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Nutrition and housing influence calf health

Michael A. Ballou Published on 22 May 2015

Dairy calves are extremely susceptible to gastrointestinal disease during the pre-weaned period. The risk for enteric disease decreases as the calf ages.

When a calf is born, it has been exposed to very few if any micro-organisms, and some aspects of its gastrointestinal immune system are not fully developed.



After birth, the calf is in a microbial world and exposed to a greater quantity and diversity of micro-organisms. This adaptation is abrupt, dramatic and a major stressor to a newborn calf.

The calf’s gastrointestinal tract is naïve and develops rapidly during the first few days to weeks of life. The cells that make up the gastrointestinal tract are the immune system’s first line of defense.

Therefore, until the cells are more adult-like, the calf will be at an increased risk for developing gastrointestinal diseases. However, there are strategies for improved maturation of the gastrointestinal immune system.

Nutritional supplementsimprove disease resistance

Prebiotics, probiotics and proteins from hyper-immunized egg or spray-dried plasma have all shown some merit in improving resistance to enteric disease. Prebiotics are dietary components not easily digested by the calf but used by bacteria in the lower intestines to improve their growth.

Probiotics are generally described as live micro-organisms that provide “some” health benefit. At first glance this may seem bad; why would we want to improve the growth of bacteria in the lower parts of the small intestines? As mentioned before, the intestinal tract is not sterile.


Soon after birth, a wide range of bacterial species colonizes the gastrointestinal tract of calves. Most of these bacterial species do not pose any immediate threat to the survival of the calf and in the past were called “good bacteria.”

Many of the common probiotic species are routinely classified as: Lactobacilli species, Bifidobacteria, Enterococccus faecium and Bacilli species. These probiotic species may have a direct bactericidal activity or compete with the more pathogenic micro-organisms for limited resources. In addition, probiotics are bacteria themselves, and they may “prime” the immune system of the calf by keeping it alert, since it still recognizes the “good” bacteria as foreign.

Data on the influence of prebiotics and probiotics alone on the health of dairy calves is equivocal. For every study that shows feeding prebiotics or probiotics in milk reduces scouring and improves growth, there is one that shows no benefits to it at all. The lack of a clear effect in calves is likely due to many environmental factors.

Research does, however, support that many prebiotics and probiotics are generally safe and do not have any adverse effects on calf health and performance. In fact, most regulatory agencies around the world classify most prebiotics and probiotics as “generally regarded as safe” (GRAS).

Last, it is important to note that not all probiotic species and, further, not all strains of a specific species (i.e., not all Lactobacillus acidophilus strains) are equally effective. Therefore, I would recommend only using probiotic strains that have been reported, through research, to improve health and performance of calves. Additionally, viability of the product should be confirmed as many of the probiotic species can become nonviable during processing and storage.

Increased milk positivelyimpacts calf health

Some data suggest that feeding calves greater quantities of milk solids improves future lactation performance. Additional large, prospective studies are needed to confirm these benefits. Most of the data on how the quantity of milk solids fed to calves influences their health during the first few weeks of life is limited to small, controlled experiments with fecal consistency as the primary determining factor.


It was suggested, and a few recent studies from my laboratory are confirming, that calves fed more milk solids will have feces that appears looser, but when the dry matter percentage of the feces is determined, there is no difference. This data underscores the importance of not using fecal consistency as the main or only determinant of health in young dairy calves, especially when they are fed different quantities of milk solids.

A few studies challenged calves with various pathogens, and it appears that feeding greater quantities of milk solids may improve resistance to some infections but increase their risk to others. Therefore, there seems to be a complex interaction between the level of milk solids and the specific pathogen exposure.

My lab showed that when milk solids are fed in restricted quantities, many immune cells are more active. Our thought is that when calves are fed restricted quantities of milk solids, they perform more non-nutritive suckling. (They spend more time licking the environment.) This increased time licking exposes them to more micro-organisms, resulting in a more active immune system. If calves are raised in a dirty environment, that would likely increase risk for disease.

An interesting area of research in both humans and livestock is how early life experiences may have long-term impacts. As stated earlier, it appears that calves fed more milk solids have improved milk production later in life. Data from my lab also suggests that calves fed more milk may have improved health that continues past weaning.

In one of our studies, calves that were previously fed more milk solids had fewer signs of disease after they were challenged orally with a Salmonella enterica serotype Typhimurium. More recently, we conducted a respiratory challenge in calves a month after weaning.

The calves that were previously fed more milk solids had improved resistance to the bovine herpesvirus-1 and Mannheimia haemolytica challenge. More research is needed in this area, but the early reports are exciting, and it is tempting to speculate that the improvement in health may continue to persist even later into life, such as when she freshens.

Calf housing affects healthand performance

In addition to nutrition, calf housing can influence the health and performance of calves. Many calves in the U.S. are individually housed during the pre-weaned period. This allows calves to be more easily managed as individuals and reduces the horizontal transmission of disease. Recent data from my lab indicated that calves housed in groups of three had more active immune cells than individually housed calves.

Our working hypothesis is that these calf-to-calf interactions increase the exposure of these calves to micro-organisms that makes their immune systems more active. Therefore, it is likely calves raised in groups will have an increased risk for disease if raised in an environment that is more conducive to infections. If calves are fed restricted quantities of milk solids, then calves should only be housed individually.

As mentioned previously, restricted-fed calves perform more non-nutritive oral behaviors. Calf-to-calf sucking will increase the risk for negative health outcomes, which would likely outweigh any potential benefit of group housing. There are some clear benefits to group-housing calves.

The benefits of group-housing calves are in the social interactions among the calves. Increased calf starter intake is commonly reported among group-housed calves, and it was suggested that either social teaching or competition led to the increased starter intake.

Calves are going to have to be group-housed at some point during their life, so we need to find the optimal time to do this. There is often a slump in performance and increased risk for disease when we finally group calves together.

In one of our studies, we reported that the calves raised in groups of three transitioned to large groups of five random calves better than calves that were previously housed individually. There are benefits and challenges to both types of housing, which need to be considered with your facilities and management.

In conclusion, dairy calves are highly susceptible to disease in the first few weeks of life, which may be related to the calf’s naïve gastrointestinal immune system. The use of nutritional supplements such as probiotics, prebiotics or protein from hyper-immunized egg or plasma should be considered while the gastrointestinal immune system is maturing.

The relationship between the quantities of milk a calf is fed and health is complicated and dependent on many factors. However, an exciting area of research is how early life experiences, including nutrition, can have long-term impacts on health and lactation performance.

There are clear benefits to both individual and group housing of pre-weaned calves. The benefits of individual housing is less disease transmission and easier to identify and treat a sick animal. The major benefits of group housing are that calves consume more calf starter and may make a smoother transition to larger pens later on. PD

Michael A. Ballou
Associate Professorof Nutritional Immunology
Department of Animaland Food Sciences
Texas Tech University