Milk Safety and Quality in At-Home Processing.

 By Michelle Buckley - Iowa State University

 According to the USDA’s National Animal Health Monitoring System (NAHMS) the number of dairy goat operations nearly doubled between 1997 and 2017 from 75,000 to 136,000 while the average herd size decreased from 29.4 head per farm in 2009 to 19.8 head per farm in 2019. With smaller herds and more farms, more milk and milk products are being harvested and processed in homes.

With smaller herds, home processing and consumption of milk and milk products has become quite popular among dairy goat owners. Proper processing of milk and milk products is essential to maintain the health of the consumer and prevent foodborne illness. Two key components to ensuring a healthy milk product are preventing drug residues in milk and appropriate processing to eliminate any potential contaminates (such as bacteria). Home-processed products do not fall within the oversight of USDA inspectors as do products that are handled at large-scale processing facilities, it is doubly important for producers to understand how to mitigate these risks.

Judicious use of antimicrobials & milk withdrawal info; Use of records to track treatments & withhold times w/ DVM:
There are strict regulations governing drug use in food-producing animals. These species include cattle, goats, sheep, pigs, poultry, and camelids. The goal of these rules is to maximize the efficacy of a treatment, minimize the risk of antibiotic resistance, and prevent consumer exposure to medications through food products.

Goats are considered a ‘minor food animal species’ in the United States—as opposed to cattle, hogs, and poultry—because of their comparatively small population here. Because of this, there are very few drugs that are explicitly labeled for goats. Drugs that are not explicitly approved for a species may be used at the recommendation of a veterinarian with doses and withdrawal periods specific to your animals under the guidance of the Animal Medicinal Drug Use Clarification Act (AMDUCA). Your veterinarian is familiar with this legislation and can help you to determine the most appropriate medications and doses to use for specific illnesses.

Goats are considered a ‘minor food animal species’ in the United States—as opposed to cattle, hogs, and poultry—because of their comparatively small population here. Because of this, there are very few drugs that are explicitly labeled for goats. Drugs that are not explicitly approved for a species may be used at the recommendation of a veterinarian with doses and withdrawal periods specific to your animals.

Every drug that is approved for food animal use in the United States is assigned meat- and milk withdrawal times. This is a set period where meat and/or milk harvested from an animal may not be used for human consumption. Withdrawal periods are created based on extensive scientific research and can be found on the label of any medication that your veterinarian has approved for use in your livestock. Withdrawal periods are listed on the label for the major food animal species for which they are approved. Because goats are generally considered minor food animal species in the United States, your veterinarian will inform you of the appropriate withdrawal period for your animals and print it on the prescription label.

Failure to observe appropriate route, dose, or withdrawal periods can result in human exposure to residual pharmaceutical compounds within the milk or meat tissue. Appropriate animal identification and record-keeping is essential for tracking disease, drug use, withdrawal times, and reproductive metrics—ultimately improving food quality and safety. Maintaining accurate and up-to-date records can also help producers to more accurately evaluate cash flow within the farm, set farm-specific benchmarks, and help producers to determine a fair price for their product. Written records have been utilized for decades, however these are easily misplaced and may be difficult to interpret. Digital records offer the opportunity to simplify record keeping and when combined with digital methods of identification (i.e., RFID tag or microchip) offers ease of accessibility and increased number of trackable metrics with the security of virtual storage. According to the 2009 NAHMS Reference of Dairy Goat Management survey (most recent data available) only 58.6% of dairy goat producers kept records of any kind and 16.5% of producers surveyed kept electronic records. In contrast, the 2014 NAHMS Dairy Cattle Management Practices survey shows that 95% of all dairy cow operations utilized records of some kind and electronic records were used on 94% of large-scale dairies. Along with computer programs such as DairyComp 305 and PC Dart—which can be modified from dairy cattle to dairy goats—multiple smart phone applications exist which can be easily tailored to track desired metrics for farms of any scale. DHIA (the Dairy Herd Information Association) also provides milk testing services and records for dairy goat clients.

Popularity of unpasteurized milk products & benefits of pasteurization:
While commercial sale of raw milk is illegal in 40 states, direct-to-consumer sales are more loosely regulated. Consumption raw milk products has been intermittently popular over the years and goat dairy products have supplied an increasing proportion of this niche market.

Reported benefits of consuming raw dairy products include preventing breakdown of proteins and probiotics. Research has shown that the amount of protein breakdown caused by pasteurization is insignificant in terms of human health effects.  

Probiotics – bacteria found to have beneficial effects on the digestive system—are also touted to be one of raw milk’s primary benefits. It is important to remember, however, that the nutritional and bacterial composition of goat milk changes based on where she is in her lactation as well as her diet. Furthermore, research to identify bacterial strains with known or possible human health benefits has been inconclusive at best. There is currently no scientific evidence that raw milk from any species contains significant levels of “good” bacteria. This ambiguous finding combined with known pathogens that can enter the milk of even clinically healthy animals, makes this a poor argument for consumption of raw milk products. It is important to remember that these bacteria can be transmitted directly from the animal, as well as through milking equipment, debris on the outside of the udder during milking, or even from human contact after it is harvested from the animal. Therefore, evaluating animal and udder health is not an adequate method of ensuring safety of unpasteurized milk products.
Some studies report that up to 1/3 of milk samples from apparently healthy animals result in cultures of bacteria that can result in human illness. These diseases range in severity from gastrointestinal upset to neurologic disturbances. For example, studies show that up to 30% of goats have a subclinical intramammary infection at dry off culture. Coagulase negative staph. is the most commonly cultured group of mastitis and can commonly result in mastitis during the dry period or at freshening. One method of combating this issue is through the use of intramammary antimicrobial treatment and sealant at dry off. With a standard dry period of 30-60 days, the withdrawal period for the intramammary antibiotic will be well past by the time of kidding. Accurate breeding dates, appropriate dry off times, and adequate dry period length are just a few examples of parameters requiring accurate recordkeeping for milk quality and safety.

At home pasteurization techniques:
Pasteurization is the process of heating milk to a specific temperature and maintaining it there for a set period before cooling for refrigeration. The Pasteurized Milk Ordinance provides guidelines for pasteurizing milk at several different temperatures and the corresponding durations.

Small-scale hobby farm and homestead producers may find it easiest to utilize a double boiler system for small-batch pasteurization. The preferred temperature/time combination for this pasteurization technique is 167oF at 15 seconds. It is essential that the batch is stirred constantly in order to ensure uniform heating throughout. Once the target temperature and time have been achieved, move the pan to a bowl of ice water and continue to stir the milk. Add ice to the bowl of water as it warms in order to continue cooling milk.

Small batch pasteurizers can be purchased for home use in varying sizes and price ranges for operations with corresponding needs. These may be appropriate for producers that are milking more than a few goats or who are creating product for public sale.

Milk quality and safety can be complicated topics and your local veterinarian should be consulted for detailed questions related to your specific animals.