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Hay Net Height: Consider Comfort Of Horses

Horsemanship masters and mavens of yesteryear taught their students to hang haynets high and tight. Low-slung haynets invited injury, the experts cautioned. A resurgence in the use of haynets has occurred recently, frequently as an attempt to slow hay consumption among horses on calorie-restricted diets. A high-tied haynet, however, encourages horses to crane their necks and contort their backs over a long period of time. Because habitual, unnatural postures can cause discomfort, even unsoundness, Italian researchers set out to determine the physical effects of haynet height on neck and back shape.^*

“Horses and ponies seem to be quite specific in how they approach eating from a haynet,” said Catherine Whitehouse, M.S., a nutritionist with Kentucky Equine Research. “Some nibble from them, grasping pieces of hay carefully; some go in for large mouthfuls, aggressively yanking out hay. Others will headbutt the bag, leaving it swinging from its knot.” Whatever their interaction with the haynet, Whitehouse said, changes in body position invariably occur and likely become a matter of routine.

In the study, researchers used geometric morphometrics to evaluate variations in neck and back shape relative to three specific hay-feeding positions. Geometric morphometrics allows scientists to identify and analyze minute postural changes through the use of anatomical landmarks. Specifically, geometric morphometrics eliminates differences based on size and instead focuses on changes in shape of individuals. Hay was fed from three positions:

Control position. The hay was fed from the ground
Low haynet position. The bottom of the haynet was level with the midpoint of the cannon bone
High haynet position. The bottom of the haynet was level with the elbow

Researchers used slow-feed haynets made from high-density polyethylene twine. The openings of the haynet measured about 1.5 in (4 cm), and the haynets were filled with 4.5 lb (2 kg) of the same hay horses were accustomed to prior to the study.

Video recordings were made of six mature Warmbloods as they ate hay from the three different feeding positions. Using a cellphone placed on a tripod, which assured a consistent perspective, horses were recorded for 15 minutes while eating hay at each feeding position.

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Researchers found that feeding positions affected the shape of the neck and back postures during hay consumption, and these changes in shape were well defined for individual horses. With the low haynet position, the back posture more closely resembled that exhibited during the control position, indicating a more natural feeding position, but the same was not true of neck posture. Both neck and back postures were changed considerably when hay was offered in the high position, potentially leading to problems.

“Certain haynets and feeding devices designed to encourage slow consumption have refined the level of management that can be achieved when dealing with challenging horses, such as those that are chronically overweight,” said Whitehouse. “Even though the researchers identified some changes to neck and back shape, the long-term physical effects of feeding from haynets have not been studied. Right now, the benefits seem to outweigh the potential disadvantages.”

Horses on calorie-restricted diets require optimal nutrition, and this scenario calls for a well-formulated vitamin and mineral supplement, according to Whitehouse. “Because these horses are generally fed all-forage diets, they usually miss out on the vitamin and mineral fortification provided in concentrates. An appropriate vitamin and mineral supplement can fill in the nutritional gaps left by forage.”

For safety's sake: in the study described above, haynets were hung low under the watchful eye of professional scientists. In an everyday situation, whether it's in a trailer or stall, haynets should be hung at a height safe for the individual horse. This will decrease the likelihood of a horse pawing and getting its hoof caught in the haynet.

A Pain In The Neck: Literally

A surgical technique traditionally used for equine limb fractures has shown promise as a repair for horses with a specific type of broken neck. Fractures of cervical vertebra, which can occur from falls, often cause horses to be sore, stiff, and uncoordinated.

Dr. Fabrice Rossignol and colleagues tested the limb repair methodology on three horses with cervical fractures that were referred to Clinique Vétérinaire de Grosbois in Boissy Saint Leger. The surgery stabilized the affected neck bones with screws and plates; on one horse, two vertebra were fused to each other for additional stabilization.

All of the fractures healed and each horse returned to full work. The team concluded that using internal fixation measures on cervical fractures had minimal complications and a positive outcome.

Research Study On Diagnostics For Equine Osteoarthritis Of The Neck

Radiographs have been found to be insufficient evidence for diagnosing Cervical Facet disease according to a research study by Dr. Judith Koenig and a team of researchers at the Ontario Veterinary College. In a video interview, Koenig explains some of the complexities of equine osteoarthritis and cervical facet disease.

“Osteoarthritis is common in any athlete,” explains Koenig “especially as they get older.” The development of bone spurs can cause the facets to become enlarged. Inflammation around the cervical facet joints can affect the soft tissues and nerve roots. It is hypothesized that slight neck instability or overuse can result in remodeling of the joint. There were a larger number of dressage horses relative to the hospital population in the study and dressage horses may be at a higher risk for overuse of the facet joints of the cervical vertebrae.

Clinical signs of Osteoarthritis in the neck include: atrophy/muscle wasting (pronounced hollow in lower neck and vertebrae appear prominent), stiff neck (e.g. limited range in carrot stretch, difficulty when ridden in a “frame”) and sometimes front limb lameness that does not resolve by nerve blocking up the leg.

One of the reasons for the OVC study was the fact that previous studies have shown radiographs indicating changes in the neck of younger horses (6 to 8 years old) with no other clinical signs of osteoarthritis. Koenig has seen for herself, horses dismissed after pre-purchase exams when radiographs indicate mild osteoarthritis. When previous studies indicate 50 percent of clinically normal mature horses present with mild osteoarthritis on radiographs, a study to explore the significance was in order.

Differing opinions in classifying the severity of the stage of osteoarthritis from radiographs was revealed to be a good case for not using radiographs alone in diagnosis. “The repeatability of grading of osteoarthritis from radiographs was not reliable,” says Koenig. Two-thirds of the horses in the OVC study that were treated with intra-articular cortisone injection returned to their full level of work. The study concluded that radiographs alone were insufficient to diagnose cervical facet disease and other clinical signs (atrophy, stiffness, or lameness unresolved by nerve block) need to be present.

Watch the Equine Guelph video here.