Pregastric esterase in milk sham fed to adult jersey steers.

Pregastric esterase activity was detected in reconstituted nonfat milk sham fed from a nipple pail to two 4-yr-old rumen-fistualted steers. Lipolytic activity, determined in a medium containing 5% tri-n-butyrin, averaged 8.6 plus or minus .4 lipase units. Further assays, in which activitiy was measured by free fatty acids released from a condensed milk substrate, averaged 166.9 plus or minus 9.2 mumol. These values are higher than those noted for young calves, indicating that secretion of pregastric esterase may persist in cattle beyond calfhood. Esterase activity in one of the steers fed whole milk until he was 2 yr of age showed no marked residual effect of earlier intake of milk fat.