Changes in prevalence of, and risk factors for, lameness in random samples of English sheep flocks: 2004–2013

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Highlights

  • First evidence that prevalence of lameness in sheep in England has halved in 10 years.

  • Prevalence of lameness associated with prevalence of footrot and contagious ovine digital dermatitis in flock.

  • First evidence bleeding of feet associated with foot trimming is associated with higher prevalence of lameness.

  • First evidence from a random sample that prompt treatment of first lame sheep in a group associated with low prevalence of lameness.

  • First observational study to highlight lower prevalence of lameness associated with whole flock vaccination and selection of replacements from never-lame ewes.

Abstract

The aims of this study were to update the prevalence of lameness in sheep in England and identify novel risk factors. A total of 1260 sheep farmers responded to a postal survey. The survey captured detailed information on the period prevalence of lameness from May 2012–April 2013 and the prevalence and farmer naming of lesions attributable to interdigital dermatitis (ID), severe footrot (SFR), contagious ovine digital dermatitis (CODD) and shelly hoof (SH), management and treatment of lameness, and farm and flock details.

The global mean period prevalence of lameness fell between 2004 and 2013 from 10.6% to 4.9% and the geometric mean period prevalence of lameness fell from 5.4% (95% CL: 4.7%–6.0%) to 3.5% (95% CI: 3.3%–3.7%). In 2013, more farmers were using vaccination and antibiotic treatment for ID and SFR and fewer farmers were using foot trimming as a routine or therapeutic treatment than in 2004.

Two over-dispersed Poisson regression models were developed with the outcome the period prevalence of lameness, one investigated associations with farmer estimates of prevalence of the four foot lesions and one investigated associations with management practices to control and treat lameness and footrot. A prevalence of ID > 10%, SFR > 2.5% and CODD > 2.5% were associated with a higher prevalence of lameness compared with those lesions being absent, however, the prevalence of SH was not associated with a change in risk of lameness.

A key novel management risk associated with higher prevalence of lameness was the rate of feet bleeding/100 ewes trimmed/year. In addition, vaccination of ewes once per year and selecting breeding replacements from never-lame ewes were associated with a decreased risk of lameness. Other factors associated with a lower risk of lameness for the first time in a random sample of farmers and a full risk model were: recognising lameness in sheep at locomotion score 1 compared with higher scores, treatment of the first lame sheep in a group compared with waiting until >5 were lame, treatment of lame sheep within 3 days, ease of catching lame sheep and quarantine for > 21 days. A previously known factor associated with a lower risk of lameness was footbathing to prevent ID. We conclude that the prevalence of lameness in sheep in England has fallen and that this might be in part because of increased uptake of managements recently reported as beneficial to control lameness. Routine foot trimming should be avoided.

Introduction

Lameness costs the sheep industry in GB £24–£80 million per annum (Nieuwhof and Bishop, 2005, Wassink et al., 2010). Financial losses occur because of reduced rates of lambs born and reared, and slower growth rates of lame lambs (Wassink et al., 2010).

In 2004 a random sample of 3000 English sheep farmers were sent a one year retrospective questionnaire requesting information on types of foot lameness (Kaler and Green, 2008) and management of lameness in their flock (Kaler and Green, 2009). A total of 809 (27%) farmers replied after two reminders. The geometric mean prevalence of lameness was 5.4% (95% CI 4.7%–6.0%) and the global mean prevalence of all lameness was 10.6% with an estimated 6.9%, 3.7%, 2.4%, 1.9%, 0.9% and 0.8% of the sheep lame with at least one of interdigital dermatitis (ID), severe footrot (SFR), contagious ovine digital dermatitis (CODD), shelly hoof (SH), foot abscess and toe granuloma respectively. ID and SFR dominated the within- and between-flock prevalence of lameness with 90% lame sheep having these two lesions and 80% farmers reporting that it was the most common cause of lameness in their flock.

In the same study, factors associated with a higher annual period prevalence of all lameness (Kaler and Green, 2009) were routine foot trimming once or more per year compared with no routine foot trimming, routine footbathing and a stocking density of >8 ewes/ha. Separating lame sheep from sound at pasture was associated with a lower risk of lameness. In other observational studies with non-random samples of farmers, lower farmer reported prevalence of lameness was associated with quarantine of new and returning stock, isolation and treatment of all sheep lame with ID or SFR with parenteral and topical antibacterial treatments (Wassink et al., 2003), footbathing and turning a flock to clean pasture to treat ID (Wassink et al., 2004) and catching the first mildly lame sheep in a group for treatment within 3 days of first becoming lame (Kaler and Green, 2008). Factors associated with a higher prevalence of lameness were routine foot trimming (Grogono-Thomas and Johnston, 1997, Kaler and Green, 2009, Wassink et al., 2003, Wassink et al., 2004, Wassink et al., 2005), footbathing to treat footrot (Wassink et al., 2003, Wassink et al., 2004) and a stocking density >8 ewes/ha (Wassink et al., 2003). Two clinical trials have demonstrated that recovery from footrot is most rapid when sheep are treated with parenteral and topical antibacterials with no paring of the diseased foot (Kaler et al., 2010, Kaler et al., 2012).

In 2011 the Farm Animal Welfare Council proposed that the prevalence of lameness in 2004 of 10% should fall to 5% by 2016 and 2% by 2021 (FAWC, 2011) with farmer uptake of existing knowledge. Since 2006 there have been a series of campaigns in England run by AHDB Beef & Lamb (the levy body for beef and sheep farmers) comprising paper and electronic literature and farmer meetings. The aims of the current study were, given the above technology transfer, to test the hypothesis that the prevalence of lameness in sheep had fallen since 2004 and farmers had changed managements of lameness, and to identify novel factors associated with low prevalence of lameness in 2013.

Section snippets

Questionnaire design and administration

A postal questionnaire (available on request) was developed by a group of researchers at the Universities of Warwick and Nottingham. Part of the questionnaire captured detailed information on the period prevalence of lameness, recognition of four foot lesions, management and treatment of lameness, ID and SFR and details about farm and flock. It was based on previous questionnaires designed for research into sheep lameness, available literature and expertise from within the group. Questions were

Response rate and descriptive statistics

A total of 1348 questionnaires were returned after two reminders. Questionnaires missing data on flock size or lameness prevalence were excluded from the analysis. There were 1260 (31.5%) usable responses. Not all respondents answered all questions. There were similar response proportions across counties. Some respondents were from hill or upland farms and others had <200 ewes. These variables were added to the models. The median flock size was 350 ewes (IQR: 230–550). The global mean

Discussion

This paper is the first study of a random sample of English sheep flocks since 2004 (Kaler and Green, 2008b); we provide new evidence that the period prevalence of lameness in sheep in England has fallen from 2004 to 2013 from a global mean of 10.6% to 4.9% and a geometric flock mean of 5.4% (sheep) to 3.5% (ewes) and 2.6% (lambs). The 2013 figures were for ewes only whereas the 2004 figures were asked for ‘sheep’ and the period lameness for lambs was less than that for ewes, so it is possible

Conclusions

This is the first observational study to demonstrate that routine foot trimming is not beneficial to lameness prevalence compared with not routine foot trimming and that as the proportion of sheep feet that bleed during routine foot trimming increases the prevalence of lameness increases. It is also the first to quantify the association between prompt treatment (within three days, and when less than five sheep were lame) and lower prevalence of lameness, and a lower prevalence of lameness in

Acknowledgements

This research was funded by Defra as part of AW0512. Joanne Winter was part funded by a University of Warwick Impact award. Laura Green and Jasmeet Kaler are funded by BBSRC (BB/M012980/1). We acknowledge Defra and AHDB Beef & Lamb for access to sheep farmers and, most importantly, we thank the sheep farmers for completing our questionnaire.

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