Assessment of correlations and concentrations of salivary and plasma steroids, testicular morphometry, and semen quality in different climatic conditions in goats

Abstract

The current study aimed to investigate whether steroids (testosterone, estradiol, and cortisol) in the saliva of goats reflects their concentrations in the plasma. Also, it aimed at ascertaining, for the first time, the effect of changes in climatic conditions (spring versus summer) on the aforementioned steroids, testicular volume, testicular echotexture (pixel intensity; PI, and integrated density; ID), and semen quality in goats. Saliva and plasma samples were collected from 7 male Shiba goats weekly in spring and summer for measurement of testosterone (T; ng/ml), estradiol (E2; pg/ml), and cortisol (ng/ml) using radioimmunoassay. The changes in testicular volumes (TV/ml) and echogenicity were monitored weekly using ultrasonographic assessments concomitantly with subjective evaluations of semen parameters. Results revealed a highly significant positive correlation (r = 0.72; P < 0.0001) between plasma and salivary cortisol. Mild significant positive correlation was found between salivary and plasma T levels (r = 0.31; P < 0.002). However, low non-significant negative correlation was reported between salivary and plasma E2 levels (r = -0.24; P > 0.05). Higher levels of salivary cortisol were found in summer than in the spring (3.8 ± 0.6 ng/ml versus 1.4 ± 0.3 ng/ml; P < 0.001). However, no differences in levels of T, E2, and plasma cortisol were recorded between spring and summer (P > 0.05). Values of testicular PI and ID were significantly (P < 0.001) higher in the summer (94.5 ± 4.9, 258,388 ± 13,190, respectively) than in the spring (74.0 ± 2.1, 200,922 ± 5704, respectively). Meanwhile, TV and semen parameters did not significantly differ between spring and summer. In conclusion, saliva can be considered as an alternative biological fluid for the measurement of cortisol and T, but not suitable for E2. Climatic conditions significantly impact the levels of cortisol in saliva and testicular echogenicity in goats.

Keywords: Climatic conditions; Correlation; Goats; Salivary steroids; Testicular echotexture; Ultrasonography.