Wheat straw put to the test in a dietary study in horses

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Wheat straw may be beneficial for horses with low energy needs, but more research is needed.
Wheat straw may be beneficial for horses with low energy needs, but more research is needed, researchers say. File image by ratexla (protected by Pixsy)

Good quality wheat straw provided at half the daily forage ration for horses with low energy requirements may be beneficial for their welfare, the findings of fresh research suggest.

Anna Jansson and her fellow researchers, in a study published in the journal Animals, investigated straw as an alternative to grass-based haylage for horses.

They explored the effects of straw on the metabolic profile of horses involved in the experiment, examined their energy intake, assessed their behaviour and checked whether the diet resulted in gastric ulcers.

The researchers involved in the study at the Swedish University of Agriculture Sciences noted that many leisure horses have low energy requirements, and obesity is common.

“Straw has a low energy content and could be a forage option for these horses,” they said. “However, a previous study suggested that providing straw as the only forage was associated with an increased risk for gastric ulcers.”

Their study evaluated replacing half of the daily forage allowance with a good hygienic quality wheat straw.

Six horses from three different yards were enlisted for the study, aged 3 to 15 and weighing 220 to 570kg. Their body condition scores ranged from 5 to 8 or 9 on the 9-point scale. No owner reported any current clinical issues and there was no clinical history of colic or gastric ulceration. All had been out of training for at least 6 months before the study.

Each of the stabled horses spent three weeks on the control diet, which was grass haylage only, and three weeks on a diet comprising half grass haylage and half straw (on a dry matter basis).

All horses were evaluated on both diets.

The study team, which performed a gastroscopy on each horse before beginning the feed experiment, and after three weeks on each diet, found no effect on the prevalence of gastric ulcers, either in the upper or lower portion of the stomach.

Feed intake time was longer and daily energy intake lower on the diet that included straw, compared to haylage only.

Blood tests showed that plasma insulin levels were lower on the diet with straw compared to the haylage, which could be beneficial for horses with overweight or insulin problems.

Faecal dry matter content was not affected by diet, and no difference was detected in the number of intestinal sounds between the diets. Faecal water was also within normal ranges and did not differ between diets.

“The results suggest that good hygienic wheat straw provided at 50% of the forage ration does not cause gastric ulcers, but may prolong feeding time and promote a metabolic profile more suitable for overweight horses,” they said.

“Including straw as part of the ration, therefore, may improve welfare for horses with low energy requirements.” It could, they said, benefit overweight horses without increasing the prevalence and severity of gastric ulcers.

“In an earlier study, feeding with straw as the only/major roughage source was associated with a higher risk of gastric ulcers. One might speculate that the slower consumption rate of straw in the present study when fed at 50% of the forage ration could be a protective factor for the development of equine gastric ulcer syndrome.

“Interestingly, in the current study, the prevalence and severity of gastric ulcers actually decreased over the study period. It is possible that the transportation and initial change in the environment contributed to the formation of ulcers in some of the horses.

“However, the fact that there was no increase in gastric ulceration during the trial does suggest that both diets were supportive of gastric health.”

The authors said that one of the theoretical benefits of straw is that, if energy restriction is needed, caregivers can keep the roughage allowance high to support normal feeding behaviour, while still keeping energy intake low.

“Certainly, recent work seems to suggest that straw addition may help to promote weight loss in grazing equids. As both obesity and insulin dysregulation are risk factors for horses to develop laminitis the results of the present study suggests that replacing half of the daily forage allowance with straw may be beneficial to horse health in individuals prone to these conditions.”

They noted that the plasma insulin response was lower on the straw diet than on the grass haylage diet, which could be expected based on their water-soluble carbohydrate contents.

“Interestingly, during the evening meal, there was no significant increase at all in insulin when on the straw diet, again possibly reflecting the slower feed intake behaviour.”

Blood tests showed that plasma insulin levels were lower on the diet with straw compared to the haylage, which could be beneficial for horses with overweight or insulin problems.
Blood tests showed that plasma insulin levels were lower on the diet with straw compared to the haylage, which could be beneficial for horses with overweight or insulin problems. File image by Yvonne L Sweden

They concluded: “Although this was a small short-term study it suggests that wheat straw of good hygienic quality can be included at up to 50% of the diet of forage-fed horses without any apparent increased risk of gastric ulcers. In addition, it slowed feed intake and seemed to promote a metabolic profile suitable for overweight horses.

“Straw may accordingly also be an effective component of a weight loss management programme. However, as the present study was performed using a low number of overweight horses, further studies are required to confirm this.”

The study team comprised Jansson, Sara Larsdotter Davey and Sara Ringmark, all with the Swedish University of Agricultural Sciences; Patricia Harris, with the Waltham Petcare Science Institute in England; Nanna Luthersson, with Hestedoktoren I/S; and Sveinn Ragnarsson, with Hólar University in Iceland.

Jansson, A.; Harris, P.; Davey, S.L.; Luthersson, N.; Ragnarsson, S.; Ringmark, S. Straw as an Alternative to Grass Forage in Horses—Effects on Post-Prandial Metabolic Profile, Energy Intake, Behaviour and Gastric Ulceration. Animals 2021, 11, 2197. https://doi.org/10.3390/ani11082197

The study, published under a Creative Commons License, can be read here.

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