Data collated by NMR and by the University of Reading has demonstrated the impact of Johne’s disease on dairy cows. Speaking at Dairy UK’s industry conference: ‘Johne’s – Moving the agenda forward’ (October 10), NMR’s business development manager Ben Bartlett compared the performance of cows infected with Johne’s with those showing little or no infection.
Ben Bartlett, NMR business development manager
“Research conducted in the USA in 2005 compared the performance of 120 Johne’s positive cows with 120 negative cows. “This research showed that the Johne’s positive cows gave 4000kg less milk per cow over a lifetime, were five times more likely to be lame and were twice as likely to develop mastitis or somatic cell count problems,” reported Mr Bartlett.
“Keen to see if the same impact was evident in GB herds, NMR analysed nearly 4000 cows on the Herdwise surveillance service in 2011. We compared quarterly Johne’s test results with their NMR performance records.
“We found that Johne’s infected cows in this sample had lower 305-day yields even in their first lactation, suggesting that these cows suffer early in life – well before signs of Johne’s are detected through milk tests or visually,” says Mr Bartlett. “Infected cows – classified as ‘red’ cows on Herdwise, had yields around 20% lower than ‘green’ or non infected cows.
“And average cell count of affected cows was a third higher than non affected cows. We also found that cows infected with Johne’s had a Lifetime Daily Yield (LDY) – that takes account of production, health and fertility – of 11.5kg/day compared with 13.6kg/day for those with no infection.”
These findings are supported by a more recent University of Reading survey that compared Johne’s test results with NMR records for a group of 80 herds totalling 13,720 cows. Johne’s infected cows were found to be twice as likely to have high somatic cell counts and there were 50% more cases of mastitis in Johne’s infected cows.
“Johne’s positive cows had an average of 150 days calving to conception compared with 119 days for negative cows and age at first calving, which was 26 months for positive cows compared with 23 months for negative cows, would also suggest that the disease had a negative impact on performance early in the cow’s life.”
Looking at the prevalence of Johne’s in UK dairy herds, Mr Bartlett is convinced that more herds are affected than suggested in Defra’s report published in November 2009.
Of the 710 herds where NMR’s 30-cow Johne’s screening tests were carried out in 2011, 73% had at least one cow that tested positive. “Although this isn’t a huge sample, we are fairly confident that it reflects the situation in the GB herd,” adds Mr Bartlett.
“We have also analysed herds on our Herdwise quarterly Johne’s screening test and found that, of the 1000 herds analysed, 35% of herds have less that 2% ‘red’ cows - which are cows heavily infected with Johne’s and 62% of herds have less than 4% of red cows.
On a positive note, Mr Bartlett pointed out that those herds that are screening cows regularly through Herdwise are in a good position to control the disease. “Having identified affected cows they can then be managed separately, preventing further spread.
“NMR fully supports the different strategies for controlling Johne’s disease in UK herds that are being developed by the Dairy UK Johne’s Action Group. Producers, working with their vets, can adopt the most appropriate Johne’s management strategy given the individual farm circumstances - there’s one that will suit every British farm regardless of size, system, resource or disease level.
“We would strongly encourage British producers to grasp the nettle now and bring Johne’s under control.”
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