Bioguide #9

Why maintaining gut health for calf immunity and growth is our #1 calf rearing tip.

It’s not surprising that calves (particularly dairy calves) are prone to a range of health issues, given the combination of under-developed gut and the multiple stressors that can impact their ability to thrive, including:

• Not getting enough colostrum due to the short time they are with their mother. Colostrum provides the passive immunity a calf depends on for the first 21 days of life
• Drinking too much milk, too quickly – the digestive system struggles to handle the flood of food at once or twice-daily feeding. Often calves cannot produce enough rennet at this stage, leading to nutritional scours, which in turn makes them susceptible to other health issues
• Young calves are often housed in groups and pens which expose them to harmful bacteria such as E. coli and Salmonella (which can be introduced via bird droppings)
• As the calves mature, they are rapidly introduced to feed changes e.g. transitioning from milk/replacement milk on to a mixture of meal and grass. This requires equally rapid development of the digestive system in order to acquire nutrition from the new food
• Environmental stresses due to weather (particularly for spring-born calves).

As calves with good gut microbes are more resilient and grow faster, at Biostart we focus on gut health as the first line of defence at this critical early period.

Establish good microbes in the gastrointestinal tract

The first microbes established in the gastrointestinal tract of a calf will stay with that animal for life.  These microbes are usually provided through the first colostrum feeds. Getting the right microbes in the intestinal tract will help fight/suppress disease-causing organisms – minimising stress on the immune system. This is especially crucial over the first 21 days.

Set up the calf’s immune system

It takes 21–23 days for the calf’s immune system to fully develop. The calf’s digestive system has evolved to have a “rumen by-pass” function at this time, allowing colostrum/milk to go straight to the abomasum (the fourth stomach). Colostrum has very high-levels of immunoglobulins – these provide passive immunity to the calf and benefit from this rumen by-pass. There are receptors on the intestinal wall that transport the immunoglobulins from the colostrum directly into the blood supply – thus protecting the calf until it’s own immune system is functional enough to attack diseases. When farmers or vets talk about passive immunity, this colostrum to rumen by-pass to blood supply process is what they’re referring too.

Ideally, calves should get colostrum for four days but that can be difficult on commercial farms. So farmers need to reduce threats to the immune system over the first 21 days.

Minimise scouring

When calves get too much milk, too quickly, they can’t produce enough rennet in time to digest the milk properly – leading to nutritional scours. Rennet is a special enzyme produced by calves that specifically digests the kappa-casein molecule in milk. Rennet clots the milk – the same reason why it is used in cheese making!

When the milk clots, it can be digested properly in the small intestine – allowing the nutrients to be utilised properly. If the milk is not adequately clotted, the undigested milk goes through the calf causing nutritional scours, leading to extra stress on the animal and potential dehydration.

Achieve weaning weight as soon as possible, then wean off milk and onto hard feed

The calf rearer wants to get calves on to solid feed as soon as possible to save time and money.  To do this, the calf needs to reach a suitable weaning weight. 

For a calf to digest solid feed or plant matter, it must fully develop the rumen first.  This process starts as calves get older and they start eating plant material. This plant material activates the rumen microbes and starts the development process of the rumen.

Know your calf rearing additive

There are numerous feed additive products on the market to help calf rearers achieve their goals. These products tend to fall into two major groups – probiotic and prebiotic feed additives.

A probiotic is a live microbe mix consisting of a few bacterial isolates. The intention here is to establish “good” bacteria in the calf’s gastrointestinal tract, displacing the microbes already there.

A prebiotic is an ingredient that specifically changes the gastrointestinal microflora to benefit the well-being and health of the animal. Prebiotics work by stimulating the microbes already in the calf’s gastrointestinal tract (received from the mother via its first drink of colostrum).

The table below highlights some key differences:

BioStart Calf

BioStart Calf is a prebiotic that is added to milk prior to feeding. We’ve gone ahead and included the ingredients below, to help you understand the multiple roles a prebiotic can play in maintaining calf health:

1. Fermentation extracts from six superior strains of lactic acid bacteria – these are the major prebiotic components in Calf and stimulate existing gastrointestinal bacteria as well as inhibiting the activity of disease-causing microbes.
2. Two prebiotic Oligosaccharides – one of these stimulates Lactobacilli and Biffidobacilli, whereas the other can bind to the cell walls of disease-causing animals.
3. Rennet – to initiate milk clotting and reduce the chance of nutritional scours.
4. Several plant extracts – to stimulate rumen development and function.
5. A variety of support nutrients – including essential vitamins, amino acids, minerals and trace elements to support any nutrient deficiencies that may inhibit the calf’s growth.