Variations in the Vitamin C Content of Milk

PROCEDUREForty cows about equally distributed among the Ayrshire, Guernsey, Holstein, and Jersey breeds were tested 3 consecutive mornings in October and again in November.Sixteen of these cows were also tested both morning• and evening for 7 days.Subsequent tests included all 55 to 58 cows of the station herd, distributed about equally among the four breeds.In these tests 10 ml. of milk stood 30 minutes with 15 ml. of 10 per cent trichloracetic acid.Five ml. of the resulting serum was titrated with 2-6-dichlorophenol-indophenol (4, 5).Except as noted below all cows were fed, according to production, a ration consisting of alfalfa bay, atlas sorgo silage, and a grain mixture.No pasture was available to these cows.As a part of a study of vitamin C metabolism, which will be reported in detail elsewhere, 3 cows were fed after the April tests as much green rye as they would consume.By the end of one week they were each consuming approximately 65 Kg. per day of rye that tested 0.86 mg. of vitamin C per gram.This would be equivalent in vitamin C content to 30 gallons of orange juice per cow per day.The vitamin C contents of the milk and urine were determined at suitable intervals.Milk samples from 3 other cows previously found to give milk of comparable vitamin C content and constancy were also tested at the same milkings as the test animals.