Based on this data, more than 16 percent of cattle placed on feed were affected. Other studies have reported that BRD accounts for approximately 75 percent of sickness and 50 to 70 percent of deaths in feeder cattle.

This devastating disease has a huge economic impact due to direct costs associated with the treatment of sick animals. It also leads to reduced weight gains, reduced carcass value and death loss.

Indirect costs are also associated with additional costs for labor, extra space and equipment needed for sick animals. Previously, it has been estimated that the yearly losses for the cattle industry are between $2 billion and $3 billion. Based on one study from 2009, the value of cattle decreased by $23 to $150 per head when compared to healthy animals.

Good management practices, such as vaccination and weaning prior to shipment of calves, are important preventive measures to decrease the risk of disease.

The highest incidence of BRD is seen in calves within the first 30 days placed on feed. New cattle entering the feedyard should be inspected at arrival for signs of disease and treated as soon as possible. In general, calves arriving in the feedyard should be allowed to rest for 24 hours before processing.

They should be provided with clean and readily accessible water for rehydration and fresh, high-quality hay to restore their metabolic system. These measures can help to decrease the stress levels from shipping.

Based on the NAHMS study from 2011, more than 96 percent of feedlot operations observe their cattle at least once a day in the feedlot, and 20.3 percent of feedyards observed animals more than twice a day. Based on a current survey, veterinarians recommended one pen rider per 3,464 high-risk calves and one per 6,405 low-risk calves.

In the same study, 96 percent of the participating veterinarians trained feedlot pen riders to detect diseases in cattle. High-risk calves are animals that have been recently weaned, commingled and purchased through sale barns. These animals are usually not preconditioned. Low-risk calves, on the other hand, are weanlings or weaned preconditioned calves on a sound nutritional program.

Warning signs for BRD

The most important aspect when fighting BRD cases is the early detection of the disease. Early, subtle signs can be easily missed. In North American feedyards, pen riders are checking cattle on a daily basis and are the first line of defense against BRD.

Recommendation for high-risk and newly arrived cattle is to check them twice a day for sickness. Pen riders should be frequently trained to detect sick cattle. This training can either be performed by the attending veterinarian or the feedyard management.

Frequent training sessions are especially important when pen riders have a high turnover rate in a particular feedyard. In general, the pen rider should have their own pens and preferably check at the same time of the day, since observation of the cattle on feed is crucial for the detection of the disease.

Pen riders should not rush through pens. They should take their time in each pen and observe cattle thoroughly; otherwise, subtle changes will be missed.

New and inexperienced pen riders should not be used on high-risk and newly arrived cattle since they may have difficulty detecting early behavioral changes that could be a sign of disease.

One of the early behavior signs of a sick calf is less time spent at the feedbunk. Some animals will separate themselves from the group when sick. These calves also show decreased grooming behavior and carry their heads lower than their healthy penmates. Their eyes are dull, and the ears hang down.

Sick calves like to hide behind other cattle and look away when approached by the pen rider. They are also slower to respond to an environmental stimulus, such as someone approaching the pen or the feed truck driving by.

Since sick calves have a decreased appetite and eat less, they have a decreased rumen fill, which can present as a slab-sided appearance.

Calves with respiratory disease develop an increased respiratory rate. If missed and untreated, it can progress to open-mouth breathing of the animal.

Nasal discharge is common in BRD-affected calves. Often, the discharge is just hanging off the nostrils since the calves stop cleaning their noses when sick.

Any animal that has an abnormal behavior or appearance should be pulled and examined by the pen riders. Early pulls are encouraged to avoid missed cases of BRD.

Treatment in the hospital

Once a calf has been pulled, rectal temperature should be measured to confirm disease, but it should not be used as a sole criterion for the treatment of an animal. When defining fever in feeder cattle, different articles are using different cut-off values. These cut-off values are reported between 103 and 104ºF. The author is using 104ºF as a cut-off for defining fever in feeder cattle.

An indicator that cattle were pulled too late is more than 10 to 15 percent re-treats. In these cases, it is important to retrain pen riders and evaluate protocols for pulling cattle out of the pen.

A study in 2009 has shown that 37 to 83 percent of cattle never treated for BRD had lung lesions at slaughter. This means a visual evaluation of cattle on feed by pen riders might not be sensitive enough to detect all diseased animals.

Currently, multiple research studies are evaluating the use of automatic monitoring systems to detect BRD in feeder cattle, and new technologies might help the industry to improve early detection of BRD.

Earlier detection leads to an improved treatment response and an increased sensitivity, reducing the mortality rate of feeder cattle and therefore lessening the economic impact this disease has on the cattle industry.

References omitted due to space but are available upon request. Click here to email an editor.

• Anita Varga

• Gold Coast Veterinary Service & Consulting
• Email Anita Varga