RHEOLOGICAL PROPERTIES OF THE ANTERIOR VAGINAL FLUID FROM SUPEROVULATED DAIRY HEIFERS AT ESTRUS

Anterior vaginal fluid samples were collected from 25 dairy heifers in duced to superovulation at 12 to 20 hours after estrus detection. Thix otropy and flow behavior were evaluated. In samples from 19 heifers, s tructural variation was registered and the fluids were considered to b e thixotropic; in the remaining samples (6 heifers), structural variat ion was not registered and the fluids were considered to be nonthixotr opic. The mean estradiol concentration of the thixotropic fluids (20.8 pg/ml) was lower (P=0.0002) than of the nonthixotropic samples (56.7 pg/ml). All the nonthixotropic samples of anterior vaginal fluid exhib ited Newtonian behavior. Of the 25 thixotropic anterior vaginal fluid samples, 10 exhibited Newtonian behavior while 9 exhibited non-Newtoni an behavior. Heifers in which samples exhibited Newtonian behavior had a higher mean estradiol concentration (38.8 pg/ml; P=0. 003) than hei fers in which samples exhibited non-Newtonian behavior (12.8 pg/ml). E stradiol concentrations were correlated negatively (P=0.02) with the i ndex of consistency (r = - 0. 46) and were not related to structural v ariation (P=0.08), although a certain tendency was shown. These result s have shown that thixotropic and flow behavior measurements in the an terior vaginal fluid of superovulated estrous heifers vary over a wide range and even qualitatively. This variation is related to estrogen l evels: Fluidity increases with increased plasma estrogen values, and t he integrity of the gel structure tends toward elimination.