Texas Equine Veterinary Association

www.texasequineva.com • 9 Deciph ing Neonate's Bl dwork: What is and what is not normal variation Rudy Madrigal, DVM, DACVIM graduated from Texas A&M University College of Veterinary Medicine in 2013. He then completed an equine internship at Louisiana State University School of Veterinary Medicine followed by a large animal internal medicine residency at Texas A&M University from 2014–2017. He became a diplomate of the American College of Veterinary Internal Medicine-Large Animal in 2018. He has practiced in Texas and California with focus on ultrasound, neonatal medicine, and endocrinopathies. He is currently at Equine Sports Medicine & Surgery (ESMS) in Weatherford, Texas. Spring season is around the corner and with it an increase in the number of newborn foals. Serum chemistry and complete blood count (CBC) machines are invaluable for diagnosis and treatment of adult horses due to appropriate reference ranges (RR), but what about our neonatal patients? ese RR do not always directly translate for this unique population. Understanding neonatal physiology and having appropriate RR are needed to help diagnose and appropriately treat foals. COMPLETE BLOOD COUNT (CBC) At birth, a foal's hematocrit (HCT) and red blood cell (RBC) indices are similar to adult horses, with a decrease occurring within the first week of life. is decrease is due to normal physiological changes including increased destruction of fetal RBCs, increased plasma protein with subsequent fluid shi from the tissues, increased oxygenation due to lung function, and low iron levels in mare's milk. is decrease is not cause for concern unless the HCT goes below 20%. In dra foals, this drop in HCT is not as dramatic as compared to light breed foals; donkey foals will have similar HCT drops as light breed foals and this is presumed to be similar in mule foals. Foals will have similar white blood cell (WBC) counts to adult horses, although high/ high-normal neutrophils and low lymphocytes are common secondary to cortisol release, with a neutrophil:lymphocyte ratio cover of 2.5. Premature or dysmature foals at birth may have low normal neutrophil count or neutropenia due to decreased cortisol production and will have decreased neutrophil:lymphocyte ratios as compared to normal foals. Neutrophilia can occur at birth in high-risk foals (such as those born to mares with placentitis) and will increase in the first 24 to 48 hours due to sepsis. Septic foals may also present with neutropenia. Neutrophilia and neutropenia may not be present at early sepsis so normal counts do not rule this condition out in neonates. In sepsis, neutropenia is most commonly seen early in disease followed by neutrophilia. Acute phase proteins (APP) may help identify foals in early sepsis without changes in WBC count. Fibrinogen and serum amyloid A (SAA) are the most commonly evaluated APPs in horses and foals. At birth, fibrinogen is lower in newborns as compared to adults. Hyperfibrinogenemia noted within the first day or two of life is most likely an indication of in-utero inflammation/infection, as increased fibrinogen production occurs 24 to 48 hours following infection/inflammation. Serum amyloid A (SAA) is also an acute phase protein with a short half-life with increased SAA (>100mg/L) being indicative of infection/inflammation. Mild increases can be seen transiently post- foaling or may indicate an impending or resolving infection. By Rudy Madrigal, DVM, DACVIM

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