Effects of diet supplementation with sodium selenite and selenium-enriched in puppies’ health performance from post-weaning to adulthood

Selenium is an essential trace element for puppies and adult dogs and dietary supplementation is a common practice to ensure animal requirements. This study aimed to compare the efficacy of two selenium sources for supplementation of complete dry dog foods, offered to puppies from 12 to 52 weeks of age. The study followed a complete randomized block design in which, 12 Beagles (6 males and 6 females) were randomly assigned to one of two diets consisting of similar pet food formulas supplemented with the same concentration (≈ 100 μg/kg) of organic selenium from Saccharomyces cerevisiae (SeOrg) and sodium selenite (SeInorg). Samples were collected at several time points (e.g., 12, 16, 20, 24, 28, 36, 44, and 52 weeks of age) to evaluate the effects of supplemental selenium source on feed intake, diet digestibility, weight gain, haematology, serum chemistry, selenium biomarkers, and coat quality. Data were analysed using a mixed model with repeated measurements, including selenium source, sex, age, and selenium source × age (when significant) as fixed effects, and block as random effect. Nutrient and energy intakes were higher in puppies fed SeInorg (P < 0.05). Digestibility of crude protein and neutral detergent fibre was higher for SeInorg (P < 0.05), whereas the digestibility of ether extract was lower (P = 0.038). Diet SeOrg promoted higher weight gain (P = 0.028). Plasma concentration of selenium was similar using both forms of selenium (P > 0.05). Glutathione peroxidase activity tended to be higher with SeInorg (P = 0.088). The digestibility of selenium was not significantly affected by the supplemental source. Moreover, urinary content and fractional clearance of selenium were higher in puppies fed SeInorg (P < 0.05), suggesting greater retention of the organic source. Despite the lack of effect of selenium source on serum thyroid hormones, free thyroxine triiodothyronine ratio was lower in the SeOrg group (P < 0.001), which suggests high metabolic rates. Coat quality and hair growth were not affected by the selenium source (P > 0.05). Overall, data indicate better retention of organic selenium with potential less waste and highlight the need for further research to fully assess the biological benefits of organic over inorganic supplemental selenium sources.