Winter conditions present a particular challenge on the farm. A degenerative cycle begins when environmental conditions cause the skin to become dehydrated. Cold air carries less moisture than warm air and thus accelerates moisture loss. When the skin’s moisture barrier is disrupted, the lipids between the cells of the stratum corneum (Figure 1) are affected, leading to a loss of “natural moisturizing factors.”
Natural moisturizing factors are amino acids that act as internal humectants within stratum corneum cells. Once the moisture barrier is disrupted, the skin begins to dehydrate even faster, causing a positive feeding loop. Skin cell overproduction takes place in an effort to compensate for the disrupted barrier, and exfoliation (the skin’s natural renewal process) slows down. This results in thickening of the skin (hyperkeratosis) as old cells accumulate, forming a brittle flaking layer we see as “dry skin.”
Dry skin inhibits skin’s ability to hydrate itself, renew its outer layers, replenish the stratum corneum’s natural moisturizing factors, repair its moisture barrier and protect against microbial colonization.
The teat skin is important in maintaining a natural defense against microbial infection. It also has a high density of nervous terminations that detect teat stimulation and cause milk letdown. Improvement and maintenance of teat condition can affect the ability of bacteria to colonize the skin, impact milk letdown, milking speed and overall milk production. Rough skin provides more places for bacteria to hide and survive, increasing the potential for contamination of the teat canal.
Teat disinfectants are provided in a variety of product types and wide array of formulations. Each product type and formulation serves a specific purpose. Products may be concentrates or ready-to-use, be formulated for use prior to or post-milking and have additional components to impart an additional property such as a physical or chemical barrier. The opportunity to affect teat condition through a teat disinfectant is greater for post-milking applications, as they have a longer contact time with the teat.
All teat disinfectants must meet a minimum set of characteristics regardless of their specific application. Teat disinfectants must provide a broad spectrum of antimicrobial activity, be non-irritating to teat skin, and be both physically and chemically stable. However, the relative importance of other characteristics depends on the intended use and mode of application of the teat disinfectant.
For example, wetting is more important on pre-dips, where the intent is to help with soil removal in addition to providing antimicrobial protection. Similarly, foaming may be desired for manually applied teat disinfectants but not for those applied by mechanical spraying. In the case of winter dips, the following are critical characteristics:
The viscosity of a teat sanitizer varies depending on the intended application, with pre-milking applications being less viscous than barrier formulas (1 cP versus 500 cP). Increased viscosity not only results in a thicker layer of product on the teat but also may slow down evaporation. Damages to teat-end integrity, potential for skin chapping, frostbite or even freezing increase in wet teats exposed to wind chill and low temperature environmental conditions.
Specific teat conditioning agents (emollients) are added to teat dips to mitigate any adverse irritating effects of other ingredients in the formulation such as surfactants used for wetting, or active ingredients with acidic or non-neutral pH. Skin conditioning agents either provide moisture (humect) to the teat or provide a barrier to prevent moisture loss.
Moisturizers work by attracting moisture from the air and adding that moisture to the outer layers of the skin. Common moisturizers include glycerine (glycerol), propylene glycol, sorbitol and aloe. Teat dip formulations can use these moisturizers alone or in combinations. The concentration in the formula depends on the specific use. In the case of winter dips, emollients are formulated at concentrations as high as 50 percent.
Not all moisturizers have the same moisture-binding capacity, with glycerine being the most efficient. However, glycerine is difficult to keep in solution and tends to leave more of a tacky feel on teats.
Moisture barriers prevent the evaporation of moisture present on the skin. Common moisture barriers include lanolin, petroleum jelly and mineral oil. Of these, only lanolin derivatives are water-soluble and thus used on teat disinfectant formulations. They are typically used at concentrations below 1 percent.
Stability of the formula
Teat disinfectants formulated for use during winter conditions tend to be heavily built formulas. They contain a variety of components at relatively high concentrations. The potential physical and chemical interaction of these components needs to be carefully examined during the formulation stages. While mastitis-causing pathogens are mesophiles (Figure 2),
and prefer to grow at or close to mammal body temperature (98.6ºF), they are capable not only of surviving but also growing at lower temperatures (Table 1).
In addition to specific precautions when formulating teat disinfectants for use during winter conditions, there are also important herd management factors to take into account. Specific teat disinfectant application parameters during winter aid in the maintenance of healthy teats. Wet teat skin as cows enter cold and windy conditions, accelerates heat loss and tissue freezing.
When the outside temperature is below freezing, it is important to allow the teat disinfectant to dry for at least one minute before releasing the animal from the milking parlor. If the teat disinfectant is still wet, it can be pat dried with a single-use paper towel.
The requirement for a one-minute contact time allows for sufficient exposure of the bacteria to the biocidal active, allowing for effective reduction in microbial load on the teat. In addition, identification and management of cows with increased risk is paramount. In particular, low herd ranking may force heifers into locations with higher exposure to the elements. While fresh cows with large udders or distended teats may be more exposed to heat loss and tissue freezing.
Preventing problems during cold weather is mainly a herd management activity, including protection from wind; ensuring clean, dry bedding in freestalls; and choosing the correct teat disinfectant with fast-drying (to prevent additional moisture loss) and higher emollient content to maintain skin moisture as priorities.
Carolina Mateus is a research and development director over milk quality and animal health at DeLaval.