PSXII-5 In vitro digestibility of dry matter and fiber components and gas production of hays used in equine diets and incubated in equine cecal inoculum.

Abstract The objective was to evaluate the effect of hay type, commonly used in equine diets, on in vitro dry matter digestibility (DMD), neutral detergent fiber digestibility (NDFD), acid detergent fiber digestibility (ADFD), and gas production (mL/g DM) when incubated with equine cecal inoculum. We hypothesized that warm-season grass hays would result in lower digestibility and gas production than legume hays, and that different cultivars of the same forage would differ in these parameters. Five hays (~0.50 g per F57 Ankom bag; ground at 4 mm), including “florigraze”, “tito”, and “peace” rhizoma peanut (Arachis glabrata Benth), “Legendary XHD” alfalfa (Medicago sativa L.), and “coastal” bermudagrass (Cynodon dactylon L.), were incubated with equine cecal fluid for 48 h in three replicates per run in three independent runs. All variables (DMD, NDFD, ADFD, and gas production) were measured at 0, 3, 6, 9, 12, 24, and 48 h of incubation. Cecal fluid was collected from one cecally-cannulated quarter horse gelding grazing bahiagrass (Paspalum notatum Flüggé) pasture. Data were analyzed using the GLIMMIX procedure of SAS. Hay type, sampling time, and their interaction were used as fixed effects while run was considered a random effect. Bermudagrass hay had the least DMD (P < 0.01) at all time points, while alfalfa had the greatest DMD at 0 h and 3 h of incubation, but similar to Tito and lower than Florigraze and Peace at 48 h of incubation. Bermudagrass hay had the least NDFD (P < 0.01) at all timepoints, while all three rhizoma peanut hays had greater NDFD than alfalfa after 24 h. All hays resulted in similar gas production at 3 h incubation, while bermudagrass resulted in lesser gas production (P < 0.01) than all legume hays at 6 h of incubation, and Florigraze resulted in greater gas production than Tito at 48 h of incubation. Florigraze resulted in greatest (P < 0.01) ADFD at all time points, except at 24 h of incubation, where it resulted in ADFD similar to Tito and Peace, and at 48 h of incubation where it was similar to Peace only. At 24 h of incubation, alfalfa hay resulted in ADFD similar to bermudagrass hay. In conclusion, legume hay resulted in increased digestibility and gas production when compared with a warm-season grass hay. At 48 h of incubation the rhizoma peanut cultivars Florigraze and Peace, however, resulted in increased DMD, NDFD, and gas production among all hays tested. Florigraze and Peace should be prioritized in diets of horses with higher nutritional needs as they resulted in increased forage degradation.