The purpose of this study was to estimate the effect of supplementation of a functional additive during the last third of gestation in cows on the level of IgG in colostrum. Twenty-eight (28) Holstein and White Orejinegro (WON) cows were assigned to a randomized complete block design with 2 factors (breed and supplementation) with repeated measures (i.e., days of lactation). The supplementation factor included 3 treatments: CTL) Control without supplementation, S0) Supplement without additive, S1) Supplement with additive. Colostrum samples were obtained during the first 3 d of lactation for the determination of crude protein (CP), immunoglobulin G (IgG) and Brix grades. A correlation analysis between Brix grades an IgG was performed. Concentrations of IgG determined by the ELISA technique were strongly correlated with the percentages of Brix grades (n = 82, r = 0.954, P < 0.0001), indicating that it can be used as an estimate of the concentration of IgG. The concentration of crude protein in colostrum was affected by the breed × day interaction (P < 0.05), it was lower in WON cows (10.3%) than Holstein cows (11.5%) on d 1, whereas on d 2 and 3 WON cows had greater concentrations of protein (5.9% and 6.5%, respectively) compared with Holstein cows (4.8% and 4.1%, respectively). There was a breed × day × supplementation interaction on colostral IgG (P < 0.05). On d 1, S1 cows of both Holstein (55.1 mg/mL) and WON breeds (47.3 mg/mL) had greater concentrations of colostral IgG than CTL Holstein (44.4 mg/mL) and WON (32.5 mg/mL) cows. The decrease in colostral IgG from d 1 to d 3 was greater in Holstein (95%) than in WON (86%) cows. It can be concluded that dietary supplementation with functional additives increased the colostral concentration of IgG in both cow breeds.