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How to boost heifer performance to improve age at first calving

Heifers hold the key to the future on any dairy farm system. As they transition from calves to potential milk producers, understanding and correctly nurturing the critical stages of their development is essential to overall herd productivity and profitability.

Author: Will Brocklehurst, InTouch Feeding Specialist

On U.K. dairy farms, rearing replacement heifers is one of the largest ongoing investments. According to AHDB, heifer rearing accounts for around 20% of all production costs, with it taking two or more years for farmers to see a return on that outlay.

It is likely that heifers will still be carrying some of that rearing ‘debt’ into their second lactation. The moment at which they start to make a profit on an individual farm will vary, but third lactation is the average. With best management practices and protocols in place, they’re able to get to this point in less time and with less cost. That said, calving first calvers at the correct time, and at an optimal size, is essential to maximising their productivity in the longer term.

What is the best path to success?

  1. Defining success: Key performance indicators

  2. Phase 1: Newborn calf to weaning

  3. Phase 2: Weaning to bulling/breeding

  4. Phase 3: Breeding to calving 

Defining success: Key performance indicators

According to the NMR 500 report published in January 2023, U.K. dairy farms are achieving a median age of around 26 months at first calving. Whilst this is an improvement of 3 months from 2010 to 2023, there is still work to be done.

It is crucial that farm businesses understand current heifer performance before identfying future improvement opportunities. Some of those KPIs may be:

KPI Overall target
Age at first calving 22-24 months
Yield vs. mature cows 80% or higher
Heifers that calve again 90% of higher





This can be broken down by life cycle stage, with more specific aims and objectives tailored to individual farms. Body weight and stature of mature cows sheds some light on this and helps to account for breed and genetic variations between farms.

Here are target weights for youngstock based on mature cow size to benchmark:

  • Breeding – 55%

  • Pre-calving – 94%

  • Post-calving – 85%


Phase 1: Newborn calf to weaning

Now let’s take a look at getting this right at each stage of a heifer’s development. How can we grow heifers that hit target weight gains without excessive body condition?

The goal here is to double body weight from birth to weaning.

Feed efficiency and lean muscle growth is at its highest in calves. Maximising growth during this period is therefore the most cost effective approach. It has been shown to shorten the time to breeding, which achieves a younger age at first calving as well as increasing  production in first lactation. Weighing calves to ensure that targets are hit is critical.

It is well known that correct colostrum management is crucial in providing newborn calves with passive immunity, which is instrumental to getting them off to the best start. All you need to do is remember AHDB’s 3 Qs of feeding colostrum, which can be summarised as: 

Feed 3 litres of 50 g/L of IgG colostrum within the first two hours of life.

For a complete guide, download AHDB’s guide to colostrum management.


Phase 2: Weaning to bulling/breeding

Next on to the transition of calves from a liquid-only diet to a hard-feed diet, which requires significant digestive system development in a short space of time.

Calves start out in life with a rumen that is sterile, small and non-functional. Liquid feed doesn’t start the process of rumen development, and so hard feed must be offered early on. Ideally, this is a starter feed with high levels of highly fermentable carbohydrates to stimulate the growth of rumen papillae. This should be fed alongside dry and clean straw or hay, which helps to increase muscular development of the rumen. Intakes of solid feed must be monitored to ensure that calves are getting adequate quantities to support growth and performance through the weaning process and afterwards.

Heifers often experience a ‘growth check’ at weaning or shortly after, and it is crucial to put into place strategies to avoid the multiple factors that can cause this drop in performance. At the time of weaning, a lot of changes can occur, with diet and grouping changes the most common. Every change should be viewed as a potential stressor. Managing change gradually can help, in particular keeping to one change per week.

Target growth rates during this period can vary between farms due to breed differences and differences in target age at first calving. Nutritional strategies should be directed to maximising muscle weight gain whilst keeping any excess body fat gains and rearing costs to a minimum. Formulating proper diets and monitoring feed intakes and daily liveweight gain is key. 

Total energy and protein intake is a function of the total dry matter (DM) intake coupled with the concentration of nutrients in the diet fed. Consulting with your nutritionist is important in getting this right.

Nutritional guidelines for heifers:

  Kg DM per head MJ/kg DM per head % crude protein per head
Aged 3-6 months 2.5 - 5 10.8 - 11.2 18
Aged 6-15 months 6 - 7 10.2 - 10.6 16

Phase 3: Breeding to calving

Once a successful conception has occurred, it’s important to consider that nutritional requirements change as pregnancy progresses. Focussing on maintaining growth rates in line with mature cow size whilst keeping excessive body condition gains to a minimum is, again, very important.

When heifers mature, they have a tendency to increase the rate of body fat gain and may become over-conditioned. Regular body condition scoring is helpful, providing visual feedback on how the diet being fed is performing.

As heifers progress further into pregnancy towards calving, their nutrient and energy requirements increase, and we must also consider how they will effectively transition into the milking herd from a social point of view. If space allows, calving heifers as a separate group and then running them in a group of only first-lactation animals can be beneficial. If this isn’t possible, they should be moved into the dry cow group around two months before they are due to calve. This gives a good opportunity for them to adjust to being with older cows within a new social group. 

Nutritional guidelines for heifers:

  Kg DM per head MJ/kg DM per head % crude protein per head
Aged 15-22 months 7 - 10 9.6 - 10 14

Monitoring intakes alongside body condition is, again, very important. With all groups of youngstock, factors such as feed access space, water trough access, stocking rates and appropriate lying areas are as important as the feed we put in front of them. 

The journey from birth to becoming productive members of the milking herd is optimised through providing top-quality nutrition and expert care and management. With these in place, it is possible to ensure the long-term success and sustainability of your dairy operation.

Our team of InTouch Feeding Specialists is on hand to support you. If you’re looking to improve your performance, contact us.