Jim Reynolds, of the Veterinary Medicine Teaching and Research Center in Tulare, Calif., offers these tips to troubleshoot biosecurity problems with calves.

“Biosecurity refers to protecting the farm (production unit), and the animals and the people on the farm from external and internal biological pathogens. Pathogens can be introduced from outside the farm into the farm (external, or incoming biosecurity) or can be moved around within the farm (internal biosecurity). Pathogens can also be spread from the farm to other farms (outgoing biosecurity).

“Concepts basic to developing and maintaining effective biosecurity programs are pathogen load, contact probability and infective dose. Pathogen load is the amount of a pathogen (bacteria, virus, and parasite) in the environment of the calves. Contact probability is the opportunity, or risk, that a calf will be exposed to a pathogen. Infective dose is the amount of each specific pathogen needed to actually infect a calf. The three areas are completely inter-related and it is necessary to address all three in the calf raising program to maintain healthy calves. The goal for raising healthy calves is to decrease the pathogen load via sanitation and minimizing the days calves are sick, decrease the risk of a calf getting exposed to a pathogen and to increase the ability of the calf to fight off an infection without developing clinical signs (manage infective dose).

“Pathogen load in a biosecurity program is managed primarily through sanitation, nutrition and disease treatment protocols. Having calves born into clean, dry sanitary maternity areas is essential. If a calf is born into wet, dirty environment it will be exposed to increased amounts of pathogens such as E. coli, Salmonella, coronavirus and cryptosporidia. Movement of the calf from the calving area to the calf raising area or to a calf ranch will take these pathogens to the calf housing and increase the pathogen load to the other calves in the housing unit. The transport trailer must be spotlessly clean. The calf housing must be clean and dry throughout the growing period. Ventilation can be a problem for calves raised indoors and must provide fresh air and not recirculate pathogens. Calves that develop disease will shed the pathogens in feces, saliva, nasal secretions and respiration. It is essential that sick calves get identified early, diagnosed correctly and treated properly. The longer calves are sick, the more pathogens they will excrete into their surroundings and the more that pathogen will be available to expose other calves.

“Contact probability is the risk that a calf will be exposed to a pathogen. It is clear that an increased amount of pathogens (pathogen load) in the calf's environment or on the calf facility will increase the odds that each calf will come into contact with a pathogen. Contact probability is managed by reducing the pathogen load and by minimizing the transfer of pathogens onto the farm or within the farm. Calf housing should be designed to provide each calf a clean, dry comfortable place to lie down stand and turn around, have normal postures and behaviors and to minimize the spread of pathogens between calves. Calves can be raised in group housing or individually, with a primary goal of maintaining sanitation and facilitating contagious disease control. Individual housing for neonate calves (up to weaning) normally provides advantages in controlling contagious diseases because the calves are stationary and the contagious disease control procedures revolve around keeping feces and infected material from moving from calf house to calf house. Pathogens are moved between individually housed calves by people, vermin (rodents, flies), air (ventilation) and flush systems, if they are being used. The chance that each calf will be put in contact with a pathogen is very much under the management of the calf facility. The workers should be trained to treatment protocols that reduce to an absolute minimum physical contact with each calf, especially feces.

“Biosecurity then, is directed at controlling pathogens coming into the farm, being spread around inside the farm and leaving the farm to other farms. The issues related to these areas are different for calves on a dairy compared to calves raised on calf ranches.

“On large farms and ranches, calf diseases tend to be age-specific because of the relatively constant exposure of the calves to pathogens. This can be useful in managing infectious calf diseases because the risk periods are defined. Usually by the third or fourth week most calves have been exposed to the major calf pathogens. The goal of management is to emphasize sanitation, nutrition, disease detection and treatments in the first few weeks of the calf's life.”

Source: Dairy Calf and Heifer Association