Hay Net Height – What Does the Evidence Say?

After sharing a research-related post on Facebook recently, our Vetrehabbers took me on a very interesting journey as we discussed the research behind hay net height. Should we be feeding from the ground, from low-hanging hay nets, from high nets, from all the above, or from none of the above?

While the evidence remains lacking, observation of the individual horse’s physical and mental needs allows us to develop a feeding system that will benefit that individual. Variations in hay net height and size are, in fact, factors that we can manipulate to achieve specific goals in rehabilitation.

Let’s dive into what the evidence says.

Studying the shape variations of the back, the neck, and the mandibular angle of horses depending on specific feeding postures using geometric morphometrics, Raspa et al., Animals 2021, 11(3), 763; https://doi.org/10.3390/ani11030763

This is the article that went ‘viral’ on social media and sparked our conversation on the Online Learning for Equine Vet Rehab Therapists page.  

Insights from the article: This article compared the shape variations in back and neck posture in horses feeding from the ground, at carpal height and above wither height.

The study assumed the control position of feeding from the ground to be ideal, and showed that the back and neck posture, as well as mandibular angle, were different in the high position. The low net position more closely resembled the control back posture, but the neck and mandibular posture were significantly different.

Insights from our conversation: There were two main objections to the design of this study, and the recommendations made: The first is that the images show very limited space in the stable for the horse, which would certainly have affected their posture as they were only able to stand in one place to eat, and could not move any further away from the net.

The second objection is based on the teachings of Sharon May Davies, who recommends variable feeding heights. This recommendation comes from the observation that horses in the wild will graze as well as browse, therefore eating at variable heights. This active feeding from variable heights causes the horse to stretch, flex and rotate the head, neck and poll, actively moving through various ranges of motion and activating and stretching the involved muscles. This has been referred to as ‘active physio’.

An additional comment was made about horses that have a tendency to overload the forehand or to graze favouring one limb. In these cases, raising the feeding platform to chest height allows the horse to stand squarely with the forelimbs and have a more beneficial horizontal balance, to counteract their natural tendency or asymmetry.

Browsing – an overlooked aspect of feeding management in horses? Van Den Berg et al., Australasian Equine Science Symposium

Insights from this presentation: Horses have evolved primarily as grazing herbivores, consuming an estimated graze to browse ratio of 9:1, which in some cases has been seen to be closer to a 1:1 ratio, depending on the availability of feed.

This raises the question: Does limiting foraging opportunities have a negative impact on digestive health, and what are the welfare implications in domesticated horses?

Some of the potential benefits of browsing include the provision of key nutrients, reducing boredom-related behaviours, and encouraging a full range of motion and activity of the cervical spine, poll and jaw.

Hay Net Preference in Quarter Horse Mares, Garrett

This thesis from the Ohio State University looked at the preference of mares when given the option to eat from three different kinds of hay nets, at three different heights. The three hay nets had small, medium and large openings, and hay was provided in each net in equal portions. The hay was fed from three heights; the ground, shoulder height and whither height.

Horses consumed hay from the large nets before moving on to the smaller nets, as well as consuming all their hay through the course of the night from all nets.

Their results suggest that horses prefer to feed from the ground and in as unrestricted a manner as possible.

So why don’t we feed from the ground without nets? According to the above study, horses spent a mere 0.8 hours consuming the hay in the large-opening net, compared to 2.7 hours on the small-opening net. This gives us an answer to the question. When hay is fed freely from the floor, horses will consume all the available hay in a very short space of time – they will consume much more hay than they would if they were grazing continuously. In an attempt for us to slow down the rate at which they eat, to alleviate boredom, to prevent overeating, and to more closely mimic the way in which they would consume food when on pasture, we use hay nets.

What about their teeth?

For many years, I have believed that horses eating from high hay nets will wear their teeth down in an abnormal way and that this leads to some of the dental abnormalities and problems commonly seen in horses. I have searched Google Scholar for articles that might shed light on this observation or belief, but have come back empty-handed. Is this truth speculation? Or is it based on evidence?

Here is what I do know:

1. The alignment of the jaw changes with the position of the head. Leslie Goff demonstrates this beautifully in her lectures on the temporomandibular joint, in which she shares an evaluation technique where the occlusion of the incisors is evaluated from a low head position to a high head position. The incisors should occlude well when the head is down, and as the head raises the lower jaw will pull back and there will be an overbite of the top incisors.

What does this mean for horses feeding from heights? How does this impact them?

2. The molars of the upper jaw are wider than the lower jaw, requiring a lateral grinding that is even in both directions to wear the horse’s teeth down evenly and to prevent waves and hooks from forming.

If wild horses both graze and browse a variety of roughage, firstly they will be eating with different head heights, and secondly, they will be chewing through a variety of roughage – potentially much coarser and harder than our stabled horses are exposed to. Are our stabled horses, therefore, eating larger quantities in a shorter space of time, spending less time chewing the forage, and potentially putting less effort into chewing forage? In addition, in a domesticated environment, they will more easily be able to favour chewing to one side or the other, as they can feed in a routine way day in and day out, a luxury wild horses won’t have.

If you are aware of any evidence available on the correlation between hay net feeding and tooth wear in horses, please share them with us.

Thoughts from our community

Kathy Adams says, ‘I have been implementing some “passive physio” ideas, such as feeding from a higher position, and the thought here is to encourage the vertical balance through the shoulders. In the grazing position they usually have the dominant foot forward which is entrenching the side dominance/asymmetry patterns, but if they’re able to feed from chest height or higher then they tend to stand square, and this will help with building the thoracic sling strength equally. We may spend half an hour working them every day to try get this vertical balance established, but then once they’re back in the field, they’re straight back to leaning on that shoulder.

I placed my hay bowl on top of a tractor tyre so my horse has been eating at chest height, and I found that this really helped build up her strength in the thoracic sling area. Apparently feral horses also browse from trees and bushes around 20-30% of the time, so this is a natural feeding position. If the horse had back pain or kissing spine, then yes, maybe feeding high would be more of a concern; otherwise, I’ve seen great results so far with variable feeding positions.’

Dr Raquel Butler from Integrated Veterinary Therapeutics says, ‘I agree that hay nets and other environmental aspects such as stabling, etc. alter head, neck and back posture and can cause problems. Having utilised variable feeding positions for a number of years in client’s horses and my own I have noted that it can also make horses very sore if inappropriately used. My own horse for example has neck problems and gets sore in the neck when eating out of a small-hole hay net hung up in the tree or a hay net on the ground that is very full (and it’s a toss-up between feed time management and body effects) but he is good with a hay bag – comfortable, relaxed, square posture. My young horse’s posture is completely different and requires different feeding positions to aid her posture. In my opinion, it is important to observe each individual horse, knowing their body issues and observing the postural response to different feeding positions or modes, and offer variable feeding positions to suit your postural and feeding aim, which does not need to be an hour a day – 10-20 minutes 2 x a day can make a difference with a gradual introduction. We also need to consider the type of hay and how full the hay net is [in relation to] how difficult it is to get out of the net, as this will increase flexion of the OA joint, too, and potential stresses on the body. Keep in mind horses are designed to browse 20% of the time and browsing means above the knee.

There are many factors to be considered in each individual case and this study confirms a few things that are pretty obvious;

1.  There is individual variation;
2. back posture is more similar when eating off the ground and a low hay net;
3. neck posture is more similar with low hay net to higher hay net potentially as they are pulling hay out of the net.

We also need to consider individual postural challenges such as hoof balance issues which will alter back posture at different feeding positions in a potential negative way. I believe grazing symmetry is important in the general symmetry of our horses and we should be aiming for even grazing of either forelimb forward and square, which appears to be promoted by the correct use of variable feeding positions.
Having dissected and observed Koniks that have browsed as a part of their natural habit it was amazing to see the symmetry in grazing, the strength of the hypaxial and epaxial muscles particularly the psoas and transverse abdominus.’

Linda Walker shares, ‘As a physio I’m always thinking about preventative measures first whenever possible! So although this study has limitations, it gets us thinking in the right direction for our horses’ well-being. Other considerations are also the repetitive nature of movement in the upper cervical region created by feed nets; and also consider any shoulder issues your horse may have where ground-feeding may add extra weight-bearing to this area ’

Conclusion

From our little summary of the evidence available, it is clear that at this point there are still many more questions than answers, and it remains difficult to make one blanket recommendation based on the research available. My recommendations would be:

1. Treat each horse as an individual; consider their specific imbalances and postural requirements, and try and feed primarily from a position that will improve and benefit those imbalances.
2. Provide as much variety as possible, both in terms of feeding height and variety of roughage, both in the stable and in their pasture environment.

Always be aware of the dangers in any given situation – using a hay net with large holes in a low position is a risk factor for horses getting their feet caught in the net. Only use nets with small openings in a low position, or no net at all.