Probiotics and their impact on calf gut health

Calf diarrhoea, other than those of viral or bacterial origin, is usually associated with intestinal microflora disorders and damage to the intestinal mucosal barrier.

Calf diarrhoea causes huge economic losses due to high mortality, treatment and labour costs, poor growth performance and reproductive costs. Therefore, it is important to effectively prevent and control diarrhoea in calves by improving gut health.

Role of Intestinal Microflora

Gut microbial composition in pre-weaning calves affects their health and growth performance. The gut microflora has several functions such as carbohydrate and fibre degradation, regulation of dietary lipid intake and accumulation, production of vitamins and short-chain fatty acids, immune system stimulation, intestinal movement control and host protection from intestinal pathogens.

In newborn calves, various microorganisms from the external environment enter and colonise the digestive tract and any disturbance in intestinal absorption, movement and secretion disrupts the intestinal microflora. When the intestinal microbial barrier is breached, many enteric pathogens such as bacteria and viruses colonise the intestine and cause inflammation and subsequent diarrhoea.


Probiotics are live microorganisms, including bacteria and yeast, supplemented in sufficient quantities to improve gut health and reduce the incidence of diarrhoea in calves.

Effect of yeast products

Yeast products prevent microbial imbalances and increase microbial activity in calves, which reduces the incidence and severity of diarrhoea. Commercially available yeast products include live yeast (dried fermentable live yeast) and yeast cultures (yeast fermentation products containing the media in which they are grown).

Supplementation of yeast products at the pre-weaning stage promotes optimal maturation of rumen microflora, increases initial feed dry matter intake, average daily weight gain and faecal consistency, modulates intestinal mucosal recovery and reduces the risk of pathogen colonisation.

The most widely used probiotic yeast strain for livestock is Saccharomyces cerevisiae, which stabilises rumen pH and enhances cellulolytic bacterial growth in early rumen conditions. Calves supplemented with Saccharomyces cerevisiae can resist low weight gain during the diarrhoea period.

Furthermore, supplementation of Saccharomyces cerevisiae to calves failing passive immune transfer improves performance and reduces the duration of diarrhoea.

Yeast culture improves intestinal development through increased villus height and villus height-to-crypt ratio in all segments of the small intestine and increased villus length and crypt depth in the ileum. Furthermore, yeast culture increases intestinal barrier integrity and reduces the leakage of toxic luminal antigens and bacteria.

Saccharomyces cerevisiae supplementation during the first week of life increases the production and release of secretory IgA in the ileum and colon and establishes healthy microflora, limiting pathogen growth. In milk, Saccharomyces cerevisiae supplementation increases butyric acid producing bacteria and Lactobacillus.

Bacterial-based probiotics

Bacillus Subtilis and Enterococcus Faecium are mainly used at the pre-weaning stage to improve gut health, reduce diarrhoea, enhance growth performance, limit pathogen invasion, provide a nutrient-rich environment in the gut microflora and increase host digestive efficiency and mucosal immunity.

In addition, bacteria-based probiotics regulate the intestinal immune response, increase mucin production by goblet cells, improve barrier function by increasing tight junctions and promoting regulation of the inflammatory response.

In addition, bacteria-based probiotics produce bacteriocin, an antimicrobial peptide, in the intestinal lumen to reduce the risk of pathogen infection. Bacillus subtilis reduces the duration of diarrhoea and supports the prevention of calf diarrhoea.


    Calf diarrhoea is difficult to alleviate due to its multifactorial aetiology involving both infectious and non-infectious factors. Probiotic supplementation provides beneficial effects that improve growth performance while reducing digestive disorders. Probiotics colonise the intestinal tract, adhere to the surface of the intestinal mucosa and form a microbial protective layer to reduce the habitat of pathogenic bacteria and prevent their invasion.

    In addition, supplementation of these probiotics with vitamins and minerals, which have regulatory functions in the body and in the absence of which various metabolic diseases occur, will support the immune system and improve performance in daily live weight gain. CALFADYN, which is among Betra premixes, is a synergistic preparation that provides this support in calves.