Page 62 - NM Winter 2023

NEONATAL MECONIUM IMPACTION
The indication that a foal needs to defecate is familiar if you have spent time around newborn foals-hunched back, wagging tail, and straining to pass manure.
ISOERYTHROLYSIS (NI)
NI is a potentially fatal disease of
foals that causes rupture/destruction (hemolysis) of their red blood cells within the vessels that occurs because of blood
type incompatibility between the mare and foal. This incompatibility occurs when
the foal inherits its blood type from the stallion, and that blood type is different from that of the mare. The mare develops antibodies against the foal’s blood type when she has previously been exposed
to this foreign blood type from either a previous foaling, blood products, or even microcapillary rupture of the foal during the same pregnancy. All of these factors cause the mare to produce antibodies within the colostrum against the foal’s red blood cells. As we know, the colostrum of the mare contains all the necessary antibodies the
foal needs to create its immune system but in an NI situation, when the foal nurses
the colostrum, the antibodies within the colostrum attack the red blood cells of the foal. NI foals are born normal, but become depressed, weak, anemic, and have yellow mucus membranes (icterus) within 12-72 hours of life. Presumptive diagnosis can be made in any foal younger than 4 days with lethargy and icterus. Definitive diagnosis is based on finding alloantibodies in the serum or colostrum of the mare that are directed
at the foal’s red blood cells coupled with anemia in the foal. A stall-side test can be performed by mixing 1cc of sterile saline with 1 drop of foal blood and then adding 1 drop of colostrum from the mare; if a pellet forms, you know you have a problem.
Treatment depends on the age of the foal at diagnosis and the severity of the clinical symptoms and is aimed at reducing damage to the kidneys with supportive care and IV fluids. Prognosis directly correlates with the quantity and activity of absorbed antibodies and also indirectly correlates to the rate of onset of signs. If a foal becomes sick quickly, they can often die before a diagnosis is made, while slowly progressive symptoms generally allow appropriate supportive
care to be implemented and increases the prognosis. From a management standpoint, any mare who has produced an NI foal in the past is in danger of producing another in the future. Any future foals out of the mare should be provided colostrum from a banked source unless the stallion and mare have been blood typed and there is known blood group compatibility.
Meconium impactions are a common
cause of acute abdominal pain in neonates. Meconium is the dark, tarry, hard first manure produced by a foal. The indication that a foal needs to defecate is familiar if you have spent time around newborn foals-hunched back, wagging tail, and straining to pass manure. Most foals will pass meconium after their
first meal, but the flip side of that is that
most foals will not nurse well until they have defecated. Occasionally, foals will defecate but continue to act uncomfortable, and if a true meconium impaction is present, abdominal pain symptoms will persist and increase as
gas accumulates behind the impaction. These foals will often display the common foal colic behavior of the “cockroach” position; rolled
up on their backs with all 4 legs up in the air. Typically, a warm, soapy water gravity flow enema does the trick to relieve the meconium impaction. The common practice of using store-bought Fleet enemas is cautioned
against as they can cause rectal irritation and increased phosphate levels. In extreme cases a retention enema may be necessary to relieve the impaction and surgery could be required in the most dire cases. Pain management
in these foals should be approached with caution as non-steroidal anti-inflammatories have a more severe effect on the kidneys
and gastrointestinal mucosa of a foal than
in adult horses. The biggest area of concern surrounding meconium impactions ends up being the potential for sepsis secondary to FPT from insufficient colostrum consumption or from bacterial translocation across disrupted mucosal barriers of the GI tract.
There are a myriad of disease processes and illnesses that can affect the equine neonate in the early hours and days of life. While none
of these conditions are 100% preventable, most are successfully treatable if dealt with promptly and thoroughly. As I remind my clients during this time of year, it is much more cost effective to be proactive rather than reactive when it comes to a foal. These babies are an investment of money and time, and there is nothing more heartbreaking than to get through a delivery smoothly only to have the foal die from a preventable situation.
Early intervention is the key, especially in the instances where the foal appears completely normal but has trouble lurking on the horizon. This is why it is important to have a veterinary exam performed in the first 12-24 hours of life (or sooner if the foal is painful or not nursing well), to try to identify these potentially hidden causes of future illness.
© Dr. Julie Carroll, Oak Valley Veterinarian Services © Megan Petty
Foals with meconium impactions will often display the common foal colic behavior of the “cockroach”.
60 New Mexico Horse Breeder