Horses, and especially ponies, appear to be more susceptible to obesity and related disorders when given free access to grass than those with restricted access to pasture. Problems that can arise include insulin resistance and laminitis.
However, even reducing time at pasture may not be as effective as previously thought.
Another study, also presented at the meeting, has shown that ponies may adapt their grazing behaviour to eat more in a short time span.
The new research shows that the use of a grazing muzzle could be a much more effective and reliable solution if used appropriately.
Grazing muzzles significantly reduce bite size and intake.
Anecdotally, ponies fitted with grazing muzzles spend a greater proportion of time engaging in foraging and eating directed behaviours than their non-muzzled counterparts, yet either lose weight or retain an established, trim body condition.
The study, conducted by the Waltham Equine Studies Group in collaboration with Dr Annette Longland, of Equine Livestock and Nutrition Services in Wales, aimed to quantify the effect of wearing a grazing muzzle on herbage intake by ponies.
Four mature ponies were recruited for the study. After an adaptation period, their pasture intakes were determined when wearing a grazing muzzle and when grazing without a muzzle. Pasture samples were obtained daily to assess the grazing available.
The research involved measuring weight changes determined for each pony immediately before and after each three-hour grazing period.
Intakes were determined by changes in body weight after taking into account the weight of any faeces and urine, using a calibrated weighbridge.
Pasture intake by the ponies grazing for three hours without muzzles averaged 0.8 per cent (with some eating close to 1 per cent) of their bodyweight, which is the equivalent of up to two thirds of the recommended daily dry matter intake for many ponies on restricted diets.
Owners therefore may under-estimate pasture intakes of un-muzzled ponies, even when they are provided with restricted time at pasture.
In contrast, the pasture intake of the ponies when wearing muzzles was around 0.14 per cent of bodyweight over three hours, representing an average reduction of 83 per cent compared to when they were not wearing muzzles.
Nutritionist Clare Barfoot, who is research and development manager at Spillers, said: "These figures clearly show how effective grazing muzzles appear to be as a method to restrict pasture intake.
"The study has given us helpful, practical guidance on how we can safely manage grass intake to control weight gain and reduce the risk of obesity-related disorders, without significantly compromising the natural behaviour and wellbeing of our horses and ponies."
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.
Total exclusion muzzles are not advised.