Effects of added folic acid on growth performance, short chain fatty acid concentrations, and serum homocysteine concentrations in nursery pigs

Abstract Recent research reported an increase in growth performance when feeding supra-nutritional (up to 18 mg/kg) levels of folic acid to weanling pigs. Therefore, two experiments were conducted to validate these responses in typical U.S. nursery pig diets. In Exp. 1, 360 barrows (5.5 ± 0.03 kg) were used in a 38-d study to evaluate the effects of added folic acid (Rovimix Folic Acid, dsm-firmenich, Plainsboro, NJ) with or without pharmacological levels of Zn on growth performance and fecal dry matter (DM). Treatments were arranged in a 3 × 2 factorial with main effects of folic acid (0, 20, or 40 mg/kg) and Zn (3000 mg/kg of Zn in phase 1 and 2000 mg/kg in phase 2 or no Zn other than 110 mg/kg from the trace mineral premix). Diets were corn-soybean meal-based and fed in 2 phases (phase 1 from d 0 to 9 and phase 2 from d 9 to 24). Overall (d 0 to 38), increasing folic acid decreased (quadratic, P ≤ 0.003), average daily gain (ADG), and average daily feed intake (ADFI) with pigs fed 20 mg/kg having the lowest performance. From d 0 to 24, pigs fed diets with pharmacological levels of Zn had increased (P ≤ 0.030) ADG, and ADFI compared to pigs fed 110 mg/kg added Zn; however, no differences were observed in overall performance. Fecal DM was greater (P = 0.007) on d 24 compared to d 9. A trend was observed where pigs fed diets with added Zn had increased (P = 0.080) fecal DM averaged across d 9 and 24. Fecal total short chain fatty acid concentrations were greater (P = 0.053) on d 24 compared to d 9. Isobutyrate increased (linear, P = 0.030) as folic acid increased; however, most samples had nondetectable levels. In Exp. 2, 350 barrows (initially 6.0 ± 0.06 kg) were fed corn-soybean meal-based diets, fed in 3 phases (phase 1 from d 0 to 10, phase 2 from d 10 to 23 and phase 3 from d 23 to 38), and consisted of increasing folic acid: 0, 5, 10, 20, or 40 mg/kg. Overall, ADG, ADFI, and G: F were reduced (quadratic, P ≤ 0.049) as folic acid increased with the poorest performance observed when pigs were fed 20 mg/kg of folic acid. On d 10 and 23, blood samples were collected from 70 pigs to determine serum homocysteine concentration Homocysteine concentrations increased (linear, P = 0.037) with increasing folic acid on d 10; however, no differences were observed on d 23 (folic acid × d interaction, P = 0.069). In conclusion, added folic acid reduced growth performance with pigs fed 20 mg/kg having the poorest performance, and increased serum homocysteine concentrations.