Milk electrical conductivity and mastitis status in dairy goats: Results from a pilot study

Mastitis in small ruminants has a major effect in reducing both yield and quality of milk leading to strong economic losses. In addition, mastitis is one the most frequently cited reason for culling. In dairy cows electrical conductivity (EC) of milk has been introduced as an indicator trait for mastitis. When the measurement of electrical conductivity (EC) of milk is based on time-series analysis of historical data, comparing values from different quarters within milking, satisfactory results in mastitis detection can be achieved. On the contrary, mastitis detection models based on EC measurement of milk within milking are not available in literature for dairy goats. Aim of the study was to evaluate the usefulness of milk EC, measured within milking from halves of each udder, to predict mastitis status in dairy goats at farm level. For this purpose, a group of 8 Saanen goats was involved in a 225-day study. Two foremilk samples were daily collected during morning milking from halves of each udder for a total of 4 samples per animal/day. Results of bacteriological analyses were used to distinguish between healthy (absence of mastitis agents) and infected (presence of contagious or environmental mastitis agents) udder halves. EC was measured in milk from halves of each udder during every morning milking at 1-s intervals using four experimental milking units equipped with conductimetric sensors. The average of the 20 highest EC values (X20) and the variation of the 20 highest EC values (σ202) within milking were calculated for each udder halves. In addition 4 EC traits based on X20 and σ202 were computed: the highest half udder X20 value within goat and milking (Max_X20), the highest half udder σ202 value within goat and milking (Max_σ202), the inter-udder halves ratio between the udder halves X20 values within goat and milking (IHR_X20), and the inter-udder halves ratio between udder halves σ202 value within goat and milking (IHR_σ202). Values for the traits were calculated for every milking throughout the whole lactation. Proc Mixed of SAS® 9.1 (SAS Institute Inc., Cary, NC, USA, 2008) was performed to test for significant differences in EC traits between healthy and infected udder halves and between healthy (absence of infected udder halves) and infected (presence of at least one infected udder half) goats. Results highlighted that the average of the 20 highest electrical conductivity half udder values recorded within milking in early lactation and the highest half udder X20 value within goat and milking in mid lactation could be potentially used in monitoring udder health of dairy goats.