NADIS Veterinary Report and Forecast – July 2007

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

30 July 2007

9 minute read

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CATTLE

The start of the “summer” has been amazingly wet with England receiving over 3 times more rain than average in June and continued rain at the start of July. Following the pronounced dip in veterinary activity during the warm and dry April, this month’s figures are a further chance to see whether this drop was the start of a trend or just a consequence of the beautiful spring weather in many parts of the country, particularly as May’s figures, except for lameness and non-detected oestrus, were similar to those seen in April suggesting that the dip wasn’t just weather-related. Generally in June most diseases followed their usual trends but veterinary activity overall was down on average.

ADULT CATTLE

Metabolic disease

The number of displaced abomasums (DAs) reported in June increased slightly compared to May and for the first time in three months were significantly above the long term average. Nevertheless, the NADIS data suggest that by year end there will have been between 630 and 690 cases of DA reported; lower than in any year since 2001. Are we beginning to see a downward trend? If so is this because preventative measures are finally being put in place or was the high prevalence in the past five years a statistical blip similar to that reported by Roger Eddy in the early 1980’s?

Figure 1: Number of monthly reports of DA in 2007 and 2006 compared to mean of 1997-2005.

One vet described a severe DA problem on a client’s farm. This was associated with other intestinal problems including gut stasis, inappetance and, in one case, a perforated abomasal ulcer. The problem seems to be the lactation ration; he also suggested that there may be an underlying fatty liver problem. Investigation so far has been limited by the farmer’s willingness to spend money despite the obvious losses.

After a 200% rise in March and an almost equivalent drop in April, acetonaemia reports remained static in May and June. This meant that we haven’t seen the usual seasonal fall in cases and that so far this year the number of acetonaemia reports has been below expectations except in March. Ideas as to why this is the case would be welcomed.

Figure 2: Number of monthly reports of acetonaemia in 2007 and 2006 compared to mean of 1997-2005

The number of milk fever reports, like last year, rose significantly in June, but as they have since January remained well below the long term average. So far this year the number of milk fever reports has been lower than any previous year except for 2001. Indeed the NADIS figures suggest that at the end of the year there will have been between 420 and 480 reports of milk fever, well down on other years, including 2001. Thoughts as to why this is the case would be gratefully received. Milk fever remains a significant problem on many farms so its prevention is likely to remain a major veterinary role. If vets are not involved in milk fever treatment and control then both economics and animal health will be suffering. There is always a positive spin that there is less veterinary involvement because we have the disease under control, this is partially supported by the slow and relatively consistent decline in cases seen since 1997. We need more data!

Figure 3: Total yearly reports for milk fever from 1997 to 2006 with estimated results for 2007

The number of hypomagnesaemia cases reported in June was the same as May confirming that spring 2007 saw the fewest ever reported cases of hypomagnesaemia. It will be interesting to see what happens during the autumn peak.

Figure 4: Comparison of the number of reports of hypomagnesaemia between March and June for each year since 1997

Mastitis

June is usually the first month when severe summer mastitis problems occur but this year there was only one report. At this stage it’s difficult to predict what this summer will be like, but there’s no evidence from the NADIS data that global warming is bringing the peak of cases of summer mastitis earlier. Teat sealants seem to be a logical choice for preventing summer mastitis, however there is a lack of published evidence of how effective they are. We would be very interested to hear any reports of their use.

Fly control is an important part of summer mastitis control, however particularly in severely affected areas fly control can be difficult to achieve. A West Glamorgan vet reported that several of his clients are using a garlic laced lick to help keep off flies and finding it very effective. Does anyone else have an effective alternative to insecticides?

Fertility

After a return to normal in May following a very quiet April the number of missed heat reports remained static in June. This figure which accounts for the majority of all fertility reports is a good barometer for veterinary activity. The figures for this year suggest that, overall, veterinary input on farm is lower this year than last and for most years (excluding 2001), which is consistent with the data on most of the other diseases.

Figure 5: Number of reports of non-detected oestrus showing the relatively consistent nature of reporting totals since 1997, and the low level of reports so far this year (and the low predicted number)

The number of uterine torsions increased in May and also, unusually, in June. This condition like DA has been linked to large cows with large volumes of abdominal space, and like DA has been seen at higher levels recently. Furthermore like DA cases we seem to have reduced from a peak in 2004 to lower but still elevated levels.

Figure 6: Change in yearly reports of uterine torsion (with predicted number for 2007)

The number of abortions reported during the period from January to April was much lower than normal. This began to change in May and reports increased again in June, but the reports still remained well below average. If this year follows the same trend as last there will be far fewer reports of abortion than average. Is this less vet involvement or fewer abortions?

We have had some interesting case reports of abortion recently. An outbreak of abortion in cattle was reported in Powys due to Border disease virus (the usually sheep-associated relative of BVD). The cows were not vaccinated against BVD; the question is whether BVD vaccination would have helped. It’s certainly possible that there may be some protection as the two viruses are quite similar, but does anyone have specific experience of its use? Another Welsh vet submitted the fetal membranes from an abortion. Yersinia was isolated on culture. This bacteria has been associated with abortion in the past but is an unusual cause. Further tests are ongoing.

Lameness

After a dramatic rise in May from very low April levels, overall lameness cases remained static in June, though all the four major diseases decreased in June, particularly digital dermatitis which fell to almost 40% of the June average. So there was no evidence that the very wet conditions resulted in increased lameness over the short term. However as the development of lameness is a slow process, particularly for hoof horn disease, the impacts of the downpours may not be seen for another one or two months.

Figure 7: Trends in monthly reports of lameness for 2006 and 2007 compared to the average of 1997 to 2005

Despite the reduction in cases overall there are still too many farms with severe lameness problems. A report from Yorkshire illustrated a typical problem. A 75-cow dairy farm had 32 lame cows. Investigation showed that the cows were reluctant to lie in the cubicles as they were too small. They are now looking at ways to change the layout of the cubicles to accommodate the cows more comfortably.

Other diseases

The high number of New Forest Eye reports in May suggested that this summer looked likely to be a bad one, however the wet weather in June seems to have impacted on the usual summer increase in cases, so particularly if the weather remains wet it could be a good year for New Forest Eye with fewer affected cattle and less use of antibiotics.

CALVES

The NADIS figures clearly show that the number of calf pneumonia and calf scour cases have fallen markedly in recent years, as have the number of reports of joint ill and associated diseases. This year there was no rise at all in cases of scour during early spring. Figure 8 summarises the fall in reports between March and June since 1997. Clearly there has been a dramatic decline in the number of outbreaks seen by NADIS vets. As scours are recorded on an outbreak basis part of this fall is because of the decline in the number of dairy farms (fewer farms means fewer outbreaks), but this is not the whole explanation. Questioning of the NADIS vets has identified other possibilities. A Somerset vet stated that he thought that the falls were related to more time being spent on calf health, with cleanliness being a top priority for most large herds especially for their calves. He also thinks that pneumonia cases are now being treated better by farmers (newer antibiotics and more use of anti-inflammatory drugs) so vets are less likely to be called out. Increased vaccine use was highlighted by many NADIS vets. An Angus vet commented that he now sells more vaccine for pneumonia and fewer antibiotics and that control of BVD and rotavirus by vaccination has greatly improved the control of scour and pneumonia. Numbers of calves on farm was also highlighted by several vets. Fewer calves on farm leads to less disease, so the practice of selling bull calves rather than rearing them has a significant benefit for those calves left on farm. The responses tend to suggest that the reduction in cases is a reflection of improved disease status, rather than reduced use of the vet (although this is undoubtedly a factor in the fall).

As with all trends there will always be exceptions. This month a Caithness vet reported that his practice had never seen so many calves with pneumonia especially after turn out.

Figure 8: Change in reports of calf scour between March and June over the period from 1997 to 2007

An unusual case of clostridial disease in Powys. Three apparently healthy calves died suddenly after playing up in the crush, necropsy suggested that there had been clostridial invasion of the muscles of the neck, perhaps as a result of bruising by the crush.

Another NADIS vet reported on an all too common clostridial problem, tetanus. He diagnosed the disease in a beef calf that had been castrated using a rubber ring well after the legal limit. Clostridial vaccination is effective and cheap. There is no excuse for tetanus after castration. Clearly in this case the lack of vaccination combined with the significant amount of dead tissue resulting from the necrosis produced by the band to produce a fatal disease.