Laminitis continues to be a research priority due to its prevalence and severity. Although researchers have identified a number of causes and risk factors, predicting which horses will actually develop this complex hoof disease isn’t always black and white. For example, veterinarians often use the oral glucose test (OGT) to detect insulin dysregulation—a fairly reliable predictor of laminitis—but the connection between laminitis risk, the OGT, and blood glucose and insulin concentrations has remained a gray area.
A group of Australian researchers recently set out to examine the relationship between these three factors, hypothesizing they could incite laminitis in a predictable way and that they could predict the condition’s speed of onset and severity based on insulin glucose response to a high NSC (nonstructural carbohydrate) diet.
The team employed 37 ponies and implemented a diet challenge period (DCP), in which the ponies consumed the following ingredients daily in three equal portions:
- Alfalfa (lucerne) chaff at 5 g/kg of body weight (BW);
- 8 g/kg BW oat flakes;
- 1 g/kg BW liquid molasses diluted in water;
- 1 g/kg BW dextrose; and
- A vitamin/mineral supplement.
The ponies also received 5 g/kg BW of alfalfa hay with their evening meal, bringing the total daily ration to 2.7% of BW. The team continued the DCP for 18 days or until the ponies developed laminitis.
The researchers examined ponies daily and, at the first sign of lameness, initiated treatment. Fourteen ponies developed laminitis during the DCP.
“Laminitis was diagnosed by video analysis performed by (Chris Pollitt, BVSc, PhD, head of the Australian Equine Laminitis Research Unit at the University of Queensland, and Donald M. Walsh, DVM, founder and president of the Animal Health Foundation, in Missouri) who are international experts in the field,” relayed researcher Martin Sillence, PhD, professor of biological sciences at Queensland University of Technology.
The team identified a clear relationship between glucose and insulin concentrations measured during the OGT and DCP and laminitis risk and onset speed. However, Sillence said they were surprised to find that 10 ponies with very high insulin levels did not develop clinical laminitis.
“We believe subclinical laminitis may occur in ponies with high insulin levels without overt signs of laminitis,” relayed Alexandra Meier, DVM, lead researcher and PhD candidate at Queensland University of Technology. “This could mean hoof damage is occurring without owners knowing it.”
The team recommends owners have their veterinarian perform an OGT on any horse or pony showing signs of insulin dysregulation (i.e., general obesity, cresty neck, body fat deposits, or abnormal hoof growth rings) and radiograph the feet to look for evidence of subclinical laminitis.
The study, “The oral glucose test predicts laminitis risk in ponies fed a diet high in nonstructural carbohydrates,” was published in Domestic Animal Endocriniology.