NADIS Cattle Report and Forecast – July 2006

Figure 1: Monthly patterns for non-detected oestrus, showing the marked increase in cases seen in June and the very high figures reported last summer
 
June also saw an increase in the already high levels of endometritis reported by NADIS vets. The number of endometritis cases seen so far this year has been the highest of any year since 1998, continuing a trend of steady increase since 2001. Interestingly, like missed heats, 2005 saw a very high number of summer endometritis cases, with 34% of all cases reported between June and August (in contrast to the average of 28% in previous years). Again, 2005 appears to have been an unusual year as there was no previous trend towards an increase in endometritis cases during the summer

Figure 2: The NADIS reports show that, although last year the number of summer cases of endometritis increased markedly the long term trend is one of stability rather than change.
 
Another fertility problem which was much more common in June than average was uterine torsion, with the figures in June being very similar to the very high figures reported in May, confirming that the figures for that month were not an aberration. The number of cases of uterine torsion has increased greatly since 1997 and seems to be following a linear trend upwards, with an average of ten cases more per year. The cause of this trend is unclear but is probably associated with changes in genetics resulting in larger cows (with more abdominal space) and heavier calves (increasing potential torsion forces).

Figure 3: Change in the number of yearly reports of uterine torsion from 1997 to 2005 (with prediction for 2006), with linear trend line. The linear trend is statistically significant and explains over 75% of the variation between years 

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. This remained the case for hypomagnesaemia (grass staggers) during June, which meant that this year has been a good year with the number of reports being less than 60% of the average. It is likely that the effect of the poor weather in April on grass growth and turn-out significantly reduce the risk this year. It will be interesting to see whether a similar effect occurs during the autumn peak as this has been much more variable in recent years than in the past. In contrast to hypomagnesaemia, reports of both hypocalcaemia (milk fever) and acetonaemia (ketosis) cases increased in June, though neither was at unusually high levels. Displaced abomasum reports, however, were at their highest ever level for June.  This means that despite a lower peak in cases, overall figures for 2006 are very similar to those of 2005 which were the second highest ever (after 2004).  Although the peak number of cases is March to May, over 30% of DA cases occur in the next four months, so we need to keep implementing preventative measures even though many cows will be out at pasture.

Figure 4: Change in the number of reports of displaced abomasum between January and June for 1997 to 2006, with linear trend line. The linear trend is statistically significant and explains over 80% of the variation between years. On average there has been an increase of 45 cases during this period per year over the last 8 years
 

Cattle lameness
The dry and warm weather in June was marked by low levels of lameness overall, with decreases in sole ulcer and digital dermatitis. Foul-in-the-foot cases increased despite the dry weather but still remained below average, while white line disease cases increased to average. 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 particular, increases in white line disease can be linked to poor cow tracks and management of cattle entering the collecting yard. Peak levels occur in September/October but the damage that eventually results in clinical disease starts long before then, so on farms with a history of white line disease paying attention to tracks now can significantly reduce future problems.

Figure 5: Seasonality of cases of foul-in-the-foot reported by NADIS veterinarians, showing that the number of reports per month has been consistently low so far this year.
 
CALF DISEASES
The number of scour cases remained low in June continuing the trend seen in the rest of the year. Indeed this year’s trend follows the pattern seen since 1997 of a decrease in veterinary reports of scour problems (and is similar to the trend seen in the data from the VLA/SAC). On face value this seems like good news, diarrhoea and its consequences, particularly dehydration, are the primary causes of calf loss, so a reduction in incidence can only be a good thing. However this simple evaluation misses the possibility that economic factors, such as poor calf values, rather than reduced diarrhoea may be the primary driver of the reduced veterinary reports. We urgently need a better measure of actual incidence of calf diarrhoea on farm.

Figure 6: Change in time with number of scour outbreak reports showing the almost continuous decline in the number of reports by NADIS veterinarians since 1997 (2006 data estimated)
 
No lungworm cases have been reported by NADIS vets since January, which is not unusual as July is usually the first month of the lungworm season. Recent years have seen higher peaks of disease in August/September so a focus on prevention now is still likely to result in significant benefits.
Copyright © NADIS 2006           www.nadis.org.uk