MORPHOGENESIS OF THE GASTROINTESTINAL TRACT OF HELMETED GUINEA FOWL (NUMIDA MELEAGRIS ) AT PRE AND POST-HATCH

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MORPHOGENESIS OF THE GASTROINTESTINAL TRACT OF HELMETED GUINEA FOWL (NUMIDA MELEAGRIS ) AT PRE AND POST-HATCH

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 ix 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 occur.

MORPHOGENESIS OF THE GASTROINTESTINAL TRACT OF HELMETED GUINEA FOWL (NUMIDA MELEAGRIS ) AT PRE AND POST-HATCH

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