Genetic Change in the Nigerian Heavy Local Chicken Ecotype through Selection for Body Weight and Egg Production Traits

Abstract

The study was carried out to determine the genetic change in the Nigerian heavy local chicken ecotype (NHLCE) through selection for body weight and egg production traits. Progenies (G₀ generation) generated from breeding parents randomly selected from the parent stock of the NHLCE formed the materials for the research.

On hatching, the chicks were grouped according to sire families using colour markers. The chicks were brooded and reared according to standard management practices.

They were fed a starter mash containing 18% crude protein and 2800 Kcal/kgME from 0 – 8 weeks and a growers mash containing 15% crude protein and 2670 Kcal/ kgME from 8 weeks to 20 weeks.

At 20 weeks, all pullets were moved into individual laying cages for short-term (16 weeks) egg production. From then the birds were fed layers mash containing 16.5% crude protein and 2600Kcal/kgME.

Data were collected on body weight, egg weight and egg number. A control population was maintained for each generation and was used to measure environmental effects.

At the end of the 16 weeks egg production period, hens were subjected to selection using a multiple trait selection index incorporating body weight at first egg (BWFE), average egg weight and total egg number.

The relative economic weights of the traits and their heritabilities were used to weight the phenotypic values of each trait in the index.

The index score of each bird became a univariate character, which enabled the hens to be ranked for purposes of selection.

Males were selected based on their individual body weight performances  at 39 weeks of age using mass selection. Selected parents from G₀ generation were used to generate the G₁ generation which in turn yielded the parents of the G₂ generation.

Table Of Contents

Title page         – i

Certification     – ii

Dedication       – iii

Acknowledgement -iv

Abstract              v

Glossary of terms          vi

Table of content    vii

List of table       –   viii

INTRODUCTION – –   1

• Research objectives – –     3
• Problem statement – –       4
• Justification – –       5

LITERATURE REVIEW – –   6

• Characterization of the Nigerian indigenous chicken – –   6
• Variation among the indigenous chickens – –   8
• Egg Production in Chickens – –      8
• Genetic factors influence egg production – – –    9
  • Age at sexual maturity (ASM) – –    9
  • Body weight at sexual maturity (BWSM) – -10
  • Single gene effects – –    10
  • Other genetic components of egg production – –  11
• Environmental factors influencing egg production –   11
  • Nutritional factor – –    11

2.5.2    Diseases           –       11

2.5.3    Temperature (Heat)      –        11

2.5.4  Lighting            –     12

• Genetic improvement in chicken –   12
• Selection strategies – – –        13
• Genetic relationship between traits – –        14
• Economic weights (values) of quantitative traits in farm animals – 15
• Genetic parameters for body weight, egg number and egg weight in chickens      –       20

• Heritability – –   20
• Genetic relationships – –    22
  • Relationship between growth and reproduction – –    22
  • Relationship between egg production and other productive traits –  23
• Effect of selection – –        23
  • Effect of selection on genetic variance and heritability – – 23
  • Genetic and phenotypic correlations –      24
• Response to selection (R) – –     25

MATERIALS AND METHOD 

• The study site – –           –   27
• The reference population – – –         27
  • The foundation stock or base population – –           –           –           27
  • Generation of the starting stock (G₀ generation) – –           –           28
• Management of the G₀ generation – –           –           –           –           28
• Establishment of control population – –        31
• Generation and management of G₁ and G₂ generations – –  32
• Measurement of traits – –       32

3.6.1 (i) Growth trait  –              32

• Body weight at first egg (BWFE) –         32
• Final body weight of cocks –       32

3.6.2 Egg production traits      –      32

• Selection in the G₀ generation – –    33
  • Selection within the male population – –   33
  • Selection within the female population – –  33
  • Construction of selection index – –    33
  • Determination of relative economic weights – – 35

3.7.4. (i) Body weight –         35

• Egg number –           36
• Egg weight –           –        36
  • Selection in subsequent generations (G₁ and G₂) – -37
• Data analysis – –  -37
  • Performance statistics – – -37
  • Estimation of genetic parameters – -37
    • Heritability (h²) – -38
    • Genetic correlation (r_g) -38
    • Phenotypic correlation (r_p) –  39
    • Environmental correlation (r_E) – 40
  • Measurement of selection applied –  40
    • Selection differential (∆s) – 40
    • Selection intensity (i) –  40
    • Cumulative selection differential –  41
  • Measurement of response to selection – 41
    • Expected direct response (Ri) –  41
    • Cumulative direct response (cumR) – 42
    • Average direct genetic response per generation –   42
    • Expected direct genetic gain per year –  42
    • Predicted direct genetic response (Rp) –    43
    • Realized (observed) genetic response (∆G_R) – 43
    • Expected genetic gain (response) in the index value due to selection on the index score (I) -44

• Expected genetic gain in the component traits of the index due to selection on index score (I) –   44

• Effectiveness of selection – 44

4.0 RESULTS AND DISCUSSION 

4.1 Body weight          –        45

• Heritability estimates for body weight at various age periods – –            54
• Selection differentials, phenotypic standard deviation (s p ) and selection intensity for males  –   59

• Response to selection in the male population – –           –           –            62
• Total egg number, average egg weight and body weight at first egg – 65
• Response to selection in the Female population – –           –           –           69
• Genetic, phenotypic and environmental correlations (r_g, r_p, and r_E) – 72

• Estimates of additive genetic heritability (h2)for egg number, egg weight and body weight at first egg –    75
• Relative economic weight for egg number, egg weight and body weight at first egg –       77

• Selection response in egg number, egg weight and body weight at first egg 79
• Mean values, selection differential, phenotypic standard deviation,selection intensity, heritability and expected response for index score  –   83

• Response in the component traits of the index due to selection on index score        –      85

5.0       CONCLUSION AND RECOMMENDATION

5.1 Conclusion            –             87

5.2 Recommendations            88

REFERENCES              89

APPENDICES   –          100

Introduction

Background Of Study

The report of the FAO expert consultation on animal genetic resources (FAO 1973) recommended the improvement and conservation of animal genetic resources indigenous to countries.

However, two major constraints delayed its implementation until the 1980s. These constraints include the lack of funds on the one hand, and the delay caused by the disagreement between scientists concerning the genetic merits of these indigenous breeds on the other hand.

Most scientists were at this time locked in the paradigm of economic progress as the only value.

Consequently, the prevailing animal production policy then (1960s and 1970s) was to try to improve tropical breeds by introducing temperate breeds with high genetic merits (AGRI, 2002).

Indigenous breeds were considered obsolete. Improving and conserving indigenous  breeds were regarded as uneconomic and, therefore, should be allowed to disappear.

But Payne and Hodges (1997) had noted that the philosophy of improving animal production in the tropics with temperate breeds did not only fail but also damaged indigenous breed resources.

Humanity shapes biodiversity, knowingly or unknowingly. This biodiversity results both from natural selection for adaptation and artificial selection through human choices for use  and/or aesthetic value.

References

Adedokun, S.A., and Sonaiya, E.B. (2001): Comparison of the performance of Nigerian indigenous chickens from three agro ecological zones. Livestock research for rural development 3(2). 34 – 39.

AGRI. (2002): The global strategy for the management of farm animal genetic resources – an update. AGRI (2002), 32: 1- 12.

Akinokun, O., and Dettmers, A. (1977a): Comparison of the Ife breeds of the indigenous chicken of Nigeria with improved exotic strains. 2: body weight at sexual maturity. Nig. J. Anim. Production 4 (1): 269 – 270 (Abstract).

Akinwumi, J.A., Adegeye, A.J., Ikpi, A.E., and Olayide, S.O. (1979): Economic analysis of the Nigerian poultry industry. Fed. Livestock Dept. Lagos.

AL-Rawi, A.A., and AL-Athari, A.K. (2002): Characteristics of indigenous chicken in Iraq.AGRI, 2002, 32: 87 – 93.

Asuquo, B.O., and Nwosu, C.C. (1987): Heritability and correlation estimates of body weight in the local chicken and their crosses. E. Afr. Agric. For J. 52 (4): 267 – 271