Changes in Milk Products Sham Fed to Calves. III. Effects of Concentration of Fat

Abstract Liberation of volatile soluble fatty acids from sham-fed milk products (separated milk, 0.03% fat; whole milk, 4.4%; low-fat cream, 23%; and high-fat cream, 49%) and the accompanying changes in pH and bacterial counts were used as indicators of the lipolytic capacity of pregastric esterase in calves. Samples were collected for analysis immediately after sham feeding and serially during a subsequent ten-hour period of incubation at 38 C. The magnitude of lipolysis in the sham-fed products generally corresponded to the concentrations of fat therein. After two hours of incubation, the rate of change in the higher fat products declined markedly. During, terminal stages of incubation, acidity in sham-fed separated milk increased, apparently as a result of bacterial metabolism. Bacterial counts of the milk products increased as a result of contamination in sham feeding. During subsequent incubation, the numbers in whole milk and creams decreased, but subsequently increased. The decline probably was the result of toxicity of certain fatty acids. Pregastric esterase normally secreted by calves consuming whole milk seems to have the capacity to hydrolyze milk lipids in excess of quantities normally in the diet.