Muddy conditions resulting from wet weather constrain best management practices; animals, feed and the environment can all be negatively affected. Under these conditions, two major ailments can affect dairy cows: mastitis due to environmental bacteria and lameness. Cows with mastitis decrease production, have greater treatment costs and can eventually be culled or die. Lame cows incur higher production losses, lower fertility and greater culling rates.

Environment and lameness
Mud is one of the predisposing causes for cattle lameness. Wetness decreases hoof hardness and increases the incidence of claw lesions. Research has shown that nearly one-third of the total water absorbed by a hoof is during the first hour of exposure to high-moisture conditions, resulting in softer hooves. Other management factors such as subclinical acidosis and its clinical manifestation, laminitis, may result from nutritional or even management errors.

Wet bedding reduced the time that cows spent lying by five hours per day and increased the time spent perching with just two feet in the stall. Reduced amounts of bedding or replacing the bedding less often leads to cows standing for longer periods of time, increasing stress on hooves.

Also among the determinant causes of lameness associated with wet conditions is the presence of infectious agents such as Fusobacterium necrophorus and Bacteroides melaninogenicus, which cause foot rot and digital dermatitis (hairy heel warts), which is most likely caused by spirochetes.

Footbaths
Keeping hooves as dry as possible should be a priority. The current approach is to find ways to decrease the incidence of injury and infectious challenge to the hoof using footbaths and hoof trimming. Footbaths are used to medicate the feet of cattle and aid in preventing lameness.

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The most common medication added to footbaths is copper sulfate, followed by formaldehyde (formalin), and then oxytetracycline. Copper in footbaths should be added at 2.5 to 5 percent (62 gallons of water and 26 pounds of copper sulfate). Dairies that use copper sulfate should test soil to check for copper loading in cows and milk, because cows will frequently drink from the bath.

The footbath solution should be replaced often and maintained free of organic matter, as it inactivates the copper in the solution. Formalin, a solution of roughly 37 percent formaldehyde, can be hazardous to human health causing irritation of eyes, nose and throat, and burning the skin (these symptoms can also happen to cattle if not used at the right concentration). Formalin solution should be used at 4 percent (one gallon of 37 percent formalin with 10 gallons of water).

To get a better handle on foot health and develop a hoof-health management plan, a 5-point locomotion score scale has been developed. This scoring system is based on observing cows as they are standing or walking, with special emphasis on the posture of the back. This is an effective method for early detection of hoof disorders, monitoring lameness prevalence, comparing the incidence and severity of lameness between herds and identifying cows that need hoof trimming.

The observation must be performed on a flat surface that provides good traction. Always score the cows in the same location and in level terrain.

Trimming
Hoof trimming helps identify hoof disorders and maintains proper hoof health. When hooves are not trimmed regularly, they can grow unevenly, resulting in weight-bearing changes that can damage the underlying tissues. How often a hoof trimmer is needed usually depends on the number of cows to be trimmed.

Environmental bacteria and mastitis
In the cow’s environment (e.g., bedding, soil, manure, etc.) are countless bacteria that, when given the right conditions, will invade the udder and cause mastitis. As the bacteria are almost impossible to eradicate completely, one has to learn to reduce their effects by improving cleanliness of both the cows and their surroundings.

The coliform group is represented by E. coli, Klebsiella spp, and Enterobacter, which originate in manure and soil, and the environmental streps: uberis and dysgalactiae. This last group is in both the environment and the udder and can thus be transmitted from infected to clean cows through faulty milking practices.

For environmental bacteria to grow, they need an organic substrate (i.e., manure) and high moisture. If cows are allowed to rest on humid, soiled bedding, or if they are allowed to wade through mud or contaminated water, these bacteria can potentially enter through the teat canal.

When teats are not properly disinfected or dried thoroughly, drops of this contaminated water can enter the teat canal. This can be worsened if the inflations of the milking machine do not adjust properly during milking. Air that gets between the teat skin and the liner during the pulsation sequence can project contaminated drops at great speeds through the teat sphincter.

Following a strict and sound milking routine is critical to minimize the chances of contaminating the mammary gland. Although the first instinct when cows arrive covered with mud is to wash the udders and remove the dirt, it is oftentimes better to just “dry clean” them. Concentrate on cleaning the teats themselves and not the whole udder.

The use of nitrile gloves should be given high priority. Gloves need to be maintained reasonably clean during the milking procedure. They do little good at protecting the cow from bacterial contamination if they are covered with manure.

Forestripping
Forestripping (three squirts per teat) is important because it accomplishes several tasks. Forestripping stimulates milk letdown, helps detect abnormal milk and removes the most highly contaminated milk from the tank

Pre-dipping
If one were to rank the step of the miliking procedure by importance in decreasing mastitis incidence, teat dipping would probably be No. 1. It is important to use teat dips approved by the FDA with a demonstrated bactericidal effect. It is important to achieve coverage of the entire teat barrel and allow at least 30 seconds between applying the dip and drying.

Drying
Successful drying of the teats also follows certain rules, the first being single-use towels or “one towel, one cow.” Cloth towels work very well if they are clean, dry, and not worn out. At a minimum, hot water or hypochlorite should be used to wash towels. If there’s a problem with the drying process, the addition of hypochlorite is warranted.

Reusable drying cloth towels that are not properly cleaned may be a source of infection. Even when these towels are initially clean, the sequence in which the teats are dried may result in inadvertently cross-contaminating them. If teats closest to the milker are cleaned first, those teats may be accidentally contaminated while trying to reach the back teats.

Post-milking
Once the unit is detached, cows should be post-dipped immediately. The reason for this is that the sphincter of the teat canal remains open for awhile, and it is easy for bacteria to penetrate the udder.

Infections
Cows infected with coliform bacteria can show clinical signs and progress to an acute form that can lead to the death of the animal. These cases have sudden onset, with swollen and hot quarters and yellowish, watery milk that contains clots and flakes. Severe cases occur in early lactation, particularly around calving.

Infections with environmental Streptococci, Klebsiella and Enterobacter occur more frequently early in the dry period. On the other hand, E. coli infections tend to occur immediately before and after calving. It is thus important for both far-off and close-up dry cows to be kept in lots with dry, clean bedding.

Several udder health management strategies are recommended for the dry period including dry cow antibiotic therapy, teat sealant for dry cows, environmental management, nutrition, drying off method and vaccination programs. Management practices are without doubt among the most cost-effective practices when dealing with environmental mastitis. PD

References omitted due to space but are available upon request to editor@progressivedairy.com.

—Excerpts from South Dakota State University Extension website

Alvaro Garcia