Characterisation of defatted Scenedesmus dimorphus algal biomass as animal feed.

Defatted microalgal biomass (DAB) of a local
Scenedesmus dimorphus strain was characterised as animal
feed in an experimentalWistar rat model. The DAB contained
21.5 % protein, 28 % dietary fibre and 21 % ash on dry basis.
The DAB was rich in calcium (1208 mg 100 g−1 biomass)
followed by magnesium (400.6 mg 100 g−1) among the tested
mineral elements. The essential amino acids (EAA) constituted
48 % (w/w) of proteins, and the EAA index was similar to
casein and soybean. The protein was limiting in sulphurcontaining
amino acids cysteine and methionine. The algal
biomass showed 5–6-fold higher water absorption capacity
(3.44±0.06 g g−1 biomass) compared with basal diet
(0.67±0.06 g g−1 biomass). The DAB was found to be safe
in both short-term (14 days), single-dose feeding (20 % (w/w)
feed) and long-term (90 days) repeated-dose feeding (at 5 and
10 % (w/w) feed). In the short-term feeding trial, faecal output
and water intake increased by 2-fold during the initial 4 days,
mainly attributed to higher ash and fibre content of biomass.
The long-term repeated-dose feeding of DAB did not induce
any physiological changes in rats such as feed intake,
haematology profile, serum biochemical parameters, histopathology
and relative organ weight. The feed conversion ratio
and quotient of protein efficiency ratio in DAB-fed groups
were similar to control. However, animals required a longer
adaptation period to DAB-mixed feed, as indicated by slower
body weight gain and feed intake. The study suggests that
DAB can be used as animal feed up to 10 % (w/w) replacement
levels.