Effects of estradiol benzoate and estrus on N-acetyl-beta-D-glucosaminidase activity and somatic cell concentration in milk.

Quarter composite milk samples were obtained from five cows free of intramammary infection throughout an estrous cycle and after injection of corn oil and of estradiol benzoate (1 microgram/kg body weight) in corn oil. Samples were assayed for NAGase activity and somatic cell concentration. Least squares means for the enzyme were 1.46, 1.47, 1.43, and 1.41 natural logarithm nanomoles per minute per milliliter for control, estrus, corn oil, and estradiol benzoate, respectively. Milk somatic cell count means were 2.77, 2.71, 2.92, and 3.10 loge X 10(3) cells/ml. Treatment had no significant effect on enzyme activity or cell counts. Results suggest no adjustment of NAGase or cell count is necessary for stage of estrous cycle. When administered at physiological dosages, exogenous estrogen did not appear to influence either measure.