Understanding laboratory Jargon

TVC: Total Viable Count

A TVC is not a specific micro-organism but rather a test which estimates total numbers of viable (viable means living) individual micro-organisms present in a set volume of sample. The TVC count may include bacteria, yeasts and mould species.
Clearly it is impossible to have a set of conditions that are ideal for all organisms likely to be present in any one sample. This should be borne in mind when interpreting the results. TVC results are however very useful for trend analysis whereby changes in the numbers of microbes present in a system can be monitored over time and multiple samples. Mastitis
Mastitis is an inflammation of the udder, typically caused by a microbiological infection.

Total Bacteria Count (TBC)

Low levels (<50,000/ml) are essential to ensure the manufacture of high quality milk as directly increases the shelf life of milk and allow the Society to manufacture the highest quality final products for our customers. High levels of TBC are an indicator of on-farm general hygiene conditions, milking equipment cleanliness and milk storage (temperature and time).

Somatic Cells
Somatic cells are cells from the cow (predominantly white blood cells, otherwise known as leukocytes) that are normally present in milk. During most mastitis infections, the number of somatic cells present in the udder increases to help the cow fight the infection. There are several types of somatic cells that have different functions in fighting infection. Somatic cells can contain lipolytic and proteolytic enzymes, which degrade fats and proteins, respectively. An increase in somatic cells count during a mastitis infection increases the amount of destructive enzymes present in the milk, which increases the rate of deterioration of the milk fat and protein.

Bacteria Count
The total bacteria count is the number of bacteria in a sample that can grow and form countable colonies on Standard Methods Agar after being held at 32°C (90°F) for 48 hours.
Coliform Count
The coliform count is the number of colonies in a sample that grow and form distinctive countable colonies on Violet Red Bile Agar after being held at 32°C (90°F) for 24 hours. Coliforms are generally only present in food that has been fecally or environmentally contaminated.

have developed mechanisms to resist heat and other lethal agents such as sanitizers. Most of these bacteria have an ability to create a protective form called a spore that is very tough to kill.
The spores end up in finished products and begin growing and damaging the milk product. The most effective way to minimize the LPC count is to prevent contamination of the milk with thermoduric bacteria. This means clean cows and clean equipment. Thermoduric bacteria are common in soil and fermented feedstuffs. When cattle are exposed to contaminated material, thermoduric bacteria get on their teats. Poor udder sanitization will allow problems to develop. Milkstone buildups in the system may protect some of these bacteria and allow them to multiply in the raw milk. The LPC test is a good estimate of both cow and system cleanliness.

Common Mistakes in the Milking Parlour

Maintaining a low bulk tank somatic cell count has always been a good dairy management approach. Low somatic cell counts are associated with improved milk quality, increased shelf life and cheese yield after the milk leaves the farm, increased milk production, and reduced veterinary and drug costs.
Market changes have led to an increased importance by milk buyers toward lowering bulk tank somatic cell counts at the farm level. As a result, many dairy producers have refocused efforts to lower somatic cell count. Often, the reasons for a high bulk tank somatic cell count can be found in the milking parlour. Following are five common parlour mistakes that should be avoided to keep somatic cell counts low.

1. Milking dirty or wet teats
Poorly cleaned or dried teats result in increased incidence of mastitis and higher somatic cell counts. The first step to milking clean, dry teats is to keep cows as clean as possible before they ever enter the milking area. Clean cows are exposed to fewer environmental mastitis-causing bacteria and they are easier to clean before milking. If you feel the need to wash a high percentage of your cows, you may want to reconsider how your pastures or cowsheds are managed to improve cow cleanliness.
Dirt, manure, or debris can often be removed by hand or with a towel without the use of water. When cows are excessively dirty, some use of water may be necessary to clean the teats. However, this practice should be the exception and not the rule. Water use in the milking process should be kept to a minimum.
If water is used, be sure to only wet the teats and not the entire udder. It is nearly impossible to dry the udder and this water ends up being drawn into the inflations during the milking process. Generally, the use of water in the parlour results in increased mastitis and higher bacteria levels in milk.
All teats should be thoroughly dried with a single-service, absorbent cloth or paper towel. Never use the same towel on two cows. All debris, manure and predip residue on the teats should be removed while drying, using a gentle, twisting motion. During the drying process, pay particular attention to getting the teat ends clean and dry. If teats are not adequately dried, water, containing mastitis-causing bacteria, may end up in the teat cups during the milking process and expose the open teat ends to these bacteria.

2. Poor pre- or post-dip coverage
Pre-dipping and post-dipping are two mastitis management policies. Unfortunately, carelessness in the milking parlour often leads to insufficient teat dip coverage. Predipping with a sanitizing solution eliminates bacteria on teat ends prior to milking and helps to control mastitis caused by environmental mastitis pathogens. The predip should remain on the teats for at least 30 seconds before drying.
As soon as possible after the milking units are removed, teats should be dipped with a post-dip, which has been demonstrated to be an effective germicide through independent research. An effective post-dip kills bacteria on teats, prevents organisms from colonizing in the teat canal and reduces the rate of new infections from contagious mastitis bacteria. When pre-dipping and post-dipping, at least ¾ of the teat should be covered, with a goal of covering the entire teat. Teat dip cups should be kept clean.
Some dairy producers choose to spray teats rather than dip. While it is possible to adequately cover teats with a spray bottle, full coverage is often inadequate when spraying teats. A good way to test the effectiveness of dipping is to wrap a paper towel around the teat just after dipping.
The goal is to see a continuous streak of teat dip on the paper towel, indicating the entire teat was covered. With spraying, you will often find broken streaks of teat dip because the opposite side of the teat is often not covered.

3. Too little or too much time between teat stimulation with the cow and milker attachment
Attaching milkers too soon or too late can result in excessive milking time or reduced milk yield. The timing of milking unit attachment is a critical step in a good milking procedure. Oxytocin, which causes milk let down, reaches peak levels at 60 seconds after stimulation.
Therefore, milkers should be attached within 1 to 1.5 minutes after teat stimulation. Synchronizing attachment with milk let down helps ensure that the milkers are attached during the time frame when milk flow is highest.

4. Spreading mastitis with contaminated hands
Contagious mastitis-causing bacteria,like Staph. Aureus, may live on your hands and be transmitted between cows during milking. At minimum, hands should be thoroughly washed with soap and water before milking. Ideally, because bacteria are less likely to adhere to gloves than rough, calloused skin, nitrile or latex gloves should be worn during milking.
Gloves minimize the spread of contagious mastitis between cows during milking and help protect the milker’s skin. Gloves are also easier to disinfect than bare hands. Whether gloves are worn or not, hands should be washed sporadically throughout the milking procedure.

5. Over milking
Care should be taken to avoid over milking, which can increase the incidence of liner slips and lead to teat end damage. Damaged teat ends are more susceptible to mastitis. When automatic take-offs are used, the unit settings should be adjusted to ensure they do not stay on too long. Additionally, it is important to resist the temptation to override the automatic detachment by putting the milker back on.
The process of machine stripping, or holding down on individual teat cups or milking clusters, should be avoided. Properly stimulated cows milked with correctly functioning and attached milking units should not have excessive residual milk left in the udder. The potential losses from machine stripping far outweigh any potential benefits.

Milking Efficacy

To reduce mastitis and maintain milk quality, dairy farmers need to keep milking equipment in good working condition. However, milking efficacy should be measured from two other viewpoints, the amount of time the milking cluster is attached to the udder (unit on time) and the percent of unit on time that milk is flowing at peak. When milk isn’t flowing while the unit is attached, it is not only unproductive, but more importantly, could damage the teat tissue, which could increase the risk of mastitis and decrease milk yield.

Regular Maintenance
A majority of dairy farms have their milking equipment tested to ISO 6690 Requirements and serviced as per manufacturer’s recommendations on an annual or six monthly cycles. Proper equipment function is necessary for milking efficacy. Not alerting and training staff in areas that could lead to poor milking efficacy to routines that don’t achieve consistent milk let down and could cause over milking. Either one of these problems can leave cows “In pain” for a period of time and expose teats to high vacuum levels.

During pre- stimulation before unit placement, nerves carry an electric signal to the cow’s brain. She then releases oxytocin into the blood and then to the udder. It takes about 1 to 2 minutes for oxytocin levels to increase in blood to optimally contract muscle cells around the milk ducts, which then squeeze the milk down toward the teats. The two important points about this oxytocin release are enough teat stimulation (at least 10 seconds of actual physical touching) and the duration of the lag time, that is, the time interval between when teats are first stimulated until the cluster is attached. Regrettably, with increasing herd size, the number of cows that can be milked through the parlour per hour is often recognised as more important. So common talk among dairy farmers is speed of throughput

Measure Milk Flow
How would you know if this is happening in your herd? A milking time test (dynamic test) will show up milk flow from the cluster and vacuum levels during unit on time.

Biphasic milking “under milking “

“Milking is so routine, we don’t even think about it. It just happens,”
The end goal for udder preparation before milking is to maintain a constant routine at each milking:

1. A minimum of 10 seconds of physical stimulation on teats.
2. A lag time of 60 to 90 seconds before units are attached.
3. A parlour routine that consistently accomplishes 1 and 2 from the beginning to the end of milking
4. When there is a high vacuum but little milk flow. This can happen any time before complete milk let-down, the cow lets milk down which appears to be complete milking, then stops for 15 – 30 seconds.

So why stimulate the teats? How important is lag time before unit attachment?
In a recent study of farms, a large percentage experienced biphasic milking “under milking “in more than 30 percent of the cows. Biphasic milking results when oxytocin has not reached the mammary cells at the time the unit is attached. In other words, it is a delayed start of peak milk flow. The goal in the modern milking parlour routine is to have less than 10 percent of cows experience biphasic milking” under milking “.

With biphasic milking, milk flow starts as it originates from the teat and gland cisterns, but then stops or slows considerably because milk let-down has not been activated. Milk flow may be stopped for 30 seconds or more until sufficient stimulation, or sufficient time allows the arrival of oxytocin that causes the milk flow to begin again.

The impacts from biphasic milking “ under milking “ can be uncomfortable to cows, and could result in congestion in the teat, high vacuum without milk flow can cause stress on the teat . Under milking can cause teat end roughness, and it has the potential to reduce milk yield.

Milk let down is now considered as important as over milking exposing the teat to full vacuum has extreme effect on the cows teat end .
As herd numbers increase in the UK it is more important to train staff and new employees to a constant routine without cutting corners.

How Much money is lost from high SCC cows?

How Much money is lost from high SCC cows?

Dairy producers endeavour to maintain high-quality milk, which contributes to a safe, sustainable food supply. Mastitis also impacts cow health and wellbeing and ultimately the economic success of the dairy. Many buyers offer incentives related to quality milk standards. Thus, a bonus is added to the milk cheque which is a payment for good practices .however this should not be the prime financial reward for reducing mastitis.

Mastitis decreases the capacity of epithelial cells to produce milk, or destroys epithelial cells. Infections, even those that seemingly cause minor (subclinical) increases in somatic cell counts (SCC), will result in lost milk production in an infected cow during her lactation. This loss is a lost opportunity to put real money in a producer’s milk cheque. However, a cow with subclinical mastitis has the same feed, housing, labour, and husbandry expenses whether she is achieving optimal production or losing milk to mastitis. Thus, subclinical mastitis is a “silent” drain on your money.

Mastitis causes damaging inflammation in the udder, even when the inflammation is mild. Beyond the lost payment for quality milk, treatment costs of clinical cases, lower reproductive fertility and reduced longevity and well-being of affected cows, mastitis also causes a negative day to day milk yield loss.

Milk yield loss for a cow commences at any SCC over 100,000 cells/mL The earlier a cow becomes infected in a lactation the greater the milk yield loss. Decreasing new infection rates during the dry and transition period is critical. Yield losses are relative to the cow’s potential. Cows that milk more lose the same percent of milk from mastitis as those that don’t, thus higher-producing cows lose more milk.

Spring Turnout !

Spring Turnout.

The cleanliness of the cow’s environment is closely linked to levels of environmental mastitis. Manure and dirt are a source of mastitis infection. If cows have to walk through a dirty environment then dirt will get splashed onto the udder, belly and tail. To avoid spreading environmental mastitis, a dairy cow’s coat and udder should be kept as clean as is reasonably practical. Cow comfort and welfare are also linked to cow cleanliness. The aim is to examine the main areas impacting on cow cleanliness and the steps that can be taken to promote cow cleanliness

How the cow is managed within her environment has a major impact on levels of environmental mastitis:
• Cows should be provided with a clean environment;
• Cow comfort and welfare should be optimised;
• Cows should not be rushed or stressed by inconsistent handling;
• Udders must be prepared carefully for milking;
• Every milker must adhere diligently to the agreed milking routine;
• Dry cow therapy is less important for the control of environmental mastitis than for the control of contagious mastitis, but is still an essential part of the overall mastitis control strategy

The following checklist contains common measures to promote cow cleanliness:
• Feed to avoid very loose dung which leads to dirtier cows;
• Install cow brushes to improve cow cleanliness;
• Avoid rushing cows when moving them;
• Group freshly calved cows separately;
• Avoid letting cows lie down for 20 minutes after milking to let teats close properly;
• Milk highest yielding cows first to reduce milk leakage;
• Milk cows with mastitis last.

At Grass
While most cleanliness problems are associated with winter housing and dirty collecting yards, somatic cell counts can remain high in the spring following turnout. You should continue to maintain cow and udder hygiene at grass through:
• Maintenance of roadways and gate-ways;
• Managing supplementary feeding to ensure that dung is not too loose;
• Using electric fences to exclude cows from heavily fouled areas;
• Avoidance of poaching around gateways and water troughs where possible.

Teat Dipping: Is Fundamental to Milk Quality

During the 1960’s researchers in the United Kingdom investigated and reported what became known as the first comprehensive plan to control mastitis. This mastitis control plan has been successful since being introduced and is based on the notion that the infection rate of mastitis is directly related to the number of bacteria present on teat skin when the unit is attached to a cow. Teat disinfection is the basis of a mastitis control plan.
The main function of any teat dip is to flush off the milk film that is left on the teats wherever they were exposed to vacuum during milking. Failure to flush off the milk film will result in a nearly perfect food for bacteria to grow on the teat skin before the cows are milked at the next milking. Once the milk film has been flushed off, the teat dip leaves a disinfectant on the skin of the teat to kill any current bacteria. Teat disinfection does not affect existing infections.

Complete Coverage
While it is recommended to cover the teat end and bottom one-third of the teat barrel, this is insufficient. The teat should be completely covered with teat dip. Although teat dip can be sprayed onto teats with a teat sprayer, in most cases, the teat coverage will not be sufficient and uses significantly more solution than proper dipping. The most common failure in most teat dipping/ spraying programs is not adequately covering teats with a good quality germicidal teat dip immediately after milking.
Because the role of teat dipping is to avoid bacteria colonization on the teat skin as well as the teat canal, it is critical to regularly and correctly cover the entire area of the teat that had contact with the milking unit. Teat dip coverage should be checked on a regular basis

The typical use rates for various application methods are as follows: spraying approximately 20 ml per cow, non-return dipper 6 ml to 8 ml, foaming 4 ml to 6 ml.

Think about storage and contaminating the teat dip, leaving lids off containers allowing air to possibly enter the container may have an adverse effect on your solution.

Culling Cows

Cows with chronic mastitis problems act as a reservoir of infection for the rest of the herd, they cost you money in treatment costs and lost milk production, and they spend more time in the hospital shed requiring time-consuming care – increasing your time. Cows that should be considered for culling include:

Cows with persistently high SCCs.

Cows that do not respond to treatment and continue to flare-up repeatedly with clinical mastitis.

Cows with infections that persist in spite of dry cow treatment.

Cows with mycoplasma mastitis.

Of course, other factors must be considered before culling (type of infection, milk yield, replacement options, etc.) but, many times removing a few highly problematic cows will yield big dividends on your SCC report and will be well worth the loss in the long run. Culling should never be considered a substitute for solving the underlying problem with high SCCs or increased cases of clinical mastitis on your dairy. Culling is just one component to a comprehensive mastitis control plan.

Can somatic cell counts get too low?

Can somatic cell counts get too low?

That seems to be a question I receive often from producers who are trying to achieve optimum milk quality.

Low SCC herds usually have low levels of contagious bacteria and limit the spread with good milking procedures and management practices. When these herds do get an infection it is usually environmental. These organisms are opportunistic, not invasive, meaning most animals that get these infections are immune suppressed or stressed, such as dry cows or early lactation animals. Low SCC cows are not more susceptible to environmental organisms, but clinical signs tend to be more visible and grab the attention of producers.

High cell counts cost money. The cost of a high cell count doesn’t just come from the penalties imposed or bonuses foregone when targets are not met; high cell count cows produce less milk than low cell count cows. A high cell count herd will also have more clinical mastitis. So reducing cell count can provide substantial savings – on average, reducing the bulk cell count from 250,000 to 150,000 will result in savings of around £50 per cow per year, most of which comes from a reduction in production of around 0.5L more of milk per day. So cell counts are a valuable tool which can be used to identify a problem, assess the cost of the problem, give a guide as to the solution, and to monitor the response to control programmes.

What is a somatic cell count (SCC)?

When the udder is infected somatic cells from the blood (white blood cells) move to the udder and into the milk to defend the organ against the invading bacteria. Without this response, elimination of mastitis, even mild cases, would be very slow and tissue damage greatly increased.

For an individual cow the ideal cell count is 100 – 150,000. Below 50,000, there is some evidence that cows respond more slowly to infection, particularly with E. coli, so they have an increased risk of mastitis. So as reducing bulk milk below 100/150,000 may increase the proportion of very low cell count cows, it may also increase the risk of clinical mastitis. Nevertheless because of the other benefits of low bulk cell count the answer is not to increase cell count but to maximise immunity (such as by minimising negative energy balance) and to keep the cows in as good an environment as possible

Water Troughs

A major study led by Cornell researchers reveals for the first time that water troughs on farms are a conduit for the spread of toxic E. coli in cattle, which can then spread the pathogen to people through bacteria in feces. The study was published Feb. 7 in the journal PLOS ONE.
“Water troughs appeared in our mathematical model as a place where water can get contaminated and a potential place where we could break the cycle,” said Renata Ivanek, associate professor of epidemiology in the College of Veterinary Medicine and the paper’s senior author. The hypothesis was then tested in the field – with surprising results.
People commonly acquire infections from shiga toxin-producing E. coli through cow feces-contaminated beef and salad greens. The main shiga toxin-producing strain, E. coli 0157:H7, causes more than 63,000 illnesses per year and about 20 deaths, according to the Centers for Disease Control. Though cows carry and spread E. coli 0157:H7 when they defecate, the bacteria do not make them sick.
“Farmers do not see a problem because there are no clinical signs in cows; it is totally invisible,” Ivanek said.
A vaccine to reduce bacterial shedding in cows exists, but the beef industry has little incentive to use it, partly due to cost, and the industry does not benefit from labeling beef as “E. coli safe,” Ivanek said. So Ivanek and a research team of 20 co-authors conducted a study to identify other ways to reduce the bacteria’s prevalence in cattle, which can vary over the year from zero to 100 percent of cows in a feedlot carrying the bacteria, with rates generally rising in the summer.
The researchers ran mathematical modeling studies to see if they could pinpoint areas in the farm where infections might spread between cattle. They found that water in a trough, especially in summer months, could heat and promote pathogen replication, causing more cows to acquire the bacteria when they drink. The researchers hypothesized that frequently changing the water in the summer could keep the water colder, limiting bacterial growth.
On most farms, water troughs automatically refill when they get low enough, and farmers can adjust the water levels so they refill more often. This tact saves water and keeps it fresher while ensuring cows still have enough to drink.
The group ran control trials in a feedlot over two summers. This involved reducing the water volume in troughs in randomly selected treatment pens and leaving the volume unchanged in control pens. They expected that reducing the water levels in troughs would prevent the spread of E. coli. Instead they found that it increased spread; in the treatment pens, the odds of finding shiga toxin-producing E. coli in cows was about 30 percent higher than in the control pens.
“Our modeling studies did pick up the right parts of the system,” Ivanek said, “but the mechanism that we postulated is the opposite from what we thought.”
More study is needed to determine why more water in troughs reduced E. coli in cows, but Ivanek questions whether the lower volume made it easier for cows to swallow debris at the bottom of tanks, or whether a fuller tank reduced E. coli concentrations.
The study will trigger more research on environmental sources of E. coli spread in cattle, Ivanek said.
Next steps include repeating the results in other feedlots, evaluating the effectiveness and cost benefit of using more water to reduce E. coli, investigating how seasons and temperatures play a role in prevalence of E. coli, and understanding the actual mechanisms that led to the results.
Wendy Beauvais, a postdoctoral researcher in Ivanek’s lab, is the paper’s first author. Co-authors included researchers from Texas A&M University, West Texas A&M University and Texas Tech University.
The study was funded by the U.S. Department of Agriculture, the National Institutes of Health and the Texas Veterinary Medical Foundation.