Sodium and chloride in cows' drinking water and freezing point of milk

The study was in two dairying regions of British Columbia, Canada, 700 Holstein-Friesian cows in 10 herds, to examine sodium and chloride in the drinking water of cows and to relate these to the composition of milk and to its freezing point. The Peace River had more sodium and more variation between herds in natural water supplies, which usually derive from surface dugouts, whereas the Fraser Valley region draws its water from mountain reservoirs. There were associated differences in the sodium content of milk between the two regions. These did not result in any regional differences in the freezing point of milk and there were no detectable changes in the chloride and lactose contents of milk to compensate for the higher sodium. The relationships between concentrations of milk lactose and milk chloride on the one hand and milk freezing point variations on the other were as expected.