By Dr. Curt Vlietstra
While it might seem like this article is a case of “too little, too late,” take heart; Seven months from now, it will be time to prepare for winter again! Historically, we’ve learned that the summer months are the worst for seasonal increases in somatic cell counts (SCC). Truth be told, every winter, many dairy farms struggle with some sort of mastitis/SCC related problems regardless of barn design or bedding. Due to some of the most extreme weather variations and an early start, however, this winter seems to have taken more of a toll than normal. We’ll review some of the key points, and hopefully be more prepared for next winter.
General review on dairy cow mastitis:
- Mastitis is defined as inflammation of the milk producing tissues in the udder. This is often, but not always associated with an intra-mammary infection. The inflammation often lingers for days after the cause of the infection is cleared. Think of it like a sore throat: It may be caused by Strep, but often your throat can be sore and scratchy even after the antibiotics have cleared the Strep bacteria
- SCC is made up of cells from the cow secreted in the milk. Healthy cows without mastitis may still have a low SCC. The largest contributors to the SCC are white blood cells (WBC’s). Healthy cows have some WBC’s, which help prevent infections when exposure occurs. It is not unusual for cows or herds with an extremely low SCC to have cows that get very sick and even die when a mastitis “bug” is introduced into the herd because they have such low SCC/local immune defense. Bacteria cells, when present, actually make up a very small amount of the SCC, but the immune response that the bacteria causes should cause the SCC to spike. A SCC of less than 200,000 is considered normal, and cows with mastitis may spike to over 10 million! In addition to indicating an infection, high SCC is undesirable in the industry because it alters the milk components (fat, protein, sugar) and shortens the shelf life.
- Infectious causes of mastitis vary, but the most common causes are environmental bacteria that gain entrance to the udder and create an infection. Various species of Staph, Strep, and E. coli are among the most common. Less commonly, largely due to improvements in management practices, are contagious bacteria which can spread from cow-to-cow through milking equipment. Non-bacterial causes of mastitis include species of yeasts and algae. Many causes of mastitis do not respond to treatment with antibiotics.
- Economic losses due to mastitis are difficult to comprehend. It is widely thought that the largest economic loss is due to increased culling and decreased milk production, both of which are multi-factorial on dairy farms. A cow may have a mild case of mastitis that affects her production and reproduction. Months later, she may be culled with “low production” listed as the reason, even though mastitis was the primary cause. Treatment expenses, discarded milk, veterinary costs, and deaths are more easily attributed to costs because they are clearly defined. In general, most studies across the nation suggest that the average cost of mastitis to a dairy is between $150 – 200 per cow per year! This is a very important consideration when looking at options to reduce mastitis on a farm, such as improved equipment and stall/bedding maintenance, surveillance of mastitis causes, and teat disinfectants.
Weather is a big factor for several reasons:
- Extreme cold/wind dries out teat skin, making it easier to form new cracks/chaps, and impairs healing of teat ends. Fresh cows/heifers may begin their lactation with damaged teats if weather extremes cause frostbite or skin cracking, and teat condition often worsens during lactation
- When it warms up after a cold spell, most barns don’t allow for the heat to escape which leads to increased humidity in the barns, and wet bedding. It is very common for condensation on roofs to cause water to drip into stalls
- During periods of extreme cold, many traditional barns are unable to scrape alleys and groom stalls properly. In an attempt to use less water and create less ice, return alleys often have increased build-up of manure. Buildup around drainage grates can cause slurry to pool in areas where cows often walk to/from the parlor, increasing exposure to environmental bacteria
- For farms using sand for bedding, washed sand rarely gets dry enough to be handled without forming big clumps. If cows do break these down with their body heat, these clumps release their moisture and make the sand in the stalls wetter. The clumps affect cow comfort, which can cause cows to stand more and lie less, which stresses cows and affects intakes, ultimately lowering the immune functions
- The difference between the temperature of the bedding and the temperature of the cow creates a micro-environment of moisture where there is contact, making the bedding wet and causes bedding to stick to the cow and decreases the natural friction/cleaning properties of most bedding types
What can we do to decrease the effects of cold weather? Improved alley/bedding/stall management and a more thorough procedure in the parlor will increase cleanliness. Close observation of the cows and teats to see if adjustments to the equipment are needed. Winter teat dips, with extra skin conditioners and/or stronger germicidal properties are also available. Bedding dry cows and heifers adequately and providing wind-breaks if they are housed outside will help the teat skin of fresh cows to be as healthy as possible. Making sure that the bedding is dry and that there are no drafts in return alleys and along curtains should keep weather damage to teats to a minimum in the milking herd.
