A biosecurity plan is designed to prevent the introduction and spread of disease in a herd, or group of animals. External biosecurity includes practices directed at preventing the entry of new diseases into a herd. Internal biosecurity involves practices that aid in preventing the spread of disease within a group. A basic biosecurity plan in beef cow/calf operations should address risks associated with bringing in new animals, quarantine of new animals, communal grazing practices, and basic hygiene including cleaning and disinfection.
New Animals and Testing -- The primary means of introducing new diseases into a herd is via introduction of new animals into the herd. National studies have shown that approximately 40% of beef producers imported cattle into their herds, yet rarely did the producers purchasing animals obtain any medical history from the source herds.
Testing imported cattle for diseases can decrease the risk of introducing new diseases. At a minimum, considerations for testing animals should include when animal will be tested (prior to or after purchase or shipment), where animals will be tested (farm of origin or quarantine facility), and what tests will be performed. Determining what diseases to test for should be done in concert with a consulting veterinarian and involve the risk of specific diseases (considering history of past and current diseases of the seller and buyer), as well as the ultimate goals of the buyer. Veterinarians can also provide advice regarding the value of specific testing strategies since testing methods vary in their reliability and no test is 100% accurate.
An alternative strategy to testing imported cattle can involve testing the source herds or only allowing the purchase and importation of animals from certified disease-free herds or herds with low likelihood of disease. Clearly, communication between the purchaser and seller is paramount and should include appropriate detail, transparency, and integrity. The biosecurity policies that are used in source herds should be no less stringent than those ultimately used in the buyer’s herd.
Finally, producers may attempt to mitigate the risks associated with importing animals by increasing the use of vaccines. It is important to understand that even under optimal conditions, responses to all vaccines can vary and vaccination cannot fully guarantee protection. Importantly, vaccines must be seen as a part of a complete biosecurity plan, but they cannot replace appropriate management practices.
Quarantine -- Quarantine of incoming cattle may decrease the likelihood of introducing certain diseases into a herd. It is most likely to be effective for diseases with short incubation periods and no inapparent carrier states (e.g. Bovine respiratory syncytial virus, parainfluenza virus-3, Bovine viral diarrhea) but is less likely to be effective for diseases with prolonged incubation periods and inapparent carrier states (paratuberculosis, leukosis, brucellosis, leptospirosis, neosporosis).
Quarantine facilities should be physically separate from the main herd. During the quarantine period, animals need to be monitored for signs of disease. Animals placed in quarantine should all leave at the same time (all-in, all-out). Workers attending quarantined animals should wear protective, washable clothing that is devoted solely to the facility. Ideally, individuals working with quarantined animals should have minimal or no contact with the main herd. If this is not practical, the quarantined animals must be worked with only after tending to the main herd. Equipment and supplies used in quarantine must be devoted to the quarantine facility. A quarantine period of at least 60 days is recommended. This period allows adequate time for identifying diseases with short incubation times, performance and evaluation of tests, and preventative measures such as deworming and vaccinations.
Communal grazing -- Communal grazing of beef cow/calf operations is most prevalent in the Western regions of the United States. Communal grazing increases the risk of disease exposure and transmission through contact with potentially large numbers of animals outside the herd. Cooperative management practices can be incorporated in communal grazing situations that help control the risk of disease transmission. An example includes testing of bulls used in communal grazing for Tritrichomonas foetus (“Trich”), combined with the culling of all test-positive animals.
Hygiene -- Appropriate cleaning and disinfection is critical to breaking transmission cycles of disease agents that contaminate housing, feeding and treatment equipment, or other vectors or fomites. Personal hygiene of workers and sound sanitation practices is crucial to stopping the disease transmission between animals (including to and from humans). Personal hygiene should include frequent hand washing, cleaning and disinfection of boots, and thorough washing of clothing. The most important first step to cleaning any equipment involves the thorough removal of organic debris (feces, urine, milk, saliva, etc.). Thorough cleaning must precede the use of disinfectants since as organic debris can inhibit or inactivate many products. Use of manure-handling equipment to feed cattle can greatly increase the risk of transmitting certain disease agents such as M. paratuberculosis and Salmonella spp. Avoiding fecal contamination may be important in minimizing the prevalence of pathogens known to infect humans such as E. coli O157:H7 and Salmonella spp. Lastly, fecal contamination of feed by rodents and domestic animals (dogs, cats) is a risk factor for the transmission of various organisms including Neospora caninum and Salmonella spp.
Closing thoughts -- The most economically significant infectious disease processes affecting beef calves is acute undifferentiated diarrhea. While no single management system is suitable for all herds under all circumstances, the principals of Radostits and Acres in 1983, are still relevant today. These include providing a calf with a non-contaminated environment, increasing the non-specific resistance of calves (adequate colostral intake), increasing specific immunity of calves via vaccination (typically of the dam), and reducing stress. Monitoring for dystocia, aiding birth when necessary, ensuring early and adequate consumption of colostrum, and promoting bonding/avoiding miss-mothering are all means of increasing the non-specific resistance of calves.
A more recent and effective means of lessening the impact of calf hood scours in beef herds is through the adoption of the “Sandhills Calving System”. Numerous descriptions of this system can be found on the world-wide web by simply searching under the term “Sandhills calving system”.
Source: Drs. A. Allen and G. Barrington