The effects of potassium diformate and its molecular constituents on the apparent ileal and fecal digestibility and retention of nutrients in growing-finishing pigs

Abstract

Five 43-kg barrows [(Dutch Landrace x Yorkshire) x Yorkshire] were fitted with steered ileocecal valve cannulas to compare the effects of K-diformate (KDF), a specifically conjugated salt vs its molecular constituents, namely, formic acid and K-formate, as acidifiers in lysine-deficient diets on the apparent ileal (ID) and fecal digestibility, retention of nutrients, and manure production. The animals were randomly assigned to five dietary treatments according to a 5 x 5 Latin square design as follows: 1) control-no acidifier; 2) 1% KDF (= 0.65% K-formate + 0.35% formic acid, or 0.7% [HCOO-] + 0.3% [K+]); 3) 0.65% K-formate (= 0.35% [HCOO-] + 0.3% [K+]); 4) 0.35% formic acid (= 0.35% [HCOO-]); and 5) 1.3% K-formate (= 0.7% [HCOO-] + 0.6% [K+]). Diets were formulated with barley, wheat, soybean meal, and canola meal as major ingredients, and provided all nutrients at adequate levels, except for lysine (24% less than estimated requirement). Feeding level was equal to 2.5 x maintenance requirement (MR) for ME (MR = 418 kJ ME x BW(-0.75)), and daily rations were given in two portions after mixing with water in a ratio of 1:2.5. Chromic oxide was used as an indigestible marker. No clinical health problems due to the dietary treatments were observed. Irrespective of the additive, there were no differences (P < or = 0.10) in the ID of DM, OM, CP, or essential amino acids compared to the control, except for phenylalanine (P < or = 0.05). Among nonessential AA, only the ID of tyrosine tended (P = 0.092) to increase (up to 3.9 percentage units). The fecal digestibility of ash and K were greater (P < or = 0.001) in pigs fed supplemental K, irrespective of its source. The greater intake and fecal digestibility of K corresponded with greater (P < or = 0.05) losses of K in urine. Body retention of N, Ca, total P, and K was similar (P > or = 0.10) among treatments. As estimated from a separate nonorthogonal analysis, supplemental K improved (P < or = 0.05) body N by 3.7 percentage units compared to the control. The results of this study do not provide a clear explanation for the improved growth performance reported previously with KDF and its molecular constituents, and further research on their in vivo mode of action will require methodological refinement, especially with regard to the efficiency of AA utilization.