Effects of feeder style on behavior and plasma cortisol concentrations in group-fed horses

Objective: To evaluate the effects of feeder style (trough vs. individual pans) on behaviors and plasma cortisol in group-fed horses.Materials and Methods: Horses (n = 16) were blocked by sex and randomly assigned to 1 of 2 mixed gelding/mare groups or a mare group in a crossover design. Groups were offered 0.9 kg of alfalfa pellets per horse in either a centrally located trough (TR) or individual pans (IP) spaced a minimum of 20 m apart. Blood samples were obtained 10 min before feeding (PRE), immediately after feed completion or abandonment (POST), and 30 min after feeding (P30), and were later assayed for plasma cortisol. Behaviors were observed and recorded by 2 experienced observers. Behavior scores (calculated as weighted dominant minus weighted submissive) were used to categorize individuals as dominant, submissive, or neutral.Results and Discussion: When not considering behavior score, cortisol concentrations were greater (P < 0.05) before feeding compared with after feeding, and there was no effect of feeder style (P > 0.3). When TR fed, behavior classification influenced cortisol concentrations over time. Dominant horses had greater cortisol concentrations before feeding compared with POST (P < 0.01) and P30 (P < 0.05), whereas no differences over time were observed in submissive horses.Implications and Applications: These data suggest that feeder style does not influence plasma cortisol concenagonistic interactions may be a source of stress in groupfed horses.