Changes Observed in Milk “Sham Fed” to Dairy Calves

Abstract

Summary 1. Pasteurized and superheated whole milks and separated milk were “sham fed” either from open pails or through nipples to fistulated calves. 2. A comparison of the properties of various samples of “sham-fed” milks with properties of their respective controls revealed in the case of pasteurized whole milk increases in rate of rennet coagulation, in tension of the body of the curd, in hydrogen-ion concentration, in lipolytic activity and in cream volume. The corresponding changes in superheated whole milk were in the same direction but of less magnitude. Separated milk manifested a slight increase in the rate of coagulation, an insignificant decrease in curd tension, no pronounced change in hydrogen-ion concentration but a marked increase in lipolytic activity. 3. Further alterations were evident after retention of the samples at 38° C. for two hours. Except for a slight increase in pH there were no marked changes in the control sample of pasteurized whole milk, but in the “sham-fed” samples all initial changes, except for a reduction in curd tension, were further amplified. The trends of all samples of superheated whole milk were in the same direction as in pasteurized whole milk. In the separated milk the only notable change in the control sample was a decrease in curd tension, whereas in the “sham-fed” sample there was a slight increase in rate of coagulation and in curd tension. 4. Several of the pronounced changes in the properties of the whole milk as contrasted to those of the separated milk were attributed in part to lipolysis, a reaction probably resulting from enzymes present in saliva and/or other secretions of the mouth and esophagus. 5. Ingestion of milk through a nipple as compared with consumption from an open pail exaggerated the changes in whole milks but produced little difference, except in increased lipolytic activity, in separated milk. 6. The pre-gastric alterations of milk apparently are of such a nature as to expedite subsequent digestion and assimilation.