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Mammary Glands

Teat Ends -- Critical Control Point
By Winston Ingalls, Ph.D.
Aug 2, 2003, 3:13pm

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Teat Ends -- Critical Control Point 
In Mastitis Control

by Winston Ingalls, Ph.D.
West Agro, Inc., Kansas City, MO

Dairy farms have many issues requiring attention but four key locations are more critical than others. They are the right front, left front, right rear and left rear teat ends of every cow and heifer on the dairy.  Doing things correctly at these four locations produces many benefits. Failure to manage these areas properly frequently leads to problems that can be very costly.

The teat end is where the critical action takes place on a dairy farm. Maybe that sounds too simple or exaggerated but think about it. A dairy farm derives its income almost totally from the sale of milk and whatever milk is harvested has to pass through this zone. Also, any bacteria that enter the udder and cause mastitis have to pass through here as well. It therefore stands to reason that this a critical control point both in terms of milk harvesting and udder health.

Heifer Mastitis
The effort to manage this area must start early in the life of dairy animals. While this may be surprising, there is plenty of evidence indicating mastitis problems can develop well before lactation even starts in the first calf heifer. What are the issues?

Heifers are known to develop udder infections before and around the time of calving. Exactly when is unclear but it appears some may occur in the immature gland of young heifers. The bacterial species involved in heifer mastitis include Staphylococcus aureus, which is present at various levels on many dairies and is often considered a problem in older, chronically infected cows.

We discuss Staph aureus extensively but this organism also has a lot of relatives, other Staph species, frequently referred to as coagulase-negative Staph (CNS), that can create difficulties. We are now recognizing that heifers are susceptible to new mammary infections caused by the coagulase-negative Staph as well as Staph aureus. Staph species, are in fact the most common cause of udder infections in heifers and they can cause elevated somatic cells and problems prior to freshening.

How can a heifer that has not freshened and has never been milked develop mastitis? In at least some instances flies, especially biting flies, may be a factor in spreading mastitis-causing organisms from infected cows to heifers and other cows. Unfortunately they act like bees pollinating flowers. Wherever they go they have the potential to pickup and transfer disease organisms. Biting flies may also cause skin damage around the teat end providing additional opportunities for bacteria to colonize and live. Fly control is a necessary investment to help protect these four areas from intruders.

Bottom line-heifers frequently develop udder infections prior to calving. Losing a first calf heifer or having a heifer lose a quarter or develop a light quarter at this point in her productive life is a major loss because all the costs have been sunk with no return yet realized!

Antibiotic Treatment of Heifers Prior to Freshening
Several studies have evaluated the possible benefit of treating quarters of near-fresh heifers, approximately14 days before calving, with lactating cow antibiotic treatment tubes. This practice appears to reduce the incidence of clinical mastitis around calving and reduces the early culling of fresh heifers due to mastitis problems. Make sure to discuss with your veterinarian the precautions that must be considered because of the extra-label use of the antibiotic preparations and the risk of antibiotic residues in the milk. 

So the battle at the teat end starts early in the life of the dairy cow, well before the first calving.

Streak Canal -- Keratin
The teat end and streak canal is a transition zone. Skin on the exterior of the teat extends around and up into the teat end opening a short distance and there it is modified to form the lining of the streak canal. This modified skin continuously produces a waxy material, termed keratin, that lines the streak canal opening and provides several functions.

The keratin lining is thought to trap bacteria in the surface of this waxy material and stops their movement through the streak canal into the teat cistern. There are some bacteria species that appear capable of growing in the keratin but their movement through the streak canal is likely slowed down. When a cow is milked, the rapid flow of milk through the streak canal shears off some of the keratin buildup and with it goes some of the bacteria that may be stuck in the material. They are flushed out. The process of milking therefore removes some of the keratin at each milking and this appears to help limit bacterial entry into the udder. Between milkings keratin again is deposited in the streak canal.

Liner Action -- Teat end
The action of the liner on the teat end may prove to be a problem under certain conditions. Milk normally flows from inside the gland out through the teat opening into the liner. This is what occurs throughout the milking. If there is a liner slip, squawk or unit fall-off, a rapidly moving stream of air may enter and be directed at the teat end for a brief period. Milk droplets containing bacteria may be carried in this air stream and be projected against the teat end. It is this general mechanism of reverse directed impacts that is thought to explain in part how the milking unit may be involved in mastitis.

What causes it? Numerous things. Heifers and cows that have swollen udders, short teats and are sore and very nervous are tough to milk. As they move and kick they may cause liner slips or pull off the unit. Since their teats are often short and dilated the liner has a tough time staying put and liner slips are common. Uneven udders, three teated cows and poor unit alignment are additional factors that can increase liner slips etc with any cow.

For this reason, during milking time evaluations, always look carefully at how frequently this may be occurring. Proper milking system settings, machine positioning and milking procedures help minimize this concern at the teat end.

Role of Teat Dipping-Pre and Post Milking
Mastitis causing bacteria, such as Staph aureus, Strep ag and others that primarily live in and on the teat and udder, may be transferred on the liner surface to teats of the next cow milked. At the end of milking there is always a film of milk left on the teat capable of supporting bacteria growth. If these bacteria are not killed promptly they pose a risk. This is where teat dips play a key defensive role. Applying a quality teat dip, immediately after milking, should kill all surface bacteria leaving the teat well sanitized and at less risk to mastitis pathogens. Teat dipping is our primary tool to limit spread of contagious mastitis causing bacteria.

There is a somewhat similar problem prior to milking that involves different bacteria species. Any bedding, manure or dirt that sticks to the teat and teat-end carries with it large numbers of environmental bacteria such as the coliforms and environmental streptococci. Exposing the teat end to large numbers of these bacteria prior to milking increases the threat of environmental mastitis infections. Housing and teat preparation procedures that produce clean dry teats prior to milking are necessary to minimize this threat.

Liner Action on the Teat End
The action of the liner on the teat end during milking results in a teat that is stretched lengthwise and the muscles surrounding the teat end also become fatigued as the teat end is pulled open repeatedly. When the unit is removed the teat orifice remains partially open for some period after milking is complete. The gate is open!  Post milking teat dipping reduces the bacteria population on the teat and if cows can be kept standing for a period of time this also helps reduce the risk of a partially open teat orifice being plopped down into dirty, bacteria rich surroundings.

The integrity of the teat closure system is critical in helping keep bacteria from entering the udder and when damaged, problems follow. Cows experiencing injuries to the teat-end, such as deep cuts or stepped on teats that cause damage to the muscle band, generally will develop mastitis problems. Such cows unfortunately usually have to be culled because of these limitations.

The action of the liner on the teat itself can be a cause of teat end irritation and problems if the milking system settings are not proper or if there is excessive machine on-time when little or no milk is flowing.

Dry Cow Management
At dry off many of the issues are reversed. Milking no longer takes place twice daily so bacteria are not being flushed out of the system. It is helpful at this time to infuse quarters with an antibiotic tube to help clear existing infections and prevent new ones. It is known that the teat takes some time to close up after cows are dried off. The keratin development that is normally partially flushed out at each milking has to now build up and form a plug that limits bacterial entry. This takes time to fully develop. A management tool that can offer protection during this period is an external teat sealant. The sealant forms a temporary barrier around the teat end while the keratin plug is forming and helps keep bacteria from entering during this critical time.

Eventually the udder shuts down and becomes strongly resistant to new infections. As the time of calving approaches another period of vulnerability occurs. In heifers it is common for udder swelling and teat dilation to occur and it is also at this time that a number of heifers experience mastitis problems. Treatment with antibiotics appears to help but applying teat sealant at this time may also offer protection as well.

Dairy farming and mastitis go hand in hand. Much of the battle to limit mastitis must be focused on protecting the teat end.


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