Previous studies in horses have demonstrated that dietary fiber intake affects the
weight of ingesta in the hindgut (Meyer 1995) as well as overall body mass (Pagan and
Harris 1999; Warren et al. 1999). In the present study, pre-exercise body weight was
approximately 11 kg lower in RES than in AL even though hay intake differed by only 5
to 6 kg. There are at least two possible explanations for this discrepancy. First, as water
intake tends to parallel dietary fiber intake (Warren et al. 1999), it is possible that the
lower body weight in RES was, in part, due to a reduction in water intake and the fluid
mass in the hindgut. Second, it is probable the effects of reduced fiber intake on the mass
of ingesta in the large intestine are cumulative, as evidenced by the widening of the
difference in body weight between the two groups during the 3 days of restricted hay