ABSTRACT:The aim of the study was to compare the effect of selenium (Se) supplementation in organic (lactate-protein complex) or inorganic (sodium selenite) forms on Se concentrations in the blood and organs of goat kids. The experiment involved nineteen male goat kids divided into three groups: C, Se-I, and Se-O. Control group C (n = 5) was without Se supplementation, group Se-I (n = 7) received sodium selenite supplement (0.30 mg Se per animal/day), and group Se-O (n = 7) received lactate-protein selenium complex (0.28 mg Se per animal/day). The supplementation started on the day of weaning and continued for 13 weeks till the day of slaughter. Blood samples for determination of Se concentration and glutathione peroxidase activity were collected on the day of weaning and during weeks 4, 8, and 13 thereafter. Samples of liver tissue, spleen, kidneys, lungs, heart, tongue, diaphragm, shoulder, back, and thigh muscles were taken immediately after slaughter. Significantly higher concentration of Se in group Se-O in comparison with group C was found in thigh muscles (110.4 vs 71.0 µg/kg, P ≤ 0.01), shoulder (105.0 vs 67.2 µg/kg, P ≤ 0.01), back (102.9 vs 61.7 µg/kg, P ≤ 0.01), and heart (180.8 vs 116.7 µg/kg, P ≤ 0.01). Significantly higher concentration of Se in group Se-I in comparison with group C was found in shoulder (83.2 vs 67.2 µg/kg, P ≤ 0.01) and diaphragm (93.6 vs 72.8 µg/kg, P ≤ 0.01). The comparison of the groups Se-I and Se-O showed significantly higher Se concentrations in thigh muscles, heart, back, shoulder, and lungs in group Se-O. Mean Se concentration in tissues of experimental groups was 125.8% in Se-O group and 110.7% in Se-I group in comparison with group C. Our results are suggesting that supplementation of Se in the form of lactate-protein complex is more efficient in comparison with sodium selenite.