Grass length can affect muzzled grazing behaviour in ponies

Grazing muzzles can be an effective tool to help with equine weight management, according to new research, but longer grass can be more difficult for muzzled ponies to graze. This can cause frustration-related behaviour in some individuals.

Grazing muzzles have been shown to reduce the pasture intake of ponies by around 80% by significantly reducing bite size and intake. Ponies fitted with the muzzles may spend more time engaging in foraging and eating than their non-muzzled counterparts, yet the majority either lose weight or retain their body condition. This in turn helps reduce susceptibility to obesity and related disorders, such as insulin dysregulation and laminitis.

The new research was conducted by the WALTHAM® Equine Studies Group in collaboration with Dr Annette Longland of Equine Livestock and Nutrition Services in Wales. Four mature ponies were selected for the study. Their dry matter (DM) and water-soluble carbohydrate (WSC) intakes were measured in spring, summer, and autumn pastures on four, three-hour occasions per pony per season when fitted with or without a grazing muzzle. In addition ponies, with and without muzzles, were allowed to take 10 bites of swards maintained at different heights.

When wearing grazing muzzles pasture intake was reduced by 77% during spring and summer and by 83% during the autumn. Without muzzles the ponies generally reduced the sward length by half with the first bite but when muzzled the reduction was variable and the ponies appeared to experience greater difficulty in accessing the longer versus the shorter swards.

The short (less than 10cm), upright, grass appeared to be the easiest to eat, as leaf blades and stems protruded through the holes in the muzzle. The medium and long swards proved more difficult. They bent under the pressure of the muzzle and became flattened, causing the ponies to adopt various strategies to access the grass. In some cases they pawed the ground to unearth the sward and access it through the muzzle. Alternatively they rammed the solid base of the muzzle hard onto the grass, causing it to buckle and make some blades or stems accessible. These were then yanked vigorously often causing the entire plant to be uprooted and eaten.
“While the frustration displayed when the muzzled ponies were on longer grass swards indicates that care should be taken to provide an accessible grass length, grazing muzzles remain an effective weight management tool,” said Clare Barfoot, research and development manager at SPILLERS®, one of the partners in the WALTHAM® Equine Studies Group “Muzzles allow turnout over large areas, increasing exercise and allow slow “trickle” feeding, to control weight gain and reduce the risk of obesity-related disorders, without significantly compromising the natural behaviour and wellbeing.”
Water soluble carbohydrate levels in the sward were similar across the seasons although they were slightly higher in autumn. However, once muzzled the ponies’ intake of WSC wasn’t significantly different across the seasons; strengthening the evidence that the use of grazing muzzles is effective.

Grazing muzzles must be used with care, should be properly fitted and horses and ponies should be adapted gradually to wearing them. Group and individual behaviour should be monitored closely to observe any potential concerns caused by changes to the herd dynamics. Ensure that muzzled ponies are confident in drinking and drinking through their muzzles before turning them out for prolonged periods. Muzzles must not be used continuously (not more than 10 hours per day) and total exclusion muzzles are not advised. Regular weight monitoring is recommended as some individuals can still gain weight when muzzled.