ABSTRACT
This study was conducted to investigate the development of the Helmeted Guinea fowl (Numida meleagris) gastrointestinal tract at pre- and post-hatch. One hundred and seventy five (175) eggs were purchased from the Poultry unit of National Veterinary Research Institute (NVRI), Vom out of which one hundred and thirty five (135) were used for pre-hatch and forty were allowed to hatch for post hatch studies. The samples were studied grossly, morphometrically, and microscopically. The result revealed that at day 8 of development a digestive tube appeared with a roundish structure in the middle of the tube. By day 10 of development, a dilatation had appeared cranial to the roundish structure identified as the proventriculus. At the same time a small outgrowth appeared at the caudal end of the tube also identified as one of the caeca. By day 11 of development, the crop had appeared separating the oesophagus into cervical and thoracic parts, respectively. By days 12 and 13 of development the second caecum and the duodenal loop became apparent with the appearance of the duodenal loop which marks the end of the gross anatomical development of the guinea fowl GIT. The study concludes that it took 6 days for the completion of gross anatomical development of the guinea fowl GIT. This study also revealed that the crop and the proventriculus did not follow craniocaudal pattern of development. The morphometric study revealed that there were positive correlation between the measured parameters at both pre and post-hatch. The r values between the body weight (BWT) versus GIT weight (GWT), between the BWT versus GIT length (LGT) as well as between the GWT versus LGT were 0.42, 0.96 and 0.95, respectively for pre-hatch while the r values of 0.70, 0.50 and 0.85 were for post-hatch respectively. The histological study revealed that the oesophagus was lined by simple columnar epithelium at the early embryonic life and then changed to stratified squamous epithelium with the oesophageal glands appearing
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in the submucosa by day 19 of development. The histology of the crop is similar to that of the oesophagus. The proventricular gland has the most prominent histological feature of the proventriculus with the primordial gland at the embryonic stage developing progressively through pre and post-hatch. The intestine has the typical mucosal lining which was pseudostratified initially but eventually changed to columnar epithelium with numerous villi at the small intestine. No goblet cells were found in the intestinal tract before hatching but appeared at post-hatch. This is a specific feature of this avian species. The residual yolk decreased with age until it became vestigial by day 8 post-hatch. The results of this study confirm previous reports on the GIT development that its growth and the digestive function are not fully formed in newly hatched birds. The study also revealed that days 8-13 of development are the most critical periods for the gross formation of the GIT in the guinea fowl when congenital malformation can
TABLE OF CONTENTS
Title page ——————————————————————————————-ii Declaration —————————————————————————————–iii Certification —————————————————————————————-iv Dedication ——————————————————————————————v Acknowledgement———————————————————————————vi Abstract ——————————————————————————————-viii Table of Content ———————————————————————————–x List of Figures ————————————————————————————xiv List of Tables ————————————————————————————–xv List of Plates ————————————————————————————–xvi Abbreviations ————————————————————————————xxi CHAPTER ONE: INTRODUCTION 1.1 Background of the Study——————————————————————–1 1.2 Statement of Research Problem———————————————————–2 1.3 Justification of the Study——————————————————————–3
1.4 Aim of the Study——————————————————————————4
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1.5 Objective of the Study———————————————————————–4 CHAPTER TWO: LITERATURE REVIEW 2.1 Origin and Distribution of Guinea Fowl————————————————-6 2.2 Breeding—————————————————————————————-6 2.3 Social and Economic Importance of Guinea Fowl————————————-7 2.4 Functions of the Gastrointestinal Tract————————————————–8 2.5 Oesophagus————————————————————————————9 2.5.1 Developmental features———————————————————————9 2.5.2 Gross features——————————————————————————–9 2.5.3 Histological features———————————————————————–10 2.6 Crop——————————————————————————————–10 2.6.1 Developmental features——————————————————————–10 2.6.2 Gross features——————————————————————————-11 2.6.3 Histological features———————————————————————–11 2.7 Proventriculus——————————————————————————-11 2.7.1 Developmental features——————————————————————–12 2.7.2 Gross features——————————————————————————-12
2.7.3 Histological features———————————————————————–13
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2.8 Ventriculus———————————————————————————–14 2.8.1 Developmental features——————————————————————–16 2.8.2 Gross features——————————————————————————-16 2.8.3 Histological features———————————————————————–17 2.9 Small Intestine——————————————————————————-17 2.9.1 Developmental features——————————————————————–18 2.9.2 Gross features——————————————————————————-18 2.9.3 Histological features———————————————————————–19 2.10 Large Intestine—————————————————————————–20 2.10.1 Developmental features——————————————————————20 2.10.2 Gross features—————————————————————————–21 2.10.3 Histological features———————————————————————-21 CHAPTER THREE: MATERIALS AND METHODS 3.1 Egg Source and Preparation for Incubation——————————————-22 3.2 Pre-hatch Study of the Embryos———————————————————22 3.3 Post-hatch Study of Keets—————————————————————–23 3.4 Gastrointestinal Tract Harvest———————————————————–23
3.4.1 Morphological studies——————————————————————–23
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3.4.2 Morphometric studies——————————————————————–23 3.4.3 Histological studies———————————————————————–24 3.5 Microscopy and Photomicroscopy——————————————————-24 3.6 Statistical Analysis————————————————————————–24 CHAPTER FOUR: RESULT 4.1 Morphology———————————————————————————–25 4.1.1 Pre and post-hatch———————————————————————-25 4.2 Morphometry——————————————————————————–36 4.2.1 Pre and post-hatch———————————————————————-36 4.3 Histology————————————————————————————–47 4.3.1 Pre and post-hatch———————————————————————-47 CHAPTER FIVE: DISCUSSION———————————————————–86 CHAPTER SIX: CONCLUSION AND RECOMMENDATION——————–93 6.1 Conclusion————————————————————————————93 6.2 Recommendation—————————————————————————-94
REFERENCES———————————————————————————–95
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CHAPTER ONE
INTRODUCTION 1.1 Background of the Study The formation of a functional vertebrate gut involves several processes. These include the induction and patterning of the endoderm, recruitment of the mesoderm and tube formation, proliferation and specification of sections along the gut tract, and renewal of the mature gut epithelium by the specification of the endoderm that will eventually form the complex epithelium of the mature digestive organ (Grapin-Botton and Melton, 2000; Stainier, 2002).
The gut tube is formed by two invaginations appearing on either end of the embryo, the anterior intestinal portal (AIP) and the posterior intestinal portal (PIP). These two areas move inward into the embryo, taking the specified endoderm along with them, and forming a primitive tube at both ends of the gut. Fusion occurs in the middle of the embryo, and the midgut must roll up, taking the endoderm and surrounding mesoderm along with it to form a final continuous tube. At the end of this process, the vertebrate gut is grossly separated into three main regions: foregut, midgut, and hindgut (Grapin-Botton and Melton, 2000). Ultimately, the foregut gives rise to the oesophagus (and crop in birds), stomach (including the gizzard and proventricularis in birds) and derivative organs – thyroid, lungs, pancreas, and liver while the midgut forms the small intestine, and the hindgut forms the ceca (in birds) or appendix (in mammals), the large intestine and the cloaca (in birds) or rectum (in mammals) (Drucilla et al., 1998). The accessory digestive organ buds develop as outgrowths of endodermal epithelium that intermingle with the surrounding mesenchyme, and together they proliferate and
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ultimately differentiate during fetal development into functional organs such as the pancrease and liver (Aaron and James, 2009). Klasing (1999) studied the avian digestive system and found that the avian gastrointestinal tract is a double-ended open tube (as seen in mammals) that begins at the beak and finishes at the vent. In sequential order, it is composed of a mouth, oesophagus, crop, proventriculus, ventriculus, small intestine, caeca, rectum and cloaca. The gastrointestinal tract (GIT) becomes developmentally active in the early post-hatch period in poultry species (Uni et al., 2000) undergoing changes in weight and length that are determined by genetic and environmental factors (Langenfeld, 1992). Digestive tract has a major role in inducing growth during the early post hatch period. This was attributed to its more rapid increase in size compared to the whole body especially the small intestine (Nir et al., 1993).It possesses the functions of food content storage, secretion, digestion and absorption of nutrients (Sell et al., 1991).
1.2 Statement of Research Problem
The gastrointestinal tract is a critical organ system mediating nutrient uptake used by the animal (Frank, 2011). Understanding factors that influence GIT development, growth and function is critical in improving management and therapeutic approaches to maximize health and production efficiency. A lot of investigations on the development of avian digestive system have been made and also excellent reviews of the gastrointestinal of embryonic development have been given (Klasing, 1999; Uni et al., 2000). However, all these information were on the domestic fowl, ducks, turkey and quails. Among the few works done on the anatomy of the guinea fowl are; effect of age
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and sex on digestive tract morphometry of guinea fowl (Daria et al., 2012), studies on the onset of osteogenesis in grey-breasted helmeted guinea fowl (Salami, 2009), observations of the wattles of adult helmeted guinea fowl (Umosen et al., 2008), studies on the histochemistry of the proventriculus and gizzard of post-hatch guinea fowl (Senthanil et al., 2008), studies on the major respiratory pathways of the West African guinea fowl (Ibe et al., 2008), Studies on the digestive, respiratory, urogenital system and lymphoid organs of helmeted guinea fowl (Lakshminarasimhan et al., 1983) and Studies on the external morphology and skeletal system (Ojo et al., 1983). A survey of literature revealed that there are global interests in guinea fowl production as an alternative to the chicken (Nahason et al., 2006) but there is paucity of information on the gross and histology of this bird’s GIT to enhance domestication and productivity of this species hence the present study. 1.3 Justification of the Study The function of the digestive tract is to obtain the molecules necessary for the maintenance, growth and energy needs of the body from ingested food, in order to be able to perform its role of maximum production of meat and egg in this case. Therefore, the study of gastrointestinal development will shed light into the structural constituent of this organ and better understanding of its function(s). Information from this study will also equip the nutritionist with information to be able to formulate feeds that will be absorbable and helpful in enhancing production. This study will also give insight to the critical stages of GIT development and the changes that occurred at different stages of pre and post-hatch.
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1.4 Aim of the Study The aim of this research is to describe the morphological development of gastrointestinal tract of the helmeted guinea fowl during the pre- and post-hatch periods. 1.5 Objectives of the Study
i. To investigate the morphology and morphometry of gastrointestinal tract of the helmeted guinea fowl during the pre- and post-hatch periods.
ii. To investigate the histology of gastrointestinal tract of the helmeted guinea fowl during the pre- and post-hatch periods.
iii. To determine the period during which the GIT is fully developed at pre-hatch.
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