There are two broad elements to the risk of an individual quarter developing a mastitis infection. 

The first element of risk is simply a numbers game – the more bacteria near the teat end, the greater the chance of an infection.

The second part of the risk is the ability of the teat to resist bacteria entering and causing an infection.

Obviously, after wet weather, there is often an increased amount of water, mud and faecal material contaminating teats. Not only will this dramatically increase the number of environmental bacteria on the teat skin, but it also has an effect on the number of other mastitis-causing bacteria on the teat skin and near the teat end.

Healthy teat skin is coated with a protective mantle of fatty acids that slows the growth of bacterial pathogens.  In cold, wet and windy conditions, this coating and its protective effect can be quickly lost.

Furthermore the skin of machine-milked teats can become scaly, irritated or chapped, and coupled with the loss of the protective surface coating this allows growth of bacteria such as Staph aureus.

Cold, wet or muddy conditions also induce hardening or thickening of teat skin. Mud, as it dries, draws moisture from the skin with a consequent loss of elasticity of the teat skin. Under these conditions, small skin cracks, barely visible to the naked eye, begin to develop, and can quickly become bigger cracks when the teat skin is stretched and squeezed repeatedly by machine milking. Even small skin cracks further enhance the growth and survival of mastitis-causing bacteria.

So weather conditions can dramatically affect both risk factors for infection (the number of bacteria on the teat skin, and also the natural defences of the teat), thus increasing the chance of a mastitis infection. And infection can be due to either environmental or common cow-associated mastitis bacteria.

Fortunately, there are strategies that we can put in place to reduce those risks.

Words
320