The number of cattle deaths in American feedlots increased by 69 percent from 1994 to 2003.
Respiratory disease losses were of particular concern, going up by 119 percent in all cattle on feed.
Despite our ability to report these changes, it is still difficult to determine normal death loss in feedlots.
A study that looked at individual pen death loss in feedlots found that 35 percent of pens had no death loss, 18.8 percent had two percent or more, and 0.6 percent accounted for more than 10 percent of death loss.
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This means that 90 percent of the death loss is generated in less than 10 percent of the pens.
It seems that animal weight is a strong predictor of mortality. The death loss of cattle entering the feedlot between 700 and 899 pounds hasn’t really changed, but death losses in the 400 to 599 lb. group rose significantly.
As a result, the rise in feeder deaths can be explained by an increase in the number of younger, lighter weight cattle that have less mature immune systems and spend more time in feedlots.
Sex status also affects illness. Bull calves castrated after they arrive have 140 percent more morbidity than cattle that arrive as steers. Pregnancy also creates more death loss.
A common theme plays out each fall in feedlots: most death loss does not occur until the cattle have been on feed for an average of 60 days.
The season begins when the fall cattle arrive. For the first month, sick cattle are treated, but losses are minimal. The operator thinks disease is under control and orders a new batch of cattle.
When the first group has had 60 days on feed, they start to die. The new arrivals are also high risk and they contribute to losses for another 60 to 90 days.
However, death loss rates tell only part of the story.
Consider a feedlot that is suffering a death loss of five percent this year, even though it has traditionally been only one percent. The knee-jerk reaction of the managers is to change veterinarians, the drugs they use to treat cattle, or both.
However, if you look deeper into the situation, you may find that while normal pull rates hover about 10 percent, this year they peaked at 50 percent. More animals are becoming ill, but the fatality rate for both years is 10 percent. It hasn’t changed.
The drugs are working just as well as they did last year and the boost in death loss isn’t caused by the failure of treatment.
It’s because something else changed, such as the source of cattle, weather, feeding, cattle supervision or previous and current body condition.
The burning question for many producers is why does illness occur? A lot of it has to do with the diseases cattle bring to the feedlot.
Bovine viral diarrhea is a significant, invisible contributor. One calf persistently infected with BVD increases respiratory disease in the pen by 43 percent. It also causes more pulls in adjacent pens.
The other contributor is a lack of feedlot staffing.
It is difficult to find people who are willing and able to work with cattle.
Feedlot operators can reverse the trend in higher mortalities by changing how they buy and sell cattle. They can also try to source cattle free of disease and boost the number of employees in the feedlot.
Jeff Grognet is a veterinarian practising in Qualicum Beach, B.C.
