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Australian Sheep Parasite Management Survey 2019 - Flystrike Results


by Alison Colvin, May 2020

In early 2019 Australian sheep producers were asked about their sheep parasite control management practices for the year 2018. The survey was conducted by Dr Alison Colvin, Professor Stephen Walkden-Brown and Dr. Ian Reeve from the University of New England and was supported by Australian Wool Innovation Limited and followed previous surveys of the years 2003 and 2011. The results of the survey will ensure that research, advice and information can be tailored to producers at a regional, state or national level, addressing the issues that are currently of greatest importance.

Survey process

A link to the survey was emailed to the Australian Wool Innovation Ltd (AWI) email list and links were available on the AWI website (wool.com) and the ParaBoss suite of websites: paraboss.com.au, wormboss.com.au, flyboss.com.au and liceboss.com.au). Respondents were asked to complete a survey with a maximum of 45 questions which was separated into 5 sections:

1.   Property details
2.   Worms and Liver fluke
3.   Blowfly control (this article)
4.   Lice control 
 

Table 1: Number of respondents to the main survey by Region.
Table 1: Number of respondents to the main survey by Region.

Location and enterprise results

The response rate to the survey was lower than in previous years with a total of 354 usable responses returned with a further 250 responses to the short, 5 question survey used to measure non-response bias. There were 575 responses for the 2011 survey and 1365 responses to the 2003 survey. The reduced response rate may have been due to severe and continuing drought experienced by a large part of the country in 2019, survey fatigue in respondents, length of the questionnaire and presentation of the survey on an online platform. The responses to the short, 5 question survey confirmed that the responses to the main survey were a good representation of Australian sheep producers with very few differences in responses between the two.
Figure 1 shows the distribution of the respondents sorted by postcode into Meat and Livestock Australia (MLA) Reporting Regions (Region). The largest number of respondents came from Central NSW (83), Wimmera Mallee Murray (79) and Northern NSW/Qld (Table 1). 

Figure 1: Location of survey respondents within MLA Reporting Region.
Figure 1: Location of survey respondents within MLA Reporting Region.

The mean age of respondents was 57 years with a range of 27-92 years, this is higher than in 2003 (51 years) and 2011 surveys (56 years). The mean reported rainfall in 2018 (407mm) was significantly lower than the mean average annual rainfall of respondents (557mm).

Flystrike results

Incidence of flystrike

As reported in the corresponding article on worms and liver fluke, 2018 was a drier than average year for large parts of the Australian continent. This seems to have affected the proportion of sheep producers who reported flystrike in their sheep with only 49% reporting any type of flystrike and the proportion reporting breech strike or body strike significantly reduced compared with the 2011 survey (Table 2). The incidence of body and breech strike within respondents’ flocks was also reduced compared with 2011 (Table 2).

Methods for control

Sheep producers employed an integrated approach to the control of flystrike. The most popular methods to assist with flystrike control were timing of crutching (76%), timing of shearing (63%) and preventative chemical treatment (76%). Nationally, 47% of respondents indicated that they mulesed their sheep and 46% used genetic selection for control of blowfly (these figures include both wool and meat sheep enterprises). Merino x Merino producers were more likely to mules (69%) and more likely to use genetic selection (58%) indicating that Merino producers are looking for alternatives to mulesing for maintaining a clean breech area but are still reliant on mulesing whilst they implement their breeding program. Meat x Meat producers were significantly less likely to mules (9%) or use genetic selection for flystrike control (26%) which is consistent with meat sheep breeds having lower risk of strike due to lower breech wrinkle and breech cover. Mulesing results were similar to results from the 2011 survey with 48% of ewe lambs and 46% of wether lambs mulesed in that survey. However, these figures are lower than reported in the 2014 Sheep CRC producer survey (83% merino lambs mulesed) and the 2017 AWI Merino Husbandry Practices Survey (63% mulesed wether lambs, 70% mulesed ewe lambs) which both focused on merino sheep enterprises. The proportion of Merino x Merino enterprises using mulesing in this survey was similar to the 2017 AWI Merino Husbandry Practices Survey. It is also possible that sheep producers are moving away from the surgical procedure or that mulesing may have been delayed due to the very dry year. A significantly higher proportion of sheep producers from Central NSW used genetic selection (62%) compared with the national average (46%), with East Vic producers less likely to use genetic selection (8%).

When asked about the importance of these flystrike control methods, mulesing sheep was considered most important (ranked 2.8/3, where 1 is somewhat important, 2 is important, 3 very important). Preventative chemical treatment (2.6/3), timing of crutching (2.6/3) and genetic selection (2.5/3) were also very important. When asked about the use of these methods in 2018 compared to 5 years earlier 30% of respondents said they used genetic selection more now than 5 years ago (65% no change and 5% less now) and 18% used preventative chemical treatment more now (73% same, 9% less now, Figure 2). There was a slight trend towards reduced use of mulesing with 11% using it less than 5 years ago.

When chemical treatments were given they were given predominantly as a preventative treatment at approximately the same time every year (66%). When this method is used, dicyclanil is the most commonly used chemical (55%) followed by cyromazine (24%). Backliner/spray on was the most popular method of chemical application (66%) followed by hand jetting (16%). Only 5% of respondents reported suspected resistance to a flystrike treatment product.

Use of visual traits and Australian Sheep Breeding Values

Genetic selection has an increasing role to play in breeding for resistance to flystrike with pressure on wool growers to produce wool from un-mulesed sheep. As mentioned above, more sheep producers are indicating that they use genetic selection now than 5 years previously. Producers also identified breeding for genetic resistance as their most important change in flystrike management over the last five years (21%).

Fifty-six percent of respondents indicated that they used visual traits for selection in ewes for sheep that are less susceptible to flystrike and 44% used visual traits for selection in rams. The most commonly used visual trait in ewes was to cull sheep with body strike (29%) followed by cull sheep with fleece rot (28%), breech wrinkle (22%), wool colour (20%) and cull sheep with breech strike (20%).  Dag score (15%), urine stain (12%) and breech cover (12%) were less likely to be used. There were large differences in use of visual traits between Regions with the use of visual traits generally higher in WA, Central NSW, Northern NSW/Qld and SA Peninsula than in East Vic, Tasmania or Wimmera Mallee Murray. There was also a large difference in use of visual traits between chosen enterprises with Merino x Merino enterprises more likely to use all visual traits listed than Meat x Meat.

Australian Sheep Breeding Values (ASBVs) were less utilised than visual traits with only 17.3% using ASBV traits to select for rams, 75% of respondents who answered this question had Merino x Merino enterprises. The use of ASBVs was up slightly from the 5% who used ASBVs in the 2011 survey. The most popular ASBV trait used to select sheep that are less susceptible to flystrike was Breech wrinkle (64%) followed by Worm Egg Count (52%), Souring and dags (36%), Co-efficient of variation of Fibre Diameter (36%) and Breech Cover (36%). There were significant differences between chosen enterprises for Breech wrinkle (BWR) with higher proportions of Merino x Merino and Merino x Other using BWR than the other three enterprises (Table 3).

Mulesing

As mentioned above, 47% of all respondents indicated they used mulesing for flystrike control, with 69% of Merino x Merino, 18% Merino wethers, 13% Merino x Other and 9% of Meat x Meat using the procedure. Of those who mulesed, there was a very high proportion of sheep producers using pain relief with mulesing in ewe lambs (87%) and wether lambs (91%) much higher than the rates of pain relief used in 2011 (59% ewe lambs, 64% wethers). For ewe lambs and wether lambs combined, most used Tri-Solfen® (84%) with few using a combination of Tri-Solfen® and Buccalgesic® (4%) or Buccalgesic® alone (0.5%), 12% used no pain relief. There were no differences in use of pain relief between Chosen enterprises.

For those respondents who used mulesing the average age of lambs mulesed was 2.2 months, there was a large difference between regions with East Vic and Northern NSW/Qld mulesing significantly later (3.1 months and 3.3 months, respectively) than Central NSW (2 months), South Australia (2.1 months), Wimmera Mallee Murray (2.1 months) and Western Australia (1.6 months). The difference in age at mulesing was confined to Region with there being no difference between Chosen enterprises. The mean proportion of lambs mulesed was 92% with a trend for those in Northern NSW/Qld to mules a smaller proportion of replacement sheep (79%). The change in proportion of lambs mulesed in 2018 and proportion of lambs mulesed 5 years ago remained stable in most Regions ranging from -1.3% to 1.2%, except for Northern NSW/Qld which reported a significantly larger change in the proportion of lambs mulesed with a mean reduction of 21% compared with 5 years ago.

Sources of information for Flystrike control

The FlyBoss website was considered ‘somewhat important’ by respondents as a source of information for parasite control (ranked 2.4/4). The use of FlyBoss has increased markedly since 2011 with a total of 59% of respondents visiting the site with 18% using the site to make changes to their flystrike control practices compared with 11.4% visiting in 2011 and only 2% using the site to make changes (Table 4).

The FlyBoss website has a range of tools and information including:

Australian Wool Innovation and the researchers wish to thank the sheep producers who took part in the Benchmarking Australian Sheep Parasite Survey.