'Ethical considerations' - cow and calf separation moves up the agenda

TIMING was critical when it came to feeding colostrum, which Prof Reynolds said was important not only for its antibody content, but also for energy.

He said: “The value of antibodies in colostrum is extremely important, but research shows calves really need energy and colostrum provides the energy.

“Calves have a perfectly good immune system, but if they do not have energy, the immune cells cannot work.

“Calves should be getting transition milk. The first day is high quality colostrum, and the solids in the colostrum dilute slowly over time until about the fifth day when it becomes normal milk.”

Prof Reynolds said in the first three days of life, calves were not designed to drink lactose. Their digestive enzymes were not developed enough at this stage and needed milk with less than 30 per cent lactose.

“If there is too much lactose in an intestinal tract which does not have the enzyme lactase, the lactose sugars cannot be absorbed and stay in the stomach and intestine, providing a substrate for bacteria to grow on which increases the risk of enteritis and diarrhoea,” he said.

As well as the most well-known antibody, Immunoglobulin G (IgG) colostrum contains many other antibodies, including immunoglobulin A (IgA).

Prof Reynolds explained these antibodies were not time-sensitive, and rather than being absorbed into the bloodstream, they blocked receptors in the mucosal lining of
the intestine.

This mean pathogens were not able to bind with these receptor sites, which made the calf sick.

“The IgA for corona virus has a short half-life and are gone by day five,” he said.

“When we see calves with diarrhoea at day six, we should send a sample to the lab and feed colostrum again to calves on day four to block receptors again, irrespective of the calf’s inability to absorb IgG antibodies into the blood.

“If it is a corona virus problem, they will usually stop having diarrhoea before the results come back from the lab.”

He added that white blood cells were functional in a newborn calf, but if the calf went into a negative energy balance, the body ‘switched the off’, as the cells required glucose to work. In a period of negative energy, the body started to conserve glucose and energy sources for major organs and closed down non-essential systems which were not needed immediately to survive.

“Calves need the fat, the protein and the antibodies, probably in that order,” said Prof Reynolds

“This is also why cows get metritis after giving birth if they go into negative energy balance during transition.”

He also said, the rumen could take four to eight months to completely develop, as volatile fatty acids (VFAs) stimulated rumen development and roughage improved the mucosal carpet in the rumen.

“By day three to four, dry feed should be available, water drives feed intake from day one, more water, more feed intake,” said Mr Reynolds.

He explained dairy calves would be chewing cud between 24 and 25 days old and starting to absorb some VFAs between 15 and 20 days.

Prof Reynolds recommended providing roughage in the form of alfalfa, hay or haylage but not straw, to encourage calves to chew the cud. Silage was not suitable due to its acidic nature.