ABSTRACT
Two experiments were conducted to evaluate the effect of melatonin and lighting regime on physiological responses and reproductive traits of two strains of laying birds using 324 laying birds. Each of the experiments consisted of 162 birds. Experiment I was with Nera Black strain while experiment II was with Isa Brown strain. Each of the experiments was grouped into 9 treatments which were further subdivided into three replicates of six birds each in a 2×3 factorial in a completely randomized design. Melatonin and lighting at three levels were administered to the birds four times weekly for 30 weeks. The three levels of melatonin were 0mg, 5mg and 10mg while lighting were 12 hours, 15 hours and 18 hours daily. Melatonin was dissolved in 2mls warm water and the birds were drenched while 100 watt bulbs were used to provide lighting. Data on physiological, performance, haematological and serum was evaluated. Results from the physiological responses showed that rectal temperature (RT), respiratory rate (RR) and heart rate (HT) were significantly (p<0.05) influenced by both melatonin and lighting regime in the two experiments. Melatonin at 5mg significantly (p<0.05) reduced the RT, RR and HT with values of 41.55oC, 142.56 and 327.11 respectively in experiment I and 40.55oC, 139.44 and 320.22 respectively in experiment II. Melatonin at 5mg significantly (p<0.05) reduced the dust-bathing, feather pecking and panting in both experiments. Lighting regime increased dust-bathing and panting rate in experiment II but not in experiment I. Performance characteristics were significantly (p<0.05) influenced by both melatonin and lighting regime. The hen day egg production, feed conversion ratio and egg weight of 91.66%, 1.73 and 61.52g respectively for experiment II and 84.77%, 1.61 and 70g respectively for experiment I were recorded. This indicates that melatonin at all levels significantly (p<0.05) had superior effects in both experiments compared to lighting. The weight of the reproductive organs and the number of follicles were significantly (p<0.05) improved by melatonin in both experiments. Large yellow follicles and small white follicles increased significantly with increasing level of melatonin in both experiments. The haematological profiles were influenced by the administration of melatonin in both experiments. Significant differences (p<0.05) were observed in most of the serum biochemical parameters in both experiments. Significant (p<0.05) differences occurred in the hormonal profile. 15hrs lighting regime improved the body weight of the birds, size and number of developing follicles in both experiments. Interaction between melatonin and lighting improved the overall performance of the birds as the groups on 5mg of melatonin and 15hrs lighting performed better than the other groups in both experiments. It is therefore concluded that 5mg melatonin and 15 hours of lighting improved hen day egg production and development of follicles in Isa Brown birds. Nera Black on 5mg melatonin and 15 hours lighting had improved body weight gain and immune response thereby enhancing survival rate. It is therefore recommended that 5mg melatonin and 15 hours lighting should be used to enhance egg production and improve the behavioural characteristics of laying birds during thermal stress.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Contents vii
List of Tables xiv
List of Plates xviii
Abstracts xix
CHAPTER 1:
INTRODUCTION
1.1
Background information and knowledge gap 1
1.2 Statement
of Problem 9
1.3 Objective of the Study 10
1.4 Justification
of the Study 11
CHAPTER
2: LITERATURE REVIEW
2.1 Significance
of Additional Light in the Hen House 13
2.2.1 Circadian Rhythm 15
2.2.2 Circadian
Photoreception 16
2.3.1 Lighting Programs for Layers 17
2.4 Effect of Photoperiod on Melatonin Production 19
2.5
Regulating System of the Melatonin Secretion 21
2.6 Mechanisms of Melatonin Production 23
2.7 Endocrine Effects of Melatonin 27
2.8 Metabolism of Melatonin 28
2.9
Animal Welfare 29
2.9.1 Behavioural Welfare 30
2.9.2 Vocalisation Welfare 32
2.10 Endocrine Control of Reproduction 33
2.11
Effect of Behavioural Stress on Poultry 33
2.12 Gonadotropin- Releasing Hormone 34
2.13 Circadian
Rhythm in Avian Species 35
2.14 Melatonin Secretion in Avian Species 36
2.15 Physiology of Melatonin Production 38
2.16 Importance of Melatonin in Poultry
Production 40
CHAPTER 3:
MATERIALS AND METHODS
3.1 Experimental
Site 45
3.2 Experimental
Animals and Management 45
3.3 Experimental
Materials 46
3.4 Experimental
Design 46
3.4.1 Experiment
I: Nera Black Strain (NB) 47
3.4.2 Experiment II: Isa Brown Strain (IS) 47
3.5.1 Experimental
Procedures and Data Collection 48
3.5.2 Physiological
Measurements 49
3.5.3 Performance
Evaluation 50
3.5.4 Egg
quality characteristics 50
3.5.4.1 External egg quality characteristics 51
3.5.4.2 Interior
egg quality characteristics 51
3.5.5 Follicular Dynamics 52
3.5.6 Hormonal
Analysis 53
3.5.7 Haematological
Parameters 53
3.6 Statistical
Analysis 54
CHAPTER 4: RESULTS
AND DISCUSSION
4.1 Main
Effect of Melatonin on Physiological Response of Nera Black 55
4.2 Main
Effect of Light on Physiological Response of Nera Black 56
4.3 Interactive effect of Melatonin and Light
on Physiological Response of
Nera Black 58
4.4 Main
Effect of Melatonin on the Behavioural Response of Nera Black 60
4.5 Main
Effect of Light on Behavioural Response of Nera Black 62
4.6 Interactive effect of Melatonin and Light
on Behavioural Response of
Nera Black 63
4.7 Main Effect of Melatonin on Physiological
Response of Nera Black 65
4.8 Main
Effect of lighting on Performance of Nera Black and Isa Brown 69
4.9 Interactive
Effect of Melatonin and Light on the Performance of
Nera Black 70
4.10 Main Effect of Melatonin on External Egg
Characteristics of Nera Black 73
4.11 Main Effect of Lighting Regime on External
Egg Characteristics of
Nera
Black 74
4.12 Interactive Effect of Melatonin and Light
on the External Egg Characteristics
of Nera Black Laying Birds 76
4.13 Main Effect of Melatonin on Internal Egg
Characteristics of Nera Black 78
4.14 Main
Effect of Lighting Regime on the Internal Egg Characteristics
of Nera Black 80
4.15 Interactive
Effect of Melatonin and Light on Internal Egg Characteristics
of Nera Black 81
4.16
Main Effect of Melatonin on Ovarian
Traits of Nera Black 84
4.17 Main Effect of Lighting Regime on Ovarian
Traits of Nera Black
of
Nera Black 86
4.18 The ovary and follicles from experimental
birds 88
4.19 Interactive Effect of Melatonin and Light
on Ovarian Traits of
of Nera Black 92
4.20 Main
Effect of Melatonin on the Haematology of Nera Black 94
4.21 Main
Effect of Lighting Regime on Haematology of Nera Black 99
4.22 Interactive Effect of Melatonin and Light
on the Haematology
of Nera Black 101
4.23 Main
Effect of Melatonin on Serum Biochemistry of Nera Black 103
4.24 Main Effect of Lighting Regime on Serum
Biochemistry of Nera Black 106
4.25 Interactive Effect of Melatonin and Light
on Serum Biochemistry
of Nera Black 108
4.26 Main
Effect of Melatonin on Hormonal Assay of Nera Black 111
4.27 Main Effect of Light on Hormonal Assay of
Nera Black 113
4.28 Interactive
Effect of Melatonin and Light on Hormonal
Assay of Nera Black 114
4.29 Main
Effect of Melatonin on Physiological Response of Isa Brown 117
4.30 Main Effect of Lightening on Physiological
Response of Isa Brown 119
4.31 Interactive
Effect of Melatonin and Light on Physiological Response
of Isa Brown 120
4.32 Main
effect of Melatonin on the Behavourial Response of Isa Brown 123
4.33 Main Effect of Lighting Regime on
Behavourial Response of Isa Brown 124
4.34 Interactive
effect of Melatonin and Light on Physiological Response
of Isa Brown 125
4.35 Main
Effect of Melatonin on Performance of Isa Brown 127
4.36 Main
Effect of Lighting Regime on Performance of Isa Brown 129
4.37 Interactive
Effect of Melatonin and Lighting Regime on the Performance
of Isa Brown 130
4.38 Main Effect of Melatonin on the External
Egg Characteristics of
Isa Brown 132
4.39 Main Effect of Lighting on the External Egg
Characteristics of
Isa Brown 134
4.40 Interactive Effect of Melatonin and Light
on the External Egg
Characteristics of Isa Brown 136
4.41 Main Effect of Light on Internal Egg
Characteristics of Isa Brown 138
4.42 Interactive Effect of Melatonin and Light
on the Internal Egg
Characteristics of Isa Brown 139
4.43 Main Effect of Melatonin on Ovarian Traits
of Isa Brown 141
4.44 Main
Effect of Light on Ovarian Traits of Isa Brown 143
4.45 Interactive Effect of Melatonin and Light
on Ovarian Traits of Isa Brown 144
4.46 Main
Effect of Melatonin on Haematological Parameters of Isa Brown 146
4.47 Main Effect of Lighting Regime on
Haematological Parameters
of Isa Brown 149
4.49 Interactive Effect of Melatonin and Light
on Haematological parameters
of Isa Brown 151
4.50 Main Effect of Melatonin on Serum
Biochemistry of Isa Brown 153
4.51 Main
Effect of Light on Serum Biochemistry of Isa Brown 156
4.52 Interactive
Effect of Melatonin and Light on Serum Biochemistry
of Isa Brown 157
4.53 Main
Effect of Melatonin on Hormonal Assay of Isa Brown 160
4.54 Main
Effect of Lighting Regime on Hormonal Assay of Isa Brown 161
4.55 Interactive
Effect of Melatonin and Light on Hormonal Assay
of Isa Brown 163
CHAPTER
5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 165
5.2 Recommendation 167
References
169
Appendixes 192
Appendix
1: Administration of melatonin 192
Appendix
2: Measuring of Egg Internal Quality 192
Appendix
3: Measuring of Feed 193
Appendix
4: Taking Physiological Measurement 193
Appendix
5: Measuring of External Egg Quality 194
Appendix
7: Blood Collection 194
Appendix
8: Counting of Ovarian Follicles 195
Appendix
9: Student with Supervisor 196
Appendix
10: Analysis of Variance Using Mini Tab 197.
LIST
OF TABLES
3.1 Experimental Layout 46
4.1 Main
values of the Physiological Response of Nera Black 55
4.2 Main of
the Effect of Light on Physiological Response of Nera Black 56
4.3
Interactive effect of Melatonin and
Light on Physiological Response 59
4.4 Main of the Effect of Melatonin on
Behavioural Responses of Nera Black 61
4.5
Main of the Effect of Lighting
Regime on Behavioural Responses of
Nera Black 62
4.6 Interactive effect of Melatonin and Light on
Behavioural Responses of
Nera Black 64
4.7 Main of
Melatonin on Performance Evaluation of Nera Black 66
4.8 Main of
light on Performance Evaluation of Nera Black 69
4.9 Main
Interactive Effect of Melatonin and Light on the Performance of
Nera Black 72
4.10 Main of Melatonin on External Egg Characteristics
of Nera Black 73
4.11. Mean of lighting Regime on External Egg
characteristics of Nera Black 75
4.12 Mean of the Interactive Effect of Melatonin and
Light on the External Egg
Characteristics of Nera
Black 77
4.13 Mean Effect of Melatonin on the Internal Egg
Characteristics of
Nera Black 79
4.14 Mean Effect of Lighting Regime and Internal Egg
Characteristics of
Nera Black 80
4.15 Mean Interactive Effect of Melatonin and Light on
the Internal Egg
Characteristics of Nera
Black 83
4.16 Mean
Effect of Melatonin on Ovarian Traits of Nera Black 84
4.17 Mean
Effect of Lighting Regime on Ovarian Traits of Nera Black
of Nera Black 87
4.18 Mean
Interactive Effects of Melatonin and Light Ovarian Traits
of Nera Black 93
4.19 Effect of Melatonin on the Haematology of Nera
Black 95
4.20 Mean
Effect of Lighting Regime on Haematology of Nera Black 100
4.21 Interactive
effect of melatonin and light on the haematology
of Nera Black 102
4.22 Main
effect of melatonin on serum biochemistry of Nera Black 104
4.23 Main
effect of Lighting Regime on serum biochemistry of Nera Black 107
4.24 Main
effect of melatonin and light on serum biochemistry of Nera Black 110
4.25 Main
Effect of Melatonin on Hormonal Assay of Nera Black 111
4.26 Main
Effect of Light on Hormonal Assay of Nera Black 113
4.27 Main
Effect of Melatonin and Light on Hormonal Assay of Nera Black 116
4.28 Main of
the physiological response of Isa Brown 117
4.29 Main of
the Effect of Lighting on Physiological Response of Isa Brown 119
4.30
Interactive effect of Melatonin and Light on Physiological Responses
of Isa Brown 122
4.31 Main of
the effect of Melatonin on Behavioural Responses Isa Brown 123
4.32 Main of
the Effect of Lighting Regime on Behavioural
Responses Isa Brown 124
4.33
Interactive effect of Melatonin and Light on Physiological Response
of Isa Brown 126
4.34 Main of
Melatonin on Performance Evaluation of Isa Brown 127
4.35 Main of
lighting Regime on Performance Evaluation of Isa Brown 129
4.36 Main
Interactive Effect of Melatonin and Lighting Regime on Isa Brown 131
4.37 Main of
Melatonin on the External Egg characteristics of Isa Brown 133
4.38 Main of
Lighting Regime on External Egg characteristics of Isa Brown 134
4.39 Main
Interactive Effect of Melatonin and Light on the external egg
of Isa Brown 137
4.40 Main
effect of melatonin on the internal egg characteristics of Isa Brown 138
4.41 Main Effect
of Light on Internal Egg Characteristics of Isa Brown 140
4.42 Main
Interactive effect of melatonin and light on the Internal Egg
Characteristics of Isa
Brown 141
4.43 Main
Effect of Lighting Regime on Ovarian Traits of Isa Brown 143
4.44 Main
Effect of Lighting Regime on Ovarian Traits of Isa Brown
of Isa Brown 144
4.45 Main
Interactive Effects of Melatonin and Lighting Regime
Ovarian Traits of Isa
Brown of Isa Brown 145
4.46 Main
effect of melatonin on Haematological Parameters of Isa Brown 147
4.47 Main
effect of lighting Regime on Haematological Parameters
of Isa Brown 150
4.48 Main
Effect of Melatonin and Light on the Haematological
Parameters of Isa Brown 152
4.49 Main
Effect of Melatonin on Serum Biochemistry of Isa Brown 154
4.50 Main
effect of Light on serum biochemistry of Isa Brown 156
4.51 Main
Effect of Melatonin and Light on Serum Biochemistry
of Isa Brown 159
4.52 Main
Effect of Melatonin on Hormonal Assay of Isa Brown 160
4.53 Main
Effect of Lighting Regime on Hormonal Assay of Isa Brown 161
4.55 Main
Effect of Melatonin and Light on Hormonal Assay of Isa Brown 163
LIST
OF PLATES
Plates Page
1.
Ovary and follicles of
Nera Black on 5 mg of melatonin 89
2.
Ovary and follicles of
Nera Black on 10 mg of melatonin 89
3.
Ovary with follicles of
Isa Brown on 10 mg of melatonin 89
4.
Ovary with follicles of
Isa Brown on 5 mg of melatonin 89
5.
Follicles of Nera Black on
15 hours of lighting 91
6.
Follicles of Isa Brown on
15 hours of lighting 91
7.
Follicular weight of Nera
Black 91
8.
Follicular weight of Isa
Brown 91
CHAPTER 1
1.0 INTRODUCTION
1.1 Background
information and Knowledge Gap
Population
growth, rising incomes and urbanization are the
driving forces behind poultry sector growth. Growing demand for livestock
products will also have a negative impact on the environment (FAO, 2006). Economic losses are incurred by the livestock
industries because farm animals are raised in locations and seasons where
effective temperature conditions venture outside their zone of thermal comfort (St.
Pierre et al., 2003). Poultry houses that do not
have appropriate ventilation during extreme hot conditions, results in
overheating of sheds, and thus causes heat stress to birds (Akyuz, 2009). In
addition to high ambient temperature, relative humidity also plays an important
role in bringing out stress in the chickens leading to production and economic losses
(Ajakaiye et al., 2011).
These
losses are heavily incurred in animals like dairy cows, dairy heifers, beef
cows, finishing cattle, sows, market hogs, broilers, layers, and turkeys and it
contribute much economic loss in livestock production. In USA, St Pierre et al (2003) noted
that, economic losses, in the layers sector are very high due to heat stress and
when the heat stress were reduced, it was observed that the losses also reduced
The economic losses
can be estimated from the following:
i.
Decreased performance (feed
intake, growth, milk, eggs): Once the feed consumption drops, other production
parameters like hen day egg production, milk yield and growth rate of the
animals also drops leading to loss of production.
ii.
Increased mortality: adequate feeding improves the immune response of
animals as some of the nutrients plays significant roles in improving the
health status of the animals. As the health status gets improved mortality rate
also reduces, on the other hand compromised immune response leads to high
mortality rate leading to production losses.
iii.
Decreased reproductions: lack of conception as a result of poor
management leads to indirect production loss.
High ambient temperature is one of the major problems
facing poultry production mostly in hot climate areas. Its debilitating effect
on egg production is well recognized, but the mechanism involved is not clearly
understood. Reduced feed consumption may account for part of the impairment in
reproduction; however, the effect of high environmental temperatures on the
rate of egg production appears largely unrelated to feed intake (Ayo et al., 2010). When
environmental temperature exceeds the limits of thermoneutral zone, body
temperature of the animal increases leading to distress in animal. Prolonged
heat stress results in dramatic physiological changes in chicken organs
especially in broiler birds, these changes are used as indicators of heat
stress (Melesse et al., 2011). Research on heat stress in laying hens is not
entirely consistent regarding its effects on percent hen-day production, but
results show a consistent decrease in egg weight and shell thickness (Muiruri
and Harrison, 1991; Wolfenson et al.,
2001). Reduction in egg numbers, egg weight and
shell thickness has been reported during heat stress. An interesting finding by
Wolfenson et al. (2001) was that the productivity decreases
only when hens experienced nocturnal heat stress but not experienced during day
time. Hen-day egg production was significantly decreased through all 13 weeks
for hens exposed to the constant hot temperature compared with those in the
control group (Allahverdi et al., 2013). In layers, peak
production may not be achieved and the eggs produced will be soft shelled and
weigh less with poor egg size quality and shell strength (Faria et al., 2001).
Chronic heat stress is either categorized as cyclic chronic heat stress which
refers to a limited period of heat stress exposure followed by comfortable
temperature for the rest of the day or constant chronic heat stress where by
the bird is continuously confronted with high ambient temper. Khan et al. (2012) noted that the
physiological, endocrine and productive responses are adversely affected by
heat stress. When such physiological disturbances take place, it even leads to
increased mortality (Sandhu et al., 2012). There is acid-base
(Imik et al., 2013), electrolytes imbalance (Borges et
al., 2004) and these disturbances are due to increased respiration rate
(Renaudeau et al., 2011). Increased panting under heat stress
conditions leads to decreased blood carbon dioxide levels and higher blood pH
(alkalosis) that in turn hampers blood bicarbonate availability for egg shell
mineralization. Osmotic change and dehydration are due to the result of water
imbalance which in turn affects the cell performance negatively (Sahin et
al., 2002). This blood alkalosis affects the neuroendocrine system.
This system gets stimulated under the effect of stress. The hypothalamic
neurons perceive the increases in body temperature and exert an inhibiting
influence on cells that are responsible for controlling feed intake. The two
major systems are hypothalamic pituitary axis and the sympathetic nervous
system. The hormones corticosterone, catecholamines like epinephrine and
norepinephrine secreted by the above mentioned systems, act on the immune
cells. It is well known that immune cells have receptors for these hormones
(El-Lethay et al., 2003). The down regulation of immune
response to stress reduces resistance of the body to microbes (Dohms and Metz,
1991). Studies by El-Lethey et al (2003) in White Leghorns revealed
that there are stress resistant and stress susceptible antibody responses.
Heterophils, granulocytes in chicken exhibit different functions when
stimulated such as phagocytosis (Genovese et al., 201) and
produce extracellular traps (Chuammitri et al., 2009). The
extracellular traps are formed by de-condensed chromatin fibers, contain
antimicrobial peptides released by granules of neutrophils
(Donis-Maturano et al., 2015) which trap and kill
microorganisms. But if this process continues it kills antigen presenting cells
such as macrophages and dendritic cells. This is for controlling the
inflammatory process (Donis-Maturano et al., 2015). The most
reported effect of stress is the suppression of immune organs and immune cells
(Shini, 2004; Shini et al., 2008a). The hormone whose
concentration gets elevated in plasma due to stress is corticosterone, is well
documented in birds resulting in increase in the number of heterophils and
decrease in the number of lymphocytes thus, favoring higher ratio for
heterophils which has been well studied (Shini et al., 2008). The
regulatory mechanisms for the reduced reproductive efficiency in the
heat-stressed hen might be modulated at the level of the hypothalamus and
pituitary or at the level of the ovary as found in mammalian species. Heat
stress decreased ovarian function in cattle Wolfenson et al. (1997), suggesting a differential inhibitory effect of heat
stress on the functions of granulosa and theca cells by concurrent and delayed
effects on the steroidogenic capacity of ovarian follicles. Changes in
reproductive hormone secretion represent the final sequence in the
neuroendocrine pathway leading to the diminished reproductive performance
associated with stress. Rozenboim et al.,
(2004) demonstrated that stress, in a number of forms and in a number of
species, increased and decreased circulating prolactin (PRL) and gonadotropins
(luteinizing hormone, LH; follicular stimulating hormone, FSH), respectively
especially in cows and goats, turkey poults, laying hens, and turkey hens.
There is also a marked alteration in sperm function of
broiler breeder males exposed to high temperatures, which results in poor
sperm-egg penetration, low fertility and a lower fertilization rate (Karaca et al., 2002). Various methods are
available to alleviate the negative effect of high ambient temperature on
performance of poultry. Because of the high cost of cooling poultry houses,
diet manipulations short term fasting in layers Altan et al. (2000) and broilers acclimation to heat during pre and post
natal periods had great interest to reduce heat stress on poultry during the
hot dry season. Studies have shown that antioxidant nutrient supplementation
such as ascorbic acid and melatonin could be used to decrease the negative
effects of high ambient temperature on quails (Sahin et al., 2004). Sinkalu et al.
(2008), noted that atmospheric temperature in poultry houses during the hot-dry
season in the zone fluctuated markedly between 16-41oC.
Consequently, several physiological parameters of broiler breeders raised
during the season may vary as the hour of the day increases.
It is pertinent to note that whenever the homeostatic
mechanisms of birds are activated, extra energy is expended in the process. The
energy so extended is no longer available for production process. Generally
broilers both breeders and non breeders react to heat stress condition by
eating less feed, thus controlling the rise in deep body temperature caused by
digestion. The resultant effect is
impaired growth, decreased egg production, poor quality eggs, low hatchability
of the eggs and low quality of semen produced which in turn affect the
fertility rate of the egg. The survivability of the progeny of such breeder is
also affected. Broilers whether breeders
or broiler chicken normally do not eat during darkness as long as this period
does not extend for more than 12 hours. But breeders need additional light to
stimulate egg laying. Therefore, it is assumed that feed intake and production
are maximal for breeders that are reared in continuous illumination (Aperdoorn et al., 1999). This practice depletes
the reserves of the endogenous antioxidant, melatonin in broilers. Seasonal
sterility has been observed in mammalian species affected by high ambient
temperatures.
Various
methods are available to alleviate the negative effect of high ambient
temperature on performance of poultry. Therefore, due to high cost of cooling poultry houses, diet manipulations
(Altan et al., 2000a), short term
fasting in breeder layers (Altan et al., 2000b) and broilers (Özkan et al., 2003) , there is a need to
investigate use of melatonin as an antioxidant.
The production
and secretion of melatonin encodes a photoperiodic calendar to birds as they
exhibit changes in both the duration and amplitude of melatonin secretion
corresponding to the duration of night length/ day length (Aperdoorn et al., 1999). Since lighting affect melatonin secretion and light is also necessary
to enhance feeding and photoperiod which enhance egg laying, melatonin and
lighting will be combined in this study to see its effect on the physiological
responses and reproductive performance of the laying birds.
Pineal
gland acts as a photoneuroendocrine transducer that responds through melatonin
release. Melatonin (C13H16N2O2) is
the main neurohormone synthesized and released by the pineal gland. This
hormone appears to be a potent free radical scavenger opposing the most toxic
hydroxyl radical (Webb et al., 1995;
Zang et al., 1998). Besides its
ability to directly neutralize a number of free radicals and reactive oxygen
and nitrogen species, it stimulates several antioxidative enzymes which
increase its efficiency as an antioxidant (Reiter et al., 2000). It is
one of the important hormones that prevent metabolic and physiological
disorders in poultry but does not attract attention by poultry scientist
(Suleyman et al., 2018). It regulates
the brain's biological clock, acts on respiration, circulation, excretion,
reproduction and immunity system. Melatonin helps regulate feed consumption,
energy metabolism and body heat. It also provides elimination of free radicals
in the body. It also stimulates growth hormone secretion and, thus, effects
growth performance of poultry positively (Suleyman et al., 2018). It sets the internal biological clock that
regulates different daily and seasonal rhythms in various physiological systems
including the cardiopulmonary, reproductive, excretory, thermoregulatory,
behavioural, immune and neuroendocrine systems in birds (Brennan et al., 2002; Melamud et al., 2012) In addition to its ability
to scavenge free radicals, melatonin also is involved in many physiological
functions such as immune response, energy metabolism and temperature regulation
(Sahin et al., 2004). Many studies
have shown that melatonin plays an important role in animal reproduction. It
could enhance the maturation of oocytes and the development of follicles in
mammals and fish (Sahin et al.,
2004). Despite the great differences between birds and mammals, melatonin may
play a similar role in the maturation of oocytes and the development of
follicles in birds as it does in mammals. In other words, it is hypothesized
that melatonin is directly involved in the growth and maturity of oocytes as
well as in the inhibition of factors which might impair the quality of oocytes.
In photoperiodic vertebrates,
the annual cycle of reproduction is controlled principally by changing day
length, a highly predictive cue of seasonal resource abundance. In all diurnal
vertebrates studied, melatonin is synthesized in and secreted from the pineal
gland during night (Sundaresan et al., 2009) such that the timing and duration of
melatonin secretion provide an endocrine proxy of changes in day length (Sundaresan et al.,
2009). In mammals,
melatonin stimulates reproductive physiology and activity in short day breeders
and inhibits reproductive physiology and activity in long-day breeders.
Consequently, manipulating the duration of melatonin secretion experimentally
causes changes in reproductive physiology in photoperiodic mammals. Layers have been submitted to genetic improvement to
produce more eggs at a lighter body weight and with lower feed intake. As a
result, egg operations need to face the challenges of supplying the high
nutritional requirements of layers and of designing management practices
adapted to the increasingly automated and environmentally controlled facilities
and to high stocking densities.
An aspect of the physiology of egg-laying in poultry
is that they do not require long and continuous periods of light. This
phenomenon is called "subjective day", which indicates that adult
hens in lay ignore periods of dark between the 14-16 hours of light
stimulation. Subjective day is the period during which the bird is awake and
physiologically active, even if it is in the dark. This allows the use of
intermittent lighting programs for laying hens, which are programs that include
more than one period of light (photophase) and one period of dark (scotophase)
within a 24-h cycle (Gewehr and Freitas, 2007; Freitas et al.,
2010). In
photoperiodic birds, the relationship between melatonin signal and reproductive
timing is more complex than in photoperiodic mammals. In seasonally breeding
birds, a prolonged exposure to short days induces a physiological state termed
“photosensitivity” (Chabot and Menaker 1992). When photosensitive birds
experience a critical day length, the hypothalamic-pituitary-gonadal axis
becomes stimulated, and gonadal recrudescence and initiation of reproductive
behaviors occurs (Kumanov et al., 2005; Lewis et
al., 2006). Because
melatonin provides a measure of changing day length, and day length is a
primary cue in mediating the transition to photostimulation (from
photosensitivity), it seems likely that melatonin could be involved in the
event.
Underwood and Siopes (1985) highlighted three reasons why melatonin
has been of interest to researchers. These include:
·
Melatonin was the first
methoxyindole identified
·
Historically, melatonin
was thought to be a unique pineal product since the enzyme responsible for the
last step in its synthesis, hydroxyindole-Omethyltransferase (HIOMT) was
thought to be confined to pineal tissue
·
Melatonin has been shown
to be involved in controlling circadian and photoperiodic systems.
·
Melatonin is involved in
physiology of reproduction especially in seasonal breeders.
Therefore,
the present study is designed to determine the effect of oral administration of
melatonin and lighting regime on physiological responses and reproductive
performance of two breeds of commercial laying birds during hot dry seasons.
1.2 Statement of Problem
Ebonyi
State is classified under the Guinea Savannah zone of Nigeria characterized by
intensive heat stress during the hot-dry season which usually lasts from October
to March (Oformata, 1997). The hot dry season is characterized by long day
length and hot dry air which makes it difficult for exotic animals in this
micro-environment to survive. This is one of the major reasons why in
South-East Nigeria especially Ebonyi state breeder farms establishment is
almost a mirage. In warmer
regions, high ambient temperature are the major problem facing the egg
production industry, since they adversely affects feed intake, egg production,
egg quality, antioxidants status, physiological traits and, therefore, the
overall profit of poultry farms (Mashaly et
al., 2004).
Seasonal
decline in production of poultry products like chicken and egg necessitated the
need to combine melatonin and lighting to mitigate the effect of hostile
environment and improve production within this region.
1.3 Objective of the Study
The
main objective of this study was be to evaluate the effect of melatonin and
different lighting regime on the physiological responses and reproductive
performance of two breeds of laying birds (Isa brown and Nera Black) during
hot-dry season.
The specific
objectives were to determine:
i. the
effect of orally administered melatonin on the physiological responses of the
two strain of laying birds during hot-dry season.
ii. the
effect of orally administered melatonin and extended light period on the growth
and production performance of the two strain of laying birds during hot-dry
season.
iii. the behavioural responses of two the strains of
laying birds administered with melatonin and extended light period during
hot-dry season.
iv. the
effect of orally administered melatonin and extended light period on the
haematology and serum biochemistry of the two strains of laying birds during
hot-dry season.
v. the
effect of orally administered melatonin and extended light period on the
follicular dynamics of the two strains of laying birds during hot-dry season.
vi. the effect of orally administered melatonin
and extended light period on the egg quality of two the strains of laying birds
during hot-dry season.
vii. the
hormonal profile of selected reproductive hormones of laying birds orally
administered with melatonin and extended light period during hot-dry season.
1.4 Justification of the Study
Poultry
is fast becoming an important source of income and employment to poultry
operators, likewise a sustainable source of animal protein to consumers in
Nigeria. With the current security challenges facing the country especially
Northern Nigeria, there are urgent needs to expand poultry industry. Poultry
meat and egg offer considerable potential for meeting basic animal protein
requirement for humans. The prevailing global climatic warming also poses a
serious threat to the industry due to thermal stress imposed on the chicken.
Melatonin
and its receptors were found to be present in the ovary. It has been demonstrated that feeding
melatonin to 70- 73-week-old layers resulted in a highly significant decline in
heat production and increased egg production (Zeman et al., 2001) due to the antioxidant properties present in
melatonin. Melatonin may be a key factor in the regulation of seasonal
variation in gonadal activity. Exposure to bright light and increasing the
concentration of melatonin in circulation is hypothesized to be useful in
treatment of both male and female infertility. Experimental studies and
clinical trials have shown that melatonin turned out to be effective than
classical antioxidants to reduce the oxidation of lipids (Rodriguez et al., 2007; Maldonado et al., 2012). It also preserves the
levels of glutathione in cells and mitochondria which helps to suppress oxidative
damage at these sites (Acuna-Castroviejo et
al., 2011; Escames et al., 2012).
In the oocyte, melatonin scavenges free-radicals and acts as an anti oxidative
substance, hence the need to combine melatonin and lighting in improving egg
production and quality in laying birds.
Results
from this study were used in making recommendations to poultry farmers
particularly commercial layers farmers on the use of melatonin and extended light
period to enhance egg production, improve the welfare of the birds and finally
maximize profit.
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