disease Prevention
Paul M. Pitcher, DVM, and
Thomas D. Parsons, DVM,
New Bolton Center,
School of Veterinary Medicine, University of Pennsylvania
Traditional veterinary interventions for the treatment or
control of infectious disease usually include antibiotic
therapy or vaccination. A progressive definition of disease
recognizes management, facilities, genetics, and nutrition,
as well as infectious agents, as important potential causes of
health problems. The emergence of severe diseases affecting
newborn pigs such as Porcine Reproductive and Respira
tory Syndrome (PRRS) has required re-evaluation of man
agement practices in order to minimize losses.
Crossfostering is often considered an important farrow
ing house management practice to reduce preweaning mor
tality in young pigs. In many of the herds that we visit,
extensive crossfostering policies are common. Piglets are in
itially sorted and then disadvantaged animals are moved
regularly during lactation in an attempt to maintain size
uniformity within a litter. Herds with the majority of litters
disrupted are common.
When successfully implemented, the result of crossfoster
ing is to improve fostered pigs’ access to their source of nu
trition-milk. The goal is to balance nutritional needs of the
piglets with that provided by the sow. This goal cannot be
achieved without observations on the fostered pig’s current
source of nutrition and its projected source (the sow it will
be moved to). Therefore, an important part of our recom
mendations on crossfostering policy is to determine each
lactating sow’s capacity by counting functional glands.
This is easy to do at farrowing by simply palpating each
gland for fullness and suppleness. Pigs required to nurse
smaller or hardened glands will not thrive. This will be evi
denced in litter weaning weights. Litter weaning weights are
one of the best ways to assess sow productivity, and if labor
can be supplied to gather the data are extremely useful in
making culling decisions that serve to increase the average
productivity of lactating sows. It is our opinion that failure
to assess each lactating sow’s productivity (either by exam
ining udders or by measuring litter weaning weights) is a big
reason for excessive crossfostering as managers scramble to
find every nursing pig a place at the table.
It is sound advice to completely avoid crossfostering
beyond the first day of age, especially when greater control
over disease incidence rate is desired. Several biological and
behavioral factors tend to be compromised if crossfostering
is practiced beyond the first 24 hours post-farrowing. At
birth, piglets receive passive immunity in the colostrum
against the largest source of pathogens in their environ
ment-the dam.
Unless all lactating sows have identical disease and vac
cine exposure histories, there is likely to be a mismatch be-
Piglet Management And PRRS
tween immunity provided in colostrum and disease
exposure in newborn pigs that have been fostered to a sow
other than their mother. Furthermore, recent work indicates
that, with PRRS, pigs can be bom with the infection.
Often, these pigs are the smaller, weaker pigs and are
more susceptible to secondary bacterial infections. If the
crossfostering policy is to move disadvantaged pigs to give
them a better chance at survival, a bad situation (pigs born
with PRRS or carrying secondary bacterial infections) is
made worse as crossfostered, diseased pigs are given the op
portunity to spread the infection to previously healthy
litters. Of course, the opposite scenario is also
possible-healthy crossfostered pigs are placed in an infected
litter-as glands are vacated by pigs that have succumbed to
disease.
Social hierarchy within the litter is also formed at birth.
Disruption of litters late in lactation can reduce pig growth
rates and causes behavioral problems in fostered pigs, resi
dent pigs, and the sow. Fostered pigs have increased ambu
lation, vocalization, and an increased reluctance to engage
in suckling. These pigs may also exhibit a withdrawal syn
drome. Such disruption of the litter causes more pig-to-pig
aggression even between resident pigs, and sows also exhibit
aggression toward foster pigs, especially older pigs. Also, as
age at fostering increases, the behavioral abnormalities in
crease and extend the time required for fostered pigs to in
tegrate into their new environment. Abnormal behavior can
be greater in litters with animals of equal status compared to
litters that contain a mix of dominant and submissive pigs.
Therefore, we do not recommend that piglet size be used as
an important criterion in crossfostering decisions.
So-called Mcßebel (management changes to reduce expo
sure to bacteria to eliminate losses) attempts to minimize
the spread of the PRRS virus and maximize the piglet’s pro
tection afforded by its maternally derived immunity. Ac
cordingly, one of the tenets of Mcßebel is to minimize or
even eliminate crossfostering after the first 24 hours of life.
We have developed tools to measure the effectiveness of
crossfostering and to monitor crossfostering policy. These
computer-based tools are driven by observations collected in
the farrowing house. We welcome the opportunity to work
with swine producers seeking to improve the performance
of their herds.
References: Fraser, DK. Behavior and misbehavior in the
lactating sow and litter. In Proceedings, American Associa
tion of Swine Practitioners 26th annual meeting, seminar
session 10,1995; McCaw, MB. Effect of reducing crossfost
ering at birth on piglet mortality and performance during
an acute outbreak of porcine reproductive and respiratory
syndrome. Swine Health Prod. 2000;8:15-21; Price, EA,
Huston, GD, Price, MI, Borgwardt R. Fostering in swine as
affected by age of offspring. J. Anim. Sci. 1994;72:1697-
1701.