Effects of Dietary Acid-binding Capacity at pH 4 on Growth Performance and Fecal Parameters of Weaned Piglets

Abstract A total of 1,102 underweight weaned piglets (initial BW = 5.73 ± 0.7 kg; 24 d of age, DanBred × Pietrain) were used to evaluate the effect of dietary acid-binding capacity at pH 4 (ABC-4) on growth performance and fecal characteristics during the post-weaning period in diets supplemented with a potentiated ZnO source (pZnO). Piglets were allotted to 48 pens based on sex (24 pens per sex) and body weight, with 12 pens per treatment. Diets were formulated to provide increasing ABC-4 values using different inclusion rates of buffering ingredients, resulting in four dietary treatments: Low (180/220 mEq/kg), Medium (253/280 mEq/kg), Medium-High (327/340 mEq/kg), and High (400/400 mEq/kg) for phases 1 (d 0–14) and 2 (d 15–28), respectively. All diets contained 100 mg Zn/kg from pZnO (HiZox®, Animine, France), to support intestinal integrity and help control bacterial proliferation typically associated with post-weaning pathogenic challenge. Animals had ad libitum access to feed and water throughout the trial. Average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were measured by phase and overall (d 0–28). Fecal scores, fecal dry matter (DM), pH, and total enterobacteria were monitored to assess gut health. In the pre-starter phase, no significant differences were observed among treatments for ADG, ADFI, or FCR, although there was tendency on improving ADG and FCR at lower ABC-4 levels (P = 0.07). During the starter phase (d 15–28), piglets fed diets with lower levels ABC-4 had higher ADG and ADFI compared to piglets fed diet with High ABC-4. Moreover, increasing ABC-4 values resulted in a linear decrease (P 0.0001) in ADG. For the overall trial, ADG decreased linearly (P 0.001) as ABC-4 increased, reflecting reduced intake (P 0.001). Fecal parameters reflected similar trends. From d 15 to 28 (Phase 2), fecal score and diarrhea frequency increased linearly (P 0.05) with higher ABC-4 values, with pigs fed the highest ABC-4 diet (400 mEq/kg) exhibiting the greatest incidence of diarrhea (score ≥3). Fecal pH increased linearly (P 0.05) with increasing ABC-4 on d 12, suggesting reduced fermentation activity. Total enterobacteria counts showed a tendency (P = 0.065) to increase linearly with higher ABC-4 levels at the end of phase 2, indicating potential microbial imbalance. In conclusion, increasing dietary ABC-4 impaired growth performance and increased fecal looseness and enterobacteria counts, while lowering ABC-4 (180–250 mEq/kg) improved ADG and intestinal stability. These results highlight the importance of controlling dietary buffering capacity and including effective Zn sources in post-weaning diets to support piglet health and performance.