Swine diets impact manure characteristics and gas emissions: Part II sulfur source

Minimum carbon dioxide is a key predictor of the respiratory health of pigs in climate-controlled housing systems

BACKGROUND

Respiratory disease is an economically important disease in the swine industry. Housing air quality control is crucial for maintaining the respiratory health of pigs. However, maintaining air quality is a limitation of current housing systems. This study evaluated the growth and health parameters of pigs raised under different environmental conditions and identified key environmental variables that determine respiratory health. Eighty (Largewhite × Landrace) × Duroc crossed growing pigs (31.71 ± 0.53 kg) were equally distributed into two identical climate-controlled houses with distinct environmental conditions (CON = normal conditions and TRT = poor conditions). Two-sample tests were performed to compare the means of the groups, and a random forest algorithm was used to identify the importance scores of the environmental variables to respiratory health.

RESULTS

Pigs in the TRT group were significantly exposed to high temperatures (28.44 vs 22.78 °C, p < 0.001), humidity (88.27 vs 61.86%, p < 0.001), CO2 (2,739.93 vs 847.91 ppm, p < 0.001), NH3 (20.53 vs 8.18 ppm, p < 0.001), and H2S (14.28 vs 6.70 ppm, p < 0.001). Chronic exposure to these factors significantly reduced daily feed intake (1.82 vs 2.32 kg, p = 0.002), resulting in a significant reduction in average daily gain (0.72 vs 0.92 kg, p = 0.026), increased oxidative stress index (3.24 vs 1.43, p = 0.001), reduced cortisol levels (2.23 vs 4.07 mmol/L, p = 0.034), and deteriorated respiratory health status (74.41 vs 97.55, p < 0.001). Furthermore, a random forest model identified Min CO2, Min NH3, and Avg CO2 as the best predictors of respiratory health, and CO2 was strongly correlated with NH3 and H2S concentrations.

CONCLUSIONS

These findings emphasize the critical importance of proper environmental management in pig farming and suggest that regular monitoring and control of either CO2 or NH3, facilitated by environmental sensors and integration into intelligent systems, can serve as an effective strategy for improving respiratory health management in pigs.

Effects of atmospheric and manure surface conditions on H2 S emissions from an in-ground finisher hog manure slurry tank

Hydrogen sulfide (H2 S) emitted by livestock operations can be detrimental to human health. The storage of hog manure is a significant agricultural source of H2 S emissions. H2 S emissions from a ground-level Midwestern hog finisher manure tank were measured for 8-20 days each quarter over a 15-month period. After excluding 4 days with outlier emissions the mean daily emission was 1.89 g H2 S m-2 day-1 . Mean daily emission was 1.39 g H2 S m-2 day-1 when the slurry surface was liquid and 3.00 g H2 S m-2 day-1 when crusted. Emissions however were not significantly different whether the surface was liquid or crusted when differences in temperature were considered. Diurnal variation in emissions was not correlated with air temperature, water vapor saturation deficit, or wind speed when the manure surface was crusted but was positively correlated with these variables when the surface was not crusted. Daily H2 S emissions were modeled according to two-film theory incorporating resistance approach with limited success. Additional emissions measurements with greater documentation of the manure liquid composition and crust characteristics are needed to assess the component transport resistances in the emissions model.

Arazyme in combination with dietary carbohydrolases influences odor emission and gut microbiome in growing-finishing pigs

This study evaluated the effects of supplementing feed with arazyme and dietary carbohydrolases derived from invertebrate gut-associated symbionts on the noxious gas emissions, gut microbiota, and host-microbiome interactions of pigs. Here, 270 and 260 growing pigs were assigned to control and treatment groups, respectively. The tested feed additives contained a mixture of arazyme (2,500,000 Unit/kg) and synergetic enzymes, xylanase (200,000 Unit/kg) and mannanase (200,000 Unit/kg), derived from insect gut-associated symbionts in a 7.5:1:1 ratio. The control group was fed a basal diet and the treatment group was fed the basal diet supplemented with 0.1 % enzyme mixture (v/v) for 2 months. Odorous gases were monitored in ventilated air from tested houses. Fecal samples were collected from steel plate under the cage at the completion of the experiment to determine chemical composition, odor emissions, and bacterial communities. There was a significant decrease in the concentration of NH₃ (22.5 vs. 11.2 ppm; P < 0.05), H₂S (7.35 vs. 3.74 ppm; P < 0.05), trimethylamine (TMA) (0.066 vs. 0.001 ppm; P < 0.05), and p-cresol (0.004 ppm vs. 0 ppm; P < 0.05) at 56 d in treatment group compared with the control group. Moreover, fecal analysis results showed that exogenous enzyme supplementation caused a reduction in VFAs and indole content with approximately >60 % and 72.7 %, respectively. The result of gas emission analysis showed that NH₃ (9.9 vs. 5.3 ppm; P < 0.05) and H₂S (5.8 vs. 4.1 ppm; P < 0.05) were significantly reduced in the treatment group compared to the control group. The gut microbiota of the treatment group differed significantly from that of the control group, and the treatment group altered predicted metabolic pathways, including sulfur and nitrogen related metabolism, urea degradation. The results demonstrated that supplementing feed with arazyme with dietary carbohydrolases effectively controls noxious gas emissions and improves health and meat quality of pigs.

Emissions of H2S from Hog Finisher Farm Anaerobic Manure Treatment Lagoons: Physical, Chemical and Biological Influence

Hydrogen sulfide (H2S) from hog operations contributes to noxious odors in the surrounding environment and can be life-threatening. There is, however, limited understanding of what influences H2S emissions from these farms. Emissions of H2S were measured periodically over the course of two years at hog finisher farms in humid mesothermal (North Carolina, NC, USA) and semi-arid (Oklahoma, OK, USA) climates. Emissions were determined using an inverse dispersion backward Lagrangian stochastic model in conjunction with line-sampled H2S concentrations and measured turbulence. Daily emissions at the two lagoons were characterized by low emissions on most days with occasional days of high emissions. Mean annual area-specific emissions were much lower for the NC lagoon (1.32 µg H2S m−2 s−1 ± 0.07 µg H2S m−2 s−1) than the OK lagoon (6.88 µg H2S m−2 s−1 ± 0.13 µg H2S m−2 s−1). Mean annual hog-specific emissions for the NC lagoon were 0.75 g H2S hd−1 d−1 while those for the OK lagoon were 1.92 g H2S hd−1 d−1. Emissions tended to be higher during the afternoon, likely due to higher mean winds. Daily H2S emissions from both lagoons were greatest during the first half of the year and decreased as the year progressed and a reddish color (indicating high populations of purple sulfur bacteria (PSB)) appeared in the lagoon. The generally low emissions at the NC lagoon and higher emissions at the OK lagoon were likely a result of the influence of wind on mixing the lagoon and not the presence of PSB.

Swine diets impact manure characteristics and gas emissions: Part I protein level

Crude protein (CP) is a key nutrient in swine diets supplying essential amino acids, N, and S to animals for growth are fed in excess to maximize growth. Swine diets reduced in CP and supplemented with crystalline amino acids have been shown effective at maintaining animal growth while increasing overall CP use efficiency. A feeding trial study was conducted to determine the effects of reduced dietary CP levels on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 111 kg BW were fed corn and soybean meal diets formulated with 8.7, 14.8, and 17.6% CP using crystalline amino acid supplementation in the 8.7 and 14.8% CP diets, but only intact protein, soybean meal, in the diet containing 17.6% CP. Diets were fed for 45 d with an average daily feed intake (ADFI) of 2.70 kg across all diets. Animals were fed twice daily with both feces and urine collected during each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary CP levels increased manure pH, total solids, total N, and total S, including increased levels of ammonia (NH₃), volatile fatty acids, and phenolic compounds. Pigs fed lower CP diets had lower emissions of NH₃, branched chain fatty acids (BCFA), and phenol compounds which translated into lower emissions in total odor. Emissions of NH₃ and odor were reduced by 8.9% and 4.2%, respectively, for each unit percent decline in dietary CP. Hydrogen sulfide was the dominate odorant associated with manure odor emissions. Based on nutrient mass balance, animal retention of dietary N and S increased by 7.0% and 2.4%, respectively, for each unit percent drop in crude protein fed animals, while C retention in the animal declined by 2.1%.

Dietary composition and particle size effects on swine manure characteristics and gas emissions

Nutrients excreted from animals affect the nutritive value of manure as a soil amendment as well as the composition of gases emitted from manure storage facilities. There is a dearth of information, however, on how diet type in combination with dietary particle size affects nutrients deposited into manure storage facilities and how this affects manure composition and gas emissions. To fill this knowledge gap, an animal feeding trial was performed to evaluate potential interactive effects between feed particle size and diet composition on manure characteristics and manure-derived gaseous emissions. Forty-eight finishing pigs housed in individual metabolism crates that allowed for daily collection of urine and feces were fed diets differing in fiber content and particle size. Urine and feces were collected and stored in 446-L stainless steel containers for 49 d. There were no interactive effects between diet composition and feed particle size on any manure or gas emission parameter measured. In general, diets higher in fiber content increased manure nitrogen (N), carbon (C), and total volatile fatty acid (VFA) concentrations and increased manure VFA emissions but decreased manure ammonia emissions. Decreasing the particle size of the diet lowered manure N, C, VFAs, phenolics, and indole concentrations and decreased manure emissions of total VFAs. Neither diet composition nor particle size affected manure greenhouse gas emissions.

Copper Speciation Evolution in Swine Manure Induced by Pyrolysis

Swine manures generally contain high levels of copper (Cu) resulting from its use as a growth promoter in feedstuff. Pyrolysis can further concentrate Cu whereas decrease its available fraction in swine manures. Here we investigated the speciation transformation of Cu and associated elements in swine manures induced by pyrolysis using multiple X-ray absorption spectroscopies. Results showed that over 82% of Cu existed as Cu(I)-S and Cu(I)-thiolate complexes in swine manures, which were transformed into stable Cu(I)₂S during pyrolysis at a low temperature of 300 °C and partially oxidized and desulfurized into Cu(II) compounds at a high temperature of 500 °C. The speciation evolution of Cu in swine manures was consistent with the speciation distribution of sulfur in feedstuff and its following changes in swine manures during pyrolysis. About 58% of phosphorus existed as CaHPO₄ and struvite in swine manures, which were gradually transformed into stable Ca-bound species such as hydroxyapatite during pyrolysis. The formation of stable phosphate, together with concentrated carbonates, significantly decreased the available Cu in pyrolyzed manures. These findings suggested that the high levels of S and P in feedstuff profoundly affected the speciation of Cu in the swine manures and derived biochars. This study has important implications to our understanding of the behaviors of heavy metals in manure-derived biochars once entering soil environments.