The inside of a healthy udder is free of bacteria. The teat canal closes in between milking times and also when the cow is dry. It acts as a seal that protects the inside of the udder from the outside. Mastitis bacteria invade the udder almost always through the teat canal. In a few cases bacteria can also enter the udder tissue directly from infected wounds and from the blood when the cow has fever. Wrong hand milking (forced stripping) or incorrect machine milking (faulty teat cups, fluctuating vacuum) cause injury to the teats every time an animal is milked. This progressive weakening of the teat tissue reaches a point where the teat canal can no longer close completely. It loses its role as a barrier to protect the udder against outside bacteria in between milking times.
-> In consequence, in most cattle that had more than six calvings the udder is very susceptible to mastitis.
Factors that contribute to poor udder health and more frequent Mastitis in dairy cattle:
• Dirty stable and bedding – high contamination of the cows environment with mastitis bacteria
• Dirty milking shed / milking parlour – high contamination of the milking area with mastitis bacteria
• Milking with dirty hands, teats not cleaned before milking, dirty udder cloth used for washing
• Faulty machine milking - dirty teat cups, dirty milk pipes, fluctuating vacuum (machine not serviced)
• Dirty udder skin harbours more bacteria, more bacteria on the skin of the udder means more mastitis
• Purulent wounds of the udder skin and teats (such wounds can be caused by injury, insects and ticks)
• Untreated purulent infections of the feet and hooves - pus bacteria cause mastitis
• Oversized teats - teat canal does not close properly between milking times, prone to mastitis
• Low hanging udders and very long teats are more exposed to dirt and very prone to injury
• Cattle with chronic mastitis that act as permanent source of infection for other animals in the herd
• Heifers suckling each others teats before calving
• Use of under-strength and contaminated teat dip
• Mouldy feed (contains fungal toxins)
• Acute infections with high fever and bacteria or viruses in the blood of the cow
• A lot of flies in stables, milking area and on pasture
-> Avoiding these factors will significantly reduce the occurrence of mastitis.
Bacteria that have succeeded in entering the udder through the teat canal can be cleared by the defensive response of the udder or persist inside the gland. If they persist they start multiplying rapidly inside the milk gland and cause mastitis. The mastitis bacteria can survive inside the udder for weeks, for months or sometimes even for life.
Healthy Teats & healthy udder skin -> less mastitis
The number of bacteria on the teat skin determines how many bacteria can reach and enter the teat canal in between milking times.
- If more bacteria are present on the teat skin -> more of them can enter the teat canal.
- If more bacteria enter the teat canal -> more of them move through the canal and reach the milk gland tissue inside the udder.
- If more bacteria reach the gland tissue -> it is more difficult for the udder defence to eliminate them completely.
- If bacteria survive and start multiplying inside the gland -> the cow suffers from mastitis.
Therefore, the cleanliness of the teat skin (or in other words: the number of bacteria on the teat skin) determines whether a cow catches mastitis!
The density of bacteria on the tea surface depends on the health of the teat skin.
- If the teat skin is dry and has small wounds and cracks the bacteria multiply inside these small wounds and cracks and become more. Using milking fat regularly keeps the teat skin elastic and healthy with by far less bacteria on its surface.
- If the teat skin is affected by Foot-and-Mouth-Disease (FMD) or other infections with fever that also produce lesions on the teats (e.g. pseudo-Cowpox, Herpes virus) an anti-septic ointment must be applied after each milking until lesions have healed completely. During infections like FMD the risk of a cow suffering from mastitis increases; it’s important to observe maximum cleanliness at milking.
- In cows with low hanging udders and oversized very long teats the cow can accidentally step on the teats causing injury. This can either damage the teat beyond repair or cause wounds that constantly harbour lots of bacteria. - Providing cows that have low hanging udders and/or oversized teats with an udder support (the “udder bra”, made of nylon mesh) reduces risk of teat injury. Breeding for compact udders with normal sized teats reduces mastitis risk.
- If the teats are too short it also takes a shorter distance for bacteria to reach the inside of the milk gland -> higher risk of mastitis.
- Warts on the teats are harmless and should only be removed if they really interfere with milking.
- Udder acne are small pustules with pus appearing on the skin of the udder and teats; keeping the hair in the affected area very short and washing the udder skin thoroughly each day with antiseptic soap will solve the problem.
- Ticks must be immediately removed from the teats and udder, tick bites harbour dangerous bacteria.
- Udder Sores are moist foul-smelling skin lesions that appear in areas where the udder is pressed tightly against the thigh (= udder skin permanently pressed against inner skin of the legs) – this can also happen when the udder has an oedema (see dry period); the affected skin should be washed daily with an antiseptic solution and thoroughly dried.
What to observe at milking in order to maintain good udder health
The udder, and in particular the teats of the udder, must be clean before milking. Although widely practised, washing the whole udder immediately before milking is not a good method. The water that runs down from a freshly washed wet udder reaches the teat and carries dirt and bacteria towards the teat opening and onto the milkers’ hands during milking. If udders are very dirty they must be washed and dried in good time before milking starts. Udders must be dry when milking begins. Udders that are dry and reasonably clean do not need washing at every milking time. It is good practice to only clean the teats immediately before milking. The safest way to clean the teats is to use dry tissue paper, one fresh piece of paper for each teat. (For example one piece of tissue paper can be torn off a fresh roll of toilet paper that is used only for milking; this is not expensive.) Udder cloths are frequently used for cleaning the teats and the udder. Very often these cloths get contaminated and carry bacteria from one cow to the next. If udder cloths are used each cow must have her own cloth; the cloths must be washed in hot water and ironed or dried in between every milking time (this is often not practical -> easier to use tissue paper).
–> In short: Keeping udders generally in clean condition is easier and safer than washing them before every milking. Teats must be dry-cleaned immediately before each milking.
These first streaks of milk should always be milked onto a strip cup (with dark surface) and examined for abnormal colour, watery consistence and presence of flakes or lumps. If any abnormal signs are present in the milk, such a cow is likely to suffer from mastitis and should be milked last. If the cow cannot be milked last the milkers’ hands and the milking bucket must be thoroughly washed with antiseptic soap before milking the next cow.
After milking the teat canal is still open and the mastitis bacteria on the teat skin are trying to move into the teat canal as soon as the milk flow stops. To prevent this it is important to apply disinfectant teat dip (containing iodine). Immediately after milking each teat is briefly dipped into a dip cup containing the teat dip fluid - this kills off all bacteria on the tip of the teat near the teat opening. Teat dip fluid must always be fresh and clean. Only a very small volume is needed to dip a cow at each milking. Discard any leftovers and squeeze the bottle below to fill the cup with fresh dip fluid. Old contaminated teat dip can transmit bacteria from one cow to the next.
Cattle with diarrhoea shed more dangerous bacteria in their faeces than cattle with normal dung. These dangerous bacteria are then very numerous on the bedding, in the milking parlour and on the teat skin of the cow and can easily enter the teat canal and cause acute mastitis. Feeding cows enough good hay to avoid diarrhoea reduces the risk of dangerous mastitis.
Also, if cows are treated rough before and during milking they will pass faeces more frequently at milking time because they are afraid. More defecation means more bacteria near and on the teat and again a higher risk of mastitis. Handling cows gently before and during milking reduces the risk of mastitis. Feeding dairy meal during milking also makes the cow relax and defecate less often.
The milking parlour or location where milking takes place and the milking equipment, must be kept as clean as possible. Milking buckets must be washed with hot water and antiseptic detergent after every milking time and kept in inverted position to dry before the next milking. Faeces contain bacteria that can cause mastitis. Bacteria also survive and multiply in standing water (puddles on the floor) or inside not well cleaned milking buckets. Flies move around, including on the ground and on dung. When they land on the teats to sip some drops of milk they leave behind dangerous bacteria on the teat skin. These bacteria then enter the udder and cause mastitis.
Some bacteria that can also cause mastitis are shared between humans and cattle. The person(s) carrying out the milking must wear clean clothes and gum boots, be in good health (no fever, not coughing or sneezing, no infected skin wounds), wash their hands thoroughly before milking and refrain from eating, drinking or smoking during milking.
In between milking times some bacteria will always manage to enter the teat canal. They are flushed out with the first streaks of milk when the milking begins (these are the very same streaks of milk that are normally being checked in the Strip Cup). It is important to discard these first streaks of milk and NOT include them in the milking bucket -> this leads to cleaner milk with less bacteria and which keeps fresh for longer and fetches a better price. Milk with mastitis bacteria in it spoils much more rapidly, fetches lower prices or cannot be sold at all. Mixing mastitis milk with clean milk in the same container leads to contamination and spoilage of all the milk. (Rather than milking the first streaks onto the floor collect them into the Strip Cup.)
The Dry Cow Period
The first two weeks after a cow has been dried off can be a critical period for the health of the udder, especially if it has already been infected by bacteria during the lactation. After these two weeks the dry udder is generally resistant to new bacterial infections until the next lactation. The dry period should not be too long or too short, 6-8 weeks is recommended. When the cow gives birth, for about two weeks starting just before calving, the udder defence is low and the risk of mastitis is again very high (see Coli mastitis).
Before the cow gives birth she develops an oedema on the lower side of her body that also affects the udder. The oedema swelling can be differentiated from the swelling caused by acute mastitis by the following signs:
- The swelling does not feel hot
- The swelling is not painful
- The swelling is soft and has a dough-like consistence, when pressing it with a finger the created depression persists for a while
This swelling is normal and disappears soon after birth, although it may sometimes persist for a while. It may interfere with milking when it is very strong. There is no treatment to reduce it faster.