RELATIONSHIP BETWEEN ULTRASONOGRAPHIC ASSESSMENT OF THE CORPUS-LUTEUMAREA AND MILK PROGESTERONE CONCENTRATION DURING THE ESTROUS-CYCLE IN COWS

Ultrasonography was used to examine the cavity within the Corpus luteu m and to measure the Corpus luteum area during the estrous cycle in co ws (n = 12). Cows were divided into cows that had a Corpus luteum with (n = 7) or without (n = 5) a cavity. Ultrasound examination and colle ction of of milk samples for progesterone assay were performed at 2-da y intervals on days 0-12, and then daily from day 14 to the day of the next ovulation. The means for Corpus luteum area and for milk progest erone concentration during the estrous cycle were not significantly di fferent between cows that had a Corpus luteum either with or without a cavity. The correlation coefficients between Corpus luteum area and m ilk progesterone concentration during luteal development (days 2-8) we re 0.69 (p < 0.0001) and 0.75 (p < 0.0001) for Corpora lutea with and without a cavity, respectively, while, during luteal regression (days -6 to 0 relative to the next ovulation), they coefficients were 0.73 ( p < 0.0001) and 0.77 (p < 0.0001), respectively. The correlation coeff icients, combined for both stages of the estrous cycle and both luteal statuses, came to 0.69 (p < 0.0001). These results indicate that Corp us luteum area is significantly correlated to milk progesterone concen tration, and ultrasonographic assessment of the Corpus luteum is a rel iable method for estimating peripheral progesterone concentrations dur ing the estrous cycle in cows.