Factors associated with edema of the mammary gland in primigravid dairy heifers.

The severity and anatomical extent of mammary edema (edema) of 73 primigravid Holstein heifers was scored, and certain hormones in peripheral blood plasma were quantified. The objective was to obtain by least-squares analysis of covariance independent estimates of the association of each hormone and other factors with edema scores around first calving. Mammary edema prepartum increased with age of heifer and gestation length, decreased as calf birthweight increased, but was unrelated to seasonal fluctuations in temperature and photoperiod. The increase in edema during the last week of pregnancy was accounted for by associations with prepartum concentrations of hormones in plasma. The independent estimates of hormonal relationships to edema score prepartum were positive for plasma estrone and estradiol-17 alpha and were negative for plasma estradiol-17 beta and progesterone. Plasma prolactin was not related to edema score. After parturition, estradiol-17 beta was the only independent variable associated (negatively) with edema. The results indicate a complicated interaction among the sex steroids of late pregnancy wherein some steroids may promote edema and other steroids may inhibit edema in heifers.