Grazing on Camelina sativa pasture: effects on mare body condition, metabolic profile, and fecal microbiota

This study evaluated the potential of Camelina sativa as a forage crop for extensive horse breeding focusing on body condition, serum biochemical parameters, 16S rRNA gene sequencing, and metabolomic profiling of mares’ feces. The aim was to characterize microbiota composition, predict microbial functions, and identify volatile organic compounds (VOCs). Six mares underwent a longitudinal study over 12 weeks: in the first 6 weeks, the mares grazed on a control pasture; afterwards, they were shifted to a pasture containing camelina for a further 6 weeks. At the end of each grazing period, blood and feces were individually collected for analysis. Grazing on camelina pasture increased the contents of ash, acid detergent lignin (ADL), and acid insoluble ash (AIA) (p < 0.01), while it decreased the fecal concentration of N-free extracts (p < 0.05), crude fiber, neutral detergent fiber ( NDF ) (p < 0.01), serum alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), non-protein nitrogen (NPN), cholesterol, chlorides, calcium, and potassium (p < 0.05). Alpha- and beta-diversity metrics clearly distinguished pre- and post-diet collected fecal samples, clustering into two different microbiota subclusters. A beneficial effect on the gut microbial community was observed, with an increase in the relative abundance of specific taxa acting as homeostasis biomarkers, i.e., the genera Lysinibacillus and Planococcaceae indicate an enhanced bile acid biotransformation capacity. Although limited by the small sample size, our statistically significant VOCs and predicted metabolic pathways suggest biosynthetic flexibility in response to fiber-rich diets, showing possible microbial adaptation to maintain redox balance with an increased energy yield under fermentative conditions and improved metabolic efficiency in producing short chain fatty acids (SCFAs).