Properties of the Colostrum of the Dairy Cow. VI. Creaming and Rate of Flow

Abstract

A study conducted over a period of 3 yr. involved colostrum from as many as 120 lactations. Observations on these samples showed that: (a) During the transition period, cream volume decreased and rate of flow increased, the changes being most rapid during the first three milkings. (b) In samples of colostrum from the first postpartum milking, the cream volume and the rate of flow (inverse expression of viscosity) were extremely variable, even when the mammary secretions were produced under apparently similar conditions. However, in any given sample there was a tendency for an inverse relationship between cream volume and rate of flow. (c) There appeared to be the following relationships of cream volume and fate of flow, respectively, to other properties and to various components of the first postpartum mammary secretions: when high values for specific gravity, solids-not-fat, total protein and albumin-globulin fraction were noted, the percentage of cream volume tended to be large and the rate of flow small. Though there was a general tendency for large cream volumes to be associated with high fat percentages, variability was pronounced; rate of flow apparently was independent of fat content. Neither differences in concentrations of casein, lactose and ash, nor presence of visible blood, nor variations of leucocyte numbers was related to cream volume and to rate of flow. (d) The data suggest that the variability in cream volume and in rate of flow are attributable primarily to the individual characteristics of the cow; environmental factors normally encountered in a dairy herd apparently played only a secondary role. © 1951, American Dairy Science Association. All rights reserved.