“I don’t know about you, but I’m feeling 22.” You might be wondering why an article on heifer raising is starting off with lyrics from a popular Taylor Swift song, but that line from her 2013 song describes a lot of themes around setting goals and optimizing heifer raising. When asked “What age do you want to calve in your heifers?” many producers may very well repeat that exact line. Too often, goals for the heifer-raising enterprise are based around feelings and traditions, instead of facts and figures. So that begs the question: How then should a producer set goals, monitor and manage the growth of their heifers? To properly do that, the size of the farm’s mature cows needs to be quantified, whether that is by a weigh tape, a scale in the robot or averaging the weight of some cull cows. Many of the goals for different stages of calf/heifer growth can be made based on the current mature body size of the herd, as seen in Table 1, or what the producer desires the size of the herd to be.
Zero to 2 months
The first two months of the calf’s life will impact the remainder of their productive life. There are many targets in those first 60 days, but they can be summed up in these three main points:
1. Promoting good health – The impact of bovine respiratory disease (BRD) on raising costs and future production is immense and cannot be emphasized enough. A complete review of colostrum and nutrition management, bedding, ventilation, housing, stocking rates, vaccine protocols, etc., is needed if BRD challenges exceed 5%.
2. Promoting optimal gains – Healthy, well-grown calves have a target to double birthweight by 2 months old or, preferably, reach 13% of mature bodyweight (MBW).
3. Initiating rumen development – Sufficient rumen development is necessary pre-weaning to maintain optimal rates of gain post-weaning on a dry feed diet. Rumen development is best stimulated by the consumption of dry starter feeds containing easily digestible carbohydrates, typically grains, as they are energy-dense and consistent, driving gain and rumen papillae development. Higher dry matter intake (DMI) of starter at weaning is significantly correlated to higher intakes post-weaning and results in higher future milk yield (+290 kilograms fat-corrected milk in first lactation for every 1 kilogram of DMI at weaning). For operations feeding high levels of milk, proper weaning protocols need to be in place to allow for sufficient starter intake prior to weaning. While previous recommendations have suggested that calves are ready to be weaned when consuming at least 1.5 kilograms of starter per day, to maintain gains of at least 900 grams per day, DMI at weaning will need to be at least 2.5 kilograms or more.
Post-weaning to 6 months
Too many changes in a short period and insufficient rumen development are the most common reasons why calves may experience a growth slump post-weaning. Calves are most efficient at converting nutrients into gain up to 6 months old – therefore, taking advantage of their efficiency is priority during this time.
A diet that has grown in popularity is a dry TMR fed ad-lib consisting of a high protein grower mixed with 5% to 15% finely chopped straw or grass hay. While this is not the only way to feed calves effectively at this age, its success hinges on some key factors listed below:
1. Consistency – The nutrient profile of this diet does not change.
2. High ADG – Optimal levels of protein balanced with the correct energy levels to support high rates of gain.
3. Simplicity – There are only a few ingredients in the mix, and large batches can be pre-mixed.
4. Intake, intake, intake – The size of the rumen at weaning is equivalent to the size of a basketball. When presented with a diet made up of dry feeds, a young calf will be able to easily consume enough feed to support high rates of gain; the same is not true when presented with wet/fermented forages at this age.
5. Rumen development – Providing a variety of sources of digestible carbohydrates will support continual rumen development and high rates of gain.
6 to 12 months
Recent research reported that every additional 100 grams of gain in the pre-pubertal stage resulted in 320 kilograms of additional milk in the first lactation. This underlines the importance of properly balanced diets to support an average daily gain (ADG) of 0.8 to 1 kilogram per day so that heifers reach the correct bodyweight and height as they approach breeding age. As seen in Figure 1, achieving consistent growth across the entire group of heifers can minimize the breeding window, allowing for the target age at first calving (AFC) to be met more easily.
With the cost of raising heifers a large expense on a dairy, aiming for an age at first calving just below 24 months is a critical goal. However, Table 2 demonstrates that younger is not always better when it comes to calving in heifers.
On this particular operation, heifers calve between 20 to 24 months, and it is evident that production is maximized as the heifers near the upper end of the range, with a sweet spot in the 22-to-23-month age window. Breaking down production by age fresh is critical to not only optimizing age at first calving, but also to find areas of opportunity in the heifer program. If production is maximized in older/bigger heifers, is body size in relation to mature cows an issue? If production is maximized toward the younger end of the range, is body condition around breeding or calving an issue that needs to be addressed?
Confirmed pregnant (16 months) to calving