The previous article was about the management strategy concerning mastitis. This article gives an insight into the natural defence mechanisms at udder level and how to support these.
Cow health, Milking
Teat skin is the first line of defence against invading pathogens. The surface of the teat skin consists of dead cells filled with keratin. In addition, there are fatty acids present on the skin that are bacteriostatic. When intact, this provides a hostile environment for bacteria, thus preventing their growth. This bacteriostatic property can be removed and this is why teat sanitiser should be chosen carefully. The normally intact surface of the skin may also become compromised by cuts, cracks, chaps, bruising, lesions, etc. Bacteria can then multiply on the surface of the skin and become a reservoir for mastitis infections. This is particularly the case for organisms such as Streptococcus dysgalactiae and Staphylococcus aureus. Therefore, every udder care product from Lely consists of disinfection and care components to reduce the infection pressure (figure 2). Besides this, trials have shown that cows with dry and badly cracked teat skin are much slower milkers. They may need double the time on the unit to achieve the same level of yield, and of course, this increased time can lead to teat-end damage.
The teat canal is located between the teat cistern and the outside ending of the teat. It is lined with a skin-like epidermis that forms the keratin material that has antibacterial properties. At the level of the teat canal, the circular muscle is well developed, forming the teat sphincter, the function of which is to retain milk in the intervals between milking. It takes at least 20 minutes to 30 minutes for the teat to become fully closed. Hence, in order to protect the teat from bacterial contamination, the advice is given that animals should not be allowed to lie down for at least 30 minutes after milking. In robotic milking systems, in which this behaviour is hard to control, a barrier spray can give a good outcome. Although, in particular, cows prefer to drink after milking and during feeding. This behaviour is clearly seen in herds, where cows will go to drink after visiting the robot. Therefore, ensure an adequate and clean water supply.
Many bacteria entering the teat between milkings become trapped by the layer of keratin and lipid lining in the teat canal. They are then flushed out at the start of the next milking by the first flow of milk, as this removes the superficial layers of keratin lining the teat canal. This is known as ‘the keratin flush’. It is very important to ensure that udder preparation and unit attachment are such that milk flows out of the teat when the cluster is applied, and that there are no reverse flow mechanisms that might lead to milk and infection being propelled back up into the udder. This is why cows with short teat canals (short vertical length) and those with a wide cross-section diameter are more susceptible to mastitis. Therefore, Lely provides a portfolio of different teat liners to match these teat sizes and farmers’ needs.
Teat-end scoring is nowadays a commonly pursued parameter in research. In the field, teat condition has been accepted as an indicator for quality of milking. Different settings of the milking machine, such as vacuum level, flow rate at cluster removal and pulsation rate, including previously mentioned causes, affect teat tissue. Changes can be observed such as teat swelling, teat flattening, colour changes, openness of the teat orifice, loss of keratin, vascular damage (haemorrhages), and teat-end callosity. Research has found that teat ends with severe erosions that were raw and ulcerated (broken skin) showed a higher prevalence of mastitis (Farnsworth, 1995).
Microscopic view of a teat end with a smooth and thin callosity ring and the corresponding view of the outside (De Man, 1998).
Microscopic view of a teat end with a severe rough callosity ring and the corresponding view of the outside (De Man, 1998).
Tight closure of the teat canal is not possible, thus enabling pathogens to enter the udder.
This image shows poor teat skin condition and poor teat-end condition. Poor teat skin can be caused by environmental factors, such as cold, wet or muddy conditions, or lime bedding material drawing moisture from the skin. Another possible issue is irritation by the disinfecting ingredient in the absence of sufficient emollients.
Poor teat-end condition can be caused by poor milking performance, such as the wrong milking settings, overmilking or poor teat liner fit.
The teat-end condition is a very important defence against invading pathogens. Optimising skin condition is a preventive and effective way to limit cases of mastitis. In the next article, we will delve deeper into the cow-related and environmental pathogens that cause mastitis.
