In the wild, horses graze for about 14 to 16 hours daily. This means they constantly consume small portions of roughage, keeping their digestive system active. The digestive system is therefore adapted to this. Sometimes, it is simply impossible, for example, due to an increase in body weight, to provide the horse with 14 to 16 hours of access to a grass field or ad libitum roughage. Due to current management systems, most horses are also kept indoors at night and are given a portion of roughage on the ground. Horses often consume their roughage too quickly, leaving them without food, which is detrimental to their digestive system. To make sure the horse eats its roughage slowly and to prevent long periods without food, a "slow feeder" or hay net is used.
The Importance of Sufficient Roughage
Roughage forms the basis of a horse's diet and is important for a healthy and well-functioning digestive system. It also contains fibre, which is fermented in the intestines into volatile fatty acids. Sixty to seventy percent of the daily energy a horse absorbs from food comes from volatile fatty acids 1. Fibre is therefore an important source of energy for the horse 2. These volatile fatty acids are also required to support a healthy composition of the hindgut microbiome. A healthy hindgut microbiome composition is essential for the optimal functioning and health of the intestines 3. Additionally, the hindgut mircobiome are responsible for the fermentation of fibre. To provide enough roughage, the horse should receive at least 1.5% of its body weight in kilograms of roughage. This means that a 600kg horse should receive at least 9kg of roughage per day.
Besides being essential for healthy intestinal function, roughage is also important for the horse's stomach. Horses chew roughage longer and more frequently compared to, for example, concentrates, resulting in more saliva being produced in the mouth. Saliva contains a substance that neutralises stomach acid 4. Stomach acid can become very acidic, and the buffering effect of this substance reduces the acidity. Moreover, roughage also can absorb and remove excess stomach acid 5. If stomach acid becomes too acidic, ulcers can develop. This is painful and negatively affects the health and performance of the horse. If the horse has no access to roughage for too long, longer than 4 to 6 hours, the chance of developing stomach ulcers increases. Naturally, horses eat small portions of food frequently throughout the day, producing saliva that buffers the stomach acid, keeping the digestive system, especially the intestines, constantly in motion. However, it is not always feasible (for example, at night when horses are stabled) to provide the horse with frequent small portions of roughage. In such cases, a haynet or "slow feeder" can be used to ensure that the horse eats slowly and it will take longer to finish the given portion of roughage.
The Use of a Haynet to Extend the Eating Period
As previously mentioned, horses graze for most of the day. This allows them to take frequent small portions of food and engage in natural behaviour. Practising this foraging behaviour is important for the health and wellbeing of the horse 6. However, sometimes it is not possible to provide the horse constant access to a grass field, offer frequent small portions of roughage, or provide ad libitum roughage. Additionally, when horses eat roughage from the ground, in the natural position, they finish it more quickly. To extend the intake of the offered roughage and ensure the horse takes small bites at a time, a haynet can be used.
There are different types of haynets, such as those with smaller or larger holes, which affect the eating time of the horse. Lundqvist and Müller (2022) demonstrated in a study that the total eating time for roughage increased by up to 1.5 times when using a haynet, compared to feeding roughage from the ground. The holes in the haynets used in this study measured 3.5 cm by 3.5 cm 7. When horses ate roughage from the ground, it took them about half an hour to consume one kilogram of dry matter. Additionally, Ellis et al. (2015) demonstrated that the use of multiple feeding points (including several haynets) in the stable helps extend the intake of roughage and it takes longer for the horse to finish a portion of roughage 8. In another study by Ellis et al. (2015), results showed that by using haynets with small holes (25-30mm), horses took 5 minutes longer to eat 1 kilogram of roughage compared to roughage offered in nets with larger holes (75mm). Moreover, the smaller nets also helped spread the total eating period of the horse more evenly over the entire test period 9. According to a study by Ragnarsson et al. (2024), using haynets with holes measuring 10 by 10 cm led to horses taking 13% longer to consume roughage (averaging 12 minutes per kilogram of dry matter) compared to when they were fed roughage directly from the ground.d 10.
DeBoer et al. (2024) conducted a study showing that using haynets helped to better maintain horses' body weight compared to feeding roughage from the ground. In a two-year study, horses were divided into two groups, during which the group without haynets gained an average of 20kg, while the group with haynets lost an average of 23kg. This resulted in an average weight difference of 43kg between the groups 11. Both groups of horses had unlimited access to roughage during this study.
Therefore, using haynets helps extend the horse's eating period, meaning they take longer to finish a portion of roughage. When using a hay net, it is important to hang it at the correct height in the stable. As previously stated, the natural position for the horse's head is lowered to the ground. Hanging the net too high can make it difficult for the horse to reach. Moreover, when the haynet is hung too high, dust particles from the roughage can get into the horse's nose and eyes. Since the respiratory system and eyes are sensitive to small dust particles, it is not advisable to hang the haynet too high. However, the haynet should not be hung too low, as it could pose a danger for horses with shoes.
The way the horse eats roughage from the haynet also depends on the type of roughage in the net. Roughage with higher moisture content, such as silage, causes the horse to pull harder on the net, putting pressure on the horse's skeleton 12. It can also affect the horse's teeth. More research is needed to better understand the effect of haynets and the pulling force of the horse on the skeleton and teeth.
Overall, when used correctly, haynets are a good way to extend the horse's eating time to support and promote the health of the digestive system. It also has a positive effect on the horse's body weight and body condition.
References
Bergman, E.N. (1990) Energy contributions of volatile fatty acids from the gastrointestinal tract in various species. Physiological Reviews, 70(2): 567-590.
Argenzio, R.A., Southworth, M., Stevens, C.E. (1974) Sites of organic acid production and absorption in the equine gastrointestinal tract. American Journal of Physiology, 226(5): 1043-150.
Julliand, V., Grimm, P. (2016) Horse species symposium: The microbiome of the horse hindgut: History and current knowledge. Journal of Animal Science, 94(6): 2262-2274.
Luthersson, N., Jenifer, N.A. (2013). Equine Applied and Clinical Nutrition Chapter 34 - Gastric ulceration. In: Geor, R.J., Harris, P.A., & Coenen, M., (Eds.). Equine Applied and Clinical Nutrition. Saunders Elsevier: China.
Sykes, B.W., Jokisalo, J.M. (2015). Rethinking equine gastric ulcers syndrome: Part 2 - Equine squamous gastric ulcer syndrome (ESGUS). Equine Veterinary Education, 27(5):264-268.
Goodwin, D., Davidson, H.P.B., Harris, P. (2002) Foraging enrichment for stabled horses: effects on behaviour and selection. Equine Veterinary Journal, 34(7):686-691.
Lundqvist, H., Mülller, C.E. (2022) Feeding time in horses provided roughage in different combinations of haynets and on the stable floor. Applied Animal Behaviour Science, 253:1-5.
Ellis, A.D., Redgate, S., Zinchenko, S., Owen, H., Barfoot, C., Harris, P. (2015) The effect of presenting forage in multi-layered haynets and at multiple sites on night time budgets of stabled horses. Applied Animal Behaviour Science, 171:108-116.
Ellis, A.D., Fell, M., Luck, K., Gill, L., Owen, H., Briars, H., Barfoot, C., Harris, P. (2015) Effect of forage presentation on feed intake behaviour in stabled horses. Applied Animal Behaviour Science, 165:88-94.
Ragnarsson, S., Víkingsdóttir, S.V., Stefánsdóttir, G.J.(2024) Initial Impact of Different Feeding Methods on Feed Intake Time in Stabled Icelandic Horses. Animals, 14(1211):1-9.
DeBoer, M., Keener, L., Layeux-Parks, J., Scheuller, O. (2024) Effect of hay nets on horse bodyweight, body condition score, hay usage, and dental health in mature adult horses. Journal of Equine Veterinary Science, 136(3):105051.
Hodgson, S., Bennett-Skinner, P., Lancaster, B., Upton, S., Harris, P., Ellis, A.D. (2022) Posture and Pull Pressure by Horses When Eating Hay or Haylage from a Hay Net Hung at Various Positions. Animals, 12(2999):1-18.
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