Staphylococcus aureus Mastitis: Cause, Detection, and Control

Control measures aimed at preventing S. aureus from entering the teat canal, namely milking time hygiene, has reduced the prevalence of this disease on many modern farms, yet the disease is still prevalent .

Staphylococcus aureus causes one of the most common types of chronic mastitis. Though some cows may flare up with clinical mastitis (especially after calving), the infection is usually subclinical, causing elevated somatic cell counts (SCC) but no detectable changes in milk or the udder

S. aureus bacteria produce toxins that destroy cell membranes and can directly damage milk-producing tissue. White blood cells (leukocytes) are attracted to the area of inflammation where they attempt to fight the infection.

The major reservoirs of S. aureus are infected udders, teat canals, and teat lesions, but these bacteria also have been found on teat skin, muzzles, and nostrils. The bacteria are spread to uninfected quarters by teat cup liners, milkers’ hands, washcloths, and flies

1. Milkers should always wear gloves and change them frequently, especially when dirty or after stripping an infected animal. It is recommended to fore strip five squirts of milk from each quarter and check for abnormal milk or flakes.
2. Dirt should be brushed off teats with the use of a dry, single-use towel. Water should not be used as part of any milking procedures, even if a sanitizing solution is added. Sanitizers do not maintain activity throughout a milking, and water can introduce pathogens that are very difficult to cure.
A commercially available pre-dip should be applied with a dipper or cup and given 30 seconds of contact time. Sprayers can be used, but proper coverage is difficult to attain, especially on the teats farthest from the milker. Foamers are also commonly used, but caution must be taken to ensure that adequate parts per million of the active ingredient reach the teat end and teat skin.
3. A separate paper or cloth towel should be used to dry teats and scrub teats five times or for 20 seconds (Rasmussen et al., 1992). Towels must not be used on more than one cow.
4. Milking units should be attached 90 seconds after first tactile stimulation (stripping or wiping, whichever comes first).
5. Teat ends should be examined for evidence of chapping, cracks, or lesions, which may harbour mastitis-causing bacteria.
6. An effective post-milking teat dip should be applied after milking, ensuring that the entire barrel of each teat is covered. At the end of each milking, any teat dip left in the dip cup should be discarded, and cups should be rinsed with water and allowed to dry.
It is important to educate your employees.

Antibiotic treatment will not control this disease, but it may, in certain cases, shorten the duration of the infection. Treatment effectiveness decreases as the cow becomes older and even as the first lactation progresses

Dry cow therapy is more effective in eliminating infections than lactating treatment.

Low mean Milking Vacuum

At a recent milking time visit to a high yield herd, I noticed mean claw vacuums during our milking time testing often getting as low as 30 – 32 kPa during peak milk flow, despite the system vacuum being 46 kPa on a mid-level installation The national mastitis Council recommends average claw vacuums between 36 and 42 kPa during peak milk flow, it was very important to understand what was going on. The milking machine can transmit infection onto teats and disturb normal teat health, quantifying the degree to which the milking machine might be contributing to the risk of new intra-mammary infection. Cows’ teat size and position have changed as have milk flow rates. Milk yields have been rising faster than unit attachment times. Milk flow rate has been shown to be positively associated with risk of new intra-mammary infection “Milking time testing” A milking-time test is a test performed while milking cows and with the milking system under normal use conditions. Some cows had been achieving milk flow rates approaching 7.5 litres/min. This is quite high for typical British cows, where flow rates often don’t exceed about 5 litres/min. The milking machine had a claw capacity of 220 litres with an 8 litre bleed from the claw the length of milk tube was over 3 meters with an inline cut off valve and in line automatic cluster remover canister The long milk tube was supposed to be 12.5 mm internal diameter , the real diameter measured was 11mm ,the slug length was excessive, however the Variable Speed Drive was not installed correctly and the recovery was affecting the vacuum drop by as much as 10 kpa . The pulsation rate was 49ppm .

Thermoduric Counts

Thermoduric Counts

EU legislation indicates that total bacterial count (TBC) in milk should be less than 100,000/ml. However, ideally and on many farms, a TBC of less than 15,000/ml can be reached. Thermoduric bacteria counts of greater than 1,000/ml are generally penalised. However, ideally this count should be less than 200/ml.

Thermoduric bacteria.

Thermoduric bacteria can survive exposure to temperatures considerably above their maximal temperature for growth. In the dairy industry, the term is applied to those organisms which survive, but do not grow, at pasteurization temperature. They usually include species of Micrococcus, Streptococcus, Lactobacillus, Bacillus, and occasionally gram-negative rods. The sources of contamination are poorly cleaned equipment on farm. These bacteria contribute to significantly higher Standard Plate Count on pasteurized milk (LPC counts). The thermoduric count has been used in the dairy industry as a means of detecting sources of organisms responsible for high counts in the final product.

Thermophilic bacteria.

In the dairy industry, the term thermophilic bacteria applies particularly to bacteria which grow in milk held at elevated temperatures (55 C or higher), including pasteurization, 62.8 C. The species that grow in higher temperatures include Bacillus species which enter milk from various sources in the farm, or from poorly cleaned equipment. When the milk is held at high temperatures for long periods, these bacteria rapidly increase in numbers and may cause taint defects or problems with respect to bacteria standards.

Psychtropic bacteria.

The microorganisms which play a significant role in biological processes in low-temperature environments have usually been called psychrophilic, meaning cold-loving. Psychotropic is used to refer to the bacteria that are able to grow rapidly at 7 C and below. Species of Pseudomonas, Flavovacterium, Alcaligenes, Acinetobacter, and Bacillus are often encountered among psychotropic group. These group of are generally non-pathogens, but in dairy products they can cause a variety of taints, including fruity, stale, bitter, putrid and rancid taints. Psychotropic bacteria are rarely present in the udder. The numbers of bacteria depend upon sanitary conditions prevailing during production and upon time and temperature of milk storage before processing. The influence of psychotropic bacteria in the shelf life of pasteurized milk will depend mainly upon the number present after packaging, the rate of growth, the storage period, and the biochemical activity of the organisms.

The simple answer for avoiding these organisms is sanitation!!!!


Peracetic Acid Uses, Health Risks & Workplace Guidelines

During a recent milking -time test I found it very uncomfortable to be in the milking area when the cluster flush was initiated.

Peracetic or peroxyacetic acid (PAA) is a strong oxidizing agent used for high level disinfection and sterilization at low temperatures. It is water soluble, and leaves no solid residue after rinsing and the end products are only water, oxygen and acetic acid (vinegar), making PAA a very environmentally friendly compound.

As an antimicrobial agent, PAA is broadly effective against a wide range of microorganisms

The properties of PAA that make it an efficient sterilant and environmentally friendly make it potentially dangerous to any employees exposed to it in the workplace. Unfortunately the health risks to workers from PAA exposure are not known by many employers. PAA in concentrations can be harmful to workers if they are exposed.

PAA is very irritating to the skin, eyes, nose, throat, and lungs, with the potential for causing permanent scarring of the skin, cornea, and throat. Higher exposures in the short term can also cause pulmonary edema as well as liver and kidney effects.

0.17 ppm: the level above which discomfort could be observed for an exposure of up to 8 hours per day.

No occupational exposure limits have been established for Peracetic Acid.
This does not mean that this substance is not harmful. Safe work practices should always be followed.

What to do with high cell count cows

When Bulk Milk Cell Counts are elevated there is plenty of incentive to reduce them – but what are the options?
Cows with subclinical mastitis infections have cell counts above 250,000 cells/ml, but no visible changes in the milk.
The question is how to remove the cells from the vat (and infections from the cows) most effectively.
• Treatment during lactation is NOT generally recommended. It has a relatively low chance of success and is expensive (milk discarded and antibiotic cost).
• Culling is a very expensive option unless the cows have chronic infections (high cell counts in two lactations with Dry Cow Treatment in-between) or have other reasons to leave the herd.

Antibiotic Dry Cow Treatment at drying-off is the best approach.

Whatever the approach to removing infections, it is essential to minimise spread to clean cows by hygiene at milking and 100% coverage of teats with teat disinfectant.
Identifying the infected cows
• Herd Testing provides Individual Cow Cell Counts (ICCCs) regularly during lactation.
Cows with any cell count above 250,000 are likely to be infected.
Diverting milk from these cows to feed calves for sale is also an option for some farms.
Treatment during lactation – usually not recommended
• Antibiotic treatment for subclinical infections during lactation usually has a low chance of success. It is just not possible to keep enough antibiotic in the udder for long enough. The costs in antibiotic and discarded milk are usually too high for the likely benefits, and there is increased risk of antibiotic contamination.
• The current recommendations are NOT to attempt treatment of subclinical cows
(with cell counts above 250,000 cells/ml, but no visible changes in the milk) except in specific circumstances.
For example herds with the majority of infections due to Strep agalactiae and possibly Strep uberis may see economic benefits from treatment during lactation. This should be assessed, based on cultures and economic analysis, in conjunction with your vet.

Antibiotic Dry Cow Treatment

• Most cows will cure infections over the dry period if they have sufficient time
(minimum of 6 weeks) and are treated with Antibiotic Dry Cow Treatment. Note, some cows are less likely to respond – especially older cows with high cell counts that have been present for two lactations.
• Early drying-off of high cell count cows that are in later lactation may be a good approach to decreasing Bulk Milk Cell Counts.
than usual and you should consider a blanket approach to Antibiotic Dry Cow
Treatment (all quarters of all cows at drying off).
• It is likely that cows will be at higher risk of new infections during the dry period and the use of a Teat Sealant to reduce this risk should be seriously considered.

Culling – a final step

A small number of high cell count cows can have a significant effect on Bulk Milk Cell Count level and milk quality payments. Chronically infected cows are likely to be a source of bacteria for other cows. Culling cows with chronic infections helps protect the healthy, young cows which are the future of the herd.
• Although culling is important in mastitis control, it is an expensive option. Farm cell count problems are seldom solved by culling alone. Failure to prevent new infections
will mean that other cows quickly take their place at the top of the high cell count list.
 Candidates for culling are cows that have:
• 3 clinical cases of mastitis in the one lactation
• chronic infection – a cell count above 250,000 in two lactations with Dry Cow Treatment in-between

Check your Vacuum Level

One of the most often neglected areas on a dairy farm is the milking parlour. Even though it is used two or three times a day, it is often assumed to be working properly and operated correctly. But it’s dangerous to think that as long as the motors run and milk flows through the pipeline, everything is OK. This may or may not be true. The two major problems with milking systems are malfunctioning equipment and operator misuse. The problems can occur separately or simultaneously. In either case, the dairy farmer increases his chances of lowering milk production and, ultimately, lowering income. Research shows a high correlation between the incidence of mastitis and poorly functioning or poorly operated milking equipment. Mastitis is not a new disease. It was recognized and studied even before the milking machine was invented. Because the dairy industry became more dependent upon efficient milking operations, the milking machine is now used on nearly every dairy farm in the united kingdom. In many cases, when a dairy herd’s incidence of mastitis increases, the first area to be targeted is the milking equipment. The milking system can be adjusted or adapted to function properly, but other factors can contribute to this problem.
• Higher average claw vacuum results in quicker milking but milking that may be less gentle or complete.
• Lower average claw vacuum results in milking that is more gentle and complete but not as quick.
A recent visit highlighted a issue with and excessively high vacuum level.
The plant normally ran at 47 kpa “working level “
After a high incidence of mastitis in the herd the farmer required a milking machine test, on arrival the vacuum was stable with very little fluctuation; however the average claw vacuum was at 51 kpa
Nobody is saying you cannot milk at this level, it is important to remember the High vacuum levels and improper use of the milking machine have been associated with teat orifice erosion and hyperkeratosis. The development of teat end lesions can create an environment for the concentration of and colonization of, damaged tissue by a variety of mastitis pathogens. Increased new infections from Staphylococcus aureus and Streptococcus dysagalactia are commonly associated with an increase in or high level of teat-end lesions  is having on your teat end,


New Milking parlours & parlour updates

For most dairy farmers the milking parlour is their place of business for at least half of each working day – typically four hours – so no wonder many want to improve throughput or reduce time allocated to milking.
Changing a parlour is not a step to be taken lightly.
Choosing any item of machinery can have implications for unit output and profitability,
It is suggested the main reasons for altering milking equipment is to reduce overheads, in particular labour costs, or to simply spend less time milking your cows.
But extending or changing the layout of parlours can require investment, as more often than not existing building and parlour layout may need to be altered.
Others may see updating equipment as a route to improved efficiency
Just like any machinery, parlour equipment requires regular maintenance.
The need for an annual parlour check as outlined in dairy farm assurance rules; don’t forget this is a minimum requirement and there are no penalties for exceeding it.
When sourcing new or used equipment direct from suppliers, it’s important to get it right first time.
Once installed, and before any cow is milked, get the parlour checked by an expert.
Defective or improperly installed equipment can have an immediate and long-term influence on both milking performance and – more importantly – cow health.
As well as possibly extending milking times, the augmented risk of teat damage from too high vacuum, faulty pulsation and ill-fitting teat cup liners can increase risks mastitis in a herd.
Ensure equipment to be used, whether new or second-hand, is installed by a suitably experienced and qualified engineer.
To qualify the above!
A recent visit to a customer whom had a second-hand parlour fitted, had issues with Bactoscan and fidgety cows.
The vacuum pump was installed at the far end of a loft, the oiler was empty and the pump was running dry, resulting in an underperforming pump.
The Vacuum regulator was also in the loft and the had not been checked for some months, to this end it was clogged with dust and was hunting excessively, the cheap vacuum gauge in the parlour was not recording this irregular fluctuation.
The access to the loft was a rickety old ladder, causing some concern for safety issues.
The moral of this is Out of Sight out of Mind!
When improving your Milking parlour consider
A Tank room
A Pump House
A Wash Room
Milking Parlour.
Access to equipment should always be safe, secure, clean and accessible.

Check your Cow’s Teats

Cows with dry skin on teats can produce skin damage
The problem with dry teat skin is  more bacteria thrives in  the cracks and can be painful. It has been known for a long time numbers of bacteria at the teat end is the biggest risk for a new mastitis cases. Dry skin is also painful, and pain can block oxytocin resulting in under-milked quarters leaving the milking parlour. It can also result in hyperkeratosis at the teat end, which heightens the risk of mastitis by interfering with streak canal closure and can create a place for bacteria to live around the teat end opening.
Dry, chapped teat skin most often has weather to blame. Other causes can include
Wet bedding. Recycled sand or manure can be higher in moisture than other bedding types.
High humidity poor ventilated sheds.
Lime with other bedding materials. It has the potential to dry-out and damage teat and udder skin and so must be adequately covered with chopped straw or sawdust, but is very useful in drying-out soiled wet patches on cubicle beds and controlling bacterial levels.
Pre dips with high parts per million (ppm) of free chlorine. These will strip the oils in the skin.
Post dips with low levels of skin moisturizers. These are cheaper alternatives used  to save money.
If you suspect your cows to have dry chapped skin use a post dip formulated with the correct skin moisturizing ingredients for your cows. Most dips do not have the exact ingredients on the label find a post dip that is well formulated with a combination of ingredients that will heal your herd’s teat health problems quickly and completely.

Are your Cows Happy during Milking

A recent visit to observe cow behaviour during milking and visible changes in teat condition immediately after milking had been noted. The conclusion is probably related to a combination of milking conditions and equipment.
The milking machine was compliant with the 2007 ISO standard.
An examination of the orifice of all teats of the cows was made during the visit for teat orifice hyperkeratosis also completeness of milking was noted
During the on farm observations it was also noted that milking cluster removal timings at the end of milking increased agitation of the cows seen as fidgeting, unsuccessful attempts to remove the cluster by kicking during this period.
The milking machine is 3 years old no adjustments had been made to the equipment during this time .
The next step is to carry out a milking – time test.


“What is the importance of  fore-stripping,”  Since the very first milk has the highest SCC, you may usually see a slight SCC increase if  fore-stripping is discontinued . it also aids in  early detection  of clinical mastitis , again contributing to higher SCC. “Cows with clinical mastitis that go undetected may also have a higher chance of developing chronic subclinical mastitis.

This practice should be done before attaching the milking unit  to help stimulate milk let-down, and increase milk flow rate. Some people prefer to fore-strip each quarter before the pre- dip is applied and the teats are wiped clean and dry. Others prefer to do the fore-stripping after the cleaning process is done
Both ways work equally well in realizing the benefits of fore-stripping. Several field trials have shown that fore-stripping will increase milk flow rate and decrease unit on-time. Some studies have also shown that the total amount of milk removed at each milking may be increased when cows were fore-stripped. Fore-stripping has the potential in many dairy operations to improve milk quality and teat end health, reduce the rate of new IMIs, and improve parlour performance.

I would suggest no less than four squirts from each quarter .