How to keep calves growing and thriving post-weaning

Maintaining attention to heifer calf health and performance post-weaning is vital to avoid losing gains already made and to keep them on track to meet the industry target of calving at 24 months.

In general, farmers focus closely on managing their pre-weaned calves, on the level of milk fed in particular.

Relaxing that focus once calves are weaned can undo some of the progress made in those early weeks.

Maintain performance and efficiency after weaning

To maintain performance and efficiency after weaning requires a seamless transition, with several key considerations around achieving this:

• Ensure proper rumen development pre-weaning

• Over-feeding milk and not allowing the calf sufficient time to adapt to solid feed can cause major issues.

• Milk volumes are quite often retained at high levels for too long during the pre-weaning period, discouraging solid feed intake and impacting negatively on the calf’s ability to utilise dry feed.

Setting our sights on achieving a certain weight by weaning is not the main focus. We are aiming to get calves eating dry feed and water early alongside their milk – if their rumen is sufficiently developed, they will continue to grow post weaning, if it’s not they won’t.

The more important target to aim for in calves is weight gain. They should be able to easily achieve 0.8-1.0kg daily liveweight gain (DLWG) in the lead-up to weaning and continue this trajectory during weaning and afterwards, regardless of their weight. By adopting a gradual weaning programme, they will adjust to a diet that doesn’t include milk.

Rumen development is a gradual process, not instant. To achieve this, milk and concentrate feeds should complement one another to provide the calf with adequate energy and nutrients to develop in a way which provides a solid foundation for good health and an ability to digest solid feed once milk is withdrawn.

Microbes in the calf’s gastrointestinal tract are responsible for digesting and utilising dry feed and they need time to adjust to that feed to do an efficient job.

Failure to prepare the rumen for weaning risks post-weaning growth checks and the nutritional stress will heighten the calf’s susceptibility to disease.

To avoid undoing the hard work invested in the pre-weaning period, only wean when calves are eating 1.75 – 2kg concentrates a day.

Introduce just one change at a time

Calves are creatures of habit and deviation from their usual routine causes them stress, resulting in disease and a reduction in overall performance.

Change needs to be minimised and that means making the transition period gradual to allow the calf time to adapt and move forward. To achieve this:

• Reduce the number of milk feeds prior to weaning

• Allow calves to stay in the same house for a week or two post-weaning to maintain a stable environment

• Keep calf groups the same rather than mixing groups as this will avoid social interaction issues

• Don’t change the type of concentrates and forage fed until a few weeks after weaning

Concentrates and forage

Once the calves are weaned their primary source of nutrients will be concentrates, with forage secondary until the rumen is fully developed.

The rumen grows considerably in mass and size after weaning (Baldwin and Connor, 2017). The reticulorumen almost doubles in size (67% of total forestomach) by 12–16 weeks’ of age compared to at birth (38% of total forestomach) (Diao et al., 2019).

Ad lib concentrate feeding, alongside complementary forage such as barley straw or low-to-medium quality hay, is recommended until the calf is at least 16 weeks old.

Although the economics of feeding concentrates can make it tempting to swap these for silage once the calf is weaned, this is not recommended as at this early stage the rumen isn’t fully able to digest and utilise the volatile fatty acids (VFAs) from fermented feeds.

Fermented forages such as grass silage or grazed grass should be introduced gradually alongside concentrates and straw or hay as a fibre source as this will allow the rumen to adapt gradually to the new feed.

Good quality silage can become a main feed source around six months of age.

Monitor and maintain average DLWG

How well calves thrive during the transition period is a good indicator on how successful the weaning process has been.

Aim to provide enough nutrients post-weaning in the form of VFAs from concentrates to achieve optimum muscle gain without laying down too much fat.

Consider the desired mature weight of that calf as an adult cow and the ambition to calf at 24 months. For example, if a Holstein with an anticipated mature weight of 700kg is to achieve 85% of that at calving, that equates to 595kg. By deducting her birthweight, in this case around 40kg, this gives 555kg. When divided by 24 months, it means achieving a DLWG of 0.76kg/day.

Regularly weighing and body condition scoring heifers are useful tools to help keep the herd on track and to allow diets to be adjusted where needed ahead of breeding.

Don’t compromise progress already achieved

Good management and effort once calves are weaned will ensure progress is maintained.

Set the calf up with a well-developed rumen before milk is removed, provide the correct feed sources post-weaning and limit changes and stressors where possible.

Monitor growth rates and keep a check on health.

By observing these key steps heifers are likely to hit the target of calving at 24 months.