IMPROVEMENT IN EGG PRODUCTION TRAITS IN THE LIGHT LOCAL CHICKEN ECOTYPE USING A SELECTION INDEX

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TABLE OF CONTENT

Title page        …         …        …        …        …        …        …        …        i

Certification    …            …        …        …        …        …        …        …        ii

Dedication           …        …        …        …        …        …        …        …        iii

Acknowledgement             …        …        …        …        …        …        …        iv

Table of contents            …        …        …        …        …        …        …        v-vi

List of Tables  …         …        …        …        …        …        …        …        vii

List of Figures …           …        …        …        …        …        …        …        vii

Abstract          …          …        …        …        …        …        …        …        ix

CHAPTER ONE

INTRODUCTION    …        …       …        …        …        …        …        1-4

            1.1       Background of Study …          …        …        …        …        1

            1.2       Statement of Problem …              …        …        …        …        2

            1.3       Objectives of the Study …          …        …        …        …        3

            1.4       Justification     …               …        …        …        …        …        3

CHAPTER TWO    

LITERATURE REVIEW   …             …        …        …        …        …        5-16

2.1       Egg Production in Chicken     …        …        …        …        …        …        5

            2.1.1    Factors Influencing egg Production   …        …        …        …        5

            2.2       Principles of Selection…      …        …        …        …        5

2.3       Selection for Body Weight and Egg Production Traits in Chicken   …        9-13

  •       Use of Selection Index in Chicken        …        …        …        13-14
    • Basis for Short-Term Egg selection in Poultry           …        14

2.6       The Nigerian Local Chicken         …        …        …        …        14-16

CHAPTER THREE

MATERIALS AND METHOD           …        …        …        …        …        17-25

3.1       Experimental Site        …        …        …        …        …        …        …        17

3.2       Experimental Animals …        …        …        …        …        …        17

3.3       Foundation Stock       …        …        …        …        …        …        …        17

3.4       Management of birds  …        …        …        …        …        …        …        18

3.5       Maintenance of a control population         …        …        …        20

3.6       Data Collection           …        …        …        …        …        …        …        20

            3.7       Data Analysis      …        …        …        …        …        …        20

                        3.7.1    Evaluating the Performance Characteristics  …         20

                        3.7.2    Estimation of Genetic Parameters           …        …        21

                        3.7.3    Measurement of Selection Applied       …        …        23

            3.8       Construction of Selection Index using the Selection Criteria   24

CHAPTER FOUR

RESULTS AND DISCUSSION           …        …        …        …        …        27-48

            4.0       Results              …        …        …        …        …             27-41

            4.1       Mean Performance of the Various Egg Production Traits Studied    …        27-31

                        4.1.1    Age at First Egg            …        …        …        …        27

                        4.1.2    Body Weight at First Egg         …        …        …        27

                        4.1.3    Weight of First Egg          …        …        …        …        27

                        4.1.4    Average Egg Weight     …        …        …        …        27

                        4.1.5    Total Egg Number          …        …        …        …        28

            4.2       Estimates of Genetic Parameters of the Selection Criterion Traits     …        32-36

                         4.2.1   Heritability Estimates       …        …        …        …        32

                        4.2.2    Phenotypic and Genetic Correlation between Traits  35

            4.3      Measurement of Selection Applied        …        …        …        37-40

            4.3.1    Selection Differential, Selection Intensity and Selection Response   …        37      

  4.4       Selection Indexes used for the Selection of LLCE Hens   40       

            4.5       Discussions     …        …        …        …        …        …        41-47  

                        4.5.1    Mean Performance of the Various Egg Production Traits Studied    41

4.5.2    Heritability Estimates …         …        …        …        43                    4.5.3   Phenotypic and Genetic Correlation between Traits  …        …        46

4.5.4    Measurement of Selection Applied    …        …        …        …        46

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS      …        …        …        49-51

REFERENCES              …        …        …        …        …        …        …        52-65

APPENDICES           …        …        …        …        …        …        …        66-88

LIST OF TABLES

                                                                                                                                              Page

Table 1:           Population Size, Effective Population Size and Change in Inbreeding Coefficient over the Three Generations of Selection ……        18

Table 2:           Proximate Composition of Commercial Diets            …        19

Table 3:           Vaccination Schedule for the Birds     …        …        …        19

Table 4:           Analysis of variance table      …        …        …        …        21

Table 5:           Analysis of Covariance table  …        …        …        …        22

Table 6:           Mean (±SE) by population for traits studied  …        …        28

Table 7:           Mean (± SE) of the Traits Performance by Generation and Population1      …        …        …        …        …        …        …        …        29

Table 8:           Mean (± SE) performance and phenotypic regression coefficients in selected and control populations      …        …        …        30

Table 9:           Heritability (± SE) estimates of the three selection criteria by generation and population of the LLCEa        …        …        …        …        34

Table 10:   Genetic (rg), Phenotypic (rp) and Environmental (re) correlation by generation and population of LLCE         …        36

Table 11:         Selection differential, Selection Intensity, Expected Direct Response,

Estimated Realized Response and Estimated Index Response over three generationsa        …        …        …        …        …        …        …        38

Table 12:         Estimated Index Score (Selected Is and Whole Iμ population), Selection Intensity Factor (ῑ), Heritability of Index (h2) Genetic Gain in Aggregate(ΔH) and Correlation of Index and Aggregate Genotype rIH, Expected Annual Genetic Response (ΔGAi) and Generation Interval Li  41

LIST OF FIGURES

                                                                                                                                           Page

Figure 1:          Phenotypic trend of body weight at first egg in 3 generation selection         31

Figure 2:          Phenotypic trend of egg weight in 3 generation selection      …        …        31

Figure 3:          Phenotypic trend of egg number in 3 generation selection     …        …        32

Figure 4:          Regression of BWFE response on generation number           …        …        39

Figure 5:          Regression of AEW response on generation number …        …        …        40

Figure 6:          Regression of TEN response on generation number…           …        …        40       

ABSTRACT

Fifty hens and five cocks from a random mating population of light local chicken ecotype (LLCE) were mated and the fertile eggs hatched to obtain the parent generation (G0) used for this study aimed at improving egg production traits in the LLCE using a selection index.  The hens were monitored for short-term (90-days from first day of lay) egg production traits namely: Body Weight at First Egg (BWFE), Average Egg Weight (AEW) and Total Egg Number (TEN).  Data obtained were subjected to statistical analysis using SPSS (2001) and paternal half-sib model with Harvey (1990) to estimate descriptive statistics and genetic parameters respectively.  These were employed in constructing the selection index.  Selection for all the selection criteria (BWFE, AEW and TEN) was in the positive direction.  Selected parents were mated to produce next generations – G1 and G2.  Selection differentials, selection intensities and genetic response due to selection were also estimated.  A control population which spanned for three generations (each generation had its own control population) was used to monitor environmental changes and to estimate the genetic changes due to selection.  There were significant increases (P<0.05) in BWFE, AEW, and TEN in the selected populations over the three generations of study such significant increases (P<0.05) were not observed in the control population.  Heritability estimates for all traits in all generations and populations were moderate to high.  The heritability of the index was also moderate.  Such moderate to high heritability estimates indicate high additive genetic variances, implying that these traits were most passed on from the parents to their offspring.  Low to high positive genetic and phenotypic correlations was observed between BWFE and AEW in all populations of study.  The genetic correlation and phenotypic correlation between BWFE and EN, and between AEW and EN, was moderate to highly negative for all generations and populations of study.  A positive genetic correlation was observed between AEW and TEN in G2 of the selected population.  A cumulative selection differential of 269.38g, 1.58g and 3.88 eggs were obtained for BWFE, AEW and TEN respectively.  Selection response for traits increased over the generations in a fairly linear manner.  Realized response per generation was estimated to be 94.22g, 0.84g and 4.85eggs for BWFE, AEW and TEN respectively.  It is evident that the simultaneous inclusion of BWFE, AEW, and TEN in a selection index generally improved the performance of selected birds over the generations in the Light Local Chicken Ecotype.

CHAPTER ONE

INTRODUCTION

1.1       BACKGROUND OF STUDY

The report of the 4th Food and Agriculture Organization (1973) expert consultation on Animal Genetic Resources presented two important objections concerning the endeavour to improve and conserve the local chicken.  The first was as to whether the local strains still possess genes, which are useful to the vastly improved exotic strains given the centuries of genetic screening, which the latter have undergone.  The second objection pointed to the fact that the process of further screening of the local chicken will be long, laborious and very expensive.  However, the results of recent research using local chicken (Ikeobi and Peters, 1996; Ayorinde et al., 2001; Udeh and Omeje, 2001) indicate that the local chicken is a repository of advantageous genes.  Secondly, with molecular genetic techniques, genetic improvement of the local chicken is fast and less expensive.  Incidentally, third world countries, which established breeding programmes based on the dilution of indigenous germplasm by extensive crossbreeding programme, suffered failures. Those failed efforts have made livestock breeders aware of the importance of indigenous breeds in overall food production systems – because of their adaptation to the environmental stress of the tropics.

In spite of the large number of livestock and poultry in the nation, the animal protein intake per caput per day still falls below the minimum requirement level recommended by UN/FAO (Ayodele and Ajani, 1999).  This has been traced to the low production of animals, which could be due to genetic and/or environmental constraints.  The above underscores the need to improve the level of animal protein production in Nigeria.  Of greater importance is the improvement of the poultry sector since it has a number of advantages – including short generation interval, and production of large number of offspring, due to its peculiar reproductive traits (Ibe, 2001).  Furthermore, poultry meat is generally accepted by all religions and societies.

In many countries the development of agriculture and breeding programmes has resulted in serious changes in poultry breeding stocks during the last decades.  The establishment of breeding institutions has led to a pronounced supra-regional propagation of certain chicken breeds due to improvements in performance.  As a consequence the local breeds have decreased continuously to the same extent as the preferred high performance breeds have expanded.  For instance, it was in a bid to satisfy the need for increased production and profitability in intensive production systems to meet the increase in demand for animal protein by the populace that new high yielding and fast growing poultry breeds were introduced into the existing poultry production systems in Nigeria since the late 1950’s (Obioha, 1992).  Incidentally, such introduction has resulted in non-integration of the local breeds considered as ‘low producers’ into large-scale poultry production. 

Nigeria has rich chicken genetic resources.  A good number of workers have documented the characteristics of the local chicken, in terms of morphological, physiological, behavioral and production attributes.  Nwosu (1990) gave a review of these.  Ibe (1990a, b) identified some major genes of tropical relevance in Nigerian local chicken populations. Perhaps, the most distinguishing feature for physical characterization at present is the body weight of the local chicken found in the various ecological zones of the country (Olori and Soniaya 1992).  Observations have shown that local chicken found within the swampy rainforest and guinea savanna regions are lighter in weight than those found within the highlands and sudan savanna regions (Nwosu, 1979).  Such differences in body weight can be used to categorize the local chicken broadly as Light Ecotype – those with lighter weight and Heavy Ecotype – those with heavier weight.

Research data on the local chicken in the past 50 years (Hill, 1954; Oluyemi, 1979; Omeje and Nwosu, 1982; Nwosu, 1987; Udeh and Omeje, 2001) indicate that the Nigerian local chicken has useful genetic attributes that can be harnessed in crossbreeding programmes for the development of egg-type and meat-type chickens.  However, there exist limitations to the realization of total heterosis in such crosses with the exotic because – the local chicken is unpedigreed, unselected and unsegregated (Omeje, 1985) hence, unlike the exotics the local chicken cannot be considered a purebred.  Furthermore, crossbreds from purebred parents show heterosis to the extent that their gene frequencies differ unlike hybrids from similar lines that manifest total heterosis, (Pirchner, 1983).

In order to incorporate the local chicken as a parent breed to produce strains of chicken that are adaptable to the local environment as well as achieving the much desired goal of making Nigeria self-sufficient in the sourcing of poultry breeding stock and boosting her poultry industry, there is need for selective breeding.  The practice of selective breeding among local strains has been found advantageous (El-Issawi, 1975).  The concept underlying selective breeding is variation.  For within a group of individuals there exist allelic variations that affect the outcomes of quantitative traits such as growth, egg production and egg quality traits.

1.2       STATEMENT OF PROBLEM

IMPROVEMENT IN EGG PRODUCTION TRAITS IN THE LIGHT LOCAL CHICKEN ECOTYPE USING A SELECTION INDEX