Franklin Vets Blog

Calf immunity

July 10, 2019

Antibodies are essential for a healthy immune system. Calves receive no antibodies from their dam while in the womb. They are entirely reliant on absorbing antibodies from the colostrum feeds in the first 12-24 hours to get the immunity to fight off the diseases and infections that they face over the first 12 weeks of life.

Virtually no absorption takes place after 24hrs so calves need good quality colostrum within the first 6-12 hours of birth. Calves with low antibody levels are twice as likely to die than of those with adequate levels (see diagram below).

Calf survival graph


Factors causing poor immunity in calves

  • Timing of first feed:
    • The single biggest factor in calf immunity is how quickly a calf receives its first feed. The gut closes very quickly, with absorption being 50% by 6 hours post calving and nil at 24hours.
    • As can be seen on the table below, the volume of good quality colostrum required (split between two feeds) increased dramatically the longer the gap between calving and the first feed.


calving to first feed & colostrum requirements


  • Calves left on cows; 26% of dairy calves left to nurse had poor immunity. Picking calves up more frequently reduced the number of calves with poor antibody levels.
  • Quality colostrum; not all colostrum is created equally:
    • There is a lot of variation between colostrum from different animals, with no pattern of who will be good or bad
    • Animals which are sick or have difficulty calving
    • Animals which have been vaccinated against scour bugs.
  • Bacterial contamination of colostrum (cupping dirty cows for gold colostrum collection) can lower the absorption of antibodies.

Raising good young stock

Calves which don’t absorb enough antibodies have higher mortality rate, are more prone to becoming ill and have long-term reductions in animal production. There have been several studies that show the long-term benefits of the early growth phase in young stock:calves

  • Doubling birth weight by day 56 was shown to be 7 times more important than sire selection in terms of milk production.
  • 22% of 1st lactation milk yield can be explained by pre-weaning daily weight gain. This effect extended into 2nd and 3rd lactations
  • Calves fed lower ME diet pre-weaning (but fully growth to target at calving) had lower milk yields, fat and protein in their 1st lactation when compared to those well-grown animals through this period.

This is why scour vaccines, which can appear to be a relatively costly investment, offer a strong return on investment beyond the reduction in the clinical incidence of scour and lost replacements. The examples above demonstrate that it is vitally important that we minimise any reductions in growth rates during these first critical months of life. A fully functional immune system is the best way to ensure that your calves get off to the best start, with effects which are seen throughout their productive life.

Ensure you are starting the season with your best foot forward by doing a few simple things:

Detecting a problem with enough lead time to make changes to avoid a major health problem is of huge benefit over the busy calving period not to mention the benefits to life-long production of your replacements.

Test your calves’ immune function

Take 12-15 bloods from animals under 1 week old to test their antibody levels. Some people have spent 10-15% of their total animal health spend on scour vaccine. I would recommend testing immune function to ensure you are getting the very most out of your investment.

brix refractometer for testing antibodies in colostrum

Brix refractometer

Test your colostrum

Brix testing of colostrum has become more common on NZ farms over the past 2-3 seasons. Brix is a measure of how many antibodies are in each litre of milk.

A brix value of 22% is good, a minimum of 4 litres split into 2 feeds over the first 24 hours will give good immunity. Concentrations under 18% will require 8 litres of colostrum being fed in the first 24 hours (split into 2 feeds). A Brix Refractometer is available from the Shoof stand in our clinics. Over 50% of animals will have poor colostrum, so screening colostrum prior to feeding has been a real success in many herd.

Dr David Moors BVSc (Dist) BSc MANZCVS Medicine of Dairy Cattle