Shitu Tan

Microplastics (MPs) are increasingly accumulating in agricultural soils, while their effects on crop-associated rhizosphere microbial communities and ecological functions remain insufficiently understood, particularly for different polymer types. In this study, polyethylene (PE) and polystyrene (PS) microplastics with the same particle size (2 μm) were applied at different concentrations (0, 0.1%, 0.5%, 1%, and 5%, w/w) to investigate their effects on oat rhizosphere bacterial communities and predicted functional potentials. The results showed that microplastic addition significantly altered bacterial community diversity, composition, and predicted functional profiles. Compared to the control (Ctrl), the 1% PE treatment significantly reduced bacterial richness-related indices (p < 0.05), whereas PS mainly affected bacterial diversity. Microplastic treatments also reshaped dominant bacterial taxa and altered the predicted functional potentials associated with carbon and nitrogen cycling. In particular, the 1% PE treatment significantly reduced the predicted relative abundance of the carbon fixation-related gene cbbL (p < 0.05). In addition, high-concentration (5%) PE enhanced several predicted functional potentials related to nitrogen cycling, including nifH, ureA, and amoC. Overall, PE and PS microplastics induced polymer- and concentration-dependent changes in oat rhizosphere bacterial communities. These findings suggest that microplastic accumulation in agricultural soils may influence ecosystem processes by modifying microbial diversity and potential biogeochemical functions. This study provides new insights into the ecological consequences of different microplastic polymers in crop rhizosphere ecosystems and highlights the importance of considering polymer-specific effects when evaluating soil microplastic pollution.

N-carbamylglutamate (NCG) is a structural analog of N-acetylglutamate and has multifunctional roles in animal production. However, few studies have been conducted to evaluate the effects of NCG on protein digestive function and muscle growth in broiler chickens. This study investigated whether NCG could improve muscle growth via protein digestive ability and amino acid metabolism in broiler chickens. A total of 144 one-day-old male broiler chickens were randomly allocated to four treatments with six replicates of 6 broiler chickens each. The treatments were a basal diet and a basal diet with NCG supplementation at three graded levels (150 g/t, 300 g/t, and 450 g/t of NCG). The results showed that NCG supplementation significantly improved the average daily weight gain (ADG) and decreased the feed conversion ratio (FCR) compared to the control group (p < 0.05) and increased the weight of leg muscle and breast muscle. Furthermore, NCG supplementation significantly increased protein digestibility, the activities of amylase, trypsin and lipase, and villus height in the ileum (p < 0.05), which demonstrated that digestibility and absorption were improved by NCG in broiler chickens. Analysis of plasma amino acids, hormone levels and the gene expression of breast muscle revealed that NCG increased the concentration of GABA, glutamate, glutamine, leucine, threonine, valine, branched-chain amino acids and essential amino acids and the levels of testosterone and IGF-1 in plasma (p < 0.05). Additionally, NCG increased the expression of mTOR and P70S6K in breast muscle tissue. Therefore, NCG supplementation could be an important nutritional strategy to improve product performance, muscle growth and development, and meat yield. The 300 g/t supplementation level was found to be the practical optimum dose, as it produced effects comparable to the highest dose (450 g/t) on most parameters while offering better cost-effectiveness. This study provides new insights into the application of NCG for meat production improvement in broiler chickens.

Despite increasing environmental concerns, there are few studies on the potential effects of polyethylene and polystyrene microplastics on feed crops. The effects of polyethylene (PE) and polystyrene (PS) microplastics with a diameter of 2 μm at different concentrations (0.1%, 0.5%, 1%, and 5%) (w/w) on the growth and development of oats were analyzed in a pot experiment, with no microplastics added as the Control (Ctrl) group. The results showed that PS microplastics exhibited a spherical morphology, whereas PE microplastics displayed an irregular morphology. PE microplastics had an inhibitory effect on oat growth, chlorophyll content, photosynthetic parameters and antioxidant enzyme activity, and this effect was concentration-dependent; specifically, the inhibitory intensity increased progressively as the concentration of PE microplastics rose. In contrast, treatments involving varying concentrations of PS microplastics elicited distinct effects on the physiological and biochemical parameters of oats. The 0.1% PS microplastics treatment significantly enhanced the net photosynthetic rate of oat leaves (by 14.0%), while the 5% PS microplastics treatment significantly reduced the seedling height (by 31.1%), the total chlorophyll content (by 34.6%), the transpiration rate (by 35.7%), the stomatal conductance (by 71.1%), and the intercellular CO₂ concentration (by 43.1%). Furthermore, a significant decrease in antioxidant enzyme activity was observed in oats after the 5% PE microplastics treatment. The activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) decreased by 17.1%, 89.2% and 5.6%, respectively. At the same concentration (5%), PE microplastics exhibited a more pronounced inhibitory effect on oats compared to PS microplastics. In summary, this study demonstrates that microplastics impair photosynthesis and antioxidant capacity in oats, thereby inhibiting their normal growth and development. These findings provide a theoretical foundation and supporting data for further research into the toxicity of microplastics to oats.