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Congratulations, your cria has arrived!
After all the planning and waiting,
the bundle of joy is now here in all
its wobbly, long-legged glory. Soon
your veterinarian will arrive for your
cria’s first health check and will likely
have its blood sampled to test its IgG.
Here are some answers to commonly-
asked questions about IgG.
Due to the specific type of placenta
an alpaca has, no immunity is trans-
ferred from mother to cria during
gestation. This means when the cria
is born, it has virtually no immune
system. In order to gain a short-term
immune boost to protect the cria
while it is developing its own immune
system, the cria “borrows” antibodies
from its dam in the form of colostrum,
or her first milk. These antibodies are
a type of immunoglobulin, specifically
immunoglobulin G, or IgG.
For the first twenty-four hours
of life, a cria is able to absorb IgG
through its gut. After this period,
the cria’s digestive system does not
allow absorption of such large particles
as IgG and absorption of antibodies
in this way is ended. This is called
“gut closure” and occurs in all species
in which colostrum is a vital route for
antibody transfer. This gut closure is
in part a safety mechanism, preventing
other large particles such as bacteria
from entering the blood stream in the
same manner as IgG does. This is also
why it is important to ensure a cria
nurses soon after birth.
After the first few weeks of life, a
cria’s IgG level will start to decrease.
This is normal and represents the
slow destruction of these borrowed
antibodies. After a few months, how-
ever, IgG levels increase again. This
indicates the time when a cria’s own
immune system is starting to develop
and produce antibodies of its own.
Testing a cria’s IgG at twenty-four
hours of age measures the amount of
antibody the cria has consumed. This
is measured most importantly on sick
or weak crias, as well as those born to
maiden mothers. Some farms forego
measuring IgGs in healthy, strong crias
born to proven dams. There currently
is no way to test IgG content in a dam’s
colostrum so the cria IgG test acts as
an indirect exam of the quality of the
dam’s colostrum, an important thing
to document in a maiden mother.
An IgG test is simple to perform.
It only requires a small blood sample
taken from the cria by your veterinarian.
Your vet will then run the sample on
a specific laboratory machine that will
produce an objective measurement of
the amount of IgG present in the cria.
This measurement is a number in
milligrams per deciliter (mg/dL) and
can be roughly anywhere from under
100 to over 1500. IgG testing kits are
available for purchase directly from the
manufacturer and some farms choose to
run their own IgG samples themselves.
Once given your cria’s IgG measure-
ment, how then do you interpret it? Any
number over 800 mg/dL represents a
successful transfer of passive immunity,
meaning your cria has ingested enough
high quality colostrum to provide him
with antibodies to help his body fight
infection. Some owners and veterinarians
prefer to see numbers above 1000 mg/dL.
In a healthy cria with a good suckle with
a dam that produces high quality
colostrum (meaning high IgG), this
passive transfer of immunity is usually
all it takes for a cria to maintain a strong
immune system while growing up.
IgG values between 400 and 800
mg/dL indicate what is called partial
failure of passive transfer, meaning that
the cria does not have as many anti-
bodies as it should, but still has some
immune function. Values below 400
mg/dL indicate true failure of passive
transfer, or FPT. These crias do not
have the appropriate amount of IgG
to adequately fight infection and as a
result are immunocompromised.
What does it mean to have a cria
with FPT? Crias such as these are
normally weaker and do not grow as
well as their counterparts with higher
IgGs. More importantly, these crias
are much more susceptible to life-
threatening infections such as infected
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Alpacas
Magazine
Your Cria’s
Ig
G
by Anna O’Brien, DVM