Better Pork - August 2016

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recover from the acute disease often
abort 2–3 days later.”
Other toxic causes
Cresol sprays (used for mange and
louse control) can cause abortions
and stillbirths. Other toxic causes in-
clude dicumarol and nitrates. “Nutri-
tional causes of reproductive failure
are not well defined,” according to
the Manual. “Vitamin A deficiency
can cause congenital anomalies
and possibly abortions. Riboflavin
deficiency can cause early premature
births (14–16 days), and calcium,
iron, manganese, and iodine defi-
ciencies have been associated with
stillbirths and weakborn pigs.”
Propane heaters and carbon monoxide
poisoning
Propane heaters are commonly used
to heat farrowing rooms and gesta-
tion barns in winter. Propane heaters
exhaust carbon monoxide as a by-
product of generating heat. Carbon
monoxide converts hemoglobin in
mammals to carboxyhemoglobin.
Hemoglobin is the carrier of oxygen
which is transported in blood to all
tissues and cells throughout the body.
Carboxyhemoglobin does not have
the oxygen-carrying capability of
hemoglobin, hence when present, de-
prives the body of life-dependent ox-
ygen. Fetuses are highly sensitive to
carbon monoxide intoxication, much
more so than newborns and mature
mammals, including pigs. Ventila-
tion in winter is reduced in barns
to conserve heat and reduce energy
costs. Carbon monoxide toxicity
due to faulty propane heaters and/
or poorly ventilated rooms has been
associated with increased numbers of
abortions, stillbirths and weakborn
pigs which usually die soon after
birth. Fetal tissues are cherry red, a
sign of carboxyhemoglobin and car-
bon monoxide intoxication. Sows are
not usually clinically affected unless
carbon monoxide reaches very high
levels. Pregnant women working in
areas with propane heaters may also
abort, creating a public health safety
concern.
Summary
Prior to PRRS virus, we did not have
a confirmed diagnosis for the vast
majority of abortions in swine. Most
abortions prior to PRRS were from
non-infectious causes rather than by
any infection (viruses, bacteria, etc.).
The non-infectious causes of repro-
ductive failure are scattered among
a handful of known events. These
include low numbers of fetuses in a
pregnancy, high ambient tempera-
ture, autumn abortion syndrome that
is probably linked to low progester-
one levels in pregnant sows during
late summer and fall, carbon monox-
ide poisoning from propane heater
exhausts to heat barns in winter,
mycotoxins (zearalenone, zearalenol
and fumonisin), and possible vitamin
deficiencies (vitamin A and B2 [ribo-
flavin]). BP
S. Ernest Sanford, DVM, Dip Path, Diplomate
ACVP, is a swine veterinary consultant in London,
Ontario.
HERD HEALTH