Seasonality in Saint Croix male lamb reproductive development in northern Mexico.

The aim of this study was to determine the influence of the season of birth on the body weight, testicular size, testosterone concentrations, semen output and sexual behaviour in Saint Croix male lambs. Thirty-three lambs were born in spring (n = 10), summer (Sum; n = 12) or autumn (n = 11). Body weight and the scrotal circumference were weekly recorded; semen was also weekly collected by electroejaculation; and sexual behaviour towards oestrous ewes was weekly evaluated.

Social dominance affects the development of sexual behaviour but not semen output in yearling bucks.

Goats are polygynous seasonal mammals that establish dominant-subordinate relationships, especially in bucks. The aims of this study were to: 1) compare the reproductive development of dominant and subordinate young bucks allocated in dyads, and 2) determine if their previous dominant position affect their response to grouping. Twenty-four young bucks were allocated in dyads when they were 4 mo old, and the dominance position (DP) [dominant (DB) or subordinate buck (SB)] was determined with a test of competition for food.