Page 756 - Veterinary Immunology, 10th Edition

generally remain healthy and do not require treatment. About 75%
VetBooks.ir of foals with IgG levels between 200 and 400 mg/dL will also

remain healthy. However, they should be watched and treated with
antibiotics at the first signs of bacterial infection. Any foals with

total failure of passive transfer or foals younger than 3 weeks with
partial failure of passive transfer should be treated. Foals with
plasma IgG concentrations less than 200 mg/dL, foals that have not
nursed within 6 hours of birth, and foals that have received

colostrum with IgG of less than 1000 mg/dL (specific gravity less
than 1.050) should receive additional colostrum. Two to three liters
of good-quality colostrum (IgG of more than 7000 mg/dL) should be
given by bottle or nasogastric tube in three or four doses at hourly

intervals. The colostrum must be free of antibodies to the foal's
erythrocytes (Chapter 31). Colostrum may be obtained from mares
that have more than is needed for their own young. It can be stored
frozen at -15° to -20° C for up to 1 year. If stored colostrum is

unavailable, fresh colostrum from primiparous mares can be used.
If colostrum is not available, serum or plasma may be administered
orally. A large volume (up to 9 L) may be required since serum IgG
is rapidly catabolized so that within 12 hours its concentration is

much less than that found in colostrum-fed foals. The reasons for
this are unknown.
In foals that are older than 15 hours, oral absorption ceases and
intravenous plasma infusion must be given. Ideally the dose used

can be calculated to attain an IgG level of at least 400 mg/dL. Frozen
horse plasma is available commercially, although this may not
contain antibodies against local pathogens. Alternatively, the
plasma may be obtained from local donors. Blood should be

collected aseptically with heparin or sodium citrate. The plasma is
collected after the erythrocytes settle and is stored frozen until
used. The plasma must be prechecked for antierythrocyte
antibodies and must be free of bacterial contamination. The

transfusion should be given slowly while the foal is monitored for
untoward reactions. All foals receiving supplemental colostrum or
plasma should have their IgG levels rechecked 12 to 24 hours later.
Considerations similar to those described previously apply to
failure of passive transfer in the calf. Calves with serum IgG of less

than 1000 mg/dL at 24 to 48 hours of age have mortality rates more

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