199. The chloride content of milk

Extract

The frequency distribution of the chloride contents of 7802 samples of milk, grouped into morning and evening samples, monthly samples for three consecutive years from the Institute herd, samples from Shorthorn, Guernsey, Ayrshire and Friesian cows, and other miscellaneous samples, has been determined. The mode for morning milk is 81–90 and for evening milk 71–80 mg. %. The mode for Guernsey and Shorthorn milk is 71–80 and for all (6076) samples, 81–90 mg. %. The mode for milk from herds of Friesians known to give milk of low content of solids-not-fat was 111–120 mg. %, but this must not be taken as the value for this breed generally. The average for Shorthorn milk is 97, Guernsey 93, Institute herd 93, all samples 98, special Friesian herd 128 and bulk Institute milk 85 mg. %.

Factors influencing the chloride content of milk such as breed, age of cow, lactation period, number of lactations, seasonal effects, and udder troubles have been discussed from inspection and by deduction from the series of values obtained.

The electrical conductivity of milk increases with chloride content but there is some deviation from the linear law. The conductivity increases at a greater rate than the chloride content in samples high in chloride, probably owing to the increase in electrolytes other than chloride.