Cattle

Cattle. Three studies were reported. The first two were of the distribution of radioactivity, one from a topical application and the second from i.v. administration. The third was a continuation of the i.v. study for the identification and quantification of the residues.

In the first study (Cameron and Phillips, 1986), in accordance with GLP principles, a single dose of 938.5 mg (6.56 mCi) of formulated [U-fluorophenyl-¹⁴C]flumethrin was applied by syringe to a 60 cm x 15 cm section along the spine of a 530 kg lactating Friesian dairy cow (1.8 mg/kg bw). The GAP rates for pour-on applications are 1.8-3.6 mg/kg bw (generally <2.5 mg/kg bw) and for spray applications approximately 1.5-2 mg ai/kg bw. Milking was by machine twice daily, and blood samples were taken at frequent intervals until slaughter 48 hours after treatment. Samples were taken of liver, kidney, perirenal fat, subcutaneous fat (beneath and away from the dose area) and muscle at different sites, as well as of bile and bladder urine. All samples were stored at -20°C until analysis for total radioactivity by liquid scintillation counting.

Residues in the plasma peaked at 6.3 ng flumethrin equivalents/ml after 23 hours, slowly decreasing thereafter. No radioactivity was detected in the milk on the first day after treatment but 1, 3 and 2 ng equivalents/ml were reported at the first and second milkings on the second day and the first milking on the third day respectively. The levels of radioactivity in other samples are shown in Table 1.

Table 1. Total radioactivity in tissues and fluids of a lactating cow 48 hours after topical administration of fluorophenyl-labelled [¹⁴C]flumethrin at 1.8 mg/kg bw (Cameron and Phillips, 1986).

Sample		14C, ng flumethrin equivalent/g or ml
Whole blood		2
Plasma		4
Liver		9
Kidney		10
Renal fat		2
Subcutaneous fat
	below dose area	0 (<7.7 ng equiv./g)
	away from dose area	0 (<7.7 ng equiv./g)
Skeletal muscle
	fore leg	0(<3.9 ng equiv./g)
	rump	0(<3.9 ng equiv./g)
	dorsal	0(<3.9 ng equiv./g)
	cheek	1(3.9 ng equiv./g limit of determination)
Bile		70
Bladder urine		281
Application area (surface wash and solubilized skin)		4.7 mCi = 71.5% of administered dose

In the second study, also in accordance with GLP, [U-chlorophenyl-¹⁴C]flumethrin (98.2% pure by TLC, 96.3% by HPLC) was formulated as a solution (specific activity 9 mCi/mg) and administered as a single i.v. dose into the jugular veins of both a lactating cow (545 kg) and a steer (340 kg) at a nominal rate of 1 mg ai/kg bw (Gifford and Dunsire, 1994). The integrity of the dose solution was confirmed by TLC after dosing. Urine, milk and faeces samples were taken until slaughter 8 hours after treatment and milk also just before dosing. Tissue samples were taken at slaughter and all samples were transported under dry ice and stored at -20°C until analysed. Total ¹⁴C was determined by liquid scintillation.

The cumulative recovery of ¹⁴C is shown as a proportion of the administered dose is summarized in Table 2 and as flumethrin equivalents/kg in the milk, blood and tissues in Table 3.

Table 2. Recovery of radioactivity from [¹⁴C]flumethrin 8 hours after administration of a single intravenous dose to cattle at 1 mg ai/kg bw (Gifford and Dunsire, 1994).

Sample			14C, % of injected
			Dairy cow	Steer
Urine			4	8
Faeces			0.03	0.35
Milk			0.32	NA
Tissues
	liver		21.13	4.4
	kidney		0.22	0.28
	muscle		7.13*	6*
	fat		3.1*	2.5*
		Total	31.6	13.2
Total			35.9	21.5

* Assumes muscle and fat account for 30% and 20% of body weight respectively.

Table 3. Residues of ¹⁴C as flumethrin equivalents 8 hours after administration of a single intravenous dose of [¹⁴C]flumethrin to cattle at 1 mg ai/kg bw (Gifford and Dunsire, 1994).

Sample			14C as flumethrin, mg/kg
			Dairy cow	Steer
Milk			0.3	NA
Liver			13	3.4
Kidney			0.9	1.4
Muscle - loin			0.19	0.18
		- flank	0.25	0.19
		- round	0.30	0.23
Fat - subcutaneous			0.17	0.24
	- omental		0.37	0.19
Whole blood			15	1.8
Plasma			2.2	2.8

The third study (Klein, 1995), also in accordance with GLP, was a continuation of the 1994 study of Gifford and Dunsire described above, with the objective of identifying and quantifying the residues in the edible tissues and milk. Identifications were based on the characterization and fractionation of urinary extracts by HPLC, followed by GC-MS and NMR spectrometry. One HPLC fraction was shown by MS and NMR to contain the glucuronic acid conjugate of metabolite BNF 5533A. The identification was confirmed by the detection of BNF 5533A in glucuronidase/arylsulfatase hydrolysates of the conjugate. Another major urinary component was shown by GC-MS and NMR after methylation to be unconjugated BNF 5533A.

Samples of loin, flank and round muscle and of omental and subcutaneous fat were composited for each animal before extraction for analysis. Tissues were extracted with acetonitrile/water, and the extracts concentrated and partitioned with n-heptane. The heptane fractions were concentrated, taken up in acetonitrile and analysed by HPLC. The aqueous fractions were diluted with water, adjusted to pH 3 (except liver extracts) and partitioned with acetonitrile which was concentrated for HPLC. Milk was extracted with methanol and the residues were partitioned into heptane: only the heptane fraction was analysed as it contained 89% of the radioactivity. Residues were quantified by HPLC with integration of ¹⁴C signals, and identified by comparison with reference standards in two HPLC systems. Table 4 shows the efficiencies of extraction of from the milk and tissues and the levels of ¹⁴C found. Table 5 shows the levels and percentages of the identified compounds.

Table 4. Concentrations and extractable proportions of total radioactivity in milk and tissues of cattle 8 hours after i.v. administration of [¹⁴C]flumethrin at 1 mg/kg bw (Klein, 1995).

Sample	14C
	Dairy Cow		Steer
	Flumethrin equivalent, mg/kg	Extractable, %	Flumethrin equivalent, mg/kg	Extractable, %
Liver	13	96	3.4	92
Kidney	0.9	92	1.4	90
Muscle	0.25	87	0.2	87
Fat	0.27	78	0.22	88
Milk	0.34	89	-	-

Table 5. Distribution of ¹⁴C in flumethrin and metabolites in milk and tissues of a lactating dairy cow and steer 8 hours after i.v. administration of [¹⁴C]flumethrin at 1 mg/kg bw (Klein, 1995).

Sample		Component or fraction				Total % and mg/kg as flumethrin in sample
		Flumethrin	BNF 5533A	BNF 5533A glucuronide	Unknown
Liver (cow)	%	87.1	7.0	1.0		95.1
	mg/kg	11.31	0.91	0.13		12.4
Liver (steer)	%	28.9	39.9	7.2		76
	mg/kg	0.97	1.34	0.24		2.6
Kidney (cow)	%	35.1	47.4	5.7		88.2
	mg/kg	0.31	0.42	0.05		0.8
Kidney (steer)	%	15.5	46.5	24.8		86.8
	mg/kg	0.22	0.66	0.35		1.2
Muscle (cow)	%	29	57.5			86.5
	mg/kg	0.07	0.14			0.2
Muscle (steer)	%	35.9	51.1			87
	mg/kg	0.07	0.1			0.2
Fat (cow)	%	23.8	54.5			78.3
	mg/kg	0.06	0.15			0.2
Fat (steer)	%	27.8	59.8			87.6
	mg/kg	0.06	0.13			0.2
Milk (cow)	%	67.9			11.5	67.9
	mg/kg	0.23			0.04	0,2