A few years ago cattle in an American feedlot went down during transport to a packing plant, and others developed severe lameness. This condition was eventually labeled fatigued cattle syndrome (FCS) and became a huge animal welfare issue due to the appearance of severely lame, non-ambulatory cattle.
Initially beta agonists were incriminated but numerous studies have essentially proven that it was a combination of other factors that precipitated this condition. However, Dr. Dan Thomson of Kansas State University, and a team of researchers in production animal medicine, determined several stressors that led to FCS. From this discovery there were a number of preventative measures feedlot operators could use to prevent this condition.
FCS has some characteristic symptoms but they can be confused with other syndromes such as acute laminitis due to grain overload, or selenium/vitamin E deficiencies. Symptoms of FCS include a strained pattern of breathing as well as very slow movements leading to non-ambulatory cattle. In severe cases there has been sloughing of the hooves.
Contributing factors to FCS are possibly preventable. The heat load contributed as the initial cases appeared in temperatures around 35°C. The specific findings may lead to specific recommendations in our upcoming Canadian transportation Code revision and we need to be even more careful handling transporting and butchering cattle in the summer for these reasons. Depending on distance travelled or the number of cattle moved and sorted perhaps a safe maximum temperature will be found. We also know that hide color has a lot to do with heat stress and these tolerable temperatures may go down as the demand for black hided cattle goes up.
I was privy to a very descriptive video showing heat stress in a pen of mainly black hided cattle. While the majority of the cattle were in the shade of a porosity fence and breathing heavily, the red and white cattle were up at the feed bunk eating. Of the few cattle I have treated for heat stress over the years all have been black hided. Cattle handling, the distance to be loaded, the distance traveled, and the related stress during movement all contribute to FCS. These may all seem like common sense observations, and they are. Until this specific syndrome appeared there was no reason to suspect we had a problem.
The researchers also performed tests on the blood looking at muscle enzyme levels to see if any damage was done. In affected cattle the levels were very high. This is also found with downer cattle or calves with white muscle disease.
Dr. Thomson and his group found that aggressive handling produced the same muscle enzyme levels as running a seven or eight-minute mile or walking for about 20 minutes. We can all identify with this. If we run too far when we’re not used to it, our muscles can become extremely sore for a few days due to the build up of lactic acid.
Feedlot cattle these days are getting bigger, and when they are in prime condition for butchering they are not athletic enough to be running around for any amount of time. In some large feedlots the home pen may be more than a mile from the load out area and that had a bearing on the incidence of FCS, so changes may need to be made in lot design. It may require staged moving or more load out areas.
FCS was even more prevalent at the packing plants. Some common factors contributing to FCS at the plants were the time the cattle remained in the pens before slaughter and whether shade and cooling were available, particularly in areas with very hot climates. Cattle density in the pens was another factor. When holding pens get too crowded the cattle cannot properly dissipate heat.
Animal handling practices and facilities were also examined. Stress, exertion, and rough handling can often be reduced by better facilities or staff training. The type of flooring was also looked at as some floor surfaces can cause injuries to the feet.
In the U.S., discovering the causes of FCS has led to a training and monitoring protocol termed the “FCS Stewardship program”. The goal is to minimize or eliminate FCS by removing or reducing these risk factors across the industry.
Investigating all suspected cases should identify the areas that need improvement. Although the incidence of FCS may never have been as high in Canada as in the United States (because of our more temperate climate) we may still get very hot days in southern areas of the country in summer. It makes sense to be aware of the potential ramifications of how we sort, process, load, and transport cattle. This is especially true with heavy market weight, black hided cattle on hot summer days.
Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.