Nigerian Indigenous Chicken: A Valuable Genetic Resource for Meat and Egg Production
This review work aims at determining the potential usefulness of the Nigerian indigenous ecotype chickens and the effect of the major genes of frizzling and naked neck for poultry production in the tropical humid climate. Classification by ecological zones does not consider the effect of the major genes hence the heavy and light chickens or the Fulani and Yoruba ecotype chickens respectively. Heritability estimates of body weight of 0.43 and 0.30 for heavy ecotype chicken at 8 and 20 weeks, respectively is an indication that the heavy chicken ecotype may possess dual potential to be selected as meat type or egg-type bird because 8 weeks and 20 weeks of age are broiler and layer ages, respectively. The frizzling and naked neck genes conferred better feed conversion, growth rate, feed efficiency and dressing percentage than the normal feathered chicken. The feather structure and feather distribution genes are well adaptive to the harsh tropical environment; survive on low energy feed, highly resistant to diseases and superior to their exotic counterparts. Crossbreeding with the exotic breeds improved body weight greatly at 12 weeks of age. Limited reports are available on the molecular characterization of Nigerian indigenous chickens, it is necessary to determine genetic distance between or within indigenous naked neck, frizzled and normal feathered chicken populations for future breeding plans. Thus, this present review provides genetic and performance information on naked neck, frizzled and normal feathered chickens which may be useful for breed improvement and development for future generation.
July 23, 2010; Accepted: August 11, 2010;
Published: October 08, 2010
Indigenous chickens are widely distributed in the rural areas of tropical and
sub-tropical countries where they are kept by the majority of the rural poor.
Indigenous chickens in Africa are in general hardy, adaptive to rural environments,
survive on little or no inputs and adjust to fluctuations in feed availability.
Chickens largely dominate flock composition and make up about 98% (Gueye,
2003) of the total poultry numbers (chickens, ducks and turkeys) kept in
Indigenous chicken constitutes 80% of the 120 million poultry type raised in
the rural areas in Nigeria (RIM, 1992). They are self
reliant and hardy birds with the capacity to withstand harsh weather condition
and adaptation to adverse environment. They are known to possess qualities such
as the ability to hatch on their own, brood and scavenge for major parts of
their food and possess appreciated immunity from endemic diseases. Their products
are preferred by the majority of Nigerian because of the pigmentation, taste,
leanness and suitability for special dishes (Horst, 1989).
Their outputs (egg and meat) are readily available to villagers and people in
urban semi urban areas thus serves as a good source of protein in their diet,
in the same vein, they serve as good source of income.
The indigenous poultry species represent valuable resources for livestock development
because their extensive genetic diversity allows for rearing of poultry under
varied environmental conditions, providing a range of products and functions.
Thus, great genetic resources embedded in the indigenous poultry await full
exploitation that will provide basis for genetic improvement and diversification
to produce breeds that are adapted to local conditions for the benefit of farmers
in developing countries (Horst, 1988; Sonaiya
et al., 1999).
Though poultry breeding in Nigeria started in 1985 at the National Animal Production
Research Institute, Zaria (Adebambo, 1992), reports
have it that research on the local chicken had started earlier with comprehensive
information about the local fowl. The local chicken of Nigeria is small in size
and grows slowly. There have been reports on the characterisation of the local
chicken in Nigeria and its potential for egg and meat production (Nwosu,
1979; Adebambo, 2005).
In Nigeria, indigenous chickens were characterized along genetic lines of feather
and plumage colour (such as normal or frizzled feathered), body structure (such
as naked neck, dwarf types and colour variants (such as black, white, brown,
mottled etc.). The frequency distribution of the normal feathered chicken was
about 91.8% while that of frizzled and naked neck were 5.2 and 3.0% respectively
in Bayelsa State of Nigeria (Ajayi and Agaviezor, 2009).
Classification has also been on the basis of location. There are various ecotypes
of the local chicken in the different agro ecological zones in Nigeria as reported
by different authors. Most of the classification by the different agro ecological
zones considered mainly the normal feathered indigenous chicken because they
are the most prominent whereas the naked neck and frizzled feathered are rare
and almost becoming endangered and the gene pool they represent may be lost
if not characterized and conserved. For instance, Olori (1992)
noted two ecotypes characterized as forest and savannah or Yoruba and Fulani
ecotypes, respectively Nwosu (1979) identified three
main strains in ecotype named Nsukka, Owerri and Awgu types at the South Eastern
states of Nigeria (Hill and Modebe, 1961) and Oluyemi
et al. (1982) also reported variation in many traits of the indigenous
chicken from the Southern region of Nigeria which they found to be different
from those of other parts of the country. It was agreed by all these researcher
that the Nigerian chicken is a light breed, often with single comb and that
black and brown plumage, laced with various colours such as mottling are common
(Adebambo, 2005). Recent works revealed that the different
ecotypes can be grouped into two major categories on the basis of body size
and body weight as heavy ecotype and light ecotype (Momoh
et al., 2007). The heavy ecotype (also referred to as Fulani ecotype)
is found in the dry Savannahs (Guinea and Sahel Savannah), Montane regions and
cattle Kraals of the North and weigh about 0.9-2.5 kg at maturity. The light
ecotype are those chicken types from the Swamp, Rainforest and Derived Savannah
agro-ecological zones whose mature body weight ranges between 0.68-1.5 kg.
This review aim at describing the characteristics of the Nigerian ecotype chickens, the effect of the major genes and possibilities for genetic improvement.
Genetic Background of Nigerian Indigenous Chicken
Certain major genes have been found to be relevant to the indigenous breeds
in their tropical production environment which is characterized by stress factor
(Horst, 1989; Mathur and Horst,
1990). The feather distribution gene, naked gene (Na) and the feather structure
gene, frizzle (F) are among these major genes. Major genes are economically
interesting in modern breeding systems as they act as sex marker genes and disease
resistant factors (e.g., avian leucosis). These genes cause a reduction in tropical
heat stress by improving the breed's ability for convection, resulting in improved
feed conversion and better performance. Horst (1989)
further stated that the Na and F gene confer superiority in some production
characters in the tropics. Horst (1988) and Mathur
and Horst (1990) showed that individuals with F and Na genes both singly
and in combination were superior to those individuals with normal feathering
for egg number, egg mass/weight and forty-week body weight in tropical environments
According to Ibe (1993), naked neck and the frizzed
genes are associated with earlier sexual maturity in a tropical environment.
Molecular Basis of Nigerian Indigenous Chickens
Nigeria is endowed with varied ecological zones and possesses diverse animal
genetic resources of the local breeds. These local breeds contain genes and
alleles pertinent to their adaptation to a particular environments and local
breeding goals (Romanov et al., 1996). Indigenous
chickens in Nigeria are becoming seriously endangered owing to the high rate
of genetic erosion resulting from diseases and predation. Attempt must be made
so that these adaptive features of the local stocks will not be eroded before
they are characterized and conserved. Little has been done on the molecular
characterization of the indigenous chicken in Nigeria. Adebambo
et al. (2009) found no significant differences in genetic distance
of indigenous chicken from three populations (Southwest, Northwest and Northeast
ecological zones) of Nigeria. They concluded that these chicken populations
exhibited genetic homogeneity resulting from intermixes of germplasm in Nigeria
as the country allows free flow of human and animal traffic. Molecular markers
have played a leading role in characterization of diversity which provides relatively
rapid and cheap assays in the absence of quality phenotypic measures (Toro
et al., 2006). As a result the classification of genetic resources
based on geographical location needs to be supported by molecular data to provide
unbiased estimates of genetic diversity (Pimm and Lawton,
1998) for the purpose of genetic resource conservation and utilization.
Characterization includes a clear definition of the genetic attributes of an
animal species or breed, which has a unique identity and the environment to
which the species or breed populations are adapted (FAO, 1984).
The genetic distinctiveness of an animal forms the basis for distinguishing
it among different animal genetic resources and for assessing the available
diversity (FAO, 1984).
Productive and Reproductive Performance of the Local Chicken
Although, the Nigerian indigenous chickens possess small body size and grows
slowly, it has been concluded that they reach point of inflection earlier than
the exotic (Nwosu et al., 1980). Body size of
an individual is also determined by its rate of growth (Ibe,
1993). Olawunmi et al. (2008) found that
the Fulani ecotype chicken was bigger in size than the Yoruba ecotype chicken
1.76±0.4 and 0.79±0.21 kg for Fulani and Yoruba ecotypes respectively.
Indigenous male chicken was also bigger in size than their female counterparts
1.5±0.06 kg versus 1.29±0.04 kg, respectively (Ajayi
and Agaviezor, 2009). Major genes have been reported to show pronounced
effect on the performance of indigenous chicken in the tropics (Ibe,
1992). It has also been reported that the frizzled feathered and naked neck
genes conferred better feed conversion on these genotypes when compared to their
normal-feathered counterpart (Horst, 1997; Gunn,
2008). Table 1 shows the growth rate at various ages for
the indigenous pure bred chicken of various ecotypes in Nigeria and its crossbred
counterpart with exotic strains.
|| Growth rate of pure indigenous, exotic and their crossbred
It has been established that differences existed between these ecotypes from
morphological point of view (Olawunmi et al., 2008).
Crossbreeding indigenous chicken with exotic also improved body weight greatly
at 12 weeks (Adebambo, 2005).
Growth rate and egg production under conventional system of rearing in the
villages are very low. This is generally due to the insufficient feed supply and
problem of diseases and social behavior (Ibe, 1998). Egg
production when raised extensively is about 40 eggs year-1 (Ikeobi
et al., 1996) whereas under improved conditions, egg yields of local
birds may be doubled (Nwosu, 1979). The age at sexual
maturity ranged between 133-169 days under scavenging condition whereas in cage
system, it increases to about 189 days (Gunn, 2008). This
report contradicts the findings of Islam and Nishibori (2009)
for indigenous chicken of Bangladesh. Adedokun and Sonaiya
(2001) also reported mean age at first egg of 157±3.7, 160±3.8
and 165±3.7, respectively for hens from Derived savannah, Guinea savannah
and Rain forest zone of Nigeria (Table 2). Ibe
(1992), also noted that frizzled and naked neck individuals in the tropical
environment attaining earlier maturity than normal-feathering birds. The difference
in age of pullet in attainment of sexual maturity was attributed to system of
management (Tadelle et al., 2003) and productive
trait (Gunn, 2008). Although, egg weight was higher for
the heavy ecotype than the light ecotype chicken (Fayeye et
al., 2006; Momoh et al., 2007), the latter
lays more egg than the former. Adedokun and Sonaiya (2001)
in their investigation reported that birds that attained early sexual maturity
end egg laying production earlier than those late sexual maturity ones. More feed
was also utilized in producing a dozen eggs by the indigenous chicken than the
crossbred chicken (Table 2).
Fertility and Hatchability of Eggs
Fertile eggs from indigenous chickens in Nigeria are comparable in fertility
and hatchability with indigenous chickens from other regions of the world under
local conditions. Fertility and hatchability were 76 and 48% respectively for
Fulani ecotype chicken which was within the range of 83.0-92.7 and 52.4-87.0%
reported for indigenous full feathered Bangladesh chickens (Islam
and Nishibori, 2009).
|| Egg production performance of Nigerian indigenous chicken
ecotypes, exotic and their crossbreds
|| Fertility and hatchability of eggs
Although, the fertility of the normal feathered (nana ff), naked neck (NaNa)
and the frizzled feathered chickens were just a little above average (Table
3), they all have high hatchability between 72-93.1% except the normal feathered
birds with about 45% hatchability (Ajayi et al.,
Meat Quality and Consumers Preference for the Indigenous Chicken
Scanty reports abound in literature on the meat quality characteristics
of the Nigerian indigenous chickens. Major genes have significant effect on
carcass and organ weight at 20 weeks of age. Naked neck had higher breast percent
than both frizzled and normal feathered birds (Gunn, 2008)
but the frizzled and naked neck excelled in weight of other cut parts than the
normal feathered chicken. Recent studies on incorporation of naked neck into
broiler birds showed the superiority of the same over the normal feathered chicken
in terms of growth rate, feed efficiency, dressing percentage and other important
broiler traits (Singh et al., 1996; Mathur
and Horst, 1990; Ibe, 1993; Yunis
and Cahaner, 1999; Ikeobi et al., 1996).
Indigenous chicken meat and egg are preferred by majority of the rural dwellers
mainly because of their toughness, pigmentation, taste, leanness and suitability
for special dishes (Horst, 1991; Islam,
2000). Meat and eggs from indigenous chicken are also of moderate prices
compared to products from commercial birds (Horst, 1989;
|| Heritability of body weight in chicken
Estimate of Heritability of Growth Traits in Indigenous Chicken
For a given trait, heritability is the amount of the superiority of the
parents above their contemporaries, which on the average is passed on to the
offspring. In order to establish breeding programme it is necessary to count
with heritability estimates of traits of economic importance and genetic association
between them. This is because the degree of heritability allows one to estimate
the amount of improvement by selection and genetic association that can dictate
method of selection. There is little report in literature of estimate of heritability
of body weight of Nigerian local fowls at various ages. Oluyemi
and Oyenuga (1974) reported 12th week body weight heritability of 0.32 (h2S),
0.29 (h2d) and 0.31 (h2s+d). Nwosu
et al. (1984) obtained estimates of heritability for 4 and 8 weeks
as 0.36, 0.38 and 0.37, 0.32, 0.36 and 0.34 for sire, dam and combined components,
respectively estimates of heritability are necessary to predict response to
direct or indirect selection.
Using three breeding groups, pure light and heavy ecotype chickens and a crossbred
between heavy and light ecotype chickens, Ndofor et al.
(2006) reported that heritability estimate between 4-20 weeks for light
chicken was 0.40±0.44, while 0.37±0.09 and 0.29±0.57 were
recorded for heavy and main cross chickens respectively. They concluded that
appreciable improvement in the trait could be achieved if the pure parents are
individually selected at the age of 12 or 16 weeks. Momoh
and Nwosu (2008) also reported heritability estimates of body weight of
0.43 and 0.30 for heavy ecotype chicken at 8 and 20 weeks respectively (Table
4). There is an indication that the heavy chicken ecotype may possess dual
potential to be selected as meat type or egg-type bird because 8 weeks and 20
weeks of age are broiler and layer ages, respectively. The moderate to high
heritabilities indicate that response to selection at the 8th or
20th week could be rapid (Momoh and Nwosu, 2008).
The Nigerian indigenous chickens have the capability of being developed into
meat-type and egg-type birds.
Indigenous Chickens and Future Breed Development
The indigenous breeds represent a huge reservoir of chicken genome. Their
continued use in a low input small scale village production systems serve as
a cheap in-situ conservation technique that needs to be encouraged and supported
(Olori, 2009). The frizzling and the naked genes in
particular have been described as adaptability genes acting as sex marker and
disease resistant factor (Islam and Nishibori, 2009).
Indigenous chickens need to be maintained for the purpose of conserving the
wide gene pool that they represent into the future. In this form, they are of
the highest value especially in this era of genomics research and enhanced potential
for the development of new improved breeds for the future. This will be achieved
largely through the increased application of molecular genetics in poultry (Fulton,
2008). There is a wide gap between indigenous chickens and exotic breeds
raise udder harsh environmental conditions. Crossbreeding indigenous chicken
with exotic breed will go a long way in improving the performance of the indigenous
without necessarily losing its adaptive features as their desirable genes are
conserved (e.g., for disease resistance). This will enhance better productivity
of these indigenous stocks and also help in planning sustainable breeding programme
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