Effects of Long-Term Zinc Deficiency on Feed Utilization, Reproductive Characteristics, and Hair Growth in Sexually Mature Male Goats

In this study, 10 sexually mature male goats were fed a zinc-deficient diet, while 5 received a control diet with adequate zinc for 20 weeks. The zinc-deficient goats showed symptoms of zinc deficiency, including lower plasma zinc levels, reduced hair growth and zinc content in hair, smaller testicles, and decreased libido compared to controls. Despite increased feed intake from weeks 10 to 18, the body weight of zinc-deficient goats remained unchanged. Testicle biopsies revealed that spermatogenesis was not severely affected until 4 weeks post-treatment, with only spermatogonia present and reduced tubular size. Both zinc-deficient and control goats experienced high mortality rates, with 80% and 60% dying, respectively. After the treatment period, goats previously on the deficient diet did not show a significant increase in feed intake when switched to the control diet, indicating that the adaptation to zinc deficiency was not easily reversible.