Effects of Simulated Self-Enurination on Reproductive Behavior and Endocrinology during the Transition into the Breeding Season in Male Goats (Capra hircus).

The objective of this study was to determine the effects of a simulated self-enurination (SE) on the hypothalamo-pituitary-gonadal (HPG) axis in goat bucks. Self-enurination in bucks is androgen-dependent and occurs primarily during the breeding season. The behavior is characterized by emission of urine from the erect penis onto the face and front legs; flehmen usually follows. Unpublished work in our lab demonstrated that SE may be used to present attractive cues to females, but may also serve as a self-excitatory sexual behavior, whereby urine or chemicals therein stimulate the HPG axis via accessory olfactory system excitation. Previously, our lab conducted experiments to assess this hypothesis by analyzing serum LH and testosterone (T) concentrations in samples taken after simulated SE containing SE urine or saline. Results from these studies suggested that simulated SE with SE urine may increase LH during the transition into the breeding season, and increase T during the transition out of the breeding season. In this study, we assessed both T and LH responses in bucks during the transition into the breeding season. SE urine for this study was collected during the previous breeding season, pooled, and frozen until needed. Simulated SE involves spraying 1 ml of urine through a modified 22G needle creating a spritz directed at the buck’s nose. Each buck (n=12) received a total of four spritzes, 15 min apart, of either SE urine (SEU) or control (AIR). Air was applied to prevent re-liquefying urine residue on the bucks’ faces. A switchback was performed in the following three weeks. Three blood samples were drawn 10 min apart before the first spritz, then 5, 10, 20, 30, 45 and 60 min after the final spritz. Serum LH and T concentrations were determined by RIA. No AIR bucks displayed flehmen. SEU bucks displayed flehmen 98% of the time (mean duration 21 s). Treatment with SEU resulted in a greater T increase from baseline than with AIR at 5 min (388% vs 133%, respectively; P <.05) and at 10 min (349% vs 159%, respectively; P <.05). Not sampling blood after each spritz complicated interpretation of the LH data. However, in SEU males the involvement of the HPG axis is reflected by a decrease in LH area under the curve (57.6 and 74.1 ng/ml x min for SEU and AIR, respectively; P <.1) when T was elevated. Our evidence suggests that self-enurination stimulates the HPG axis thereby facilitating sexual performance.