Mastitis Control
Published: February 4, 2008
By: David R. Bray and Jan K. Shearer - University of Florida, IFAS
EFFECTS OF MASTITIS
Epithelial cells synthesize milk constituents (protein, fat, lactose). Mastitis is a bacterial infection that destroys these milk-secreting cells. Scar or connective tissue replaces the milk secreting tissue which results in a permanent loss of productive ability.
Mastitis organisms enter the udder through the teat end and streak canal. The streak canal is held closed by a circular muscle that holds milk in and foreign matter out. Also, the streak canal is lined with keratin, which traps and kills organisms that attempt to invade through the teat end.
MASTITIS-CAUSING ORGANISMS
About 95% of all infections are caused by Streptococcus agalactiae, Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis, and Escherichia coli. The remaining 5% are caused by other organisms.
Contagious Organisms
Contagious organisms are spread by hands, milking units, etc. They include S. agalactiae, S. aureus, S. dysgalactiae, and mycoplasma.
S. agalactiae lives in the udder and cannot exist outside the gland for long periods. It is susceptible to penicillin and, once eliminated, usually does not return to the herd unless infected cows are purchased.
S. aureus lives in the udder and on the skin surfaces of an infected cow. It can be controlled effectively with good management and is moderately susceptible to antibiotics when the infection first involves the gland. Older infections usually do not respond to treatment. Severe cases may cause death.
S. dysgalactiae may live almost anywhere: in the udder, rumen, and feces and in the barn. It can be controlled with proper sanitation and is moderately susceptible to antibiotics.
Mycoplasma is a unique organism. It does not fit the description of a bacterium or a virus and is classified as a microbe. Mycoplasmas do not have cell walls, leaving them unaffected by most antibiotics that interfere with cell-wall formation. Since no effective treatment is available, the best way to control this disease is to avoid purchasing cattle from known positive-tested herds. In addition, if cattle are routinely purchased, the bulk tank and pot herd milk should be sampled monthly. Mycoplasmas can be spread through the use of contaminated bottle mixes, syringes, and teat tubes in treating mastitis cows. Other infected cows are major sources of infection which can be transmitted by the milking machine components, hands of the operator, use of common rags and sponges, and directly from the environment. Teat dipping is essential for proper control.
The spread of contagious organisms are controlled by teat dipping and except for mycoplasma, are eliminated by dry cow therapy. Herds with contagious mastitis problems usually have to get back to dip cups and cover the whole teat to the base of the udder to control the spread.
Environmental Organisms
Environmental organisms live in the cows' environment and are always present.
E. coli bacteria are environmental pollution organisms; they live in feces, polluted water, and bedding material. Excellent sanitation is needed for their control. They are not susceptible to antibiotics.
S. uberis live most everywhere; in the rumen, feces and even in the udder. They can be controlled by proper sanitation and milking clean, dry udders.
WHEN DO INFECTIONS OCCUR?
The rates of new infections are the highest during the first two weeks of the dry period and the last two weeks of the dry period. New infection rates are also high in early lactation and diminish as the lactation proceeds.
Infection Dynamics
To understand mastitis infection, you must realize how its level changes on a herd basis. New infections can be brought into the herd in four general ways: 1) new infections during lactation; 2) new infections during the dry period; 3) infected heifers entering the herds; and 4) infected cow purchases.
Infections are eliminated in four general ways: 1) spontaneous recovery, elimination by the animal's own defense mechanism, 20% effective; 2) use of lactation therapy, usually 30-40% effective; 3) dry period therapy, usually 80-90% effective; and 4) culling the animals, very effective (100%).
Somatic Cells Described
Somatic means "of the body." Thus, a somatic cell is simply a body cell. Examples are skin cells, muscle cells, bone cells, or virtually any cell in the body. In milk, however, the predominant cell types are epithelial and white blood cells. High somatic cell counts in milk are indicative of infections, such as mastitis.
Epithelial cells of the alveoli are most numerous and active during early lactation when milk production is greatest. Throughout the cow's lactation, these cells slowly age and gradually are sloughed into the milk. Milk production drops during late lactation as these cells become fewer and less productive. While this is a dynamic process, the number of epithelial cells found in milk is relatively constant throughout lactation.
The other group of cells consistently found in milk are the infection-fighting cells of the body, the white blood cells. They always are present in the udder. However, in the presence of an inflammation they increase to tremendous numbers. Since inflammation generally results from infection, high somatic cell counts in milk are associated with mastitis.
MASTITIS CONTROL PRACTICES
Proper Milking Procedures
Proper milking procedures are important for the prevention of mastitis and for insuring complete milk removal from the udder.
Mastitis can decrease total milk production by 15 to 20%. To minimize loss and achieve maximum milk yield, a practical milking management scheme should be followed.
The term "milking management" includes care for the environment in which cows are housed or pastured. The dairy cow should have a clean, dry environment. This helps reduce the potential for mastitis and increases milking efficiency by reducing time and labor to clean udders before the milking process.
Moving Cows
Movement of cows should be in a quiet gentle manner. If cows are frightened or hurried, the milk letdown process may be disturbed. Therefore, rough handling of dairy cattle should be avoided.
Mastitis Detection
Milking may begin with a check of all quarters for mastitis. It is acceptable to strip milk onto the floor in a milking parlor or flat barn. Any cows that show clinical mastitis should be examined and appropriate action taken. If fore milking is not done, visual checking for inflamed quarters is done by milkers and herd health people.
Udder Preparation
The object of udder preparation is to ensure that clean dry udders and teats are being milked. The federal government's pasteurized milk ordinance (PMO) also states that a sanitizer must be applied before milking. This task may be accomplished by using an approved sanitizer injected in the floor-mounted cow washers or by using a hose and water with a sanitizer on the parlor. Single service paper towels or washed and dried cloth towels may be used.
Predipping
Predipping with teat dip has become popular. The advantage may just be getting the water out of the milking barn so wet udders are not being milked.
The procedure for predipping involves washing of teats with water and a sanitizer. The teats are then dried with an individual paper towel and dipped or sprayed with the sanitizer. A 30-second contact with sanitizer is needed to kill organisms. Then the sanitizer is wiped off with a paper towel. The cows are milked and teats are dipped again with the same type of sanitizer to prevent chemical reactions that could cause irritation to teats.
Predipping may be beneficial in reducing mastitis, but the actual dipping, dip contact time, and wiping with a towel increase the total milking time. If the dip is not wiped off, excessive chemical residues in milk may occur. If contact time is not sufficient, then it's a very expensive premilking regime.
Attachment and Detachment of the Milking Unit
To attach the milking unit to the teats, apply the cluster allowing a minimum of air admission and adjust to prevent liner slip. Air entering the unit may cause the propulsion of mastitis organisms from one infected teat into a noninfected teat. This also may happen when one teat cup is removed before the others.
Machine stripping usually is not needed on dairy cows. Machine stripping should not take more than one minute and no air should be allowed to enter the teat cups while this is being done. A downward force applied to the cluster while massaging the udder with the other hand is all that is needed.
Following milk-out, the machine should be removed only after the vacuum to the teat is shut off. This is accomplished most commonly by use of a vacuum shut off valve or milk hose clamp which prevents the backjetting of bacteria from one teat to another.
Backflushing
Backflushers have been developed to sanitize the liners and claws between milkings. Most units on the market have four or five cycles. The first cycle is a water rinse, followed by an iodine or similar sanitizer rinse, a clear water rinse, and positive air dry cycle.
Research has demonstrated that backflushers do reduce the number of bacteria on the liners between cows, but do not reduce the number of bacteria on teats. Backflushers also may stop the spread of contagious organisms, but this can also be accomplished at a much lower cost by teat dipping. There is no effect on environmental pathogens that are encountered between milkings.
Backflushers may be effective in stopping the spread of contagious mastitis; however, there is limited research to support this view. Because of the high initial cost, the need for daily maintenance, and limited efficacy, backflushers are not routinely recommended.
Milking Machine Factors
Research has demonstrated that "liner slip" is one area in which the milking machine may increase mastitis. This is when air is admitted through the top of the teat cup. Milk and bacteria, if present, may be propelled into the teat end of an adjacent teat, thus causing a new bacterial infection. Also, the use of malfunctioning pulsators can cause teat end damage and increase the rate of new infection.
The milking machine has little effect on mastitis if properly operated and functioning according to the manufacturer's specifications. Clearly though, when operated improperly, milking machines can have a role, and malfunctioning equipment can cause mastitis in several ways. If the pulsator is dirty and does not function properly, this will cause the massage phase to be eliminated with the teat end being damaged. A vacuum controller that is dirty also will not function properly and again damage the teat end. Damage to this entry area for organisms increases the risk of mastitis.
Post-milking Teat Dipping
There is only one way to effectively stop the spread of mastitis in the dairy herd, and that is by applying teat dip to every quarter of every cow after every milking. Teat dips are used to remove milk residue left on the teat and kill organisms on the teat at the time of dipping. They also leave a residual film of sanitizer between milkings.
Are teat dips effective against all mastitis organisms? Yes, teat dips have been shown to effectively reduce mastitis caused by S. aureus and S. agalactia, the most common types of mastitis found in Florida.
Post-milking teat dipping is effective in eliminating environmental organisms E. coli and Strep. uberis on the teats after milking. These pathogens are found in the cow's surroundings; if there is udder-deep mud, the teat dip will be removed and a new infection may occur.
Types of teat dips
There are many effective teat dips, including iodine at 0.1%, 0.5%, and 1.0%. Also, although it is not labeled for teat dipping, hypochlorite at 4.0% with a sodium hydroxide content less than 0.05% was effective in field trials. There are many more teat dips on the market that are effective in preventing new infections. Effective coverage of the teats is more important than the type of dip being used.
Dip or spray
If contagious bacteria is present in your herd (Strep. agalactiae, Strep. dysgalactiae, Staph. aureus, or mycoplasma), you must dip the whole teat to the base of the udder to stop the spread. Wand sprayers are acceptable for herds that have only environmental mastitis, since teat colonization is not a factor. Hand-held spray bottles are almost worthless in getting proper coverage of dip on the cow's teats, so they should not be used.
Dry Cow Therapy
Dry cow treatment is administered after the last milking of the cow before the dry period. Care must be taken to scrub the teat end with cotton and alcohol before infusion and to use teat dip after infusion.
There are many antibiotics available for dry cow therapy. High levels of penicillin and dihydrostreptomycin, the cloxacillins and other products specifically for dry treatment are effective.
The idea of dry period therapy has been accepted because antibiotics can be put into a slow release base that allows them to stay in the udder longer. They are not constantly being milked out of the udder as is the case with lactation therapy. Antibiotics can be administered in higher quantities because there is no concern for milk levels and antibiotic residues.
While dry treatment is very effective, it must be administered properly and the dry cows must have favorable environmental conditions. Teat ends must be scrubbed clean with cotton alcohol pads before injecting the dry treatment. If the teat ends are not cleaned properly, you may inject into the udder very high numbers of bacteria, which would overwhelm the antibiotic just administered. Unsanitary treatment procedures cause rather than eliminate mastitis.
Management of dry cows also is very important in mastitis control. If dry cows are exposed to muddy or dirty conditions, risks of mastitis will increase. This is especially true at the time of calving; cows are under much stress during this period and if an udder is exposed to wet dirty conditions, mastitis will increase. If you believe that your dry cow therapy program is ineffective, it may be because of poor treatment procedures and/or improper management of the cows during the dry period and at calving.
Culling
Culling cows for mastitis is effective in eliminating mastitis in the herd. Cows that have been treated many times in a single lactation are prime candidates for culling, as they may no longer be profitable because of discarded milk and antibiotic costs. It is usually more profitable to carry out preventive mastitis control procedures and cull only old chronic cows rather than to try and control mastitis by routine culling.
SUMMARY
Mastitis is a very costly disease, but losses can be reduced greatly by following an effective control program, which should include the following items:
1. Handle cows gently to achieve highest production.
2. Follow proper milking procedures, milk clean, dry udders, apply milking units properly, and make adjustments to prevent the admittance of air into the teat cup liners and prevent liner slip.
3. Dip cow's teats after milking to prevent new infections.
4. Treat all cows going dry with an approved dry cow drug in commercially prepared tubes to eliminate existing infections and prevent new infections during the dry period.
5. Cull chronically infected cows.
Footnotes
1. This document is DS7, one of a series of the Animal Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 1986. Revised June 1996. Reviewed June 2003. Visit the EDIS Web Site.
2. David R. Bray, Extension Agent III; Jan Shearer, associate professor, dairy research, College of Veterinary Medicine, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
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