Some aspects of the pyridoxine (vitamin B6) requirement in weanling piglets.

Four trials were carried out to determine the optimal level of dietary pyridoxine (vitamin B6) and its interaction with riboflavin (vitamin B2) in early-weaned piglets. In Trial 1, twelve piglets were tube-fed graded supplements of B6, 0, 10, 50 or 100 mg/kg. The level of 50 mg/kg maximized B6 in red blood cells (P<0.05). In Trial 2, thirty-six piglets were tube-fed with four combinations of B6 (0 v. 50 mg/kg) and B2 (0 v. 25 mg/kg). The B6 supplement increased (P<0.01) B6 in red blood cells. C-peptide and insulin responses to intravenous glucose tended (P<0.08) to or decreased (P<0.03) with B2 while no effect was observed on glucose. After gastro-enteral glucose, dietary B2 depressed C-peptide and insulin responses in B6-unsupplemented piglets and increased them in B6-supplemented piglets (P<0.03). The glucose response tended to be higher in B6-supplemented piglets (P<0.06). Trials 3 and 4 were carried out in commercial conditions using either B6 and/or B2 supplements given during 2 weeks after weaning (Trial 3) or a B6 supplement alone (50 mg/kg) given between 2 (weaning) and 10 weeks of age. Despite a marked and persistent increase (P<0.01) of B6 in red blood cells in B6-supplemented piglets, the effect on growth performance was either none (P>0.39; Trial 3) or marginally lower (<-2 %; P<0.03; Trial 4). In conclusion, it appears that a dietary supplement of 50 mg/kg B6 saturated the red blood cell pool in B6 and influenced, along with B2, the glucose homeostasis through the entero-insular axis. Nevertheless, such metabolic effects are not reflected on growth performance.