136 Effects of acid-binding capacity in low-zinc diets on growth performance of weaned pigs

Abstract Post-weaning diarrhea (PWD) of piglets remains a concern in the pork industry. Historically, PWD has been controlled with dietary solutions such as antibiotics as growth promotors and high dietary inclusion of ZnO. However, such use of antibiotics is not permitted any longer and such use of ZnO has already been banned in the EU. In the present trial, the objective was to study the effects on growth performance of acid binding capacity (ABC) as dietary solution in low zinc diets compared to control diet with high zinc. In total, 1,445 pigs (Camborough F1 female x 800 boar line; PIC Canada) were weaned at 20 ± 1 d of age, comprising of equal number of gilts and barrows, and were randomly placed into one of 50 mixed-gender pens (50% barrows and 50% gilts) in two rooms filled four d apart, for 28 or 29 pigs per pen. In total, five dietary regimes were tested during Phase 1 (d 0-7) and 2 (d 7-21): one high in Zn (2,000-3,000 ppm ZnO; 412 mEq/kg ABC-4) and 4 low in Zn (150 ppm) with incremental reductions in ABC-4 from 326 to 150 mEq/kg. Reductions in ABC-4 were accomplished using a combination of changes; added organic acids (formic, fumaric, benzoic), Ca formate to replace limestone, and a low ABC-4 soy protein concentrate to replace regular soy protein concentrate. Pigs were fed a common diet during Phase 3 (d 21-42). For each feeding phase all diets were formulated to equal net energy and standardized ileal digestible amino acids and contained phytase. At d 21, pigs fed high Zn were 1.6 kg heavier (11.3 vs 9.7 kg; P 0.01) than pigs fed low Zn with greatest ABC-4. Within low Zn diets, reducing ABC-4 linearly increased body weight (BW; 9.7 vs. 10.1 kg). These differences continued until d 42: pigs fed high Zn were 1.8 kg heavier (24.1 vs 22.3 kg; P 0.01) than pigs fed low Zn with greatest ABC-4). Within low Zn diets, reducing ABC-4 for the first 3 wk after weaning linearly increased BW (22.9 vs. 22.3 kg; P 0.01). This increased growth was caused by a combination of increased (P 0.01) feed intake and increased (P 0.05) gain-to-feed and coincided with reduced (P 0.01) incidence of scours. In conclusion, weaned pigs fed high Zn diets grew more than pigs fed low Zn diets. Dietary ABC-4 is a dietary solution to consider for ameliorating the reduced growth by pigs fed low Zn diets: 33% of the reduced growth could be compensated for by feeding diets low in dietary ABC-4 during the first 3 wk after weaning.