NADIS is a network of 40 veterinary practices and six veterinary colleges monitoring diseases in cattle sheep and pigs in the UK.

NADIS data can highlight potential livestock disease and parasite incidence before they peak, providing a valuable early warning for the month ahead.


NADIS disease forecasts 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.
The forecasts are based on national trends and farmers are advised to discuss
their individual farm circumstances with their veterinary surgeon
.

ADULT CATTLE

Fertility
The number of fertility problems continued its fall from April.  Missed heats remained the most commonly detected problem, but in contrast to last year where the number of cases remained around 40% above average, the figures for May 2006 suggest that this year the number of cases will follow the usual summer pattern, with the average number of cases falling to about 60% of the number seen in the winter months. Nevertheless, on average, NADIS veterinarians report over 3500 cases during the summer, so although detecting bulling in cows at pasture can be very time consuming it is essential. Indeed when heat detection is done effectively submission rates at pasture can be significantly better than in housed cattle. Heat detection aids such as beacons and tail paint are particularly useful at this time of year. 

Figure 1: Monthly patterns for non-detected oestrus, showing the very high figures seen last summer

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Calving problems is another problem that is often forgotten about during the summer, however the NADIS figures clearly show that significantly more problems occur in the summer than the winter. In past years oversized calves have been reported as a particular problem, often in association with over fat dry cows. Although keeping condition on lactating cows at pasture is a significant problem, even for cows producing average yields, preventing dry cows gaining weight and condition at pasture requires careful management. Condition scoring at drying off and again one month later can identify potential problems early. Management changes needed may include keeping cattle on bare pasture and feeding them controlled amounts of silage and straw. It is also important to remember that fat cows don’t just have more difficult calvings, they are also more prone to most diseases that occur in early lactation such as metritis, mastitis, and lameness, and they are less productive.

Figure 2: The NADIS reports show that, although calving has become less seasonal since 1997, for dystocias the main change has been a small increase in the number seen during the winter period and no change in the number of summer problems

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One interesting problem reported by a NADIS veterinarian this month has been a poor recovery rate in cattle after caesareans. Further investigation suggested that there might have been a link with low copper and selenium levels. Both of these micro-mineral are associated with immune function so it is possible that deficiencies could be associated with poor recovery. In such cases there may be a case for liver biopsy during the caesarean operation to better assess status!
Abortions were at their usual low level in May, however June to August tend to be the months when most abortions are reported, so now is a good time to review your plan for dealing with abortion. Individual cases will always occur so you need to set an intervention level that triggers action. This needs good records to work properly; it is probably worthless examining a near-term abortion when you have a problem around four months of gestation. The simple rule when collecting material sample is to collect everything. In particular collect the placenta; this is often forgotten and can provide valuable information as to cause.
Stillbirth is also commonly reported during this period. It can be very difficult to investigate. A particular problem is iodine deficiency which was identified as the cause of problem by one NADIS vet in May. Unless cattle are on consistent rations diagnosis can be very difficult as blood iodine levels (PII) vary considerably depending on daily dietary intake. Blood thyroxine levels are also used but their link to iodine status in ruminants is not consistent, as they are very variable depending on the status of the cow.
Metabolic disease
The relative lack of dietary control in cattle at pasture means that the summer remains the peak period for metabolic disease. So far this year, except for displaced abomasums the number of metabolic disease cases has been below average. Both hypocalcaemia (milk fever) and hypomagnesaemia (grass staggers) had fewer reports in May than last year and the average for previous years. For grass staggers, May is usually a peak month so the low number of outbreaks suggests despite May being a relatively warm wet month grass growth wasn’t sufficient to cause severe problems. For hypocalcaemia the rise in cases is usually seen later in summer so relatively low levels now do not prevent significant problems occurring later in the summer. As for dystocia good management of dry cows is essential for controlling this problem and on some farms preventing access of dry cows to significant amounts of pasture may be the only solution.
 
Figure 3: Seasonality of reports for metabolic disease by NADIS veterinarians, showing the low levels reported so far this year.

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In contrast to most years the number of cases of displaced abomasum (DA) peaked in March this year rather than in April. However, the number of cases reported in May (70) were still almost 50% above the 1997 – 2004 average, so preventative measures are still essential, even with many cows out at pasture.
Cattle lameness
Summer marks a significant change in the risk factors for lameness on many herds. The risk factors change from those associated with housing (concrete and slurry) to those associated with pasture (tracks and gateways). In some cases, particularly if the weather is poor, there may be relatively little change. For diseases such as foul-in-the-foot the change from constant contact with slurry to constant contact with mud may not actually result in much change in risk, but for others there are significant impacts. For example the NADIS data show that sole ulcer is much more closely linked to housing than white line disease. Thus when lameness problems arise we need to identify the risk factors on each particular farm in order to effectively reduce the impact of lameness.

Figure 5: Seasonality in the total number of lameness reports by NADIS veterinarians.  There is definitely a seasonal bias towards winter, but it is much less marked than in previous reports. So far this year the trend has been similar, but the total number of reports has reduced.

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Figure 6: Comparison of reports of sole ulcer (SU) with those of white line disease (WLD). This shows that while sole ulcer is most common in the winter, white line disease is markedly more common in the late summer

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One disease which is definitely not as seasonable as it was originally is digital dermatitis. Significantly mores cases and outbreaks are being reported during the summer in the UK, and this pattern is also being reflected across Europe. More and more farms now have to keep using digital dermatitis control programmes throughout the grazing period.

CALF DISEASES
The number of calf scour outbreaks reported in May remained well below average in May. So this year the spring rise in scour outbreaks was about 20% below average, continuing a trend that began in September last year. It would be interesting to know why levels have been so low, whether it’s actually fewer outbreaks because of an improved on-farm position or whether it’s reduced reporting of such problems to vets. If it is the former we still shouldn’t be complacent as scour is still being seen in significant numbers of calves and in the average year, even though rates are at their lowest, the next four months account for over 20% of cases. Cleaning, disinfection and colostrum feeding remain essential control measures.

Figure 7: Seasonality of calf scour outbreaks, showing the low number of reports since Sept 2005. 

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In contrast to scour problems, the number of navel-ill and related problems, reported in May were higher than average, suggesting that environmental conditions on farm may be worsening. However, although the rise is statistically significant it is from a small base, so to use the navel ill data to say the calf environment is worsening may be over-interpreting the data (particularly as scour cases are low). Nevertheless, attention to the environment of the calf (at and after calving) is still important if such problems are to be prevented.
One interesting outbreak of calf disease was reported by one NADIS vet in May. An outbreak of pneumonia and scours was linked to feeding soya milk to calves. Soya milk products can be useful as part of the ration given to milk-fed calves, but if not properly produced they can cause significant problems as the raw soya product contains several anti-nutrition factors. More details would be useful of any similar problems in the future.

Copyright © NADIS 2006          

www.nadis.org.uk

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