Effect of dietary phenolic amines on testicular function and luteinizing hormone secretion in male angora goats.

Abstract

To test the effect of dietary phenolic amines on pituitary-gonadal functions, 24 postpubertal male Angora goats were assigned during the breeding season to a control diet or to graze on a pasture dominated by phenolic amine-containing vegetation (PA). Compared with control bucks, bucks grazing PA had decreased (P < .001) serum concentrations of testosterone, increased (P < .001) triiodothyronine (T3) and thyroxine (T4), greater (P < .001) reduction in scrotal circumference (SC), lower (P < .001) body weight gains, and reduced (P < .01) semen volume. Sperm concentration and progressive motility were not affected by treatment. On d 75 of treatment, endogenous and GnRH-stimulated LH secretion were greater (P < .01), but endogenous and stimulated testosterone secretion tended (P < .10) to be reduced in the PA bucks relative to the controls. Endogenous serum concentrations of LH and testosterone were positively correlated in the controls, whereas no correlation was detected in the PA males. We conclude that during the breeding season, increased consumption of plants with a high concentration of phenolic amines can affect the reproductive competence of male goats in a manner that suggests a premature ending of the active reproductive phase. The concurrent influence of dietary phenolic amines on serum T3 and T4, and the relationship of these hormones with expression of seasonal reproduction in domestic and wild ruminants, warrants further analysis of the relationship between dietary phenolic amines, thyroid function, and reproduction in these species.