Date published: July 2013 ISBN: Meat & Livestock Australia Limited Locked Bag 991 NORTH SYDNEY NSW 2059

Transcription

1 finalreport Project code: Prepared by: B.PDS.1004 Dr Ian Carmichael South Australian Research and Development Institute Ms Kate Joseph/Dr Leo Cummins South West Prime Lamb Group Inc. Date published: July 2013 ISBN: PUBLISHED BY Meat & Livestock Australia Limited Locked Bag 991 NORTH SYDNEY NSW 2059 Targeted drenching of adult ewes Published by Meat & Livestock Australia acknowledges the matching funds provided by the Australian Government to support the research and development detailed in this publication. This publication is published by Meat & Livestock Australia Limited ABN (MLA). Care is taken to ensure the accuracy of the information contained in this publication. However MLA cannot accept responsibility for the accuracy or completeness of the information or opinions contained in the publication. You should make your own enquiries before making decisions concerning your interests. Reproduction in whole or in part of this publication is prohibited without prior written consent of MLA.

2 Abstract A worm drenching decision program (targeted drenching - TD) designed to reduce drenching levels in adult ewe flocks at strategic intervals, without incurring significant production loss was applied on 7 properties in South west Victoria. Expected benefits include significant delays in development of drench resistance and savings in drench costs. TD uses the average flock worm egg count (WEC) to calculate a proportion of the flock to be drenched to reduce WEC below a critical level compatible with acceptable worm control, rather than to zero. The number to be drenched is calculated after provision for drenching all scouring or obviously thin ewes. Ewes to be drenched are then allocated from the lowest body condition score upwards. Average drench reductions of 58% and 48% were achieved in and respectively without identified production penalties. Summer drenching was reduced by 63% and 49% respectively. The second summer drench averaged across both seasons was reduced by 66%. Producers either had or rapidly developed the skills required to implement TD on their properties. Page 2 of 29

3 Executive Summary Internal parasite control remains a major problem for lamb producers in South-west Victoria and elsewhere in southern Australia. For many years recommended best practice has stressed the importance of drenching the entire flock at strategic times of the year (especially in summer) to underpin an integrated worm control program that includes grazing rotation, preparation of low worm risk paddocks and improved nutrition. This established practice has contributed to escalating drench resistance, necessitating the development of a strategy which reduces drenching and therefore selection pressure for resistance, but continues to provide adequate control of worms. However, the concept of leaving a proportion of the flock un-drenched on some or all of the occasions when it is yarded for drenching is difficult for producers and some veterinary consultants to accept. A program of reduced drenching (targeted drenching [TD]) developed under the Sheep CRC and applied in controlled studies over 2-4 years on Struan Research Centre SA and two commercial farms convincingly demonstrated that drenching of mature ewe flocks could be significantly reduced with minimal risk provided monitoring of worm egg count (WEC) was consistent and reduced drenching levels conservative. In line with current practice TD relies on the average flock WEC to influence a decision whether or not to drench at strategic times. However, TD differs in that it targets only some of the flock to reduce flock WEC below a defined critical level, rather than to zero. The South West Prime Lamb Group Incorporated (SWPLG), a group of approximately 40 lamb producers in the Portland/Hamilton region of Western Victoria, developed B.PDS.1004 to refine the practical application of TD in the hands of producers, identify pitfalls and determine whether it was likely to be acceptable as a significant change to current management practice. TD was implemented on 7 farms at Bulart, Branxholme (2), Heywood, Tyrendarra, Bessiebelle and Cashmore, Victoria over 2 seasons from to Flock size was adult ewes, accompanied for varying periods with their lambs. General flock management for each property was not amended. Producers followed their own established drenching program. Drench reduction levels were not prescribed; the objective being to retain acceptable worm control on the property, concurrent with flexibly reduced drenching. WEC was measured at strategic times of the year, usually shortly before when whole flock drenching would normally have been considered. With variations between enterprises the general timing of these intervals were (a) 1st summer drench (November to January); (b) 2nd summer drench (February to March; (c) Pre-lambing (May to August) and (d) Lamb marking (September to November). Monitoring also included, where possible, ewe body condition and dag scores. At the interval appropriate for each enterprise a decision whether to drench all, a portion, or none of the flock was made, based on WEC, the objective being to reduce WEC below a critical predetermined threshold value when necessary. Critical seasonal WEC values were initially based on those tested earlier in CRC studies, but the process was simplified as the project proceeded. Estimation of the numbers targeted for drenching excluded scouring ewes and those in obvious poor condition, which were all drenched. Sheep in condition score 4 or greater were not drenched. Ewes to be drenched were allocated from the lowest body condition score (CS) upwards. According to facilities and personal preference each producer identified a workable mechanism for physically identifying targeted ewes according to CS in the race and handling or dividing the flock before and Page 3 of 29

4 during drenching. Repeated drafting was unnecessary. Final numbers of ewes drenched were usually a conservative approximation of the calculated numbers, i.e., where there was potential indecision on whether to drench an individual or not, the first option prevailed. Altogether, over the 2-year period 51 informed decisions were made either to drench some or all of a flock, or not to drench any ewes. On 4 occasions (8%) the entire flock was drenched, with 2 of these decisions based on WEC. On one property 23% of ewes were drenched in spring 2012 based on clinical assessment (scour and dag). On 12 occasions (24%) no ewes were drenched; 2 of these decisions were made on good body condition and availability of good quality feed, the remainder on WEC. In other words, targeted treatment principles, including WEC involved most (90%) decisions on whether to drench and what proportion of the flock to drench. Overall this was highly successful and led to average drench reductions of 58% and 48% in and seasons respectively. First Summer drenching across the 2 summer seasons was reduced by 63% and 49% respectively. The level of second summer drenching averaged across both seasons was reduced by 66%. This reduced drenching input was achieved with producers being aware of a level of risk and of using their judgement to drench greater numbers of animals than suggested from the available WEC when they had reservations about worm transmission potential, condition of animals, feed availability and other factors. Body condition was the factor underpinning selection of ewes for treatment and producers did not find difficulty in rapidly identifying target animals. Over the second year of the project one producer gradually extended TD initially from 2 through to 10 additional flocks on his property, including younger ewes, without measured penalties. Originally, TD was tested using a sliding scale of drenching levels according to WEC at different times of the year. This was confusing when applied as a practical day to day management tool on commercial properties. Defined seasonal objectives were replaced with a single overriding objective to reduce the flock average for all planned drenches to at least below 80 epg, more conservatively to around 60 epg. The drenching percentage is estimated using the laboratory actual WEC, not the adjusted WEC. Summer drenching usually has a maximum flock WEC level imposed to limit seasonal pasture contamination. Pre-lambing and spring values are important because they may have immediate implications for the health of ewes or lambs. The value of epg satisfies both requirements with the following minor exceptions. If the pre-lambing ewe WEC exceeds 250 epg or ewe WEC in spring exceeds 500 epg it is recommended to drench 100% of the flock. TD of mature ewe flocks is not a worm control program in its own right. It is imperative that there is an established worm control program using effective drenches. Flock WEC, on which the estimated drenching percentage is based, should be done as close as possible before the planned drenching date. Shortly after the break large numbers of immature worms may be present and WEC can underestimate the true level of infection, therefore, at least at this time of the year, a WEC days after drenching is advised to confirm that the expected level of control has been achieved. The concept of targeted treatment of a component of the flock is attractive for industry adoption in that it retains a system of monitoring and provides for maintenance of WEC below a critical level, yet does not in all cases demand mass flock treatment. The project has demonstrated that if mean flock WEC is kept below a maximum level, worm control can be maintained with little impediment to production, and drenching, particularly in summer, reduced substantially. It remains to formally quantify losses potentially incurred in a conservative TD program and weigh them against the benefits of savings in drench costs and postponement of drench resistance. This may help to offset some entrenched convictions that TD is unsuitable for south eastern Australia. Page 4 of 29

5 Contents Page 1 Background The south west prime lamb group Inc The concept of targeted drenching Project Objectives Faecal worm egg counts (WEC) Reduction of drenching levels Methodology Initial meeting and establishment of B.PDS Composition and management of flocks and the drenching program Sampling, worm egg counts and targeted treatment Worm egg count (WEC) sampling The worm egg count (WEC) report Critical (trigger) worm egg counts Allocation of ewes for drenching Choice of drench Confirmation of satisfactory reduction of the flock average WEC Results and Discussion Introduction November 2010-March April 2011-December Autumn (mid pregnancy) drench Late pregnancy (pre-lambing) drench Post lambing (lamb marking) drench Spring drench First summer drench January 2012-March April 2012-September October 2012-January Page 5 of 29

6 4.7 Summary of targeted drenching outcomes December 2010-January The application of targeted selective drenching principles in SW Victoria Background Targeted treatment program development Targeted treatment principles Targeted treatment practice Communications Success in achieving objectives Impact on the sheep meat industry now and in five years time Conclusions and Recommendations Bibliography Page 6 of 29

7 1 Background 1.1 The south west prime lamb group Inc. The South West Prime Lamb Group Incorporated (SWPLG) is a group of approximately 40 lamb producers in the Portland/Hamilton region of Western Victoria, formed to promote profitable lamb production in the region. A small committee operates to develop 3-5 activities for the group annually. A spin off activity was the formation of a lamb marketing co-operative which ran successfully for 9 years. SWPLG has been operating continuously for almost 20 years. Evening meetings are held with local or guest speakers, on-farm visits to look at new and existing strategies and visits to outside enterprises. Over the years the group has run some large PIRDS and been involved with some detailed on-farm research programs. In the recent past these have included a PIRD on the value of LAMBPLAN in selecting prime lamb sires and involvement in MLA project AHW.045 on the impact of internal parasites in southern Australian prime lamb enterprises. 1.2 The concept of targeted drenching Internal parasite control remains a major problem for prime lamb producers in South Western Victoria and elsewhere in southern Australia (Carmichael, 2009). Many years of research and extension have emphasised the importance of drenching the entire flock at strategic times of the year (especially in summer) to underpin an integrated worm control program including other activities such as grazing rotation, the preparation of low worm risk paddocks and improved nutrition. The widespread and increasing development of resistance to drenches provides a serious threat to this established practice. There is a need to develop a strategy which reduces the amount of drenching to reduce the selection pressure for drench resistance but continues to provide adequate control of worms. However, the concept of leaving a proportion of the flock un-drenched on some or all of the occasions when it is yarded for drenching is recognised as one which most producers and some veterinary consultants will find difficult to accept. Targeted treatment of the blood-sucking worm Haemonchus has been promoted successfully in South Africa for many years There, the FAMACHA system of physical assessment of the level of anaemia is used to identify individuals requiring drenching. Despite significant reductions in drenching levels in sheep in South Africa the concept is too labour intensive and the risk and potential magnitude of losses too high to find practical application under Australian conditions. Hence, for Haemonchus, in Northern NSW and southern Queensland a structured and evidencebased approach, which includes worm egg counting, has been successful in aiding decision making about the need for worm control treatments (Scrivener et al., 2006; Kahn et al., 2006). In South-eastern and South-western Australia the important worm species are the Scourworms (Trichostrongylus and Teladorsagia). Besier et al., (2010) successfully reduced the level of drenching In Western Australian mature ewe flocks without penalty, using threshold WEC as a guide to the proportion of the flock to be drenched and targeting the poorest body condition sheep for treatment. In South-west Victoria and South-east SA Carmichael and Blackburn (unpublished data) have generated similar convincing data using WEC for deciding the proportion to be drenched, plus body condition and scouring to decide which individuals are drenched. Scourworm problems in South-eastern Australia, particularly those involving Black Scourworm (Trichostrongylus vitrinus) are often of rapid onset, with serious impacts on productivity. This mandates that reduced drenching levels are conservative and there is confidence that targeted drenching will continue to support Page 7 of 29

8 robust worm control. A program developed for the high rainfall area including South- west Victoria and South-east SA has been applied over 2-4 years at Struan Research Centre SA and on two commercial farms near Portland (Victoria) and Millicent (South Australia). These controlled studies convincingly demonstrated that drenching levels in mature ewe flocks could be significantly reduced with minimal risk providing that worm egg count monitoring was consistent and reduced drenching levels conservative. In this approach, apart from the computer modelled benefit of significantly delaying drench resistance development (Dobson et al., 2011), it follows logically that there are also substantial savings in drench costs The current project (B.PDS.1004) arose from recognition that the concept needed to be further evaluated on more and varied commercial properties in South-west Victoria to refine its practical application in the hands of producers, identify pitfalls and determine whether it was likely to be acceptable as a significant change to current management practice. It was recognised at the beginning of B.PDS.1004 that entrenched advice stipulated that whole flock treatment was necessary to support adequate worm control. However the rate of escalating drench resistance (shared in different measure by probably all producers in SWPLG) was a serious threat to the industry which could be significantly offset by reduced drenching. The advent of at least one unique new drench (the amino aceto-nitrile derivative Zolvix ) greatly increased the importance of promptly addressing the practicality of the targeted treatment concept. The project was seen to align with the MLA Strategic Plan, Action Plan items; Decrease mortality rates Reduce cost of production Increase skills knowledge and confidence of producers 2 Project Objectives To demonstrate that monitoring of ewe worm egg counts, in conjunction with body condition scores and evidence of scouring can lead to programs of targeted drenching of only a portion of mature ewe flocks and that this will adequately control the effects of parasitism in the flock and reduce pasture contamination with worms to acceptable levels. 2.1 Faecal worm egg counts (WEC) Monitoring of WEC (faecal worm egg counts) at strategic times in mature ewe flocks of at least 6 SWPLG members. Depending on the management system of each specific enterprise these times generally are (a) 1st summer drench (November to January); (b) 2nd summer drench (February to March; (c) Pre-lambing (May to August) and (d) Lamb marking (September to November)). This monitoring would also include, where possible, ewe body condition and dag scores. Page 8 of 29

9 2.2 Reduction of drenching levels Measurement of WEC will provide information used to determine the proportion of the ewe flock which requires drenching. The drenching matrix has been developed by Ian Carmichael and further refined in field studies by SARDI on Struan Research Centre and commercial properties. Not all ewes will need to be drenched each time they are monitored. The actual reduction in drench usage will be closely linked to the flock WEC which, among other factors, is dependent on seasonal and farm conditions and the efficacy of previous drenches used on the property. The reduction in drenching required on each property at each drenching interval will be measured over two years. 3 Methodology 3.1 Initial meeting and establishment of B.PDS.1004 An initial meeting of SARDI staff with 7 SWPLG producers was held at Bulart, Victoria on 2 November The concept of Targeted Selective Treatment or Targeted Drenching (TD) was discussed and relevant work conducted over the past 3 years under the Sheep CRC at Naracoorte and Millicent, SA and Portland, Victoria was presented. It was resolved that work would start on at least 4, but preferably more, properties as soon as possible, once agreement had been confirmed with MLA on funding and milestones. Another consideration was that some late spring drenching had already been done on some properties, and producers needed time to think about the concept, so most would only start in The current ongoing Sheep CRC work on a property at Portland would be rolled over into the new project but with a reduced flock size. The first summer targeted drenching decision was made on the Portland property on 30 November 2010, followed by 2 other properties (Bulart and Branxholme) on 14 December There was significant unseasonal rain over summer and some producers became concerned and drenched their flocks in January. Others had not drenched their mature ewe flocks at all early in summer. To define a baseline for further planning all flocks were sampled on 1-2 February 2011 and the project firmly established on 7 widely-distributed properties in South-western Victoria. Six of these flocks comprised mature ewes of meat sheep breeds, the seventh Merinos. Details of flocks enrolled in the project are summarised in Table 1. Page 9 of 29

10 Table 1 Participant sites and flock details for SWPLG targeted treatment project Location Bulart Branxholme Grassdale Cashmore Tyrendarra Bessiebelle Heywood 115 Composite 100 Merino Flock details 200 Coopworth composite 150 Border Leicester/Merino 150 Border Leicester/Merino 116 Coopworth/Corriedale 150 Romney/BL/Merino composite 3.2 Composition and management of flocks and the drenching program Flock size was to be adult ewes, accompanied for varying periods of the year with their lambs. Flock structure could change from time to time following day to day farm management decisions to cull ewes, split or reduce the flock, or add replacements. General current flock management for each property was not to be amended. Producers were to follow their own routine planned (or unplanned if the need arose) drenching program. The only difference would be that at the determined drenching point a decision whether to drench all, a portion, or none of the flock would be made, based on the average flock worm egg count in samples taken within a week of the proposed drenching time. Samples were to be processed under veterinary supervision at established commercial laboratories at either Hamilton or Wickliffe, Victoria. 3.3 Sampling, worm egg counts and targeted treatment Worm egg count (WEC) sampling Where possible it was recommended to determine the flock average WEC from a minimum of 15 individual counts rather than a single or multiple count average made on a composite sample. The specific purpose of this recommendation was so that producers could observe the huge variation in individual worm egg counts in their flock, including in many cases a large proportion of zero counts which would not benefit from drenching. Samples could be collected either per rectum orfresh from the ground all participants were familiar with the collection of individual samples from the ground, so this was adopted as the preferred method. Page 10 of 29

11 3.3.2 The worm egg count (WEC) report These come in various formats from different laboratories and the following principles were applied to their interpretation for the purposes of TD programs. The only value to be used is the unadjusted Strongyle WEC in the report, not the adjusted (for moisture) value. Ignore the following counts when present Nematodirus ; Chab/Oes (only in some reports) or any other worm types that may be recorded Critical (trigger) worm egg counts The critical worm egg counts which determined the percentage of animals to be drenched were initially based on those tested in CRC studies elsewhere in South-eastern Australia in previous seasons, but were later simplified in the light of data emerging from the project (see Targeted treatment practice, pp ). Early critical egg counts (trigger points) for 4 strategic drenching intervals were ; 1st summer 100 epg, 2nd summer 80 epg, pre-lambing 80 epg and spring 200 epg. Examples of the flock percentage requiring drenching according to this scheme, either pre-lambing or in spring are given below. Table 2. Percentage of animals to be drenched at different WEC s Pre lambing <80 epg Spring <200 epg WEC % drenched WEC % drenched In cases where the egg count is below the trigger point and there are no scouring ewes, no treatment is necessary. The actual number of ewes requiring drenching is calculated after (and not including) provision for drenching any freshly scouring or obviously thin ewes, the latter two determinations being those of the producer Allocation of ewes for drenching According to facilities and personal preference each producer would identify a mechanism for physically identifying targeted ewes and handling or dividing the flock before and during drenching. It was expected that confidence in the process would grow rapidly and that producers would develop a system best suited to their individual circumstances. In broad principle the following process could be followed, although there are numerous variations. The overall percentage of ewes that require drenching to reduce the flock WEC below the critical value is calculated from the WEC before the ewes are yarded. Page 11 of 29

12 Scouring ewes, all of which will be drenched, or ewes identified for drenching because of obvious poor condition are not going to be included in the final calculations, so their numbers are either estimated in the yard and they remain with the flock, or they are drafted off for specific attention. After excluding scouring and thin ewes, the required number of non-scouring animals to be drenched is calculated. This process means that in a flock with scouring ewes the final tally of drenched ewes will always be higher than that originally calculated from the flock WEC. For example, consider a flock of 100 ewes of which 20 are scouring. The flock has a WEC of 100 epg which we wish to reduce to 60 epg. If the flock had no scouring ewes we would normally drench 40% of them (40 ewes) to achieve the required reduction in WEC. However, because 20 are scouring we first make provision for 20 ewes to be drenched and then for 40% of the remaining 80 non-scouring ewes, or 32 ewes. The total number drenched therefore in this scenario is 20 plus 32 (52 ewes), which is 12 more than in a non-scouring flock. The race is filled with ewes once or twice and they are condition scored. This is usually sufficient to provide a broad overview of the distribution pattern of condition scores (CS) in the flock. The expected numbers of each CS in the yarded flock as a whole is then known and a guide to the expected numbers in each full race is given by the capacity of the race. In theory this means that some ewes may be handled twice, but in practice, especially with long races, a reliable estimate of the numbers in each CS category can be made with minimal or no re-handling. Moderate competence in condition scoring is an essential skill but it is unnecessary to be more precise than 0.5 CS units. Ewes to be drenched are allocated from the lowest CS upwards. For example, should it be determined that a total of 120 ewes require drenching and it is estimated from the preliminary scoring procedure above that the approximate CS estimates in the flock are 60 CS2.5, 40 CS3.0 and 80 CS 3.5, then it is necessary to drench all CS2.5 s, all CS3.0 s and 20 CS3.5 s. Because of chance variations in the ratios of CS ewes presented in consecutive races there is a need for flexibility of choice of the higher CS animal for drenching as one proceeds, but this is not an issue, providing all of the lower CS ewes are not overlooked. The final result is an approximation of the calculated required drenching percentage and should in most cases be conservative, i.e, if there is potential compromise or indecision in the drenching process, adjust in favour of the higher rather than the lower level. It is unnecessary to drench ewes of CS4 and above Choice of drench The producers were to use the drench of their own choice, subject to advice,if they wished, on what was the most appropriate (effective and/or cheapest) anthelmintic at the time and whether there were any specific advantages or disadvantages in its use in terms of addressing drench resistance. The project was not involved in determining drench efficacies on individual properties and assumed that effective products or combinations of products were used Confirmation of satisfactory reduction of the flock average WEC Further faecal samples were to be taken days after drenching to confirm that the drench had reduced average flock WEC to the expected level. An additional flock WEC could be done after 4-6 weeks to confirm that overall flock worm control was not threatened. Page 12 of 29

13 4 Results and Discussion 4.1 Introduction The results are presented in chronological order because the development of issues is more logically viewed from a seasonal perspective. In this approach all key events are identified but, in general, finer details including individual worm egg counts etc remain in the quarterly reports or the extensive raw data, except where their inclusion in the final report clarifies a decision or explains, emphasises or illustrates an important action, understanding or interpretation. A series of Notes has been included for each of the activity periods for the first year of the project. The entries provide examples of the level of communication, records and documentation maintained and of producer decision making and intervention under practical farming conditions. Producer decisions were often independent of the targeted treatment process and based on the practical realities of farm management in inconsistent seasons. The examples illustrate the flexibility of the system should producers feel compelled to treat the entire flock at a particular time because they are unsure of circumstances, foresee imminent problems, or, for whatever reason do not have a WEC available, there is no penalty for doing so and they retain peace of mind. A general summary in which overall drenching results are consolidated is given at the end of this Section (see 4.7, pp ). 4.2 November 2010-March 2011 Drenching decisions based on worm egg counts were made on all 7 properties. On some occasions no drench was given to any animals. On 4 properties (5 flocks) targeted selective drenching applied to the planned first summer drench in 2010 resulted in 0%, 12%, 45%, 73% and 81% of the flock being drenched. Observations on the remaining properties were established in A second summer drench was given on 5 of the 7 properties and no drench on 2 properties. Six of the 7 decisions were based on WEC results, leading to targeted selective drenching of 0%, 0%, 1%, 41%, 54% and 100% of the flock. All ewes in the remaining flock were drenched due to concerns about heavy infections under unseasonal conditions. Producers reported that the targeted ewes were rapidly selected from the lower condition component of the flocks as they passed through the race. Larval cultures were done on all faecal samples where egg counts were sufficiently high. The dominant parasite was Teladorsagia, (Ostertagia) the Brown Stomachworm, with smaller numbers of Trichostrongylus or Black Scourworm. Small numbers of Barbers Pole Worm (Haemonchus contortus) were found on the Cashmore property, but not on any of the other properties throughout the project, so it is assumed that its profile and impact was negligible. Page 13 of 29

14 Notes: Location Cashmore March WEC 52 epg. No flock drench. 2 thin ewes and 2 with dag score 4 drenched 1% Bulart December WEC 45 epg. 15 out of 20 samples zero egg counts. Flock count below the critical level, but a decision made to drench a small number of CS 2 and some CS 3 ewes - 12% Branxholme December WEC 360 epg. 73% drenched. Rapid reinfection due to seasonal conditions. Entire flock drenched again mid-january based on WEC (600 epg) and concern (not confirmed by faecal culture) about Barbers Pole Worm Tyrendarra January Drenched whole of flock because of concerns about worms as a consequence of unseasonal summer rains prior to heading away on overseas travel but WEC taken at same time confirmed this was unnecessary. 4.3 April 2011-December 2011 Targeted drenching decisions were made on all 7 properties at various intervals based on WEC, body condition, scour and dag. The drenching interventions can be described as: mid-pregnancy (autumn) late pregnancy (pre-lambing) post-lambing (lamb marking) spring first summer. Because of differences in management, environment and production enterprise, each participant had different priorities in their worm control program and selected only one or a few of the intervals where they saw drenching to be most effective. In addition, they chose to use a wide variety of drenches and combinations according to their individual preferences. The project therefore, continued the principle of not influencing the day to day management of the production enterprise, and aimed only to define the necessity for drenching to occur and then reduce overall drench use once that decision had been made. Follow-up worm egg counting was then done on some occasions to confirm that the levels of worms in the flock had been sufficiently reduced to provide confidence that there would not be production penalties Autumn (mid pregnancy) drench It was not routine practice to drench ewes on any of the properties at this time, however there was considerable monitoring and decision making on some of them. The most directly relevant activities are listed below. Notes: Location Cashmore Bulart Flock monitored monthly from April-June. Ewes monitored in April and May and CS in May. WEC 0 epg and 60 epg Page 14 of 29

15 Branxholme Bessibelle May WEC 218 epg, but one outlier of 2400 epg. Decision to defer drenching until pre-lambing. May WEC 34 epg Late pregnancy (pre-lambing) drench Drenching decisions for ewes based on worm egg counts, body condition and presence of scouring or dag were made on all 7 properties pre-lambing. On two properties it was decided not to give a pre-lambing drench. On the other 5 properties targeted selective drenching was applied to the planned pre-lambing drench, resulting in 34%, 36%, 43%, 86% and 93% of the flock being drenched. Notes: Location Cashmore Decision to drench approximately 80% of the flock based on June WEC 352 epg. 88% of twinning ewes and 77% single bearing ewes (average CS 3.2) were drenched. All ewes with CS of 3 or lower drenched, and to make up numbers some of CS 3.5 Bulart June WEC 28 epg (13 out of 15 zero). 20 CS values - CS 5 (10); CS 4 (6); CS 3 (4). Lambing starts 20 July. Decision made not to give pre-lambing drench. Branxholme WEC at point of lambing 546 epg. Decision to drench 90% of flock late July. Probably a better outcome for worm control had a drench been given in May. Bessibelle Tyrendarra June light (CS<3) and 25 daggy ewes (total 41) drenched (36%). No WEC value, but low in May. Selection on clinical grounds 25 May 2011 WEC 120 epg. (11 out of 15 ewes zero counts and One outlier [1260 epg]). 5 June 2011 Ewes crutched. Average weight clean 85.8 kg. Average weight daggy 85.6 kg. No difference. 6 June 2011 Decision made to drench 40-50% of the flock. Ewes targeted on the basis of dagginess (all 41 daggy ewes) plus general body condition (lighter ewes) 19 June 2011 Follow up WEC 13 days after drenching WEC 52 epg (11out of 15 zero counts). Satisfactory reduction to below 60 epg immediately pre-lambing Post lambing (lamb marking) drench Targeted selective drenching of ewes was applied on 3 properties at the time of lamb marking, leading to 43%, 50% and 81%,drenching levels. Page 15 of 29

16 Notes: Location Bulart Ewe WEC (20 individual counts) 420 epg (range epg). Just finished lambing. Ewes in reasonable condition with little dag. Condition score average 2.3 (3x1, 16x2, 11x3, 1x4). Pasture short. Targeted drenching on 2 September (81% drenched) 27 September 2011 Check on reduction in WEC following drenching. Mean 101 epg (range epg; 16 out of 30 counts zero). 23 October 2011 Routine WEC check. Bulk count 150 epg. Average CS 2.25 and weight 68kg. Little dag. Lambs satisfactory only, but it is not a good clover year. Pasture short (FOO approximately 1100) Tyrendarra 17 August 2011 Individual WEC - average 248 epg (5 zero: 3 60 epg; epg; epg; epg). Marked lambs 138%. Grassdale Spring drench Drenched 24 August 2011 Ewes with dags and/or CS below 3 were targeted (43%). Both ewes and lambs to be re-sampled late September and for interest compared with a similar (maternal and lamb age, food on offer) flock where there has not been targeted treatment. 18 August Post lambing/lamb marking check up. Bulk WEC 320 epg. Decision to drench 50% of flock (22/8/11) including all scouring and lower CS ewes. To reduce WEC to around 160 epg. Ewes are not routinely drenched in spring, but routine monitoring continued on 3 properties. A decision to delay autumn drenching on one property (Branxholme), until pre-lambing approximately 2 months later was, in retrospect, not the best choice, because persistent drench activity failed, leaving ewes heavily exposed to worms from autumn pasture contamination. Targeted treatment (27%) was applied to the spring treatment that was necessary. Notes: Location Branxholme 11 October Serious shortcoming (at least 5 weeks) in the activity of Cydectin LA injection in relation to its label claims for persistent activity against Teladorsagia. Many ewes with severe dag. 19 October Severe flock scour (Day 84 after treatment with Cydectin LA injection). 32 out of 100 had zero counts. Mean WEC 506 epg. 27% scouring and daggy animals drenched. Page 16 of 29

17 Tyrendarra 4 October Re-sampling of ewes plus lambs and second similar flock plus lambs. 43% ewes of targeted flock and 100% of non-targeted drenched 24/8/ First summer drench Targeted treatment (4yo, rearing 161% lambs): Ewes 120 epg; Lambs 360 epg Comparison flock (3yo, rearing 164% lambs): Ewes 150 epg; Lambs 270 epg. No differences between these groups. Lambs drenched. No ewes drenched. Drenching decisions for a first summer drench for ewes based on worm egg counts, body condition and presence of scouring or dag were made on all 7 properties. On one property no pre-lambing drench was given. On the other 6 properties targeted selective drenching was applied to the planned first summer drench, resulting in 10%, 60%, 80%, 83%, 90% and 90% of the flock being drenched. The principle of targeted selective treatment was extended on one property (Bulart) to two additional mature ewe flocks for the first summer drench. Notes: Locations Bulart 10% of ewes drenched in original flock and targeted drenching of 75% and 80% started in two additional flocks Heywood 2 November Bulk WEC of ewes 150 epg and lambs 90 epg. Ewes in very good condition. Plentiful good quality food. Decision not to drench ewes. Tyrendarra 12 November % drenched based on dag or and/or lighter condition, around CS 3 or lower. Average WEC 218 epg (range epg). 4 December Follow-up on first summer drench. Bulk WEC 0 epg. 4.4 January 2012-March 2012 This period broadly covers decisions relating to the second summer drench (early 2012). Decisions for the second summer drench based on worm egg counts, body condition and presence of scouring or dag were made on 6 of the 7 properties in the first quarter of On these 6 properties the percentages of ewes drenched using targeted treatment principles were 0%, 60%, 60%, 53%, 70% and 0%. The seventh property (Cashmore) routinely does not give a second summer drench until March. In 2012 it was delayed until the first week of April, when the producer decided on the basis of feed availability, robustness of the ewes and absence of scouring not to drench. This is in line with some previous decisions on this property where on occasions only 1-2% of ewes have been drenched. Therefore, on 2 properties no second summer drench was given. Page 17 of 29

18 Producers on 2 properties extended the concept to additional flocks with targeted drenching percentages for the second summer drench in adult ewe flocks of 0%, 0%, 0%, 66% and 70% (Bulart) and 85% (Grassdale). 4.5 April 2012-September 2012 This period broadly covers decisions relating to the 2012 pre-lambing and lamb marking drenches Summer was much drier than that of 2010/2011 and autumn remained dry throughout. Available feed was less than the previous season. Most ewe flocks continued to receive grain supplements through to winter. Decisions for the pre-lambing drench based on worm egg counts, body condition and presence of scouring or dag were made on 6 of the 7 properties from May-July The percentages of ewes drenched on the 6 properties based on worm egg counts and using targeted treatment principles were 0%, 0%, 30%, 38%, 77% and 100%. This compares with 0%, 0%, 34%, 36%, 43%, 70% and 90% drenching of pre-lambing flocks in Worm egg count was not always the overriding factor in determining the need to drench or the percentage drenched. For example, Bessiebelle drenched 77% of the pre;lambing flock with a WEC of only 30 epg based on dagginess and light body condition and Tyrendarra drenched 43% of a flock with a mean WEC of 58 epg (12 zero counts out of 15), targeting all thin and scouring ewes. A follow-up WEC at Tyrendarra approximately 2 weeks after the above pre-lambing drenching (43% of the flock) indicated that the average worm egg count had not been satisfactorily reduced (original mean WEC of 15 individuals 60 epg vs bulk 120 epg post drenching). The most plausible (unverifiable) explanation for this at the time was thought to be sampling bias, however further sampling in August confirmed that the ewes were carrying substantial worm burdens and they were all drenched at lamb marking late in August. A more likely explanation is that there was rapid exposure to infection shortly before the original sampling so that a large proportion of the worm burden at the time of sampling comprised immature (and therefore non egg-producing) worms. Under such circumstances the WEC would provide an underestimate of the potential danger and therefore of the proportion of the flock to be drenched. This highlights the value of a bulk WEC post-drenching, especially at this time of the year, to confirm that worm levels have been reduced as expected. One producer (Bulart), who has extended the targeted treatment concept to additional adult ewe flocks on his property, recorded targeted drenching percentages for the pre-lambing drench of 0%, 0%, 0%, 50% 50% and 66% in these flocks. One producer (Cashmore) again decided that the ewes were in good health and it was unnecessary to do a worm egg count or drench ewes pre-lambing. The ewes were due to lamb in late August and it was agreed that a decision on targeted drenching would be made at lamb marking in September. The late autumn-winter period was reasonably harsh in 2012 and in all areas available feed was less than the previous season. High lambing percentages placed greater strain on ewe flocks. In the southern sites after a slow start the season became wet, and some paddocks waterlogged, putting further pressure on the availability of good pasture. It was thought that Page 18 of 29

19 this seasonal difference may lead to greater drenching of ewes at lamb marking and this was confirmed in practice. Decisions for a lamb marking drench based on targeted treatment principles were made on 4 of the 7 properties from August-September Worm egg counts in ewes on 2 properties (Cashmore and Tyrendarra) were very high at the time of lamb marking. Three producers did not to sample or drench ewes at lamb marking, judging them either to be in good condition or without need for intervention because of successful pre-lambing drenching. The percentages of ewes drenched on the 4 properties were 75%, 85%, 100% and 100%. This compares with 43%, 50% and 81% on 3 properties at the same time in One producer (Grassdale) who did not drench any ewes pre-lambing followed up postlambing and drenched 85% of ewes at lamb marking in July. Observations were discontinued on this property a few weeks after lamb marking when the trial flock was inadvertently mixed with another flock and could not be accurately reassembled. The Bulart property had now had extended the targeted treatment concept to 7 additional adult ewe flocks on his property, recorded targeted drenching percentages at the time of lamb marking in these flocks of 100%, 66%, 66%, 0%, 0%, 0% and 0%. This illustrates very clearly, first that the concept of targeted treatment can work to reduce drench usage significantly, and second, that there is likely to be huge variability between flocks on a single property. Table 3. Examples of satisfactory WEC reduction following drenching of a portion of a flock Location Original WEC Date % Drenched Check Date Final WEC Bulart /8/12 75% 19/9/12 30 Tyrendarra 210 3/10/12 23% 23/10/ Tyrendarra /11/12 88% 4/12/ October 2012-January 2013 This period broadly covers decisions relating to drenches that might have been needed in spring 2012 and the first summer drench. Observations on one property (Grassdale) were discontinued shortly after lamb marking. Decisions for the first summer drench based on targeted treatment principles were made on 5 of the remaining 6 properties. The percentages of ewes drenched using targeted treatment principles were 0%, 58%, 88%, 90%, and 100%. For 10 additional flocks Bulart recorded first summer drench percentages of, 0%, 0%, 0%, 30%, 50%, 66%, 73%, 80%, 85% and 87%. He reported that his flocks were all in good condition, including weights in some groups to support this. Page 19 of 29

20 On one property (Tyrendarra) a discretionary (no WEC value) spring drench was given at the time that lambs were drenched (4/10/12) to 23% of ewes in the flock with moderate to severe scour. Bulart continued with the experimental flock to the second summer drench in March The ewes had a WEC of 120 epg, but were combined with a flock of young ewes (WEC 240 epg) for mating, so 66% of the combined flock were drenched. Five other flocks had drenching levels of 0%, 0%, 0%, 25% and 66%. Page 20 of 29

21 4.7 Summary of targeted drenching outcomes December 2010-January 2013 The period includes activities relating to the first summer drench of through to and including the first summer drench of , plus information for the second summer drench in 2013 for Bulart. Information is summarised in Tables 4 & 5 with explanatory footnotes. Table 4 South West Prime Lamb Group: Targeted drenching percentages. First summer drench to spring drench 2011 Location First summer Second summer Autumn 2011 Prelambing Lamb marking Spring 2011 Bulart 12% 0% X 0% 81% X Branxholme 73% 100% 0% 93% X 27% Grassdale - 41% X 0% 50% X Cashmore 45% & 80% 1% X 86% X X Tyrendarra - 100%* X 43% 43% X Bessiebelle 0% 54% X 36% X X Heywood - 0% X 34% X X * Based on concern about potential clinical problems. WEC confirmed drench unnecessary. X Ewes not routinely drenched on property at this interval Page 21 of 29

22 Table 5. South West Prime Lamb Group: Targeted drenching percentages. First summer drench to first summer drench Owner First summer Second summer Autumn 2011 Prelambing Lamb marking Spring 2011 First summer Bulart 20% 0% X 0% 75% X 0% Branxholme 90% 70% X 100% Grassdale 90% 0% X 0% 80% Disc. Disc. Cashmore 83% 0%* X 0%* 100% X 90% Tyrendarra 60% 60% X 30% 100% 23%* 88% Bessiebelle 80% 53% X 77% X X 100%# Heywood 0% 60% X 38% X X 58% *Based on clinical evaluation alone #Based on clinical evaluation before egg count result received Disc. Program discontinued due to mixing of flocks see text X Ewes not routinely drenched on property at this interval 20% of ewes drenched in original flock and targeted drenching of 75% and 80% started in two additional flocks Altogether, over the 2-year period (excluding 2 cases where the producer had pulled the trigger and opted to drench all of the flock without a WEC value or convincing clinical signs that flock health was threatened) 51 decisions were made either to drench some or all of a flock, or not to drench any ewes. On 4 occasions (8%) the entire flock was drenched, with 2 of these decisions based on WEC. On one property 23% of ewes were drenched in spring 2012 based on clinical assessment (scour and dag). On 12 occasions (24%) no ewes were drenched; 2 of these decisions were made on good body condition and availability of good quality feed, the remainder on WEC. In other words, targeted selective treatment principles, including WEC involved most (90%) decisions on whether to drench and what proportion of the flock to drench. Overall this was highly Page 22 of 29

23 successful and led to average drench reductions of 58% and 48% in and seasons respectively. Summer drenching across the 2 summer seasons was reduced by 63 % and 49% respectively. The level of second summer drenching averaged across both seasons was reduced by 66%. This reduced drenching input was achieved with producers being aware of a level of risk and of using their judgement to drench greater numbers of animals than suggested from the available WEC when they had reservations about worm transmission potential, condition of animals, feed availability and other factors. Body condition was the factor underpinning selection of ewes for treatment and producers did not find difficulty in rapidly identifying target animals. 4.8 The application of targeted selective drenching principles in south-west Victoria Background The principles developed for and tested in the current project derive from experience accrued in veterinary diagnostic and research activities by one of the participants (IC) over more than 20 years in the South Australian environment, especially the cool temperate South-east of SA, which is similar climatically to adjacent South-west Victoria. Over the last 3 decades, although uptake by producers has been somewhat disappointing, it has become recommended practice for informed drenching decisions to be based on the average of a group of individual WEC or a composite (bulk) WEC of each of the flocks on a property. Only those flocks deemed to have counts that might lead to breakdown in overall worm control on the property should be drenched. Based on experience, parasitology laboratories and farm consultants have identified certain trigger WEC values associated with each of the seasonal decisions on whether to drench or not. In South Australia the figures used by the Primary Industries Parasitology Laboratory have been as follows: First summer drench, 100 epg; Second summer drench 80 epg; Pre-lambing drench 80 epg; Spring drenches, 200 epg. At each of these points the whole flock, regardless of its composition, has traditionally been drenched. Targeted treatment also relies on the average of a group of individual WEC or a bulk WEC, but differs substantially from whole-of-flock treatment in that it aims to reduce the flock mean WEC below certain critical levels rather than to zero, by treating only a calculated proportion of the flock. The emphasis is on retaining acceptable worm control on the property concurrent with flexibly reduced drenching, not on imposing mandated maximum percentages of drench reduction which are likely to lead to failure of worm control. The concept is not applicable to and will not work on properties with marginal or poor worm control, which by definition is unsustainable Targeted treatment program development A program aimed at reducing the level of drenching of mature ewe flocks was developed by SARDI Parasitology for the high rainfall area including South- western Victoria and South-east SA and tested under the auspices of the CRC for Sheep Industry Innovation over 2-4 years at Struan Research Centre SA and on two commercial farms near Portland (Victoria) and Millicent (South Australia). These controlled studies convincingly demonstrated that drenching levels in mature ewe flocks could be significantly reduced with minimal risk providing that worm egg count monitoring was consistent and reduced drenching levels conservative. In this approach, apart from the computermodelled benefit of significantly delaying drench resistance development (Dobson et al., 2011) it follows logically that there are also substantial savings in drench costs. Page 23 of 29