| Back to programme |
|
Crop-livestock systems reduce the dependency on commercial
feeds, and facilitate the use of organic rather than chemical
fertilizers. Water spinach (Ipomoea aquatic) appears to have
a great potential in such systems as both biomass yield and protein
content increase with fertilization from organic fertilizer.
Earlier observations showed
that rabbits grew and reproduced satisfactorily on a sole diet of
fresh water spinach, and that supplementary water was not
needed.
Water spinach has higher content of crude protein (up to 25% in
DM) than found in conventional pelleted diets (about 16% in DM). It
was therefore hypothesized that there would be beneficial effects
from supplementing the water spinach with a high energy-low protein
feed. However, when broken rice was offered at levels up to 12
g/day in a basal diet based on water spinach, there was no effect
on growth rate or DM feed conversion. The rabbits that consumed
water spinach alone; grew at 18.1 g/day during the first 6 week
period, decreasing to 9.3 g/day between 7 and 12 weeks with overall
growth rate of 14 g/day during 12 weeks of experiment.
In ruminant animals fed forage diets, increasing the offer level
to twice the expected intake leads to higher DM intake and better
performance as the animals are able to select the more nutritious
part of the feed. It was hypothesized that a similar response might
be observed in rabbits fed water spinach as the protein in the leaf
is higher and the crude fiber lower compared with stems. Increasing
the offer level from 8% (DM basis) to18% of live weight (DM basis)
increased the proportion of leaf consumed, the crude protein intake
and the digestibility of DM and crude protein; however, live weight
gain was depressed. It appeared that fiber became a limiting factor
on the high offer level of water spinach as both the content of
crude fiber and its digestibility decreased as the rabbits ate more
leaves in preference to stems.
Water spinach stems and leaves were offered separately to
observe the eating habits of the rabbits especially the intake of
the caecotrophes. The composition of the stomach contents
(including the caecotrophes) was higher in crude protein and lower
in crude fiber when the diet was water spinach leaves compared with
stems. There were marked diurnal trends in the composition of the
stomach contents during 24 hours for the rabbits fed water spinach
stems, with maximum values at midnight for DM and crude protein and
minimum values for crude fiber. These trends were less marked on
the diet of water spinach leaves.
It is concluded that fresh water spinach has a high nutritive
value with high digestibility of DM and crude protein and that
there are no nutritional advantages from providing additional
digestible energy in the form of broken rice. The crude fiber level
in water spinach appears to be too low to support maximum
performance and better results may be achieved by providing
supplementary fibrous feeds. Feeding water spinach leaves rather
than stems resulted in a lower production of caecotrophes that
might reduce the net supply of protein and B
vitamins.