PhD Thesis
In recent decades the demand for poultry and livestock products has increased
significantly. Likewise, poultry rearing has been adopted as a tool for poverty alleviation
and has led some development agencies to promote the intensification of improved
poultry systems. Two genetically improved chicken breeds (Sasso and Kuroiler) have
been introduced in Tanzania as a way of improving the productivity of the poultry
industry and improve people’s livelihoods. Performance of any breed is a function of both
genotype and the environment in which the birds are raised. This means that breeds that
perform better in one environment may not necessarily perform better in another
environment. It is for this reason that Kuroiler and Sasso chickens were evaluated to
establish their suitability under different agro-ecologies and management systems in
Tanzania. The selected agro-ecologies in the current study were the highland and lowland
areas of Mvomero district in Morogoro region, Eastern Tanzania. The two agro-ecologies
were purposively selected based on their differences in temperature, altitude, vegetation
type, and farming systems. Alongside, two varied management conditions i.e. on-station
(controlled management) and on-farm (farmer management) conditions were also
considered for performance evaluation of these breeds. The on-station study was
conducted at Sokoine University of Agriculture in Morogoro region. The study was
conducted to evaluate the effects of management, breeds and interaction on growth
performance, egg production, egg quality and survivability.
A total of 1800 day old chicks comprised of 900 Sasso and 900 Kuroiler were procured
from Silverlands Tanzania in Iringa region and AKM Glitters company in Dar es Salaam
region respectively. The chicks were brooded for six weeks at the Poultry farm of Sokoine
University of Agriculture (SUA). Sexing of the chicks was done at end of the 6 th week.iii
The birds of each breed were divided into two groups, one for on-station and the other one
for on-farm evaluation.
The sampling frame under farmer management (on-farm) in the two agro-ecological zones
consisted of two villages per zone, 16 farmers per village and 18 birds per farmer; thus
making a total of 64 farmers and 1152 birds. The farmers involved in the study were
randomly selected from the list of farmers that had more than ten chickens and had been
keeping chickens for at least five years. Birds were raised under a semi-scavenging
system and supplemented with kitchen leftovers, maize bran, and other crop by-products
in addition to scavenged feeds. For on-station study, birds were raised in six replicates per
breed of 40 birds each, thus making a total of 12 pens and 480 birds. They were raised in
deep litter pens and fed a commercial ration.
Production traits that were evaluated and compared under both environments include
growth, egg production, egg quality and survivability. The growth performance traits were
body weight at 6, 8, 12, 16 and 20 weeks of age, total weight gain (TWG) and average
daily gain (ADG). The traits considered for egg production were age at first egg, age at
peak egg production, hen-housed egg production (HHEP), hen-day egg production
(HDEP) and egg production rate. On the other hand, the quality of eggs was evaluated for
eggs from both on-farm and on-station management and they involved both external traits
(egg weight, length, width, shape index, shell weight, shell thickness and shell ratio) and
internal traits (yolk weight, albumen weight, yolk ratio, albumen ratio, albumen height
and Haugh unit). Mortalities were recorded during the growing and laying periods in both
environments. Additional data for the on-station study were feed conversion ratio (FCR)
and carcass traits. Evaluation of the carcass traits involved slaughtering of male chickens
of the two breeds at the 16 th week of age. The traits measured were body weight ativ
slaughter (BWS), carcass weight (CW) and carcass parts yield including breast, thighs,
drumsticks, wings, back and neck. Data were subjected to analysis of variance using the
General Linear Models (GLM) procedure of SAS software (SAS 2009), while mortality
data were analyzed in accordance to frequency procedure of SAS software (SAS 2009)
using a chi-square (χ2) test.
Results show that agro-ecological zones differed significantly (p<0.05) with respect to
growth performance and survivability. Birds raised in the highland zone were heavier
(2021.7 g) than those raised in the lowland areas (1873.6 g). Similarly, birds raised in the
highland zone had lower mortality rates than lowland zone during growing (12.7% vs
20.3%) and laying (34.6% vs 47.1%) periods. Significant interaction (p<0.05) between
agro-ecology and breed was observed on body weight and age at sexual maturity. In the
highland zone, Sasso chickens were heavier and attained sexual maturity earlier than
Kuroiler while in lowland areas the performance of Kuroiler was higher than that of
Sasso.
With regard to management systems, the results show that management systems
influenced significantly (p<0.05) all growth traits, egg production traits and survivability
of chickens in favour of on-station birds. The final body weight and total egg yield
(HDEP) under the on-station were 2510.9 g and 108.3 eggs, while for on-farm were
1870.5 g and 50.5 eggs in respective order. Mortality for on-station birds was lower than
on-farm birds during growing (10.6% vs 22.1%) and laying ( 47.1%) 17.0%) periods. The
results further showed that the mean values of egg weight, length, width, shape index,
shell weight, shell thickness, yolk weight, albumen weight, albumen height and Haugh
unit were also higher for on-station than on-farm while shell, yolk and albumen ratios
were similar between the two management systems. Interactions between managementv
and breed were significant (p<0.05) on body weight, egg weight, shell ratio and all egg
production traits except peak egg production rate and mortality rate. While Sasso
performance was better than that of Kuroiler on body weight and age at first egg under the
on-station management system, Kuroiler was better than Sasso on those traits under the
on-farm condition.
For feed conversion ratio (FCR) and carcass traits, results showed that both FCR and
carcass traits were influenced by breed. The FCR of Sasso was lower than that of
Kuroiler. Carcass weight, dressing percentage and weight of different carcass parts were
higher for Sasso than Kuroiler. Furthermore, correlations between carcass weight and
carcass parts were high and positive.
Based on the results of these studies, the following conclusions can be made:-
i.The performance traits of the two breeds are dependent on agro-ecological
zone and management systems. The chickens' performance in the highland
zone appeared to be better than in the lowland in terms of growth and
survivability. Similarly, on-station birds performed better than on-farm in
growth performance, egg production and survival rate.
ii.The response of each breed differed in some traits when subjected to
different environments. Kuroiler maintained its bodyweight regardless of agro-
ecology, but it matured earlier and had a lower mortality rate than Sasso in
lowland areas whereas Sasso appeared better in highland than in lowland areas
in growth performance, survival rate and age at sexual maturity.