Animal Residue Data Sheet - Terbutryn

Terbutryn is registered in Australia for use on wheat, barley, triticale, oats, pasture, peas and sugarcane. Details of the registered use patterns can be found on the approved labels of registered products containing terbutryn as the active constituent. This Animal Residue Data Sheet provides information on the possible residues in feed commodities obtained from crops treated with terbutryn. It also provides information on the anticipated maximum dietary exposure of animals fed treated commodities, which should not result in the violation of animal MRLs.

Current MRLs

The Australian MRLs for terbutryn in food and animal feed commodities, as listed in Table 1 and Table 4 of the MRL Standard (as at June 2003) are shown below. The residue definition of terbutryn is the parent compound per se.

Code	Food	MRL, mg/kg
Food Commodities
GC 0080	Cereal grains?	*0.1
VP 0063	Peas	*0.1
GS 0659	Sugar cane	*0.05
Animal commodities
MO 0105	Edible offal (mammalian)	3
PE 0112	Eggs	*0.05
PO 0111	Poultry, Edible offal of?	*0.05
PM 0110	Poultry meat	0.1
MM 0095	Meat [mammalian]	0.1
ML 0106	Milks	0.1
Animal feed commodities
	Forage, straw and fodder (straw) of cereal grains	30
	Pastures (mixed grasses/leguminous)	75
	Field pea forage and fodder	30

Summary of maximum feeding levels and livestock dietary intakes

The Maximum Feeding Level (MFL, the feeding level at which the MRLs are based), the equivalent Daily Dietary Intake For Livestock (DDIL) and the equivalent daily intake of terbutryn are summarised below.

Species	MFL, ppm in diet	Equivalent DDIL, mg/kg bw	Equivalent intake of terbutryn, mg/animal/day
Cattlea	60	2.4	1200
Sheepb	60	2.5	150
Pigc	60	2.5	150
Poultryd	50	3	0.45
a Based on a 500 kg animal consuming 20 kg DM/day b Based on a 60 kg animal consuming 2.5 kg DM/day c Based on a 60 kg animal consuming 2.5 kg DM/day d Based on a poultry feeding study

Detailed information

All feed commodities

Feed commodities that may contain residues of terbutryn are listed in the table below. The theoretical maximum proportion of the diet that the commodity can comprise, when residues are present at the MRL, without the significant risk of animal commodity MRLs being violated is also given. It should be noted that the feeding levels assumed by the NRA when setting animal commodity MRLs are theoretical values, and they should not be taken as recommendations of appropriate rations for livestock.

Commodity a	Assumed Maximum proportion of diet (%)b	Feed intake (kg/animal/day)c	MRL (mg/kg) d	Maximum intake of terbutryn from commodity (mg/animal/day)e	Theoretical maximum proportion of diet (%)f
Cattle (Based on a 500 kg animal consuming 20 kg DM/day)
Cereal grain	100	20	*0.1	2	100
Forage, straw and fodder of cereal grains	100	20	30	600	100
Pastures (mixed grasses/ leguminous)	100	20	60g	1200	100
Field pea forage and fodder	100	20	30	2	100
Field peas	100	20	*0.1	2	100
Sheep (Based on a 60 kg animal consuming 2.5 kg DM/day)
Cereal grain	100	2.5	*0.1	0.25	100
Forage, straw and fodder of cereal grains	100	2.5	30	75	100
Pastures (mixed grasses/ leguminous	100	2.5	60g	150	100
Field pea forage and fodder	100	2.5	30	75	100
Field peas	100	2.5	*0.1	0.25	100
Pigs (Based on a 60 kg animal consuming 2.5 kg DM/day)
Cereal grain	100	2.5	*0.1	0.25	100
Field peas	100	2.5	*0.1	0.25	100
Poultry (Based on a 2 kg animal consuming 120 g DM/day)
Cereal grains	100	0.12	*0.1	0.012	100
Field peas	100	0.12	*0.1	0.012	100
a The feed commodities that may contain residues of terbutryn, and may form more than 20% of an animals diet. b The maximum % of the diet that the commodity is assumed to comprise for the purposes of setting MRLs, based on Stockfeed Information Document 1 c The equivalent amount of feed for an animal of designated weight and feed intake that is assumed for the purposes of setting MRLs d The MRL for each feed commodity (correction for dry weight basis where required) e The maximum intake of terbutryn when the commodity is fed at the maximum assumed level (Column 1) in the absence of other sources of terbutryn. f The maximum % of the diet at which the commodity could theoretically be fed without significant risk of exceeding animal commodity MRLs. It is assumed that the residue in the feed commodity is present at the MRL (or dry weight equivalent) and other dietary sources of terbutryn are absent. g The highest terbutryn residue on pasture treated at 1.2´ the label rate was 60 mg/kg on a dry weight basis. Residue levels of 50 mg/kg were estimated when scaled for application rate. On this basis, a residue level of 60 mg/kg is appropriate for determining terbutryn intake from pasture.

Abbreviations and definitions

DM: Dry matter. The feed consumption for livestock and the residue levels in feed commodities are expressed on a dry matter basis.

DDIL: Daily Dietary Intake for Livestock. The level of dietary exposure for a specified chemical in a specified species that should not result in exceedance of the relevant animal commodity MRLs. Expressed in mg chemical/kg bodyweight.

MFL: Maximum Feeding Level. The level of dietary exposure for a specified chemical in a specified species that should not result in exceedance of the relevant animal commodity MRLs. Expressed in terms of ppm in the feed.

MRL: The concentration of a chemical residue, in units of mg/kg, that is legally permitted in or on a food or food commodity.

ppm in the feed: Parts per million in the feed. An alternate way of expressing the level of dietary exposure for a chemical. The level of chemical intake is calculated as though it were present uniformly in the total feed intake. The ppm in the feed is calculated using the following formula: DDIL (mg chemical/kg bw) _ body weight (kg) ¸ daily feed intake (kg).

STMR-P: Supervised Trial Median Residue of the processed commodity. The highest residue that livestock are likely to be exposed to in practice when fed processed commodities over a prolonged period. This is derived from the STMR of the whole commodity multiplied by the processing factor.

Attachment 1: Anticipated maximum dietary exposure

The following calculations outline the theoretical diet used to calculate the maximum anticipated dietary exposure, maximum feeding level (MFL) and the daily dietary intake for livestock (DDIL) for cattle, sheep, pigs and poultry.

Cattle

Feed group	Feed commodity	% in the diet	Feed intake, kg/animal/daya	MRL, mg/kg	% DMb	Intake of terbutryn, mg/animal/dayc
Cereal Grains	Grain	100	20	*0.1	-	2
	Forage, straw and fodder	100	20	30	-	600
Pasture	Grass/leguminous pasture	100	20	60d	-	1200
Pulses/legumes	Field peas	100	20	*0.1	-	2
	Field pea forage and fodder	100	20	30	-	600
Total		100	20			1200
aBased on assumed feed consumption of 20 kg dry matter/day bEstimate of percentage dry matter. Applied to MRLs expressed on a fresh weight basis cBased on assumed bodyweight of 500 kg dThe highest terbutryn residue on pasture treated at 1.2´ the label rate was 60 mg/kg on a dry weight basis. Residue levels of 50 mg/kg were estimated when scaled for application rate. A residue level of 60 mg/kg is appropriate for determining terbutryn intake from pasture.

Maximum anticipated dietary exposure:	1200 mg/animal/day
equivalent to:	2.4 mg/kg bw
equivalent to:	60 ppm in the diet
MFL (Based on the available animal ? feeding data (Attachment 2)):	60 ppm in the diet
equivalent DDIL:	2.4 mg/kg bw

Sheep

Feed group	Feed commodity	% in the diet	Feed intake, kg/animal/daya	MRL, mg/kg	% DMb	Intake of terbutryn, mg/animal/dayc
Cereal Grains	Grain	100	2.5	*0.1	-	0.25
	Forage, straw and fodder	100	2.5	30	-	75
Pasture	Grass/leguminous pasture	100	2.5	60d	-	150
Pulses/legumes	Field peas	100	2.5	*0.1	-	0.25
	Field pea forage and fodder	100	2.5	30	-	75
Total		100	2.5			150
aBased on assumed feed consumption of 2.5 kg dry matter/day bEstimate of percentage dry matter. Applied to MRLs expressed on a fresh weight basis cBased on assumed bodyweight of 60 kg dThe highest terbutryn residue on pasture treated at 1.2´ the label rate was 60 mg/kg on a dry weight basis. Residue levels of 50 mg/kg were estimated when scaled for application rate. A residue level of 60 mg/kg is appropriate for determining terbutryn intake from pasture.

Maximum anticipated dietary exposure:	150 mg/animal/day
equivalent to:	2.5 mg/kg bw
equivalent to:	60 ppm in the diet
MFL (Based on the available animal ? feeding data (Attachment 2)):	60 ppm in the diet
equivalent DDIL:	2.5 mg/kg bw

Pigs

Feed group	Feed commodity	% in the diet	Feed intake, kg/animal/daya	MRL, mg/kg	% DMb	Intake of terbutryn, mg/animal/dayc
Cereal Grains	Grain	100	2.5	*0.1	-	0.25
Pulses/legumes	Field Peas	100	2.5	*0.1	-	0.25
Sugar	Sugar	20	0.5	*0.05	-	0.025
Total		100	2.5			0.25
aBased on assumed feed consumption of 2.5 kg dry matter/day bEstimate of percentage dry matter. Applied to MRLs expressed on a fresh weight basis cBased on assumed bodyweight of 60 kg

Maximum anticipated dietary exposure:	0.25 mg/animal/day
equivalent to:	0.004 mg/kg bw
equivalent to:	0.1 ppm in the diet
MFL (Based on the available animal ? feeding data (Attachment 2)):	60 ppm in the diet
equivalent DDIL:	2.5 mg/kg bw

Poultry

Feed group	Feed commodity	% in the diet	Feed intake, kg/animal/daya	MRL, mg/kg	% DMb	Intake of terbutryn, mg/animal/dayc
Cereal Grains	Grain	100	0.12	*0.1	-	0.012
Pulses/legumes	Field Peas	100	0.12	*0.1	-	0.012
Total		100	0.12			0.012
aBased on feed consumption of 0.120 kg dry matter/day bEstimate of percentage dry matter. Applied to MRLs expressed on a fresh weight basis cBased on bodyweight of 2 kg

Maximum anticipated dietary exposure:	0.012 mg/animal/day
equivalent to:	0.006 mg/kg bw
equivalent to:	0.1 ppm in the diet
MFL (Based on the available animal ? feeding data (Attachment 2)):	50 ppm in the diet
equivalent DDIL:	3 mg/kg bw

Attachment 2: Residue data

The residue definition of terbutryn in Australia is the parent compound per se.

Selected residue data for animal feed commodities

Terbutryn residues in Pasture and Wheat

Crop	Location, year	Rate, g ai/ha	No.	Volume, L/ha	Commodity	PHI, days	% DM	Terbutryn, mg/kg DM
Pasture	NSW, 1988	425	1	89	-	7	25	28-60
					-	14	25	3.5-14
	VIC, 1988	425	1	115	-	0	25	264
					-	7	25	28-60
					-	14	25	3.52-9.6
Wheat	NSW, 1988	600	1	123	Whole plants	0	25	200-300
						7	25	3.08-4.4
						14	25	0.76-1.08
	VIC, 1988	600	1	70	Whole plants	0	25	168-200
						7	25	13.2-18
						14	25	1.72-3.04
	England	500				270		<0.1
	USA	500			Green parts	187		<0.05
						190		<0.05
					grains	267		<0.05
		750			Green parts	166		<0.05
						168		<0.05
						211		<0.05
					grains	256		<0.05
	Switzerland	670			straw, grains	129		<0.05

Selected animal transfer data

Lactating cows — milk

Lactating cows were dosed orally for 21 consecutive days with terbutryn at levels equivalent to 100, 200 and 400 ppm in the diet.

Terbutryn residues in milk of cows treated with terbutryn for 21 consecutive days.

Treatment (ppm in the feed)	Terbutryn residues (mg/kg) at days shown
	pre	7	14	21	23
100	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01
200	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01
400	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01

Terbutryn residues in butter produced from the milk of cows treated with terbutryn for 21 consecutive days

Treatment (ppm in the feed)	Terbutryn residues (mg/kg) at days shown
	pre	21	28
100	<0.01 <0.01	<0.01 <0.01	- -
200	<0.01 <0.01	0.01 <0.01	<0.01 <0.01
400	<0.01 <0.01	0.02 0.03	<0.01 <0.01

Laying Hens

Laying hens were dosed orally for 21 consecutive days with terbutryn at levels equivalent to 50 ppm in the diet.

Residues of terbutryn in tissues following 21 consecutive daily doses

Time (days) from commencement of exposure		Terbutryn residues (mg/kg)
	chicken no.	muscle	liver	fat
9	control	<0.01	<0.01	<0.01
7	19 20	<0.01 <0.01	<0.01 <0.01	0.01 0.01
14	17 18	<0.01 <0.01	<0.01 <0.01	0.07 0.05
21	1 2	<0.01 <0.01	<0.01 <0.01	0.06 0.03
23	3 4	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01
28	5 6	<0.01 <0.01	<0.01 <0.01	<0.01 <0.01

Residues of terbutryn found in eggs collected from hens treated with 50 ppm terbutryn in the feed.

Time (days) after commencement of exposure	rep.	Terbutryn Residues (mg/kg)*
		Treated	control
3	1 2	<0.01 <0.01	<0.01 <0.01
7	1 2	<0.01 <0.01	<0.01 <0.01
10	1 2	<0.01 <0.01	- -
14	1 2	<0.01 <0.01	<0.01 <0.01
17	1 2	<0.01 <0.01	- -
21	1 2	<0.01 <0.01	<0.01 <0.01
23	1 2	<0.01 <0.01	- -
28	1 2	<0.01 <0.01	- -