Understand and Recognize Hidden Commingling
by Robin Falkner, DVM
Most of us experienced with feeder cattle recognize that a history of recent commingling is associated with increased risk for post-arrival Bovine Respiratory Disease Complex (BRDC). Given this association, many cattlemen give considerable weight to “commingling status” when determining the price, health expectations, and post-arrival management of a given set of cattle. Since many of the diseases associated with BRDC can not be eliminated or excluded from an operation, we should develop a strategy to better manage those diseases likely to be present—-our BRDC “Biocontainment” Strategy. Understanding and managing commingling is critical to BRDC Biocontainment.
However, many times cattle are received from a single source with what appear to be good histories and good health programs, but they still have significant health problems in the immediate post-arrival period. Extensive investigations into “groups that broke that shouldn’t have” often reveal what I call “hidden commingling” to be a consistent contributing factor.
Exactly what is this concept? First, we need to understand the dynamics of commingling. Diseases stabilize in populations after a period of time. This occurs as each animal in a population (group) is exposed to the diseases present in the group and acquires active immunity to them. After stability occurs in the group, some animals may be carriers and others may suffer performance degradation due to exposure, but for the most part we don’t expect to see a lot of clinical disease, and a significant, well-defined break of stabilized diseases in a group would not be expected.
For most of our BRDC diseases, which are rapidly transmittable from animal to animal, we would expect relative stability 30-60 days after the last introduction of a “new” disease. However, even though a stabilized group is “straightened out,” we can break that disease stability by commingling—adding new animals to the group, mixing “straightened out” groups, exposure to sick cattle, etc. —anything to add new disease(s).
Since the vaccines available for BRDC pathogens are not always 100 percent efficacious in preventing early clinical signs, and vaccines for some pathogens are not available, no health program can completely eliminate post-commingling BRDC. Research and experience have shown that solid health programs will decrease both the incidence and severity of BRDC when commingling is necessary, with the greatest benefit often being seen in the response of animals to treatment. However, the fact that some animals develop early clinical signs and require treatment in the arrival period is a source of considerable disappointment for the purchaser of groups considered “low risk” for BRDC.
If one is to maximize the ability to predict BRDC in the immediate post-arrival period, understanding and recognizing whether commingling is occurring (and the degree of it) is a critical tool. In addition, since many times this commingling is not necessary, it can often be eliminated or managed more effectively. Investigations of field outbreaks reveal these common “hidden commingling” scenarios:
Cow calf operations
- Those operations that maintain multiple, separate herds. When calves from these separate herds are mixed to create uniform lots, it often has the same consequences as combining the cattle of as many separate owners as the operation has herds. Since progressive operations often group cows by age, etc to improve management, this problem is often seen in the better managed herds in addition to herds kept separate because of divided acreage.
- Large herds with very low stocking densities: if cattle are dispersed widely enough, “good” disease exposure from animal to animal in a herd may not occur prior to weaning, resulting in a population where the diseases present are not stabilized.
- It should be noted that the lack of disease stability between the separate herds within an operation can cause considerable health problems when cows and/or calves are regrouped for other reasons.
Backgrounded Cattle/Yearlings
- Mixing of separately backgrounded groups to create load lots •Addition of cattle held separately, such as in a hospital or recovery pen, to a group just prior to shipment. •Special feeder calf sales: Often uniform, load-sized lots are sold that have been backgrounded/preconditioned in separate locations—with commingling occurring day-of-sale. These cattle have higher BRDC risk that those managed as a single group.
Other
- Handling of cattle during marketing/transportation: Disease exposure may occur when groups are marketed through facilities with other cattle and/or are exposed to other cattle in shipping facilities.
- Groups with a significant number of animals breaking very early in the post-arrival period often have “hidden commingling” that occurred several days prior to shipment, such as calves from separately managed herds that are commingled and “short weaned” for a week or two prior to shipment.
- Commingling actually occurs after arrival: Adding newly arrived cattle to existing animals in the immediate post-arrival period is risky, regardless of their health program. Likewise, fenceline contact with other recently arrived cattle (that still may be shedding significant numbers of pathogens), or even worse, hospital or recovery pen contact/circulation, should be avoided if possible.
Managing purchased cattle to minimize disease exposure (and loss of group disease stability) in the weeks immediately prior to shipment and following arrival can pay huge dividends in BRDC management, and is a critical part of a BRDC Biocontainment Strategy. Such a strategy allows health and management programs to exert their full benefit, plus takes advantage of any natural disease stability present at purchase or occurring after arrival. Compromises that result in new disease exposure during this period will result in disappointments with the best cattle, programs, and products.
Dr. Falkner is a stocker consultant and technical services veterinarian for Pfizer Animal Health. He can be reached at 615 849 3642.
easy-to-read articles designed to increase overall awareness among the feedlot community.