Diagnostic significance of electrical conductivity in milk
The electrical conductivity of milk is an inverse indicator of the resistance of milk and basically depends on the strength of the vascular reaction. When the inflammatory process begins in the udder, the concentrations of sodium, potassium, calcium, magnesium, chlorine and other ions present in milk will change. Milk becomes more conductive to electricity.
The electrical conductivity of healthy cow’s milk is 4.0 – 5.5 mS/cm. It changes very quickly when the health of the cow changes. These changes are often associated with mastitis, although they can also be due to other health problems. Changes in electrical conductivity are also associated with genetic factors, lactation, changes in milk composition. Therefore, when assessing the health of cattle, this indicator should not be assessed separately, but together with other indicators.
Lactose and electrical conductivity
Monitoring changes in lactose and electrical conductivity in milk is considered one of the most effective methods for early diagnosis of mastitis in dairy systems with integrated sensors. The electrical conductivity of milk increases because the milk becomes heterogeneous, as “clots” appear, slowing down the flow of milk. The amount of lactose decreases with the onset of inflammatory processes in the udder.
Electrical conductivity and SCC
The relationship between electrical conductivity and the change in somatic cell count (SCC) is not direct, although its observation can be used as one of the main indicators for the early diagnosis of mastitis. With an increase in conductivity of more than 6.0 mS/cm, subclinical mastitis can be suspected. As the inflammation progresses, the conductivity also increases, and it is the highest when SCC in milk reaches 400-600 thousand/ml.
Values of changes in electrical conductivity in milk
| Electrical conductivity value | 4,0-5,5 mS/cm | 5,5-6,5 mS/cm | >6,5 mS/cm |
|---|---|---|---|
| Indication | Electrical conductivity of milk is characteristic of cows with healthy udders | Changes in udder tissue and subclinical mastitis can be suspected | Clinical mastitis with increased SCC is often detected |
| SCC | Within SCC norm | SCC levels in milk may be increased | Electrical conductivity of milk increases until the SCC in milk reaches 600 thousand/ml, and then the electrical conductivity starts to decrease again |
| Lactose | Norm | Lactose level in milk may decrease | Lactose level in milk decreases |
| Proteins | Norm | Protein level in milk may decrease | Protein level in milk decreases |
| Fats | Norm | Fat level in milk may decrease | Fat level in milk decreases |
| Amount of milk | Amount of milk produced has not changed | Amount of milk produced is unchanged or slightly increased | Amount of milk produced decreases |
Methods for determining electrical conductivity
Laboratory tests and mobile devices
The electrical conductivity of milk can be measured with special mobile devices or equipment in the laboratory, but this is not always practical and sufficiently informative. It is very important not only to determine the value of the electrical conductivity of milk, but also to notice when it has changed and its correlation with other indicators of milk. Most dairy systems on farms have the ability to determine the electrical conductivity of milk, but not all of them can do it in real time and correlate the data with other milk indicators.
BROLIS HerdLine milk analyzer
The in-line milk analyzer BROLIS HerdLine is like a small laboratory on your dairy farm. The analyzer examines the composition of each cow’s milk during each milking. This “mini-spectroscope” is installed in the milking stalls or milking robot in the milk line and does not use additional reagents and does not require special maintenance.
The analysis of protein, fat, lactose and electrical conductivity provides a proper evaluation of the health, productivity and economic efficiency of dairy cattle. The data collected during milking is processed in real time and can be viewed using the BROLIS HerdLine application.
What affects electrical conductivity?
The main causes of increased milk conductivity are udder reaction, increased ambient temperature and changed feed. The electrical conductivity of cows of the first lactation is the lowest. It also changes during lactation itself, depending on the amount of milk produced, fat concentration, milk solids and milk fraction. Changes in electrical conductivity in the case of mastitis are influenced by the causative agent of the disease.
