A semi-extensive management system reduces plasma testosterone concentrations, sexual behaviour and sperm production in male goats from subtropical latitudes

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Abstract
Context: In subtropical latitudes, most goats are managed in semi-extensive management systems, eating only available vegetation. Underfeeding is common during the dry season and may reduce the endocrine and sexual activities of male goats. Aims: The aim of the study was to determine plasma testosterone concentrations, sexual behaviour and sperm production of male goats kept in a semi-extensive management system for 12 months, from March to February. Methods: Control males were placed indoors and were well nourished (n = 5). Experimental males were placed in a flock and grazed daily with females for 7 h, eating only natural vegetation (n = 5). Experimental males were fitted with an apron to prevent mating during the study. Plasma testosterone concentrations were determined every 2 weeks. Sexual behaviour and sperm production were determined in May and June (beginning of breeding season), August and October (middle of season), and November and December (end of season). Key results: Plasma testosterone concentrations were higher (P < 0.05) in control than experimental males in June and from August to December. The percentage of males refusing to ejaculate was lower (P < 0.05) in control than experimental males throughout the study. Total number of spermatozoa per ejaculate was higher (P < 0.05) in control than experimental males in May, June, November and December. Sperm progressive motility was higher (P < 0.05) in control than experimental males in May and June and from October to December. Conclusions: The results indicate that male goats in a semi-extensive management system have lower plasma testosterone concentrations, sexual behaviour, and sperm quantitative and qualitative production than those in a confined management system. Implications: Nutritional supplementation may improve the endocrine and sexual activity of male goats in semi-extensive management systems.

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