Teat spraying is probably still the most important single thing you can do to reduce the spread of mastitis. The reason for this is that every time you apply cups to a cow you are passing bacteria to the teats of the next cow to be milked. These bacteria then can enter the teat canal and cause mastitis.
The most effective way to stop this form of transfer is with an effective teat spray. Trials in NZ and overseas consistently show a 50% reduction in cell counts and clinical mastitis with the use of teat spray or teat dip. In a survey of 200 mastitis problems (IDF 2010 conference) only 30% of the teats were adequately covered with teat spray and only 30% of farmers were using the correct dilution rate. The end result was that only 12% of farmers had both the teat spray coverage and dilution right.
The second most important factor is teat condition. All the bacteria that cause mastitis have to enter through the teat canal. Having a normal intact teat end is the best defence against entry of mastitis bacteria. The teat skin should be smooth and supple and the teat canal should just be visible as a pin point hole about 1mm in diameter. The first stage of teat damage is an open teat canal about 2 to 3 mm diameter that you can put a match stick through. The next stage is a rough teat canal where the end of the teat canal is protruding and is no longer smooth.
The very rough stage is where the teat skin is broken and this may progress to the black pock or black spot type of lesion where there is loss of teat skin tissue. The teat skin should be supple as dry skin will predispose the teat to cracks and teat end damage. Teat damage allows bacteria to enter the teat canal easier during milking and also because the teat canal never closes it makes the cow more susceptible to picking up bacteria from the environment. There are many causes of teat end damage-incorrect vacuum level, faulty pulsation or incorrect pulsation settings, liner type and over-milking. Often teat damage results from a combination of these factors.
The third key cause of mastitis is impacts that occur after cup slips. When a cup slips air rushes in and blasts any bacteria in the cluster up against and into the teat canals of the attached cups thereby spreading bacteria during milking. There are many causes of cup slip-poor cluster alignment, unsuitable liners, poor vacuum reserve are the common ones.
The fourth mechanism is poor milk-out of cows. Leaving milk behind through poor milk-out means more bacteria are left in the udder which will multiple and increase the risk for clinical mastitis. There are many causes of poor milk out and the most common ones are uncomfortable cows and teat damage.
The above issues are best assessed during milking as it is important to observe the normal milking process and to do “wet” testing of the milking machine to assess its impact on cows during milking.