Valutazioni pluriennali delle caratteristiche riproduttive in stalloni impiegati in un programma di monitoraggio del materiale seminale

This study reports on the variation in semen quality and hormonal characteristics, during a 4 year period, of 16 stallions representing 4 breeds and ranging in age from 7 to 26 yr. Stallions have been divided in 3 age categories: ≤15, 16-19 and ≥20. Semen samples were collected into an artificial vagina and semen characteristics were examined for gel-free volume, morphology, spermatozoa concentration, total number of spermatozoa, motile spermatozoa and progressively motile spermatozoa at 0, 24 and 48 hours after collection. Semen concentration was significantly higher in stallion ≥20 yr of age and a significant breed variation was apparent in semen concentration, gel-free volume, total number of spermatozoa and progressively motile spermatozoa. In the group of 16 stallions motile and progressively motile spermatozoa at 24 and 48 hours decreased sharply during the 4 year period. Blood was collected from each stallion for hormonal analysis of testosterone and cortisol response at the dexamethasone suppression test were also evaluated. In order to predict stallion fertility testes and testicular arteries were examined from 14 stallions by using Doppler ultrasound. Stallions ≥20 yr of age showed a significantly lower TABF frequency compared to stallions ≤15. The connection between fertility, hormonal patterns and testicular artery characteristics in human beings suggest further investigations in stallion field.