The composition of secretions obtained from the udders of heifers during pregnancy

Abstract

The initial work on the composition of the fluid obtained from the udders of virgin heifers has been extended and the character of the secretions of the mammary gland during first pregnancy has been investigated.The results obtained point to the following conclusions:During the first four or five months of pregnancy, the character and composition of the mammary secretion undergo no essential alterations. During this time, the mechanism of the gland which elaborates the normal constituents of milk is displaying feeble activity.After about twenty weeks the secretion undergoes a progressive change in character and composition. The characteristic milk constituents begin to disappear, and ultimately the secretion, which is now honey-like in consistency, contains about 40 per cent, total solids, of which about 35 per cent, is globulin. During this phase, which apparently corresponds with a definite stage in the gland's development, the normal activity of the cells which results in the production of caseinogen, lactose, etc. seems to be in abeyance.Removal of the honey-like secretion from the udder leads to a stimulation of normal mammary gland activity, in the same way as thorough and frequent milking stimulates activity during normal lactation. The viscous secretion gives way to a milk-like fluid. This is produced in relatively large amount and contains appreciable percentages of the normal colostrum corstituents.If the honey-like secretion is not removed from the gland, the transition from this phase to the eclostral phase appears to be much more gradual and is probably taking place uniformly throughout the remainder of pregnancy.