A total of 300 weanling pigs (241 × 600, DNA, initially, 5.6 ± 0.2 kg) were used to evaluate the effects of altering the acid-binding capacity-4 (ABC-4) of nursery diets with different specialty soybean products and organic acids on performance and fecal dry matter (DM). At weaning, pigs were allotted to 1 of 6 dietary treatments. There were 5 pigs/pen and 10 replications/treatment. Diet 1 was formulated with 12.0% specialty soy protein concentrate (AX3 Digest; Protekta; Newport Beach, CA), 1.06% citric acid, and 0.5% fumaric acid to achieve an ABC-4 of 223 meq/kg. Diets 2 and 3 were the same as diet 1 except citric and fumaric acid were reduced by 50 and 100% to achieve an ABC-4 of 280 or 338 meq/kg, respectively. Diets 4 and 5 were the same as diet 1 except 50 and 100% of the specialty soy protein concentrate was replaced with enzymatically treated soybean meal (HP 300; Hamlet Protein; Findlay, OH) on an SID Lys basis to achieve ABC-4 of 280 and 338 meq/kg, respectively. Diet 6 was a positive control with the same formulation as diet 5 except for the addition of 2,500 mg/kg of Zn from ZnO and a diet ABC-4 of 410 meq/kg. Dietary treatment structure allowed for the comparison of increasing ABC-4 (223 to 338 meq/kg) and formulation method (decreasing acidifier vs. specialty soy protein concentrate replacement) as well as their interactions. Pigs were fed the experimental diet for 24 d postweaning (d 0 to 24) followed by a common diet for an additional 18 d. There were no significant (P > 0.05) ABC-4 method × level interactions throughout the study. From d 0 to 10, increasing ABC-4 decreased (linear, P = 0.042) G:F with no other differences in performance due to ABC-4. Formulation method influenced fecal DM with replacement of specialty soy protein concentrate (diets 4 and 5) reducing (P = 0.038) fecal DM compared with decreasing acidifier level (diets 2 and 3) on d 17. During the experimental period (d 0 to 24), pigs fed the diet with pharmacological Zn from ZnO had increased (P < 0.05) BW, ADG, ADFI, and G:F compared to pigs fed diets without ZnO.
In summary, pharmacological Zn from ZnO improved nursery pig performance when experimental diets were fed. Increasing ABC-4 and the formulation method had minimal effects on nursery pig performance; however, fecal DM was influenced by formulation method. Increasing ABC-4 from 223 to 338 meq/kg may not have been a large enough difference to observe a response to changing ABC-4 of the diet. Further research is warranted to determine the influence of lower ABC-4 levels or other ingredient changes to achieve target ABC-4.
