Deltamethrin, an important pyrethroid insecticide, is frequently detected in human samples. This study aims to assess the potential effects of deltamethrin on human health and investigate the patterns of residue enrichment and elimination in 112 healthy laying hens. These hens were administered 20 mg·kg⁻¹ deltamethrin based on their body weight. Gas chromatography-mass spectrometry (GC-MS) was used to investigate the residue enrichment pattern and elimination pattern of deltamethrin in the hens. The results indicated a significant increase in the concentration of deltamethrin in chicken manure during the treatment period. By the 14th day of administration, the concentration of deltamethrin in the stool reached 13,510.9 ± 172.24 μg·kg⁻¹, with a fecal excretion rate of 67.56%. The pulmonary deltamethrin concentration was the second highest at 3844.98 ± 297.14 μg·kg⁻¹. These findings suggest that chicken feces contain substantial amounts of deltamethrin after 14 days of continuous administration, and that it can easily transfer to the lungs. After 21 days of drug withdrawal, the residual concentration of deltamethrin in the fat of laying hens was 904.25 ± 295.32 μg·kg⁻¹, with a half-life of 17 days and a slow elimination rate. In contrast, the lungs showed relatively low elimination half-lives of 0.2083 days, indicating faster elimination of deltamethrin in this tissue. These results highlight differences in the rate of deltamethrin elimination in different tissues during drug withdrawal. The fat of laying hens exhibited the highest residue of deltamethrin and the slowest elimination rate, while the lungs showed the fastest elimination rate. Moreover, deltamethrin was found to accumulate in the edible tissues of eggs and laying hens, suggesting that humans may be exposed to deltamethrin through food.

This study investigated the effects of different dietary flaxseed inclusion levels (0, 2, 4, 6, 8, and 10%) on the fatty acid composition, plasma biochemical parameters, and meat quality of Beijing-you chickens. A total of 960 6-week-old birds were randomly assigned to six dietary treatments in a completely randomized design, with eight replicates per treatment. Dietary flaxseed supplementation significantly decreased plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), and triglyceride (TG) concentrations (p < 0.05), while significantly increasing high-density lipoprotein cholesterol (HDL-C) levels (p < 0.05). Meat quality was also improved, as evidenced by reduced drip loss (p < 0.05). Moreover, gas chromatography analysis revealed that increasing dietary flaxseed levels markedly elevated the concentrations of total ω-3 polyunsaturated fatty acids (ω-3 PUFAs) in both breast and leg muscles (p < 0.05), accompanied by a significant reduction in the ω-6/ω-3 ratio (p < 0.05). Dietary flaxseed supplementation did not significantly affect the docosahexaenoic acid (DHA) content in pectoral muscle (p > 0.05), with the highest value observed at the 6% inclusion level. In conclusion, dietary flaxseed supplementation effectively enriches ω-3 PUFAs in chicken meat while simultaneously enhancing metabolic health indicators and improving meat quality traits.