Persistency of Fat Secretion during the Lactation Period as Affected by Age

Summary 1.Using a method previously described for the quantitative determination of persistency of milk and fat secretion, a study was made of the effect of age upon this character. 2.Data were presented indicating that there is a decline in the persistency of secretion during the lactation period as the dairy cow reaches maturity. 3.A summary is made of the literature indicating the nature of the stimulation of mammary growth and secretion and the relation to the problem of the influence of age was indicated. 4.The theory is advanced that the normal or hereditary rate of decline of milk secretion during the early lactation periods is retarded due to further division of cells which become functional through the stimulation of the follicular hormone, and to the increased activity of the cells due to an increased blood supply and the perfection of the functioning of the cells.