“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.

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.

Read more here.

^*Raspa, F., A. Roggero, C. Palestrini, M.M. Canavesio, D. Bergero, and E. Valle. 2021. Studying the shape variations of the back, the neck, and the mandibular angle of horses depending on specific feeding postures using geometric morphometrics. Animals 11:763:11030763.

Reprinted courtesy of Kentucky Equine Research. Visit ker.com for the latest in equine nutrition and management, and subscribe to Equinews to receive these articles directly.