|dc.description.abstract||Studies were carried out to determine the nutritive value
of grain amaranth as a feed ingredient for broiler chickens and
assess the extent to which it could replace maize in broiler
diets. Three grain species were evaluated namely, Amaranthus
cruentus L., Amaranthus hypochondriacus L. and Amaranthus
caudatus L .. In the preliminary study, the chemical attributes
of the grain were assessed. The average crude protein and
metabolisable energy contents of the three grain species were
15.80% and 3310 kcal/kg, respectively. The mean lysine and
sulphur amino acid levels were 0.78 and 0.67%, respectively. The
mean tannin and trypsin inhibitor contents were 0.093% and 0.65
trypsin inhibitor units/mg, respectively. A. caudatus species
had superior nutrient composition but contained the highest
levels of antinutritional factors.
In Experiment I, raw grain from each of the three species
was incorporated in broiler starter diets at 20, 40 and 60%
levels. Chick body weight and feed intake at four weeks of age
declined (P<0.05) while pancreas weights increased with
increasing levels of dietary amaranth. The 20% A. hypochondriacus
diet however gave similar (P>0.05) chick performance to that of
the maize-soyabean meal control diet. Upon thermal extrusion of
grain amaranth in Experiment 2, chick performance markedly
improved, with the 20 and 40% A. hypochondriacus and A. cruentus
grain diets showing similar (P>0.05) body weight, feed intake and
feed efficiency as the maize-soya bean meal control diet.
In Experiment 3, inclusion of lysine, lysine plus methionine
and casein in 40% raw and 60% thermal processed A.
hypochondriacus diets showed similar (P>0.05) chick performance
between the thermal processed amaranth diet containing casein and
the maize-soya bean meal control diet. The latter diet however,
resulted in higher (P<0.05) essential amino acid availability.
Casein increased the levels of various essential amino acids in
the amaranth diets. Chicks on thermal processed amaranth diets
were heavier and consumed more feed than those on diets
containing raw grain amaranth. The low zinc retention from all
the diets indicated interference with absorption of this mineral.
In Experiment 4, casein and ethylene diamine tetraacetate (EDTA)
were separately added to 40% raw and 40% thermal processed A.
hypochondriacus diets. Chicks on the processed amaranth diets
gave higher (P<0.05) body weight, feed intake and nitrogen
retention. Inclusion of EDTA in amaranth diets failed to
increase (P>0.05) mineral retention but the tissue mineral
content of chicks was adequate.
In Experiment 5, 20 and 40% A. hypochondriacus diets with
or without molasses were fed either as raw grain mash diets or
in steam pelleted form. Chick body weight was higher (P<0.05) for
the pelleted and maize control diets at 4 weeks of age. However,
continued feeding up to 8 weeks of age resulted in similar
(P>0.05) chick body weights for all the diets including the maize
control. Pelleting improved (P<0.05) body weight and feed
efficiency and increased (P<0.05) carcass fat but molasses
inclusion had no ~ffect (P>0.05) on feed intake or body weight.
Histopathological studies of chick organs did not show changes
attributable to amaranth feeding.
Growth depression in chicks fed on raw amaranth diets mainly
resul ted from reduced feed intake accompanied by low protein
digestibili ty. Raw and thermal processed A. hypochondriacus grain
can effectively replace maize up to 20 and 40% of broiler starter