ABSTRACT
106 grand-parent Hyla rabbits of New Zealand (NZW) and California (CAW) breeds were
imported from France consisting of 22 bucks of 11 NZW line (HYLA.GPC) and 11 CAW
line (HYLA.MAX) and 84 does of NZW line (HYLA.NG). They were mated naturally to
produce two genetic groups consisting of 205 and 192 kits for Hyla purebred and crossbred
respectively. 20 non-descript rabbits consisting of 12 old and 8 grower rabbits were used as
control for the physiological evaluation. Adaptability index were found to be
proportionately moderate in Hyla New Zealand grand-parent (HNZW), Hyla California
grand-parent (HCAW) and old non-descript (OND) (0.37, 0.36 and 0.39) respectively.
However values obtained for the F1 progeny lines and grower non-descript were 0.34, 0.33
and 0.35 for Hyla New Zealand (HNP), Hyla New Zealand X Californian (NCP) and grower
non-descript (GND). Genetic groups for both grand-parent and its FI progeny rabbits had
significant (P < 0.05) influence on body-weights at all ages. Reproductive traits such as litter
size at birth (LSB) to litter size at 35 (LS35), litter weight at birth (LWB) to litter weight at
35 (LW35) were significantly (P < 0.05) higher for purebred than the crossbred Hyla
rabbits. Individual kit weights were significantly (P < 0.05) higher for crossbred than the
purebred rabbits at pre and postweaning ages. Estimates of heritability (0.39 – 1.30),
repeatability (0.21 – 0.77), and phenotypic correlations (0.28 – 1.00) were moderate to high,
except for genetic correlations (0.09 – 0.87) which were low to high from birth through 35
days for pre weaning kit weights. From the factor analysis, two principal components which
accounted for 83.97 % of the total variance were extracted for Hyla purebred and three
principal components accounted 89.88 % for Hyla crossbred rabbits. In conclusion, the
average performance of the Hyla rabbits was moderate and this implied gradual
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acclimatization to the tropical environment of Zaria. Heritability and repeatability estimates
implied that progress will be faster through individual selection for the pre weaning traits.
The adaptability index should be further investigated to include more variables and larger
sample size to improve accuracy of the estimates obtained.
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TABLE OF CONTENTS
Cover page – – – – – – – – – i
Title page – – – – – – – – – ii
Declaration – – – – – – – – – iii
Certification – – – – – – – – – iv
Dedication – – – – – – – – – v
Acknowledgment – – – – – – – – vi
Table of contents – – – – – – – – vii
List of tables – – – – – – – – – xiii
List of figures – – – – – – – – xv
List of abbreviations – – – – – – – – xvi
Abstract – – – – – – – – – xix
CHAPTER ONE
1.0 INTRODUCTION – – – – – – – 1
CHAPTER TWO
2.0 LITERATURE REVIEW – – – – – – 4
2.1 Historical Origin of Rabbits – – – – – – 4
2.2 Biological Description of Rabbits – – – – – – 4
2.3 Rabbit Breeds – – – – – – – – 5
2.3.1 New Zealand White Breed – – – – – – 5
2.3.2 Californian Breed – – – – – – – 6
2.3.3 Chinchilla Breed – – – – – – 6
viii
2.4 Rabbit Hybrids – – – – – – – 7
2.4.1 Hyla Hybrid – – – – – – – – 7
2.4.2 Hycole Hybrid – – – – – – – 7
2.4.3 Hyplus Hybrid – – – – – – – 7
2.4.4 Non Descript Rabbits- – – – – – – 8
2.5 The Concept of Stress – – – – – – 8
2.5.1 Definition of Stress – – – – – – – 8
2.5.2 Causes and Symptons of Stress – – – – – 9
2.5.3 Mechanism of Heat Balance – – – – – – 11
2.5.3.1 Thermoregulatory Function – – – – – 11
2.5.3.2 Heat Dissipation Pathways – – – – – 12
2.5.3.3 Respiration rate – – – – – – – 12
2.5.3.4 Ear Lobe – – – – – – – – 14
2.5.3.5 Pulse Rate – – – – – – – 14
2.6 Body Temperature Changes – – – – – – 14
2.6.1 Rectal temperature- – – – – – – – 14
2.7 Adaptability Estimation – – – – – – 15
2.8 Doe Litter Traits – – – – – – – – 15
2.8.1 Litter Size – – – – – – – – 16
2.8.2 Litter Weight – – – – – – – – 16
2.9 Factors Affecting Doe Litter Traits – – – – – 16
2.9.1 Genetic and Non-Genetic Factors – – – – – 16
2.9.1.1 Parity – – – – – – – – – 17
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2.9.1.2 Lactation – – – – – – – 17
2.9.1.3 Pre-weaning Mortality – – – – 18
2.10 Growth Traits – – – – – – – 19
2.10.1 Pre-weaning Growth – – – – – – 19
2.10.2 Post-weaning Growth – – – – – 19
2.11 Genetic Parameters for Growth Traits – – – – 20
2.11.1 Heritability- – – – – – – – 20
2.11.2 Repeatability – – – – – – 21
2.11.3 Genetic and Phenotypic Correlation of Bodyweight – 22
2.12 Prediction of Bodyweight from Linear Body Measurement – 22
CHAPTER THREE
3.0 MATERIALS AND METHODS- – – – – – – 24
3.1 Location of the Study Area – – – – – – 24
3.2 Experimental Animals and Management – – – – – 24
3.3 Experimental Mating Plan – – – – – – 25
3.4 Data Collection – – – – – – – – 28
3.4.1 Meteorological Data of the Rabbitry Microclimate – – – 28
3.4.2 Thermoregulatory Parameters Measurement – – – 28
3.4.3 Adaptability Estimation – – – – – – 29
3.5 Breeding data estimation – – – – – – – 29
3.5.1 Reproductive Traits – – – – – – – 29
3.5.2 Weaning Traits – – – – – – – 30
3.6 Growth Traits – – – – – – – – 30
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3.6.1 Linear Body Measurements – – – – – – 30
3.7 Statistical Analysis – – – – – 31
CHAPTER FOUR
4.0 RESULTS – – – – – – – – 36
4.1 Temperature Humidity Index – – – – – – 36
4.1.1 Thermoregulatory Response of Hyla Grand-parent and Old Non
Descript Rabbits – – – – – – – – 38
4.1.2 Thermoregulatory Responses of Hyla F1 Progeny and Grower Non
Descript Rabbits – – – – – – – 40
4.1.2.1 Circadian Rhythm – – – – – – – 42
4.1.2.2 Sexual Dimorphism- – – – – – – – 44
4.1.2.3 Adaptability Indices – – – – – – – 46
4.3 Growth and Reproductive performance of Hyla rabbits – – – 48
4.3.1 Growth Performance of Hyla Grand-parent Rabbits – – 48
4.3.2 Growth Performance of Hyla F1 Progeny Rabbits – – – 51
4.3.3 Reproductive Performance at Pre-weaning ages – – – 52
4.3.4 Parity – – – – – – – – – 54
4.4 Genetic Parameter – – – – – – – 56
4.4.1 Heritability Estimates for Pre-weaning Growth Traits – – – 56
4.4.2 Repeatability Estimates for Pre-weaning Growth Traits – – – 56
4.4.3 Genetic and Phenotypic Correlations for Pre-weaning Growth Traits- 56
4.5 Bodyweight and Linear Body Measurement – – – – 58
4.5.1 Least Square Means (± S.E) of Bodyweight and Biometric Traits – 58
xi
4.5.2 Pairwise Phenotypic Correlations between BW and LBMs of Purebred
and Crossbred Rabbits – – – – – – 60
4.5.3 Principal Component Matrix – – – – – – 62
4.5.4 Prediction of Bodyweight of Hyla Rabbits from Interdependent
Body Measurements and Independent Principal Components – 64
4.5.4.1 Purebreds – – – – – – – 64
4.5.4.2 Crossbreds – – – – – – – 64
CHAPTER FIVE
5.0 DISCUSSIONS – – – – – – – – 66
5.1 Thermoregulatory Activities- – – – – – – 66
5.2 Growth Performance of Hyla Rabbits- – – – – – 68
5.2.1 Growth Performance of the Grand-Parent Hyla Rabbits- – – 68
5.2.2 Growth Performance of F1 Progeny Rabbits- – – – 68
5.3 Reproductive Performance- – – – – – – 69
5.3.1 Reproductive Performance of Purebred and Crossbred Hyla Rabbits- 69
5.3.2 Effect of Parity on Reproductive Traits – – – – 71
5.4 Genetic Parameters for Pre-weaning Body weight – – – 72
5.4.1 Heritability Estimates of Preweaning Kits Weight – – – 72
5.4.2 Repeatability Estimates of Preweaning Kits Weight – – – 72
5.4.3 Estimates of Genetic and Phenotypic Correlations – – – 73
5.5 Prediction of Bodyweight from Linear Body Measurements – – 74
5.5.1 Relationship between Bodyweight and Linear Body Measurements- 74
5.5.2 Phenotypic Correlations of Body Weight and Biometric Traits- – 74
xii
5.5.3 Principal Component Analysis – – – – – 75
5.5.4 Prediction of Bodyweight from Linear Body Measurement using
Stepwise Multiple Regression- – – – – – 76
CHAPTER SIX
6.0 SUMMARY, CONCLUSION AND RECOMMENDATION – 77
6.1 Summary – – – – – – – – 77
6.2 Conclusions – – – – – – – – 79
6.3 Recommendations – – – – – – – 80
REFERENCES – – – – – – – 81
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CHAPTER ONE
1.0 INTRODUCTION
Rabbits can be considered as one of the several species quite suitable for meat production. They
are characterized by quality protein (20 – 21 % CP) with high biological value amino acids, meat
low in calories and fat, prolificacy, short gestation length, initial capital outlay, great genetic
flexibility, highly unsaturated lipids (60 % of the total fatty acids), valuable animal model for
biomedical research, low sodium and cholesterol. It is considered a delicacy for healthy food
products (Dalle Zotte, 2002).
However, the most obvious limitation to rabbit production in regions with hot climate is the
susceptibility of this species to heat stress. Heat stress, as indicated by elevated body
temperature, occurs when environmental extremes, acute or chronic, lead to alteration in the rate
of heat production and body temperature (Freeman, 1988). It occurs when animals are exposed to
high ambient temperatures (30 – 39.5 oC), high humidity (60 – 90 %), low wind speed and high
direct and indirect solar radiation (Willmer et al., 2000).
The importation of domestic animal diversity is essential to meet future needs in Nigeria due to
the quest for protein sufficiency. Also, this will be a suitable way to improve performance of our
local rabbits by introducing purebred exotic rabbits with high growth and reproductive
potentials. In semi-intensive and intensive systems, the rearing of more productive rabbit breeds
could be a suitable path to improve the productivity and reduce the production cost. Imported
populations such as Hyla rabbits are usually bigger in size, have rapid growth, great adaptability,
better reproductive efficiency and disease resistance. Hamouda et al. (1990) reported that Hyla
rabbits are productive breeds used in many crossbreeding programs for genetic improvement.
2
Estimation of genetic parameters are primordial to the establishment of strategies to be used in
Hyla rabbit breeding programs and the evaluation of response to selection for traits and genetic
associations among traits (Nizza and Moniello, 2000). Diversity that exists between Hyla breeds
and our local breeds is likely to provide genetic combinations suited to a variety of environment
and production systems in Nigeria. Genetic information on production traits for Hyla rabbits
raised under the Guinea Savannah Zone of Nigeria is very limited. Without the knowledge of the
genetics of Hyla rabbits, planned improvement of rabbit meat in Nigeria will be limited. This
study is therefore designed to study the heritable characteristics favouring survival of Hyla
rabbits, the capacity and process of adjustment of the animal to itself and to the physical
environment in its new micro-climate.
Hypotheses:
This study was designed to evaluate the following hypotheses:
Ho: Performance of Hyla rabbits in Guinea Savannah zone are not influenced by their genetic
and physiological changes in response to internal and external stimuli.
Ha: Performance of Hyla rabbits in Guinea Savannah zone are influenced by their genetic and
physiological changes in response to internal and external stimuli.
Ho: Relationships involving body measurements and body weight may not be different when
orthogonal conformation traits derived from the factor analysis are used instead of the
intercorrelated original traits.
3
Ha: Relationships involving body measurements and body weight may be different when
orthogonal conformation traits derived from the factor analysis are used instead of the
intercorrelated original traits.
Specific objectives:
1. To estimate the adaptability of Hyla and non-descript rabbits to the guinea savannah zone of
Nigeria.
2. To determine variations in growth and reproductive traits of Hyla pure and crossbred rabbits.
3. To estimate some genetic parameters for pre-weaning growth traits in Hyla purebred rabbits.
4. To predict bodyweight from biometric traits using principal component factor analysis and
intercorrelated original traits.
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