ABSTRACT
This study which lasted for 52 weeks investigated the effects of dietary Vitamin C (L-ascorbic acid) and Vitamin E (dl- alpha tocopheryl acetate) on the performance of laying hens in the humid tropics. A total of 240 twenty-four week old Golden Neslink pullets were randomly selected from a flock of 550 birds and randomly divided into sixteen treatments of 15 pullets. The birds were initially vent examined to ensure that they were at point of lay before commencing the study. Each pullet was randomly assigned to a previously cleaned and disinfected cage measuring 49 x 35 x 42cm at a stocking density of one bird per cage. Four dietary levels of Vitamin C: 0, 200, 400, and 600mg Kg-1 basal diet were combined with four dietary levels of Vitamin E: 0, 125, 250 and 375mg Kg-1 basal diet in a 4 x 4 factorial arrangement in a Completely Randomized Design. All management principles were observed. Dead birds were promptly removed for autopsy when the need arose. At the end of the study, three birds were selected per treatment for haematological investigation. Blood samples were collected from the wing vein of the birds using a 3ml syringe and a 23-gauge needle and placed in micro tubes with Ethlene diamine tetra acetic acid (EDTA) as anti-coagulant for determining the haematological values. The samples were cooled to 4 oC, using icepacks and transferred to the laboratory within 12h of blood collection. The economic implication of the study was then calculated. Data obtained were subjected to analysis of variance (ANOVA) using SPSS. The mean minimum and maximum indoor temperatures recorded during the study ranged between 18.3-25.0 oC and 27. 15-34 oC respectively while the RH values lay between 53.0 and 88.9%. These were well outside the zone of thermo neutrality for laying hens. Results obtained indicated that, there were highly statistical differences (P < 0.01) between Vitamin C and Vitamin E treated birds for hen day production (HDP), feed intake (FI), feed conversion ratio (FCR), Haugh unit score (HUS), , egg weight (EWT) and incidence of cracked eggs. The treatment, T7 (400mg vitamin C + 125 mg vitamin E Kg-1 basal diet) was superior to all the other treatments and had the highest values for HDP (85.45±1.15), FI (113.15±0.56), HUS (96.27±0.47), and EWT (69.11±1.52). These values were however, statistically similar (P > 0.05) to T8 (600mg Vitamin C + 125 mg Vitamin E Kg-1 basal diet). The lowest values for HDP (42.33±1.43), FI (65.42±0.61), HUS (75.50±2.10) and EWT (54.50±1.15) were observed in T1 (Controls). The synergism between Vitamin C and E is different from the sum of the two vitamins applied separately. Loss in body weight, incidence of cracked eggs and mortality were statistically higher (P < 0.01) in T1 (controls) than vitamin treated birds which showed no significant (P > 0.05) differences. With Vitamin C supplementation, birds on T3 (400 mg Vitamin C kg-1 basal diet) were superior to T2 (200 mg Vitamin C kg-1 basal diet) and T4 (600 mg Vitamin C kg-1 basal diet). Similarly, for Vitamin E supplementation, birds on T9 (250 mg Vitamin E kg-1 basal diet) were statistically different (P < 0.01) from T5 (125 mg Vitamin E kg-1 basal diet) and T13 (375 mg Vitamin E kg-1 basal diet). For haematological values investigated T7 recorded the highest values for RBC (4.11±0.15×106), Hb (8.80±0.31g/dl), and WBC (18300±519.62/mm3) and these were statistically similar (P > 0.05) to T8 but highly statistically different (P < 0.01) from the rest of the treatments. There was highly significant interaction (P < 0.01) in the net income/dozen of eggs that accrued from the study. T7 had the highest net income/dozen egg of N1, 627.11±28.68 while the least net income (N560.50±32.12) was generated from T1. This work therefore upholds that vitamins C and E act in synergy, and that the combined effects of the two antioxidants are additive, immunomodulatory, anti-parasitic and economical.
TABLE OF CONTENTS
CONTENT PAGE
TITLE PAGE ii
CERTIFICATION iii
DEDICATION iv
ACKNOWLEDGMENTS v
ABSTRACT vii
TABLE OF CONTENTS viii
LIST OF TABLES xxi
LIST OF FIGURES xxiv
LIST OF PLATES xxvi
CHAPTER ONE
1.0 INTRODUCTION 1
1.1 SPECIFIC OBJECTIVES 4
1.2 JUSTIFICATION OF THE STUDY 4
CHAPTER TWO
2.0 REVIEW OF RELATED LITERATURE 6
2.1 ANATOMY AND COMPOSITION OF THE AVIAN EGG 6
2.1 .1 Shape 6
2.1.2 The Shell 6
2.1.3 Shell Membranes 6
2.1.4 Germinal Disc 6
2.1.5 White (Albumen) 8
2.1.6 Chalaza 8
2.1.7 Yolk membrane 8
2.1.8 Yolk 8
2.1.9 Air Cell 8
2.2 THE AVIAN PHYSIOLOGY OF EGG PRODUCTION 11
2.2.1 The Male Reproductive System 11
2.2.1.1. Deferent duct 11
2.2.1.2 Testes and sperm 12
2.2.2 Female Reproductive System 12
2.2.2.1 Ovary 12
2.2.2.2 Oviduct 17
2.2.2.3 Uterus (shell gland) and eggshell quality 20
2.2.2.4 Vagina 21
2.2.2.5 Cloaca 21
2.2.3 Egg Quality 21
2.2.3.1. Physical and internal measures of egg quality. 24
2.2.3.2 Factors influencing egg shell quality 27
2.3 STRESS IN POULTRY 33
2.3.1 Common Causes Of Stress In Birds 34
2.3.2 TYPES OF STRESS 34
2.3.3 Physiological Mechanism Of Stress Regulation 35
2.3.3.1 The Stage of alarm reaction i.e. Neurogenic. 37
2.3.3.2 The Stage of resistance or adaptation. 37
2.3.3.3 Stage of exhaustion: 39
2.3.3.4 Physiological indicator of stress in poultry 41
2.3.3.5 Physiological reactions of birds to high ambient temperatures. 42
2.3.3.6 Physiological effects of panting 48
2.3.3.7 Adaptation 49
2.4 HOT WEATHER MANAGEMENT OF POULTRY 49
2.4.1 Stocking Density 49
2.4.2 Bird Handling 49
2.4.3 Water Temperature 49
2.4.4 Feeding Time 52
2.4.5. Feed Stimulation 52
2.4.6 Nutrition 52
2.4.7 Housing. 55
2.4.7.1. Naturally ventilated houses 55
2.4.7.2 Power ventilated houses 59
2.4.7.3. Evaporation cooling 60
2.5 REPORTED EFFECTS OF HOT WEATHER ON PRODUCTION ATTRIBUTES OF POULTRY 61
2.5.1 Effect Of Hot Weather On Egg Production 61
2.5.2 Effect Of High Ambient Temperatures On Voluntary Feed Intake. 62
2.5.3 Effect Of Hot Weather On Feed Conversion Efficiency 65
2.5.4 Effect Of High Environmental Temperature On Egg Shell Quality 65
2.5.5 Effects Of Hot Weather On Body Weight Gain 67
2.5.6 Effect Of Hot Weather On Egg Weight, Fertility And Hatchability 68
2.5.7 The Avian Blood. 68
2.5.7.1 Blood plasma. 69
2.5.7.2 Red blood cells (RBCs). 69
2.5.7.3 Haemoglobin 70
2.5.7.4 Blood platelets. 70
2.5.7.5 White blood cells (WBCs). 70
2.5.7.6 Effect of Heat Stress On Hematocrit Values 75
2.5.7.7 Effect Of Heat Stress On Blood Electrolytes In Birds. 76
2.5.8 Effect Of Hot Weather On Disease Prevalence And Mortality 77
2.6 TECHNIQUES FOR REDUCING EFFECT OF HOT WEATHER ON POULTRY 78
2.6.1 Vitamin C 78
2.6.1.1 Chemical structure. 78
2.6.1.2 Properties of Vitamin C 78
2.6.1.4 Functions of Vitamin C 84
2.6.1.5 Absorption, transport, and disposal of Vitamin C. 86
2.6.1.6 Endogenous production of Vitamin C. 87
2.6.1.7 Ameliorative effects of dietary Vitamin C (L-ascorbic acid) on heat stressed chickens 87
2.6.2 Vitamin E 95
2.6.2.1 Chemical structure. 95
2.6.2.2 Properties Vitamin E. 97
2.6.2.3 Sources of Vitamin E 97
2.6.2.4 Biosynthesis of Vitamin E 97
2.6.2.5 Functions of Vitamin E 104
2.6.2.6 Effects of dietary Vitamin E (dl-alpha tocopheryl acetate) on the performance of heat stressed laying hens 106
2.6.3 Feed Restriction And Heat Stressing Early In Life. 109
CHAPTER THREE
3.0 MATERIALS AND METHODS 110
3.1 LOCATION AND DURATION OF EXPERIMENT 110
3.2 MANAGEMENT OF EXPERIMENTAL ANIMALS 110
3.3 EXPERIMENTAL DESIGN AND LAY OUT 111
3.4 STUDY PROCEDURE. 115
3.5 MEASUREMENT OF PARAMETERS 115
3.5.1 Hen Day Production: 115
3.5.2 Average Daily Feed Intake: 115
3.5.3 Loss in Body Weight. 116
3.5.4 Feed Conversion Ratio: 116
3.5.5. Average Egg Weight (g): 116
3.5.6 Haugh Unit Score (HU): 116
3.5.7 Shell Thickness (mm) 116
3.5.8 Cracked Eggs:. 116
3.5.9 Mortality Rate (%): 117
3.5.10 Economic Analysis of Production 117
3.5.11 Haematological Studies. 117
3.5.12 Meteorological Records 118
3.5.13 Proximate Analysis of Experimental Diet 118
3.5 STATISTICAL ANALYSIS 120
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION 121
4.1. METEOROLOGICAL RECORDS 121
4.2 EFFECTS OF DIETARY VITAMINS C AND E ON PRODUCTION ATTRIBUTES OF GOLDEN NESLINK LAYING HENS IN THE HUMID TROPICS. 121
4.2.1 Hen Day Production 121
4.2.1 Feed Intake 128
4.2.3. Feed Conversion Ratio, FCR. 131
4.2.4 Egg Weight 132
4.2.5 Shell Thickness 135
4.2.6 Cracked eggs 141
4.2.7. Haugh unit score (HUS) 145
4.2.8 Loss In Body Weight (BWT). 148
4.2.9. Mortality 151
4.2.10 Haematological Values Of Laying Hens Supplemented With Vitamins C And Vitamin E Under Humid Tropical Conditions. 155
4.2.11 Economic Analysis of Egg production 181
CHAPTER FIVE
5.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS 201
5.1 SUMMARY 201
5.2 CONCLUSION 202
5.3 RECOMMENDATIONS 202
REFERENCES 204
APPENDICES 240
LIST OF TABLES
TABLE PAGE
Table 1. Standard dimensions of an average egg. 9
Table 2. The Proportions and solids contents of an average egg. 10
Table 3.The composition of egg yolk. 14
Table 4. Albumen types of a normal egg. 19
Table 5. Weight classes and internal features of eggs. 25
Table 6. Class of layers with high quality egg producing traits. 28
Table 7 Avoidable and un-avoidable stressors. 36
Table 8. A guide to the performance of poultry at various temperatures. 44
Table 9. Methods of Sensible and Latent Body Heat Loss. 45
Table 10. Recommended stocking density of laying hens with increasing in indoor temperatures. 51
Table 11. Fatty acid content of different oils. 54
Table 12. Negative effects of vitamin deficiencies. 57
Table 13. Mineral effects in poultry nutrition. 58
Table 14. Effect of temperature on feed intake of laying hens, regardless of value for metabolizable energy in diet. 64
Table 15. Mean blood values for various species of domestic animals. 73
Table 16. Range of haematological values for chickens. 74
Table 17. Physico-chemical properties of Vitamin C. 81
Table 18. Plant sources of Vitamin C. 82
Table 19. Animal sources of Vitamin C. 83
Table 20. Number of families of mammals having at least 1 species with site of Vitamin C synthesis indicated. 89
Table 21. Homologues of tocopherols and tocotrienols. 98
Table 22. Physico-chemical properties of Vitamin E. 100
Table 23. Plant sources of Vitamin E. 101
Table 24. Animal sources of Vitamin E. 102
Table 25. Ingredient composition of the experimental diet. 112
Table 26. Proximate nutrient composition of the basal diet. 113
Table 27. Experimental layout. 114
Table 28. Mean monthly environmental temperatures and relative humidity (RH) recorded during the period of study. 122
Table 29. Effects of dietary Vitamins C and E on Hen day production, HDP (%). 124
Table 30. Effects of dietary Vitamins C and E Feed intake (g/bird/day). 129
Table 31. Effects of dietary Vitamins C and E on Feed conversion ratio. 133
Table 32. Effects of dietary Vitamins C and E on egg weight (g). 137
Table 33. Effects of dietary Vitamins C and E on shell thickness (mm). 139
Table 34. Effects of dietary Vitamins C and E on cracked eggs (%). 143
Table 35. Effects of dietary Vitamins C and E on Haugh unit score (%). 146
Table 36. Effects of dietary Vitamins C and E on loss in body weight (g). 149
Table 37. Effects of dietary Vitamins C and E on mortality (%). 152
Table 38. Summary of dietary effects of Vitamins C and E on production attributes of Golden Neslink laying hens in the humid tropics. 154
Table 39a. Effects of dietary Vitamins C and E on RBC count (x 106). 156
Table 39b. Effects of dietary Vitamins C and E on Haemoglobin concentration (g/dl). 159
Table 39c. Effects of dietary Vitamins C and E on packed cell volume (%). 161
Table39d. Effects of dietary Vitamins C and E on white blood cell (WBC) count (/mm3). 163
Table 39e. Effects of dietary Vitamins C and E on Lymphocytes count (%). 166
Table 39f. Effects of dietary Vitamins C and E on Heterophils count (%). 168
Table 39g. Effects of dietary Vitamins C and E on Eosinophils count (%). 170
Table 39h. Effects of dietary Vitamins C and E on Mean Corpuscular Haemoglobin Concentration, MCHC (%). 174
Table 39i. Mean Corpuscular Haemoglobin, MCH (%). 176
Table 39j. Effects of dietary Vitamins C and E on Mean Corpuscular Volume, MCV (%). 178
Table 40. Summary of dietary effects of Vitamins C and E on haematological values of Golden Neslink laying hens in the humid tropics 180
Table 41a. Total feed consumption tones/bird/week. 182
Table 41b. Total feed consumption (kg)/week. 184
Table 41c. Total feed consumption /dozen eggs (Kg). 186
Table 41d. Total egg production (dozens). 188
Table 41e. Cost of vitamin treatment /kg diet (N). 192
Table 41f. Total feed cost /dozen eggs (N). 194
Table 41g. Egg revenue at N240/dozen eggs (N). 196
Table 41h. Net income/dozen eggs (N). 198
Table 42. Summary of economic analysis of production on effect of dietary Vitamins C and E on production attributes of Golden Neslink laying hens in the humid tropics. 200
Table –X Prevailing prices of feedstuffs used for the study as at 2009. 248
LIST OF FIGURES
FIGURE PAGE
Figure 1.Schematic of endocrine aspects of physiological stress. 38
Figure 2. Importance of continued production of corticosterone during physiological stress. 40
Figure 3. Radiation, convection and evaporation with increasing house temperature. 46
Figure 4. Method of heat loss from birds as temperature changes. 47
Figure 5. Hen body temperature adaptation to high temperatures. 50
Figure 6. Chemical structure of Vitamin C . 80
Figure 7. Production of L- ascorbate from glucose in the liver or kidney of vertebrates. 90
Figure 8. Chemical structure of Vitamin E 96
Figure 9. Structure of tocotrienol. 99
Figure 10. Endogenous production of Vitamin E. 103
Figure 11. Average daily indoor and outdoor temperatures (oC) and relative humidity (%) of the study area from Nov.2008 – Oct. 2009. 123
Figure 12. Hen day production. 125
Figure 13. Feed intake. 130
Figure 14. Feed conversion ratio. 134
Figure 15. Egg weight. 138
Figure 16. Shell thickness. 140
Figure 17. Cracked eggs. 144
Figure 18. Haugh unit score. 147
Figure 19. Loss in body weight. 150
Figure.20 Percentage contribution of individual treatments to total mortality. 153
Figure 21. Red blood cell, RBC (Erythrocyte) count. 157
Figure 22. Haemoglobin concentration. 160
Figure 23. Packed cell volume (PCV). 162
Figure 24. Total white blood cell, WBC (Leucocytes) count. 164
Figure 25. Lymphocytes count. 167
Figure 26. Heterophils count. 169
Figure 27. Eosinophils. 171
Figure 28. Mean Corpuscular Haemoglobin Concentration, (MCHC). 175
Figure 29. Mean Corpuscular Haemoglobin, (MCH). 177
Figure 30. Mean Corpuscular Volume (MCV). 179
Figure 31. Total feed consumption (tonnes). 183
Figure 32. Total feed consumption (Kg). 185
Figure 33. Total feed consumption/ Doz. eggs (Kg). 187
Figure 34. Total egg production (Dozens). 189
Figure 35. Cost of vitamin treatment /kg diet (N) 193
Figure 36.Total feed cost / Doz. egg. 195
Figure 37. Egg revenue at N240/Doz. egg. 197
Figure 38. Net income/dozen eggs (N). 199
LIST OF PLATES
PLATE PAGE
Plate 1. Structure of an egg. 2
Plate 2.The urinary and reproductive organs of the male chicken. 22
Plate 3. Diagram of the avian female reproductive organs. 23
CHAPTER ONE
1.0 INTRODUCTION
Human diets in tropical countries such as Nigeria are most often protein-poor, both quantitatively and qualitatively (Okeke et al., 1985; Ojewola, et al., 2004). For instance, the contemporary average per capita protein consumption in Nigeria is estimated at 7-10g (Oluremi et al., 2008; Okuneye, 2002). This estimate falls far below the FAO (1997) recommendation of 35g/caput/day. Meanwhile, it should be borne in mind that the Nigerian population on the other hand, continues to rise. Current demographic figures show that the total head count overshoots 140 million at a 3.0% annual growth rate (BBC News, 2006; Nigerian News, 2006), without a corresponding livestock population to match (FAO, 2005). To stabilize this situation, no improvement could be made in this country without an increase in food crops, livestock and fish farming. Even then, from the point of view of quality protein consumed, animal proteins by far outweigh proteins from crop sources (Obioha, 1992). Regrettably, there is a perennial low intake of animal products such as meat, milk and eggs in Nigeria (Onyimonyi, 2002). Unfortunately, these animal products are the major sources of high quality proteins. The implication is that, the nutritional status of the Nigerian population and economic development are inextricably linked. This is a clear indication of the inability of the traditional system of animal agriculture to meet the protein needs of Nigerians creating an avenue for protein malnutrition to persist!
The immediate remedy would thus, involve the massive production of animals with short reproductive cycles such as poultry, pigs and rabbits. But when a quick means of significantly increasing turnover rate thereby modifying farm income and improving animal protein in the human diet is the objective, then poultry becomes the animal of choice (Emeruwah, 1999; Ojewola, et al., 2004).
Apart from these dimensions, Obioha (1992) has earlier demonstrated that poultry are excellent feed converters. Carew et al. (2007) have also shown that, poultry do not suffer social infringement on consumer acceptability like other livestock species such as pigs. The foregoing has triggered the rising demand for poultry products like eggs and meat given their palatability and high nutritional value (CTA, 1987; Ojewola, et al., 2005). These attributes among others, make the poultry industry stand tall amidst rival livestock producing ventures.
However, for poultry to perform its ascribed roles, it is necessary to closely scrutinize the environmental factors that have the capability of frustrating their genetic potentials. Nigeria being a humid tropical country is associated with a myriad of these environmental factors. Sinkalu et al. (2008) have listed these environmental stressors as: deprivation of food and water, high ambient temperatures (AT), relative humidity (RH), high velocity, noise, motion, overcrowding, vibration and mishandling. Among these factors, high AT and RH are the most important meteorological stress factors adversely affecting poultry in general, and laying hens in particular (Asli et al., 2007; Ayo and Sinkalu, 2007; Ayo et al., 2005a; Ramnath et al., 2008).
The ideal temperature (conventionally referred to as the zone of thermo neutrality) under which the performance of laying hens is not adversely affected by temperature has been earlier identified by Oluyemi and Roberts (2000) as 12.8-26.00C. CTA (1987) has however given the thermo neutral zone to be 16 -200C. Anderson and Carter (2007) on the other hand identified the range of thermo neutrality as 12.8 – 23.9 0C. Recent field work by Imik et al. (2009) has narrowed the thermo neutral zone of laying hens to 18- 220C.
Temperatures outside the critical limits of the thermo neutral zone such as those obtained in most humid tropical regions of the World like Nigeria have been reported to constitute heat stress (CTA, 1987; Ensminger et al., 1990; Holik, 2009; Kucuk et al., 2003; Oguz et al., 2010). Under heat stress conditions, poultry perform sub-optimally owing to a reduction in feed intake, egg production, egg weight, Haugh units and yolk index (Asli et al., 2007; CTA, 1987; Freeman and Crapo, 1982; Oguz et al., 2010; Smith, 2006; Smith and Oliver, 1972; Vathana et al,. 2002).
Similarly, some authorities Sahin et al. (2002a, b) and Sinkalu et al. (2008) have demonstrated that metabolic (anabolic) activities of tissue building such as transcription, RNA processes and translation are impaired as a result of heat stress.
Earlier reports point that temperatures exceeding 200C enhance heat production by the birds and this supersedes that dissipated through the various processes of elimination (Lewis and Thomas, 1985). Bains (1996) further reported that heat stress could stimulate the increase in corticosterone and catecholamine secretions. Collaborating the work of Freeman and Crepo (1982), Altan et al. (2003), Gous and Morris (2005), Halliwell and Gutteridge (1989), Klasing (1998), Minka and Ayo(2007), and Seifulla and Borisova(1990) have severally demonstrated that, this biochemical activity elicits the generation of free radicals, which cause lipid per oxidation of cytomembranes. Consequently, the natural antioxidant defense systems of the body are overwhelmed (Altan et al., 2003; Sahota and Gillani, 1996; Shini, 2003; Tauler et al., 2003) due to alterations in haematological values (Dawson and Bortolotti, 1997). Apart from stimulating hypothalamo – hypophyseal adrenocortical axis, high and low temperatures alter the susceptibility of animals including laying hens to infectious diseases (Dohms and Metz, 1991; Ramnath et al., 2008; Siegel, 1985). Holik (2009) reported that the electrolytes balance of the fowl become altered due to panting and mineral excretion increases.
With the prospective climate change predisposed by global warming, the magnitude of the low performance may be worsened (IPCC, 2007; Spore, 2008) especially where no adaptation and mitigation strategies are employed to exempt laying birds from these environmental adversaries (Nombor and Okeke, 2009). Affluence poultry farmers could build poultry houses with open – sides or fit ceiling/asbestos sheets or hang ceiling fans in poultry house roofs as ameliorative measures, these strategies are rather very expensive. The next option therefore, would be the manipulation of layer nutrition to intercept the adverse effects of heat stress.
In this wise, the use of antioxidants especially Vitamin C (L-ascorbic acid) and Vitamin E (dl-α-tocopheryl acetate) as dietary supplements in the nutrition of laying hens under humid tropical regions of the world have been demonstrated to be beneficial and economical (Asli et al., 2007; Balnave and Brake, 2005; Ciftci et al., 2005; Oguz et al., 2010; Panda et al., 2008). Even though birds can synthesis Vitamin C endogenously (Daghir, 1995a; McCuskey, 1985; Wikipedia, 2010), under stress conditions such as low or high environmental temperatures, it becomes inadequate (Kucuk et al., 2003; Oguz et al., 2010; Puthpongsiriporn et al., 2001; Ramnath and Rekha, 2010; Ramnath et al., 2008). As for Vitamin E, Biswas et al. (2010), Bolukbasi et al. (2007), Chan and Decker (1994), and Wikipedia (2008) have emphasized its inability for endogenous synthesis in the fowl hence its requirements must be met from exogenous dietary sources.
The climatic conditions of the South – Eastern Nigeria as depicted in Nsukka and its environs reflect a typical tropical climate. Work by Okonkwo and Akubuo (2007) has revealed an average annual minimum and maximum temperature ranges of 22.00C – 24.70C and 33.00C – 37.00C respectively.
These ranges appear to fall outside the zone of thermo neutrality of laying hens which is 18- 220C as recently defined by Imik et al. (2009). As such, adverse effects of heat stress are suspected to clasp egg production parameters of laying hens in this region.
Given the above therefore, the general objective of this study was to investigate the effects of dietary Vitamins C and E used either singly or in combination on egg production parameters under Nsukka humid tropical conditions.
1.1 SPECIFIC OBJECTIVES
