PSVI-11 Evaluation of the Acid Binding Capacity of Ingredients and Complete Diets Commonly Used for Weanling Pigs

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Abstract The objective of this experiment was to measure acid-binding capacity at a pH of 4 (ABC-4) of common feed ingredients and determine additivity in diets. Ingredient categories included: cereal grains, vegetable proteins, animal proteins and milk, vitamin premixes and minerals, amino acids, and fiber sources. A 0.5 g sample of each ingredient was suspended in 50 mL of distilled deionized water and titrated with 0.1 N hydrochloric acid. Sample ABC-4 was calculated as the amount of acid in milliequivalents (meq) required to reduce and maintain 1 kg of ingredient to a pH of 4 with a smaller number believed to be more advantageous. Cereal grains were found to have decreased ABC-4 compared with other ingredients (Table 1). Vegetable proteins had greater ABC-4 with more variation than cereal grains. Soybean meal (SBM) had an ABC-4 of 602 ± 28.2 meq/kg. Soy protein concentrate (737 ± 165.0 meq/kg) and enzymatically treated soybean meal (ESBM; 753 meq/kg) had greater ABC-4 compared with SBM while fermented soybean meal (FSBM; 207 ± 100.0 meq/kg) was less. Fish meal (1,380 ± 150.9 meq/kg) had greater ABC-4 compared with all analyzed vegetable proteins. Spray dried whey powder and whey permeate had slightly less ABC-4 than that of soybean meal with values of 440 and 520 meq/kg, respectively. Zinc oxide (ZnO) and calcium carbonate (CaCO3) had the greatestt ABC-4 among all ingredients with values of 21,863 ± 598.7 and 18,384 ± 769.7 meq/kg, respectively. Following ingredient analysis, a series of diets were created and analyzed to determine additivity by comparing the differences between calculated and analyzed ABC-4. All analyzed diets had less ABC-4 than calculated values; however, analyzed ABC-4 increased in the same magnitude as the calculated values across diets. The first series of diets were arranged in a 2 × 5 factorial consisting of increasing CaCO3 with or without ZnO. There was a ZnO × CaCO3 interaction (P = 0.020) for difference between calculated and analyzed ABC-4 where differences between calculated and analyzed ABC-4 increased (linear, P < 0.001) as CaCO3 increased in diets without ZnO, but not in diets with ZnO. The second series of diets consisted of different levels of SBM with either FSBM or ESBM included at 5% of the diet. Differences between calculated and analyzed values were not different between treatments (P = 0.640). In conclusion, perfect ABC-4 additivity in complete diets was not realized due to lower analyzed than calculated values; however, analyzed ABC-4 still increased as calculated values increased. These data suggest that diet ABC-4 can be adjusted through selection of ingredients but feeding trials are needed to determine its impact on pig performance.