Effect of exogenous estradiol and progesterone upon lipase activity and spontaneous lipolysis in bovine milk.

Three of six lactating Jersey cows received estradiol--17 beta and progesterone (.10 and .25 mg/kg body weight per day subcutaneously for 7 consecutive days. Lipase activity and acid degree were determined for morning milk samples stored 24 h at 4 degrees C. Whole milk lipase activity did not increase over control milk samples; however, lipase activity of cream fraction and percent whole milk lipase activity in cream fraction increased 200 and 100%. Increases in acid degree occurred also and were closely correlated (.8 to .9) with lipase activity of cream fraction and percent whole milk lipase activity in cream fraction. Cooling was not required to effect association of lipase with cream fraction. Two treated cows developed mastitis-like symptoms after elevation in lipase activity of cream fraction and acid degree. Estradiol alone evoked similar responses.