124 A wild rice byproduct compares well to traditional wood sawdust as bedding material

Abstract

Minnesota is one of the largest producers of cultivated wild rice in the US, and the straw-like byproduct (rice knuckles) may provide an alternative bedding material for horses while supporting sustainability. Bedding selection is an important factor to provide a healthy environment for horses. This study evaluated the suitability of wild rice knuckles (RK) as an alternative bedding material to traditional wood sawdust (WS) by comparing water absorptive capacity (WAC), air quality, and ammonia levels. Four mature horses (>3 yr old) were used in the crossover study. Horses were randomly assigned to bedding type (RK or WS) for 5 d, then switched to the other bedding type for the next 5 d. Horses were housed in box stalls at night and turned out in paddocks during the day. Total muck production was recorded daily after stall cleaning by 3 individuals. The WAC was tested by soaking bedding material (n = 2) in water using nylon pantyhose for 0, 1, 3, 6, 9, and 24 h and recording the change in weight. An Elitech air quality monitor recorded the concentration of 3 sizes of suspended particulate matter (PM < 2.5 µg/m3, 10 µg/m3, and total PM). Air quality was recorded 3 m above the stall surface after horses were stalled over night and during stall cleaning. Ammonia was measured in the horse's breathing zone by attaching Draeger tubes to horse's halters for 12 h overnight and instantaneous ammonia levels were measured each morning in the stalls.Changes over time in WAC, ammonia, muck production, and air quality were analyzed using a mixed model ANOVA with repeated measures (SAS 9.4). The WAC was higher in WS compared with RK (P = 0.0057) but there was no difference in total muck produced (P = 0.5931). There was no main effect of bedding type on suspended PM (P > 0.05) but there was an increase over time across bedding types (P < 0.05). Suspended PM was lowest the first day and increased during subsequent days. During stall cleaning there were no differences in air quality between bedding type (P > 0.05), however, the average PM 2.5 level (51.5 ± 14.7 µg/m3) was higher than recommended exposure levels (35 µg/m3) for caretakers. Ammonia levels in the RK stalls were lower than stalls bedded with WS (4.65 ± 2.4 ppm and 6.88 ± 2.4 ppm, respectively; P = 0.0125). Horses bedded on RK were exposed to lower levels of ammonia in their breathing zone compared with horses bedded on WS (P = 0.003). Overall, RK appear to be a suitable alternative bedding type to traditional WS. Although the WAC is lower, bedding with RK reduces ammonia exposure of horses and their caretakers. Utilization of agricultural byproducts as bedding provides an opportunity to extract value from these byproducts.