Quantitative identification and sensor sensitivity analysis in detection of odor volatile compounds emitted by scaly grain mites, Suidasia pontifica Oudemans.

BACKGROUND: In Thailand, the scaly grain mite, Suidasia pontifica Oudemans, impacts the feed industry by emitting a lemongrass-like odor in contaminated feed, reducing its palatability. This study focused on identifying volatile organic compounds (VOCs) associated with this odor in contaminated chicken feeds and ground maize, as well as individual mites using gas chromatography-mass spectrometry (GC-MS). We explored the relationship between VOC concentration and mite population size in chicken feed cultures, aiming to detect minimal mite presence through regression models. Additionally, we tested the sensitivity of nine electronic odor sensors in detecting these VOCs. RESULTS: Our results showed Z-citral and E-citral present in mite-contaminated ground maize, chicken feeds, but absent in uncontaminated samples. Mite populations in chicken feed followed a normal distribution, increasing rapidly, peaking, and then declining, a pattern mirrored in the concentrations of Z-citral and E-citral. Simple linear regression models confirmed a positive correlation between mite density and citral concentrations. Polynomial regression models indicated Z-citral is detectable at mite densities over 67 individuals per gram and E-citral over 3.89 individuals per gram. Odor sensors showed varying readings across different citral concentrations, uncontaminated, and mite-infested chicken feeds. CONCLUSIONS: Our study confirms that S. pontifica are responsible for the lemongrass-like odor in infested samples, due to Z-citral and E-citral. The citral concentrations increase with mite population growth and are detectable at low mite densities, suggesting their effectiveness as biomarkers for early mite infestation detection. Additionally, MQ series odor sensors detected these VOCs, indicating their potential for monitoring mite infestations in storage environments. © 2024 Society of Chemical Industry.

Influences of spent coffee grounds on skin mucosal and serum immunities, disease resistance, and growth rate of Nile tilapia (Oreochromis niloticus) reared under biofloc system.

The study was executed to find out the potential effects spent coffee ground (SCG) on Nile tilapia's skin mucosal and serum immunities, disease prevention, and growth rate reared in a biofloc system. Nile tilapia fingerlings (average weight 15.25 ± 0.07 g) were disseminated into 15 aquaria (150 L tank-1) at a density of 20 fish per aquarium and treated five diets: SCG1 (control), SCG2 (10 g kg-1), SCG3 (20 g kg-1), SCG4 (40 g kg-1), and SCG5 (80 g kg-1) for eight weeks. A Completely Randomized Design (CRD) with three replications was applied. Growth rate, skin mucus, and serum immunities were quantified every 4 weeks; whereas the challenge study was conducted at the termination of the feeding trial. The outputs indicated that dietary incorporation of SCG give rise to the enhancement of SGR and FCR in comparison with the control, with best levels noted in fish fed SCG2 diet. Similarly, significant enhancements in skin mucosal and serum immunities were revealed in fish treated SCG2 over the control and other SCG diets. Likewise, higher survival rates against Streptococcus agalactiae were displayed in fish fed SCG, with the maximum level displayed in the fish treated SCG2. In conclusion, dietary supplementation of SCG2 (10 g kg-1) can be potential used as immunostimulants in tilapia aquaculture.

Physicochemical profiles of stingless bee (Apidae: Meliponini) honey from South East Asia (Thailand).

This study examines the physicochemical properties of stingless bee honey from SE Asia (Thailand). Twenty-eight stingless bee honey samples, from 11 stingless bee species, were examined. Results reveal an average color (67 ± 19 mm Pfund), moisture (31 ± 5.4 g/100g), ash (0.531 ± 0.632 g/100g), electrical conductivity (1.1 ± 0.780 ms/cm), pH of (3.6 ± 0.198), total acidity (164 ± 162 meq/kg), diastase activity (1.5 ± 1.6 °Gothe) and hydroxymethylfurfural (8.7 ± 12 mg/kg). The carbohydrate profile is: total sugar (51 ± 21 g/100g), fructose (17 ± 9.7 g/100g), glucose (14 ± 8.6g/100g), maltose (41 ± 15 g/100g) and sucrose (1.2 ± 2.7 g/100g). These findings are not dissimilar to those reported for stingless bee honeys from the neo-tropics. When compared with the Apis mellifera standard, stingless bee honey is characterized as possessing higher moisture content, acidity, ash and HMF but a lower level of total sugars.

The life cycle and effectiveness of insecticides against the bed bugs of Thailand.

The purpose of this study was to determine the life cycle and effectiveness of insecticides against bed bugs in Thailand. Bed bugs from dwelling places in Chon Buri and Chiang Mai provinces were determined to be Cimex hemipterus and Cimex lectularius, respectively. Both bed bug species were reared by feeding on rabbit blood at 2-day intervals in laboratory conditions at 28-32 degrees C with 75% relative humidity. The duration from egg to adult stages took 39.9 +/- 7.0 and 36.9 +/- 8.2 days in C. hemipterus and C. lectularius, respectively. The insecticides, propetamphos 20% CS, pirimiphos-methyl 50% EC, bifenthrin 25% WP and alpha-cypermethrin 5% SC, were tested against adult C. lectularius using a Potter spray tower. The concentrations at which 50% of bed bugs were either dead or moribund (ED50) for propetamphos and pirimiphos-methyl were 6.67 and 14.93 mg/m2 for the active ingredients on day 3 and the ED50 for bifenthrin and alpha-cypermethrin were 1,767.76 and 353.55 mg/m2, respectively. The results reveal C. lectularius in Thailand has a tendency to develop pyrethroid resistance.