TABLE OF CONTENTS
CONTENT PAGE
TITLE PAGE …………………………………………………………………………………………………………….. ii
CERTIFICATION ……………………………………………………………………………………………………..iii
DEDICATION ………………………………………………………………………………………………………….. iv
ACKNOWLEDGMENTS …………………………………………………………………………………………… v
ABSTRACT …………………………………………………………………………………………………………….. vii
TABLE OF CONTENTS …………………………………………………………………………………………..viii
LIST OF TABLES ……………………………………………………………………………………………………xiii
LIST OF FIGURES ………………………………………………………………………………………………….. xv
LIST OF PLATES ………………………………………………………………………………………………….. xvii
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
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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
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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
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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
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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
CHAPTER ONE
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
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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
3
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.
4
1.1 SPECIFIC OBJECTIVES
This study was designed to:
(a) determine the levels at which Vitamin C supplementation will optimally improve
production in laying hens under heat stress.
(b) determine the dietary levels of Vitamin E that will enhance layer performance under
humid tropical conditions.
(c) establish any synergetic relationship that may arise between Vitamin C and Vitamin E
used in combination to improve the performance of laying hens in the humid tropics
(d) investigate the effect of Vitamins C and E as antioxidants on hematological values of
laying hens.
(e) determine the economic benefits of dietary Vitamins C and E fed to laying birds under
heat stress.
1.2 JUSTIFICATION OF THE STUDY
Among the topical issues on the “Yar Adua’s” 7 point – agenda is food security
reforms primarily geared towards revolutionizing the agricultural sector leading to a 5 – 10
fold increase in yield and production (Aluko, 2007). Given Nsukka’s tropical conditions,
research in this zone directed towards increasing egg production is worthwhile in the
realization of the goals of the 7 point – agenda as far as food security is concerned.
Secondly, University of Nigeria, Nsukka has made previous attempts towards
environmentally modifying the poultry Unit (by building open – sided houses) so as to record
commercial benefits. This attempt may direct air movement onto the floor. And even if
ceiling/asbestos sheets together with fans were to be fitted in the roofs, much still remain on
the manipulation of the nutritional requirements of the birds if optimum performance is to be
achieved.
Thirdly, Okonkwo and Akubuo (2007) have given the average annual minimum and
maximum temperature ranges in Nsukka as 22.00C – 24.70C and 33.00C – 37.00C
respectively. (Note sharp changes in corresponding figures of 200C-230C and 270C -320C as
earlier reported by Breinholt et al. (1981). This increase in air temperatures might probably
be as a consequent of global warming. These temperature ranges indicate that laying hens at
Nsukka are experiencing temperatures above the comfort zone most of the time unnoticed. In
the present face of climate change, this research is worth undertaking.
5
More so, dietary Vitamins C and E have not been shown to have residual but
beneficial effects on treated animals unlike antibiotics, hormones and other growth
promotants whose use in livestock nutrition is at present discouraged (Schell, 1984).
Lastly, since this work is a maiden attempt in this location, data generated from the study will
provide baseline information upon which subsequent investigation will be based.
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