Milking Machine and Mastitis Control Handbook

Subclinical mastitis cannot be detected on a strip plate, but it is found through a high somatic cell count. A count of 1 million cells/ml indicates that over 30% of a herd's quarters are infected with mastitis.

Herds with high cell counts and many infected quarters will have losses in milk production and income in the range of 20-30%. A 500-cow dairy, averaging 50 pounds of milk per cow per day for 365 days a year, with a $16 per hundred pounds milk price that has a 20% loss would lose $292,000 a year because of mastitis ( Table 1).

ANATOMY OF THE UDDER

The cow's udder consists of four separate quarters containing a complex network of various sized ducts, blood vessels and capillaries, ligaments, and secretory tissue. Because milk is constantly being produced and is stored in the udder between milkings, it must be strong and well attached to the cow. In high producing cows, 60 pounds of milk may be stored in the udder between milkings.

Udder Support System

The size and shape of the udder may vary considerably with the age and inheritance of the cow. Attachment of the udder to the cow is by elastic and nonelastic suspensory ligaments ( Figure 1 ). The median suspensory ligament is located in the center of the udder and holds the udder up in the middle. The other inelastic set of ligaments on the outer walls of the udder are called the lateral suspensory ligaments and also aid in udder support.

Figure 1. 

Udder Divisions

The udder is divided into halves by the central supporting ligament and each half into quarters by a fine membrane ( Figure 2 ). While each quarter is separate and no transfer of milk occurs between quarters, antibiotics can be transferred from one quarter to others through the extensive blood network throughout the udder. This is the reason that a cow treated in one quarter with antibiotic must have milk from all quarters discarded, and antibiotics administered in the muscle or other areas of the body will end up in the milk through the blood supply system.

Figure 3. 

HISTOLOGY OF THE MAMMARY GLAND

The Alveolus

The alveolus is the basic component of secretory tissue. It is composed of epithelial cells that surround a cavity, the lumen. Milk constituents (protein, fat, lactose) are synthesized and secreted by the epithelial cells into the lumen of the alveolus.

The alveolus is surrounded by numerous muscle cells known as myoepithelial cells ( Figure 3 ). These are activated by oxytocin and cause milk ejection from the lumen of the alveolus. Milk is ejected from the alveolus through the capillary milk duct which empties into a series of mammary (milk) ducts that get progressively larger until eventually the milk reaches the gland and teat cisterns. Myoepithelial cells also are found on smaller ducts in the mammary gland and aid in milk removal.

Figure 5. 

Lobules and Lobes

Groups of alveoli form lobules that are drained by a common duct. One lobule may contain 150-250 alveoli. Lobules join together to form a lobe that is drained by a larger duct ( Figure 4 ). As described previously these also connect to form still larger ducts which eventually reach the mammary gland cisterns and ultimately the teat cistern and streak canal as milk exits the gland.

Figure 6. 

TEAT HISTOLOGY

The teat wall ( Figure 5 ) contains an abundance of elastic connective tissue and two layers of muscle tissue (an inner layer of longitudinal muscles and an outer layer of circular muscles). The teat skin is covered with a normal squamous cell epithelium and is hairless. The teat or streak canal is lined with epithelium and has a particularly thick layer of flat cornified epithelial cells.

Figure 7. 

This albuminous layer of cells is frequently referred to as keratin. Keratin is vitally important in preventing the entrance of mastitis causing organisms into the mammary gland.

THE LYMPHATIC SYSTEM

Lymph is a colorless fluid drained from tissue spaces by thin walled vessels. These vessels have many one-way valves that allow lymph to move only in the direction of the lymph node ( Figure 6 ).

Figure 8. 

The supramammary and other lymph nodes in the cow's body are responsible for disease resistance by forming lymphocytes, which are a form of white blood cell involved in protection against diseases.

When a mastitis infection occurs, the lymph nodes increase their output of lymphocytes into the lymphatic vessels, which discharge them into the cow's blood supply. Lymphocytes then travel to the udder to combat mastitis infection.

THE CIRCULATORY SYSTEM

The flow of blood to the udder is very important for milk production since it requires about 500 volumes of blood to produce one volume of milk. A cow producing 100 pounds of milk a day will require as much as 6000 gallons of blood to circulate to the udder. The extensive circulatory system needed to transport blood to the udder is depicted in Figure 7 .

Figure 9. 

THE MILK LETDOWN PROCESS

To harvest all the milk from the udder, you must have the cow's cooperation. To achieve this cooperation, treat the cow properly, not only during the milking process, but also from the time the cow is moved to the milking area.

A cow lets down her milk if she is stimulated properly before milking. Since cows seem to be creatures of habit, this stimulation process need not be extensive but should be consistent. Stimulation can include washing or massaging the udder and forestripping milk out of each quarter. During stimulation nerve impulses cause the pituitary gland to discharge the hormone oxytocin into the blood system. Oxytocin then circulates in the blood to the udder and stimulates contraction of the myoepithelial cells surrounding the milk-filled alveoli. The milk is then forced into the duct system and into the gland and teat cisterns.

If the cow becomes excited or suffers pain either before or during the milking process, the cow's cooperation stops. This excitement or pain causes release of epinephrine (adrenaline) from the adrenal gland into the blood stream. This reduces the blood and oxytocin supply to the udder and inhibits myoepithelial cell contraction and milk ejection ( Figure 8 ). In order to remove as much milk as possible from the udder, it is very important to treat the cow in a routine and gentle manner, both before and during milking.

Figure 10. 

THE MILK REMOVAL PROCESS

There is a positive pressure inside the cow's udder of about 0.4 pounds per square inch (psi) before the cow is stimulated; after stimulation the pressure increases to about 0.8 psi. The sphincter muscle at the end of the teat is tight enough to keep the milk inside, but if the muscle is not strong enough, milk will leak out even before the cow is stimulated.

Machine Milking

The milking machine usually applies 12.5 to 15 inches Hg (mercury) of vacuum to the outside of the teat. This produces a pressure differential of 12.5 to 15 inches Hg negative vacuum pressure on the outside of the teat compared with the 0.8 psi positive pressure inside the teat. This pressure differential is great enough to open the sphincter muscle and the milk is ejected, even at the end of milking when the internal pressure diminishes.

Since the vacuum applied forces milk out of the teat, it also forces blood and body fluids to the end of the teat. If a constant vacuum is applied to the teat, damage will occur. The pulsator and the double-chambered teat cups are designed to prevent this from happening ( Figure 9 ).

Figure 11. 

The role of the pulsator is to alternate atmosphere air and vacuum between the liner and shell. As already explained, the vacuum causes a pressure differential that removes the milk from the streak canal. When the pulsator admits atmospheric air between the liner and shell, the liner closes around and below the teat, which in turn flattens the streak canal causing the milk flow to end. The stress is removed from the inner and middle tissues of the streak canal wall.

The liner also applies a compressive force to the teat end during its collapsed phase, which relieves the effects of congestion at the teat end.

Hand Milking

The outside pressure on the teat is one atmosphere or 14.6 psi. The act of hand pressure and internal pressure forces open the sphincter muscle and the milk is removed.

MASTITIS

Mastitis is the costliest disease of the dairy industry today. Losses are estimated to be as much as $200 per cow annually. It is obvious that dairymen must control this disease to achieve maximum profit from their enterprise.

As explained earlier, epithelial cells synthesize milk constituents (protein, fat, lactose). Mastitis is a bacterial infection and 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, and 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 other 5% are caused by other organisms.

Contagious Organisms

These are spread by hands, milking units, etc.

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. They can be controlled with proper sanitation and are 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 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

These live in the cows' environment and are always present.

Coliform 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 herd, 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.

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 also 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 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 dry with a paper towel. The cows are milked and teats are dipped 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 teats 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, need for daily maintenance, and limited efficacy, backflushers are not routinely recommended.

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. areus and S. agalactia , the most common types of mastitis found in Florida.

There seems to be much controversy about the effectiveness of teat dipping on environmental pathogens E. coli and S. uberis . Some research has shown that teat dipping does not control these organisms. 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%, and chlorhexidine at 0.5%. 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. ag., strep. dysgalactiae, staph. areus , 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 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.

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.

COMPONENTS OF THE MILKING SYSTEM

The Vacuum Pump

The vacuum pump is the heart of the milking system. Its purpose is to remove air from the system, thus creating a vacuum. Pump capacity is a measure of how fast the pump can remove air and is, therefore, measured in cubic feet of air per minute (CFM). Pump capacity can be expressed as American Standard (ASME) or New Zealand Standard (NZ). One CFM ASME equals 2 CFM NZ. It is similar to measuring the pumping capacity of an irrigation system in gallons per minute. Since the rate at which a pump can remove air depends on the vacuum level, all pump capacity ratings are standardized by measuring them at 15 inches of mercury. At that vacuum level, a pump removes air at a constant rate.

The vacuum pump needs to be able to remove air at least as fast as it is let in during milking (air usage) in order to help keep the vacuum level constant. If air enters the system faster than the pump can remove it, the vacuum level will drop. If pump capacity is greater than air usage (which should always be the situation), the excess air pumped must be let in through the vacuum controller (regulator).

The balance tank or vacuum reserve tank serves two functions. First, it acts as a cushion to absorb any sudden inrush of air, which might result in a vacuum drop. Second, it acts as a trap for liquid while the system is operating, thus protecting the pump from internal damage. If two pumps are running the system, each should be connected to the balance tank. Usually, only one balance tank should be used. Excess tanks in the system create dead spots and interfere with the vacuum controller's ability to create a stable vacuum in the system.

Our recommendation for pump capacity is 30 CFM ASME to run the system plus 1.5 CFM/milker unit. This is a minimum and is for usable CFM, not pump CFM. This makes it very difficult to size a system since you must know the amount of leakage in the system before you start. Most systems in Florida have large enough vacuum pumps. If you are concerned that you don't have enough vacuum, you might try checking for leaks. In Table 2 , we see the capacity of systems found in the Florida survey.

Leakage in the vacuum system should not exceed 10% of the vacuum pump capacity. To determine the amount of leakage, all units are removed from the system, and the air flow is measured at the receiver jar. Leaks are determined by subtracting the CFMs measured at the receiver jar from the actual pump capacity.

In Table 3 , we see that Florida dairies have more leakage in their systems than is desirable. Only two of the 39 dairies surveyed had systems which met the standard.

Once you remove leakage from pump capacities, you will see that the usable CFMs per unit is much lower. Excessive leakage can be quite expensive since you may need a larger pump to stay ahead. Most leaks are found in the balance tank, especially if it is old and rusty and has long plastic lines that sag and come unglued. If you would like to check your system for leaks, take a piece of plastic wrap and place it loosely around the pipe joints. The plastic wrap will be sucked around the pipe joint wherever it is leaking.

Table 4 describes usable CFM's per unit, or pump capacity minus leakage. This is the vacuum available for milking.

Thus, on the average, Florida dairies had sufficient pump capacity; however, those on the low end of the range should observe their vacuum gauge regularly to insure that line vacuum remains stable.

Vacuum Pump Maintenance

1. Check belts - replace if worn or oil-covered, and keep tight.

2. Keep the motor clean.

3. If you have an oil reclaimer, clean the filter.

4. If you have a water pump, replace the water hoses at the first sign of leakage. Many of them get clogged with algae or scum. This may even burn the pump up if it doesn't get enough water.

5. Check balance tank. The drain on bottom should seal off. If old and rusty, replace it.

Summary

Most Florida dairies have large enough vacuum pumps, but have an excessive number of leaks. Before you buy a new vacuum pump, make sure that leaks are not the cause of your low capacity. Worn or loose belts also contribute to low pump performance.

Vacuum Controllers (Regulators)

A survey of Florida dairies revealed that an unacceptably high percentage of vacuum regulators were not working properly. This condition can easily translate into a severe mastitis problem. In this section, we will examine the role of the controller and describe how to maintain it and check for malfunctions.

The vacuum pump removes air from the system at a constant rate, but air is used at a highly variable rate in the milking operation. Vacuum controllers are installed in the milking system to hold the vacuum level constant. The controller does this by admitting variable amounts of air into the system. When little air is used in milking, more is allowed in by the controller. If no air is let in, it could create a vacuum of nearly 30 inches Hg, much higher than you want for milking. If excess air is allowed to enter the system, the line vacuum will drop below the desired level.

A good quality controller can sense very small drops in vacuum, which occur as air usage increases, and responds by admitting less air into the controller. This keeps the vacuum level constant. The controller should be able to hold the vacuum constant over its whole range of air flow capacity, and, when necessary, it should be able to shut down so that almost no air is admitted. The capacity of the controller should be more than the capacity of the vacuum pump.

Types of Controllers

Diaphragm-type controllers generally have the ability to sense small changes in vacuum, respond quickly, and hold the vacuum constant over their whole range of capacity. The most common diaphragm controllers are the Sentinel, Westfalia, DeLaval Servo, and D.E.C. Servo. The Surge Equalizer II is quite acceptable also although it is a spring type.

Old dead weight controllers are not very sensitive and they should be replaced. A million-dollar dairy should not be ruled by an old five-dollar controller.

Location of Controllers

The controllers should be placed in the system according to manufacturer's recommendations and placement will differ according to manufacturer. Controllers usually are placed on the main vacuum line that runs from the pump to the trap or the balance tank. It is important that it be located in a clean area that also is accessible for service. Installation in the parlor usually is not satisfactory because of the noise it produces. Some controllers must be double elbowed if installed on the balance tank. Many have sensors as part of the unit. They must be located in front of the controller and must have a correct length of tubing between the sensor and controller. Because of the complexity of those controllers, it is important that they be installed according to directions.

Checking the Response of the Controller

If you have your system analyzed, be sure to have the controller response checked. This may be done by removing the probes and placing an orifice flowmeter in the receiver jar, admitting air in 10 CFM bursts. There should not be more than one-half inch change up to 90% of the system's capacity. If equipment to check your controller is not available and you keep your controller clean and it is of the newer type, you should have no problems, as long as you can see no fluctuation on the vacuum gauge while milking. If you have the old dead weight controllers, you do not have to check them. They were not responsive when they were new--replace them.

Maintenance

Because of the complexity of these controllers, follow directions for cleaning. If the unit has filters, clean them when they are dirty, usually once a month, or more often if located in a dirty area, or you have a large pump. Large pumps require that all excess air must come through the controller. Most controllers that are fitted with filters must also be washed internally. In some, only the bottom half is washed while others may be completely washed. Most controllers need no lubrication and should not be oiled, which causes dirt and dust to collect and clog.

Summary

Vacuum controllers are a very important part of the milking system. No dairy should have an old controller, since new models are much more sensitive. Controllers should be installed correctly and kept clean so they function properly. Maintainance costs are a small price to pay to insure against a major mastitis problem.

Pulsators

The pulsator is the device that alternates vacuum and atmospheric air between the liner and shell and is responsible for the milking process. Vacuum at the teat end removes the milk by a pressure differential. This is called the open or milking phase.

The massage, or rest, phase begins when the pulsator admits atmospheric air in the chamber between the liner and shell. This collapses the liner on the teat end and provides massage to the teat. The massage cycle is necessary because while the milk is removed during the milking cycle by vacuum, this vacuum also draws blood and body fluids down into the teat. Without adequate massage, the teat and teat end may be damaged, thus causing an increase in mastitis.

This action makes the pulsator very important in the milking process. If the milking phases are not performed adequately, quarters will not be milked or milked very slowly. If the massage phase does not take place, edema of the teat will occur and the quarter will not be milked properly. In addition, teat end damage will occur. Either situation is bad for udder health.

The mastitis survey indicated that only 25% of all dairies in Florida had all pulsators working properly. Conversely, 75% of the dairies had malfunctioning pulsators.

Type of Pulsators

• Electric - usually direct current, constant pulsation. These are most common in Florida.

• Pneumatic - these run by vacuum. Most don't function well in Florida because of high humidity and feed dust.

Pulsation Rate

Pulsation rate is the number of times per minute the milk phase and the massage phase occur (the two phases equal one cycle). The most common rates are between 44 and 60 pulsations per minute. Forty-four pulsations per minute is quite common in Florida, but this is slow milking. Recent research results have demonstrated that 60 pulsations per minute may be the best choice.

Pulsation Ratio

Pulsation ratio is the proportion of one cycle that the milking machine is in the milking phase versus the massage phase. Most common ratios are between 50:50 and 70:30. In theory the higher the ratio, the faster that milking will take place; 60:40 seems to be the most common in new installations.

Analysis of Pulsators

There are several types of equipment used to check pulsator performance. Earlier machines used bellows and did an adequate job of graphing pulsator function. However, more advanced electronic testing equipment is now available. Both are acceptable to determine pulsator function. All equipment dealers and some veterinarians have this equipment.

Pulsators should be checked regularly. In Florida, where dairies are large, it would be wise for most dairies to buy their own equipment and check all pulsators each month.

If you clean your pulsators each month, replace rubber parts. If all pulsators sound the same when running, they are probably working properly. Clean pulsators are very reliable. Remember that, as with vacuum controllers, pulsators need not be eligible for social security before they are retired. If they are old and beat up, buy new ones.

Pulsator Maintenance

Pulsators should be cleaned at least once a month in Florida. Our unique herd size, hot humid weather, and the use of dusty feeds are very hard on these machines. If the small air inlet is blocked, no air will be admitted, no massage takes place, and the teat end of every cow milked by that unit gets damaged.

Epoxy-sealed pulsators may be cleaned by sucking water through the hoses. Make sure that the air inlet gets washed during this process. Other types of pulsators should be taken apart and cleaned monthly. Rubber piston caps should be replaced every 6 months.

Many new installations now have filtered pulsation air. This is an excellent idea and should decrease the frequency of required pulsator maintenance. But even filtered types should be dismantled and cleaned, with rubber parts replaced every 6 months.

Summary

With 75% of the dairies in Florida having malfunctioning pulsators, mastitis losses probably are high in these herds. To prevent disease, clean pulsators every month. Most pulsators do not malfunction because they are mechanically faulty, but because they are dirty.

The Milking Cluster

The cluster includes the liner, shells, and claw.

Types of Liners.

• Most liners used in Florida are one-piece narrowbore types and should be replaced after 1200 cow milkings.

• Stretch liners are used by a few dairymen in Florida. They should be replaced after 500 cow milkings.

• Silicone liners also are available and will last 6000 cow milkings. They are very expensive initially, but because of their extended life, their cost per milking is equal to or less than regular liners.

Liner Shapes

Round is the most common shape in Florida. Square liners also are quite popular in some areas of the state. Shape of liner used is more a matter of personal preference than a result of scientific evidence as to which is best.

One of the most important management considerations for liners is the frequency with which they are changed. The reason for replacing liners after the recommended number of milkings is that they stretch and no longer provide adequate teat massage.

Equation 1 shows the formula for determining number of days to use liners:

Equation 1. 

For example ( Equation 2 ), using liners with a 1200 milking life, 20 units, twice a day milking, and 500 cows:

Equation 2. 

Because of the large number of cows milked in Florida, it usually is more labor efficient to leave the liners on the units until it is time to discard them, rather than going to all the trouble of dismantling them each week and resting them for a week. This works fine up north where the dairyman milks 30 cows with three units two times per day.

Liner Vents and Claw Vents

It is very important to vent the milking cluster. This facilitates the movement of milk away from the claw and increases milking speed and prevents flooding of the claw.

Many liners used in Florida are already vented when purchased. If the liners are vented the claw vent should be blocked off, but this is easier said than done. Stainless steel claws may be silver-soldered shut; epoxy glue may work for a limited time. Superglues have been known to shatter some plastic