ABSTRACT
The experiment was carried out to investigate the effect of dietary vitamin C levels on growth performance, thermoregulatory response, and semen characteristics of rabbit bucks in the hot-dry and cool-wet season of Zaria Nigeria. A total of 55 10 month old rabbit bucks consisting of 40 (NZW) pure and 15 (NZW×CAL) crossbred Hyla rabbits were allotted in a 2× 2×4 factorial arrangement in a Completely Randomized Design. The factors considered were vitamin C levels (100 control, 200, 300 and 400 mg/kg) season (hot dry: March-June and cool wet: July-August), breed (pure and crossbred). Results obtained showed that vitamin C levels had significant (p<0.01) effect on growth performance. Breed had significant (p<0.05) effects on growth performance. Season had significant (p<0.01) effect on growth performance. Month had significant (p<0.01) effect on growth performance. There was interactions between vitamin C levels and breed on growth performance (p<0.01). There was interaction between vitamin C levels and month on growth performance (p<0.05). There was interaction between breed and season on growth performance (p<0.01). There was interaction between breed and month on growth performance (p≤0.01). Vitamin C levels had significant (p<0.05) effect on thermoregulatory response. Season had significant (p<0.01) effect on thermoregulatory response. Month had significant (p<0.01) effect on thermoregulatory response. There was interaction between vitamin C levels and breed on thermoregulatory response (p<0.01). There was interaction between vitamin C levels and season on thermoregulatory response (p<0.05). There was interaction between vitamin C levels and month on thermoregulatory response (p<0.05). There was interaction between breed and season on thermoregulatory response (p<0.01). There was interaction between breed and month on thermoregulatory response (p<0.05). Vitamin C levels had significant (p<0.05) effect on semen characteristics. Breed had significant (p<0.05)
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effects on semen characteristics. Season had significant (p<0.05) effect on semen characteristics. Month had significant (p<0.05) effect on semen characteristic. There was interactions between vitamin C levels and season on semen characteristics (p<0.05). Vitamin C levels had significant (p<0.05) effect on sperm morphological abnormalities. Season had significant (p<0.05) effect on sperm morphological abnormalities. Month had significant (p<0.01) effect on sperm morphological abnormalities. There was interaction between vitamin C levels and breed on sperm morphological abnormalities (p<0.05). There was interaction between vitamin C levels and month on sperm morphological abnormalities (p<0.01). There was interaction between breed and season on sperm morphological abnormalities (p<0.05). There was interaction between breed and month on sperm morphological abnormalities (p<0.05). It is concluded from this study that crossbred bucks performed better on 200 mg vitamin C, while purebred bucks performed better on 400 mg vitamin C.
TABLE OF CONTENTS
Title page- – – – – – – – – – – i Declaration- – – – – – – – – – – ii Certification – – – – – – – – – – iii Dedication – – – – – – – – – – iv Acknowledgements – – – – – – – – – v Abstract – – – – – – – – – – xvii Table of Contents – – – – – – – – – vi List of Tables – – – – – – – – – – xiii List of Figures – – – – – – – – – – xv Abbreviation – – – – – – – – – – – xvi CHAPTER ONE
1.0 INTRODCUTION – – – – – – – – – 1
1.1 Justification – – – – – – – – – – 2 1.2 Research Hypothesis- – – – – – – – – 3 1.3 Objectives of Study – – – – – – – – – 3 CHAPTER TWO
2.0 LITERATURE REVIEW
2.1. Concept of Heat Stress – – – – – – – – – 4 2.1.1 Effect of Heat Stress on Physiological Parameters – – – – 5 2.1.2 Effect of Heat Stress on Growth Performance – – – – – 5 2.1.3 Effect of Heat Stress on Enzymes – – – – – – 6 2.1.4 Effect of Heat Stress on Hormones – – – – – – – 6
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2.1.5 Effect of Heat Stress on Reproduction – – – – – – 7 2.2. Mechanism of Heat Stress Regulation in Rabbit Bucks – – – – 7 2.3 Functions of Vitamin C – – – – – – – – 9 2.4. Performance Characteristics of Rabbit Bucks during Heat Stress – – – 12 2.4.1 Feed Intake- – – – – – – – – – 12 2.4.2 Water Intake- – – – – – – – – – 13 2.4.3 Weight Gain- – – – – – – – – – 14 2.4.4 Scrotal Circumference – – – – – – – – 14 2.4.5 Reaction Time- – – – – – – – – 15 2.5 Indicators of Physiological Stress – – – – – – – 16 2.5.1 Skin Temperature- – – – – – – – – 16 2.5.2 Ear Temperature- – – – – – – – – 16 2.5.3 Scrotal Temperature – – – – – – – – 17 2.5.4 Rectal Temperature – – – – – – – – – 18 2.5.5 Respiratory Rate- – – – – – – – – 19 2.5.6 Heart Rate – – – – – – – – – – 20 2.6. Semen Characteristics – – – – – – – – 20 2.6.1 Semen Volume- – – – – – – – – 21 2.6.2 Sperm Motility – – – – – – – – – 22 2.6.3 Semen pH – – – – – – – – – – 23 2.6.4 Sperm Concentration – – – – – – – – 24 2.6.5 Semen Colour – – – – – – – – – 24 2.6.6 Live and Dead ratio – – – – – – – – – 25
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2.7 Sperm Morphology and Abnormalities – – – – – – – 26 CHAPTER THREE
3.0 MATERIALS AND METHODS
3.1 Experimental Site – – – – – – – – – 28 3.2 Experimental Animals and Management – – – – – – 28 3.3 Data Collection – – – – – – – – – – 29 3.4 Statistical Analysis – – – – – – – – – 31 CHAPTER FOUR
4.0 RESULT
4.1 Average Monthly Ambient Temperature and Relative Humidity – – 34 4.2 Effect of Vitamin C Levels on Growth Performance of Rabbit Bucks – – 34 4.3 Effect of Breed on Growth Performance of Rabbit Bucks – – – – 37 4.4 Effect of Season on Growth Performance of Rabbit Bucks – – – 37 4.5 Effect of Month on Growth Performance of Rabbit Bucks – – – 40 4.6 Interaction between Vitamin C Levels and Breed on Growth Performance of Rabbit Bucks – – – – – – – – – – 42 4.7 Interaction between Vitamin C Levels and Season on Growth Performance of Rabbit Bucks – – – – – – – – – – 44 4.8 Interaction between Vitamin C Levels and Month on Growth Performance of Rabbit Bucks – – – – – – – – – – – 44 4.9 Interaction between Breed and Season on Growth Performance of Rabbit Bucks- 47 4.10 Interaction between Breed and Month on Growth Performance of Rabbit Bucks- 47 4.11 Effect of Vitamin C Levels on Thermoregulatory Parameters of Rabbit Bucks- 50 4.12 Effect of Breed on Thermoregulatory Parameters of Rabbit Bucks – – 50
4.13 Effect of Season on Thermoregulatory Parameters of Rabbit Bucks – – 50
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4.14 Effect of Month on Thermoregulatory Parameters of Rabbit Bucks – – 54 4.15 Interaction between Vitamin C levels and Breed on Thermoregulatory Parameters of Rabbit Bucks – – – – – – – – – 54 4.16 Interaction between Vitamin C Levels and Season on Thermoregulatory Parameters of Rabbit Bucks – – – – – – – – – 57 4.17 Interaction between Vitamin C Levels and Month on Thermoregulatory Parameters of Rabbit Bucks – – – – – – – – – 57 4.18 Interaction between Breed and Season on Thermoregulatory Parameters of Rabbit Buck – – – – – – – – – – – 60 4.19 Interaction between Breed and Month on Thermoregulatory Parameters of Rabbit Bucks – – – – – – – – – – 60 4.20 Effect of Vitamin C Levels on Semen Characteristics of Rabbit Bucks- – 60 4.21 Effect of Breed on Semen Characteristics of Rabbit Bucks – – – 64 4.22 Effect of Season on Semen Characteristics of Rabbit Bucks – – – 64 4.23 Effect of Month on Semen Characteristics of Rabbit Bucks – – – 64 4.24 Interaction between Vitamin C Levels and Breed on Semen Characteristics of Rabbit Bucks – – – – – – – – – – – 65 4.25 Interaction between Vitamin C Levels and Season on Semen Characteristics of Rabbit Bucks – – – – – – – – – – – 65 4.26 Interaction between Vitamin C Levels and Month on Semen Characteristics of Rabbit Bucks – – – – – – – – – – – 65 4.27 Interaction between Breed and Season on Semen Characteristics of Rabbit Bucks- 65 4.28 Interaction between Breed and Month on Semen Characteristics of Rabbit Bucks- 73 4.29 Effect of Vitamin C Levels on Sperm Morphology of Rabbit Bucks – – 73 4.30 Effect of Breed on Sperm Morphology of Rabbit Bucks – – – 73
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4.31 Effect of Season on Sperm Morphology of Rabbit Bucks – – – 77 4.32 Effect of Month on Sperm Morphology of Rabbit Bucks – – – 79 4.33 Interaction between Vitamin C Levels and Breed on Sperm Morphology of Rabbit Bucks – – – – – – – 79 4.34 Interaction between Vitamin C Levels and Season on Sperm Morphology of Rabbit Bucks – – – – – – – 80 4.35 Interaction between Vitamin C Levels and Month on Sperm Morphology of Rabbit Bucks – – – – – – – 80 4.36 Interaction between Breed and Season on Sperm Morphology of Rabbit Bucks – – – – – – – 87 4.37 Interaction between Breed and Month on Sperm Morphology of Rabbit Bucks – – – – – – – 87 CAPTER FIVE
5.0 DISCUSSION
5.1 Effect of Vitamin C Levels on Growth Performance – – – – 92 5.2 Effect of Breed on Growth Performance – – – – – 92 5.3 Effect of Season on Growth Performance – – – – – 93 5.4 Effect of Month on Growth Performance – – – – 94 5.5 Effect of Interaction between Vitamin C Levels and Breed on Growth Performance- 95 5.6 Effect of Interaction between Vitamin C Levels and Month on Growth Performance- 96 5.7 Effect of Interaction between Breed and Season on Growth Performance- – 96 5.8 Effect of Interaction between Breed and Month on Growth Performance- – 96 5.9 Effect of Vitamin C Levels on Thermoregulatory Parameters – – – 97 5.10 Effect of Season on Thermoregulatory Parameter – – – – 97
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5.11 Effect of Month on Thermoregulatory Parameters – – – – 98 5.12. Effect of Interaction between Vitamin C Levels and Breed on Thermoregulatory Parameters – – – – – – – – – 99 5.13 Effect of Interaction between Vitamin C Levels and Season on Thermoregulatory Parameters – – – – – – – – – 100 5.14 Effect of Interaction between Vitamin C Levels and Month on Thermoregulatory Parameters – – – – – – – – – 100 5.15 Effect of Interaction between Breed and Season on Thermoregulatory Parameters- 100 5.16 Effect of Interaction between Breed and Month on Thermoregulatory Parameters- 101 5.17 Effect of Vitamin C Levels on Semen Characteristics – – – – 101 5.18 Effect of Breed on Semen Characteristics – – – – – 101 5.19 Effect of Season on Semen Characteristics – – – – – 101 5.20 Effect of Month on Semen Characteristics – – – – – 102 5.21 Effect of Interaction between Vitamin C Levels and Season on Semen Characteristics – – – – – – – – – 102 5.22 Effect of Vitamin C Levels on Sperm Morphology – – – – 102 5.23 Effect of Season on Sperm Morphology – – – – – 103 5.24 Effect of Month on Sperm Morphology – – – – – 103 5.25 Effect of Interaction between Vitamin C Levels and Breed on Sperm Morphology- 104 5.26 Effect of Interaction between Vitamin C Levels and Month on Sperm Morphology- 104 5.27 Effect of Interaction Breed and Season on Sperm Morphology – 104 5.28 Effect of Interaction between Breed and Month on Sperm Morphology – 104
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CHAPTER SIX 6.0 SUMMARY, CONCLUSION AND RECOMMENDATION 6.1 Summary – – – – – – – – – – 105 6.2 Conclusion- – – – – – – – – – 109 6.3 Recommendation- – – – – – – – – 110 6.4 References – – – – – – – – – 111
CHAPTER ONE
1.0 INTRODUCTION Reproductive inefficiency is one of the most limiting constraints to efficient rabbit production. The efficiency of spermatozoa production, libido, and semen quality changes throughout the reproductive life of an animal due to nutrition, environment, health status, drugs, and chemicals (Ifeanyi, 2009). In tropical countries, high temperature hinders the success of rabbit farming (Cervera et al., 1997) as it leads to a significant reduction in daily weight gain, feed intake and feed efficiency (Chiericato et al., 1993). A very important limitation to rabbit production in a hot climatic area is heat stress. Susceptibility to heat stress produces a series of changes in biological functions which in turn lead to impairment of production and reproductive function (Marai et al., 1999). Such detrimental effects are evident during the hot season of the year, which are reflected in limiting the breeding season of rabbits, normally from May to September in the Northern hemisphere (Marai et al., 1996). The effect of heat stress is aggravated when heat is accompanied by high humidity (Habeeb et al., 1993; Marai et al., 1996; 2001). The changes that occur in rabbits biological functions are depressed feed intake, feed efficiency, utilization, and disturbance in metabolism of water, protein, energy, mineral balance, enzymatic reaction, hormonal secretions and blood metabolites (Marai et al., 2002).
In rabbits, stress associated with exposure to high ambient temperature decreases growth performance, possibly because it destroys cellular biological molecules (Liu et al., 2011). During stress episode, reactive oxygen species (ROS) generation exceeds the body antioxidant production capacity, and oxidative stress develops (Roth, 2000). These active metabolites could
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result in drastic damage to cell structures, protein, lipid, and DNA, and further induce physiological and pathological changes, resulting in poor performance, reduced welfare of the live animal and worsen its meat quality (Abdel-Kalek, 2010). Endogenous antioxidant enzymes are the major cell defense against oxidative stress (El-Medany et al., 2012). Glutathione peroxidase (GSH-PX) and catalase (CAT) are considered the major peroxide removing enzymes located in the cytosol (El-Medany et al., 2012). Superoxide dismutase (SOD) plays an important role in protecting against damage by the superoxide anion radical (Chan and Decker, 1994). Dietary supplementation has been proven to be a simple and convenient strategy to introduce natural antioxidant that may effectively inhibit the reactive oxygen species reaction (ROS) (Botsoglou et al., 2004). Vitamin C is widely used to alleviate heat stress in rabbits, more over this vitamin promotes growth, reproduction, and counteracts infections by pathogenic bacteria and viruses (Wang et al., 2004). It also serves as nutritional supplement, as well as reduce metal ions that generate free radicals (Valko et al., 2005). It is also a co-factor in at least eight enzymatic reactions including several collagen synthesis reactions that, when dysfunctional, causes the most severe symptom of scurvy in animals, these reactions are especially important tin wound healing and preventing bleeding from capillaries (Kotze et al., 1974). Vitamin C induces suppression of serum aspartate aminotransferase (AST) and glutamate pyruvate transaminase (ALT). Administration of vitamin C revealed protective activity against the toxic metabolites of diabetes (Hussein et al., 2012). 1.1 Justification
Fertility of rabbit bucks is the basis of reproductive success in rabbit production (Al-Sobayil and Khalil, 2002). The use of antioxidant agent to improve fertility during environmental stress
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becomes necessary (Marai et al., 2002). Vitamin C have been reported to increase body resistance to environmental stress by reducing the synthesis and secretion of corticosteroids, thus alleviating the negative effects of stress (Roth and Kaeberle, 1985). The present study is designed to examine the effects of dietary vitamin C levels on growth, thermoregulatory response and reproductive performance of rabbits bucks in hot-dry and cool-wet season . 1.2 Research Hypothesis: (1). Null Hypothesis (HO): Vitamin C levels have no effect on growth performance, thermoregulatory response and semen characteristics of rabbit bucks (1). Alternative Hypothesis (HA): Vitamin C levels have effect on growth performance, Thermoregulatory response and semen characteristics of rabbit bucks (2). Null Hypothesis (Ho): Season and breed have no effect on growth performance, thermoregulatory responses and semen characteristics of rabbit bucks given graded levels of vitamin C. (2). Alternative Hypothesis (HA): Season and breed have effect on growth performance, thermoregulatory responses and semen characteristics of rabbit bucks given graded levels of vitamin C. 1.3 Objectives The specific objectives of the study were: 1. To evaluate effect of dietary vitamin C levels on growth performance, thermoregulatory responses and semen characteristics of rabbit bucks. 2. To evaluate effect of season and breed on growth, thermoregulatory responses and semen characteristics of rabbit bucks given graded levels of vitamin C.
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