Influence of Feeding Horses a High Fiber Diet With or Without Live Yeast Cultures Supplementation on Feed Intake, Nutrient Digestion, Blood Chemistry, Fecal Coliform Count, and In Vitro Fecal Fermentation

• F53 had higher oat straw and total dry matter intake and nutrients' digestibilities.
• The SC47 resulted in lower blood total protein.
• F53 had higher asymptotic in vitro fecal gas production.
• Yeast cultures did not change in vitro fecal pH, CH4, CO2 and dry matter degradability.

Sixteen Quarter Horse mares (body weight: 450–500 kg) were used in a complete randomized design to determine the effects of feeding horses a high fiber diet with or without yeast cultures addition on nutrient intake and digestion, blood chemistry, fecal coliform count, and in vitro fecal fermentation. The treatments were (1) a basal diet without yeast cultures addition (control treatment), (2) control diet plus Procreatin 7 at 15 g/mare/d (P7 treatment), (3) control diet plus Biocell F53 at 11 g/mare/d (F53 treatment), or (4) control diet plus Biosaf SC47 at 15 g/mare/d (SC47 treatment). The basal concentrate diet consisted of a mixture of 50% commercial concentrates and 50% wheat bran fed at 4 kg/mare and offered twice daily at 04:00 and 16:00 hours, while oat straw was offered ad libitum at 05:00 and 17:00 hours. The mares fed the F53 had higher (P < .05) oat straw and total nutrient intakes compared to the control diet. Addition of Biocell F53 and Biosaf SC47 yeast cultures increased (P < .05) all nutrients' digestibilities. Feeding the yeast cultures resulted in higher crude protein (P = .029), neutral detergent fiber (P = .042), and acid detergent fiber (P = .035) digestibilities compared to the control diet. The SC47 treatment had lower blood total protein (P = .014) than the control treatment. Higher (P < .05) asymptotic in vitro fecal gas production was obtained with F53 treatment compared to SC47 treatment without differences between F53, P7, and control treatments. Increased methane production was obtained (P < .05) with F53 and SC47 treatments compared to the control treatment. It can be concluded that daily addition of Biocell F53 yeast culture at 11 g/mare/d resulted in higher feed intake and nutrients digestibility without affecting the mare's health.