ABSTRACT
This experiment was conducted to study the heritability and response to selection of egg production and quality traits in three generations of Japanese quail (Cortunix cortunix japonica). A total of 300, 450 and 420 adult Japanese quails mated at seventh week of age and in the ratio of 1:2 male to female ratio were used. A total of 4906 eggs (2461, 1365 and 1080) in base population, Generation One and Generation Two were collected and incubated. Egg collection for egg quality analyses was done at ninth week of age. At mating, Sire body weight was weighed and grouped into four weight groups. Selection for egg number was carried out and the correlated response estimated. Traits measured included body weight of sire at mating, egg number and egg internal and external quality traits. The egg quality trait was carried out using the breakout analysis. Data was analyzed using SAS Statistical Software. The effect of sire bodyweight at mating and the generation of selection on reproductive performance as well as phenotypic correlation between egg quality traits after two generations of selection were also estimated. Selection was carried out for two generations G1, G2 along with a base population G0. The generations of selection for egg production significantly (P<0.05) increased egg number, yolk length, yolk index and shell thickness; while egg weight, egg length, and shell weight significantly (P<0.05) decreased. Sire body weight at mating does not significantly affect all the measured reproductive traits (p>0.05) but there was a significant effect of generation of selection (p<0.05) on early embryonic mortality (13.46, 12.86 and 5.91) and late embryonic mortality (16.63, 17.44 and 11.40), respectively. There was a significant effect (p<0.05) of interaction between sire body weight at mating and generation of selection on all the traits measures. Phenotypic correlation between egg quality traits varied in magnitude and direction (-0.90-1.00) also, heritability estimates of egg production and quality traits ranged from low to high (0.09-0.77). Correlated responses among the egg production and quality traits also varied in magnitude
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and direction. It was observed that egg number improved by 2.37 and 1.56 in generation one and two respectively, as a result of selection. It was concluded that short term selection for increased egg number lead to increased yolk length, yolk index and shell thickness but decreased egg weight, egg length, and shell weight. In addition, heritability and response of egg production and its correlated response with egg quality can be maximized in quail egg improvement program. It is therefore recommended that medium to heavy eggs should be used in hatcheries for better hatchability and reduced embryonic mortality. Also, correlation between traits should be considered in selection designs.
TABLE OF CONTENTS
DECLARATION…………………………………………………………………………………………………………… ii
CERTIFICATION ……………………………………………………………………………………………………….. iii
DEDICATION……………………………………………………………………………………………………………… iv
ACKNOWLEDGEMENTS …………………………………………………………………………………………… v
TABLE OF CONTENT ………………………………………………………………………………………………… ix
CHAPTER ONE …………………………………………………………………………………………………………… 1
1.0 INTRODUCTION……………………………………………………………………………………………………. 1
1.2 Justification of the study ………………………………………………………………………………………….. 3
1.3 Objectives of the study……………………………………………………………………………………………… 3
CHAPTER TWO ………………………………………………………………………………………………………….. 4
2.0 LITERATURE REVIEW ………………………………………………………………………………………… 4
2.1 Origin and Distribution of Japanese Quails. ……………………………………………………………… 4
2.2 Sexual Characteristics of Male Japanese Quails………………………………………………………… 7
2.3 Productive and Reproductive Traits of Japanese quails …………………………………………….. 7
2.3.1. Egg number …………………………………………………………………………………………………………… 8
2.3.2 Egg weight …………………………………………………………………………………………………………… 10
2.3.3 Egg mass ……………………………………………………………………………………………………………… 12
2.3.4 Egg composition …………………………………………………………………………………………………… 12
2.4Fertility and Hatchability ………………………………………………………………………………………… 12
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2.4.1Fertility percentages ……………………………………………………………………………………………….. 13
2.4.2 Hatchability percentages ………………………………………………………………………………………… 14
2.4.3 Embryonic mortality. …………………………………………………………………………………………….. 16
2.5 Egg Quality Characteristics ……………………………………………………………………………………. 17
2.6Selection Studies ……………………………………………………………………………………………………… 20
2.7 Genetic Parameters. ……………………………………………………………………………………………….. 23
2.7.1Heritability ……………………………………………………………………………………………………………. 23
2.7.2 Phenotypic Correlation ………………………………………………………………………………………….. 28
2.8 Selection Response …………………………………………………………………………………………………. 29
2.9 Generation Interval ……………………………………………………………………………………………….. 30
CHAPTER THREE …………………………………………………………………………………………………….. 32
3.0 MATERIALS AND METHODS …………………………………………………………………………….. 32
3.1 Study Location ………………………………………………………………………………………………………. 32
3.2 Management of Experimental Birds ……………………………………………………………………….. 32
3.2.1 Establishment of the foundation stock ……………………………………………………………………… 34
3.2.2 Experimental stock………………………………………………………………………………………………… 34
3.3 Data Collection ………………………………………………………………………………………………………. 35
3.4 Data Analysis ………………………………………………………………………………………………………….. 37
3.4.1Phenotypic correlations (rp) between traits ………………………………………………………………… 38
CHAPTER FOUR ……………………………………………………………………………………………………….. 42
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4.0 RESULTS ……………………………………………………………………………………………………………… 42
4.1 Mean (±SE) and Coefficient of Variation for pooled egg production and egg quality characteristics of Japanese quail egg for base generation ……………………………. 42
4.2 Mean (±SE) and Coefficient of Variation for pooled egg production and egg quality characteristics of Japanese quail egg for Generation one ……………………………………………… 42
4.3 Mean (±SE) and Coefficient of Variation for pooled egg production and egg quality characteristics of Japanese quail egg for Generation two……………………………………………… 42
4.4 Least square means for egg characteristics of Japanese quail at different generations 46
4.5 Hatching characteristics of Japanese quail eggs over three generations of selection ….. 46
4.6 Effect of sire bodyweight at mating and generations of selection on reproduction characteristics of Japanese quail eggs over three generations ……………………………. 49
4.7 Phenotypic correlations of external egg quality traits for Japanese quails over three generations ……………………………………………………………………………………………………………. 51
4.8 Phenotypic correlations of Internal egg quality traits for Japanese quail by Generation …………………………………………………………………………………………………………………………….. 53
4.9 Phenotypic correlations between External and Internal egg quality traits of Japanese quails ……………………………………………………………………………………………………………… 55
4.10 Principal component analyses for egg production and quality traits ………………………. 57
4.11 Realized (h2R) Heritability estimates of egg traits in Japanese quail in Generation one and two …………………………………………………………………………………………………………………. 57
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4.12 Actual and expected Selection Differential of Egg Production and Egg Quality Traits in Generation one ………………………………………………………………………………………………….. 61
4.13 Selection Differential of egg production and egg quality traits in generation two ….. 61
4.14 Realized and Expected Selection Response for egg production and egg quality in Japanese quails ……………………………………………………………………………………………………… 64
CHAPTER FIVE ………………………………………………………………………………………………………… 66
5.0DISCUSSION …………………………………………………………………………………………………………. 66
5.1 Descriptive Statistics for Egg Production and Egg Quality Characteristics of Japanese quail’s Eggs for Base population ……………………………………………………………………………. 66
5.2 Descriptive Statistics for Egg Production and Egg Quality Characteristics of Japanese quail Eggs for Generation One ………………………………………………………………………………. 67
5.3Descriptive Statistics for egg production and egg quality characteristics of Japanese quail egg for Generation two …………………………………………………………………………………. 68
5.4 Least Square Means for Egg Characteristics of Japanese quail at Different Generations …………………………………………………………………………………………………………………………….. 69
5.5 Fertility Traits of Japanese Quail Eggs over three Generations of Selection. ……………. 70
5.6 Effect of Sire Bodyweight at Mating and Generations of Selection on Reproduction Characteristics of Japanese quail Eggs over three Generations ………………………………. 72
5.7 Phenotypic correlations of External egg quality traits for Japanese quails over three generations ……………………………………………………………………………………………………………. 74
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5.8 Phenotypic Correlations of Internal Egg Quality Traits for Japanese quail byGeneration …………………………………………………………………………………………………………………………… 75
5.9 Phenotypic Correlations between External and Internal Egg Quality Traits of Japanese Quails …………………………………………………………………………………………………. 76
5.10 Principal Component Analyses for Egg Production and Quality Traits ………………….. 77
5.11Heritability Estimates of Egg Traits in Japanese quail in Generation One and two …. 77
5.12 Actual and expected Selection Differential of Egg Production and Egg Quality Traits in Generation one and two …………………………………………………………………………………….. 78
5.13 Realized and Expected Selection Response for Egg Production and Egg Quality in Japanese quails …………………………………………………………………………………………………. 79
CHAPTER SIX …………………………………………………………………………………………………………… 81
6.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS………………………………….. 81
6.1 Summary ……………………………………………………………………………………………………………….. 81
6.2 Conclusion …………………………………………………………………………………………………………….. 82
6.3 Recommendation……………………………………………………………………………………………………. 82
REFERENCES ……………………………………………………………………………………………………………. 84
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CHAPTER ONE
1.0 INTRODUCTION
Livestock diversification using animals with short generation interval will be a viable tool in ameliorating shortage of protein among the populace in developing countries (NVRI, 1994). Quails are the most efficient biological machine for converting feed into animal protein of high biological value and hence are the cheapest source of animal protein for human diet (Muthukumar and Dev Roy, 2005). Japanese quail (Coturnix coturnix japonica) is considered a pilot bird for poultry breeding studies because it is the smallest avian species farmed for meat and egg production (Baungartner, 1994; Panda, 1996; Akpa et al., 2008) and it has thus been used widely in many biological experiments. The main advantages for considering Japanese quail as a pilot animal are its rapid growth which makes it marketable for consumption at about 5-6 weeks of age, early sexual maturity resulting in short generation interval, high rate of lay and much lower feed and space requirements than other domestic fowls (Oluyemi and Roberts, 2000).
Selection programmes in poultry has placed much emphasis on rapid early growth rates and increase in body size which result in a significant reduction in the number of days required to grow birds to market weight with indirect improvement in feed conversion (Aboul-Seoud, 2008). Therefore, the merits of selection methods to increase genetic gain depend not only on direct response alone but also on associated changes in other economically or biologically important traits such as egg quality traits as a result of correlated responses to selection (Aboul-Seoud, 2008). Selection for a certain trait may indirectly affect other traits not considered in the programme due to the fact that the improved trait is correlated with these other traits.
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Reproductive traits (fertility and hatchability) are the most important attributes of parent stock performance (Sezer, 2008) hence; selection is possible if sufficient additive genetic variance exists in population or selected lines of those traits (Kaye, 2014). Knowledge of heritability of traits is therefore essential for understanding how individual characteristics change across generations in response to selection (Falconer and Mackay, 1996). Eggs and meat are classified among the most nutritious food; and eggs are rated with milk among the best foods rich in protein, vitamins, essential amino acids, saturated fatty acids, unsaturated fatty acids, phospholipids, iron (Fe) and vitamins (Oluyemi and Roberts, 2000; Muthukumar and Dev Roy, 2005). Egg quality is a term which refers to general standard that define both internal and external quality such as egg weight, length, width, index, shell weight and thickness, albumen height and width, yolk height, index and haugh unit (Scott and Silversides, 2001). The findings of Islam et al. (2001) and Sezer (2008) indicated that the external and internal egg quality traits can affect the future generations and their performance. Reports from various authors (Abdel-Fattah, 2006, Aboul- Seoud, 2008, Okenyi et al., 2013) indicate that heritability estimates for egg quality differ with age and are also affected by environment, experimental conditions and methods of analysis. Akpa et al. (2008) reported the relationship between laying age and repeatability of egg quality traits in Japanese quails. Ojo et al. (2011) reported the effect of egg weight on hatchability and hatching weight in Japanese quail while Ojo and Ayorinde, (2011) also reported the effect of divergent selection for 35th day body weight on growth and egg quality traits of Japanese quails.
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1.2 Justification of the study
Most studies on quails were aimed at increasing meat and egg production (Ani et al., 2009). With this goal, new breeds of quails have been obtained for meat and egg type. For egg type quails the intention has been to increase total egg mass, to get an earlier sexual maturity and to optimize egg production in order to increase laying performance (Camci et al., 2002). Positive correlations between egg weight, shell weight and shell thickness have also been reported by Farooq et al. (2001) and Khurshid et al. (2013) but there are scanty works on the trend of relationships that exist between egg quality traits over generations of selection, the effect of bodyweight at mating on reproductive traits as well as heritability and response to selection of egg production and quality traits of Japanese quails.
1.3 Objectives of the study
The broad objective of this study is to determine the heritability and response to selection of egg production and quality traits in Japanese quails The specific objectives of this study are to determine the:
1. Effect of bodyweight of male quails at mating on reproductive performance of Japanese quails.
2. Trend of relationship between the external and internal egg quality traits over two generations in quails.
3. Heritability (h2S) of egg production traits and response (R) to selection of egg production and egg quality traits in Japanese quails.
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