ABSTRACT
A multiple trait selection programme was designed and carried out at the Department of Animal Science Teaching and Research Farm, University of Nigeria, Nsukka to further determine the genetic response of productive traits of the Nigerian heavy local chicken ecotype (NHLCE) using selection index from fourth to sixth generation. The parameters measured included growth traits and egg production traits. Six (6) heavy local chicken ecotype-cocks and sixty hens were randomly selected to form the base population. They were artificially inseminated and fertile eggs were collected and hatched. On hatching, a total number of 270 day-old chicks were produced from three hatches and used according to six sire families by use of colour markers. These chicks formed the reference population from which G4 and subsequent G5 and G6 populations were generated. The chicks were brooded and reared according to standard management practices. Formulated rations, chick mash, grower mash and layer mash were fed according to each stage of growth. Water and medication were also given. At 23 weeks of age, all pullets were moved into individual laying cages for short term (16 weeks) egg production. A control population was established for each generation, to measure environmental effects and to estimate genetic responses. At the end of the 16weeks (egg production period) layers were subjected to selection, using selection index method incorporating Body weight at first egg (BWFE), Average egg weight (AEW) and Total egg number (TEN). Relative economic weights of the traits and their heritability estimates were used to weight the phenotypic values of each trait in the index. Males were selected based on individual body weight performances at 39weeks of age. Data collected were subjected to statistical analysis using SPSS computer package 2015 version 23.00. From the analysis of variance, sire components of variance were determined and heritability estimates of the traits calculated. Genetic (rg), phenotypic (rP) and environmental (rE) correlations between pairs of traits in the index were estimated. Selection differential, expected, predicted and realized genetic gains/responses were determined for each trait. The results showed significant increases (P<0.05) in all the traits selected. Body weight of males and females were similarly significantly (P<0.05) improved. Total egg number (TEN) and Average egg weight (AEW) increased from 89.98+0.81, 43.52+0.08g in G4 to 93.86+0.36, 44.55+0.15g, in G5 and 94.98+0.51, 45.06+0.12g in G6 respectively. Selection differential values were positive for 39 weeks body weight in males across the three generations with a mean of 119.18g, total egg number (mean 6.46) and (0.39) for average egg weight in females. It was negative on the average for body weight at first egg (-11.94g) due to the negative value of its economic weight. Selection intensity (i) values for total egg number (TEN), average egg weight (AEW) and body weight at first egg (BWFE) for G4, G5 and G6 generations respectively for females were TEN G4 (2.12), G5 (1.42) and G6 (2.38); AEW G4 (0.908), G5 (0.514) and G6 (0.562) and BWFE G4 (-0.601), G5 (-0.519) and G6 (-0.393). With mean intensity values of TEN (1.97), AEW (0.661) and BWFE (-0.504). selection intensity (i.) for body weight of males at 39 weeks of age (mass selection) were 0.754, 0.714 and 0.615 for G4, G5 and G6 generation respectively. Direct selection responses namely, expected, predicted and realized genetic gains were all positive for all the traits selected. The mean ratio of 0.56 as realized to expected genetic gain was recorded for 39weeks body weight in males, 0.96 in BWFE, 1.62g in AEW and 1.42 in TEN. Estimates of heritability (h2) ranged from moderate to high in egg weight, low to moderate in egg number and moderate to high in BWFE, while positive, negative, low, moderate and high genetic (rg), phenotypic (rP) and Environmental (rE) correlations were recorded for pairs of traits in EN-EW, EN-BWFE and EW-BWFE.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgement iv
Abstract v
Table of contents vii
List of Tables ix
Glossary of Terms xi
CHAPTER ONE 1
10 Introduction 1
1.1 Research Objectives 2
1.2 Problem Statement and Justification of the Study 3
CHAPTER TWO 4
2.0 Literature Review 4
2.1 Origin and Domestication of Chicken 4
2.2 Characterization of the Nigerian Chickens 4
2.3 Egg Production in Local Chicken of Nigeria 8
2.4 Body Weight at First Egg and Egg Size 9
2.5 Heritability and genetic correlations on growth and egg production traits
in the Nigeria Indigenous chickens 9
2.6 Selection Criteria in Poultry and Tools for animal Genetic Improvement 11
2.6.1 Selection Methods 13
CHAPTER THREE: MATERIALS AND METHODS 15
3.1 Study Site 15
3.2 Experimental Animals 15
3.3 Breeding/Mating Arrangement 16
3.4 Semen Collection and Routine Examination 17
3.5 Generation of the starting stock (G4 Generation) 17
3.6 Management of the G4 Generation 17
3.7 Layer Management and Egg Production Monitoring 21
3.8 Establishment of Control Population 23
3.9 Generation and Management of G5 and G6 Generations 23
3.10 Data Collection and Measurement of Traits 23
3.11 Selection in the G4 Generation 24
3.12 Selections within the Female Population 25
3.13 Construction of Selection Index 25
3.13.1 Relative economic value/weight of animal 26
3.14 Methods of Determining the Economic Weight of Traits 27
3.15 Determination of the Relative Economic Weights using Deterministic
Model Approach (Ogbu et al., 2014) 27
3.16 Selection within G4 Generation 29
3.17 Selection in G5 and G6 30
3.18 Data Analysis 30
3.18.1 Descriptive statistics 30
3.18.2 Estimation of genetic parameters 30
3.18.3 Measurement of selection applied. 32
3.18.4 Realized (observed) genetic response (∆GR) 35
3.18.5 Expected genetic gain (Response) in the index value (∆GI) due to
selection on the index score 35
3.18.6 Expected genetic gain in the component traits due to selection on the index 35
3.18.7 Effectiveness of Selection 35
CHAPTER FOUR: RESULTS AND DISCUSSION 36
4.1 Body Weight 36
4.2 Response to selection in the male population 50
4.3 Effects of selection on egg production traits 52
4.4 Generational selection progress in index selected traits for G4, G5 and G6
populations 56
4.5 Genetic, Phenotypic and Environmental Correlations (rg. rp and rE) 58
4.6 Relative economic weights for body weight at first egg (BWFE), average
Egg weight (AEW) and total egg number (TEN) for selected traits 62
4.7 Response in the component traits of the index due to selection
on the index score 72
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 74
Conclusion 74
Recommendation 75
REFERENCES 76
CHAPTER ONE
INTRODUCTION
Nigeria is a country with a large human population and this population needs to be adequately fed with high quality animal products such as egg, meat and milk for good health and increased productivity. The need for improvement in the overall livestock industry, therefore, becomes obvious when viewed against this background of our ever growing population. With a population of 166 million birds (FAO STAT 2007) in Nigeria, the poultry species stand out among the cheapest and highly affordable protein sources for the populace. Nigeria still imports exotic species of livestock including poultry and pigs. The shortage of poultry meat led to the importation of exotic stock which has resulted in the dilution of our indigenous gene pool and neglect of research and improvement of our indigenous gene pool (Ndofor-Foleng et al., 2010).
Also our earlier researchers have concentrated on crossbreeding programmes of the local chicken species with the exotic chicken, with a view of improving their body size (Hill and Modebe 1961, Nwosu 1979 and Omeje et al., 1985). This is commendable since appreciable progress has been made in that direction (Omeje, 2013). However, it has not solved our problem of self sufficiency in animal protein supply. The identification, characterization and selection of the native poultry species in Nigeria for productive purposes cannot be over emphasized. This could help us to improve their performance and also develop our own strain of poultry since they have lived and produced for several years in Nigerian environments especially in the rural communities where their products are readily available (Ajayi 2010). In this regard, the Fulani – ecotype chicken (heavy ecotype chicken) readily comes to mind since it has been identified as one of the purest indigenous chicken because of the secluded lifestyle of the Fulani keepers (Olori 1992, Al-Nasesr et al., 2007).
Humanity shapes biodiversity; this biodiversity results both from natural selection for adaptation and artificial selection through human efforts for use and/or aesthetic value. The selection of distinct genetic traits is reflected in the breed types and races that are adapted to specific uses or environments. Nwosu (1990) and Sonaiya (2013) noted that Nigeria is blessed with a vast array of biodiversity. This array of breeds is a human heritage worthy of improvement and conservation. Their loss is bound to deplete the quality of life (Hodges, 2002).
The Central Bank of Nigeria, CBN (2000) while analyzing the economic sub-sectors noted that the Gross Domestic Product (GDP) has been on the down ward trend. Since the nature of GDP reflects the standard of living of the citizens, it means that the standard of living of Nigerians has been on the decline. By extension, this also implies that the animal protein intake of the average Nigerian on daily basis of 45.4g has continued to fall far below the recommended level which is 53.8g on daily basis (Iyangbe et al., 2009) citing FAO, ( 1992).
The local chickens of Nigeria play major roles through their contributions to food security, household income, employment and quick funds in emergencies (Adedokun et al., 2001, Momoh and Nwosu 2005, Momoh et al., 2010). The genetic base of the local chicken could form the genetic basis of improvement and diversification to produce our own breed/strain of egg or meat type bird as they have been shown to be adapted to harsh local climatic environment (Nwosu and Orneje 1985, Ogbu, 2010, Adedokun 2001, Momoh et al., 2010).
The improvements of the indigenous livestock species require sustained and painstaking approach which would eventually make us self – sufficient in livestock products. Biochemical genetics/genetic engineering, biotechnology and more recently genomics offer useful information to breeders with regard to livestock improvement (Dubey, 2006), however, they are not likely to replace the conventional methods of selection (Nordskog 1981, FAO, 2003) .The novel methods could argument traditional methods such that information obtained could be incorporated into an overall selection index to make selection more effective. Hence, for Nigeria to develop her own indigenous breed/strain of livestock species including poultry, selection is still a basic technology and a better option for now (Agbo et al., 2013).
1.1 Research Objectives
The general objective of this study is to improve the performance of the Nigerian heavy local chicken ecotype (NHLCE) with respect to productive traits by index selection.
The specific objectives include:
- To select by index heavy local chicken ecotype from the 4th to the 6th
- To investigate the short – term egg production traits and growth parameters in these three generations.
- To obtain and document information/data on genetic parameters, namely heritability, genetic correlation as well as phenotypic and environmental correlations respectively, of body weight, egg weight and egg number in the selected population.
- To undertake selection in the NHLCE using mass selection for body weight in males and a selection index for body weight at first egg, average egg weight and short term egg production (egg number) in females with a view to improving its performance.
1.2 Problem Statement and Justification of the Study
The difficulty in procuring parent stock and day – old chicks in Nigeria is of great concern. This challenge has been attributed to lack of indigenous parent stock and many states not having strong international link with foreign poultry breeders coupled with the absence of indigenous poultry breeding companies in the country (Ohagenyi, 2014). So far, over 90% of the commercial poultry farms with parent stocks are resident in Oyo State because of their proximity to foreign affairs at Lagos State. This implies that the order remaining 35 states depend on only Oyo State for the supply of day- old chicks and parent stock to our farmers, a situation that is not healthy for the rapidly growing population whose poultry industry presents such scenario.
The high cost of these exotic birds make the Nigerian farmers incur far more total cost leading to less net profit and also high cost of poultry products. The justification in carrying out this study, therefore, stems from the following reasons. It would be good and necessary to develop our own breed/strain of egg or meat type of bird to conserve our foreign exchange on importation of day – old chicks’, fertile eggs and parent stock. It would also be important to evaluate the growth traits and improve on the productive traits of our native chicken genetic resources that have been proven to be adapted to our local environmental conditions (Omeje and Nwosu 1983, 1985, 1988, Peters et al., 2002, Adebambo, 2002, 2006, Ogbu and Omeje 2011, Olowofeso, 2013). Selection, as a tool in animal improvement, is still a basic technology (Robbins and Staub, 2005, Davis and Berzonsky, 2006) and in Nigeria, since all our livestock species including poultry have not been completely characterized, developed and registered as breeds except the Shika brown layer Alaku (2008), breeders need that selection tool. Developing our own strain/breed of egg or meat type bird is necessary.
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