EFFECT OF DIETARY PHENOLIC AMINES ON TESTICULAR FUNCTION AND LUTEINIZING-HORMONE SECRETION IN MALE ANGORA-GOATS

To test the effect of dietary phenolic amines on pituitary-gonadal fun ction, 24 postpubertal male Angora goats were assigned during the bree ding season to a control diet or to graze on a pasture dominated by ph enolic amine-containing vegetation (PA). Compared with control bucks, bucks grazing PA had decreased (P < .001) serum concentrations of test osterone, increased (P < .001) triiodothyronine (T-3) and thyroxine (T -4), greater (P < .001) reduction in scrotal circumference (SC), lower (P < .001) body weight gains, and reduced (P < .01) semen volume. Spe rm concentration and progressive motility were not affected by treatme nt. On d 75 of treatment, endogenous and GnRH-stimulated LH secretion were greater (P < .01), but endogenous and stimulated testosterone sec retion tended (P < .10) to be reduced in the PA bucks relative to the controls. Endogenous serum concentrations of LK and testosterone were positively correlated in the controls, whereas no correlation was dete cted in the PA males. We conclude that during the breeding season, inc reased consumption of plants with a high concentration of phenolic ami nes can affect the reproductive competence of male goats in a manner t hat suggests a premature ending of the active reproductive phase. The concurrent influence of dietary phenolic amines on serum T-3 and T-4, and the relationship of these hormones with expression of seasonal rep roduction in domestic and wild ruminants, warrants further analysis of the relationship between dietary phenolic amines, thyroid function, a nd reproduction in these species.