Added dietary pyridoxine, but not thiamin, improves weanling pig growth performance

We conducted two trials to determine the effects of added dietary pyridoxin e (vitamin Bs) or thiamin (vitamin B-1) on growth performance of weanling p igs. In Exp. 1, weanling pigs (n = 180, initially 5.55 +/- .84 kg, and 21 /- 2 d of age) were fed either a control diet (no added pyridoxine or thiam in) or the control diet with added thiamin (2.8 or 5.5 mg/kg) from thiamin mononitrate or pyridoxine (3.9 or 7.7 mg/kg) from pyridoxine HCl. These fiv e diets were fed in meal form in two phases (d 0 to 14 and 14 to 35 after w eaning), with identical vitamin concentrations in both phases. From d 0 to 14 after weaning, pigs fed added pyridoxine had increased (quadratic, P < . 05) ADG and ADFI; pigs fed 3.9 mg/kg of added pyridoxine had the greatest i mprovement. From d 14 to 35 and 0 to 35, ADG and ADFI increased (linear P = .06) for pigs fed increasing pyridoxine. Growth performance was not improv ed by added thiamin. Tn Exp. 2, weanling pigs (n = 216, initially 6.08 +/- 1.13 kg, and 21 It 2 d of age) were fed a control diet or the control diet with 1.1, 2.2, 3.3, 4.4, or 5.5 mg/kg of added pyridoxine from pyridoxine H Cl. From d 0 to 14 after weaning, increasing pyridoxine increased (quadrati c, P < .05) ADG and ADFI; pigs fed 3.3 mg/kg of added pyridoxine had the gr eatest ADG and ADFI. Break-point analysis suggested a requirement estimate of 3.3 and 3.0 mg/kg of added pyridoxine to maximize ADC and ADFI, respecti vely. From d 14 to 35 or 0 to 35, increasing pyridoxine had no effect (P > .10) on pig growth performance. These results suggest that adding 3.3 mg/kg of pyridoxine (7.1 to 7.9 mg/kg of total pyridoxine) to diets fed from d 0 to 14 after weaning can improve pig growth performance.