Update on preconditioning (Proceedings)

Objectives

     • Cow-calf operations can impact post-weaned calf wellness by creating a program to both enhance animal immune function and decrease disease challenges.

     • Preconditioning programs are varied and selection of techniques for an individual farm is related to management and marketing constraints.

     • Vaccination programs should be implemented in a time frame to allow generation of active immunity prior to disease exposure.

     • Methods to decrease stress associated with weaning (such as fenceline weaning) reduce the incidence of disease and improve calf performance.

Beef production is shifting toward a consumer focus and new areas are achieving more attention including: individual animal identification, value-based marketing, food safety, as well as source, process, and age verification. These recent developments in the beef industry are compatible with concepts of preconditioning and should benefit the producer who adequately prepares their animals for the next production phase.

Individual farm production goals must be identified prior to implementation of any new health or management scheme. The selected method for increasing economic returns for the farm influences health program targets and value of veterinary services to the specific operation. The goal of a calf wellness program for the cow-calf farm is to maintain health from birth until sale of the animals. Prevention of disease in the post-weaning phase is based on implementation of management practices to reduce the negative impacts of disease and facilitate transition to new management and nutritional situations.

Managing for a single disease causing agent or risk factor will not eliminate disease from the population. The production of healthy cattle must include proper management, prevention and treatment procedures aimed at reducing disease risk factors. New and improved molecules to eliminate or prevent infection from pathogens will not abolish disease from cattle. Management of the traditional epidemiological triad of pathogen, host, and environmental factors must be incorporated into generating a wellness program. Many producers request a "Health" program from their veterinarian expecting a list of vaccines and times to process cattle, but what they are really asking for is a system to reduce the negative impact of diseases and enhance herd production.

Preconditioning programs

Preconditioning programs designed to decrease morbidity in feeder calves are not a new concept; variations on the theme have been around since the 1960s. Vaccine and management technologies have improved, but the core concept has remained constant: disease can be decreased by reducing disease challenge and enhancing the animal's ability to ward off pathogens.

New technologies typically have uptake curves related to utility of specific methodologies. Industry-wide adoption of comprehensive preconditioning practices has been slow, in part because the value added through management practices must be coupled with a marketing system that provides economic incentives to the manager who incurred increased costs associated with the preconditioning program. The cow-calf owner is in possession of the cattle at the most opportune time to precondition, yet may not own animals when benefits of preconditioning are reaped. The decision to precondition calves is based on both potential added value and the marketing mechanism to capture this value. Accurate conveyance of potential value between buyer and seller is a critical step in capturing the increased worth of preconditioned animals.

One challenge in evaluating impact from preconditioning programs is the widely varied definition of what preconditioning entails. Procedures included in preconditioning programs differ and an accurate definition is critical to generate valid expectations as specific components (i.e. length of weaning prior to sale, type of feeding and vaccinations) likely impact the outcomes of animal health and performance. Preconditioning guidelines range from requiring castration and one viral immunization to more complex management schemes involving weaning, feeding a specific ration, and two rounds of immunizations. If the term "preconditioned" is applied generically to all calves that had some procedure performed prior to sale, the brand, or perceived value is diluted. Logically, the likelihood of reducing disease incidence varies in each set of calves based on the specific procedures performed. Specific preconditioning program descriptions should adequately differentiate based on the level of management, yet in many cases buyers view preconditioning as a binary (yes/no) descriptor. This view results in unrealistic expectations for some sets of calves.

Enhancing immune response - vaccinations

The goals of the vaccination program are to stimulate an effective immune response, prevent shedding of the pathogens and improve performance through decreasing subclinical disease. Bovine Respiratory Disease (BRD) is the most frequent disease affecting feeder calves in the post-weaning phase, and commercial or autogenous vaccines are available for all major pathogens associated with this syndrome. One option is to vaccinate all cattle for all potential pathogens, however, a more appealing alternative is to use evidence based guidelines to select appropriate immunization protocols for the cattle.

The cow-calf producer has an advantage as immunizations can be given prior to stresses and disease exposure post-weaning. Cattle take seven to fourteen days post-vaccination to stimulate immunity to infectious etiological agents. Non-specific immune responses may occur sooner, but in general the vaccination schedule should be completed at least one week prior to shipment or exposure to disease challenge. Modified-live vaccines stimulate cell mediated and humoral immunity and recent evidence reveals that parenteral MLV vaccines are effective at stimulating rapid immune responses. (Fairbanks, 2004) Killed vaccines require a booster and the booster immunization should be completed at least 7-14 days prior to disease challenge. Effective immunization must be performed in time for the animal to mount an appropriate response prior to challenge to confer health benefits to the animal.

Specific antigens included in the protocol should be based on available evidence. Clostridial bacterins are important components of calf wellness programs. MLV viral vaccines are effective at stimulating immunity to relevant pathogens in the BRD complex. Mannheimia haemolytica vaccines have mixed results in clinical trials, however, many trials have been performed on arrival to the feedyard and the cow-calf producer can give the immunization prior to exposure allowing a longer time for calves to generate immunity. Research is limited regarding effectiveness of other BRD bacterial vaccines (Histophilus, Mycoplasma).

Processing protocols

A specific protocol should be generated for each operation using the history of particular disease prevalence on the farm. The timing of the program (starting at 3 weeks prior to weaning or at weaning) is based on management and labor constraints of the farm. An effective protocol should be communicated to the cow-calf producer in writing and explained thoroughly. Decision points for inclusion or exclusion of specific procedures should be clearly defined. An example protocol for preconditioning feeder calves is listed below:

Initial processing (either 3 weeks prior to wean or at weaning):

Enhancing immune response - stress management

Weaning is a stressful period for feeder calves and this event typically results in reduced feed intake and a challenge to the immune system. The goal is to utilize appropriate management and animal husbandry tools to minimize negative effects. Animal stress can be divided into the broad categories of psychological (restraint, handling, or novelty) or physical stresses (hunger, thirst, fatigue, injury, or thermal extremes). (Grandin, 1997)

Second processing (either at weaning or 3 weeks post-weaning):

Fenceline weaning is a management program allowing calves to see, hear, and smell their dams through the weaning process. Recent research has illustrated that providing fenceline contact between calves and dams for 7 days post-weaning reduces instances of signs of behavioral distress and increases weight gains (Price, 2003). Cattle in these systems face relatively low levels of disease challenge during the stressful period of maternal separation and tend to have comparatively low rates of illness. Maintaining calves on their current pasture also limits the dietary transition for the animals through the weaning phase. After acclimation to maternal separation, calves can be moved farther from dams and ration supplemented to provide the desired level of nutrition.

Cattle handling is another important aspect of minimizing the stress impact. Psychological or physical stresses can result from environmental challenges, poor facilities or abrasive cattle handling techniques. Feeder calves should be processed in a calm manner to enable maximum response to immunizations.

Summary

Prevention of disease is based on enhancing animal immunity and decreasing the disease challenge. Successful preconditioning programs combine effective immunization techniques with management tools such as fenceline weaning to reduce animal stress. Veterinarians play an important role in assisting producers by preparing a calf wellness program for the farm.