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