1 May 2008

9 minute read

Europe

Adult Cattle

Metabolic disease

For the first time ever (excluding 2001, when the FMD outbreak had just got started) the number of reports of displaced abomasums (DAs) in March decreased compared to February. The number of reports was almost half the number seen in the same month last year. This drop is all the more remarkable because since 1997 there has been a change in the seasonality of DA cases with the peak in cases has been moving backwards from April/May to February/March. However as Figure 1 shows this is more to do with a reduction in the proportion of cases in April/May than an increase in February/March

Figure 1: Proportion of yearly reports of DA in April/May compared to February/March

This means that, although the peak of DA cases has moved to March from May, what’s actually happened is that DA has become 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 2)

Figure 2: Change in seasonality of DA. The 1997-1999 figures show a clear peak in April/May, while the 2005-2007 figures show a smaller peak in March/April. It is important to note that almost 3 times as many cases of DA were reported in 2005-2007 than in 1997-1999.

In contrast to last year where very low levels in February were followed by an increase of over 200% in March, this year reports of acetonaemia fell in March. As with DA this is unusual as March usually sees an increase in cases. Clearly although the two diseases have some different risk factors there are strong links so it is likely that the cause of the fall in DAs in March also caused the fall in acetonaemia reports.

Comparing the seasonality trends shows that the changes in seasonality of acetonaemia have been less marked but similar to the changes seen in DA. In particular, overall there has been a reduction in the seasonality of the disease with the spring period becoming relatively less important and an appreciable increase in the proportion of cases in the early summer.

Figure 3: Change in seasonality of acetonaemia. The 1997-1999 figures show a relatively clear peak in March to May, while the 2005-2007 figures show two smaller peaks in March/April and July/August. Around 10% fewer cases of acetonaemia were reported in 2005-2007 than in 1997-1999.

Hypomagnesaemia and milk fever both remained low in March, particularly the latter. The low figures suggest that like last year it will be a good spring for staggers with around 60% of the long term average number of cases. So far this year the number of milk fever reports has been lower than any previous year, even 2001. The clear consensus among NADIS veterinarians is that farmers are increasingly treating milk fever cases themselves and not calling the vet in. It might thus be thought that the NADIS figures would show a decline in cases. However the picture is more complex than that. Between 1997 and 2000 there was a decrease in total cases seen of over 10% per year, however this was reversed between 2001 and 2004. Since then the decline has returned, again averaging at about 10% per year. Interestingly the decline in reports in January to March has been less marked, trailing the figures for the whole year. However figures for milk fever for the whole year and for the first three months are now at <50% of the figures reported in 1997.

Figure 4: Changes since 1997 in the number of reports of milk fever over the whole year and in the first three months

Fertility

The number of reports of non-detected oestrus and anoestrus remained low in March; with both having their lowest March figures except for 2001. These low March figures following low January and February figures suggest that fertility has been good since the turn of the year. Is this another indication of cows having good quality feed in front of them? The only major fertility problem to be significantly above average in March was ovarian cysts, which despite a decrease compared to February remained at almost 50% above the long-term average. We would be interested to hear what factors you think are keeping ovarian cysts rates relatively high.

Figure 5: Monthly reports of ovarian cysts

A Gloucestershire vet reported an unusual case of a barren cow which was doing poorly two months after aborting a 7-month old fetus. On examination she was found to have the remnants of a second calf left inside her. The vet was surprised that this calf was not very smelly. The cow was treated with penicillin and left to expel the rest of the dead calf which mainly seemed to be bits of bone. It is surprising what a cow can cope with, they can do very well with dead calves left inside them. In New Zealand, where this happens significantly more often, this is often referred to as the crock-pot or slow cooker method of calf removal.

Lameness

The OTMS scheme has been effectively dismantled for over two years. Lame cattle that are not fit for transport are thus worthless unless they fit the criteria for the OCDS. It might have been thought that this would mean that there would be more veterinary treatment of lame cows however this has clearly not been the case with the overall number of lameness cases continuing to decline. Overall lameness reports in 2007 were lower than in any previous year and 2008 has continued this trend with overall figures so far this year being just over 80% of the already low 2007 figures to the same date. We need to know whether this reduction reflects the situation on the ground or whether it reflects reduced veterinary involvement. The first is good news, the second is not! Lameness is the most important welfare problem in dairy cattle and the NADIS data are the most current and widest ranging data we have on its prevalence. With a bit more support from government the data could identify clearly whether the reduction in lameness is real.

Figure 6: Number of reports of lameness in January to March from 1997 to 2007.

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 around 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.

There is no evidence that this increased use of teat sealants has had an effect on the rates of acute toxic mastitis reported by NADIS veterinarians. Although the figures so far this year are historically low at only 50% of the average since 2001, the figures for previous years show no continued downward trend (Figure 7)

Figure 7: Yearly reports of acute toxic mastitis since 2002 showing no evidence of any significant trend

Other diseases

Bovine iritis (silage eye) cases usually peak in March as the final silage of winter is fed out. However this year’s figures have been much lower than normal and lower than 2007 which was already very low. These low figures are likely to be partly due to better farmer appreciation of the problem with feeding pure quality baleage. However it is likely that better recognition of the problem by farmers has reduced the likelihood of the vet being called to see a problem in the herd. When combined with additional data from focus farms, the NADIS data could be used to answer which of these causes are the more important, providing valuable information on an important and painful disease, which is the most commonly reported disease caused by Listeria in cattle.

Figure 8: Reports of bovine iritis by month showing that the peak of cases has been much lower in 2007/8 than average.

A Lancashire vet described an unusual problem in ten newly calved heifers. They were all thin and poor-looking. The worst affected had swollen carpal joints and was unable to stand. She was euthanased and necropsied by the local VLA laboratory. No significant findings were found on PM, but it is suspected that Mycoplasma bovis may be the underlying problem.

The same vet also reported some unusual findings on a TB test in a farm which vaccinated cows for Johne’s disease. On TB 90% of the herd had lumps, only 2 were inconclusive but the rest passed the test. He thinks the 2 IR’s were due to Johnes vaccination and is wondering whether any one else has experienced the same thing as he was amazed by the number of animals that had lumps and size of those lumps.

One NADIS vet reported a particularly distressing problem in March. He was called out to see 2 downer and 3 dead cows. Fluke had been diagnosed 2-3 months previously but no treatment had been given. All of the animals were at or around calving. Post mortem confirmed significant liver damage due to fluke.

Another examined an adult Highland bull that was itchy and had hair loss and lot of lice eggs. The bull had been treated three times over the last six weeks, twice with Spot On and once with Dectomax Pour On. He reported that the ineffectiveness of skin application of insecticides in hairy cattle is a recognised problem. In order for pour-on products to be effective, the hair needs to parted down to the skin in order to get the preparation on. Even then very long hair may make it difficult to get enough chemical to come out to the end of the hair, and repeat applications may be needed. We would be very interested to hear of any similar problems.

Calves

Following the trend since 2003, the March figures for calf scour were much lower than the long-term average. Indeed last months figures were the lowest ever recorded, being even lower than the figures recorded in 2001 at the height of the FMD outbreak. Reports from NADIS veterinarians suggest that it is a combination of better management and more farmer treatment that is driving this downward trend. More focussed research is required to identify which of these two factors are the most important

Figure 9: Change with time relative to 1997 cases in the number of reports of calf scour between January and March

Further Reading

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