Abstract
Johne's disease (JD) is caused by infection with the organism Mycobacterium avium spp. paratuberculosis, leading to chronic diarrhoea and ill thrift in adult cattle. JD is considered to adversely affect farm performance and profitability. This retrospective case study was undertaken on a single commercial dairy herd in the south west of Ireland. Animal production records were interrogated to assess the effect of JD on milk yield (total kg per lactation), somatic cell count (the geometric mean over the lactation), reasons for culling, cull price and changes in herd parity structure over time. JD groups were defined using clinical signs and test results. One control animal was matched to each case animal on parity number and year. Specific lactations (clinical, pre-clinical and test-positive only) from 1994 to 2004 were compared between JD case and control cows. A significantly lower milk yield (1259.3 kg/lactation) was noted from cows with clinical JD in comparison to their matched control group. Clinical animals had an average cull price of €516 less than animals culled without signs of clinical disease. In contrast, little effect was noted for sub-clinical infections. These direct effects of JD infections, in combination with increased culling for infertility and increasing replacement rates, had a negative impact on farm production. Results from this study provide preliminary information regarding the effects of JD status on both herd and animal-level performance in Ireland.
Highlights
Johne’s disease (JD), called paratuberculosis, is caused by infection with the organism Mycobacterium avium spp. paratuberculosis (MAP), leading to chronic diarrhoea and ill thrift in adult cattle (Collins 2003)
JD infection is associated with reduced milk production (Lombard et al 2005), increased involuntary culling rates (Ott et al 1999) and increased calving interval and infertility (Johnson-Ifearulundu et al 2000; Raizman et al 2007)
This is of particular relevance to Ireland, noting concerns about MAP in raw milk (O’Reilly et al 2004), and the significant share (15%) Ireland has in the world powdered infant formula market (Anon. 2007)
Summary
Johne’s disease (JD), called paratuberculosis, is caused by infection with the organism Mycobacterium avium spp. paratuberculosis (MAP), leading to chronic diarrhoea and ill thrift in adult cattle (Collins 2003). JD infection is associated with reduced milk production (Lombard et al 2005), increased involuntary culling rates (Ott et al 1999) and increased calving interval and infertility (Johnson-Ifearulundu et al 2000; Raizman et al 2007). Concern has been raised over potential links between Johne’s disease in cattle and Crohn’s disease in humans, which may lead to international barriers to trade in milk and milk products, including infant formula. This is of particular relevance to Ireland, noting concerns about MAP in raw milk (O’Reilly et al 2004), and the significant share (15%) Ireland has in the world powdered infant formula market Farm performance prior to the disease outbreak was in the upper quartile of its peer group of milk monitored herds
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