The importance of pyridoxine for the impact of the dietary selenium sources on redox balance, embryo development, and reproductive performance in gilts

• Dietary organic source of Se to gilts maximized Se transfer to 30-d embryos.
• Dietary B6 reduced post-pubertal plasma Se-glutathione peroxidase activity in gilts.
• Dietary Se and B6 did not affect organ and embryo Se-glutathione peroxidase activity.
• Dietary B6 reduced within-litter weight and Se content homogeneity in 30-d embryo.

This study aimed to determine the effects of dietary pyridoxine and selenium (Se) on embryo development, reproductive performance and redox system in gilts. Eighty-four gilts were fed one of five diets: CONT) basal diet; MSeB60) CONT + 0.3 mg/kg of Na-selenite; MSeB610) diet 2 + 10 mg/kg of HCl-pyridoxine; OSeB60) CONT + 0.3 mg/kg of Se-enriched yeast; and OSeB610) diet 4 + 10 mg/kg of HCl-pyridoxine. Blood samples were collected for long-term (each estrus and slaughter) and peri-estrus (fourth estrus d −4 to d +3) profiles. At slaughter (gestation d 30), organs and embryos were collected. For long-term and peri-estrus profiles, Se level and source affected (P < 0.01) blood Se concentration whereas B6 level increased (P < 0.01) erythrocyte pyridoxal-5-phosphate concentration. A B6 level (P < 0.05) effect was observed on long-term plasma Se-dependent glutathione peroxidase (Se-GPX) activity whereas peri-estrus Se-GPX was minimum on d −1 (P < 0.01). Selenium level increased sows’ organs and embryo Se concentration (P < 0.01). Selenium source tended to enhance embryo Se content (P = 0.06). Within-litter embryo Se content was increased by B6 level (P < 0.01). Selenium level tended to affect Se-GPX and total GPX activities in organs mitochondria (P = 0.09 and 0.07, respectively). Selenium source affected kidney ATP synthesis (P = 0.05). In conclusion, B6 level affected the Se-GPX activity on a long-term basis, whereas the basal level of Se was adequate during the peri-estrus period. Embryo quality was not improved by dietary Se, and B6 impaired within-litter homogeneity.