The effect of benzoic acid with or without a direct-fed microbial on the nutrient metabolism and gas emissions of growing pigs.

Twenty-four gilts (PIC 337 × 1050, PIC Genus, Hendersonville, TN) with an initial body weight (BW) of 33.09 ± 1.33 kg were used to investigate the effects of benzoic acid (BA) and a Bacillus-based direct-fed microbial (DFM) on the nutrient metabolism and manure gas emissions of growing pigs. Pigs were blocked by BW, placed into metabolism stalls, and randomly assigned to one of four dietary treatments: basal control (PC), low nitrogen (NC), PC plus 0.3% BA (PC+BA; VevoVitall, DSM Nutritional Products), and PC plus 0.3% BA and 0.025% DFM (PC+BA+DFM; PureGro, DSM Nutritional Products). Pigs were fed a common diet from day 0 to 14, and the experimental diets were fed in two phases (day 14 to 28 and day 28 to 53). The experiment consisted of four collection periods, with each period subdivided into two subperiods to collect samples for gas emissions and nutrient balance. Firstly, manure samples were collected for 72 h. Twice daily, urine and feces were weighed, and urine pH was measured. After each period, manure was subsampled and taken to the lab to measure gas emissions. Secondly, urine and feces were quantitatively collected for 96 h to allow for measurement of nutrient digestibility (ATTD) and retention. Data were analyzed as repeated measures in SAS 9.4 (SAS Inst., Cary, NC) with fixed effects of treatment, collection period, and block. Pig was the experimental unit, and results were considered significant at P ≤ 0.05 and a tendency at 0.05 < P ≤ 0.10. Pigs fed PC+BA had the greatest ADG compared to pigs fed NC (P = 0.016), with intermediate ADG for pigs fed PC or PC+BA+DFM (P ≥ 0.148). The ATTD of dry matter, gross energy, P, and N did not differ between treatments (P ≥ 0.093). However, the ATTD of Ca was reduced in pigs fed PC+BA+DFM compared to pigs fed PC+BA (P = 0.012). Pigs fed PC+BA or NC excreted less urinary N compared to PC and PC+BA+DFM (P ≤ 0.034), which contributed to greater nitrogen retention in PC+BA compared to PC (P = 0.016). Furthermore, decreased manure pH from pigs fed PC+BA or NC resulted in lower ammonia (NH3) emissions compared to pigs fed PC+BA+DFM or PC. There was no effect of dietary treatment on manure hydrogen sulfide, methane, or carbon dioxide emissions. In conclusion, supplementing 0.3% BA improved N retention and reduced manure pH and NH3 emissions, similar to feeding pigs low N, but improved the ADG of pigs when compared to feeding a low N diet.

Diet formulation as a strategy to improve economic and nutritional efficiency may be combined with nonnutritive feed additives, such as organic acids, specifically benzoic acid, and direct-fed microbials, to further improve nutrient utilization in pigs. Therefore, the objective of this trial was to investigate the effect of supplementing benzoic acid with or without a direct-fed microbial on the nutrient metabolism and emissions of ammonia, hydrogen sulfide, carbon dioxide, and methane from the manure of growing pigs. Feeding a diet containing 0.3% benzoic acid did not affect nutrient digestibility but reduced urinary nitrogen excretion, which resulted in improved nitrogen retention compared to the basal diet. Furthermore, benzoic acid reduced urine and manure pH, contributing to reduced manure ammonia emissions. However, supplementing the direct-fed microbial alongside benzoic acid attenuated these effects.

Field sampling method for quantifying odorants in humid environments.

Most air quality studies in agricultural environments use thermal desorption analysis for quantifying semivolatile organic compounds (SVOCs) associated with odor. The objective of this study was to develop a robust sampling technique for measuring SVOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 +/- 1.5 degrees C) and 25, 50, and 80% relative humidity (RH). Sorbent material used included Tenax, graphitized carbon, and carbon molecular sieve (CMS). Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80% RH dueto excessive sorption of water. Heating of CMS tubes during sampling or dry-purging of CMS tubes post sampling effectively reduced water sorption with heating of tubes being preferred due to the higher recovery and reproducibility. Tenaxtubes had breakthrough of the more volatile compounds and tended to form artifacts with increasing volumes of air sampled. Graphitized carbon sorbent tubes containing Carbopack X and Carbopack C performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. The graphitized carbon tubes were taken to the field for further testing. Field samples taken from inside swine feeding operations showed that butanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole were the compounds detected most often above their odor threshold values. Field samples taken from a poultry facility demonstrated that butanoic acid, 3-methylbutanoic acid, and 4-methylphenol were the compounds above their odor threshold values detected most often, relative humidity, CAFO, VOC, SVOC, thermal desorption, swine, poultry, air quality, odor.