Odor Emissions Research Articles

Improving slaughterhouse byproducts utilization via anaerobic digestion, composting, and rendering

A large number of high-strength byproducts/wastes are discharged from slaughterhouses of meat industry in China and could pose serious environment pollution if without proper treatments. These wastes are rich in protein and lipid, and could potentially be utilized for effective recovery of energy and nutrients. In this study, three treatment scenarios of slaughterhouse wastes, namely anaerobic digestion (AD), composting, and rendering, were firstly investigated in China, and the greenhouse gas (GHG) emissions were calculated and compared. The results indicated that 23.1 Tg of slaughterhouse byproduct (SBP) and 679.7 Mm3 of wastewaters were estimated to discharge in 2020, which can potentially produce 2743 Mm3 of biomethane in AD, 316 Gg of nitrogen and 660 Gg of phosphorus nutrients in composting, or 5.4 Tg of rendering products in rendering. AD of SBP resulted in high GHG reductions (approximately 17.88 Tg of CO2-eq). The net energy produced from a typical pig slaughterhouse through treating SBP by the AD system was also estimated to be 194.7 GJ/d and GHG reduction was 100.3 Mg of CO2-eq/d. Technical challenges (include digester inhibition, odor emissions, and biosafety) were also summarized and discussed for practicing these technologies. Therefore, integrating the bioenergy/byproducts production to animal processing can potentially enhance the environmental sustainability of meat industry in China in the future.

Olfactory Mating Signals in the Migratory Locust Locusta migratoria.

Swarming locusts cause huge plagues across the world threatening food production. Before swarms form, locust populations exhibit a dramatic phase change from a solitary to a gregarious phase. The cause of this phase change is a complicated interplay of conspecific and environmental cues and is, especially for one of the major pests, the migratory locust Locusta migratoria, still not well understood. Here we study the behavior of both solitary and gregarious L. migratoria towards the headspace odors of conspecifics. As we do not find a general attraction of gregarious animals to the headspace of gregarious conspecifics, swarm formation does not seem to be mainly governed by olfactory aggregation cues. When testing for potential mating signals, we observe that the headspace of virgin gregarious females is highly attractive only towards virgin males of the same phase, while mated gregarious males and solitary males, regardless of their mating state, do not become attracted. Interestingly, this phase-specific attraction goes along with the finding, that mating behavior in experiments with inter-phasic pairings is extremely rare. Our data suggest that odor emissions in L. migratoria play a significant role in a mating context.

Microplastic, a possible trigger of landfill sulfate reduction process

The environmental impact of microplastics (MPs) formed from landfill has not been gained enough attention. This research investigated the characteristics of the MPs occurrence in landfills through field sampling. It shows that the MPs abundance in the landfill surface soil and non-landfill areas can reach 3573 items·g−1 and 3041 items·g−1, respectively. The vertical abundance of MPs increases significantly with depth, ranging from 387 to 11,599 items·g−1 with small size (≤10 μm, 65.61 %) and flake or wedge shape (38.48 %). The leachate movement in a longitudinal direction enables MPs to accumulate more easily in the landfill bottom layer with high moisture abundance. The abundance of MPs are significantly correlated with SO42− and S2− content, the two typical metabolic substrate and product of sulfate reduction process. In such heterogeneous environment, this significant correlation is not a random phenomenon in terms of the MPs have known substantial impact on biogeochemical processes. Microplastic is a possible trigger of landfill odor emission related with sulfate reduction. This research could serve as a reference for MPs and odor pollution management in landfills.

Assessment of dimethyl sulphide odorous emissions during coal extraction process in Coal Mine Velenje

Underground coal extraction at Coal Mine Velenje occasionally gives rise to odour complaints from local residents. This manuscript describes a robust quantification of odorous emissions of mine sources and a model-based analysis aimed to establish a better understanding of the sources, concentrations, dispersion, and possible control of odorous compounds during coal extraction process. Major odour sources during underground mining are released volatile sulphur compounds from coal seam that have characteristic malodours at extremely low concentrations at micrograms per cubic metre (μg/m3) levels. Analysis of 1028 gas samples taken over a 6-year period (2008–2013) reveals that dimethyl sulphide ((CH3)2S) is the major odour active compound present in the mine, being detected on 679 occasions throughout the mine, while hydrogen sulphide (H2S) and sulphur dioxide (SO2) were detected 5 and 26 times. Analysis of gas samples has shown that main DMS sources in the mine are coal extraction locations at longwall faces and development headings and that DMS is releasing during transport from main coal transport system. The dispersion simulations of odour sources in the mine have shown that the concentrations of DMS at median levels can represent relatively modest odour nuisance. While at peak levels, the concentration of DMS remained sufficiently high to create an odour problem both in the mine and on the surface. Overall, dispersion simulations have shown that ventilation regulation on its own is not sufficient as an odour abatement measure.

Implementation of an electronic nose for real -time identification of odour emission peaks at a wastewater treatment plant

This paper proposes a novel approach for the real-time monitoring of odour emissions from a WasteWater Treatment Plant (WWTP) using an Instrumental Odour Monitoring System (IOMS). The plant is characterized by unpredictable odour peaks at its arrival tank (AT), generating nuisance and complaints in the population living nearby the plant. Odour peaks are most likely due to the conferment of non-identified and malodorous wastewaters coming from various industrial activities. Due to the high variability of sources collecting their wastewaters to the WWTP, a new methodology to train the IOMS, based on the use of a one-class classifier (OCC), has been exploited. The OCC enables to detect deviations from a “Normal Operating Region” (NOR), defined as to include odour concentrations levels unlikely to cause nuisance in the citizenship. Such deviations from the NOR thus should be representative of the odour peaks. The results obtained prove that the IOMS is able to detect real-time alterations of odour emissions from the AT with an accuracy on independent validation data of about 90% (CI95% 55–100%). This ability of detecting anomalous conditions at the AT of the WWTP allowed the targeted withdrawal of liquid and gas samples in correspondence of the odour peaks, then subjected to further analyses that in turn enabled to investigate their origin and take proper counteractions to mitigate the WWTP odour impact.

Effects of Air Exchange Rate on VOCs and Odor Emission from PVC Veneered Plywood Used in Indoor Built Environment

As people spend more than 80% of the day in an indoor built environment, indoor air quality pollution caused by volatile organic compounds (VOCs) emitted from wood-based panels has attracted attention. PVC veneered plywood used in the indoor built environment and relevant VOCs and odor emission under different air exchange rates were studied in this research. Microcell thermal extraction technology was used to sample under the conditions of three different air exchange rates and loading factors: 0.2 m3·h−1·m−2, 0.5 m3·h−1·m−2, and 1.0 m3·h−1·m−2, respectively. Gas Chromatography-Olfactometry-Mass Spectrometry (GC-MS-O) was used to analyze VOCs and their odor release characteristics. The key odor characteristic compounds were analyzed by subjective and objective methods, and the main sources of odor release from the board were analyzed. In this experiment, the time-intensity method is mainly used to analyze the mass concentration of VOCs released from plywood. By comparing the mass concentration and odor intensity of VOCs released from plywood and its components under different air exchange rates and loading factors, the influence of the ratio of air exchange rate to loading factor on plywood is judged. The results show that with three different ratios of air exchange rate to loading factor, the VOCs emission concentration and odor intensity of plywood can be affected greatly and are the highest at 0.2 m3·h−1·m−2. The components released by PVC veneered plywood are mainly aromatic compounds, alkanes and aldehydes. The research findings can guide the indoor built environment design and construction process to control the emission of VOCs by adjusting the air exchange rate, which helps build more healthy and sustainable living environments for humans.

Volatile Organic Compounds from Cassava Plants Confer Resistance to the Whitefly Aleurothrixus aepim (Goeldi, 1886).

Cassava is an essential tuber crop used to produce food, feed, and beverages. Whitefly pests, including Aleurothrixus aepim (Goeldi, 1886) (Hemiptera: Aleyrodidae), significantly affect cassava-based agroecosystems. Plant odours have been described as potential pest management tools, and the cassava clone M Ecuador 72 has been used by breeders as an essential source of resistance. In this study, we analysed and compared the volatile compounds released by this resistant clone and a susceptible genotype, BRS Jari. Constitutive odours were collected from young plants and analysed using gas chromatography-mass spectrometry combined with chemometric tools. The resistant genotype released numerous compounds with previously described biological activity and substantial amounts of the monoterpene (E)-β-ocimene. Whiteflies showed non-preferential behaviour when exposed to volatiles from the resistant genotype but not the susceptible genotype. Furthermore, pure ocimene caused non-preferential behaviour in whiteflies, indicating a role for this compound in repellence. This report provides an example of the intraspecific variation in odour emissions from cassava plants alongside information on odorants that repel whiteflies; these data can be used to devise whitefly management strategies. A better understanding of the genetic variability in cassava odour constituents and emissions under field conditions may accelerate the development of more resistant cassava varieties.

A comprehensive review on the decentralized composting systems for household biodegradable waste management

Municipal solid waste primarily consists of household biodegradable waste (HBW). HBW treatment is a crucial step in many countries due to rapid urbanization. Composting is an effective technique to treat HBW. However, conventional composting systems are unable to produce matured compost (MC), as well as releasing huge amounts of greenhouse and odorous gases. Therefore, this review attempts to suggest suitable composting system to manage HBW, role of additives and bulking agents in composting process, identify knowledge gaps and recommend future research directions. Centralized composting systems are unable to produce MC due to improper sorting and inadequate aeration for composting substrate. Recently, decentralized compost systems (DCS) are becoming more popular due to effective solid waste reduction at the household and/or community level itself, thereby reducing the burden on municipalities. Solid waste sorting and aeration for the composting substrate is easy at DCS, thereby producing MC. However, Mono-composting of HBW in DCS leads to production of immature compost and release greenhouse and odorous gases due to lower free air space and carbon-to-nitrogen ratios, and higher moisture content. Mixing HBW with additives and bulking agents in DCS resulted in a proper initial substrate for composting, allowing rapid degradation of substrate due to longer duration of thermophilic phase and produce MC within a shorter duration. However, people have lack of awareness about solid waste management is the biggest challenge. More studies are needed to eliminate greenhouse and odorous gases emissions by mixing different combinations of bulking agents and additives (mainly microbial additives) to HBW in DCS.

Relationship between human behavior and indoor air quality of private room in a care facility for the elderly in Japan

In Japan, the number of elderly people in need of nursing care is increasing while the population of young people is decreasing, and the potential for labor shortages in the field of elder care is of great concern. This study aimed to estimate the behavior of the elderly by using sensors to monitor indoor air quality (IAQ), without placing undue burden on the elderly or their caregivers. Odor and carbon dioxide (CO2) concentrations were monitored in a private room of a nursing home in the Kanto Region of Japan, the behaviors of the resident and staff members were recorded, and the relationship between the two was analyzed. Both odor and CO2 concentrations were higher when the resident was present than when absent, indicating that the resident was one of the main sources of indoor odor and CO2. In addition, after the resident entered the room, the CO2 concentration increased and remained stable, whereas the odor concentration tended to vary after the resident entered the room, first increasing and later decreasing. This suggested that the increase or decrease in odor could be used to monitor the behavior of the resident and staff members. The relationship between the slopes of odor and CO2 in typical behavioral events suggest that if only odor increases and CO2 does not change, the likelihood of the event in which feces were observed during diaper changes is high. In addition, based on the behavior near the sensor, the rate of CO2 and odor emissions differed between the elderly resident and the younger staff members, suggesting that the ratio of odor slope to CO2 slope may be greater in the elderly than in younger people. Furthermore, the repeated number of increases and decreases in odor and CO2 suggested that multiple events could be distinguished. These results suggest that IAQ can be utilized to estimate the behavior of residents and staff in nursing care facilities for the elderly.

Foaming Properties of Lignosulfonates in the Flotation Process.

The widely used technology for the selective flotation of copper and molybdenite using sodium hydrosulfide (NaSH) to depress copper sulfides creates environmental issues related to the potential emissions of toxic hydrosulfide gas (H2S) and bad odors. Previous studies showed that molybdenite flotation can be depressed by the action of lignosulfonates, but no significant progress has been made in studying the effect that these reagents have on the foaming/frothing phenomena in flotation. The objective of this work was to investigate the foaming properties of three samples of lignosulfonates through measurements of surface tension, foamability, bubble size distributions, and water recovery. A sugared sodium lignosulfonate (NaLS), a calcium lignosulfonate (CaLS), and a sample prepared by sulphomethylation of kraft lignin (KLS) were tested. It was found that all lignosulfonates displayed surface activity that decreased with pH and was related to the degree of anionicity and molecular weight. The NaLS lignosulfonate showed the highest dynamic foamability index (DFI) value, compared to that of the CaLS and KLS samples. The lignosulfonates tested in this study strongly affected bubble size. Water recovery tests performed using flotation experiments in a two-phase system showed that the KLS and NaLS samples had the strongest effect, which correlated with the surface tension, foamability, and bubble size results.

ODOUR EMISSIONS FROM A MUNICIPAL SOLID WASTE DUMPING AREA THAT ARE AT THE MODERATE STAGE OF DISINTEGRATION

<p>Odour is a major concern as they are termed hazardous to the surroundings as well as life forms when they are exposed to the environment. Odour emission is also one of the indicators of environmental changes that impact the environment. Among the different sources of odour emission, in the dumping yard itself, different types and ages of waste are dumped in the municipal solid waste (MSW) dumping yards. This study aims to relate odour emission and concentration changes caused by different weather patterns. Different periods of waste (fresh waste, moderate waste, and ripened waste) and weather seasons (summer and winter) affect the odour concentrations. Mixtures of gases and intolerable odours are major components of the MSW dumping yard. The odour concentration was monitored in the different periods of waste (moderate wastes) at different locations in the MSW dumping yard. In this study, it was found that meteorological conditions are also one of the main influences on odour concentrations in the environment. In this study, a comprehensive investigation of odour pollution from a local MSW dumping yard has been performed. The odour concentration indicates that the maximum range of aromatic hydrocarbon chemical compounds (volatile organic compounds) reported was T-butylbenzene at 1.41µg/m3 and the minimum range was Sec-butylbenzene at 0.07µg/m3. This study will provide information on odour emissions in urban areas and how VOC (Volatile Organic Compounds) components are present and affect the dumping yards surrounding those areas</p>

Odour Perception Using a Sniffing Team at a Municipal Solid Waste Treatment Plant: A Case Study

The monitoring of odour intensity, generated by a landfill area, is a difficult activity since it is a multi-source problem with discontinuous odour emissions. A modified sniffing team method is described here and applied to determine the main odour sources in a landfill located in Pomerania, Poland. Four consecutive test sessions were performed during the following months: August, December, April, and June. It was found that the main odour sources are as follows: a closed-chamber composting facility for leach storage; the site wherein technological operations associated with compost turn-over during open-air aeration processes are performed; and the landfill site. The results of the sniffing team method present the indicative values of sensory testing. The application of the presented method was limited by disturbances due to changing atmospheric conditions. The calculated odour intensities and concentrations correspond with real sensitive perceptions of the tested environment.

Effect of exogenous CaO addition on H2S production from waste activated sludge and its influence mechanism.

Hydrogen sulfide (H2S) production from waste activated sludge (WAS) is the main reason for odor emission during anaerobic fermentation system. CaO has been reported to effectively improve the resources recovery of WAS, but its potential effect on H2S production in anaerobic fermentation process remains unrecognized. In present study, it was found that the addition of 60mg/g VSS CaO greatly inhibited H2S production and the maximum yield of H2S was 60.1±1.8% lower than the control. Mechanism investigation demonstrated that CaO destroyed sludge structure and increased the release of intracellular organic matter with hydrogen bonding networks destroying, but had a mild effect on the transformation of sulfur containing organic matters and inorganic sulfate reduction. Additionally, the enhancement in H+ and S2- consumption by alkaline condition and metal ions release was another reason for the inhibition of H2S production in CaO addition reactors. Furthermore, microbial analysis showed that CaO addition importantly reduced the hydrolysis microorganism, particularly denitrification hydrolytic bacterias (e.g.,unclassified_f_Chitinophagaceaeand Dechloromonas), sulfate reducing bacterias (SRBs) (e.g., unclassified_c_Deltaproteobacteria and Desulfosarcina) and genes (e.g.,PepD, cysN/D, CysH/C and Sir) involved in organic sulfur hydrolysis and sulfate reduction. Results from this study provides theoretical insights into the practical applications of CaO.

Effects of aeration rate on the cornstalks used for filtration of anaerobically digested manure centrate direct composting process: Maturity and gas emissions

This study aimed to clarify the effect of the aeration rate on the maturity and gas emission during the direct composting process of the cornstalks for ADMC filtration under three aeration rates of 0.05 (R1 0.05), 0.1 (R2 0.10), and 0.15 (R3 0.15) m3/m3 min for the 21-day composting experiment. The results showed that the temperature of R3(0.15) treatment was lower than the others during composting. All treatments could maintain high temperatures (>50 °C) for more than 5 days, meeting the Chinese national standard for organic fertilizer production. The cumulative CO2 emission of the R1(0.05) treatment was the highest, which was 36.59% and 33.04% higher than the R2(0.10) treatment and R3(0.15) treatment, respectively. R1(0.05) treatment is not conducive to N2O emissions, and R3(0.15) treatment is not conducive to CH4 emissions. The cumulative emissions of NH3 and sulfur-containing odor in the R1(0.05) treatment were the lowest, and the cumulative emissions of H2S, C2H6S, and COS in the R3(0.15) treatment were the highest. Based on the comprehensive comparison, the recommended aeration rate for the cornstalks after the ADMC filtration direct composting is 0.05 m3/m3 min. The results can provide a theoretical basis and measures for the process parameters of the cornstalks for ADMC filtration direct composting.

Relating bacterial dynamics and functions to greenhouse gas and odor emissions during facultative heap composting of four kinds of livestock manure

Although facultative heap composting is widely used in small and medium-sized livestock farms in China, there are few studies on greenhouse gas (GHG) and odor emissions from this composting system. This study focused on GHG and odor emissions from facultative heap composting of four types of livestock manure and revealed the relationship between the gaseous emissions and microbial communities. Results showed that pig, sheep, and cow manure reached high compost maturity (germination index (GI) > 70%), whereas chicken manure had higher phytotoxicity (GI = 0.02%) with higher electrical conductivity and a lower carbon/nitrogen ratio. The four manure types significantly differed in the total GHG emission, with the following pattern: pig manure (308 g CO2-eq·kg−1) > cow manure (146 g CO2-eq·kg−1) > chicken manure (136 g CO2-eq·kg−1) > sheep manure (95 g CO2-eq·kg−1). Bacterium with Fermentative, Methanotrophy and Nitrite respiratory functions (e.g. Pseudomonas and Lactobacillus) are enriched within the pile so that more than 90% of the GHGs are produced in the early (days 0–15) and late (days 36–49) composting periods. CO2 contributed more than 90% in the first 35 d, N2O contributed 40–75% in the late composting period, and CH4 contributed less than 8.0%. NH3 and H2S emissions from chicken and pig manure were 4.8 times those from sheep and cow manure. Overall, the gas emissions from facultative heap composting significantly differed among the four manure types due to the significant differences in their physicochemical properties and microbial communities.

Microbiome-metabolomics analysis reveals abatement effects of itaconic acid on odorous compound production in Arbor Acre broilers

BackgroundPublic complaints concerning odor emissions from intensive livestock and poultry farms continue to grow, as nauseous odorous compounds have adverse impacts on the environment and human health. Itaconic acid is a metabolite from the citric acid cycle of the host and shows volatile odor-reducing effects during animal production operations. However, the specific role of itaconic acid in decreasing intestinal odorous compound production remains unclear. A total of 360 one-day-old chicks were randomly divided into 6 treatment groups: control group (basal diet) and itaconic acid groups (basal diet + 2, 4, 6, 8 and 10 g/kg itaconic acid). The feeding experiment lasted for 42 d.ResultsDietary itaconic acid supplementation linearly and quadratically decreased (P < 0.05) the cecal concentrations of indole and skatole but did not affect (P > 0.05) those of lactic, acetic, propionic and butyric acids. The cecal microbial shift was significant in response to 6 g/kg itaconic acid supplementation, in that the abundances of Firmicutes, Ruminococcus and Clostridium were increased (P < 0.05), while those of Bacteroidetes, Escherichia-Shigella and Bacteroides were decreased (P < 0.05), indicative of increased microbial richness and diversity. Furthermore, a total of 35 significantly (P < 0.05) modified metabolites were obtained by metabolomic analysis. Itaconic acid decreased (P < 0.05) the levels of nicotinic acid, nicotinamide, glucose-6-phosphate, fumatic acid and malic acid and increased (P < 0.05) 5-methoxytroptomine, dodecanoic acid and stearic acid, which are connected with the glycolytic pathway, citrate acid cycle and tryptophan metabolism. Correlation analysis indicated significant correlations between the altered cecal microbiota and metabolites; Firmicutes, Ruminococcus and Clostridium were shown to be negatively correlated with indole and skatole production, while Bacteroidetes, Escherichia-Shigella and Bacteroides were positively correlated with indole and skatole production.ConclusionsItaconic acid decreased cecal indole and skatole levels and altered the microbiome and metabolome in favor of odorous compound reduction. These findings provide new insight into the role of itaconic acid and expand its application potential in broilers.

Effect of reducing dietary crude protein level on growth performance, blood profiles, nutrient digestibility, carcass traits, and odor emissions in growing-finishing pigs.

This study was conducted to evaluate the effect of a low-protein (LP) diet on growth performance, carcass traits, nutrient digestibility, blood profiles, and odor emissions in growing-finishing pigs. A total of 126 crossbred pigs ([Yorkshire × Landrace] × Duroc) with an average body weight (BW) of 38.56 ± 0.53 kg were used for a 14-week feeding trial. Experimental pigs were allotted to one of 6 treatments in 3 replicates of 7 pigs per pen in a randomized complete block design. Pigs were fed each treatment diet with different levels of crude protein (CP). Phase 1 (early growing): 14%, 15%, 16%, 17%, 18%, 19%; phase 2 (late growing): 13%, 14%, 15%, 16%, 17%, 18%; phase 3 (early finishing): 12%, 13%, 14%, 15%, 16%, 17%; phase 4 (late finishing): 11%, 12%, 13%, 14%, 15%, 16%. All experimental diets in each phase were contained the same concentration of lysine (Lys), methionine (Met), threonine (Thr), and tryptophan (Trp). Over the entire experimental period, there was no significant difference in body weight (BW), average daily feed intake (ADFI), and gain-to-feed ratio (G:F ratio) among all treatments (p>0.05), but a quadratic effect (p = 0.04) was observed in average daily gain (ADG) during the late finishing phase with higher ADG in Group D. Blood urea nitrogen concentration linearly increased with an increase in dietary CP levels (p<0.01). Regarding nutrient digestibility, excreted nitrogen in urine and feces and nitrogen retention linearly increased as the CP level increased (p<0.01). A linear effect was observed with increasing CP levels in amines, ammonia, and hydrogen sulfide in odor emissions (p<0.01). No significant effects were observed in the measurements of carcass traits and meat characteristics (p>0.05). In phase feeding, reducing the CP level to 14% in early-growing pigs, 13% in late-growing pigs, 12% in early-finishing pigs, and 11% in late-finishing pigs is recommended.

Effects of the Combined Odor Reducing Additive on Fecal Fermentation Characteristics and Growth Performance in Hanwoo Steers

Background: Odors from livestock facilities are mainly caused by livestock manure. This causes deterioration of the health of the farm workers and the productivity of livestock. Complex additives with different actions are required to effectively reduce fecal contaminants. This study was conducted to investigate the effects of combined odor reducing additive (CORA) supplementation on the odor emission of feces and the growth performance of Hanwoo steers. Methods: Ninety-six Hanwoo steers were randomly assigned to the following four groups: control group fed with CORA-unsupplemented formula feed; T0.05 group fed with 0.05% CORA-supplemented formula feed; T0.1 group fed with 0.1% CORA-supplemented formula feed and T0.2 group fed with 0.2% CORA-supplemented formula feed. The CORA comprised 88% zeolite, 3% Bacillus licheniformis, 3% Bacillus polyfermenticus and 6% saponin. Result: The fecal NH3-N gas emission was significantly lower in the T0.2 group than in the control group (P less than 0.05). The fecal H2S gas emission at 20 d of incubation was lower in the T0.2 group than in the control group (P less than 0.05). The fecal NH3-N concentration was lower in proportion in all the groups with different supplementation levels of CORA than in the control group after 7 d of incubation (P less than 0.05). The number of fungi in feces was lower in the treatment groups than in the control group and the lowest was for T0.2 group (P less than 0.05). The results of this study indicated that CORA supplementation can reduce the emission of harmful gases (NH3-N and H2S) and odor-causing substances in feces and inhibit mold growth.

Effects of dietary protein levels on performance, nitrogen excretion, and odor emission of growing pullets and laying hens

The objective of this study was to determine the effects of dietary crude protein (CP) levels on production performance, nitrogen balance, and odor emission of excreta in growing pullets and laying hens from 13 to 32 wk of age. Two hundred and forty pullets (Hy-Line Brown) were randomly assigned to 1 of 4 dietary groups with 10 replicates per group, and 6 birds per replicate. Experimental diets were formulated to contain 4 graded CP levels in the diets of pullets ranging from 180, 160, 140, and 120 g/kg of diet during 13 to 18 wk (phase 1) and in the diets of laying hens from 190, 170, 150, and 130 g/kg of diet during 19 to 32 wk (phase 2). The limiting amino acids including lysine, methionine, and threonine were supplemented to maintain constant equal amino acid concentrations in all experiment diets. In phase 1, decreasing dietary CP levels did not affect growth performance but increased (linear and quadratic effect, P < 0.05) the relative abdominal fat contents and triglyceride concentration in serum samples. High-density lipoprotein cholesterol in serum samples decreased as the CP levels decreased in the diets of pullets. Dietary CP levels quadratically increased (P < 0.05) the villus height and the villus height to crypt depth ratio but did not affect tibia traits and relative organ weights in pullets at 18 wk. Apparent digestibility of dry matter and ether extract increased with decreasing dietary CP levels in pullets. Graded CP levels linearly increased the digestibility of dry matter, CP, and ether extracts but lowered that of crude ash in laying hens. Nitrogen excretion was linearly decreased (P < 0.05) as the dietary CP levels decreased in both pullets and laying hens. Dietary CP levels only affected carbon dioxide emission in pullets. In phase 2, dietary CP levels did not affect growth performance and the ages at first egg laying and to reach 50% egg production in laying hens. However, egg weights were decreased (linear and quadratic effect, P < 0.05) as the dietary CP level decreased in laying hens. Increasing dietary CP levels increased Haugh unit at 26 wk but lowered corticosterone concentrations in yolk samples at 22 wk. Collectively, this study shows that dietary CP levels could be decreased to reduce nitrogen excretion without adverse effects on performance and egg quality of growing pullets and laying hens.

Monoterpene alcohols induced by sweet potato weevil larvae deter conspecific adults from feeding and oviposition.

Intraspecific competition is shared in the insect world, especially under the condition of limited food and space resources. To avoid intraspecific competition and increase offspring survival, insects have evolved various effective strategies. A widely-accepted tactic is employing chemical cues, which are frequently utilized as indicators of conspecific colonization. The sweet potato weevil (SPW), Cylas formicarius, is a destructive pest of sweet potatoes. Its larvae bore into sweet potatoes and alter the emission of odors. The present study aimed to investigate whether volatiles associated with SPW larvae feeding influence the behavioral preference of conspecific adults. Volatiles from SPW larvae-infested sweet potatoes were collected by a head-space method and analyzed using gas chromatography-electroantennogram detector (GC-EAD) and gas chromatography-mass spectrometry (GC-MS). Five compounds eliciting EAD responses from the antennae of both male and female adult SPW were identified from sweet potatoes with the third-instar larvae, including linalool, citronellol, nerol, geraniol, and ipomeamarone. Four monoterpene alcohols significantly repelled SPW adults from feeding and oviposition at higher doses in the behavioral preference bioassays. Among them, geraniol displayed the strongest repellent activities for SPW feeding and oviposition. These results suggested that SPW larvae could reduce colonization of adult SPWs by inducing monoterpene alcohols, thereby avoiding intraspecific competition. The present study demonstrated that volatile monoterpene alcohols induced by SPW larvae are chemical cues of larvae occupation for SPW adults to change their behavioral preference. Unveiling factors that mediate avoidance of intraspecific competition could help develop repellents or oviposition deterrents for SPW control. © 2023 Society of Chemical Industry.