PhD Thesis
In Tanzania, maize scarcity, high cost and competitiveness between humans and
other livestock has necessitated the search for alternative energy sources for poultry.
In view of this, four studies on the assessment of the suitability of commercially
available Tanzanian grain sorghum varieties (GSV) for poultry and evaluation of
appropriate feeding strategies of diets containing GSV were conducted. In the first
study, a cross section survey was conducted in selected food markets of Singida,
Dodoma and Morogoro regions to identify types of available commercial GSV
whereas in the second study, assessment of nutritive values of identified GSV was
carried out. In the third and fourth study, two feeding experiments to evaluate the
effectiveness of using final sugar molasses (SCM) and Moringa oleifera leaf meal
(MOLM) as additive in GSV based diets on performance of growing chicks and layer
chickens and egg quality characteristics and consumers’ preferences were carried
out. Semi-structured questionnaire and personal observation guided by checklist
were used to collect information on type, identity and source of GSV. The identified
GSV were analyzed for proximate and anti-nutritional components, minerals, some
amino acids, metabolizable energy (MEn) and starch using standard procedures in the
second study. GSV collected from local food markets, were ground and packed in
nylon bags for use in the feeding experiments. Fresh Moringa leaves were harvested
dried under the shed, ground through hammer mill to make MOLM. Molasses was
obtained from Mtibwa Sugar Company. Other feed ingredients were obtained from
local livestock feed dealers. 2x3 factorial experiment in which two GSV for high
tannin sorghum (HTS) and low tannin sorghum (LTS); three supplementary
strategies for non-supplemented GSV based diets (CTL) and 10% DM- SCM andiii
10% DM-MOLM (MOL) supplemented GSV based diets to make six dietary
treatments for the feeding experiments. The data of the second study was analyzed
using descriptive statistics whereas for the third and fourth study the General Linear
Model Procedure was used. The results showed that out of the twelve Tanzanian
commercial GSV identified, 75% were predominately landraces with local
identity.58% of GSV had white coat colour and were sourced from Singida and
Dodoma region. The overall chemical composition for GSV was found to be dry
matter (DM) (88.3% ± 0.44), metabolizable energy (MEn) (13.8MJ/KgDM±0.39),
ether extract (EE) (3.2%DM±0.46) and crude protein (CP) (1 l.l%±0.63). In
addition, GSV contained a range of high crude fiber (CF) (1.8-6.8%DM), ash (1.8-
6.9%DM) and condensed tannins (2.1-5.8%DM) as leucocynidin equivalent and low
macro/micro minerals and essential amino acids., The results did not show any
significant correlation between coat colour and amount of condensed tannins in
GSV. The results of the present study showed that use of FITS as a main source of
energy led to poor dry matter intake (DMI), lymphocyte, and oesinophils and
monocyte ratios for growing chicks whereas poor DMI, feed conversion and egg
production were observed in layer chickens but produced more desirable eggs in
terms of aroma, flavour and yolk colour after being stored for long time. The LTS
diets had better DMI, lymphocyte, oesinophils and monocyte ratios and feed
conversion for growing chicks whereas better feed conversion and egg production
were observed in layer chickens but relatively produced undesirable eggs in terms of
aroma, flavour and yolk colour after being stored for long time. The results further
showed that supplementation of GSV based diets with final SCM led to increased leg
abnormality incidences (LAI), paleness of the bird’s body parts and decreasediv
lymphocyte and oesinophils ratios for growing chicks. In layer chickens decrease in
egg production and impairment of feed conversion, egg aroma, flavor and yolk
colour when final sugar cane molasses was added to GSV based diets were noted.
Addition of MOLM to GSV based diets, prevented occurrence of LAI and improved
colour of the bird’s body parts; monocyte, lymphocyte and oesinophils ratios and
feed conversion for growing chicks. Egg production, feed conversion, Roche egg
yolk color scores (RYS) and consumers’ yolk colour score index (YSI) were
improved by the addition MOLM in GSV based diets for layer chickens. It can be
concluded that Tanzanian commercial GSV have high feed component and energy
content showing their potential in poultry feeding but their utilization could be
limited by presence of high anti-nutritional factors and low content minerals and
amino acids. Moreover, FITS has relatively lower feeding values than LTS in poultry
feeding may be due to the negative effects of tannins which impair the utilization of
nutrients though they may produce relatively more desirable egg in terms aroma and
flavour qualities when stored for long time. However, LTS has higher feeding value
for poultry due to nutrition adequacy although may cause to leg abnormalities in
chicks if it contains high phytates and may lead to unpleasant egg aroma, flavour and
yolk colour when stored for long time. It can further be concluded that utilization of
MOLM additive to GSV based diet for poultry improve feeding value of HTS and
LTS in layer chickens due to its ability to compensate deficient minerals, pigments,
energy, amino acids and proteins. But, use of SCM additive to GSV based diet for
poultry worsens HTS and LTS feeding values due to the negative its effects in
utilization of nutrients associated with its ability to increase rate of passage in gastro
intestinal tract. Following findings of this study, partial utilization of Tanzania GSVV
as a source of energy in poultry feeding is recommended but it’s fully use should be
accompanied by supplementation of synthetic minerals, pigments and amino acids or
strategic feeding options. Moderate use of HTS in layer chickens’ diets is suggested
but fully utilization should require supplementation of synthetic pigments, minerals
and amino acids and energy sources or strategic feeding options for health chicks and
production of desirable eggs. Fully utilization of LTS in layer chickens’ diet is highly
recommended but requires supplementation of synthetic pigments and minerals for
production health chicks and desirable eggs. Addition of up to 10%DM- MOLM
level for improving HTS and LTS feeding value for layer chickens is recommended
whereas the use of 10%DM- final SCM level is not suggested. Further research is
recommended to evaluate economics of using MOLM additive to GSV based diet for
layer chickens and nutritive value of different GSV in Tanzania rural.