Abstract :
The aim of this study was to evaluate the potential of luteal echotexture (mean pixel
value and heterogeneity), as a tool for assessing luteal function during different phases
of the estrous cycle in Toggenburg goats. Sonographic evaluations of the ovaries were performed
daily in nulliparous goats (n = 21), using a 5MHz linear rectal probe, commencing at
estrus (day 0). Blood samples were collected daily for plasma progesterone RIA and images
recorded on VHS tape and then digitized in TIFF format at a resolution of 1500×1125 pixels.
A representative elementary area (REA) of 5625 pixels (0.31cm2) of these images was
analyzed using custom-developed software, for mean pixel value and heterogeneity. Mean
plasma progesterone, luteal area and pixels all reached maximum values at approximately
days 13 and 14, during luteogenesis. Luteolysis was characterized by an abrupt decrease
in blood progesterone concentration following ovulation, and a gradual decline in luteal
area and pixel values. The luteal tissue area was positively correlated with plasma progesterone
concentration during both luteogenesis (r = 0.63; P < 0.05) and luteolysis (r = 0.50;
P < 0.05). Weak correlations were recorded between the mean pixel value and luteal tissue
area during luteogenesis (r = 0.34; P < 0.05) and luteolysis (r = 0.26; P < 0.05). Similarly,
weak correlations between the mean pixel value and plasma progesterone concentration
were recorded during luteogenesis (r = 0.24; P < 0.05) and luteolysis (r = 0.37; P < 0.05). The
pixel heterogeneity was not correlated with luteal tissue area or the plasma progesterone
concentration at any stage of the estrous cycle. The results show the association between
the corpus luteum echotexture and steriodogenic function to be weak and the present
ultrasound technology, to have limited potential in evaluating luteal function in goats.
