Performance Response of Piglets to Acid-Preserved High Moisture Wheat or Barley As an Alternative to in-Feed Acidification.

Two experiments were conducted to compare the effectiveness of acidified high moisture wheat or barley in the diet of weanling pigs as an alternative to in-feed acidification. Wheat or barley were stored for 34 or 38 days, respectively, following reconstitution to 20% moisture and the addition of the appropriate acid (propionic acid or a commercial acidifier with 30-50% phosphoric acid). Weight loss of galvanized and carbon steel coupons, embedded in the acidified grain, were used to estimate corrosion rate. Trial 1 (wheat) and trial 2 (barley) used 160 and 90 pigs respectively (weaned at 21±2 days, 6.50 to 6.70 kg BW, housed 4 pigs/pen). Pigs were fed stage 1 and 2 treatment diets from day 0 to 7, and 8 to 21 respectively, and a common commercial diet from day 22 to 35. The treatments in trial 1, arranged as a 2x2 factorial, were type of acid (propionic or phosphoric) and application method (wheat preservation or diet supplementation) plus a negative control (5 treatments). The 3 treatments in trial 2 were phosphoric acid applied either as barley preservation or diet supplementation, plus a negative control. Mold was observed on phosphoric acid-preserved wheat and barley (7,000 and 820,000 cfu/gram respectively), however, mycotoxin levels were below acceptable limits. During storage, the pH of phosphoric acid-preserved wheat and barley increased from 4.27 to 5.72 and 4.60 to 5.47 respectively, while the pH of propionic acid-preserved wheat increased from 4.56 to 4.85. In trial 1, treatment had no effect on ADG or ADFI (P>0.05) but G:F (0.78 negative control vs 0.84 propionic acid) was improved in stage 2 in pigs fed diets with propionic acid, regardless of application method (P<0.05). Treatment had no effect on ADG, ADFI or G:F in trial 2 (P>0.05). Corrosion rate was higher with propionic than phosphoric acid on carbon steel but not galvanized steel (acid x coupon interaction, P<0.05). Regardless of acid, a higher corrosion rate was observed on galvanized steel than carbon steel (P <0.05). In conclusion, propionic acid addition to weanling pig diets improved G:F and wheat preserved with propionic acid provided comparable feed efficiency benefits to diet supplementation with the acid. Phosphoric acid in wheat or barley-based diets did not affect piglet performance and requires further investigation as a grain preservative. Furthermore, a higher corrosion rate can be expected if propionic acid preserved grains are stored in bins made of galvanized steel.