The Effect of Feeding 0.3% Benzoic Acid to Growing Pigs, Alone or in Combination with a Direct-Fed Microbial, on Nutrient Metabolism and Manure Composition and Emissions Compared with a Low Protein Diet

Abstract Twenty-four gilts (PIC 337X1050, PIC Genus, Hendersonville, TN) with initial bodyweight (BW) 33.09±1.33kg were used to investigate the effects of benzoic acid (BA), with or without a Bacillus-based direct-fed microbial (DFM), on the nutrient metabolism and gas emissions of growing pigs. Pigs were blocked by BW, placed into metabolism stalls, and randomly assigned to 1 of 4 dietary treatments: control (PC), low nitrogen (NC), PC plus 0.3% BA (VevoVitall, DSM Nutritional Products), and PC plus 0.3% BA and 0.025% DFM (PureGro, DSM Nutritional Products). The 54-d experiment consisted of 4 collection periods, with each period subdivided into 2 sub-periods to measure manure gas emissions and nutrient balance and digestibility. Gas emissions sub-periods lasted 72h. Twice daily, urine and feces were weighed, and urine pH was measured. Urine and feces were stored together and, after 5 d of storage, manure was subsampled and taken to the lab for gas emissions measurements. Urine and feces were quantitatively collected for 96h to measure nutrient digestibility (ATTD), excretion, and retention. Data were analyzed as repeated measures in SAS. Pig was the experimental unit, and results were significant at P ≤ 0.05. Pigs fed BA had greater ADG (922g/d) than pigs fed NC (849g/d), with intermediate ADG for PC (882g/d) or BA+DFM (906g/d). The ATTD of DM, GE, and CP was similar among treatments; however, pigs fed BA or NC excreted less nitrogen in urine than PC and BA+DFM, resulting in greater nitrogen retention in BA compared with PC. Decreased manure pH from pigs fed BA or NC resulted in lower NH3emissions compared with BA+DFM or PC. Manure H2S, CH4, and CO2 emissions were similar among treatments. In conclusion, BA improved nitrogen retention and reduced manure pH and ammonia emissions similarly to feeding low crude protein but improved ADG when compared with a low crude protein diet.