Zinc (Zn) is an essential trace element, and its deficiency causes defects in the response of the immune system, affecting the synthesis and secretion of γ-globulins. In this study, we evaluated serum Zn levels in race foals of different age categories to establish the relationship between subnormal values of Zn and decreased levels of γ-globulins. Decreased γ-globulin levels were accompanied by total protein and albumin serum levels that were within the normal range for the species. Serum Zn was measured in 304 foals (aged between 8 and 24 months), which were classified into three categories (weaning, yearling, and 2 years). The albumin/globulin ratio was 1.28 ± 0.2964 in the normal Zn group and 2.185 ± 0.818 (P < .001) in the low Zn group. Hypogammaglobulinemia was found to be more frequent in the yearling and in the 2-year-old category animals (P < .001 low Zn vs. normal Zn).