Background Tail docking is common practice in the sheep industry to prevent soiling of the breech and flystrike. To ensure optimal healing after tail docking and reduce the risk of arthritis, perineal cancers and prolapses, it is recommended to dock tails equivalent to the length of the vulva. However, recent studies have found that some tails are docked too short (24–86 per cent).
Methods To address this issue, this study aimed to identify key drivers behind tail docking length decisions. Two focus groups, phone (n=30) and online surveys (n=21) were conducted in regional Victoria, Australia to examine farmer knowledge of and attitudes towards appropriate lamb tail length and barriers to best practice. The focus group data were analysed qualitatively, and the surveys were analysed qualitatively and quantitatively.
Results In total, 57 per cent of farmers were classed as docking tails short. Short tail docking appeared to be influenced by unawareness of the recommended length and docking at a length that shearers approve of. Other potential factors included lack of knowledge of negative health consequences associated with short tails, importance placed on dag and flystrike prevention, and impracticality of measuring where to dock.
Conclusion Addressing these factors in future education and intervention programmes may improve tail docking practice and sheep welfare.
- theory of planned behaviour
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Docking sheep tails is a routine procedure in some of the highest sheep-producing countries including Australia, primarily for the prevention of flystrike.1–3 Most tail length studies since 1930 recommended docking tails equivalent to the length of the vulva (ETV), which approximately corresponds to leaving three palpable joints of the tail.4 Findings indicated that this length was optimal to prevent flystrike,4 5 improve rate of healing,6 7 maintain rectococcygeal muscle integrity,6 8 and reduce the risk of prolapses,9 10 cancer11 12 and bacterial arthritis.13 Although some studies recommended docking tails longer than the bare area or to leave approximately four joints of the tail,14 15 other studies reported that tails of this length or longer decreased the ease and efficiency of shearing and crutching.16–18 The accumulation of this research ultimately informed the current Australian Animal Welfare Standards and Guidelines for Sheep (2016), which recommend docking tails ETV.19
Despite research and guidelines for docking tails ETV, recent studies in Australia and around the world2 20 have demonstrated that some farmers dock tails shorter than recommended and have identified this as a sheep welfare issue. Several national Australian surveys have identified between 24 per cent and 54 per cent of participants self-reported docking tails shorter than recommended.21–24 A more recent Australian survey found Victoria had the highest proportion of farmers who self-reported docking tails short (54 per cent).24 Furthermore, 44 per cent of surveyed Australian Merino producers self-reported to dock tails short.23 Primary tail length data collected at a South Australian abattoir indicated 23 per cent of lambs had short tails.13 Most recently, an independent assessment of ewes on 32 Victorian farms identified 86 per cent as having short tails.25 This research over the past 15 years demonstrates that a considerable proportion of Australian farmers are docking lambs’ tails shorter than recommended, indicating that farmers’ tail docking behaviour presents an important risk to sheep welfare.
It is a growing and imperative area of research in the field of animal welfare to understand farmer behaviour and the beliefs and attitudinal drivers behind it.26 Common beliefs among those who dock short include that short tails improve the ease and cost efficiency of shearing, reduce dag formation,2 27 improve appearance,28 improve mating and that it is traditional practice.20 Those who dock short have been found to place significantly less importance on the reduction of uterine prolapses,2 whereas those who dock ETV gave perineum protection as a reason behind docking at this length.20 This indicates that where farmers place importance may be a driver behind docking ETV or short.
To investigate why some Australian sheep farmers dock lambs’ tails short, it is crucial to understand their knowledge, beliefs and attitudinal drivers behind tail docking behaviour and choice of tail length. The Theory of Planned Behaviour (TPB) was used to examine this, which states background factors such as demographics, knowledge and experiences form beliefs, which then form related attitudes.29 Attitudes influence an individual’s intentions and behaviours; the three attitudinal factors include behavioural attitudes (importance placed on certain behaviours), subjective norms (the influence of others) and perceived behavioural control (the ease or difficulty of certain behaviours).30–32 The relationship between human attitudes, behaviour and animal welfare has been demonstrated in previous research.33 For example, Munoz et al 34 found sheep farmers with positive attitudes towards good management practices were more likely to perform these behaviours, which was linked to higher sheep welfare. The present project aimed to identify farmers’ key drivers behind lamb tail docking length and barriers to adoption of best practice. By understanding the main drivers that underpin farmers’ tail docking length decisions, it will be possible to develop intervention strategies to promote attitudinal and behavioural change2 33 35 which have been shown to be effective in previous research.36–38 It was hypothesised that farmers with knowledge of the recommended tail length, knowledge of negative consequences associated with short tails, and positive attitudes towards docking tails ETV, would be more likely to dock tails at this length.
Two focus groups and two surveys (phone and online) were used in this study (2018) to investigate background factors, underlying beliefs and attitudes that influence farmers’ tail docking length.
Purposive sampling was used to invite Victorian commercial sheep farmers to participate in the focus groups, with the assistance of two industry network coordinators known to the Animal Welfare Science Centre. Two focus groups were organised in different Victorian sheep-producing regions to account for differences such as flock sizes and environmental factors. Participants were encouraged to discuss their opinions and experiences in an informal manner, in private function rooms, and each discussion ran for approximately 60 minutes. Each group was facilitated by one research team member, a male psychologist (GJC) with over 30 years of qualitative research experience and a female veterinarian and PhD student (CM). Written consent was obtained at the beginning of each session. The facilitators prompted the topics of discussion and followed the same semistructured agenda. The discussions were recorded, and notes were taken by the lead author (MEW).
The focus group agenda was developed based on TPB to address key beliefs and attitudes of tail docking practice and lamb tail length. The overarching themes of discussion were ‘current practice’; ‘behavioural attitudes’, involving questions around the importance of various aspects of tail docking practice; ‘subjective norms’, regarding the influence of others’ opinions, including the length at which to dock a tail; and ‘perceived behavioural control’, pertaining to the perceived difficulties associated with the procedure. Discussions followed participant-led tangents and spontaneous or delayed contributions, and facilitators maintained the direction of the conversation. The researchers were satisfied with the level of data saturation from the two focus groups as both provided similar key behavioural and attitudinal themes.
The surveys were developed using the TPB, with questions stemming from the most relevant and commonly raised topics in the focus groups. Thirty-two commercial sheep farmers in Victoria, Australia were invited, via email or phone, to participate in the phone survey based on their involvement in a previous study.25 All phone survey participants were invited to complete the online survey. These modes maximised the ease of communication and minimised effort required by participants. The phone survey was conducted as semistructured interviews by the student researcher (MEW) to obtain in-depth qualitative data about individuals’ tail docking behaviour and attitudes. Each interview took 20–40 minutes to complete and notes were taken throughout. Verbal consent was obtained at the beginning of each interview. The interview questions addressed current tail docking behaviour and all attitudinal factors (table 1; contact MEW for full copy). The online survey was distributed via the platform Qualtrics and required 10 minutes to complete. The first question required the selection of a photograph that best depicted participants’ tail docking length (figure 1) and was followed by blocks of questions related to TPB (table 2; see online supplementary file). Responses were recorded on a Likert scale (1–5), with a score of 5 indicating the highest importance/difficulty respectively. Trusted advisers were identified based on a scale of how often participants would rely on a list of individuals for advice (from 0 indicating never to 5 indicating always).
The focus group recordings were transcribed verbatim by MEW. The transcriptions and phone survey notes were qualitatively analysed by content in NVivo V.11 (QSR International) using a thematic framework based on the TPB.39 Content was coded by MEW under parent nodes (child node examples in parentheses) related to tail docking practice, including background factors (‘knowledge of recommended length’, ‘experience of negative health consequences’), current practice (‘method’), behavioural attitudes (‘length importance’, ‘importance of procedure’), subjective norms (‘shearers’ and ‘other farmers’) and control (‘difficulty’, ‘who does the procedure’).
The phone survey notes were created as cases in NVivo,39 along with each farmer’s demographic information from previous data.40 Participants were classed into two tail docking length groups, ETV or short, based on farmers’ self-reported tail length, considering all details and descriptions provided and which tail length image was chosen to best represent their sheep in the online survey, if applicable. The phone and online survey data were also analysed quantitatively using the SPSS V.16.0 statistical program. Fisher’s exact tests were utilised to assess associations between tail docking behaviour (tail docking method), knowledge (of recommended tail length and negative health consequences associated with short tails), reasons given behind specified docking length and self-reported tail length. Mann-Whitney U tests were used to examine attitudinal differences between the two groups, using the online survey data. Binary logistic regressions were used to examine which of the independent variables (attitudinal factors) had a statistically significant effect on farmers’ self-reported tail length (0: short tail; 1: ETV); highly correlated online survey questions (r>0.80) for each attitudinal factor were grouped (table 2) and individuals’ average responses were used for this analysis.
The first focus group involved 13 participants from 9 farms (11 men: 3 women) aged between 26 and 70. The second group involved 10 male participants, each from their own farm aged between 26 and 60. In both focus groups, most participants were prime lamb producers; however, there were two Merino wool producers in each group and one Poll Dorset ram breeder in the first group. Only Merino wool producers mulesed their sheep. Flock size ranged from 500 to 2500 in the first group and from 2500 to 8500 in the second group. All participants were part of industry network groups that convened regularly to discuss a broad range of topics and organised industry specialist guest speakers.
Tail docking in general was described to be very important by almost all participants, primarily for the prevention of flystrike. It was also raised by both focus groups that tail docking was not only a procedure carried out for the prevention of flystrike, but also to maximise the ease of shearing. There were comments around castration being the most important procedure at lamb marking, and vaccinations requiring careful administration were prioritised over tail docking. In general, farmers were aware there was a recommended tail length in the Australian Animal Welfare Standards and Guidelines for sheep19; however, not all were certain of what the recommended length was. In most cases tail length was determined visually without measurement, based on experience and ‘having your eye in’. Most participants acknowledged the link between short tails and vulva cancer. Some participants were aware of research linking short tails to prolapses and/or arthritis, although most were sceptical of these links. Breed standards and ease of shearing were listed as potential factors influencing one’s choice of tail length. Farmers agreed ‘it’s easier to crutch’ sheep with short tails, with some reporting shearer complaints that tails ETV were more difficult to shear. Some participants commented that the use of rings was associated with short tail docking. Specific quotes from the focus groups are reported with survey results in relevant sections.
Thirty of the 32 farmers contacted participated in the phone survey. Two were not contactable. There were equal proportions of meat (40 per cent, n=12) and meat-wool (40 per cent, n=12) enterprises, and six farmers ran wool enterprises (20 per cent). The number of ewes per farm, based on previous data,25 ranged from 431 to 9400, with an average of 2847 ewes. Participants ranged from 28 to 88 years of age with an average age of 54. Majority were men; there were four women. Most were university-educated (53 per cent, n=16), with equal numbers completing secondary education (23 per cent, n=7) or technical college (23 per cent, n=7). The average amount of work experience was 32 years and 83 per cent were part of industry network groups. Of the 30 phone survey participants, 21 completed the online survey.
Majority of farmers were classed as docking tails short (57 per cent, n=17), based on the phone and online survey data. While a large proportion of farmers self-reported they left enough tail to cover the vulva in ewes or left three joints of the tail (67 per cent, n=20), there were multiple ways farmers described their tail docking lengths. Farmers who gave contradictory length descriptions (40 per cent, n=12), such as stating that two inches or two joints were ETV, were classed in the short tail docking group along with those who openly docked short (17 per cent, n=5). Participants most commonly reported more than one person would be involved in docking tails at lamb marking (n=12), some reported that just one person was responsible for tail docking (themselves or a helper) (n=10), and eight employed contractors.
Tail docking method
Tail docking method was not found to be related to tail length group (Fisher’s exact test). The most common tail docking method used by participants was the gas knife, followed by rubber rings. Some used both methods, each for different breeds, and one participant surgically docked tails with mulesing shears (figure 2). Those who mulesed (n=11) more commonly used the gas knife to dock tails (82 per cent, n=9).
Knowledge of recommended tail length
Based on their comments, farmers were classified into two groups, aware or not aware of the recommended length. Half the participants were grouped as being not aware of the recommended length due to being uncertain of, misquoting or not remembering the recommended length, or if they had never read the Welfare Standards and Guidelines. Farmers who were not aware of the recommended length were four times more likely to be classed as docking tails short than those who stated their tail lengths were the same as recommended (Fisher’s exact test, P<0.05) (table 3).
The most common reasons given by the group docking ETV were health preservation, such as preventing cancer, prolapses and arthritis, and adherence to the industry-recommended length or as stated in the Welfare Standards and Guidelines. In contrast, most participants in the short tail group gave ease of shearing, dag reduction and flystrike prevention (labelled as ‘shearers/dags/flies’ in figure 3) as reasons behind their tail docking length. Adherence to the industry-recommended length was not commonly mentioned by the short tail group, and although infrequent, rump appearance and tradition were factors only mentioned by participants in the short tail group (figure 3). A degree of length variation was accepted by 47 per cent (n=14) of participants, one being less concerned over wether lambs’ tail length. In general, the practice was ranked at high importance along with vaccination and was given an average score of 4.9 in the online survey (with 5 being of most importance). Lengthening tails was commonly in response to experiences with negative health consequences associated with short tails or just as a trial. No predictive relationships between behavioural attitudes and self-reported tail length were identified from binary logistic regression analyses.
Knowledge of negative consequences associated with short tails
Few farmers were aware of negative health consequences associated with short tails, such as arthritis and vaginal and rectal prolapses (figure 4). However, 47 per cent of all participants commented on the link between shorter tails and vulva cancer. Although no statistically significant association was identified, a higher percentage of participants in the ETV group were aware of the link between short docked tails and arthritis and vaginal and rectal prolapses, than those in the short tail group (figure 4). Regarding reasons given behind their tail docking length, prevention of arthritis and prolapses tended to be raised more frequently by those in the ETV group than those who docked short (P=0.056). Some farmers in the ETV group had experienced negative health consequences in their flock that they associated with short tails (38 per cent, n=5). For example, one farmer shortened the length of their lambs’ tails when they stopped mulesing and recounted a ‘horrendous’ rate of vaginal prolapses as a result. Another experienced a high incidence of rectal prolapses in feedlot lambs with short tails. Both farmers observed reduced incidences after docking ETV; one reported this was on veterinary recommendation. This was supported by focus group participants. One quoted a veterinarian’s advice: ‘if you cut them too short, you’ll end up with prolapses’. Another described their disregard for shearer complaints on account of preventing vaginal prolapses: ‘put up with a bit of whingeing and have a long tail, and you don’t get prolapses’.
Over half the farmers (53 per cent, n=16) commented that shearers preferred short or no tails because it made shearing and crutching easier. Some farmers had previously been (n=2) or were currently (n=1) involved in shearing their own sheep. Participants in the short tail group placed significantly more importance on docking tails at a length that shearers approve of than those in the ETV group (Mann-Whitney U test, P<0.05; table 2). Some farmers (17 per cent, n=5) reported complaints from shearers that their sheep tails, docked ETV or longer, were too long. Five farmers reported shortening their tails in the past, two of whom stated this was due to shearer suggestions or complaints; short tails were suggested to one participant to improve the cleanliness and appearance of their sheep, and complaints drove the other participant to shorten their tails after a year of trialling a longer tail length.
Tail length variation within and between farms was said to be rare. Only 13 per cent (n=4) reported seeing lambs with tails longer than they would prefer, whereas half the participants had seen lambs’ tails docked too short. Participants observed short-tailed sheep at saleyards, shows, when purchasing sheep, and on neighbouring or nearby properties.
Farmers most commonly reported veterinarians and more experienced farmers as their most trusted advisers (online survey average scores 3.6 and 3.4, respectively). They were followed by family members, friends, network groups and stock agents (2.8–2.3). Binary logistic regression analyses identified a predictive relationship between higher subjective norm scores (related to trusted advisers) and docking ETV (P<0.05) (table 2). Shearers were identified as individuals who farmers would rarely or never seek advice from (1.9). One participant expressed they never relied on others for advice.
Perceived behavioural control
Measuring where to dock
When docking tails, placement of the ring or judging where to cut tails was most commonly visually estimated, based on previous experience (90 per cent, n=27). Physical means of measuring were used only at the start of each lamb marking session or season to develop a visual cue for time efficiency and speed; measuring where to dock each lamb’s tail was said to be impractical. Ways of measuring included referring to the caudal folds of the skin and placing the ring, or cutting, relative to them (33 per cent, n=10); directly comparing the tail length in relation to the vulva (20 per cent, n=6); or by palpating for the joint space (13 per cent, n=4).
Difficulty of procedure
The procedure of tail docking was not considered difficult for farmers and was described as ‘basic’, regardless of method. Docking at a length that shearers approved of was significantly more difficult for those in the ETV group (Mann-Whitney U test, P<0.05) (table 2). Docking ETV tended to be positively predicted by perceived behavioural control (P=0.078) (table 2). Providing instruction to others was also described as simple, and checking the length at which the tails were being docked by helpers or employees was common. Some farmers did not check the length at which helpers were docking tails at marking (23 per cent, n=7); they stated this was due to trust in the tail docking operators, who were either a contractor, employee, family member or partner.
Farmers that docked tails short were less aware of the recommended length in the Welfare Standards and Guidelines, and placed significantly higher importance on docking at a length that shearers approved of. Other identified factors that may impact short tail docking included lower awareness of and experiences with negative health consequences linked to short tails, such as arthritis and vaginal and rectal prolapses, and high importance placed on dag and flystrike reduction. The perceived impracticality of measuring where to dock tails may also contribute to short tail docking. These findings supported the hypothesis that knowledge and attitudinal factors would be related to the choice of tail length. Based on these results and the TPB, figure 5 illustrates a proposed model of the influence of background and attitudinal factors that may influence tail docking behaviour. These attitudinal factors could be targeted in an intervention strategy, which have been shown in previous research to result in changed attitudes and behaviour.36–38 For example, the belief that short tails reduce dag formation, based on previous experience, could be addressed in an intervention that counteracted and challenged this preformed belief and related attitudes, with the goal of changing tail docking behaviour to dock at the recommended length.
The finding that 57 per cent of participants docked tails short closely aligned to that of a recent phone survey of Victorian farmers.24 However, there was an inconsistency identified between self-reported tail length data collected in this study and primary tail length data collected by Munoz et al.25 In this study, 43 per cent of participants self-reported to dock tails ETV, yet all participants had a percentage of short-tailed ewes (two to five years old) in the previous study; averages ranged from 41 to 100 per cent. It is possible that these same participants25 may have changed their tail docking practice since the previous study. However, considering the marked difference between primary tail length data and self-reported behaviour, and the presence of contradictory tail length descriptions, this study highlights the potential unreliability of self-reported tail length data, indicating that the scale of short tail docking in Australia may be larger than what has been captured by previous studies relying only on self-reported data.21–24
There was a significant association between short tail docking and being unaware of the recommended length. This supports findings by Kerslake et al,2 who also identified that farmers who did not follow processor, market or welfare guidelines were more likely to dock tails short. Despite some farmers’ awareness that there should be enough tail remaining to cover the vulva, this was not always reflected in their tail length descriptions nor in previous primary tail length data.25 There were multiple ways farmers described their tail docking length, some of which were contradictory, such as reporting that two tail joints were enough to cover the vulva. It is possible that there are misinterpretations of the recommended length among farmers, where some farmers may consider tails that extend below the upper commissure to be ‘covering the vulva’, rather than correctly extending to or past the lower commissure. This highlights the role of knowledge in compliance with tail length recommendations. The TPB suggests knowledge has a key role in the formation of an individual’s beliefs, attitudes and intention to perform behaviours,30 so education around docking at the appropriate length is imperative.
Although most farmers in this study were members of industry network groups which are support and information systems that may influence individuals’ opinions and decisions,41 there is still a clear gap in knowledge regarding the recommended tail length. There was a predictive relationship identified where farmers who placed higher importance on the advice provided by trusted advisers were more likely to dock tails ETV. Key trusted advisers, reported in the online survey, were vets and other farmers, supporting previous research involving sheep farmers who valued the guidance from these individuals more than research or government institutions.35 42 The reliability of the source impacts how information or advice is received and accepted by farmers; therefore, this finding presents an opportunity for education on the recommended tail length involving identified trusted advisers.
Shearers were not identified as trusted advisers but appeared to directly and indirectly influence short tail docking. Those who docked tails short placed significantly higher importance on docking at a length that shearers approved of, and most farmers agreed shearing and crutching sheep with short or no tails was easier. Similarly, Kerslake et al 2 found that those who docked short placed significantly higher importance on reducing dags and crutching costs. Furthermore, those who docked ETV reported that it was significantly more difficult to dock tails at a length that shearers approved of than those who docked short. This information indicates the influence of shearers is a key factor affecting farmers’ tail docking length decisions, presenting an opportunity for further investigation into the attitudes, knowledge and tail length preferences of shearers and the subjective norms related to farmers’ choice of tail docking length, which could then be targeted in educational programmes.
Overall, there was a lack of knowledge of negative health consequences associated with short tails among both tail length groups, particularly around arthritis and prolapses (vaginal and rectal). Proportionally, fewer farmers who docked short were aware of the links between arthritis, prolapses and short tails. Furthermore, those who docked ETV tended to raise prevention of these specific diseases as reasons behind their tail length more than those who docked short. Similar findings were reported by O’Kane et al 43 around footrot management, where farmers who had knowledge of the importance of regulating lameness in their flock had less lame sheep. The awareness of risk mitigation by docking tails ETV could act as an important driver for farmers to dock at this length. Some participants’ scepticism of the link between arthritis and tail length may indicate a lack of trust in research among producers. In this case, disseminating knowledge only by providing information may not be so effective, particularly from untrusted sources. Considering previous research around the positive influence of knowledge on sheep management,2 43 educational programmes addressing tail docking length should aim to build farmers’ knowledge of the association between the increased risks of aforementioned negative health consequences and docking tails short.
Factors including misconceptions around dag reduction and flystrike prevention, appearance, breed and show standards, and traditions were mentioned to lead to or encourage docking tails short. More participants in the short tail group expressed their beliefs that docking at this length would prevent dag formation and therefore flystrike (figure 3). This belief has been previously reported by farmers in New Zealand2 and is important, considering previous research has found increased risk of flystrike in sheep with short tails.4 5 14 15 Similarly, New Zealand farmers who docked lambs’ tails short were more likely to identify tradition as driving their current choice of tail docking length.2 However, unlike the present study, appearance was mentioned by both tail length groups.2 Short tail docking was said to be common among ram breeders and show communities, to improve rump appearance. Similar results have been documented by Goodwin et al,28 who reported that producers who participate in sheep shows in the USA dock tails short in an attempt to create the illusion of a full, square rump. To enable an investigation of any relationship between enterprise type and tail length, there would need to be a replication of this study including samples from various enterprises such as feedlots, ram breeders and show participants. Furthermore, in promoting best tail docking practice, the misconception that shorter tails prevent dag formation and flystrike must be addressed.
The impracticality of measuring where to dock tails and the lower priority of tail docking in comparison with other lamb marking procedures were raised. These may result in less attention given to tail docking and perhaps less importance placed around tail length. The effects of practicality and priority may impact the length at which lambs’ tails are being docked and must be taken into consideration in the development of any practice change programmes.35
This sample is representative of the wider sheep producer population in terms of enterprise and farmer sex ratio.24 44 45 However, the main limitation in this study is the voluntary participation, which may have led to a biased sample of more proactive farmers with an interest in research. Furthermore, most participants were members of industry network groups that met regularly, indicating they may have had more exposure to current research than the average producer. The wider producer population is likely to have less knowledge of the negative health consequences associated with short tails demonstrated by research. It is therefore expected that the actual percentage of Victorian farmers docking tails short is higher than this sample indicates.
In support of the hypothesis, knowledge and attitudinal factors were related to self-reported tail docking length. A lack of awareness of the recommended tail length and the influence of shearers were found to be important factors among farmers docking tails short. Other factors that may contribute to short tail docking were: the lack of knowledge of associations between docking tails short and arthritis and prolapses; importance placed on dag and flystrike reduction; and the perceived impracticality of measuring tails. These factors must be considered and targeted in intervention strategy development to effect practice change, to improve sheep welfare.
The authors would like to thank the staff and students at the Animal Welfare Science Centre for their support and guidance. They acknowledge the industry network coordinators who assisted the organisation of the focus groups. Most importantly, they thank all the sheep farmers for their participation and for sharing their time and experiences.
Contributors MEW, CM, RD, LH and GJC designed the study. MEW, CM and GJC were involved in focus group data collection. MEW conducted the phone and online surveys. MEW, CM and GJC analysed the data. MEW wrote the paper. CM, RD and GJC contributed with feedback and edits to the paper.
Funding This research was funded by the Faculty of Veterinary and Agricultural Sciences, The University of Melbourne. The lead author was a grateful recipient of the John and Jenny Barnett Memorial Prize.
Competing interests None declared.
Ethics approval This project was approved by The University of Melbourne Human Ethics Committee (ID: 1851246.1).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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