|NADIS is a network of 40 veterinary practices and six veterinary colleges monitoring diseases of cattle, sheep and pigs in the UK.|
|NADIS data can highlight potential livestock disease and parasite incidences before they peak, providing a valuable early warning for the month ahead.|
|NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare. Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.|
The very warm and dry April seems to have been associated with very low vet activity throughout the country with falls in many conditions to levels well below the long term average. The number of displaced abomasums (DAs) reported in April was just over half that reported in March and below the long term average (1997 -2005) for the first time since 2000. This suggests that like last year the number of DA cases will have peaked in March (although the fall off was much less precipitous in 2006) rather than April and May as has been the trend in past years.
We would be very interested to hear any ideas about what drives the seasonality of DAs. Is it the weather or is there an association with turn out. Nevertheless despite the large drop this month high DA levels seem here to stay and the industry seems to have just accepted this as another problem of modern dairy farming?
Figure 1: Number of monthly reports of DA in 2007 and 2006 compared to mean of 1997-2005.
After a 200% rise in March acetonaemia reports fell back to well below their long term average in April. Again the warm settled weather is likely to have played a significant part in this fall.
The number of milk fever reports failed to show its usual rise in April. So far this year the number of milk fever reports has been lower than any previous year except for 2001. It might be thought that milk fever treatment would be of gradually reducing importance, at least from a veterinary perspective, as more farmers treat their own cases. However the picture painted by the NADIS data is more complex. Although the general trend is downwards, the slope is slow (at just over 2% per year) and the individual variation between years is very large.
This is particularly the case for the first three months of the year where the evidence for any reduction is poor. We would like to hear your thoughts on what’s driving the slow decline in total numbers and whether you’ve seen a change in seasonality of the disease. The data so far this year suggest that milk fever levels will remain low until at least July so farms with higher than average cases or with outbreaks should be closely investigated.
Figure 2: Changes since 1997 in the number of reports of milk fever over the whole year and in the first four months
AS would be expected hypomagnesaemia cases increased in April, following the usual seasonal pattern though actual numbers were about 50% down on average which based on NADIS data from past years means that the risk of grass staggers in May and June is likely to be low this year.
All of the main fertility problems reported by NADIS veterinarians reduced with non-detected oestrus and endometritis reports both falling to levels far below those recorded in any month in the last ten years. We would be very interested to hear independent verification that these two diseases have dropped in incidence as dramatically as the NADIS figures suggest.
Other diseases have not dropped as far, both anoestrus and ovarian cysts fell but followed the usual pattern of a moderate decline in April compared to March.
Overall lameness cases dropped by almost 50% in April, with dramatic falls in all four of the major diseases. The largest fall was for digital dermatitis with only four reports in April against a long term average of over 40!
A mid Wales vet reported an unusual outbreak of lameness in a herd at turn out. On being released from winter housing 2 cows broke their cannon bones while running round the yard and 8-10 animals appeared stiff. Selenium, calcium and phosphorous were normal so the vet suspected vitamin D deficiency. PM results and confirmation are awaited.
The animals which were stiff have not been treated. They still seem sore but are gradually getting better but seem sore. The cattle had been fed on silage and a commercial concentrate to which vitamins had been added. Any comments would be much appreciated.
Bovine iritis (silage eye) cases usually peak in Feb-April as the final silage of winter is fed out. However this year’s figures have been much lower than normal and lower than 2006 which was already very low and April continued that trend.
These low figures suggest that the quality of baleage is probably better this year than average, although it cannot be discounted that the reduction in cases is due to vets being less likely to be called out to see such cases. This highlights that with a bit of additional support the NADIS data would provide even more valuable information on an important and painful disease (it is the most commonly reported disease caused by Listeria in cattle).
Figure 4: Reports of bovine iritis by month showing that the peak of cases has been much lower in 2006/7 than average.
Reports of malignant catarrhal fever have been relatively high this year having been noted by both NADIS veterinarians and the veterinary surveillance laboratories. A Yorkshire vet reported that a dairy farm lost 6 heifers over the winter to a progressive respiratory disease which was not responsive to any treatment.
A post mortem showed consolidation in lungs and blood was positive for malignant catarrhal fever. We would be interested to hear of other similar cases.
Another interesting report came from the North of Scotland. A cow that went down after vaccination with a vaccine for calf enteritis. The treatment given was systemic phosphorus. The vet suggested that this was a condition he had seen and treated before. Is this also the case for other veterinarians?
In April both calf scour and enzootic pneumonia remained at levels well below the long term average, with both being the lowest ever recorded. Again it’s unclear whether these reductions are due to better disease control or less use of vets.
Additional support to collect more data, such as that from sentinel farms, would greatly enhance the value of the NADIS data. We would be very interested to hear all opinions on how much of the low level of calf disease is due to it being actually less common or less commonly seen by vets.
A problem was reported in a calf-rearing unit in Devon with less than ideal conditions which lost 60 calves over the winter. Haemophilus and Mycoplasma bovis were grown in culture from one animal which was also positive for Salmonella Dublin. There were significant differences between groups with calves that had been fed on a machine being the worst affected, while those in old heifer housing which were fed by bucket doing significantly better. The suspicion was that despite the machine being cleaned every night this was not sufficient to prevent disease spread through the machine.
Figure 4: Change with time relative to 1997 cases in the number of reports of calf scour between January and April
Copyright © NADIS 2007 www.nadis.org.uk