This experimental work reproduces the fipronil extra-label administration performed by producers in laying hens. The scientific goal was to characterize the residual concentrations in eggs from treated hens and suggest the withdrawal periods that should be respected to avoid risk for consumers. Thirty-four laying hens were allocated into two groups: Group A was treated with fipronil in feed, two single doses of 1 mg kg⁻¹ day⁻¹; Group B was administered a single dose of 1 mg kg⁻¹ by the topical route. Fipronil egg residues were quantified by HPLC-MS/MS. Fipronil and its sulphone metabolite (fipronil-SO₂) were measured in egg after both treatments. The highest egg residual profile was always for fipronil-SO₂. Mean maximum egg concentrations (C_max) of 228.5 ± 79.8 ng/g (fipronil) and 1,849 ± 867 ng/g (fipronil-SO₂) were found after fipronil administration in feed. The lowest residual levels were quantified after the topical treatment with C_max of 27.1 ± 4.9 and 163 ± 26 ng/g for fipronil and fipronil-SO₂. Mean fipronil marker residues and established MRLs allowed calculating the withdrawal periods, the shortest being 74 days after topical administration. Such a long withdrawal period is difficult to meet in egg production systems. Thus, the extra-label use of fipronil in laying hens should not be recommended under any circumstances.

中文翻译：

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氟虫腈对蛋鸡的口服和局部标签外给药：鸡蛋残留模式的评估

这项实验工作再现了生产者在蛋鸡中进行的氟虫腈超标给药。科学目标是表征处理过的母鸡的鸡蛋中的残留浓度，并建议应遵守的停药期以避免消费者面临风险。34 只蛋鸡被分为两组：A 组在饲料中加入氟虫腈，两次单剂量 1 mg kg ^-1 天^-1；B组通过局部途径给予单剂量1mg kg ^-1。氟虫腈鸡蛋残留量通过 HPLC-MS/MS 进行定量。两种处理后在鸡蛋中测定氟虫腈及其砜代谢物（氟虫腈-SO ₂）。氟虫腈-SO _{2 的}卵子残留量最高. 在饲料中使用氟虫腈后发现平均最大鸡蛋浓度 (C _max ) 为 228.5 ± 79.8 ng/g (fipronil) 和 1,849 ± 867 ng/g (fipronil-SO ₂ )。在局部治疗后量化最低残留水平，氟虫腈和氟虫腈-SO _{2 的}C _{max 分别}为 27.1 ± 4.9 和 163 ± 26 ng/g 。平均氟虫腈标记物残留和确定的 MRL 允许计算停药期，最短的是局部给药后 74 天。如此长的停药期在产蛋系统中是难以满足的。因此，在任何情况下都不建议在蛋鸡中额外使用氟虫腈。