Milking routine 1: Stimulation and teat preparation
The secretion of milk depends exclusively on pituitary hormones. Milk is synthesised from components that reach the mammary gland through the bloodstream and accumulates in the alveoli.
Milk ejection is an active function that responds to both hormonal and nervous stimuli. After a mechanical stimulus (calf or milking machine), oxytocin is released and myoepithelial cells contract, thus leading to milk ejection. For this process to take place, it is essential that the animal is calm, without any signs of stress. Adrenaline, a stress hormone, is a strong oxytocin antagonist and so stops the milk let down. Stressful situations such as the ones listed below are detrimental for farmer (less milk harvested), cow (teats longer exposed to vacuum) and milker (milking shifts last longer).
- Uncomfortable conditions in the waiting area (steep slopes or too much time spent in the area).
- Harsh treatment to the animals while entering the milking parlour.
- Poor use of electric prods.
- Erratic voltage (static current in the milking parlour essentially due to a deficient earth wire).
In order for a cow to be milked, her teats should be clean, dry and well stimulated. The person in charge of the milking process should wear disposable gloves in order not to contribute to increasing the bacterial load with a bare hand. Human beings are an important reservoir of microorganisms that cause mastitis, as pathogens such as S. aureus or S. agalactiae accumulate in the creases of our skin (the latter can survive on our hands for more than 10 days). There is no such thing as a sterile teat; a good milking preparation is therefore necessary and will be more succesful if cow enters the parlour already with visually clean udder and teats.
The teats can first be cleaned and stimulated without using any product. This involves discarding the first streams of milk (stripping) and then cleaning the teats with individual towels. dried up dirt can be removed with a wet towel, by rubbing towards the tip of the teat. Direct application of water from a hose should be avoided, as it will also reach the rest of the udder or other parts of the cow, increasing the likelihood of bacterial contamination from these (dirty) areas.
It is recommended to apply a disinfectant, provided the teats are clean (desinfecting dirt is quite inefficient). It acts rapidly (25-30 seconds) and can be applied by means of a spray or using a cup, always ensuring the whole surface of the teat is covered. In general, pre-dips are used to prevent both contagious and environmental mastitis. Once the predip is applied, the first streams of milk are discarded. It is recommended to strip the milk into a dark container so that abnormalities in the milk can be easily detected. With this practice, called "stripping", it is possible to:
- Evaluate a possible case of mastitis.
- Discard the first streams of milk (higher load of bacteria and higher cell count)
- Stimulate the teats to induce oxytocin release.
After removal of the disinfectant from the whole surface of the teat and sphincter, the skin – particularly that of the teat sphincter – is dried with individual paper towels.
The milking cluster should be placed in the 90 seconds after stimulation. A lack of stimulation will cause trauma at the tip of the teat, since it will be longer exposed to hihger levels of vacuum.
Most common disinfectants
- Iodophors: These are usually formulated at 0.25-1 % and with a pH of 4.5. They give good results against staphylococci, coliform bacteria, spores, fungi and some species of streptococci. Their antimicrobial action is based on oxidation, so the free iodine concentration, responsible for the oxidising action, should be taken into account.
- PVP (polyvinylpyrrolidone): 2,500-5,000 ppm. Pure or diluted.
- Chlorhexidine: gluconate or digluconate, at 0.35-0.55 %. It is also used against coliform and contagious bacteria and esculin-positive streptococci. Its action involves precipitation of the cytoplasm, proteins and macromolecules. It has traditionally been characterised as easy to contaminate by pathogens such as Serratia and species of Pseudomonas.
- Dodecylbenzenesulfonic acid (DDBSA): against S. uberis. Its action involves the denaturation of proteins in the microbial cells, the inactivation of enzymatic systems and the destruction of cell membranes.
- Chlorine derivatives: sodium hypochlorite, sodium dichloroisocyanurate and acidified sodium chlorite. These components must be used rapidly once they are reconstituted due to their short shelf-life.