Avoiding the Post-Weaning Growth Check

By Lorna MacPherson, dairy consultant, SAC Consulting

Weaning is the most stressful times in a calf’s life and how well it performs from weaning onwards can directly impact on the economics of rearing, milk production and that animal’s longevity in the herd.

Immediately post-weaning, it is common for growth rates to fall below the target of 0.75kg/day but this is not always obvious without weighing heifers regularly.

The following should be considered before weaning:

• Is the calf eating enough concentrate for adequate rumen development?

• Has the calf doubled its birth weight at weaning or reached the appropriate weight for age target?

• Is the calf at the minimum age? Calves weaned at less than five weeks are more susceptible to disease.

• Will the calf be able to compete in a larger group?

Feed intake and subsequently rumen development is the most crucial factor in deciding when to wean. Age or weight of the calf gives no indicator as to rumen development and how well the calf will thrive when diet and management changes occur.

Weaning should take place when calves are eating at least 1kg of starter feed for three consecutive days (for smaller breeds aim for 0.75kg intake) but the more the better! Water supply is also critical along with starter feed for rumen development and, as a rule of thumb, calves will drink four litres of water for 1kg of feed.

Calves on accelerated growth programmes consuming high levels of milk or milk replacer (>900g/day) will eat less starter feed and it is even more important that they are gradually weaned as opposed to abrupt weaning. Gradual weaning will result in less of a growth check and ensure calves are consuming sufficient concentrate to help replace the energy and protein lost from milk consumption.

Start the weaning process seven-10 days beforehand to encourage more starter feed intake. Gradual weaning can be done by reducing the number of feeds per day, feeding less milk per feed or feeding the same volume but at a lower concentration of milk replacer (lower dry matter intake).

Dairy calves are commonly weaned at around eight weeks of age. Research from the University of Guelph compared calves weaned at six weeks and at eight weeks of age. Those weaned later showed significantly higher liveweight gain both pre and post-weaning, with higher starter feed intake post-weaning. Their stress levels were also lower as indicated by more time spent ruminating, longer lying times and less non-nutritive oral behaviours i.e. licking and sucking. The calves weaned at eight weeks were 9kg heavier at day 70.

Avoid social stressors and keep calves in the same size of group post-weaning without mixing calves. Increasing group size with unfamiliar calves means the pecking order has to be re-established and less dominant animals will suffer, with lower feed intakes and reduced growth.

With larger groups, there is more competition for resources when the calf is already having to adapt to a new environment with potentially new sources of food and water.

Calves that are stressed at weaning will have a compromised immune system for at least two weeks, increasing the risk of picking up infections and further exacerbating the growth check. Therefore, minimising changes to housing, social groups, feed and water supply in the first two weeks post-weaning will help calves thrive and maintain growth rates. Any change to forage type and concentrates should be made gradually over a few days.

It goes without saying that handling for veterinary procedures (vaccination, dehorning and castration) should also be avoided at this critical time. Only healthy calves should be weaned.

Those with any disease issues or poor feed intakes should be held back until health and feed consumption have improved. If you are not sure whether calves are suffering a growth check post-weaning, weigh them seven-10 days later to work out their average daily gain. If below target, review your weaning strategy and management procedures to identify areas for improvement.