Intra-caecal fermentation parameters in ponies fed botanically diverse fibre-based diets

Intra-caecal fermentation parameters in caecally fistulated ponies offered fibrous diets of diverse botanical origin were examined in two experiments, A and B. In Experiment A three ponies were offered ca. 4 kg dry matter (DM) per day of either ground, pelleted hay cubes (HC), a 67:33 mix of oat hulls:naked oats (OH:NO) or a 75:25 mix of unmolassed:molassed sugar beet feed (SBF), whilst in Experiment B the same ponies were offered ca. 4 kg DM of a 50:50 mix of unmolassed sugar beet:hay cubes (USB:HC). In Experiment A, DM intakes (kg per day) were 3.75, 4.03 and 1.72; (S.E.D. 0.26) for the HC, OHNO and SBF diets, respectively, and in Experiment B, average intakes were 4.03 kg per day. (S.E. 0.03). Intra-caecal fermentation parameters were measured in samples of caecal chyme obtained via a permanent in-dwelling caecal fistula. During the three 5-day collection periods, samples were removed 5 h after the morning feed on days 2, 3, 4 and 5; and on Day 4 of each collection period hourly samples were obtained commencing 1 h after the morning feed and ceasing 7 h later. In both experiments, each diet maintained the intra-caecal pH above 6.5 and molar proportions of acetate above 700 mmol mol−1 throughout the 8 h measurement period. When the entire diet consisted of SBF, voluntary feed intake was reduced, indicating that SBF should not be fed to ponies as the sole dietary ingredient. Each of the diets maintained caecal pH well above the critical level of pH 6, which is regarded as the threshold of sub-clinical caecal acidosis in equids. Thus, these three fibre-based feeds can be incorporated into equine diets, offering alternatives to hay as the forage component of the diet without compromising hindgut function.