Assessment of Nutritional Status
Although the healthy adult horse or ruminant with an adequate body condition score (see Chapter 9) and minor injury or illness rarely requires nutritional supplementation, early nutritional support should be strongly considered in patients with increased metabolic demands, such as young growing animals or lactating dams, individuals presenting with a prior history of malnutrition or hypophagia, patients with underlying metabolic abnormalities that could worsen with feed deprivation, and individuals with an illness such as severe trauma, sepsis, or strangulating bowel obstructions that may result in an increased metabolism and excess losses (e.g., albumin loss through a compromised gastrointestinal tract).
Underweight horses with a BCS less than 3.5 out of 9 (though this depends on the breed and individual characteristics) should ideally receive nutritional support early in the disease process rather than waiting to see if the individual will begin to eat on his or her own volition. Obese or overconditioned individuals, particularly pony breeds, miniature horses, donkeys, and camelids, as well as lactating mares, are at risk for developing hyperlipemia and should receive nutritional support, especially if their serum triglycerides are above normal reference values. Lactating dairy cattle or pregnant sheep or goats should also receive early nutritional support to minimize the risk of developing ketosis, fatty liver, or pregnancy toxemia. Patients with pituitary pars intermedia dysfunction (formerly known as equine Cushing's disease) or equine metabolic syndrome are insulin resistant and may also be at greater risk for developing hyperlipemia and fatty infiltration of their liver. Depending on the severity and type of underlying disease process and individual characteristics (breed, body condition), some animals may develop severe hyperlipemia (triglycerides > 500 mg/dL) or ketosis within days of onset of anorexia. The combination of illness and metabolic effects of hyperlipemia or ketosis can worsen the individual's inappetence, creating a vicious cycle. Consequently, if feed deprivation is prolonged (in some cases as little as 1 to 2 days of anorexia can result in moderate to severe hyperlipemia) or there is a concern regarding the individual's desire or ability to eat, early intervention is indicated to prevent more severe metabolic complications.A list of BCS descriptions for different species is provided in Chapter 9. Changes in weight or BCS are often easily overlooked on day-to-day observations of the patient if a concerted effort is not made at detecting them. Palpation of the animal (ribs, dorsal vertebral processes) is necessary in sheep with a heavy fleece, camelids with long fiber, and horses with a thick winter hair coat.