms rearing heifers are weighing their replacements on a regular basis?
If the industry is serious about achieving earlier calving without compromising performance, greater focus must be placed on sustaining growth rates and monitoring this progress throughout the rearing period, using real on farm data. Heifers should be managed to achieve 0.8kg of daily liveweight gain in order to reach the recommended target of 55% of mature bodyweight at service. By doing so, farmers can ensure heifers enter the herd at the correct size and condition, rather than forcing animals to ‘catch up’ during their first lactation — a challenge that can limit both productivity and long-term performance.
Ultimately, the success of a heifer-rearing system should not be judged solely by the age at first calving, but by the quality of the heifer entering the milking herd. Earlier calving only delivers real value when heifers have been developed correctly from birth through to service, reaching the right growth and weight targets along the way. When that foundation is in place, heifers are far better equipped to achieve high levels of production, fertility, health, and longevity throughout their lifetime.
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