Development and test of a portable device to monitor the health status of Sarda breed sheep by the measurement of the milk electrical conductivity

Abstract

The electrical conductivity (EC) of milk is a parameter which is often used for identifying sub-clinical mastitis in dairy animals. It is widely used for cattle, and is measured either by means of probes integrated into the milking machine or by means of portable devices. However this is not the case for small ruminants, where the available devices are few. The aim of this study is to deepen the knowledge of about the relationship between EC and certain constituents of Sarda sheep milk, and thus to develop a portable device specifically designed for on-site measurement of conductivity and to estimate the somatic cell count (SCC) of Sarda sheep milk. Therefore, the device allows a rapid test for checking the acceptability of milk to monitor the effects of udder infection. The receiver operating characteristic (ROC) method was used to evaluate how efficacious EC was in discriminating between animals with a somatic cell level higher or lower of a threshold value previously defined. The cut-off values, sensitivity, specificity and the area under the ROC curve for EC were, respectively, 4.835 mS/cm, 73.08, 75.46 and 0.804, using a threshold of 700 000 cells/ml. Our results gave a positive evaluation of the portable device that we had designed for estimating the SCC in sheep milk. Only 8.8% of the samples were incorrectly identified as negative. A portable device for EC measurement is a useful tool for monitoring the somatic cell level individually, and allows early and efficacious action to contrast new intramammary infections. ARTICLE HISTORY

Relationship of mammary gland health status and other noninfectious factors with electrical conductivity of milk in Manchega ewes

“…The negative correlation of EC with the fat content of milk agrees with Caria et al (2016), Prentice (1962), and Mucchetti et al (1994), who stated that fat globules increased the actual distance in the migration of ions that tend to cross over between the 2 electrodes of the conductometer. Albenzio et al (2002), Leitner et al (2004), Bianchi et al (2004), andSantos et al (2007) observed a decline in the fat content of milk from ewes with mastitis, which along with the ion concentration would explain the increase in EC observed in the milk from the infected glands.…”

“…However, they also observed that when taking the difference in EC between both glands of the same animal into account, the outcomes improved considerably (70% sensitivity, 93% specificity, and 89.1% of samples classified correctly for a difference between glands greater than 0.3 mS/cm). The results obtained by Caria et al (2016) were also better than those obtained in this work; they achieved sensitivity and specificity of 73.08% and 75.46%, respectively, setting an EC threshold of 4.84 mS/cm. These results show that for EC to be used as a method for detecting mastitis in sheep, as Díaz et al (2011) also noted, we should develop detection methods that would not be affected by the variations arising in milk EC due to intrinsic animal factors (parity number, milking session, and lactation stage) and not be limited to setting absolute thresholds.…”

“…The authors of those studies concluded that as lactation progressed the blood-milk barrier permeability increased, causing an increase in Na + and Cl − concentrations in milk. In Sarda ewes, Caria et al (2016) also obtained a high correlation coefficient (r = 0.893) between the EC of the milk and its chloride content…”

“…McDougall et al (2002), despite finding no significant differences between the impedance (EC inverse property) of milk from healthy and infected glands, obtained a negative correlation between the impedance and SCC (r = −0.27), leading them to deduce that the increase in SCC must be related to an increase in EC. Caria et al (2016) found a positive correlation (r = 0.31) between milk EC and SCC in Sarda sheep. In the same study, they achieved 73.08% sensitivity and 75.46% specificity, setting an EC threshold of 4.84 mS/cm, which was then applied in the evaluation of a prototype designed to detect subclinical mastitis by online gauging of the EC of the milk.…”

IoT smart add-on for small-farm milking machine

“…The novelty of our solution is based on the ability to control milk in-flow, working with any small size milking machine, provide three main indicators: overmilking phase alert, milk temperature, subclinical mastitis probability indicator, furthermore, it has the capability for data collection. We observed multiple researches aiming to develop a portable device to monitor the health status based on the threshold value of electrical conductivity (EC) [9]. However, we have not found similar research on the solution for control milk in-flow working with any small size milking machine.…”