Milk A-Esterase Levels as Influenced by Stage of Lactation

Open Access
Publisher Website
Google Scholar
Abstract
Milk A-esterase levels were found to be very high in colostrum (average units of enzyme activity for 8 cows was 0.93 [mu]moles of phenyl acetate hydrolyzed/min./ml of milk). There was a rapid decrease in average A-esterase values during the first few days of lactation (0.19 enzyme units on Day 7). These values gradually decreased during the rest of the month to a low of 0.09 units. The average A-esterase activity remained essentially constant during the following 3 months. In colostrum there were considerable inter-(SD = 1.05) and intracow (SD = 0.42) variations in A-esterase activity. These variations decreased rapidly during the first few weeks of lactation (inter- and intracow standard deviations 1 month after parturition were 0.04 and 0.02 enzyme units, respectively) and remained low for the duration of the study. It was hypothesized that blood plasma is the principal source of A-esterase in the milk and that blood plasma A-esterase may enter the mammary gland through passive diffusion.