ABSTRACT
Two experiments were conducted in this study to evaluate the performance of main and reciprocal F1 and F2 crossbred chickens bearing normal feather, naked neck and frizzle feather genes in the humid tropics. In experiment 1, a base population of 90 adult chickens comprising 45 local strains (normal feathered chickens, frizzle and naked necked) and 45 exotic broiler breeder (Anak) strain were used at a mating ratio of 5:40 and 5:40, respectively for the experiment in a Randomized Complete Block Design. The main cross constituted the mating of the exotic cocks (Anak male) to the local hens (Normal, frizzle and naked neck). The reciprocal cross consisted of the reverse mating involving the mating of the local cock (Normal, frizzle and naked neck) to the exotic broiler breeder hens. Data collected were subjected to Analysis of Variance technique. Results of growth performance revealed that the reciprocal F1 hybrids were significantly (P<0.05) heavier in body weight than their main cross counterpart throughout the period of the study. Average daily feed intake were also higher (P<0.05) in the reciprocal F1 crosses and also the best feed conversion ratios. Brooding and rearing mortalities were significantly higher (P<0.05) in both the main and reciprocal crosses of naked neck (E x Na and Na x E) in F1. Sexual dimorphism was observed in the body weight and Linear body measurement (LBM) with the male weighing heavier than females at all stages of the cockerels and pullets. The frizzle males and females were superior in body weight and most LBM at 18 weeks. Body weight at first age, egg at first egg, average weight of egg at first lay and short term egg number at 90 days were significantly (P<0.05) better in the reciprocal crosses with the frizzle chicken having the highest body weight at first lay (2000g), egg weight (47.55g) and egg number (41.02). The reciprocal cross of frizzle also had the lowest number days for first egg (146days). The egg quality traits were also significantly (P<0.05) higher in the reciprocal F1crosses. The correlation values between body weight at first egg and age at first egg in the genetic groups were all positive and ranged from low to high (0.287 – 0.996) with the exception of F x E where a highly significant (P<0.01) negative correlation between these traits were found. A significant negative correlation (r = -0.999) was also found between body weight at first egg and egg number at 90 days in E x F hybrid. The live weight, dress weight, dressing percentage, breast cut, back cut, thigh, wings and shank of the reciprocal crosses were significantly higher (P<0.05) than in the main crosses. Among the reciprocal crosses, F x Ehad the highest live weight and shank length, followed by Na x E. The Na x E was significantly higher in dress weight, dressing percentage, breast cut, back cut and thigh, followed by F x E. Significant differences (P<0.05) were seen in heart, proventriculus, lungs and kidney, where the reciprocal crosses where significantly different (P<0.05) from the main crosses. The reciprocal crosses were significantly higher (P<0.05) than the main crosses in heart, proventriculus, lungs and kidney. The reciprocal F2 backcrossed chickens [E x (NF x E), E x (Na x E) and E x (F x E)] were superior to their main cross counterparts in body weight throughout the study periods. They also had better FCR and higher LBM when compared to their main cross F2 backcross counterparts. The reciprocal crosses were also superior in egg production parameters with the frizzle having the highest body weight at first egg and least age to attain sexual maturity in both main and reciprocal crosses. However, the normal feathered had higher number of eggs lay. The reciprocal F2 backcrosses also were superior in egg qualities. The experiments showed clear evidence of maternal influence in the expression of growth and in egg production traits. The reciprocal crosses were significantly higher (P<0.05) than the main crosses in carcass characteristics. From experiment 1 and 2, it was clear that the reciprocal crosses produced off springs with superior growth, egg production and egg quality characteristics traits. It was concluded that backcrossing the F individuals to the exotic broiler breeder cocks increased the genetic profile of the backcross lines resulting in enhanced growth performance of progenies. Crossbreeding of exotic and local chicken varieties generated progenies that had higher genetic potentials for growth relative to the local strains and better adaptability relative to the exotic breed. It is therefore concluded that reciprocal crossbreeding should be adopted in other to achieve rapid improvements in the traits studied. Frizzle gene was superior in body weight and egg production and egg quality traits followed by naked neck gene, which showed improvement especially in egg quality traits.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List
of Tables ix
Abstract x
CHAPTER 1: INTRODUCTION
1.1 Background Information 1
1.2 Objective of the Study 3
1.3 Problem Statement 3
1.4 Justification of the Study 4
CHAPTER 2: LITERATURE
REVIEW
2.1 Classification of the local Chickens 6
2.2 Local
Chickens: Breeding Systems, Characteristics and Productivity 7
2.3 Major
Genes within the Local Chicken Biome 11
2.4 Frizzle
Gene 12
2.5 The Effects of Frizzle Gene on Productivity 13
2.6 Feed Intake and Feed Conversion in Local and Crossbred
Chickens 17
2.7 Naked Neck Gene 18
2.8 The Effects of Naked Neck Gene on Productivity 19
2.9 Crossbreeding as an Option for Genetic
Improvement 26
2.10 Body Weight and Linear Body Measurements 29
2.11 Relationship
and Association Studies in Certain Economic Traits in Chickens 31
2.12 Egg Quality Characteristics of Chickens 33
2.13 Growth Performance Evaluation in Naked Neck,
Frizzle and
Normal
Feathered Meat-Type Chickens 36
2.14 Comparative
Egg Production Performance of the Naked Neck, Frizzle
and Normal Feathered Birds 40
CHAPTER 3: MATERIALS AND
METHODS
3.1
Study Location 44
3.2
Experiment 1 44
3.2.1
Procurement and management of parent population 44
3.2.2
Mating scheme for the production of F1 crossbred chicks 46
3.2.3
Management of F1 chicks 48
3.2.4
Experimental design and statistical analysis 53
3.3 Experiment II 54
3.3.1
Location and duration of study 54
3.3.2
Management of parent population 54
3.3.3
Mating scheme for the production of F2 backcross chicks 56
3.3.4 Management of F2 backcross chicks 57
3.3.5 Experimental design and statistical analysis 60
CHAPTER 4: RESULTS AND
DISCUSSION
4.1 Growth
Performance of F1Hybrid Chickens 61
4.1.1
Mean body weight (g) of F1
crossbred normal feathered, naked neck
and frizzle chickens 63
4.1.2 Average daily feed intake (ADFI) feed
conversion ratio of F1 hybrid chickens 63
4.1.3 Linear body measurement (LBM) of F1 hybrid
chickens 66
4.1.4 Brooding, rearing and laying mortality
rates in the F1 hybrid chickens 68
4.1.5 Egg production of F1 hybrid
chickens 70
4.1.6 External and internal egg characteristics of
F1 hybrid chickens 71
4.1.7 Correlation between body weight at first egg
and egg production
parameters in F1 hybrid
chickens 74
4.1.8 Correlation between egg weight and egg
quality traits in F1 hybrid chickens 75
4.1.9 Carcass characteristics of F1 hybrid
chickens 77
4.1.10 Organ proportion of F1 hybrid
chickens 80
4.2 Growth Performance of F2 Backcross
Chickens 81
4.2.2 Average Daily Feed Intake (ADFI) and feed
conversion ratio of F2backcross 83
4.2.3 Linear body measurement (LBM) in F2 backcross 85
4.2.4 Brooding, rearing and laying mortality in F2
backcross Chickens 87
4.2.5 Egg production characteristics of F2 backcross
chickens 88
4.2.6
External and internal egg characteristics of F2 backcross
chickens 91
4.2.7 Correlation between body weight at first egg
and Egg production
parameters
in F2 backcross chickens 93
4.2.8 Correlation between egg weight at 60 days of
lay and egg quality
traits
in F2 backcross chickens 94
4.2.9 Carcass
characteristics of F2 backcross chickens 95
4.2.10 Organ
proportion of F2 backcross chickens 97
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1
Experiment I 98
5.2
Experiment II 99
5.4
Recommendation 99
References 101
LIST OF TABLES
4.1:
Mean Body Weight (g) of F1 Crossbred Normal feathered, Naked neck
and
Frizzle Chickens (sex
combined) 63
4.2:
Average Daily Feed Intake (ADFI) of F1 Crossbred Normal feathered,
Naked neck and Frizzle Chickens 64
4.3:
Feed Conversion Ratio (FCR) of F1 Crossbred Normal feathered, Naked
neck and Frizzle Chickens 66
4.4:
Body Weight and Linear Body Measurements (LBM) of Cockerels in
Various Genetic Groups at 18
Weeks 67
4.5:
Body Weight and Linear Body Measurements (LBM) of Pullets in Various
Genetic Groups at 18 Weeks 68
4.6:
Brooding, Rearing and Laying Mortality in F1 Crossbred Normal
feathered,
Naked neck and Frizzle
Chickens 69
4.7:
Egg Production Characteristics of F1 Crossbred Normal feathered,
Naked
neck and Frizzle Chickens 71
4.8:
External and Internal Egg Characteristics of F1 Crossbred Normal
feathered,
Naked neck and Frizzle
Chickens 72
4.9:
Correlation between Body Weight at First Egg and Egg Production
Parameters in F1 Crossbred
Chickens 75
4.10:
Correlation between Egg weight at 60 days of lay and Egg Quality
Traits in F1 Hybrid
Chickens 77
4.11:
Carcass Characteristics of F1 hybrid chickens 79
4.12:
Organ Proportion of F1 hybrid chickens 80
4.13:
Mean Body Weight (g) of F2 Backcross Normal feathered, Naked
neck and Frizzle Chickens 82
4.14:
Average Daily Feed Intake (ADFI) of F2 Backcross Normal feathered,
Naked neck and Frizzle
Chickens 84
4.15:
Feed conversion ratio (FCR) of F2 backcross normal feathered, Naked
neck
and Frizzle Chickens 85
4.16:
Body weight and linear body measurements (LBM) of Cockerels in various
genetic groups at 12 weeks 86
4.17:
Body weight and linear body measurements (LBM) of Pullets in various genetic
groups at 12 Weeks 87
4.18:
Brooding, Rearing and Laying Mortality in F2 Backcross Chickens 88
4.19:
Egg production characteristics of F2 backcross chickens 90
4.20:
External and internal egg characteristics of F2 backcross chickens 92
4.21:
Correlation between body weight at first egg and Egg production parameters in F2
backcross chickens 93
4.22:
Correlation between Egg weight at 60 days of lay and Egg quality traits in F2
Backcross
Chickens 95
4.23: Carcass Characteristics of F2
Backcross Chickens 96
4.24:
Organ proportion of F2 backcross chickens 97
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
INFORMATION
Poultry
production in Nigeria amounts up to 454 billion tonnes of meat and 3.8 million
eggs per yearwith a standing population of about 180 million birds (ASL 2050,
2018). Local chickens, still represent an appropriate system for supplying the
fast-growing human population with high-quality protein and providing
additional income (Gueye, 2003; Alabi et
al., 2006) especially in the rural economy.
The
Nigerian local chickens are typified by their small adult size and laying of
small sized eggs when compared to improved commercial broiler or layer birds
respectively (Pedersen, 2002; Gondwe, 2004). They are made of heterogenous
individuals that have variable performance, thus necessitating the need for
their genetic diversity to be exploited for genetic improvement and development
(Msoffe et al., 2001; Fayeye et al., 2005). The genetic erosion
of these local breeds may lead to the loss of valuable genetic variability in specific
characteristics (Ladokun et al., 2008). The indigenous chickens of
Nigeria are not yet classified into breeds (Ibe, 2001) but there exist strains
or inbred lines within the native chicken populations which possess major genes
that have direct and indirect effect on production and quantitative trait loci
(Fayeye et al., 2006). Among these is the plumage reducing genes which
include the naked-neck (Na) and Frizzle (F) genes with associated
thermoregulatory roles (Peters, 2000).
Temperature
is the most important environmental factor affecting poultry production and
elevated temperatures inevitably lead to reduced productive performance in both
broilers and laying hens, particularly when accompanied by high relative
humidity (Mahrous et al., 2003; Chen et al., 2009; Fathi et al., 2013). Genetic
approaches that aid in reducing or altering the extent of plumage cover by
taking advantages of a number of genes, such as frizzled (Galal and Fathi,
2001; Nwachukwu et al., 2006; Mahrous
et al., 2003; 2008) and naked neck
(Galal and Fathi, 2002; Mahrous et al.,
2003; 2008) have been extensively studied due to their role in heat tolerance.
It
is imperative to utilize Nigerian local chickens as part of parent stock
development for better adaptability (Olawoyin 2006). Several researchers have
advocated the use of the naked-neck and frizzling genes singly or in
combination to develop stocks specifically for the hot and humid environments
(Horst, 1988). Apparently, the reason for accentuating the use of the Na and F genes
may be related to the relative high T3 (triiodothyronine) concentration
(Decuypere et al., 1993) and lower
feather mass which increases the effective surface for heat dissipation and
increases the sensible heat loss from the neck of Na strains (Yahav et al., 1998) and reduction in feather
coverage and heat insulation by the frizzle gene by curling for better heat
tolerance (Fathi et al., 2013).More
so, reduced feathers spare protein which could have been used to grow feathers
to be channeled productively into egg or meat production (Adomako, 2009).
Fortunately,
many reports have proved that the naked neck and frizzle genes have pleiotropic
effects on several important quantitative productive traits (Galal, 2000; El-
Safty, 2006; Mahrous, 2008). Accordingly, the utilization of naked neck and
frizzle genes in high-ambient temperatures is encouraged, and, in future, will
play an important role in production of layer lines suitable for overcoming
such genotype environment interactions (Thiruvenkadan et al., 2010; Rajkumar et al.,
2011; Mahrous and El-Dlebshany, 2011). Therefore, continuous selection for
faster growth rate in broilers, together with the increasing proportion of
broiler production in tropical and subtropical regions, may accentuate the
importance of the potential use of Na and F genes.
1.2 OBJECTIVE OF THE STUDY
The
main objective of the study is to evaluate the performance of F1 and
F2 crossbred chickens bearing normal feather, naked neck and frizzle
genes in the humid tropics.
The
specific objectives include;
i.
To evaluate the growth
performance and carcass characyteristicsof F1 and F2
backcross progenies of normal feathered, naked neck and frizzle crossbred
chickens.
ii.
To evaluate the
short-term egg production and egg quality characteristics of the two
generations of hybrid chickens produced.
iii.
To determine the nature
of association between bodyweights at first egg (BWFE) and the egg production
and egg quality parameters in the various crosses.
1.3 PROBLEM STATEMENT
Tropical
climates are characterized with high ambient temperature which is known to
negatively affect the growth performance of birds. The per capita consumption
of chicken is still low compared to what obtains in developed countries. The
effect of high ambient temperature is reflected in decreased body weight, body
weight gain, feed efficiency, low egg number, poor egg size and poor carcass
output among others. Tropical regions again contain indigenous chicken strains
which are known to have lower adult size, slow growing, poor hatchability and
lower carcass output but are endowed with potential adaptive features requiring
improvement and exploitation.
1.4 JUSTIFICATION OF THE STUDY
The requirement of
the genetic potentials of the local chicken with thermos-regulating plumage
modifying genes is a veritable option in tropical poultry breeding. The
existence of plumage reducing genes such as frizzle and naked neck genes among
the indigenous stocks has become a game changer in tackling the deleterious effects
of high temperature. These genes control the structure and distribution of
feathers and ultimately results in reduced feathering or plumage thus exposing
more surface area for dissipation of heat. Heat generation in chickens is not
really a misnomer as development of fast growing broilers leads to high heat
generation as a result of increased metabolic rate. The heat generated becomes
a problem when its rate of generation does not equal its rate of loss. The
reduction in feathering in naked neck and frizzle chicken strains spares
protein which would have been used to develop feathers to be channeled to the
growth of meat and egg. Heritability of useful growth traits is
characteristically low in indigenous chickens especially within the current
popular market age of broiler chickens (6-8 weeks of age). Such low
heritability estimates affects genetic improvement and are the results of non
additive gene effects. Crossbreeding using an exotic broiler chicken has
therefore been presented as an indispensable option for developing stocks that
are well adapted, have moderate to high heritable growth and carcass traits as
well as have fast growth rate and result in greater growth performance and
carcass output. Crossbreeding will harness the advantage of complementarities
and heterosis. Finally, plumage reducing genes are known to have pleiotropic
effects. In other words, their positive effect in one trait may result in a
concomitant positive effect in another useful economic trait. Therefore,
continuous selection for faster growth rate in broilers, together with the
increasing proportion of broiler production in tropical and subtropical
regions, may accentuate the importance of the potential use of Na and F genes
singly or in combination.
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