Successful calf-rearing means calves grow well and remain healthy even when exposed to infections.
University of Melbourne PhD candidate Emma Ockenden has spent the last three-and-a-half years examining the impact of two different feeding strategies on calf immune responses pre-and post-weaning.
The results showed the level of milk fed pre-weaning has long-term impacts on that animal’s immune system.
Current industry standard is a minimum of four litres of milk fed daily to calves from birth until weaning.
Recent years have seen dairy farmers examine their feeding routines and take up accelerated feeding; that is, an increased level of nutrition.
One accelerated method of feeding calves involves feeding at least eight litres of milk a day from a few days after birth until weaning.
Emma wanted to see if feeding higher levels of milk in early life would impact how the immune system of those dairy calves responded in comparison to calves fed at the current industry standard.
The immune response was measured during the pre-weaning phase via a blood test before and after vaccination of the calves.
“A superior response to the vaccine correlates to an animal that is more resilient, and we wanted to see if the level of nutrition or volume of milk fed to the calves influenced this,” Emma said.
Results of the blood test showed the calves fed the higher volume of milk had a superior immune response in comparison to those that were fed at industry standard.
All calves involved in the experiment were then weaned based on age rather than weight, with the calves receiving the higher level of milk being between 15 and 20 kilograms heavier than the calves fed at industry standard.
While the increased amount of milk fed to the calves paid off with higher growth rates and improved immune responses in dairy calves reaching weaning, Emma was also interested in what happens to these calves post-weaning.
Post-weaning, pasture-based heifers are typically put out to pasture in paddocks away from the main milking herd or put on agistment properties where they receive less intensive management.
This led Emma to examine whether the accelerated method of feeding calves had longer-term responses or effects post-weaning.
Post-weaning, these groups were all reared as per normal farm practice.
The research was able to show that calves fed at the higher level of milk pre-weaning still had a better immune response regardless of what their post-weaning feeding regime was.
“We repeated the immune response challenge post-weaning when calves received a booster vaccination at 12 months of age,” Emma said.
“Even though the calves fed at industry standard pre-weaning had caught up to the other calves in weight, they still did not display the same level of immune response that the accelerated milk fed calves showed.”
On-farm calf-rearing practice implications
Consider your calf feeding practices and whether the amount of milk you are feeding calves could be increased.
If you increase the amount of milk fed pre-weaning, you still need to keep your focus on consistent growth over the first two years of life.
It is likely that this superior immunity will pay off as cows that are better able to resist disease will be more likely to produce high levels of milk, calve each year without difficulty, and remain in the herd for a long time.
The calves involved in Emma’s research are now entering the milking herd at Agriculture Victoria’s Ellinbank SmartFarm, where their performance will continue to be monitored to determine their milk production and other impacts that early life nutrition can have over the life of the cow.
This research will form part of the DairyFeedbase23-28 research program, which started last year.
