Abstract
Bovine hock lesions present a serious welfare and production issue on dairy farms worldwide. Current theories suggest that trauma is an important factor in the formation of hock lesions, although infection may also play a role in increasing their severity and duration. Digital dermatitis (DD) lesions in dairy cows are strongly associated with specific treponeme bacteria which are opportunistic invaders of other skin regions. Hock lesions were tested to ascertain if they too contained treponemes. Swab and tissue samples were taken from hock lesions from two farms in South West England. Hock lesions were classified into two categories: open lesions, which were often bleeding and ulcerated, or were encrusted; and closed lesions, which were classified as hair loss with no skin breakage. PCR assays and bacterial isolation were used to detect treponemes in hock lesions. All three phylogroups of digital dermatitis treponemes were detectable and isolated from open hock lesions only, with closed lesions showing no evidence of treponeme infection, either by PCR or bacterial culture. When analysed by 16S rRNA gene sequencing, the cultured treponeme DNA showed complete homology or was very similar to that found in foot lesions. Additionally, skin swabs from near the open hock wounds were also positive by PCR assay and isolation for the DD treponemes. Identification of the contribution of these infectious agents will allow for more optimal treatments to be developed that reduce the prevalence and healing times of both hock and DD lesions.
Highlights
Hock lesions are a major problem for farmers worldwide, affecting a large number of cattle, causing significant welfare issues
Spirochaete isolations from tissues None of the tissue samples taken from unaffected animals showed any signs of treponeme presence or growth in culture, when analysed by phase contrast microscopy and the tissue and bacterial cultures were negative when tested by the nested PCR assay for all three digital dermatitis (DD) treponeme phylogroups
Of the seven tissues taken from open hock lesions, all of the resulting cultures were positive for treponeme growth upon analysis by phase microscopy, and this was confirmed by Treponema genus PCR assay and nested PCR assay for all three DD treponeme phylogroups (Table 1)
Summary
Hock lesions are a major problem for farmers worldwide, affecting a large number of cattle, causing significant welfare issues. This can be through discomfort and pain to the animal, as well as leading to production issues and decreased longevity (Huxley et al, 2006; Bareille et al, 2003; Barberg et al, 2007). Contradictory data exists about body condition score of cattle and risk of developing hock lesions (Kielland et al, 2009; Potterton et al, 2011; Espejo et al, 2006; Bicalho et al, 2009; Regula et al, 2004). Decreased numbers of hock lesions are reported in organic and outdoor farming, whilst there is contradictory information with regards herd size contribution (Rutherford et al, 2008)
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