| Comments |
"Table 3 summarizes estimates obtained in various species for the contribution of VFA to the energy requirements
of the whole body. Considerable variation is
present, and errors undoubtedly have arisen because of
methodology or assumptions by the authors. In general,
in vitro incubation techniques tend to underestimate
VFA production, and in vivo techniques tend to be the
most reliable. Also in most cases only the cecum or the
large colon was used for calculation. Despite these uncertainties,
however, considerable energy must be
available from the VFA produced in the lower gut:
values from 5 to 30% were obtained, and these are in
keeping with the differences in diet and digestive tract
morphology. All values were, of course, lower than that
obtained from the rumen. The highest figures of 30%
were obtained from rabbits and ponies: this is expected,
since they are entirely herbivorous and are hindgut
fermenters. Pigs and humans seemed roughly comparable,
and this also is expected in view of their similarities
in digestive tract morphology. The value of 6-10% for
humans (Table 3) was calculated on the basis of a typical
British diet where 50-60 g of carbohydrate (15 g
fiber and 35-50 g sugar and starch) are fermented per
day (ref 209 (beneath table))." |