The Health Management Program in Dairy Cattle
The goal of health management programs is to ensure the optimal care and well-being of dairy cattle and to reduce losses in productivity caused by disease and management errors. The health management program is generally developed cooperatively by the herd veterinarian and the dairy producer based on comparisons of herd performance with predetermined performance goals. The structure of health management programs is unique to each farm but is typically keyed to the scheduled veterinary herd visits that combine routine reproductive examinations, review of selected herd performance records, and decisions and actions related to specific herd management issues.
The frequency of scheduled veterinarian visits is somewhat dependent on herd size. In herds of <100 cows, one or two cows calve every week and a single, scheduled monthly visit is probably appropriate. These herds may have more unscheduled visits for examination of sick cows than herds visited more regularly. Larger herds in which cows are calving daily warrant more frequent visits, and weekly scheduled visits are not uncommon for herds of >200 cows. A trend on extremely large dairy farms (>2,000 cows) is employment of a full-time staff veterinarian to oversee and direct day-to-day issues regarding health and performance. The frequency of scheduled herd visits for grass-based seasonal dairy operations varies depending on the herd’s stage of lactation. More frequent visits are necessary in early lactation and during the breeding period.
Activities at herd visits fall into four general categories: provision of individual animal health care and emergency services, scheduled technical activities, scheduled analytic and training activities, and provision of quality control programs. The frequency of individual activities varies.
The examination and treatment of individual animals is an important activity during scheduled dairy visits. Frequent herd visits allow practitioners to examine cows early in the course of disease when the likelihood of successful treatment is higher. Routine visits also allow veterinarians to monitor the outcome of treatments and modify treatment protocols as needed. Ideally, monitoring programs include a system to detect cows not performing as expected. Special attention should be paid to the highest-risk cows, including frequent observation of animals during the periparturient period. Some farms have adopted a system that includes routine daily monitoring of body temperature and rumen activity of cows during the first 7 days after calving. Animals that fall outside normal limits are treated according to predefined criteria or detained for examination by the herd veterinarian. All treatments administered to dairy cows should be recorded in treatment logs (either computerized or handwritten) to ensure adherence to proper meat and milk withholding periods. The frequency of unscheduled visits for emergency medical services usually diminishes in herds that have adopted a health and production management program.
Routine reproductive examinations account for much of the veterinarian’s time during scheduled herd visits. Attaining reproductive success is an essential determinant of herd productivity. For a description of reproductive programs, see Management of Reproduction: Cattle. The end point of reproductive examinations should be to identify nonpregnant cows that can be returned to the breeding program and to generate data that can be used to determine the success or failure of breeding programs. The implementation, success, and cost-effectiveness of scheduled breeding programs should be reviewed frequently.
On smaller farms, it is often customary for the veterinarian to perform routine individual animal treatments (such as IV injections), prophylactic activities (such as vaccinations), and some technical tasks (such as dehorning calves) during scheduled herd visits. It is appropriate for the veterinarian, or a technician under the veterinarian's supervision, to perform these tasks, because the farm staff may not perform them often enough to become technically proficient. On larger farms, these tasks must often be performed on a daily basis; in this case, farm employees should be trained to accomplish these tasks.
Conducting scheduled or unscheduled technical activities will not be effective unless a system exists to capture the results of the activities and allow for analysis and ongoing revision. The structure of the health and production management program must include time for the farmer and the herd veterinarian to analyze and discuss herd management issues. In herds that depend on hired personnel to implement designated tasks, time must be scheduled to observe and effectively train personnel ultimately responsible for performing the activities. Development of standard operating procedures is one method to ensure that agreed-on practices are implemented.
Treatment protocols are used to define standard treatments for common diseases on dairy farms and should be used when multiple people have responsibility for administering antibiotic treatments to dairy cattle or when extra-label drug use is prescribed. They also provide a mechanism for increased communication about treatment plans between the veterinarian and producer.
The avoidance of residues in food products is a major responsibility of dairy practitioners. Increased scrutiny regarding antimicrobial use in food-producing animals has arisen because of concern about the development of antimicrobial resistance in foodborne pathogens. Although the level of detected antibiotic residues in meat and milk products is extremely low, antibiotic residues in bulk milk and carcasses are seen occasionally. In the USA, contamination of bulk milk is rare because of an effective surveillance system based on rapid testing for selected antimicrobial agents of every load of raw milk. Milk contaminated with antibiotics is discarded, and the producer is fined.
The requirements for extra-label drug use in the USA have been defined by regulatory officials under the Animal Medicinal Drug Use Clarification Act and should be closely followed. The American Association of Bovine Practitioners has responded to societal and regulatory concerns about the use of antimicrobial agents by adopting recommendations for the prudent and judicious use of antimicrobial agents in dairy cattle. In response to concerns about the development of antimicrobial resistance in human medicine, the FDA is requesting that drug manufacturers begin the process of eliminating the labeling and use of certain antimicrobials for production purposes (to increase feed efficiency or weight gain). Specifically, antimicrobials of importance to human medicine will no longer be permitted to be provided in feed or water solely for production purposes, and no new antimicrobials will be approved for production purposes, although they can be approved for use in feed or water for treatment or prevention of disease. For producers to use an antimicrobial in feed or water, they must receive a feed directive from their veterinarian (essentially a prescription); over-the-counter sales of antimicrobials for use in feed or water will no longer be allowed. See also The Veterinary Feed Directive (VFD).
Some dairy practitioners function as the nutritional specialists for the dairy farms they serve. They may collect feed samples for nutrient analysis, formulate rations, and advise the farmer regarding crop and harvesting conditions. These veterinarians often devote a considerable amount of their professional time to nutritional management. Other farms employ a professional nutritionist or use a nutritionist employed by a feed company or local cooperative to formulate the rations and submit feed samples for nutrient analysis. Regardless of the source of the dairy’s nutrition program, the veterinarian can perform an essential oversight function simply by observing body condition and general health in cows in certain high-risk areas (periparturient and high milk production), monitoring the incidence of nutrition-related diseases such as parturient hypocalcemia and displaced abomasum, and ensuring that the diet described on paper is adequately formulated and delivered to the cows. Assessing pasture conditions by periodic inspection of pasture is an important component of managing the nutritional program of herds that use management-intensive grazing. These quality control activities should be conducted routinely as part of the health and production management program.
Quality control refers to activities that ensure consistency in performing key management processes. Vital management areas for most herds include nutritional management, milking management, and young-stock programs. Some farms may also develop quality control processes for environment and housing and farm-specific management of breeding bulls.
Milking management should be a standard element of quality control programs. Tasks such as observing the milking routine and scoring the condition of teats should be performed at least quarterly. A scheduled system of routine screening for mastitis pathogens can be implemented as part of the milking management program. The veterinarian can teach farm personnel how to perform the California Mastitis Test as part of a surveillance program. Animals routinely screened may include cows at dry off, fresh cows and heifers, and newly purchased cows. Milk samples can be collected and submitted for culture from quarters that show positive reactions.
Newborn calves and replacement heifers are often housed separately from lactating cows and may not be observed routinely by the herd veterinarian. However, routine surveillance of critical management issues such as adequate delivery of colostrum to calves and growth rates of replacement heifers can be done as part of scheduled herd visits. The environment of dairy cattle can have considerable influence on health and productivity. Some veterinarians routinely schedule “walkabouts” through the housing areas to assess factors related to animal comfort and hygiene. Udder cleanliness, hoof and hock lesions, and respiratory disease are often determined by housing conditions. Herd walkabouts should include areas often ignored, such as dry-cow and heifer housing.
Performance targets reflect herd standards of performance that are perceived as indicators of successful herd management. They are useful as comparison values for herd performance and as a starting point to initiate discussions about potential areas for improvement. To use a performance target, it is necessary for a herd to have a record system that allows for generation of comparable herd indices. In many instances, performance targets have been calculated as arithmetic averages, which are useful indicators of herd performance when the contributing data (such as milk, fat, and protein yields) are normally distributed and have a reasonable degree of variation. However, many reproductive indices and values such as SCCs are not distributed normally, and erroneous conclusions about herd performance may be made if averages alone are used to make management decisions. Appropriate frequency distributions are more useful for these types of data.
Key indicators for performance targets should be defined. The monitoring system should specify the indices used, the animals included, and the time interval to reassess progress made toward reaching each target. Typical performance indicators include milk production, reproductive performance, milk quality, replacement management, cow removal, animal health, and special reports (see Table: Examples of Activities for Routine Monitoring a). Performance targets should be reviewed at appropriate intervals with realistic expectations regarding the amount of time it takes to effect change in an index. For example, management actions taken to reduce days to first calving would require ≥9–10 mo to become apparent. A more timely value such as age at conception would more rapidly reflect current management changes.
Examples of Activities for Routine Monitoring a
A system of unique individual cow identification is a prerequisite for a successful health management program. The most common methods of animal identification are ear tags, collars, and branding. Increasingly, farms are using electronic identification via transponders on ankle bands or neck straps. At a minimum, data must be recorded on birth, breeding, and calving dates and periodic milk yield. Under ideal circumstances, summarized data should be available for the nutritional program, disease occurrence, and financial performance.
Record analysis is a necessary component of the health management cycle. Most or all dairy herd improvement (DHI) systems allow for electronic access to performance data, and various computerized systems for herd management are used throughout the industry. Most monitoring systems can be characterized broadly as one of the following: 1) manual (handwritten) card systems, 2) on-farm computer programs, 3) DHI, or 4) DHI and on-farm computer. Regardless of the type of system used, it should be easy to use and relevant to the day-to-day operations of the dairy.
One important function of record systems is the generation of “action” lists (due to calve, due to dry, etc). This function is critical in large herds in which cattle are not individually known by the animal handlers and can be overlooked easily. Most systems also provide for a minimal level of herd analysis, such as the generation of timely performance reports for production, reproduction, and disease. Some programs can also generate statistics. The record-keeping system should allow the producer and veterinarian to understand and modify the formulas used to generate herd performance indices. For parameters and values used to monitor herd health and production see Table: Parameters Useful to Monitor Health and Production of Dairy Herds.
The veterinarian should ensure that collected data are used in a timely manner. Accurate data collection is most likely when the producer is using the data frequently and understands its value. The validity of data generated from both manual and automated data collection systems should be reviewed and critically assessed. Unusual results and deviations from normal performance targets should be challenged. The producer and the veterinarian should agree on defined actions based on the herd status and goals. Actions are generally diagnostic, preventive, or treatment oriented. Typical activities might include listing animals for routine herd fertility or illness examinations, or selecting cows to obtain milk samples for culture, to vaccinate, to consider culling, to breed, to receive body condition scoring, or to receive treatments.
Parameters Useful to Monitor Health and Production of Dairy Herds
Even on the best managed farms, unexpected health and production problems arise. Surveillance programs incorporated in health and production management programs should detect problems early, before considerable financial damage has occurred. Systems to investigate herd outbreaks have been described. Epidemiologic concepts of disease investigation are useful to identify risk factors and to stimulate corrective action.