Author: Dr. Susan Kerr, WSU Regional Livestock and Dairy Extension Specialist Dr. Susan Kerr, WSU Regional Livestock and Dairy Extension Specialist
Publish Date: Winter 2017
There seems to be a resurgence of interest in small- scale/backyard/family dairies. Several breeds of dairy cows, goats, and even sheep are well-suited to this type of management system. Dairying involves a huge commitment of time, labor, infrastructure, and finances for many months; it should not be undertaken on a whim. Caring for dairy animals is not a lifestyle for those who like to travel, be spontaneous, or be away from home for extended periods. However, dairying can be a rewarding experience for those who enjoy routines, staying home, and working closely with animals.
Selecting the best species and breed for a given situation will depend on daily consumption (unweaned livestock offspring and humans), interest in making cheese for long-term milk storage, integration with other farm operations (e.g. pig production) and opportunities for legal sales. A future article will delve into this issue in more depth; this issue will focus on milking practices.
Quality Milk Starts with a Clean Environment
When dairy animals lie down, their udders are in direct contact with the floor. It is crucial that this surface be clean, dry, and comfortable. The risk of mastitis (udder inflammation and/or infection) increases greatly in dirty environments. Adequate bedding also helps reduce animals’ nutritional maintenance requirements. Straw, sawdust, or sand bedding should be cleaned of manure daily and supplemented as needed. Resting areas should be situated in areas not prone to flooding or accumulating wetness.
Teat and Udder Anatomy
Knowledge of udder and teat anatomy is needed to understand the milking process. Milk is synthesized from specialized epithelial cells in the udder using nutrients in the bloodstream. As shown in Figure 1, these cells are found in clusters (alveoli), which are surrounded by smooth muscle cells. The milk- producing cells secrete milk into the lumen (open center) of the alveolus. When a dairy animal is properly stimulated, the hormone oxytocin is released from her brain and causes the smooth muscle cells to contract, sending milk from the alveoli into ducts to the gland cistern of the udder, where it is stored until milking or suckling occurs. For optimal udder health, it should be regarded as a milk production system, not a milk storage unit.
The teat sphincter is critical to udder health and protection from infection. Within about one hour after milking, it has contracted and thereby helps prevent bacterial invasion of the teat and udder. If it is damaged by trauma, overmilking, or other poor practices, that portion of the udder is at greatly-increased risk of mastitis.
Interestingly, fear or stress just prior to milking can interfere with oxytocin release and milk letdown. For this reason, the milking area should be a calm and quiet place and animals should not be stressed getting into the parlor. Yelling, loud music, new people, or any changes in the milking routine can interfere with milk letdown.
Characteristics of Good Milkers
Many human factors are involved with an efficient milking process. First, good milkers are patient with animals and pay attention to details. They need to follow routine practices and be observant for any indications of mastitis or other animal health issues. They should wear disposable gloves to help prevent disease transmission from humans to animals, animals to humans, and animal to animal. Milkers must understand the importance of each step in the milking process and recognize that taking shortcuts puts animal health and milk quality in jeopardy. If children are milkers, they must be taught what constitutes normal and abnormal milk and to contact an adult if they observe any problems. Animals can die from mastitis.
Getting Ready to Milk
Long udder hairs should be clipped regularly to help keep udders clean. If udders are visibly dirty, they should be cleaned with dry paper towels if possible. When possible, avoid using water to clean udders because water will travel down the dirty udder onto the teat, possibly contaminating the teat opening. If it is necessary to wash the udder, use a disinfectant wash and dry the udder and teats thoroughly before continuing with the pre-milking protocol.
After teats are visibly clean (no obvious dirt or manure), apply a pre- dip half-way up the teat, ensuring a drop is observed hanging from the teat end. Pre-dips are commercial preparations proven to be effective germicides. Common products include chlorhexidine or one-percent iodine. Products must be licensed for this use; organic producers should contact their certifying organization to confirm use of approved products. Pre-dips can be sprayed on or applied with a dip cup; the former method is more sanitary but the latter is more effective. If dip cups are used, they should be stored in sanitary locations, dumped and cleaned if visibly contaminated, and disinfected periodically.
Leave the pre-dip on for the amount of time specified by the manufacturer—this is often about 30 seconds. After that, thoroughly remove the pre-dip by drying the teat with a new paper towel or clean, single-use towel; pay particular attention to cleaning and drying the teat end.
Fore-milked is Forewarned
After removal of the pre-dip, milk three or four squirts of milk onto a strip cup (Photo 1). This is a container with a black strainer that helps identify animals with abnormal milk. Also, it is good to remove these first squirts of milk because they tend to contain the highest number of inflammatory cells if they are present. Never check milk by squirting it onto the floor or your hand or boot—this is a good way to spread mastitis.
The California Mastitis Test (CMT) is an easy way to check for subclinical (not visible) mastitis (Photo 2). The CMT system involves a plastic paddle with four cells (one for each quarter of a dairy cow). Three or four squirts of milk are placed in the respective cells and an equal amount of the CMT reagent is added to each cell. The paddle is gently swirled to mix the milk and reagent. The reagent reacts with DNA from cells. Normal milk has no bacteria and few somatic (body) cells so the CMT result for normal milk will be normal (color and consistency will not change). Abnormal milk has more somatic cells (inflammatory cells and more shed epithelial cells, plus perhaps bacteria), so the reagent will cause this milk sample to darken and thicken into a gel. Such a result is evidence of mastitis and a veterinarian should be consulted.
Time to Milk
Whether milking by hand or machine, milking should start 60 to 90 seconds after pre-dip removal from teats. This amount of time has been shown to be optimal for oxytocin to cause milk letdown. It is easy to tell when a hand-milked udder is empty: no more milk can be expressed. Machine milking is easier on human hands, but can result in overmilking and teat-end trauma if done improperly. Excessive vacuum pressure, leaving milking units on too long, not disinfecting units between animals, and detaching the unit with vacuum still present are just some ways machine milking can increase the risk of mastitis. Veterinarians and milking machine distributors can advise dairy producers about best practices for machine milking.
If there are multiple dairy animals on the farm, the youngest should be milked first and any with mastitis, high somatic cell levels, or known history of mastitis should be milked last. Milking units should be cleaned and disinfected between animals; if hand milking, don clean disposable gloves between animals.
Post-milking
Immediately after each animal is milked, her teats should be dipped with another germicide made for this purpose. This product will reduce the risk of bacteria entering the teat opening until the teat sphincter closes. This product is left on until the next milking. In very cold weather, however, leave the post-dip on for 30 seconds, then dry the teats or they may get frostbitten. If animals are habituated to going to a feeding area that is protected from wind and standing and eating for 30-60 minutes after milking, this will help protect teats and reduce the risk of new mastitis cases.
Iodine-based products will leave the teats looking orangey-red; those unfamiliar with dairy animals sometimes mistakenly think that milking makes dairy animals’ teats “bleed,” when in reality they are just seeing teat dip. Make the effort to educate farm visitors about the facts of dairying when you can!
Paper or Cloth?
When it comes to drying teats, should one use paper or cloth towels? Either is acceptable and both have their pros and cons. Paper towels are easy and promote sanitation via one-animal, one-use. However, they are an ongoing expense and generate more trash. Cloth towels are a longer-term investment and can be re- used, but involve labor to wash, dry, and store. If cloth towels are used, they should be washed in hot water after each use, bleach added during the rinse phase, dried in a hot dryer, and stored in a clean covered area until use. Whether paper or cloth are used, it is critical to use one towel per animal only.
One More Time
The major goal of milking is to milk clean, dry, and properly-stimulated teats. This allows the most efficient harvesting of milk and reduces the risk of new mastitis cases. Paying attention to proper milking protocols every time also helps ensure the production and harvest of a high-quality, nutrient dense food animal product.