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  • ZISK

Create a Healthy Rumen For Your Calves

Robert B. Corbett DVM, PAS

All of your calves have a microbiome inside them. Starting at birth to develop a strong internal environment will lead to healthy calves and better productivity later in life. 

A microbiome is the total genetic material of the microorganisms in a particular environment.   The microbiota are all of the actual microscopic organisms that exist in a particular environment, such as the gastrointestinal tract (GI tract). 

The factors that influence the development of the microbiota in the young calf include the microbiota of the dam, the environment the calf is born into, colostrum intake of the calf, the types of feed the calf eats, early pathogen exposure, and the use of antibiotics. 

The colonization of the entire GI tract, including the neonatal rumen, occurs rapidly.  Even though the rumen microflora are well-established early in life, the rumen microbiome undergoes significant changes as the animal matures and establishes its adult environment. 


It is extremely important to establish a normally functional microbiota in the intestinal tract as soon as possible to help protect the calf against diarrheal disease early in life.  The calf is approximately 3 weeks old before the mucous layer on the surface of the intestine is well-developed and other attributes are fully functional.  This explains why the majority of diarrheal diseases occur early in life.  Management practices to improve the environmental conditions early in life are important to reduce the exposure of the newborn calf to gut pathogens, at a point in time when they are much more susceptible.

Feeding clean, high quality colostrum as soon as possible after birth has shown a significant improvement in the bacterial colonization of the small intestine within the first 12 hours of life. If the first feeding was delayed for 6 to 12 hours after birth, the ability to colonize was significantly reduced.  

Two other very important factors in the rapid establishment of a normal microbiota are the bacterial load in the milk being fed, and the presence of antibiotics, either in the milk or administered.  


It has been well established that feeding unpasteurized hospital milk has an adverse effect on calf health and disease incidence.  This milk contains high numbers of pathogenic bacteria since the majority of the hospital milk comes from cows with clinical mastitis.  These pathogens will obviously have a direct effect on the health of the calf, but also on the microbiota as well.  

Any time that the normal gut microbiota is affected by stress, feed changes, bacterial challenge, antibiotics, etc., it results in a change in and/or a reduction in the normal microbiota.  Probably the most common way this change occurs is through the use of antibiotics, especially oral antibiotics.  Some people have assumed that the microbiota is resistant to antibiotics and only the pathogens will be affected by antibiotic therapy.

However, this is far from the truth.  Feeding hospital milk laden with antibiotics will definitely have an adverse effect on the microbiota of the calf, both before and after weaning.  Pasteurization will not have any effect on the neutralization of antibiotics, so it is advisable to discontinue the use of hospital milk that contains antibiotics.

Another common practice is to use oral or systemic antibiotics to treat calves with diarrheal disease.  The major pathogens involved in diarrhea in the first two weeks of life are viruses and protozoa, which do not respond to antibiotics.  The only exception would be if the calf has an elevated temperature, suggesting that it is developing respiratory disease, or has issues with Salmonella or toxigenic E. coli.  If the diarrhea occurs between 7-14 days, most cases will not need antibiotic therapy.

The microbiota of the young calf is significantly different from the adult and is constantly in a state of change depending on many factors.  Part of a good management and nutrition program for the young calf is providing the environmental conditions and feeding program that will minimize the effects on the maintenance of the normal microbiota.  Feeding consistency and minimizing exposure to antibiotics, unless necessary to treat bacterial disease, are important factors in promoting the establishment and maintenance of a healthy microbiota, thus maximizing the health and growth of the calf as well as future productivity.



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