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NADIS Veterinary Report and Forecast April 2009

19 May 2009

UK - This is a monthly report from the National Animal Disease Information Service (NADIS), looking at the data collected from their UK farm inspections

Adult Cattle

Metabolic disease

Unlike last year, displace abomasum (DA) reports were higher in March than February. Vet 22 (Somerset) reported that he was seeing a surge of LDA’s, which he suggested may have been linked to changes in day length and cow behaviour/feeding patterns as several of the cows he operated on did not have too heavy body condition or milk fever or any other known concurrent disease problems.

Last year the peak number of DA cases occurred in May, the first time the peak month had been that late in the year since 2003. This was unexpected since 1997 the peak in DA cases has moved backwards from April/May to February/March, alongside DA becoming a less seasonal disease. At the start of NADIS in 1997-2000 it was very much a late-winter/spring disease, with over 50% of cases occurring between February and May, but in the last few years this proportion has fallen to just over 40% (Figure 1), with even the delay in peak cases last year making little impact.

Figure 1: Change in seasonality of DA. The 1997-1999 figures show a clear peak in April/May, while the 2005-2008 figures show a smaller peak in March/April. It is important to note that almost 3 times as many cases of DA were reported per year in 2005-2008 than in 1997-1999.

It would be useful to be able to predict the likely number of DA cases from previous month’s data. If all the data from 1997 onwards are used there appears to be good correlation between months – e.g. for March and April r = 0.6, which is a reasonable and significant figure. However this figure is artificially inflated because of the massive increase in cases since 2001, so low figures in March are linked to low figures in April because of the year they are in rather than because of a strong connection between months. If data from 2002 only are used r falls to 0.16, both non-significant and of no practical value. This highlights our lack of understanding of the factors driving rates of displaced abomasum.

Hypomagnesaemia cases were relatively high in March, indicating that there may be a high number of cases over spring, a situation we have not really had since 2004.

Fertility

The number of caesareans reported in March was double the number reported last year – in contrast the number of dystocia cases was around the same. Current NADIS reports have a strong seasonality for calving problems with a prominent peak in May; it will be interesting to see if this rise in caesarean continues through the rest of the spring calving season. Suggestions as to why the proportion of dystocias that require caesareans has increased would be appreciated. Vet 12 ( Cumbria ) commented that he has done a lot of caesareans on animals that were borderline for requiring a caesarean. He suggested that the current value of such animals may be one driving factor with two 6 month old calves that the vet delivered by caesarean being recently sold for £13,000 and £10,000.

Figure 2: Comparison of 2009 figures for caesareans with those for 2008, showing the much higher numbers reported so far this year

Vet 46 (North Yorkshire) reported that the main problem in large dairy herds is a high level of endometritis, which is not associated with classical risk factors such as assisted calvings and milk fever. He has instituted an aggressive treatment regime on affected farms with cattle being examined and treated if necessary within 7-10 days of calving. On some farms this appears to be a successful strategy but on others it does not prevent a proportion of cows from developing chronic endometritis cases. He asks whether other vets have a regime which prevents this or cures these long running cases. While we understand the pathogenesis of endometritis, our understanding of factors determining response to treatment is less developed. Repeated treatment is often suggested, with combinations of prostaglandins and antibiotics often being advocated for cases which don’t respond.

Lameness

For the first time since 2004 the number of cases of lameness reported in the January to March period has increased compared with the previous year. However this may be a blip due to the large number of reports in January as the figures in both February and March have been below those reported in the same month in 2007. Furthermore as Figure 3 shows, this increase is a small change in a decline of almost 50% in reports.

Figure 3: Number of reports of lameness in January to March from 1997 to 2009.

Mastitis

The main change in mastitis control over the past 10 years has been the greatly increased use of internal teat sealants. They now account for over 25% of the dry cow therapy market, and that number is increasing year-on-year. Combined therapy is by far the most common use with over 90% of tubes being used after an antibiotic, despite the obvious increase in cost of the combined therapy. Anecdotal evidence suggest that in most cases teat sealants are used in addition to the standard dry cow antibiotic on the farm. Very few farms are using selective dry cow therapy, i.e identifying low cell count cows and giving those a teat sealant only and treating the rest with combination therapy, and even fewer are changing the antibiotic they use to take advantage of the protection against infection at the end of the dry period provided by the teat sealant. Reports of the use of teat sealants would be very welcome, particularly the process of how combined therapy is chosen.

Mastitis reports from NADIS vets remain at low levels well below those seen in the late ‘90s, however there’s no evidence that levels are decreasing which suggest that the low levels are caused by reluctance to pay for the vet to see clinical cases rather than an actual decrease in cases. This conclusion is supported by the sales of milking cow tubes and the gradually rising national cell count figures.

Figure 4: Monthly reports of clinical mastitis showing the much lower levels seen in 2007/8 than in previous years.

Other diseases

The general trend in cases of bovine iritis is for outbreaks to peak in January and then decrease until the start of autumn. However this year’s figures have increased since January and reached levels not seen since 2004. This suggests s some very poor quality baleage and silage was fed during March.

Figure 5: Reports of bovine iritis by month showing that the increase in the number of reported outbreaks since January.

Calves

There has been a significant rise in the number of reports of pneumonia this year compared to last. As with lameness this is the first time this has happened in several years, suggesting that the cold and variable weather at the end of the winter period has allowed the multiplication of the many pathogens which cause pneumonia in housed stock. Nevertheless, again following the pattern seen for lameness, this is a small rise on a large decrease in numbers of reports.

Vet 82 ( Caithness ) reported sudden death in a beef calf due to necrotic tracheitis and severe pneumonia. Initial tests suggest IBR as the cause but investigation is ongoing as the calf was only 3 weeks old and the vet has not seen IBR in calves of this age before. IBR is much more commonly reported in cattle over 6 months of age but with a potential incubation period of < 10 days it is can be seen in very young animals.

Figure 6: Reports of pneumonia in the January to March period showing the marked decline in reports since 1997.

Further Reading

More information - You can view the full report by clicking here.


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