Lactose Intolerance in Foals

Lactose intolerance in foals is, thankfully, rare and arises from the failure of the intestines to secrete the enzyme lactase to hydrolyse (break down into compounds) lactose in the dam's milk. Not being able to digest lactose - a disaccharide comprised of the monosaccharides glucose and galactose - can result in diarrhea, colic, weight loss, bloating, lethargy, and a general failure to thrive. The undigested and unabsorbed nutrients enter the lower bowel, causing increased bacterial fermentation and retention of water and electrolytes in the intestine. Lactose intolerance may also be caused by bacterial infection or parasitic load in the intestines, specifically Strongyloides westeri (threadworm), Parascaris equorum (large roundworm), and Cryptosporidium (Giardia). Diagnosis can be made based on clinical signs, or more definitively by administering an oral lactose tolerance test to assess whether lactase activity is present or not. (This test requires a lengthy fast, followed by blood samples being taken…

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