SERUM CHEMISTRY PROFILE
LAYERS: Wilson. “I usually become more concerned if a horse has a low white cell count than if it’s high, because a low count usually means the horse is very sick at the time you are taking the blood sample.”
Finally, a CBC will show the platelet count, the total volume of the cells that are instrumental in forming clots and stimulating healing after injury. More specific tests---mean platelet volume (MPV) and platelet distribution width (PDW)---record the average sizes of the platelets. A low platelet count, which can be caused by certain drugs or toxins, may leave the horse at risk of uncontrolled bleeding. Platelet counts usually return to normal soon after the drug is discontinued. Abnormally high platelet counts are rare in horses.
Focusing on the clear, yellowish liquid left after all the solid blood cells are removed by clotting and then centrifuging, the serum chemistry profiling can identify levels of various proteins and enzymes, electrolytes and other biochemicals that indicate overall health as well as individual organ function.
“Results of the serum chemistry help me evaluate systems such as the liver, kidneys or muscles,” says Marsh. “It helps us know if the body is in good health or if there is something abnormal going on that needs further exploration.” Some of the major values a veterinarian may look for include:
• Proteins. The tests measure levels of the proteins albumin and globulin. “It is important to check protein levels because protein in the blood is responsible for keeping fluid inside the blood vessels and not leaking out into body tissues,” says Wilson. “Usually the horse loses protein from the blood through severe diarrhea. Horses can also lose it through the kidneys if the kidneys are not functioning properly.”
Low protein levels may also signal a liver problem. “The protein is produced in the liver, so if the protein is low this might mean the horse has a liver problem---if there are other things on the profile that are consistent with liver damage,” says Wilson.
The albumin/globulin ratio can also help to distinguish health issues that will affect both together, such as dehydration, from illnesses that will affect one more than the other.
Another important protein is fibrinogen, which aids the formation of blood clots. “Fibrinogen is an acute-phase protein generated by the equine liver that can indicate an inflammatory