227 Varying the Acid Biding Capacity of High and ZnO-Free Diets Influences Weanling Pig Growth Performance

Abstract Altering the acid binding capacity to pH4 (ABC-4) of the weanling pig diet can influence stomach pH, thereby aiding in protein digestion and improving feed efficiency. Two studies examined the effect of ABC-4 level in diets of either high ZnO or without ZnO on the growth performance of nursery pigs. Both trials were randomized complete block designs, where body weight (BW), average daily gain (ADG), average daily feed intake (ADFI), and gain to feed (G:F) were measured. Data were analyzed using pen and pig as experimental units for the first and second study, respectively. In the first study, weanling pigs (n = 1,152) were allocated to 4 dietary treatments with 18 replicate pens per treatment. Treatments were applied in phase 1 (1-10 d) and 2 (11-21 d), and pigs received a common phase 3 (22-42 d) diet. All diets contained high ZnO (2,500ppm and 1,500ppm phase 1 and 2, respectively). The control diet (CON) had no acidifiers resulting in 400 mEq ABC-4/kg, and treatments ranged from 360 to 300 mEq/kg using Ca formate and formic acid alone or in combination. In the first week, G:F of pigs fed the test diets was greater than in the CON diet (+0.09-0.15 g/g, P < 0.05). In phase 2, pigs fed diets containing formic acid (300 mEq ABC-4/kg) had reduced ADFI (-15 g/d from CON, P < 0.05). Conversely, pigs fed Ca formate and formic acid (300 mEq ABC-4) had greater ADFI (+16 g/d, P < 0.05) and a tendency for greater G:F than CON (+0.02, P < 0.10). Pigs fed a diet containing Ca formate only (360 mEq ABC-4/kg) had a greater G:F (+0.03, P < 0.05) yet comparable feed intake to CON. In the second 42-day study, weanling pigs (n = 120) housed in pens with individual electronic feeding stations (10 pigs/pen), were randomized to 6 ZnO-free treatments, totaling 20 replicate pigs per treatment. The ABC-4 was linearly reduced from 450 to 200 mEq/kg using fumaric acid and shifting Ca sources from Ca carbonate to monocalcium phosphate and monodicalcium phosphate. In phase 1 (0-15d), pigs had greatest ADFI (P < 0.05) and G:F (P < 0.05) at 300 and 350 mEq ABC-4/kg, respectively, and east ADFI at 200 mEq ABC-4/kg (greatest fumaric acid inclusion) and 450 mEq ABC-4/kg (no acidifier). Overall, pigs fed the 300 mEq ABC-4/kg diet had the greatest (P < 0.05) BW, ADG, and ADFI while pigs fed the 350 mEq ABC-4/kg diet had the greatest G:F. Pigs fed the 450 mEq ABC-4/kg diet had the lowest BW, ADG, ADFI, and G:F. In conclusion, reducing the ABC-4 of ZnO and ZnO-free diets using a comb