GB2341093A - Pesticide dip preparation - Google Patents

Abstract

A method of preparing a dip of pesticide dipwash dipping a herd of animals of the same species so as to reduce the incidence of overdosing and underdosing, the method including:<BR> ```providing a plurality of treatment categories for animals, the categories each defining a range in the volume of dipwash removed by an animal;<BR> ```assigning animals to the treatment categories based on the anticipated volume of dipwash removed by each animal within the herd;<BR> ```providing an initial pesticide concentration of dipwash for each category for providing effective pesticidal control in the dip for animals of said catgegory;<BR> ```providing a second pesticide concentration for each category for replenishing dipwash removed from the dip to maintain an effective concentration of pesticide in the dip.

Description

j 2341093 IMPROVEMEMCS IN AND RELATING TO THE DIPPING OV ANI -

FIELD

This invention relates to the application of pesticides to animals particularly sheep, cattle, goats, other cloven hoofed animals and domestic pets by dipping or theorise saturating the outer surface of the animal with a pesticidal composition.

BACKGROUND

Dipping of sheep:'tind cattid is--- an -inexpensive 'method of controlling a wide range of ectoparasites. The process -"of'dipoi'n'd g-nimals consists of wetting of their external regions with -ist;i-cidal composition. 'Wetting- is achieved either by complete immersion of the animal in pesticidal liquor (a process referred to as plunge dipping), or by exposing the animal to a shower or spray of appropriately diluted pesticide (a process referred to as shower dipping).

is As animals pass through a dipping station, dipwash is retained inlon the surface regions of the animal and is removed from the sump. The removed dipwash must be replenished, and a particularly convenient method of replenishment of dipwash is the method of constant replenishment, which has been described in our previous application (Australian Patent Application No 19946197 and US Patent Application Serial No. 091052,394 filed 31 March 1998.

A dipping station operated under constant replenishment conditions is characterized by the use of an initial charge of pesticide in the sump (said charge having a concentration of pesticide denoted CIC), and is further characterized by the use of a constant replenishment charge of pesticide to the dipwash (said charge having a concentration of pesticide denoted CCR).

In traditional constant replenishment dipping'practice, CIC is set at or close to the same value as CCR- Pesticide in a dipwash commonly has a higher affinity for the surface of the animal than for dipwash. The resultant transfer of pesticide from dipwash to the animal surface is referred to as stripping, and is generally considered to be based on lipophilic interaction.

Although the volume of dipwash is maintained by the process of continuous replenishment charging, the effect of stripping in a dipping operation wherein CIC = 2 CCR is that the concentration of pesticide in the dipwash progressively decreases until a steady state concentration CSS is reached. At steady- state the relationship CIC =SF x CSS (1) applies, where SF is.the stripping factor. SF can be calculated in a variety of ways as described in our previous application. In general, SF depends on (a) the nature of the active ingredient; (b) the_nature, o,f. the formulation comprising the active ingredient, and in particular the nature of the solvent. in the said formulation,. if the active ingredient is maintained in the dipwash as an emulsion; (c) the dipping method (plunge or shower dip); and (d) the sump volume of the dipping station, or some other factor(s) highly correlated with sump volume. These related factors presumably could include features of dip operation that influence degree of exposure of the dipping liquid (active ingredient) to the stripping effect of the animal surfaces (eg. length of the bath, swim distance andlor time in plunge dips and showedrig time pressure, nozzle type and sump turnover in shower dips).

As an example of the dependence of stripping factor on dipping conditions, it may be noted that the diazinon formulation sold under the trade name Diprite (Nufarm Ltd) usually has a stripping factor in range of 3-6 for small (< 4000 Litre) sump plunge dips and for small (< 500 Litre) sump shower dips. The same formulation usually has a stripping factor of 6-12 in large (> 4000 Litre) sump plunge dips and large (>500 Litre) sump shower di.Ps.

From equation 1, the implication of a large stdpping factor (eg. SF = 12) is that the concentration of active ingredient in the dip at early times (CIC) can be 12 times greater than the concentration of active ingredient in this dip at later times. This condition will lead to either of the following undesirable consequences:

(a) the sheep dipped first will be overdosed or 3 (b) the sheep dipped last (during the steady state regime) may be underdosed.

Some active ingredients, (eg. lvermectin and other macrocylic iactones) 5 have much higher stripping factors and these actives cannot be usefully applied at all using conventional dipping methodology.

Constant replenishment dips are normally run using a concentration of initial charge (C1c) which equals the "concentration of the replenishment charge (CCR) and heterogeneity of thúidcitb 'applied due ' to stripping will gen efrally be a problem.

Our previous --application provides a method for operating coinstant replenishment dips under near steady state conditions for the entirety of the dipping operation.

This is achieved by (a) establishing a concentration of pesticide which provides a safe and effective pesticide treatment. This concentration (C1c) is initially charged to the sump, and (b) maintaining the volume of dipwash by addition thereafter of a composition containing a second concentration _of pesticide, CCR where CCR is greater then Cic and is obtained from the relationship - -SF x- CIC ---1 (3) CCR 19946197 provides detailed instructions for evaluating the stripping factor SF required in (3). For a high-stripping diazinon situation with SF = 12, the replenishment concentration CCR established from equation (3) is twelve times greater than the initial concentration CIC.

4 Since the process of our previous application provides for a more constant concentration of pesticide in the dipwash throughout the entire dipping operation, the consistency of dosing Js...vastly improved compared with conventional dipping processes.

However despite the achievement of a more constant concentration of pesticide in the dipwash, we have found that the delivery of an optimal dose of pesticide to each animal in a heterogeneo, us group remains problematic. For instance, for large dips (diazinon, mering sheep) the stripping --factor SF can lie anywhere in the range 6-.12,,and we have. found by experiment thatsmall, shor,t-Wool-,.

merino sheep need, at the very least,:2-10mg diazinon per.head for effective lice_ control. For these small, short-wool sheep the volume of dipwash removed VIR can.

lie anywhere in the range 0.8 -1.2 litres per sheep. Using the procedure of our previous application it may be established that given the above range of SF and VIR, the minimum initial concentration (CIC) of diazinon required to provide an acceptable dose in all circumstances (take for the extreme case SF = 6, VIR = 0.8) is 44 mg per litre in dipwash. However under these conditions (CIC = 44 mg per litre), large long-wool sheep (VIR in range 4.6 - 6.5) could received a dose of up to 2432 mg diazinon per head (take for the extreme case SF = 12, VIR = 6.5). This represents substantial overdosing.

By decreasing the pesticide concentration in the dipwash, acceptable doses can be delivered to the large long-wool sheep. If this is done however, the dose of pesticide applied to small short wool sheep is too low to provide effective louse control.

No prior art dipping procedures apparently address the different dose requirements of animals having different physical characteristics.

SUMMARY OF THE INVENTION

We have found that by segregating the. animals of a diverse herd into dose specific categories based on the volume of dipwash removed by an animal VIR. and by using different values for the concentration of the initial charge CIC and the replenishment charge CCR for each dose-specific category it is possible to reliably achieve target pesticide dose ranges for all animals.

Accordingly we provide a method of dipping a herd of animals of the same species in a dip containing pesticide dipwash to reduce the incidence of overdosing and underdosing, the method including:

providing a plurality of treatment categories for animals, the categories each defining a range in the volume of dipwash removed by an animal; assigning animals to the treatment categodes based on the anticipated volume of dipwash removed by each animal within the herd; providing an initial pesticide concentration of dipwash for each-category for providing effective pesticidal control in the dip for animals of said catgegory; providing a second pesticide concentration -for each category for replenishing dipwash removed from the dip to maintain an effective concentration of pesticide in the dip.

This method may involve dipping sheep of at least one said category and preferably at least two categories in the respective first concentration for said category or categories; and replenishing the dipping liquid removed with the respective second concentration for said category.

There should be provided at least 2 dose-specific categories based on VIR preferably at least 3 categories. The ranges will generally be mutually distinct ranges.

In relation to the dosing of pesticide on merino sheep, an appropriate set of dose-specific categories denoted A-E can be established according to the following table.

Table 1: Categorisation of merino sheep on the basis of volume of dipwash removed per head (VR) Dose- Volume of dipwash specific removed VIR (Litrelhead) Category A 0.8-1.3 B 1.3-2.1 c 2.1-3.1 D 3.11-4.6 E 4.6-6.5 6 The volume of dipwash removed by a merino sheep is generally taken to be the volume of dipwash remaining on the animal after 5::minutes draining. This quantity may be established by weighing the animals after the set drainage time or by collection and measurement of the volume of drainage water from sheep after dipping as outlined in Example 6 of this application.

For other animals (i.e. non-merino sheep), categories can be chosen in an analogous way by measuring volume removed VIR -and dividing the range Of VIR:1 values into intervals, each such interval corresponding to a given category.

We have found that in -sep, there is a g(Qd correlaticm betweenthe volume removed VIR and the product 0 f bddyweight (kg)-a5d time off-shears (Weeks) for sheep dipped within the normal interval of 2 to 6 weeks after shearing.

Accordingly in a particularly preferred embodiment the invention provides a method of dipping a herd of animals of the same species in a dip containing a pesticide dipwash to reduce the incidence of overdosing and underdosing the method including:

providing a plurality of treatment categories for the animals, each category defining a distinct range in the product of bodyweight and time since shearing; grouping animals which fall into the same category of the product of bodyweight and time since shearing; providing an initial pesticide concentration for each category for providing effective pesticidal control of sheep in said category; and providing a second pesticide concentration for each category for replenishing dipwash, the second concentration being sufficient to compensate for the effect of stripping of pesticide from the initial concentration during dipping of animals of said category.

In a preferred embodiment the invention will include separately dipping each category of animals using a dip containing pesticide of the corresponding initial concentration for the category and during the dipping process replenishing dipwash removed by animals with the second pesticide concentration for the category.

In the drawings Figure 1 shows the relationship between the product of the body weight and time-off shears and the volume of body weight and time-off shears and the volume of dipwash removed per animal as determined in field trials.

7 Figure 2 shows the relationship between diazinon concentration and the volume of dipwash removed during a conventional dipping procedure of Example 1.

The correlation -between. VR and the product of bodyweight (Kg) and timeoffshears (weeks) for merino sheep is summarized in Table 2 and in quantitative terms 5 in Figure 1 of the drawings.

Table 2: Relationship Of VR to the product of bodyweight and time since shearing (generally referred to in the art as time off-shears).

Dose-.. Range in %folifrfid: Ekdyweight (kg) x specification of dipwash time off-shears category removed (weeks) rang e (VR, Uhead) (kg week) A 0.8 1.3 40-80 B 13-2.1 >80 - 120 c 2.11-3.1 >1 20 - 170 D 3.11-4.6 >1 70 260 E 4.6-6.5 > 260 Mean of values derived from field trials with plunge and shower dips.

The near linear relationship shown in Table 2 and Figure 1 permit the allocation of groups of sheep into dose specific categories based on their body weight and time off-shears. In order to facilitate the allocation, use can be made of a formate shown in Table 3, which presents essentially the same information in a more user-friendly form.

Table 3: Allocation of Categories Weight Time 6ff-sheafs (weeks) kg 0.5-2 2-4 4-6 0-30 A B c 30-45 B c D 45-60 B D E 60-75 c E E 8 For non-sheep animals, an analogous procedure can be devised whereby the various VR categodes can be correlated (using standard methodology) against some set of available physical parameters, for example parameters chosen from the set consisting of breed, coat density, fibre diameter, fibre length, bodyweight, age, time off-shears etc.

Once an animal has been allocated into a dose specific category (i.e. into an interval of the parameter VR), R ispossibie by experiment-to establish an acceptabte dose range. This acceptable dose range is expressed in mg/head for each category.

For the case of merino sheep treated with a diazinon formulation ("DIPRITE" Nufarm Ltd Diazinon 5OOg/L), the experimentally determined acceptable dose range is provided in Table 4.

Table 4: Target dose range acceptable dose range) Category Dose Range mgfhead A 210-780 B 260-975 c 302-1134 D 347-1302 E 442-1652 Merino sheep, Diprite formulation For cases other than the merino sheep and DIPRITE (diazinon formulation) scenario, an analogous table can be established by experiment.

Given the target dose range (eg. Table 4) and the volume removed range (eg. Table 1) for each category, it is possible, for a given range of stripping factors (corresponding to a range of sump volumes of dips and dipping methods), to find values of the initial charge concentration CIC and the constant replenishment charge concentration CCR in each category which ensures that animals in each category 9 are all adequately dosed as defined in Table 4 (or its equivalent) under near steady state conditions for the enfire dipping operation.-The relevant equations (which are justified in 19946197) are d-=Cle x SF x VIR ---(4)-- - and CCR = CIC x SF (5) where d represents dose.

Table Sa shows values of CIC and CCR for the categories A to E for menno sheep treated with Diprite formulatiori in large -dips in 'range 6-12). Table 5b shows corresponding information for small dips (SF in'range 3-6). It is apparent from - Tables 5a and 5b that the method of the current invention enables acceptable dose targets to be closely achieved for each category. Most importantly, the invention enables avoidance of under-dosing or undue overdosing.

Table Sa - Large Dips (SF = 6-12) Use of Current Invention of Delivery o Appropriate Doses of Diazinon to Merino Sheep Category VIR CIC CCR Achieved Achieved Target Acceptable range Dose Dose Dose Dose range Uhead mg/L mg/L (min) (max) mg/head mg/head mg/head mg/head A >0.8 - 50 325 240 720 260 210-780 1.2 B >1.2 - 37.5 250 270 900 325 260-975 2 C >2 - 3 30 180 -360 1080- 378 302 - 1-134 D >3 - 22.5 140 405 1215 434 347-1302 4.5 E >4.5 - 17.5 120 473 1365 552 442-1656 6.5 mass balance based on lowest SF in the range, VR at minium of range mass balance based on highest SF in the range, VR at maximum of range Table 5b - Small Dips (SF _= 3 - 6) Use of Current Invention of Delive!y o Appropriate Doses of Diazinon to Merino Sheep Category VR CIC CCR Achieved Achieved Target Acceptable range mg/L mg/L Dose Dose Dose Dose Uhead (min) (max) mg/head ran, mg/head mg./head qe mg/head A 0.8-1.2 108 325 258. 778 260 210-780 B 1.2-2 82.5 250 297 -990 325 260-975 C 2-3 60 180 360 1080 378 302-1134 D 3-4.5 47.5 140 428 1283 434 347-1302 _E 4.5-6.5 40 120 540 1560 552 442-165 For cases other than the merinoldiazinon (DIPRITE) scenario, an equivalent process can be used based on (a) experimentally derived target dose ranges (b) provision of dose-specific categories based on volume of dipwash removed (c) correlation of dose-specific categories with available physical parameters of animals to be dipped (d) experimental determination of the relevant stripping factor range.

From a user point of view, much of the information provided in Tables 5a and b is unnecessary - the key user issues are:

establishing the categories for the animals to be dipped (see Table 3) and describing the key operational parameters (C1C and CCR, see Table 6) Table 6: Key operational parameters for dipping merino sheep- Dose Specification Large dips Small dips

Category mg/L mg/L CIC CCR CIC CCR A 50 325 108 325 B 37.5 250 82.5 250 c 30 180 60--- 180 D 22.5 140 47.5. 140 E 17.5 120 40 120 Table 6 shows the key operational parameters from Tables 5a and b (Merino sheep/Diprite scenario). Generally, pesticide dose rates that are effective for merino sheep will be effective for British breed or cross- bred sheep, as the latter types of sheep tend to have greater fleece penetrability. Higher fleece penetration facilitates contact between wool-dwelling ectoparasites and pesticide in the dipping liquid. Specific label instructions for non-merino breeds of sheep could however be developed using the methods of the invention. The units of the CIC and CCR values illustrated are milligrams of pesticide/Litre of dipwash. For field use however these values could be expressed in terms of volume or mass of supplied formulation per unit volume of dipwash or replenishment liquid. Table 7 provides field- use parameters for the DIPRITE diazinon formulation (500g/L diazinon).

12 Table 7 Initial- charge (C1c) and constant replenishment (CCR) concentrations for large and small dips.

as defined in the text As described in our previous application the tendency of pesticide in a dip to sthp can be described by a measure called stripping factor (SF).

SF may be determined for any category by selecting an initial dip concentration (Cle) so that when a sheep is dipped, an effective dose of pesticide is achieved without underdosing or undesirable over-dosing. A second (replenishment) concentration (CCR) may then be selected experimentally, such the CIC is approximately maintained when using the selected CCR during an extended constant replenishment dipping operation using sheep of the same category. SF for the dip will then be equal to the ratio of the CIC to the CCR.

ie. SF = CCR 1 CIC SF may also be determined for each category using the procedures described in our previous patent application.

Dose Specification Large Dips Small Dips

Category (mL Diprite (mL Diprite formulation formulation 110001---of 11000L of dipwash) dipwash) CIC CCR CIC CCR A 100 650 215 650 B 75 500 165 500 c 60 360.120 360 D 45 280 95 280 E 35 240 80 240 1 13 Thus SF may be determined for any category from an independent dipping operation in which animals are dipped in a dipping liquid of the first concentration (CIC) and the volume of dipping liquid is maintained by replenishment with dipping liquid of the first concentration. - Thus if sufficient animals of a category are dipped to allow a steady state concentration of pesticide (CSS) to develop in the dip, the tendency for the pesticide to strip can then be defined by the Stripping Factor (SF), wherein - SF = CICICSS Preferably the dipping liquid of the first concentraflon (CIC) has a Stripping Factor (SF) of at least two and said second concentration (CCR) and said first concentration comply with a relationship wherein that the product of the first concentration (CIC) and the Stripping Factor (SF), divided by the second concentration (CCR) lies in the range 0.2 to 2.0 ie 0.2 < CIC x SFICCR < 2.0 the stripping Factor SF being determined as outlined above. 20 Surprisingly it has been found that to maintain an adequate level of pesticide in the dip, the replenishment concentration has to be at least twice the initial charge of the dip. More preferably CIC x SF/CCR is in the range of 0.5 to 1.5. Most preferably CIC x SF/CCIR will be 0.8 to 1.2. 25 The invention also provides for use of an initial or first concentration of pesticide and an operational dip concentration that provides the animals with a pesticide dose equal to, or within a selected safety margin above, the minimum effective dose (MED). The level of dipping liquid in the vessel may be maintained by continuous 30 replenishment with a mixture of water and formulated pesticide to the sump over all or most of the dipping time. For a plunge dipping station, the process of continuous replenishment leads to the maintenance of the liquid level in sump at a fixed predetermined level when no sheep are in the dip (in practice, variations of less than 20% and preferably less than 10% about the predetermined level can occur). For a 14 shower dipping station, the process of continuous replenishment leads to the maintenance of liquid level in the sump at a predetermined level, with the proviso that said level is measured at a fixed stage of the batch spraying process, and allows for the volume of liquid taken up in the dispensing equipment.

In practice, the method of treatment in accordance with the invention may be represented using a chart, table, graph or equivalent representation for a particular suitable pesticide formulation, in which sump volume (or some factor highly correlated with sump volume) is related simply to an appropriate initial charge concentration of pesticide for the sump and a concentration of pesticide for constant replenishment. Recommended initial charge - and -replenishment concentrations would depend on whether-dipping was being conducted by spray or- plunge, but generally operator instructions relating to the invention may be much simpler than the complex replenishment and reinforcement requirements of traditional dipping practices.

The extent of stripping is quantified by the Stripping Factor. This measure varies with factors including:

(a) the nature of the active ingredient; (b) the nature of the formulation comprising the active ingredient, and in particular the nature of the solvent in the said formulation, if the active ingredient is maintained in the dipwash as an emulsion-, (C) the dipping method (plunge or shower dip); and (d) the sump volume of the dipping station, or some other factor(s) highly correlated with sump volume. These related factors presumably could include features of dip operation that influence degree of exposure of the dipping liquid (active ingredient) to the stripping effect of the animal surfaces (eg. length of the bath, swim distance and/or time in plunge dips, showering time/sump turnover in shower dips).

The Stripping Factor applicable to this invention may be determined by quantifying the extent of stripping observed when for a given formulation of a given active ingredient using a given dipping method and a given sump volume, a dipping operation is carded out wherein the concentration of active ingredient in the initial charge of pesticide added to the sump may equal the concentration of active ingredient in the replenishment charge added to the sump, as in traditional constant replenishment dipping practice. Dipping is continued until an approximate steady state. has developed between pesticide addition and removal. The concentration of pesticide in the dip at this state (CSS) is used to evaluate the tendency for stripping to occur (SF) using the ratio CCR/CSS as previously described. SF will always be greater than 1 where stripping occurs and the larger the value of SF the more prominent is the stripping effect. In order to establish CSS and SF in a category, where insufficient animats: -- --- have been dipped or. are available to be -dipped to allow confirmation that a steady state between pesticide addition and removal has been established, a curve-fitting procedure such as that hereinafter described may be used to approximate both CSS and SF. The stripping factor may also be determined by:

(i) dipping a number of animals in a dipping liquid of initial concentration CIC contained in the vessel and maintaining the level of liquid in the vessel during dipping by replenishment of the liquid removed with a dipping liquid of the first concentration equal to CIC and preparing a graph of concentration of pesticide against numbers of animals.

(ii) generating an array of calculated stripping curves showing the change in concentration of pesticide during dipping for a range of SF values using the formula VA C]C+ C n-1 Vs (Cn) VS + VA SF wherein VS is the volume of dipping liquid VA is the average volume of dipwash removed per animal Cn is the concentration after passage of the nth animal CIC is the first concentration; and comparing the graph determined in step (i) with the array of calculated stripping curves to determine the stripping factor corresponding to the closest fitting calculated stripping curve.

16 The method of the invention may be used with a range of pesticides such as organophosphates) carbarnates, formamidines, - pyrethroids, macrocyclic lactones and insect growth regulators such as the benzolyl phenyl ureas.

The invention may utilise known dipping equipment shown in our previous application.

The invention will now be illustrated with reference to the following nonlimiting Examples.

Example Investigation -of the decline in pesticide concentration. in a plunge dip operated by conventional constant replenishment practice.

Methods Trial Location: Harrow, western district of Victoria, Australia.

Dip type: In ground plunge dip, 3360L capacity Sheep type: Mean liveweight, 35Kg, 3 weeks off-shears Pesticide formulation: Topclip Blue Shield (Novartis Animal Health Australasia Pty Ltd containing diazinon as a 200g/L emulsifiable concentrate (EC). Number sheep dipped: 2865 Dip operation: The formulation was used according to the manufacturer's recommendations for constant replenishment operation (100mg/L diazinon in both the initial charge and the replenishment liquid) 25 RESULTS The data illustrated in Figure 2 was derived by monitoring the concentration of diazinon in dipwash following use of the above formulation in a commercial situation.

CONCLUSION

The concentration of diazinon in the sump of the dip exhibited a rapid but decreasing rate of decline in concentration as an increasing number of sheep were dipped. After sufficient sheep were dipped, a steady state was achieved, whereby the rate of pesticide addition equalled the rate of removal on the dipped sheep. By this stage the dose /head of pesticide received by the dipped sheep equalled the 17 volume of dipwash they removed times the concentration of the replenishment liquid (100mg/L). In this instance, sheep dipped during the steady state part of the dipping operation would have received about 250mg/head (2.5Uhead x 1 00mg/L).

The following examples are included to illustrate that doses of diazinon 5 applied to merino sheep that are below the target doses outlined in Table 4 (including four field trials targeted at the above dose rate of 250mg/head), did not provide reliable control of sheep louse (Bovicola ovis).

Example 2: Lousicidal effect of a 150mg/he.ad of Oi,141non on small sheep.

Trial details Researcher: N. Sherwood, TLC Research Location: Camden, NSW Dip type: Portable plunge fitted with recirculation pump, 660L capacity Sheep type: Small frame, mixed sex merino sheep, naturally louse infected.

Mean liveweight, 23Kg (range 19-28Kg) Group allocation: Three groups of 5 sheep were dipped in pesticide at two, four and six weeks off-shears. Similar control group sheep were dipped in clean water Pesticide Topclip Blue Shield (Novartis Animal Health, Australasia Pty Ltd). Diazinon 200g/L EC.

Dose regime Two weeks off-shears group Initial charge of dip; 30.7mg/L Replenishment charge; 221 mg/L Four weeks off-shears group Initial chargeof dip; 22.6mg/L Replenishment charge; 163mg/ Six weeks off-shears group Initial charge of dip; 13.2mg/L Replenishment charge; 95mg/L Lice counting TLC Research, according to National Registration Authority recommended protocol (20 x 100mm partings, each side of the sheep).

18 RESULTS Results of the investigation are illustrated in Table 8. 5 Table 8: Individual lice counts in sheep dipped 2, 4 and 6 weeks after shearing Treatment Group mean. lice counts - weeks after treatment tand Weeks, [Diazin.................

oft g/L) 4 6 % 12 shears 2 0 17.8 5.2 1.2 1.4 2.4 6.2 (11.84) (4.66) (0.84) (20.7) (3.78) (11.65) 2 150 17.4 0.0 0.4 0.4 0.2 1.0 (11.01) (0.0) (0.89) (0.55) (0.45) (0.71) 4 0 27.4 9.2 1.2 1.4 2.4 8.6 (10.01) (2.95) (1.30) (1.67) (1.34) (5.77) 17.2 0.0 0.0 0.0 0.0 0.0 (5.68) (0.0) (0.0) (0.0) (0.0) (0.0) 6 0 41.2 13.6 3.2 4.4 10.6 43.8 (20.77) (8.79) (4.09) (5.68) (10.43) (81.64) 6 150 28.4 0.0 0.0 0.0 0.0 (11.78) (0.0) (0.0) (0.0) (0.0) CONCLUSION

Results indicate that the (small) short-wool sheep (Category A, Table 3) were not effectively treated at 15Orng/head diazinon.

Example 3: Treatment of sheep lice with diazinon at approximately 25Orng/head, in four field trials.

METHODS 19 Researcher: N. Sherwood, TLC Research, Camden NSW Dips were operated"by constant replenishment in-afi-cases, using diazinon 500g/L Diprite, Nufarm Ltd). Details of the experimental dips and trial sheep are shown in Tables ga and b. The appropriate charge rates were evaluated by methods outlined in patent application 19946197. The extent of stripping in each dip (SF) and the mean volume of dipwash removed by the sheep was evaluated in an independent preliminary trial.

Tablega: Details of sheep dipped in flel.d trials where sheep were treated with approximately 250m91heaci-diazinon Trial nu,m,ber: ---9. 6142 96143 96147 97103 Location Ta rat d' NiaRgia,,: Marulan, Wootbro k, g 0 . -:. ',.: 1 -.... NSW NSW,: - - NSW.'. NSW - Sheep description Merino Merino Merino Merino

Bodyweight 37 42 42 40 (mean, Kg) Category c c D c (Table3)

Age 2 mixed mixed (ewes and wethers lambs) Condition score 2 2.4 2.7 3.3 Woof fibre 19 approx. 19 20 18 diameter (g) Weeks off 3 3 - 5 3 shears Wool length 20 13 10 15.4 (mm) Number of 2522 3384 2299 909 sheep dipped Table Elb: Details of the dips and operational parameters in the above field trials and parameters of the dipping

Trial number 96142 -- - ' ' - 96143 - ---- 96147 97103 Location Taralga, Niangla, Marulan, Woolbrook, NSW NSW NSW NSW Dip type Shower, Shower, Plunge Shower, Sunbeam Sunbeam -Commercial Sunbeam SSD60 SSD60 Portable Anti-strip SG30 Sump volume 2500 1165 3000 400 (L) Dip operation Sump charge 8.1 9.2 13.9 12.5 rate (mg/L) Replenishment 73.7 62.5 55.6 59.6 rate (mg/L) Shower dips were replenished such that the operating volume of the sump was restored on completion of draining of a batch.

Pump output set to deliver 25-35L in five evenly spaced test buckets during a two minute test run. During operation, shower dips were operated through overhead sprays for three minutes, bottom sprays for one minute and finally for another two minutes through the overhead sprays.

Sheep (25) were nominated as 'tracer' sheep in each trial. Lice numbers on these sheep were assessed and they were individually ear-tagged prior to dipping. Lice counts were conducted according to methods recommended by the National Registration Authority (NRA), specifically being numbers observed in 40 x 10Omm partings on either side of the sheep. Trials were discontinued and arrangements 21 were made for re-treating the entire flock of sheep if (when) lice were evident in either the tracer or other sheep in the flock.

RESULTS Lice counts of tracer sheep before and after dipping are shown in Table 10.

Table 10: Lice counts in tracer sheep before and after dipping Trial Site Mean lice count pre-dipping (at weeks after treatment) Taralga 59.5 1.8(13) Niangla _. 53.8 0(8) +(12) Marulan 30.6 0.04(8) Woolbrook 12.6 0.36(5) This trial was discontinued due to lice being found by the owner on four trial sheep CONCLUSION

These trials demonstrated that a doses of diazinon outside the target range were not sufficient to remove lice from larger (average-sized) merino sheep.

The following example illustrates the results of three subsequent field trials in which the dose rate for dipping according to the invention was raised to the target dose range illustrated in Table 4.

Example 4 Seven field trials in which sheep were treated for lice infestation using diazinon at an intended dose regimen, applying 4500mg/head for average size sheep.

Methods Dips were operated by constant replenishment in all cases, using Diprite formulation (diazinon 5OOg/L EW, Nufarm Ltd). Details of the experimental dips and trial sheep are shown in Tables 11 a and b. The appropriate charge rates were derived using the example product label illustrated in Table 6. These instructions are derived using methods outlined in this application and patent application 19946/97.

22 Table 11 a: Details of sheep dipped In field trials where sheep were treated according to Tables 3 and 6

Tdai':number NI Y R ND004 97152 H .....................

Location Crookwell, Bathu NW.:Walcha, Nth Bogan Gate rst, NSW NSWI SW 66t Central NSW Central West f r NSW 1 Sheep description Merino Merino Merino Merino Meri Merino Merino n o wethers ewes and wethers Bodyweight (mean, 37 50 40 21-32 Kg 15-20 155-65 30-40 Kg) Age mixed mixed, adult mixed, mixed wearier mixed mixed adult Condition score 1.2 2.5-3.0 2.5 2.0-2.5 2.0-2.5 4 2 Woof fibre diameter 20 22 20 16-18 18-21 23 21 (p) Weeks off shears 5 3 6 1.5 0 A5-6 A5-6 Wool length (rnm) 20 15 23 A8-1 0 A5-1 0 20 15-20 Category (Table 3) D D D A A E Number of sheep 1437 603 2500 1402 1306 690 902 dipped 1 1 23 Table 11 b Details of the dips and operational parameters In the above field trials and parameters of the dipping

Trial number 97144 97149 97/N10 98/N10)/HRND903: VHRND004 97152 Location ath N nicha,,,,Nth,,.Bogan urst err' 4 C SW britral. NSW' CW M-;".... Gate v NSW:: NSW - 1 0,..

Dip type Plunge, Shower, Plunge, Portable Portable Portable Shower Concrete Sunbeam Concrete plunge plunge piunge (Sunbeam) In-ground SW60 In-ground Category D D D A A E' D (Table 3)

Sump Volume 6120 800 9000 4000L 3600L 3700 678 Sump cha e rate 22.5 22.5 22.5 108mg/L 1108mg11--- 40rng/L 22.5mg11-- rg (mg/L) diazinon diazinon Replenishment 140 140 140 325mg11--- 325mig/L 120mg11--- 140rng/L rate (mg/L) diazinon diazinon j The shower dip was replenished such that the operating volume of the sump was restored On pompletion of draining of a 1 batch. Pump output, set to deliver 25-35L in five evenly spaced test buckets during a two: minute test run. During 1 operation, shower dips were one minute and finally for another two minutes through the overhead operated through overhead sprays for three minutes, bottom sprays for sprays.

24 Sheep (25) were nominated as 'tracer' sheep in each trial. Lice numbers on these sheep were assessed- and. they were individually ear-tagged prior to dipping. Lice counts were conducted according to methods recommended by the National Registration Authority (NRA), specifically being numbers observed in 40 x 100mm partings on either side of the sheep. Trials were discontinued and arrangements were made for re-treating the entire flock of sheep if (when) lice were evident in either the tracer or other sheep in the flock.

RESULTS Lice counts of tracer sheep before and after dipping according to Tables 3 and 6 are shown in Table 12 Table 12: Lice counts in tracer sheep before and after dipping il Site Mean t:

coun Tna pre-dipping (atf-pon-ths aftertreatment) Crookwell 16.6 0.0(1.5) 0.0(3) 0.0(6) Bathurst 140 0.0(1.5) 0.0(3) 0.0(6) Nerrin Nerrin 19.4 NT 0.0(3) 0.0(6) Minninera 26.2 0.0(2) 0.0(5) 0.0(9.5) Barraba, 45.8 0.0(2) 0.0(6) Walcha 124.8 (pre- 0.0(2) 0.0(6) shearing) Bogan Gate 5.0 0.0(2) 0.0(3.5) 0.0(6) CONCLUSION

These trials demonstrated that a dose rate of approximately 500mg/head diazinon within the target range was sufficient to remove sheep lice infestation from medium20 sized merino sheep The following example is included to demonstrate how the VR categories outlined in Table 2 may be derived by determination of drainage profiles following dipping Example 5 Typical profile for dipwash drainage from a sheep following saturation in a plunge dip.

METHODS Trial Location: TLC Research Facility, Camden NSW.

Dip type: Portable, Galvanised steel Construction 660L capacity ' Drainage area Tilted tow"afd collection vesse. 1, - Dipped- sheep we - re confined on a weighing platform Number sheep dipped: 6 Sheep type: Merino, mean liveweight, 45Kg (range 43.5-47.4Kg), 4 weeks off-shears (Category C, Table 3) Wool type 18-20g fibre diameter, approx. 13.3mm length Pesticide formulation: Diprite 500g/L Diazinon EW, Nufarm Ltd.

Dip operation: Each sheep was plunge dipped for about 20 seconds. On exit from the dip, sheep were weighed and the volume of dipwash drainage recorded, at 20 second intervals.

RESULTS The drainage profile of dipwash removal from the experimental plunge dipping process, measured by both the change in sheep weight and by the volumetric collection of dipwash, is illustrated in Table 13.

The apparent time delay between mean weight change of the sheep and the volume (mass) of dipwash collected in this table was attributable to the time taken for the dipwash to run across the floor of the collection pen and be collected in the measuring cylinder.

26 Table 13 Drainage of dipwasty -following dipping of six adult merino sheep, four weeks off-shears. - Time after dipping (minutes) Mean liveProportion of Volumetric weight of original five- proportion of the sheep weight (%) dipwash collected (Kg) (%) -1 44-.9:-, 1---- - 0 507: -loo 123.4 1 47.7 51.7 2 47.7 51.4 52.0 3 46.8 67.2 59.1 4 47.2 59.2 66.3 46.5 72.4 66.7 6 47.1 62.1 70.5 7 46.3 74.6 71.3 8 47.4 56.0 75.8 9 NR 76.0 NR 86.1 11 NR 86.1 12 NR 96.3 13 NR 96.3 14 46.9 64.6 100.0 Measured as percentage of mean total dipwash collected over the 14 minute sampling period. Values shown are group means.

NR Not recorded Clearly both methods of evaluating the drainage profile of dipped sheep demonstrate that about half the increase in weight (or volume of dipwash) drains from the sheep surface within minutes of the sheep emerging from the dip. The remainder of the volume of dipwash removed is slow to drain, with about 21---remaining on completion 27 of the 14 minutes draining period. By this time the rate of liquid run- off from the sheep surface was very slow and it appeared likely that much of the retained liquid would be lost from the surface by evaporation.

In the above trial, the dipped sheep would have been defined as being at the high end of category C. Field experimentation has indicated that such sheep are likely to remove about 3.1Uhead from the dip. The level of removal was slightly higher in this trial (at about 3.5Uhead) presumably due to lower drainage losses than would be expected in the field. Drainage loss was.relatively slow seen after the first few minutes draining. Typical draining intervals used under field conditions (5-10 minutes) are therefore likely to have only a minor influence on the estimations Of VIR used for dose allocations.

It will be appreciated that various alterations, modifications and/or additions may be 15 introduced into the constructions and arrangements of parts previously described without departing from the spidt or ambit of the present invention.

Claims (18)

28 Claims

1. A method of preparing a dip of pesticide dipwash for dipping a herd of animals of the same species so as to reduce the incidence of overdosing and underdosing, the method including:

defining a 'plurality- -6f categories of animals within the herd, the categories each defining a range in the volume of dipwash removed by an animal; assigning animals to the categories based on the anticipated volume of dipwash removed by each animal within the herd; providing dipwash having an initial pesticide concentration for each category for providing is effective pesticidal control in the dip for animals of said category; and providing dipwash having a second pesticide concentration for each category for replenishing dipwash removed from the dip to maintain an effective concentration of pesticide in the dip.

2. A method according to claim 1 wherein at least three categories are defined according to the anticipated volume of dipwash removed by each animal.

29

3. A method of]teparing-A dip-of' pesticide'dipwash for dipping a herd of animals of the same species so as to reduce the incidence of overdosing and underdosing, the method including:

defining a plurality of categories of animals within the herd, each Category defining a range in the produce of bodyweight and time since shearing; providing dipwash having an initial pesticide concentration for each category for providing effective pesticidal control of animals in said category; and providing dipwash having a second pesticide concentration for each category for replenishing dipwash, the second concentration being sufficient to compensate for the effect of stripping of pesticide from the initial concentration during dipping of animals of said category.

4. A method according to claim 3 wherein at least three categories are defined according to the product of body weight and time since shearing for each animal.

5. A method according to claim 3 or claim 4 wherein said categories include: a first group consisting of animals of body-weight of from 15 to 30 kg and time off-shears from 0 to 2 weeks; a second group consisting of each of the sub-groupings of:

(i) body weight 30 to 60 kg and time off-shears from 0 to 2 weeks and (ii) body weight 15 to 30 kg and timef off-shears from 2 to 4 weeks; a third group consisting of each of the sub-groupings of:

(i) body weight 15 to 30 kg and time off-shears from 4 to 6 weeks, (ii) body weight 30 to 45 kg and time off-shears from 2 to 4 weeks and (iii) body weight 60 to 75 kg and time off-shears from 0 to 2 weeks; a fourth group consisting of each of the sub-groupings of:

(i) body weight 30 to 45 kg and time off-shears -;,o from 4 to 6 weeks,and (ii) body weight 45 to 60 kg and time off-shears from 2 to 4 weeks; and a fifth group consisting of each of the sub groupings of:

2 5 (i) body weight 45 to 60 kg and time off-shears 31 from 4 to 6 weeks, (ii) body weight 60 to 75 kg and time off-shears from 2 to 6 weeks.

6. A method according to claim 3 wherein for each category said initialpesticide concentration (C1c)times the stripping factor (SF) divided by the -. second concentration of pesticide (Cc, Olies within the range of from 0.2 to 2.0 and wherein the stripping factor SF is at least two and is defined according to the relationship SF = CIC/CS5 wherein C.. is a steady state concentration provided when the animals of said category are dipped in a dipping liquid of said first concentration contained in the vessel and the level in the vessel is maintained during dipping by replenishment of the liquid removed with a dipping liquid of concentration equal to the first concentration, the concentration of pesticide in the vessel being initially reduced as a result of stripping of the pesticide by said group of animals until said steady state concentration is reached and from which no significant further reduction in concentration occurs.

1 32

7. A method according to claim 1, wherein said second and said first concentration for each category are independently determined and comply with the relationship wherein the first concentration (Clc) times the stripping factor (SF), divided by the second concentration (CCR) lies within the range of from 0.2 to 2.0 and_wherein the stripping factor (SF) is at least two and is determined by a curve fitting procedure comprising:

(i) dipping a number of animals of the category in a dipping liquid of the first concentration (Clc) contained in the vessel and maintaining the level of liquid in the vessel during dipping by replenishing of the liquid removed with a dipping liquid of the first concentration (Cjc); (ii) preparing a graph of concentration of pesticide against number of animals; (iii) generating an array of calculated stripping curves showing the change in concentration of pesticide during dipping for a range of SF values using the formula 33 VC -C V (C,) IC n-1 S 5+VASF wherein V, is the volume of dipping liquid VA 'S the average volume of dip wash removed per animal C, is the concentration after passage of the animal C1c is the first concentration and equals the replenishment concentration in the procedure; and (iv) fitting the graph determined in step (i) with the array of calculated stripping curves to determine the stripping factor corresponding to the closest fitting calculated curve.

8. A method as claimed in any preceding claim, further comprising the step of grouping animals within the herd which fall into the same category.

9. A method according to claim 8 further including separately dipping each category of animals using a dip containing pesticide of the corresponding initial concentration for the category and during the dipping process replenishing dipwash removed by animals with 34 the second pesticide concentration for the category.

10. A method according to any preceding claim characterised in that said dip is a plunge dip containing the initial pesticide concentration.

11. A method according to any preceding claim wherein said dip is a shower dip wherein the dipwash is delivered from a sump containing the initial pesticide concentration.

12. A method according to any one of the previous claims wherein the replenishment composition is contained in a replenishment vessel provided with means for transferring liquid from the replenishment vessel to the dipping vessel in response to a drop in the level of dipping liquid in the dipping vessel.

13. A method according to any one of the previous claims wherein each category the second pesticide concentration is at least twice the initial pesticide concentration.

14. A method according to any one of the previous claims wherein the level of dipping liquid is maintained with no greater than 10% variation from.the,, initial level.

15. A method as claimed in any preceding claim, 5 characterised in that said animals are-sheep.

16. A method according to any one of the previous claims wherein the herd comprises at least 100 sheep.

17. A method according to any one of the previous claims wherein the pesticide is diazinon.

18. A method substantially as hereinbefore described.

is