Finding alternatives for antibiotics in calf production

Lautaro Rostoll Cangiano, PhD, University of Guelph

It is well known that calves can have high levels of disease. Diarrhea is the leading cause of death in preweaned calves, with 25 to 30 per cent of calves having at least one bout of diarrhea or a digestive issue during this period, amounting to treatment costs of around $34 per calf per year. In addition to treatment costs, it is important to point out that diarrhea will impact animal growth and could make the calf more susceptible to other diseases.

Despite all these challenges, we still do not have a very efficient way of dealing with this problem in our management toolbox. Traditionally, antibiotics have been used to treat diarrhea, and one recent report indicates that as many as 80 per cent of calves receive at least one treatment for disease on Canadian veal farms. Despite these treatment levels, only a small amount of diarrhea cases actually requires antibiotic treatment. In addition, antibiotic use in food animals is coming under increasing public scrutiny and the scientific community is beginning to question the efficacy of antibiotics to treat and prevent diarrhea, resulting in a need for viable alternatives to antibiotic use in diarrheic calves.

In the past decade, we have greatly improved our understanding of how gut microbes affect the health of young calves – we continue to understand more and more about how they interact with the calf and influence its physiology. Specific probiotics in the market have been shown to promote gut health and decrease diarrhea in young calves. Probiotics are defined as live strains of specific microorganisms which, when administered in adequate amounts, confer a health benefit to the animal.

Young pre-ruminants can be supplemented with probiotics in milk or starter feed to promote gut health, stimulate earlier solid feed consumption, and improve growth. We published a review article on the effects of probiotics and prebiotics on calf growth, development, and health, and found that calves supplemented with probiotics had modest improvements in average daily gain (ADG) during the preweaning period, mainly as a result of reduced incidences of diarrhea and mild improvements in rumen development and starter feed intake.

On average, from all the studies we summarized, supplementation of probiotics during the preweaning period resulted in 100 grams more of ADG. The most commonly used probiotics fed to young calves are live yeasts, mainly Saccharomyces cerevisiae (SC), yeast cultures of SC, and different strains of lactobacillus. In the case of yeast supplementation, some, but not all, of the studies we reviewed showed a reduction in the incidence and severity of diarrhea, as calves supplemented with yeast cultures boasted better fecal consistency and overall health.

In a study our group conducted in Ontario and published in the Journal of Dairy Science, we showed that supplementation of the yeast strain Saccharomyces cerevisiae boulardii (SCB) in milk replacer lowered the incidence of diarrhea and mildly reduced the need for antibiotic treatments. Supplementation of SCB has shown promising results in enhancing immune function in the gut, increasing the calf’s ability to fight enteric pathogens. Lastly, yeast supplementation has shown improvements in starter intake, possibly as a function of improved fibre digestion, and mild improvements in rumen development in early life.

In the case of lactobacillus supplementation, we’ve found that most of the effects appear to reduce the incidence and duration of diarrhea bouts, with little effect on rumen development and starter intake. It is important to emphasize that these probiotics tend to work best under scenarios of high disease pressure, mainly reducing the duration and severity of diarrhea. For example, in a study that supplemented a multistrain lactobacillus probiotic to Holstein calves, the greatest benefit on health was observed during the first two weeks of life, a period when incidence of diarrhea is the highest. This perhaps suggests that a targeted probiotic supplementation approach with lactobacillus will reduce disease when the prevalence is the highest, in turn, reducing supplementation costs.

From all the studies we summarized in our review, probiotic supplementation improved growth and reduced diarrhea. However, it is important to emphasize that there is significant variability among the observed results based on factors like the strain of bacteria or yeast used, if it is a live or dead probiotic, and the disease pressure on a particular farm. These modest beneficial effects on health result in increased profitability, even without improvements in growth performance, due to a reduction in rearing costs.