The Effects of Probiotics on Calf Health and Productivity

Robert B. Corbett DVM, PAS, Dipl. ACAN

( Dr. Robert Harding )

In the previous article we discussed the development, maintenance, and function of the microbiota of the young calf.  If you have not read this article, I would encourage you to do so since it lays the foundation for understanding how probiotics may have a positive effect on the microbiota of the gastro-intestinal tract.

Probiotics are defined as live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host.  There has been a tremendous amount of research in recent years on the potential health benefits of probiotics in humans.  Approximately 10,000 articles have been published since 2008 concerning this topic in humans alone, not including those articles that have been published on the use of probiotics in other animal species.  The main purpose of probiotics is to enhance intestinal health by encouraging the development of a healthy microbiota (pre-dominated by beneficial bacteria), preventing enteric pathogens from colonizing the intestine, increasing digestive capacity, lowering the pH, and producing metabolites.  These effects result in improved mucosal defenses and immunity. (Microbes Environ. Vol. 30, No. 2, 126-132, 2015)

In the previous article on the microbiota, I discussed that normal immune development depends on the microbiota of the dam, the environment that the calf is born into, colostrum intake of the calf, the types of feed that the calf eats, early pathogen exposure, and the use of antibiotics.  As a result, the microbiota varies significantly depending on these individual factors, from calf to calf, as well as from farm to farm.  The goal of any probiotic product is to encourage the development of a healthy microbiota, and to not interfere or alter the microbiota by inhibiting the development of the organisms that have been shown to be beneficial to the young calf. 

The microbiota is very dynamic and is constantly changing depending on the factors described above that are involved in microbiome development.  The human microbiota has been intensively studied, and there have been more than one thousand different bacterial species isolated so far. The human microbiota weighs 3 to 5 pounds, the microbial cells outnumber our own cells by 10 to 1, and the DNA of the microbiota outnumbers our own DNA by 100 to 1.  There is no reason to not assume that there is a similar relationship in animals.  This really puts things in to perspective as far as the huge influence that the microbiota has on all animals, and the importance of maintaining a healthy microbiota.

Numerous studies have been conducted on the influence of probiotics on the microbiota in young calves, with conflicting results.  Since the microbiota is so diverse from animal to animal and from farm to farm, one would not expect to receive similar results from all of the studies performed.  Probiotic formulas for administration to calves have been on the market for many years.  Most of the formulas used were placed on the market without sufficient research in calves, and often applied the research conducted in humans to the use in calves, assuming that similar results would be obtained.  Also, many of these probiotic formulas only contain one specific species of microorganism.  Human studies strongly support the use of multiple strains of microorganisms since the microbiota is so diverse, making it important to choose multiple strains that are predominant in numbers and have the greatest influence on improving the microbiota and its functions.  As mentioned previously, the microbiota in the young calf is different from that of the adult, and is constantly changing as the animal matures.  These changes should be taken into account when a probiotic product is formulated for young calves. 

Many of the probiotic products contain only one species of bacteria.  There is some research that shows that a single strain yielded positive results, but it was variable.  This is obviously due to the diversity of the microbiota.  Thus, it is possible for a product to work on one farm, and not show any effect on another farm.  As with humans, there is an increasing amount of microbiota research in young calves as well as adult ruminants.  As this research is completed, more information will become available on formulation of probiotic products that would be beneficial to the calf.

Most people do not realize the importance of the microbiota from a nutritional aspect.  These bacteria are very important in the young calf in assisting in the digestion and utilization of the nutrients that are consumed during this period.  Even though the calf is not and should not be consuming large amounts of calf starter at an early age, what is consumed is not efficiently utilized in the rumen and passes on to the intestine.  The intestinal microbiota is essential in the digestion and utilization of plant oligosaccharides and fiber in these calves prior to developing a fully functional rumen.  If the microbiota of the young calf is not well-developed, or is altered by other factors, it will result in a decrease in the availability of the nutrients in the feed consumed.  This will obviously result in a decrease in average daily gain and feed efficiency.

The previous article also described the adverse effects that antibiotic usage had on the microbiota.  This includes oral and systemic administration of antibiotics, as well as antibiotics that are present in non-salable milk. If antibiotic treatment is necessary, then this would be an appropriate time for the use of probiotics.  Since pasteurization does not destroy antibiotics, the non-salable milk should not be fed to calves.  If non-salable milk is being fed, it would be advisable to use probiotics to try and maintain a functional microbiota as much as possible while the calf is being fed non-salable milk. 

There are “Direct Fed Microbial” (DFM) products on the market that are soluble in milk, and in most cases, would be especially beneficial if hospital milk is being fed to the calves.  To determine if these products are beneficial, the calves have to be closely monitored, and information related to disease incidence and treatments entered into their computer record.  Also, it is extremely helpful to have birth weights and weaning weights to help determine the success of the calf nutrition program and if there is an actual improvement in the health and average daily gain of calves that are being fed a probiotic product.

The weaning process can have a major adverse effect on the microbiota of the calf.  There will always be major changes to the microbiota when the calf is changing from the highly digestible milk to the less digestible dry feed.  These microbiota changes take time to occur, making a closely monitored weaning process extremely important when it comes to allowing these changes to occur gradually. Low impact weaning is absolutely essential to minimize adverse effects on the health and average daily gain of the calf.  Weaning protocols, which use the cessation of one feeding per day as the first step in the weaning process, should not be used.  This results in the calf consuming a larger amount of starter the following day when it does not receive that milk feeding.  Increasing the volume of starch that enters the rumen of the young calf, results in either clinical or sub-clinical acidosis.  This will result in a significant change in the microbiota, leading to an increase in the susceptibility of the calf to the colonization of pathogenic bacteria, resulting in an increase in diarrhea and respiratory disease, a common outcome in calves post-weaning.

The weaning process is a major transition for the calf, equivalent to the transition of the closeup dry cow to the lactating animal.  The weaning process has to have a major focus on management at this time to allow the gradual adaptation of the calf to dry feed, and allow the microbiota sufficient time to adjust the populations of microorganisms that is necessary to maintain the efficient utilization of nutrients as well as the health of the gastro-intestinal tract.  Hopefully, the calf is receiving at least 8 quarts of milk per day, divided into two feedings.  The calf should be maintained on this amount of milk until it is consuming enough starter to be able meet its nutritional requirements as the milk is gradually reduced.  This would be approximately 4 pounds a day of an 18% crude protein starter, or 2 pounds per day of a 25% crude protein starter. An example of a gradual weaning process in this feeding program would be as follows:


                                    4 quarts AM                4 quarts PM  (until consuming sufficient starter)

                                    3 quarts AM                3 quarts PM (for 4 days)

                                    2 quarts AM                2 quarts PM (for 4 days)

                                    1 quart AM                  1 quart PM (for 4 days then wean)

This process will take a total of 12 days to complete.  This will allow the microbiota the time it needs to gradually adjust its bacterial populations from the liquid diet to the dry feed.  Shorter weaning programs will most likely result in major fluctuations in microbiota population as a result of clinical or sub-clinical acidosis. The weaning period would also be a time that probiotics would be beneficial to try and maintain a healthy microbiota during changes in rumen and intestinal pH as well as feed substrate. 

Since the microbiota is constantly changing and is affected by so many environmental factors and feed changes, as well as disease and antibiotic usage, it would make sense to utilize a good quality probiotic while the calf is on milk and through the weaning process.  Again, the only way to determine if the selected probiotic is having a positive effect on the health and feed efficiency of the calves is to monitor the results by accurately recording health events and weight gains.

In addition to the probiotic and direct fed microbial products that have been on the market for quite some time, there is a new generation of probiotics that are designed to fight specific diseases.  As an example, multiple manure samples are collected on an individual farm and the pathogenic Clostridia species are isolated from these samples by culture.  The Clostridia species have been determined to be specific to that operation, similarly to way that the microbiota is similar on the same farm.  The Clostridia sp. are grown in culture with thousands of different strains of Bacillus subtilus to find which strains of B. subtilus produce bacteriocins which are toxic to the Clostridia sp., resulting in their death.  Once these specific strains of B. subtilus are determined, they can be grown in the lab and produced in large amounts to be added to the feed of the animals, thus reducing the numbers of pathogenic Clostridia sp. on the farm.  This results in a significant decrease in the number of sick and dead animals that are succumbing to Clostridia infections.

It is likely that in the future, there will be more probiotic products designed to target specific pathogens that are causing significant morbidity and mortality on dairy farms.  This will also result in a decrease in antibiotic usage, and lower the incidence of antibiotic resistant bacteria on the farm.

Probiotics have often been looked upon as “snake oil”, and in some instances, may have had no positive effects.  However, as new research is published, in both humans and animals, it is rapidly becoming more apparent on how essential it is to maintain a healthy microbiota, especially in the young calf.  Reputable companies are now producing probiotic products that are of higher quality, contain multiple strains of bacteria, and are yielding positive results in the animals they are being fed to.  Still, it is important to carefully monitor the results of the probiotic you decide to use to make sure you are receiving the return on your investment as well as the results you expect in improved health, weight gain, feed efficiency and productivity.