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Dominant rams have preferential access to females, as they frequently interrupt sexual behaviour from subordinated. Testosterone concentrations are directly linked to sexual and aggressive behaviour and have important variations along the year. Therefore, it may be expected that the effects of dominance relationships on reproductive behaviour differ according to testosterone concentrations, and thus to the period of the year. The aim of this study was to compare the effects of dominance relationships on testosterone and sexual behaviour in different moments of the year in rams. Twelve rams were maintained in a single group. Social rank was determined in January (maximum reproductive development), May (regression of the reproductive status) and August (lowest reproductive activity), and the four rams with higher (HR) and the four with lower (LR) success index were used. Testosterone serum concentration was weekly measured four times during each experimental period. Sexual behaviour was evaluated in each period with an oestrous ewe, and with the oestrous ewe and another ram from the other social rank (each HR with each LR ram). Testosterone concentration was greater in HR than LR rams in January (p = 0.03), and all the behaviours were displayed more frequently in non-competitive than in competitive tests (p < 0.05). Rams modified their sexual strategy in competitive environments decreasing the display of sexual behaviour independently of their social status. This effect was observed consistently throughout the year: high-ranked rams have greater testosterone concentrations than LR rams only during the pre-rut, when they naturally compete to join the groups of ewes.

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Grouping previously unknown animals produces social stress, which might have negative effects on reproduction. The aims of the experiment were to determine if grouping unknown bucks (1) triggers a stress response and produces changes in body weight; (2) affects scrotal circumference, testosterone concentration, and semen quality; and (3) has differential effects between resident and introduced bucks. One group of nine Saanen bucks was transported and introduced (introduced bucks, group IG) to a group of eight Saanen bucks (resident bucks, group RG). On day 0, cortisol concentration and rectal temperature were determined, and from day -7 to day 29, body weight, scrotal circumference, and testosterone concentration were recorded and semen quality was determined. The stress response was different between groups: on several moments on day 0, resident bucks had greater cortisol concentration (P < 0.0001), while introduced bucks had higher rectal temperature (P = 0.02). Body weight decreased similarly in both groups from day -7 to day 2 (P < 0.0001), but on day 29, IG bucks were lighter than RG bucks (P = 0.05). Also, the reproductive response differed between groups: introduced bucks had lower scrotal circumference (P < 0.01), lower testosterone concentration (P = 0.02), and lower percentage of motile spermatozoa in the ejaculate (P = 0.05). It was concluded that grouping unknown bucks was stressful and negatively affected the reproduction, being more serious for the introduced than the resident bucks.

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