Nc. Bennett et Jum. Jarvis, COEFFICIENTS OF DIGESTIBILITY AND NUTRITIONAL VALUES OF GEOPHYTES ANDTUBERS EATEN BY SOUTHERN AFRICAN MOLE-RATS (RODENTIA, BATHYERGIDAE), Journal of zoology, 236, 1995, pp. 189-198
Subterranean rodents have high energy requirements when they are excav
ating their burrows. This study investigates the energy available to,
and the efficiency with which it can be extracted by, four species of
bathyergid mole-rats fed natural diets ranging from the underground st
orage organs of geophytes to grass roots and leaves. The digestibility
coefficients of geophytes ranged from 53% for the fibrous tuber of th
e gemsbok cucumber to 95.7% for corms and bulbs. One species, Bathyerg
us suillus whose diet consists of over 80% grass, had a digestibility
coefficient of 87% on an all grass diet. All species had similar coeff
icients of digestibility of > 90% when fed on a uniform diet of sweet
potato. Bulbs and corms had a low fibre content (3.3-4%), high calorif
ic value (15-16 kJ/g) and high digestibility coefficients (95.7-96%) a
nd on this diet the mole-rats maintained their body mass. Food of lowe
r digestibility tended to have a high fibre content(8.2-45%) and, with
the exception of B. suillus, although the mole-rats consumed a greate
r quantity of food, they lost mass. The sweet potato had a low fibre c
ontent(4.1%) but was energetically very similar to bulbs and corms (15
.5 kJ/g). Geophytes which have low fibre contents are generally small
(1-20 g), whereas geophytes with high fibre contents are much larger (
30-2000 g) and often occur in more arid zones.