Glycaemic and insulinaemic responses to feeding hay with different non‐structural carbohydrate content in control and polysaccharide storage myopathy‐affected horses

Abstract

The aim of this study was to determine whether the glycaemic/insulinaemic responses to hay with non-structural carbohydrate (NSC, soluble carbohydrate) of 17% (HC), 10% (MC) or 4% (LC) differs in control horses and whether these responses differ between control and horses with polysaccharide storage myopathy (PSSM). Five clinically normal control horses and seven PSSM horses, all unfit and of Quarter Horse breeding (age 9.4 ± 3.4 years, body condition score range: 4.5-6). A crossover design compared the HC and LC hay, with horses randomly assigned to hay type for 5 days, and all horses fed the MC hay during washout, after which the diets were switched. Horses were fed 1.5% BW (as fed) divided into 2 feeding per day, no grain. On morning of the fifth day of each block (seventh day for washout), horses were given 0.5% BW in hay, blood was drawn before and every 30 min for 5 h after feeding, and the rate of intake was measured. Whole blood glucose and plasma insulin were measured. The intake rate was significantly higher for HC. In control horses, the insulin area under the curve (6891.7 ± 3524.2 HC vs. 1185.4 ± 530.2 LC) was significantly higher than LC. Polysaccharide storage myopathy horses had significantly higher glycaemic and insulinaemic responses to HC vs. LC, however; the magnitude of insulin response was lower and glucose response higher in PSSM vs. control horses. Results suggest that insulin responses can differ significantly with the NSC content of hay. Feeding hay with 17% NSC produces elevations in insulin that could be detrimental for PSSM horses.

Effect of period, water temperature and agitation on loss of water‐soluble carbohydrates and protein from grass hay: implications for equine feeding management

“…The WSC in grasses largely comprise simple sugars, (glucose, fructose and sucrose) and fructans (poly and oligo-sucrosyl fructose). As fructose reduces insulin sensitivity in IR mares (Geor and others 2009), inulin-type fructans can induce laminitis (Pollitt and others 2003), and PSSM is associated with abnormal muscle glycogen accumulation (Annandale and others 2004); feeding hay high in WSC may be detrimental to animals suffering from these conditions (Genrick and others 2008, Borgia and others 2011). …”

Effects of fat supplementation on plasma glucose, insulin and fatty acid analysis in ponies maintained on a forage‐based diet

“…Similarly, Borgia et al. () reported an elevation in insulin levels in polysaccharide storage myopathy horses that were fed high non‐structural carbohydrate hay.…”

Polysaccharide storage myopathy – the story so far

“…Horses should continue to receive 1–2% of their body weight as forage, ideally with a low (<12%) NSC content (Borgia et al . ) and in some cases, depending on workload and energy requirements, further caloric supplementation may not be required. Grazing may need to be restricted at certain times of the year when the NSC content of grass is particularly high.…”