Effect of hay nets on subluxations, pain-pressure thresholds, and cervical range of motion in the axial skeleton of adult horses

Horses have become more intensively managed, including the use of hay nets to increase intake time and reduce hay waste, but their impact on health is not well known. The objectives were to compare changes in subluxations, range of motion, and the pain-pressure threshold in the axial skeleton of horses fed hay with (NET) or without (CON) hay nets. In September 2021, 13 adult horses were blocked by bodyweight (BW) and randomly assigned to the NET or CON treatments for one year. After one year, horses switched treatments and the trial concluded in September 2023. Horses were housed in dry lots with free choice access to round bales with or without hay nets (4.45 cm openings). Chiropractic adjustments occurred in May and August each year to note axial skeleton subluxations. Evaluations occurred in June, July, and August to measure cervical range of motion and mechanical nociceptive thresholds (MNTs) of the jaw, poll, and withers. SAS was used and significance was set at P≤0.05. There was an average 1.6-point increase in cervical subluxations observed in NET horses (P<0.05) while no changes were observed for the TMJ and thoracic or lumbar vertebral regions (P>0.05). Average cervical range of motion was 5 degrees greater in NET horses compared to CON horses for chin to chest and chin to fetlock measurements (P≤0.05). No differences were observed in MNTs (P>0.05). These data suggest that netted round bales may only have minor impacts on the axial skeleton of horses over 12-weeks.