SOLAR EXPOSURE REDUCES PLASMA TESTOSTERONE CONCENTRATIONS, SPERM QUALITY AND FERTILITY IN MALE GOATS FROM SUBTROPICAL LATITUDES

<p><strong>Background.</strong> In subtropical latitudes, where goats are typically raised in rangeland conditions, daily solar radiation may strongly impair reproductive activity in male goats, thus decreasing their fertility. <strong>Objective.</strong> To assess the effects of solar radiation on plasma testosterone concentrations, sperm production and fertility in well-nourished male goats over the course of 1 year. <strong>Methodology</strong>. Control males were kept in a shaded pen (n = 5), whereas the solar-exposed males remained in an unshaded pen exposed to direct solar radiation (n = 5). In experiment 1, plasma testosterone concentrations and sperm production were measured. In experiment 2, fertility of solar-exposed and control males was determined when joined with anestrous female goats. <strong>Results.</strong> Plasma testosterone concentrations varied over time (P < 0.0001), and there was an interaction between time and the groups of bucks (P < 0.001). In solar-exposed males, testosterone concentrations were lower than controls in June, September, December and January (P < 0.05). The total number of spermatozoa per ejaculate and progressive sperm motility varied over time (P < 0.0001), but there was no interaction between time and groups (P > 0.05). The percentage of live spermatozoa and the percentage of cells with abnormalities varied over time (P < 0.0001), and there was an interaction between time and treatment group (P < 0.0001). In solar-exposed males, the percentages of live spermatozoa were lower than controls in June, August, November and December, while in May, this percentage was higher in solar-exposed males than in controls (P < 0.05). The percentage of abnormal spermatozoa was higher in solar-exposed males than in controls from June to December (P < 0.001). The percentage of females that kidded was lower in those joined with the solar-exposed (48%) compared with those joined with control males (79%; P < 0.001). <strong>Implications.</strong> Providing shade reduces the negative effects of solar radiation on sperm quality and buck’s fertility. <strong>Conclusion.</strong> Daily exposure to solar radiation deeply altered reproductive activity of bucks. Testosterone concentrations, qualitative sperm production and fertility, were much lower in solar-exposed bucks compared to the control bucks kept under shade. </p>