Agriculture Reference
In-Depth Information
death. There are few vaccination or treatment programs used on swine farms where the
primary purpose is to improve the health of sows.
There are specific times when a sow is at a high risk of infectious disease. Possibly the
greatest risk occurs when the replacement gilt arrives on the farm. The gilt may be exposed
to new pathogens at a time when they are under the stress of transportation and mixing,
and possibly the onset of puberty as well. It is common to purchase replacement gilts
from genetic multiplier herds that have very high health status. If the incoming gilts have
not been exposed to common pathogens such as
Lawsonia intracellularis
before entering
the breeding herd then they may develop acute hemorrhagic diarrhea resulting in a high
mortality rate unless prophylactic antibiotics are used or the gilts are vaccinated prior to
introduction. Likewise, gilts that are reared on a farm free of
Haemophilus parasuis
will
develop acute polyserositis (Glasser's disease) shortly after introduction to a breeding
herd with more conventional health status. Both these bacterial agents are commonly
found on most farms and cause no clinical disease in breeding animals that have been
raised on a farm where these pathogens are endemic.
A second occasion when sows are at greater health risk is around the time of farrowing.
The process of farrowing is physically demanding so that it is a time when the sow is prone
to exhaustion, heart failure, and physical injury. It is also a time when the sows' immunity
is reduced. Systemic infections such as erysipelas (a bacterial disease characterized by
high fever and diamond-shaped skin lesions) are far more likely to occur around the time
of parturition than at any other time. In addition, parturition and early lactation are times
when disease organisms have more opportunity to enter the body, for example through
the birth canal thereby causing uterine infection or metritis, and through injuries in the
teats causing mastitis. Farrowing sows need to be carefully monitored, not only as a means
of preventing stillborn piglets and neonatal mortality but in order to diagnose sows in
the early stages of illness to allow timely intervention and treatment. Often when a sow
develops an illness at the time of parturition treatment with antibiotics and supportive
therapy will save the sow but she may not produce sufficient milk for her young piglets.
Fostering the piglets to other sows is often necessary despite early initiation of treatment
for the sick sow. Some steps to reduce sow illness at farrowing include; maintaining good
parity distribution within the herd (reducing the number of older sows in the herd),
using good hygiene procedures if assistance is required during parturition, vaccination to
prevent diseases such as erysipelas, proper nutrition and feeding management to prevent
obesity during gestation, and control of the environment to prevent heat stress.
18.4
Overview of sow diseases
Diseases of sows are summarized in Table 18.1.
Sudden death is a relatively common occurrence in the sow population. Heart failure
has been reported as one of the main causes of death in sows (D'Allaire
et al.
, 1991; Sanz
et al.
, 2007), but it is a difficult diagnosis to confirm. The heart-weight to body-weight
ratio is one of the smallest among domestic animals and makes sows prone to irreversible
