Animals can be reservoirs for important food-borne and waterborne infections. Both milk and water can carry these pathogens as well as contamination from antibiotics resulting from treatment of animals. Examples of pathogens found on dairy farms which can cause serious health problems include E. coli, Listeria, Staphylococcus aureus, and Cryptosporidia. Some of these infections in cattle, such as E. coli and Staph. aureus do not respond well to antibiotic therapy.
The food industry has implemented a program called Hazard Analysis Critical Control Points (HACCP) as a course of action to ensure safe food by controlling the complete production process. This is done by identifying where problems may develop and then developing strategies to prevent them rather than detecting problems at the end of the line. Under HACCP, a food plant analyzes its processes to determine at what points hazards might exist that could affect the safety of its products. These points are called critical control points (CCPs). Once CCPs are identified, the plant must establish critical limits. Next, the plant establishes monitoring requirements for each CCP and corrective actions that must be taken when monitoring indicates there is a deviation from an established critical limit. The plant must also establish record keeping procedures that document the operation of the HACCP system and verify that the controls are working as intended.
HACCP concepts can be used on the dairy farm. This is often referred to as “preharvest food safety.” For example, abnormal milk, the presence of antibiotic residues in milk, and milk cooling have been suggested to be critical control points. According to Jim Cullor (University of California, Davis), probable on-farm critical control points for many pathogens include: (1) housing and bedding; (2) water and waste management areas; (3) hospital pens, calving pens, and treatment areas; (4) bulk tank milk; and (5) young stock and cull animals. It does not seem logical to develop different management strategies for each potential pathogen. It would be useful to adopt management practices that result in an overall control of the multitude of pathogens.
Let’s look at a possible checklist which can be used to match management practices to a reduction of pathogens on the farm in order to avoid the incidence of abnormal milk. Some of the practices apply to only food-borne or waterborne pathogens while some apply to both categories.
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Pathogen Risk Assessment and Reduction:
___ Use disease control programs that have been developed in conjunction with the herd veterinarian.
___ Use hospital pens and calving pens, cleaning them out after each animal if possible.
___ Monitor for mastitis using bulk tank somatic cell counts (SCCs), milk cultures, and DHI or similar programs; culture cows with clinical mastitis or a high SCC.
___ Handle and dispose of abnormal milk in a proper manner.
___ Culture a milk sample from all purchased animals and test for mastitis before adding to the herd.
___ Use an effective fly control program.
___ Prevent suckling among calves.
Pathogen Intervention/Management Strategies:
___ Minimize exposure by keeping pathogen levels low.
Keep animals clean, dry, and comfortable. This includes water, feed, bedding, and ventilation.
Cull or segregate infected animals, especially mastitis-problem cows.
___ Minimize transfer of potentially harmful pathogens.
- Workers should wash hands often, especially after handling sick animals and before eating.
- Do not allow direct contact of infected and “at-risk” animals, such as youngstock.
- Do not allow handling of different species of animals without assessing the potential disease risk and proper prevention protocol. For example, it is suspected that a mycoplasma mastitis problem in a dairy herd originated in purchased beef cattle brought onto the farm.
___ Who does treatments? If done by more than one person, a well-defined notification process is needed. Written records of all treatments are essential.
___ What will the treatment be for predictable illnesses?
- Will treatment be based on different mastitis signs shown at milking?
- Have these been developed with input by the herd veterinarian?
- Are the treatment protocols clearly outlined and available in a readily accessible location?
___ Treat with single-use, commercially prepared infusion products approved for the disease being treated, properly disinfecting the teat end before treatment.
___ How are treated animals identified? Multiple identifications (two or more) are strongly recommended for a treated animal.
___ What steps are taken to ensure no contaminated milk or meat is sold?
- Is milk withheld from fresh cows for an adequate length of time?
- Are topical antibiotics used for lameness, etc.?
- Are systemic antibiotics used?
- Are appropriate antibiotic residue test kits used as necessary?
___ What are the preventive treatments and vaccinations that are done with specific procedures?
- Dry treat all milking animals at dry-off.
- Bred heifers infused with dry or lactating mastitis treatment if determined to be necessary and under veterinarian’s guidance.
- Vaccination programs for both young and adults, including dry cows (eg, E. coli).
___ Maintain and enhance the immune system of the animal.
___ Use vaccination programs to protect against preventable diseases.
___ Maintain individual animal health records.
___ Avoid conditions of high stress. Maintain proper nutrition.
___ Protect defense mechanisms of the animal (e.g., keratin); keep cows standing for a minimum of 30 minutes after milking.
___ Feed balanced rations; pay extra attention to vitamin E and selenium in late dry cows and bred heifers.
___ Prevent bacterial contamination of feed by rodents or birds.
___ Clean, safe drinking water should be available at all times. Keep waterers clean and maintained.
___ Potable water should be available to the milk room and related areas.
___ Water should be tested regularly and found satisfactory.
___ Maintain a clean, dry, and comfortable environment and adequate housing including dry cow and calving areas, preventing teat contamination between milkings, by avoiding damp, muddy areas or stagnant pools or ponds.
___ Limit exposure to contaminated bedding, muddy areas, and stagnant water.
___ Avoid overcrowded conditions.
___ Reduce stress causing conditions that result in susceptibility to disease.
___ Be aware of milk films containing contaminated bacteria (biofilms) on surfaces, such as gate handles in the milking parlor, routinely sanitize these areas with disinfectant.
___ Be aware of areas with the potential of containing a heavy concentration of bacteria.
___ Minimize presence of rodents and birds.
Milking Hygiene and Proper Milking Procedures are Critical
___ Check foremilk for abnormalities.
___ Milk clean, dry teats that have been predipped with a tested product.
___ Dry teats using a single-use towel (paper or cloth).
___ Infected cows and animals secreting abnormal milk should be milked last or with separate equipment or backflushed teatcup liners. Abnormal milk should be discarded.
___ Attach milking units in a timely fashion.
___ Minimize liner slippage.
___ Disinfect teats after milking with an effective product; teats should be dry before cows exit to cold areas.
___ Discard unused dip from recirculating dip cups, and clean dip cups after each milking.
___ Check milk filter for dirt at end of milking.
___ Make provisions to keep treated milk from entering bulk tank.
___ Regularly review milking procedures with all personnel who milk.
Milking Equipment – Use Correctly Designed, Maintained, and Cleaned Equipment
___ Have entire system evaluated during milking time by a competent technician or specialist, in accordance to the Milking Machine Manufacturer Council guidelines.
___ Repair, replace, or upgrade any components before they are worn out.
___ Clean equipment after each milking or a minimum of twice a day.
___ Sanitize equipment before milking according to supplier recommendations.
Milk Storage and Cooling:
___ Bulk tank washed and sanitized after every pickup.
___ Surfaces clean, with no evidence of milkstone or protein deposits.
___ Outlet valves, agitators, bridge surfaces, and gaskets around the manhole clean with no evidence of milkstone or protein deposits.
___ Cleaning and sanitizing program developed and followed.
___ Temperature of the milk decreases to 50°F within one hour of milking and to 40°F or less (36°F recommended) within one additional hour.
___ Blend temperatures remain below 45°F at all times during the second and subsequent milkings.
___ Does milk from first milking freeze before agitator runs?
___ Check calibration of tank thermometer.
___ Agitator(s) run at least 5 minutes every hour.
___ Is it possible for contamination to occur due to condensation from dripping pipes and ceilings?
___ Is care used in rinsing the top of the bulk tank to prevent the entrance of water when milk is present?
___ Is milkhouse area free from dust or dirt that might be drawn into the area around the cooler condenser unit?
___ Is last rinsing of the bulk tank, before milking, done with an approved sanitizer in the proper concentration?
___ Bulk truck and personnel access that allows for milk pickup in a clean area.
___ Drainage of external water away from animal housing, milking, and milk storage areas into proper waste storage or disposal.
___ Proper waste handling systems for restrooms – not liquid manure storage.
___ Animals kept from milking center wastewater and manure storage areas.
___ Fly population controlled (minimizing breeding areas, spraying, etc.)
___ Manure and milking center wastewater managed to minimize flies, odors, and to protect water quality.
Animal Resting Area
___ Clean, dry, and comfortable
___ Easy access to feed and water.
___ Cows can comfortably recline, lie, and rise in natural manner.
___ Are the cow resting areas readily used?
___ Adequate dimensions.
___ Clean, dry comfortable area for two weeks after drying off and before freshening.
___ Feeding program managed to minimize metabolic diseases.
___ Use dry cow treatment and treat all animals at dry-off.
___ Clean, dry, comfortable.
___ Segregated from other animals.
___ Utilities (lights, hot, and cold water) available for care of animals requiring additional medical attention.
Animal Travel Lanes and Standing Surfaces
___ Durable, easily cleanable surface.
___ Cleaned regularly.
___ Liquids not accumulating on surfaces.
___ Provides traction for animals and workers.
___ Wide enough lanes to prevent congestion.
Unpaved – pasture, dry lots, exercise lots, lanes
___ Lanes stabilized and graded to prevent mud holes.
___ Lanes wide enough to accommodate animal traffic and allow for easy maintenance.
___ Maintained and used to keep animal clean.
___ Wide enough to allow animals to maneuver and to minimize congestion.
___ Appropriate crossing for waterways.
___ Pasture layouts that prevent mud accumulation at watering and/or supplemental feed areas.
___ Proper facilities and management to keep animals out of wet areas.
___ Pastures managed to maintain adequate plant growth.
___ Areas, as required by milk regulations, have durable and easily cleaned surfaces.
___ Buildings properly maintained.
___ Bird- and rodent-resistant construction.
___ Maintain facilities to discourage rodents.
___ Adequate general day and night levels for cows and workers to move around safely.
___ Sufficient illumination of udder in milking area.
___ Sufficient illumination at areas where proper animal identification is critical (e.g. to identify treated animal in milk string).
___ Extra lighting as required for cow examination and treatment and for cleaning and examining milking equipment.
___ Suitable device properly installed and maintained for restraining animals.
___ Operator has good safe access to cows for udder examination, cleaning, and machine attachment.
___ Area kept clean.
___ Minimal manure accumulation.
___ Milk contact items stored in a clean, safe area that prevents contamination.
___ Proper storage of cleaning materials, milking supplies, and related items and drugs.
___ Provisions for cleaning/sanitizing teats.
___ Provisions to keep abnormal or treated milk from entering bulk tank.
___ Chopped, packed, stored at proper moisture content to prevent molds.
___ Completely fermented.
___ Spoiled silage discarded.
___ Harvested, handled and stored to minimize molds and toxins.
___ Spoiled hay discarded.
___ No mold.
___ Stored away from milking area.
___ Spoiled ingredients discarded.
___ Avoid contaminating feed with manure – equipment dedicated or cleaned completely, do not drive on feed in feed alley.
___ Avoid contamination of the feed floor or area.
___ Feed area smooth and easily cleaned surface.
___ Evaluate purchased feed for aflatoxin content prior to delivery.
___ Examine grown feed.
___ Retest feed stored for long periods of time.
Dairy Practices Council Publication 64 – Checklist Of Control Points For Good Management Practices On Dairy Farms.
Dairy Practices Council Publication 69 – Abnormal Milk – Risk Reduction and HACCP
Milk and dairy beef residue prevention protocol. http://www.dqacenter.org/
Gerald M. (Jerry) Jones
Virginia Polytechnic Institute and State University