1 August 2008

8 minute read

Europe

Bluetongue vaccination is progressing apace across the country. We have had a report from one NADIS veterinarian concerning abortion in 6 of 20 in-calf heifers after they received the vaccine. We would be very interested to hear if there are any similar problems.

Adult Cattle

Metabolic disease

The number of displaced abomasums (DAs) reported in June decreased significantly from the very high May levels. Nevertheless there was the same number of reports in June as in the same month last year. The NADIS data suggest that by year end there will have been between 670 and 700 cases of DA reported; much lower than the peak figures seen in 2004 – 6 but still far higher than any year before 2003. Since 2001 we seem to have seen a step change in the prevalence of DA, the cause of which is still uncertain.

Figure 1: Number of monthly reports of DA in 2008 and 2007 compared to mean of 1997-2006.

After an almost 100% rise in May, acetonaemia dropped back to low levels in June. June usually has the fewest number of reports of this disease, followed by a peak in July and decline to a similar level to that seen in June by October. Such changes are obviously feed related and vary considerably between years. Compared to DA cases the number of acetonaemia reports has not been as variable, however since 2004 they do seem to have followed a similar pattern.

Figure 2: Number of monthly reports of acetonaemia January to June for 2002 to 2008 compared to mean of 1997-2001

The number of milk fever reports fell in June, but just 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, with the NADIS figures suggesting that at the end of the year there will have been between 380 and 410 reports of milk fever, over 10% down on the previous lowest year which was 2007. It would be useful to know whether this fall is reflected in calcium sales!

Figure 3: Total yearly reports for milk fever from 1997 to 2007 with estimated results for 2008

The number of hypomagnesaemia cases reported in June was down compared to May, confirming that for the second year in a row there were fewer spring cases than ever before. Last autumn’s peak was also well below average but was not a record, it will be interesting to see what happens this year.

Figure 4: Comparison of the number of reports of hypomagnesaemia in spring and autumn, showing the much greater variability in autumnal reports

Mastitis

June is usually the first month when severe summer mastitis problems occur but this year there were only two reports. 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. One of the major changes seen in mastitis control in recent years has been an increase in the use of internal teat sealants. There are only limited data of their effectiveness against summer mastitis. NADIS veterinarians were asked how effective they thought internal teat sealants were in aiding the control of summer mastitis. The general consensus was that farms that use teat sealants don’t tend to have summer mastitis problems but that the incidence rate was generally too low to be absolutely sure that it was a benefit of the teat sealant. A Shropshire vet commented that most of the cases that he has treated were in suckler cows which wouldn’t have had any drying-off treatment. With the recent demonstration in New Zealand that internal teat sealants in dairy heifers can significantly reduce mastitis, it would be interesting if someone was brave enough to try teat sealants in suckler cows!

A Preston vet commented that summer mastitis does not always go up the teat canal into the udder; a lot is fly-borne and gets in through the teat wall. In such cases, the infection will still meet teat sealant as the sealant fills the teat cistern, but we don’t know whether the barrier at this point is less effective than against entry via the teat canal. Fly control thus remains an important part of summer mastitis control, although, 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

All of the three most common ovarian problems, non-detected oestrus, ovarian cysts and anoestrus, were reported less often in June than in May, consistent with the usual seasonal pattern. Only ovarian cysts were reported less than the long-term average, and this fall below average came after four months of markedly elevated figures.

Calving problems, abortions, dystocia and caesareans all fell appreciably from the very high May figures, though caesareans remained at more than 75% above the long-term. The number of uterine torsions remained high in June, with the highest ever number of reports for that month. 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, until this year, we seemed to have reduced from a peak in 2004 to lower but still elevated levels. However the NADIS data so far this year suggest 2008 will be a bumper year for uterine torsions.

Figure 6: Change in yearly reports of uterine torsion (with predicted number for 2008)

Lameness

All of the four main diseases decreased from their May peak and except for digital dermatitis, which had the smallest May peak and the smallest June fall, reduced to levels below those seen in 2007. We would be interested to hear any theories as to why so many lame cows were recorded in May. After a one month increase we are now back on the slow decline in lameness treatments by veterinarians.

Figure 7: Trends in monthly reports of lameness for 2007 and 2008 compared to the average of 1997 to 2006

Other diseases

After a very low number of cases in early spring, New Forest Eye cases have continued to steadily increase since March. Last year there were fewer cases reported during the summer and autumn than any previous year, with <60% of the cases seen on average. Despite the rises, this year looks set to follow the same trend.

Figure 8: Comparison of number of outbreaks of New Forest Eye recorded so far this year compared with 2007 and the average for 1997 to 2006

A Wiltshire vet last month saw, what appears to be a classic case of botulism. He saw two 18-month old heifers which were down with a flaccid paralysis. The field was an organic one but there was a large heap of chicken manure nearby, some of which had been dug into the soil. The chicken manure could not be moved until autumn because the farm was in a nitrate vulnerable zone so no more could be spread until then. Calcium and magnesium concentrations were normal in the heifers. The presence of the manure is strongly suggestive of botulism, as poultry litter contaminated with carcasses is the most common source of the intoxication. Such litter is very high risk as cattle will happily eat poultry manure and poultry carcasses can be spread to neighbouring fields by predators such as foxes and crows. Cattle should not be allowed access to fields on which poultry litter has been spread for at least 21 days after its application, and preserved forage should not be made from such fields. The vet wonders whether the risk of botulism will increase because of changes in chicken shed management with more production of litter which has to be disposed of some way. The affected cattle have been euthanased and reports of the PM’s are awaited.

Calves

Joint ill reports were, for the third month running, around the long term average. By comparison, last year only two months in the whole year were near that average.

Figure 9: Comparison of number of total number of reports per year for joint ill showing the relatively consistent decline in cases (dashed line)

These figures were reflected in both the calf scour and pneumonia reports, both of which are running at levels higher than last year but still below the long-term average

A classic case of lead poisoning in a beef bullock was reported in N Scotland. The main presenting sign was blindness. Despite the vet’s suggestions the farmer denied that the animal had had any access to lead; however after further searching the farmer found an old electric fence battery abandoned in the field which had disintegrated. Chewing marks were apparent on the case. Lead batteries are probably the most common cause of non-geochemical lead poisoning, and are a particular problem as they contain a solution of lead sulphate which appears to be very attractive to cattle which may even break open undamaged batteries to get to the solution.

A Powys vet saw an unusual case in a 3-month old beef calf which was out with its mother. The calf had a urethral blockage probably due to calculi. The vet suspected that this was caused by a mineral lick meant for the cows as the calf’s calcium: phosphorus ratio was the wrong way round with phosphorus being very high.

Further Reading

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