How much colostrum is just right? It turns out that it just may depend on the weight of the calf!
Dairy farmers know that making sure newborn calves achieve the right amount of Immunoglobulin G (IgG) concentration in their blood is essential in order for them to have adequate immunological protection and resistance to disease for the first few weeks of life, as their own immune systems gear up and as they develop their own antibodies. However, as soon as a calf is born, a process begins that rapidly renders it unable to absorb the IgG it so desperately needs in its first few weeks. Absorption is indeed at its best within the first two hours of life and completely ceases by the time 24 hours have elapsed. As we know, It's essential that neonatal calves attain at least 10 mg /mL of serum IgG of colostrum for transfer of passive immunity to be successful. But how are we to make sure that calves ingest and absorb enough of it from colostrum in the right timeframe to be optimally effective? This question has been at the centre of an ongoing debate in calf rearing for some time now. As such, researchers at the Teagasc, Animal & Grassland Research and Innovation Centre in Cork, Ireland, and from the School of Veterinary Medicine at the University of Dublin, sought to clarify these issues through an extensive 10-week study which looked at several factors.
Unique study design
Instead of determining a set amount of colostrum to feed calves just after birth, the researchers set out using the unique strategy of feeding colostrum based on different percentages of body weight (BW), to see if that made a difference. To do this, from birth they divided 99 dairy calves into three groups: those fed 7%, those fed 8.5% and those fed 10% of their birth body weight in colostrum within the first two hours of life. They then further divided the three groups into a total of nine, with 1/3 of each of the BW groups receiving either zero, two or four subsequent feedings of transition milk, in order to see if the trace colostrum in the transition milk also had an effect on serum IgG or if feeding it positively affected their health in any way. The researchers measured serum IgG levels at 24, 48, 72 and 642 hours of age, and they assigned health scores to the calves twice a week throughout the study.
Positive effects of feeding 8.5% of body weight in colostrum, and transition milk
Calves in the 8.5% BW colostrum group had the greatest mean serum IgG at 24 hours of life with 39.1 g/L, whereas the 7% BW group had 30.3 g/L and the 10% BW group had 31.2 g/L. While all serum IgG levels were on the decline at 48 hours of life and declined even further by 72 hours of life, the 8.5% BW group still maintained the highest levels. And, while at 642 hours of life, the 8.5% BW group still had higher mean serum IgG than the 7% group, there was at that stage no difference between their level and that of the 10% BW group.
In terms of the effect of the transition milk feedings, while there was no significant effect on serum IgG level, transition milk being fed did seem to have some positive effect on health scores. It turns out that those calves that did receive some amount of transition milk (as opposed to those that received no transition milk) tended to have lower odds of having both a poor eye/ear health score and a poor nasal health score.
A new formula for feeding colostrum effectively
Feeding the right amount of colostrum and doing so rapidly after birth is the key to proper passive immunity transfer for neonatal calves. What the researchers in this case found is that feeding 8.5% of a calf's body weight in colostrum within the first two hours of life helped calves attain a higher serum IgG concentration in those precious and critical first days. And, while feeding transition milk doesn't seem to affect serum IgG levels, it does appear to help with overall health. These findings just may be the key to understanding how much colostrum to feed and when, in terms of attaining the best serum IgG levels, and therefore better outcomes for overall calf health.