Breeding mastitis-resistant cows
Selecting for disease- resistant cows has become a reality for farmers around the globe as genetic developments continue to advance.
Mastitis in dairy cows is an infectious condition as a result of pathogens entering the udder through the teat canal.
Depending on the bacteria involved, the infection may be contagious and affect other cows in the herd as a result of transfer from cow to cow by milk contamination during the milking process.
Please listen to Dr Pamela Ruegg’s Global Dairy Expo 2020 presentation or read her papers on mastitis online to help with an understanding of the condition we refer to as mastitis. Ruegg refers to contagious bacteria Staphylococcus aureus and Streptococcus agalactiae and also to the especially nasty form of mastitis that they experience with Mycoplasma bovis.
Staphylococcus aureus would be the most common of the contagious bacteria we see easily transferred from cow to cow as a result of an infected cow being milked and passing the bacteria onto the next 5-6 cows using the milk contaminated cluster.
Many dairy farmers now wear gloves during milking to help prevent this bacterial contamination from occurring. It is a clever bacteria that lives deep and high in the udder and results in infectious downloads from time-to-time – sometimes only lasting a few hours. It can be hard to find as it doesn’t always create a hard swollen quarter and may be intermittent in a cow. Treatment drugs do not reliably deal to this infection and cows, especially older ones, often have to be culled.
Other mastitis causing bacteria, such as Strep. uberis and E. coli are more an environmental problem due to dirty exit areas and laneways and muddy paddocks and may be coupled with an ineffective teatspray. It is fair to say that a stressed, hard-working cow will be most vulnerable to udder pathogens especially if her immune system is down due to calving or mating.
We now milk our persistently high somatic cell count (SCC) and newly recovered from mastitis cows last to prevent cross infection. This works well and is simple to manage and we now record an average annual SCC levels at 100,000 and below.
Cows at herd test (we do four tests per year) with less than 200,000 SCC levels are considered cured and, depending on their history, may go into the main herd.
We milk our 550 cows in a rotary shed so when we need to strip the herd due to some mastitis showing up on our filter socks, a second person comes into cups on to do this. That person will wear gloves and use an approved “Ready to Use” (RTU) teat spray, (that has been shown to kill bugs quickly) on our hand. While it’s ideal to hand strip a herd using one’s finger and thumb, when you’ve done 500 cows your hand gets tired and some milk contamination will occur. Many of us have seen new cases of mastitis occur after hand stripping due to bug transfer. The RTU on a gloved hand reliably prevents this from happening.
Our newly calved (most vulnerable) cows are thoroughly teat sprayed and checked before cupping with teat sprayed clusters OAD to prevent cross infection from the main herd. They are milked before the colostrums, resulting in a bulk SCC during spring of 60,000 to 80,000. They don’t enter the main milking herd until they’re clear on a paddle test using RMT solution.
I use a Farm Medix Check-up kit to identify the bacterial challenge a cow has.
