New research from the US suggests there are still a number of improvements to be made when it comes to colostrum management.
The success of a colostrum feeding programme can be easily measured. And it is generally agreed that successful passive transfer has been achieved when a calf is bled between one-seven days old and the serum immunoglobulin (IgG) level is at least 10g/litre.
Calves with serum IgG levels of more than 10g/litre are usually classed as a ‘pass’ in the US. Research shows that calves with IgG levels of below 10g/litre will usually have higher treatment and mortality rates and are classed as a ‘fail’.
However, Sandra Godden from the University of Minnesota, says a review of recent research suggests there is an opportunity to aim for even higher values, and the pass or fail categorisation is therefore too simplistic.
A national study in 1991 showed that the incidence of calves with less than 10g/litre serum IgG, and classed as a fail, was 41 per cent.
A similar study in 2014 showed this figure was 13.7 per cent. This suggests farmers have improved their colostrum management over time.
However, Ms Godden adds that when research into the topic over the last 10 years is reviewed it shows higher serum IgG levels incrementally improved calf performance. This led to a review of the 2014 study with calves split into four groups, rather than two, based on their serum IgG g/litre.
It concluded, as before, that calves with a serum IgG of less than 10g/litre were at the highest risk of mortality, and 10 per cent of those calves died before weaning. However the study also recognised that serum IgG levels above 10g/litre were not all equal.
Ms Godden says: “There was a further reduction in mortality with each of the groups of IgG levels. And above or equal to 18g/litre was the best.
“The result was the same for the probability of being treated for some disease prior to weaning. Of the calves with a serum IgG of less than 10g/litre, 65 per cent were treated and the lowest morbidity risk was again for calves with a serum IgG greater than or equal to 25g/litre.
Based on the findings, the research group have come up with new consensus on recommendations for monitoring levels of passive immunity in dairy calves in the USA.
“Instead of just a pass or fail they were split into four groups. The pass zone is now broken into a fair, good and excellent range,” she says.
They proposed a new target for the number of calves in each category. More than 40 per cent should fall into the excellent category, about 30 per cent should be good, about 20 per cent fair and less than 10 per cent should be poor.
Ms Godden says those farmers who are doing well using the pass or fail method should begin to classify calves further into the fair, good and excellent zones to see what proportion of calves are falling into each of the ranges to measure the success of their colostrum programme.
Epigenetic programming looks at the exposure to specific conditions during critical periods of early life, and how this influences development and performance into adulthood.
Ms Godden says: “An example of this is the effect of heat stress on pregnant dams, in the last trimester.
“A study compared heat stress dams versus non heat stressed dams. It showed that calves born to heat stressed dams had lower absorption of IgG from colostrum. In the longer term they had poorer reproductive performance as yearlings and further on they also had reduced first and second lactation milk yield.