Seasonal changes in testicular ultrasonogram pixel-intensity and their association with semen characteristics in rams

Abstract

Objective: To establish reference values for pixel intensity of testicular ultrasonogram of rams in breeding and non-breeding seasons, and to investigate if the seasonal changes in testicular echogenicity and heterogeneity are associated with semen characteristics. Methods: Five Awassi rams aged 3-5 years old and weighing 45-60 kg were subjected to ultrasonographic scanning of the testes twice monthly for one year (from January 2018 to December 2018), together with semen collection and evaluation of ejaculate volume, sperm motility, sperm concentration, sperm morphology and viability. The ejaculate volume was determined in a graduated collection tube (scale of 0.1 mL). Mass and individual sperm motility was expressed in percentage of motile spermatozoa under optical microscope equipped with a warm stage. Sperm concentration was determined by using a Neubauer chamber. Semen smears stained with eosin-nigrosin were used to determine the percentage of live spermatozoa and sperm cell morphology by using a light microscope. Results: The mean testicular pixel intensity was the lowest in winter and increased gradually from breeding season to non- breeding season, reaching its maximum value in summer (P<0.05). Pixel intensity was found to have a significant negative correlation with progressive motility (r=-0.605, P<0.05), and sperm concentration (r=-0.619, P<0.05). It is also positively correlated with the percentage of sperm morphological abnormalities (r=0.666, P<0.05). Conclusions: Pixel intensity values of testicular ultrasonogram in rams undergo marked seasonal changes that are associated with fluctuations in photoperiod and ambient temperature. The resulting values of testicular echogenicity (pixel intensity) throughout the year provide useful reference values for predicting the testicular function in Awassi rams.

Keywords

• testes; echotexture; pixel intensity; semen; season; rams