Properties of the Colostrum of the Dairy Cow. V. Yield, Specific Gravity and Concentrations of Total Solids and its Various Components of Colostrum and Early Milk

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Abstract
A study was made of changes in yields, specific gravity, total solids, fat, solids-not-fat, total proteins, lactose and ash of mammary secretions collected from 111 dairy cows of the Holstein, Ayrshire, Jersey and Guernsey breeds during the transition from colostrum to normal milk. Considerable variation was found in values for yield and for the properties of early mammary secretions collected from different individuals at the same postpartal period. Variability in secretions from different individuals decreased as transition to normal milk progressed. Yields of mammary secretions increased markedly during the first week postpartum. Specific gravity, total solids, solids-not-fat, total proteins and ash decreased rapidly during the first four to six milkings, but only relatively small decreases were noted throughout the remainder of the 14 days of the study. Lactose changed in approx. an inverse ratio to the foregoing properties. The relative energy value of colostrum and milk and the percentage of the total energy contributed by proteins, fat and lactose are given.