Prevalence and Temporal Dynamics of White Line Disease in Sheep: An Exploratory Investigation into Disease Distribution and Associated Risk Factors

Abstract

Lameness in sheep is a global health, welfare and economic concern. White line disease (WLD), also known as shelly hoof, is a prevalent, non-infectious cause of lameness, characterised by the breakdown of the white line. Little is known about the predisposing factors, nor the individual disease dynamics over time. Our exploratory study aimed to investigate the prevalence and temporal dynamics of WLD, and the associated risk factors. Feet of 400 ewes from four UK commercial sheep farms were inspected for WLD at four time points across 12 months. The change in WLD state at foot-level (develop or recover) was calculated for three transition periods. We present WLD to be widespread, affecting 46.8% of foot-level and 76.6% of sheep-level observations. States in WLD changed over time, with feet readily developing and recovering from WLD within the study period. The presence of WLD at foot-level, the number of feet affected at sheep-level and dynamics in development and recovery were driven by a variety of foot-, sheep- and farm-level factors. We provide key insight into the multifaceted aetiology of WLD and corroborate previous studies demonstrating its multifactorial nature. Our study highlights an opportunity to reduce WLD prevalence and informs hypotheses for future prospective studies.

New Insight into the Prevalence and Risk Factors for Three Distinct Hoof Conformation Traits in UK Commercial Sheep Flocks

“…Feet of ewes grazing new leys, or a mixture of permanent and new leys, were more likely to have lower hoof wall scores, but higher wall overgrowth scores. This is contrary to previous findings highlighting these pastures to be associated with white line disease [ 23 ]. Without analysis of the micro- and macronutrients provided by different grazed pastures, the effects of nutrient supply are unclear.…”

“…This is concordant with our understanding that sole horn, which is softer than wall horn [ 7 ], can wear and become damaged through the abrasive action of well-drained, brashy calcareous soils and coarse, long, stalky grass. Longer sward heights have been associated with increased risk of white line disease [ 23 ], footrot [ 19 ], and general lameness in sheep [ 34 ]. Although sole and heel damage could be indicative of a previous episode of SFR, as discussed previously [ 18 ], our finding that feet with signs of footrot are more likely to have higher sole and heel conformation scores aligns with work highlighting higher loads of D. nodosus on feet with sole and heel damage present [ 18 ].…”

“…Older ewes may be more prone to nutritional imbalances and laminitis, causing the production of low-quality hoof horn and greater susceptibility to damage. White line damage has been observed more frequently in ewes aged ≥ 4 years [ 23 ]. However, no association between age (≤4 years and >4 years) and degree of hoof shape or damage has previously been reported [ 17 ].…”

“…The study was a longitudinal, repeated cross-sectional field survey of four commercial sheep farms (identified as A–D) in England and Wales. Farm characteristics, study design and data collection are described in detail in [ 23 ]. Briefly, a minimum of 90 ewes were initially convenience selected from each flock, ensuring distribution between two age groups: <4 years and ≥4 years.…”

“…Data included farm soil type and flock footrot vaccination (Footvax®, MSD Animal Health, Merck & Co., Kenilworth, NJ, USA) status, in addition to estimates of pasture moisture, quality, type and sward height for each calendar month between August 2019 and September 2020. Meteorological data (average rainfall and temperature for each calendar month) were extracted from publicly available local UK MET Office station archives, as described in [ 23 ].…”