PSIII-10 A comparison of pelleted vs extruded feed form on feeding behaviors of horses.

Abstract Chewing plays an essential role in horse health via stimulation of saliva production. Feed form may influence both chewing behavior and salivary volume, but no data are available regarding impact in horses. The purpose of this study was to investigate the effects of feed form on chewing activity, feeding behavior, and salivary parameters in horses. Quarter Horses (n = 6) with normal dental exams were utilized in a 28-day single crossover study to evaluate treatment diets formulated with identical ingredients and nutrient content (Treatment A = pelleted; Treatment B = extruded). Horses were acclimated to treatments for 16 days and fed twice daily (approximately 1.36 kg/meal). All horses were turned out to pasture daily with ad libitum access to water and white salt blocks. To measure salivary volume and other parameters, saliva samples were collected prior to and following each meal using sterile swabs (Salimetrics, State College, PA). Horses were outfitted with halters equipped with sensors (EquiWatch System®) to monitor mastication, meal consumption time, and jaw movements (chews) during each feeding session. Total data collection included 98 meal sessions and 186 saliva samples. Statistical analysis was performed using SAS (version 9.4), with significance set at P < 0.05. Feed residue was scored as high, medium or low on each saliva swab, and was analyzed using the Chi-Square (PROC FREQ), while mastication and salivary data were analyzed using ANOVA (PROC MIXED). Consumption time did not differ between diets: (Pelleted: 16.47 ± 0.73 min; Extruded: 16.45 ± 0.67 min; P = 0.99). However, chewing rate per minutes varied (Pelleted: 95.30 ± 1.88 chews/min vs. Extruded: 97.47 ± 1.80 chews/min; P = 0.05). Total chews did not differ (Pelleted (1560.09 ± 66.27 chews; Extruded: 1587.78 ± 59.19 chews; P = 0.66). Saliva volume measured pre and post meal did not differ (P = 0.77) between pelleted (0.28 ± 0.11 ml) and extruded (0.24 ± 0.08 ml) diets. However, saliva pH was different (P = 0.02) following each meal, with the extruded diet pH lower (8.29), as compared to the pelleted diet (8.43). Feed residue levels also differed with pelleted diet, swabs were scored as medium more frequently after feeding (47.06% to 60.61%, P = 0.04) as compared to the extruded diet where swabs scored as high residue were increased (16.95% to 36.21%, P < 0.001). These results indicate that extruded and pelleted diets manufactured with identical nutrient and ingredient profiles did not influence consumption time or total chews, but significantly affected chewing rate per second and salivary pH. Cumulatively, these findings demonstrate the complexity of equine mastication and feeding behavior. Future studies should include tests with commercially available pelleted or textured diets in order to evaluate differences between traditional formulations and feed forms.