Bactoscan

The Bactoscan is a measurement of measuring the number of bacteria present in milk.

Importance

Target limits are set by the buyers of a farmer’s milk as to acceptable Bactoscan levels. Milk samples over the limit set will incur financial penalties through a reduction in the milk price paid to farmers.

Reasons for a high Bactoscan

1. Poor teat hygiene
   Due to contamination of the teats from the environment entering the milk.
2. Poor milk refrigeration
   Allowing the overgrowth of low levels of bacteria that are found in all milk prior to processing.
3. Poor parlour washing
   If the parlour is not washed properly after milking, there can be a build up of residues that encourage bacterial colonisation that can elevate the levels of bacteria in the milk.
4. Mastitis (clinical or subclinical)
   Infection of the mammary gland will usually cause elevated bacterial counts from affected cows. Certain types of infection tend to cause particularly high levels such as S. uberis and S. agalactiae.

Investigation of a high Bactoscan level on a dairy herd

When investigating a herd with a high Bactoscan problem, the following areas should form the basis of the investigation.

1. Record analysis
   All types of mastitis investigation must begin with an analysis of any available records. For Bactoscan investigations, look for a pattern when levels are raised. Reports of the Bactoscan are usually available weekly from the dairy or may be available online depending on the farm. If the Bactoscan has substantial fluctuations, this often suggests a problem with mastitis with the peeks occurring due to flares up of subclinical infections. This may also indicate poor detection of clinical mastitis where undetected clinical cases accidentally enter the bulk tank. If the Bactoscan shows seasonal significant seasonal trends, this suggests an environmental problem. Alternatively a relatively recent but very large and sustained increase should ring alarm bells that there is a problem with the cooling system necessitating immediate action. Failure in the wash up routine may create a similar pattern to that seen in the latter or may be a slower increase depending on the specific problem.
2. Environment
   If cow cleanliness is poor, then this can be a reason for raised bulk milk Bactoscan level. Methods to objectify the level of cleanliness have been described and form the basis of a useful tool to use on farm. This tends to be a problem seen during the housing period, but not necessarily and farms practicing seasonal pre-milking teat disinfection may be caught out by a bad spell of weather or a badly poached field.
3. Parlour routine
   Monitoring procedures in the parlour is essential as part of any Bactoscan investigation. A common error is for very dirty cows to be washed off before milking and the clusters applied before being wiped dry. This effectively creates a suspension of bacteria on the teat that can actually make the Bactoscan worse! A herd may be pre-milking teat disinfecting, but are they doing it properly? Possible problems with post-milking teat disinfection include the disinfectant being not left on long enough (usually there is a 30 second recommended contact time), the teat not being effectively wiped dry or ineffective products being used. Some farms may only use disinfection during the housing period when teat contamination risk is highest, which can still be effective for controlling the Bactoscan. The extent of gross contamination in milk can be visibly assessed by looking at the milk sock after milking.
4. Wash up routine
   The wash up routine and its investigation has been described elsewhere.
5. Bulk Milk Bacteriology
   Bulk milk bacteriology can be a very useful tool for Bactoscan investigations.