Colostrum — nature’s amazing first milk

Colostrum is the first milk produced by lactating mammals and in our livestock species is critical for health, growth and longevity. | Getty Images

With calving, lambing, foaling and kidding seasons upon us, something that may be top of mind for many producers is colostrum.

It is the first milk produced by lactating mammals and in our livestock species is critical for health, growth and longevity.

During gestation, the placental layers in ruminants and horses prevent antibodies from passing from the dam to the offspring. Because of this barrier, they are dependent on their first meals after birth to deliver these life-saving immune molecules into their system, a process that is also called passive transfer.

Adequate intake of colostrum ensures high concentrations of antibodies (also called immunoglobulins) needed by neonates to ward off infections before their own immune system kicks into full gear.

Immune system benefits of colostrum are immediate and important. But research has also found long-term benefits. For instance, dairy calves that receive adequate colostrum are less likely to die after weaning, produce more milk when they start lactating and also have reduced culling rates during their first lactation. The amount of antibodies in the offspring’s bloodstream and how quickly it is used up depends directly on how much they consume and absorb from colostrum.

Colostrum is produced before giving birth and then, over the next following days, the composition gradually changes to what’s called “mature” milk. Besides the presence of life-saving antibodies, colostrum is inherently different from mature milk in many ways. It is rich in immune cells, which may play a role in preventing infections and also help foster maturation in the offspring’s own immune system.

Compared to milk, colostrum is higher in fat, proteins, insulin, minerals (calcium, magnesium, sodium and zinc) and vitamins (A, B, D and E). For instance, Holstein colostrum contains about seven percent fat compared to 3.5 percent fat in whole mature milk.

The growth factors in colostrum, including insulin and growth hormones, are thought to play a key role in stimulating healthy development of the gut lining tissues. The presence of some sugar molecules may be important food for nurturing healthy gut bacteria.

Recent studies have also identified a few unexpected constituents. For instance, it contains microRNA, which are very small snippets of genetic material that regulate gene expression. Secreted in colostrum, microRNAs are absorbed by the neonate and are spread throughout the body via the blood. These tiny molecules that pass from dam to offspring are thought to have an important role in developing and maturing the gut lining as well as the immune system. Another unexpected but intriguing component of colostrum are stem cells. The function of these stem cells is currently unknown, but they may have a role in healing.

Neonates need to ingest colostrum in the first few hours of life when the gut is “open” to absorbing antibodies. Gut permeability declines rapidly over the first 24 hours and by the end of the first day of age, it is essentially “closed.”

With the passing hours after birth, the composition of the milk also starts to change. So it is of critical importance that our livestock neonates get up and nurse within the first few hours of life to maximize their ability to get those passive transfer antibodies.

The recommended volume of colostrum intake for calves is 10-12 percent of their body weight so in a typical Holstein calf, this equates to about four litres. The best source is directly from the dam — nursing facilitates bonding with her offspring and the antibodies in the colostrum are designed specifically to combat pathogens that are present in that particular farm environment. There are commercial colostrum replacement products available to supplement or replace colostrum if something happens to impair those first meals.

How can you tell if your neonates are getting enough? The success of colostrum intake and antibody absorption can be measured by laboratory tests but more practically, through measuring serum total protein on farm.

This involves measuring a blood sample, ideally 24 hours after colostrum is fed. One of the first indicators of an issue with colostrum may be increased infections or failure to thrive. If there are outbreaks of respiratory illness or diarrhea in your herds, then taking a look at colostrum intake is a good place to start.

Dr. Jamie Rothenburger, DVM, MVetSc,PhD, DACVP, is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine. Twitter: @JRothenburger

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