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Mastitis Case Studies

Milking Process


The milk process requires several important steps. The purpose of these steps is to elicit optimal milk letdown, minimize the chances of a cow contacting mastitis organisms during milking, and efficient milk removal.

1. Milker preparation: The hands of a person milking cows can become contaminated with mastitis-causing pathogens, either from handling dirty equipment or from contact with contaminated milk from infected cows. Some microorganisms prefer living and growing on skin, whether it is the cow’s teat skin of the milker’s hands. Today, most milking operations will have the milkers wear disposable latex gloves. These are replaced periodically through the milking process.

Milker wearing latex gloves.
Milker wearing latex gloves while milking cows.

2. Clean the teats: The teats are prepared by thoroughly cleaning the teat and teat-ends with some solution that removes dirt and provides some sanitation to the teat skin. Many people now use a pre-milking germicide dip solution (for example at the UIUC farm they use a 1% iodine solution) called a per-dip. This wets the teat, provides sufficient moisture to wipe off the teat and get it clean, and sanitizes the teat skin. The act of massaging the teats while wiping them off also is stimulating the oxytocin release that will cause milk ejection.

It is important to avoid getting the udder wet. Use of spray hoses (drop hoses) to spray germicide onto the teats can get the udder hair wet, where the contaminated fluid then can drain down the teat to the teat end even after wiping off the teat. Long udder hair is not desirable and it is usual for many dairy producers to remove the hair from the udder, especially during winter months. This is done by clipping udders or by singeing the hair with a flame. If done properly, the latter method is very effective with no effect on the cow.

Drop hose.
Drop hoses (red arrow) are convenient to spray teats. Also can get the udder hair wet.
Dirty udder.
Dirty teats.
Predipping teats.
Dirty udder and teats. Removing long hair from the udder can help keep it cleaner.
Dirty udder and teats.
Pre-dipping teats with iodine-based germicide.

3. Dry the teats: Use a separate dry towel (usually paper or cloth) to wipe-off and dry the teats thoroughly. It is particularly important to get the entire teat and tip of the teat clean. When a pre-dip is used, wiping off the teat will remove most of the iodine solution resulting in negligible contamination of milk with the iodine. Typically milkers will dip teats on several cows and then return to the first cow, wipe off the teat and go to step three. The use of sponges is discouraged. Sponges can harbor mastitis-causing pathogens, even when soaked in germicide. Use of individual towels so that each cow is separately dried is highly recommended. Reuse of a towel from one cow to the next can spread mastitis-causing pathogens from cow-to-cow.

Drying teats with a individual paper towel.
Paper towel dispenser.
Drying teats with a dry individual paper towel.
Paper towel dispenser.

4. Foremilk stripping: Several squirts of milk are removed from each quarter. This is done into a strip cup, where the white flakes or clots in the milk will be collected and show up against the black screen of the strip cup top. Alternatively, milk is stripped onto the floor under the cow and observed for flakes or clots. The latter approach is most commonly used, although using the strip cup is the preferred means of identifying flakes or clots. Cows with flakes or clots in their milk probably have some form of mastitis. This is the most common means of identifying clinical mastitis. Typically, the milk that was furthest down in the gland at the start of milking, that is closest to the teat end, is high in somatic cells. Eliminating this by stripping results in lowered overall somatic cells in the milk that is harvested.

Strip cup.
Strip cup with milk.
Flake in milk.
Predipping teats.
Examples of milk flakes and clots. Right-hand image, taken in a CMT paddle - has a few flakes (red arrows). Left hand image, taken on the lid of a metal strip cup - has many clots and serous milk from a cow with acute mastitis.

5. Application of the machine: The milking machine should be applied within one minute of the initial wiping of the teats to take maximum advantage of the milk letdown response. The milker holds the claw in hand, the vacuum is turned on and four teat cups are applied as efficiently as possible, with minimal sucking of air when teat cups are turn up to place on the teat ends. Milk should start flowing immediately. Adjust the machine so that it hangs straight down from the cow. Teat cups that ride-up excessively high on a teat should be adjusted. This situation can potentially cause irritation to the teat lining.

Applying teatcups.
Checking teat cup placement.
Applying teatcups.
Checking teat cup placement.
Machine hanging properly from udder.
Machine hanging improperly from udder.
Machine hanging properly from udder. Rear entry milking in a parallel parlor.
Improper position of machine. Side entry milking in a herringbone parlor.

6. Machine-on time: Maximal intramammary pressure caused by milk letdown occurs at about one minute after udder preparation begins and continues for about 5 minutes. Shortly after that the milk flow will drop to a point where the automatic take-offs will detach the milking machine. Most cows will milk out in 5 to 7 minutes.

Some cows are slow to milk out. This may occur because they produce more milk than can be removed in 5 minutes, even with maximal removal efficiency. Or, cows may have structural problems with the teat end or inside the udder that makes them milk out slowly. In the latter case, because the machine is on the cow repeatedly for long periods, the cows may be expose to more chances of contacting mastitis-causing pathogens.

Milk flowing in the claw.
If milk letdown has been properly sti,ulated, then milk will start flowing freely in the claw shortly after applying the machine.

7. Detaching the machine at the end of milking: The vacuum must be turned off before the machine is removed. Otherwise, pulling on the teat cups while the vacuum is still on may cause trauma to the teat ends, weakening the sphincter muscles that keep the streak canal closed. Normally it takes about one hour after milking for the streak canal to re-close. Any teat end trauma may compromise the ability the sphincter muscles to close the canal and prolong the exposure of the teat end to mastitis-causing pathogens post-milking. Most people milking cows tend to over-milk the udder. In an effort to remove all of the milk, they will physically push down on the claw or pull down on one or more teat cups. This is called machine stripping, and while it does result in removal of more milk from the quarters, it also results in overmilking and more stress on the gland. The purpose of the automatic take-off (ATO) is to prevent this overmilking. The milking system detects flow rate of milk coming from the gland. When that flow rate drops to a specified level, the vacuum is turned off and a mechanical arm or chain retracts and pulls the machine from the cow’s udder.

Overmilking by machine stripping.
Machine stripping by holding down on one teatcup.

8. Post-milking teat germicide dipping: As indicated above in #5, the streak canal stays open for about an hour after milking. If a cow’s teat then comes in contact with mastitis-causing pathogens, they may easily enter the teat and cause an infection. One of the most effective means of controlling mastitis is post-milking teat dipping with a germicide. This protects the teat end for a period after milking, kills pathogens that may be on the teat skin, and minimizes the potential passage of those pathogens from one cow to the other at the next milking. Post-milking teat dipping can reduce new infections by 50%. However, teat dipping must be done routinely at each milking. Only doing dipping teats for selective periods of time is not effective.

Dipper for teat dip germicide.
Dipper for teat dip germicide.
Dipping teats at the end of milking.
Teats after post-milking dip.
Dipping teats with iodine-based germicide at the end of milking.
Teats after post-milking dip with iodine-based germicide. Note drop of dip remains hanging on the end of the teat.

9. Post-milking cow management: Because the streak canal stays open for about an hour after milking, often producers will make feed (often hay or silage) available to the cows after they are done milking. Cows will remain standing while eating. This reduces the chances of the cow lying in manure that may contaminate the teat end before streak canal closure.

Cow lying in stancheon stall.
Cow lying in stancheon stall.
Cows eating.
Cows eating at bunker feeder.
Cows eating in free-stall lot.
Cows eating at bunker feeder.

Teat health has been mentioned at several points above, whether in combination with proper vacuum level and pulsation rate and ratio or teat dipping. Anything that compromises the health of the teat end potentially weakens the ability of the sphincter muscles to properly close the streak canal or the ability of the keratin lining to seal off the canal. Chapped teats during winter, teats that are traumatized by being stepped on or from improper milking machine function, cows being suckled by other cows, improper or repeated insertion of teat cannulas for intramammary infusion of antibiotics or other intramammary treatments or for draining milk from teats that are damaged, all may compromise the health of the teat end.


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