Understand
and Recognize Hidden Commingling
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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.
