Cow grouping

Dairy cows are usually grouped, particularly when housed, according to the nutritional requirements and the stage of lactation of the individual cow.

However, it is also important to recognise that cow grouping and more importantly the order in which the cows are milked can contribute to an effective contagious mastitis control strategy, by milking the more susceptible animals first and leaving those most likely to carry subclinical disease until later. This means that any pathogens or contagious materials are less likely to be passed from cow to cow via the milkers and/or the milking equipment until the plant is washed at the end of milking.

Ideally, cattle should be milked in the following order:

  • Freshly-calved cows and heifers first, which due to a repressed immune system post-birth, are at the highest susceptibility to mastitis.
  • Highest yielding cows, being particularly susceptible to mastitis and having least exposure to illness.
  • Mid-yielding cows, which may pose a greater risk from being exposed to pathogens and subclinical carriers for longer.
  • Low-yielding cows, which will tend to be later lactation animals and will have had the longest exposure to mastitis-causing pathogens and therefore will likely have the highest levels of subclinical disease in the herd.
  • Cows with particularly high Somatic Cell Counts, which will present a reservoir of infection for the other herd members.
  • Cows with clinical symptoms of mastitis and those being treated for the disease.

It will also be more effective, and easier due to their being handled as a group, to put in place increased disinfection measures between individual cows in the last two groups, such as cluster unit dipping or flushing after every cow.

Furthermore, by housing cows with clinical mastitis and subclinical mastitis/high SCCs as two separate groups away from the rest of the herd, there will be a greatly reduced risk of cross-contaminating the more susceptible but uninfected cows.