Living with Mycoplasma bovis in Turner Bison Herds

By Tom Bragg

Mycoplasma bovis (M. bovis) has been a devastating disease in the Bison Industry for the last 15+ years.  As Turner Enterprises has come to better understand some of the issues around this organism, we have adapted our management in ways that address the potential associated risks. 

A brief overview of Mycoplasma bovis (M. bovis):

M. bovis is a bacterium that uniquely lacks a cell wall. This affects how well the immune system can recognize it in the body.  Prior to it becoming a deadly pathogen, it could be isolated from the respiratory tract of normal healthy bison.  Historically, it was always considered a secondary invader in the course of disease in cattle.  In the mid 2000’s, it was observed as a primary pathogen in bison, meaning it was found to cause disease without any evidence of another invader in the animal.  Over time, we have identified several different genetic “strains” of M. bovis that have been associated with outbreaks.  Its primary mode of spread is direct (or close) contact with an infected animal.  Other transmission methods may be possible (e.g. exposure to contaminated facilities, water, and bedding) but have proven difficult to confirm.  Stress appears to be a factor in development of disease, as a stress-compromised immune system may allow an otherwise subdued M. bovis to turn in to an outbreak.  Turner Enterprises’ biggest outbreaks have been associated with animal movements (shipping and exposure to animals from other herds) and placing animals in feeding operations (nutritional stress, shipping, adapting to more confined space, and exposure to unfamiliar animals).

Learning to live with M. bovis:

The Team at Turner Enterprises has worked with Newport Labs to develop an autogenous vaccine made from isolates associated with M. bovis disease outbreaks.  Mycoplasma bovis can readily change and become a new strain, similar to the way the flu virus changes and adapts in humans.  New isolates are continually evaluated to determine if we need to add the new strain to the vaccine.  Although we are uncertain of the ability of this vaccine to produce a good immune response, using these strains provide a better chance at protection than the commercially available products.  To support the health needs of other bison herds, Turner Enterprises has partnered with Newport Labs to make this M. Bovis vaccine available to US bison producers through their local veterinarians.

Turner Enterprises has reduced the amount of animal movement between ranches to reduce the risk of introducing a disease-causing M. bovis into a naïve herd.  Animal movement and mixing of herds is the most common way this disease spreads from animal to animal or herd to herd.

Preconditioning animals on the ranch of origin prior to moving to a feeding facility is another important step.  This helps to reduce nutritional stress by familiarizing them at home to the new feed ration that will be available to them upon arrival.  During this time, we also booster our M. bovis vaccine and administer commercially available vaccines against other common respiratory organisms to help improve immunity to other possible pathogens.  In addition, removing the bison from the main herd with its well-defined social structure and placing them in a similar age cohort disrupts the animals’ behavior.  To make this transition as low stress as possible, during the preconditioning phase we allow these animals time on their “home” ranch to adapt to their new group prior to the stress of shipping to a feeding facility or new ranch for grazing. 

The design of our On-Ranch Feeding operations is in response to the need to feed multiple origin bison at one location without exposing them to other origin bison.  Although somewhat speculative, the evidence seems to indicate that each herd has its own genetic M. bovis that lives in the respiratory tract without causing disease under normal circumstances.  However, an M. bovis from one herd may cause disease in another herd who has immunity to their own M. bovis but not the unique strain from the original herd.  Our On-Ranch Feeding pens have been designed with approximately 20-foot gaps between them that isolate the groups from any nose-to-nose contact from any other pen.  Alleyways are spaced from the pens as well so each group can be moved to and from the pen without ever having nose-to-nose contact with any other pen. 

While our bison are on feed, we provide them a free-choice selection of different feeds.  All pens have an unlimited availability of grass hay, alfalfa hay, and a grain (typically corn-based).  Through biofeedback, the bison are able to regulate their rumen balance, e.g. by eating more grass hay and less grain if they start to become acidotic. 

The bison in the feeding pens are given a minimum of 600 sq. ft of space per head (some up to 1000 sq. ft per head) which can be almost twice as much space as given in commercial feedlots. 

Waterers are cleaned at least weekly if not more frequently.  Tools for cleaning those waterers are specific to each pen so one brush is not used in any other pen.

Between feeding groups, pens are cleaned as much as possible and waterers are disinfected and allowed to dry if possible.

The Results:

Turner Enterprises’ experience addressing M. Bovis has shown encouraging results using the strategy described above.  For example, in three years of operation, one of TEI’s On-Ranch Feeding operations has experienced very minimal health-related issues, at approximately 0.2% death loss.  The identified health problems were not related to respiratory issues, nor was there any evidence of M. bovis.  The reduction in health-related losses alone has paid for the construction of those facilities in just two and a half years.

Living with M. Bovis appears to require an integrated approach, incorporating big picture structural and detailed management practices, providing for animal welfare by mitigating a broad suite of stress factors, and supporting animal immunity with vaccinations.

Using this integrated approach has helped Turner Enterprises reduce its losses to M. Bovis and provide for improvements in overall bison herd health and animal welfare.