Anatomical, histological, and scanning electron microscopic features of the esophagus and crop in young and adult domestic pigeons (Columba livia Domestica).

BACKGROUND: Pigeons (Columba livia) are mainly raised as a source of animal protein, racing, leisure and as an experimental animal. The present study investigated the morphology of the esophagus in the young and adult domestic pigeon, Columba livia domestica. METHODS: Ten young and ten adult, normal, and healthy pigeons were collected from the local breeders. Samples from different parts of esophagus and crop were examined grossly, by stereomicroscopy, scanning and light microscopy. RESULTS: The esophagus consisted of a long cervical part, a crop, and a short thoracic part. The crop was represented by a thin-walled outpouching with two lateral diverticula. The mucosa presented wavy fine folds in the cervical esophagus, irregular folds in the lateral diverticula giving it a corrugated appearance, and prominent longitudinal folds with several gland openings in the middle and lower parts of the crop, as well as in the thoracic esophagus. The density of gland openings was higher in adult pigeons than that in young pigeons. The mucosa of the esophagus was lined by non-keratinized stratified squamous epithelium. The shape, height, and branching of the mucosal folds differed between young and adult pigeons. Mucous-secreting alveoli were detected in the middle part of the crop as well as in the thoracic esophagus, but not in the cervical esophagus or lateral diverticula of the crop. CONCLUSION: The variations between the young and adult pigeons suggest a functional adaptation of adult pigeons to their diet compared to young pigeons.

Gross anatomical features of the gastrointestinal tract (GIT) of blue-and-yellow macaws (Ara ararauna) - oesophagus to cloaca.

Morphological studies of the gastrointestinal tract of blue-and-yellow macaws (Ara ararauna) are scarce. In view of the paucity of information regarding the digestive tract of macaws, this study aims to describe the gross anatomical features (oesophagus to cloaca) as part of a broad study of the gastrointestinal tract (GIT) of these birds. Three animals (two males and one female) adult macaws were anatomically dissected from the oropharynx to the cloaca to expose the GIT. The oesophagus was identified as a muscle-membranous tube continuous with the crop, which was intimately attached to the skin. The internal longitudinal folds of the cervical oesophagus were sparser cranial to the crop and less evident compared to the portion caudal to the crop. The duodenum began in the pylorus and was grey-coloured exhibiting a large lumen. The jejunum was formed by loops in a spiral-fashion model supported by mesojejunum. The ileum was also composed by small loops and was continuous with the colo-rectum forming the large intestine, because the caeca were absent. The large intestine was short, median in position, suspended in the dorsal wall of the abdominal cavity by mesentery and ended in the cloaca. The GIT was similar to the basic patterns in birds, in general, and also presented new unreported morphological data that might be important when studying nutrition and health of the macaws.

Histological and global gene expression analysis of the 'lactating' pigeon crop.

BACKGROUND: Both male and female pigeons have the ability to produce a nutrient solution in their crop for the nourishment of their young. The production of the nutrient solution has been likened to lactation in mammals, and hence the product has been called pigeon 'milk'. It has been shown that pigeon 'milk' is essential for growth and development of the pigeon squab, and without it they fail to thrive. Studies have investigated the nutritional value of pigeon 'milk' but very little else is known about what it is or how it is produced. This study aimed to gain insight into the process by studying gene expression in the 'lactating' crop. RESULTS: Macroscopic comparison of 'lactating' and non-'lactating' crop reveals that the 'lactating' crop is enlarged and thickened with two very obvious lateral lobes that contain discrete rice-shaped pellets of pigeon 'milk'. This was characterised histologically by an increase in the number and depth of rete pegs extending from the basal layer of the epithelium to the lamina propria, and extensive proliferation and folding of the germinal layer into the superficial epithelium. A global gene expression profile comparison between 'lactating' crop and non-'lactating' crop showed that 542 genes are up-regulated in the 'lactating' crop, and 639 genes are down-regulated. Pathway analysis revealed that genes up-regulated in 'lactating' crop were involved in the proliferation of melanocytes, extracellular matrix-receptor interaction, the adherens junction and the wingless (wnt) signalling pathway. Gene ontology analysis showed that antioxidant response and microtubule transport were enriched in 'lactating' crop. CONCLUSIONS: There is a hyperplastic response in the pigeon crop epithelium during 'lactation' that leads to localised cellular stress and expression of antioxidant protein-encoding genes. The differentiated, cornified cells that form the pigeon 'milk' are of keratinocyte lineage and contain triglycerides that are likely endocytosed as very low density lipoprotein (VLDL) and repackaged as triglyceride in vesicles that are transported intracellularly by microtubules. This mechanism is an interesting example of the evolution of a system with analogies to mammalian lactation, as pigeon 'milk' fulfils a similar function to mammalian milk, but is produced by a different mechanism.

Fossil evidence of avian crops from the Early Cretaceous of China.

The crop is characteristic of seed-eating birds today, yet little is known about its early history despite remarkable discoveries of many Mesozoic seed-eating birds in the past decade. Here we report the discovery of some early fossil evidence for the presence of a crop in birds. Two Early Cretaceous birds, the basal ornithurine Hongshanornis and a basal avian Sapeornis, demonstrate that an essentially modern avian digestive system formed early in avian evolution. The discovery of a crop in two phylogenetically remote lineages of Early Cretaceous birds and its absence in most intervening forms indicates that it was independently acquired as a specialized seed-eating adaptation. Finally, the reduction or loss of teeth in the forms showing seed-filled crops suggests that granivory was possibly one of the factors that resulted in the reduction of teeth in early birds.

Crop immune response post-Salmonella enteritidis challenge in eight commercial egg-layer strains and specific-pathogen-free White Leghorn chickens.

The crop immune response against Salmonella Enteritidis (SE) challenge in eight commercial egg-layer strains (five white-egg layer and three brown-egg layer) and specific-pathogen-free (SPF) White Leghorn (WL) hens was investigated. Pre- and post-SE challenge mucosal immune responses within the crops were evaluated. Commercial layers and SPF WL hens were orally challenged with 10(8) CFU/ml SE PT13a and SE nalR PT13, respectively. Crop lavage samples were collected at weekly intervals from day 0 (pre-challenge) to day 25-27 postinfection (PI), and bacteriological examination was performed to monitor progression of SE infection. Crop lavage samples were analyzed for SE-lipopolysaccharide (LPS)-specific IgA using enzyme-linked immunosorbent assay (ELISA). H&E-stained slides of crop sections from day 34 PI and uninfected controls were assessed for lymphoid tissue via light microscopy. Lymphoid areas were graded based on morphology, size, and cellularity using a score 0 to 5 scale. The 0 to 5 (low to high) numerical values represented progressive increases in size and cellular density of lymphoid tissue. Bacterial culture results showed the highest percentage of SE-positive crop lavage samples from all hen groups at day 5-6 PI and day 11-12 PI. A progressive decline in percentage of SE-positive crop lavage samples did occur as time PI lengthened; however, at day 25-27 PI SE persisted in crop lavage samples from SPF WL hens and three commercial white-egg layer strains. A marked increase in SE-LPS-specific IgA was measured in crop lavage samples between day 0 and day 11-12 PI for all hen groups. Crop SE-LPS-specific IgA response remained elevated above day 0 baseline for the duration of the experiment. Well-defined score 3 to 5 lymphoid tissue aggregates were observed in crop tissue sections harvested at day 34 PI. Comparison of crop sections determined a 1.2-4.0 times increase in ratio of lymphoid tissue in day 34 PI SE-challenged hens vs. uninfected control hens.

Guar meal diets as an alternative approach to inducing molt and improving Salmonella enteritidis resistance in late-phase laying hens.

Induced molting of laying hens is a practice used by commercial egg producers to increase the productive lifetime of their flock. However, the conventional method of inducing molt, which involves removal of feed, water, or both as well as a reduction in photoperiod to less than a natural day has drawn criticism due to animal welfare and food safety concerns. The objective of this study was to explore the efficacy of diets containing high levels of guar meal (GM) in inducing molt and reducing susceptibility to Salmonella Enteritidis colonization in late-phase laying hens. Late-phase (68 wk old) Lohmann laying hens were either full-fed standard laying hen diets (nonmolted control), induced to molt by feed withdrawal, or full-fed standard laying hen diets containing 20% GM with or without 250 units/kg of mannanase Hemicell supplementation. On the fourth day of treatment, all hens were orally challenged with SE (1.65 x 10(7) cfu). Hens were killed and evaluated for Salmonella colonization and differences in organ weights 5 d postinoculation. Salmonella Enteritidis present in crop, liver, ovary, and cecal contents were significantly reduced by feeding GM with enzyme supplementation compared with feed withdrawal hens. No significant differences were observed in reproductive tract weights of molted groups, although a difference in liver weight was detected. Results indicate that feeding diets containing 20% GM are as effective as complete feed withdrawal with respect to inducing molt with the added benefit of improved resistance to Salmonella Enteritidis colonization and translocation.

Filling and emptying of the alimentary tract of meal-fed broiler breeder hens.

For evaluation of the filling and emptying of the alimentary tract, broiler breeder hens were cooped and processed over a 2-d period. Hens were fed at 0600 h on d 1 and after access to feed for 0, 2, 4, and 6 h were placed into coops. Half of the hens from each pen were either immediately processed or were held in coops over-night and processed the following morning, d 2. The alimentary tract was excised from the carcass and then separated and weighed in three segments: the crop, proventriculus and gizzard, and intestines. Hens processed on d 1, after access to feed for only 2 h, had attained maximum intestine weight (176 g), but not until after access to feed for 6 h were peak crop weight (95 g) and peak weight for the proventriculus and gizzard (78 g) attained. Hens processed on d 2 did not differ in crop (12 to 14 g) or intestine (140 to 162 g) weight, but proventriculus and gizzard weights were significantly lower for hens not fed on d 1 prior to cooping (54 g) compared with hens fed on d 1 and cooped after 2, 4, or 6 h (62 to 63 g). However, hens processed on d 2 had proventriculus and gizzard weights that were the same as for those hens processed on d 1 and cooped at 0 h (63 g). Clearance of ingesta from the crop, proventriculus and gizzard, and intestines readily occurred while hens were held overnight without access to water.

Sonographic investigations of the gastrointestinal tract of granivorous birds.

This article describes the sonographic examination of the normal gastrointestinal tract of granivorous birds. Preliminary tests with dead birds were performed to get an idea of the sonographic echotexture of the avian gastrointestinal tract. Later, clinically healthy seedeaters of different weights were examined sonographically. As equipment a convex microcurved scanner with a particularly small coupling surface and an adjustable frequency from 5.5-7.5 MHz was used. For the investigation of the gastrointestinal tract, six sonographic approaches are described. After a starving time of 18 hours in the granivorous birds and water input, the best sonographic image quality could be obtained. Using this method, the crop, ventriculus, intestines, and cloaca could be demonstrated sonographically; whereas, it was not possible to visualize the normal proventriculus in granivorous birds. In contrast to mammals, the different layers of the wall of the gastrointestinal tract could not be visualized with the equipment used. Motility of individual parts of the gastrointestinal tract (GI tract), however, could be well demonstrated.

Effect of physical feed restriction during rearing on Large White turkey breeder hens: 3. Body and carcass composition.

Large White turkey breeder hens were used to evaluate the effect of three different levels of physical feed restriction on subsequent body and carcass composition. The four feed treatments were 1) ad libitum fed throughout the study (CC), 2) feed restricted from 16 to 24 wk (CR), 3) feed restricted from 3 to 16 wk (RC), and 4) feed restricted from 3 to 24 wk (RR). Feed restriction was implemented so that RC and RR hens achieved a 45% reduction in BW compared to CC hens at 16 wk. From 16 to 24 wk, feed was allotted to RR and CR hens to maintain a slight increase in BW. At the completion of each restriction period, hens were gradually returned to ad libitum feeding. At 30 wk, hens were photostimulated for a 20-wk summer season egg production cycle. Restricted fed hens had increased moisture levels at 16 and 30 wk and decreased fat levels at 16, 30, 39, and 54 wk (P < or = 0.05). Absolute and relative weights of the pectoralis major muscle were greater in hens fed ad libitum through 43 wk (P < or = 0.05). There were no differences in the number of maturing yellow follicles due to treatment. However, restricted fed hens had higher peak egg production during early lay but decreased subsequent and cumulative egg production. Changes in egg production were associated with changes in breast muscle weight. Prolactin levels were greater in hens in-production compared to hens out-of-production; however, there were no differences due to feed treatment. In conclusion, further research on quantitative feed-restriction programs, which result in body weight reductions as described in this study, should address specific physiological and nutritional requirements and not be implemented as general programs.

Physical, chemical, and microbiological changes in the crop of broiler chickens subjected to incremental feed withdrawal.

Trials were conducted to determine the effect of feed withdrawal on the weight, pH, native bacterial flora, and Salmonella typhimurium persistence in crops of broilers. Six-week-old broilers were provided medicated or unmedicated feed and were subjected to feed withdrawal for 0 to 24 h in transportation crates or on litter. After feed withdrawal, broilers were stunned, bled, scalded, and picked. Crops were aseptically removed and weighed. Crops were then blended in 20 mL distilled water, and pH values of the suspensions were measured. Aerobic bacteria, Enterobacteriaceae, S. typhimurium, and lactic acid bacteria in the suspension were enumerated on appropriate bacteriological media. Feed withdrawal produced significant decreases in the crop weights. Crop pH increased by 1.0 unit within 6 h of feed withdrawal. Enterobacteriaceae and S. typhimurium populations generally decreased during the first 12 h of feed withdrawal and remained unchanged or increased during the final 12 h of the 24-h feed withdrawal period. The number of lactic acid bacteria recovered from the crop usually decreased as the duration of feed withdrawal increased. Changes in crop weights, pH, native microflora, or the recovery of S. typhimurium from the crop were similar in broilers subjected to feed withdrawal on litter or in crates and in broilers provided medicated or unmedicated feed before initiating feed withdrawal. Findings indicate that a decrease in the number of lactic acid producing bacteria in the crop and an increase in crop pH may be related to the reduction of anti-Enterobacteriaceae activity in the crop during extended feed withdrawal.

Comparative morphology of the alimentary tract and its glandular derivatives of captive bustards.

This study describes the gross anatomy of the alimentary tract of Houbara Bustards (Chlamydotis undulata macqueenii), Kori Bustards (Ardeotis kori), Rufous-crested Bustards (Eupodotis ruficrista) and White-bellied Bustards (Eupodotis senegalensis) maintained in captivity by the National Avian Research Center in the United Arab Emirates. The morphology of the alimentary tract and the proportions of each region were similar in all 4 species. The length of the oesophagus, combined proventriculus and ventriculus, small intestine, and large intestine formed 24.2-28.4%, 7.3-9.7%, 40.5-55.1% and 9.1-14.7% of the total alimentary tract length respectively. Neither crop nor oesophageal enlargement was observed in the birds examined in this study, although male Kori Bustards possessed a saccus oralis in the oropharyngeal cavity. Oesophagi, proventriculi, ventriculi, caeca and large intestine were well developed in all species. The small intestine was shorter than that of other avian herbivores and granivores when compared on a bodyweight basis. The well differentiated stomachs and well developed caeca of the bustards examined in this study are characteristic of omnivores. Analysis of the mean lengths of the alimentary tract components and weight of the liver and pancreas showed sexual dimorphism in cases where male and female data were available for direct comparison.

Feeding regimen by sire family interactions on growth, immunocompetence, and disease resistance in chickens.

Progeny from matings of 12 sires from a White Plymouth Rock line selected for high juvenile BW and 96 dams from a White Leghorn line selected for low antibody production to SRBC were reared under alternate-day (AD) or ad libitum (AL) feeding regimens. Within a feeding regimen males were heavier than females, and within a sex, chicks fed AL were heavier than those fed AD. Feeding regimen by sire family interactions were significant for BW at 21 d of age for both male and female progeny. The interaction was due to differences among sires in the magnitude of the AD: AL relationship. Product moment correlation coefficients between feeding regimens for male and female progeny of sire families for 21-d BW were essentially zero, which was consistent with the sire family by feeding regimen interactions observed at this age. At 41 d of age, relative to BW, weights of empty esophagus plus crop and of crop contents were greater for AD than AL chicks. There were differences among sire families for crop content and breast weights relative to BW. Lesion scores to Escherichia coli challenge were lower and antibody titers to SRBC antigen were higher in AD than in AL chicks. Sire families differed in antibody titers to SRBC antigen. Feeding regimen by sire family interactions were significant for percentage change in BW 144 h after E. coli challenge and lesion scores were greater for AL than AD chicks.

Mechanoreceptors in the crop of the domestic fowl.

Electrophysiological "single fiber" experiments were conducted on the vagal nerves of the domestic fowl to confirm the presence of mechanoreceptors in the crop and to study their properties. The afferent activity of the left vagus nerve was recorded in nine anaesthetized laying hens with and without the crop being artificially distended. Twenty-two units were found to respond to the crop inflation, 18 of them being slowly adapting mechanoreceptors. The discharge rate of these slowly adapting units increased as the pressure inside the crop was raised. Twelve units were localized and the responses of three units to different doses of acetylcholine, epinephrine, and norepinephrine were obtained. Mechanoreceptor discharges were enhanced when the crop was distended and during drug-induced contractions of its smooth muscle, suggesting an "in series" location within the muscle layers. Such receptors may provide the afferent limb of a reflex regulating crop motility and may be involved in the regulation of feed intake.

[Skin and plumage changes in domestic birds. I. Skin changes]. / Haut- und Gefiederveränderungen bei domestizierten Vögeln. Teil I: Hautveränderungen.

This study presents modifications of the common integument and specific integumental structures developed during the domestication process of different poultry species. These modifications include dewlaps, variations of the comb, ear lobes, and wattles, size and form variations of the beak, exuberances of the cere and orbital skin, spur defects, loss of the uropygial gland, and crop dilatations. Most skin modifications were genetically manifested by exhibition poultry, and perpetuated by deliberate selective breeding. Several of the skin modifications described severely impair the normal, species-typical way of life of the animals concerned. The range of negative influences exerted by some of the fancy breed characteristics includes physical disabilities as well as disorders in food intake, reproduction, and social behaviour. Additionally, genetic defects and pathogenic predispositions can be found.

Behavioural and physiological effects of prolactin in incubating ring doves.

The role of prolactin in the maintenance of incubation behaviour in ring doves was re-examined and the dose-response relationships for behavioural, target tissue and body weight changes induced by injections of prolactin were compared in doves tested during the incubation phase of the breeding cycle. Doves given injections of prolactin twice a day starting on day 4 of incubation, during a 10-day period of isolation from their mates and nests, showed a higher persistence of incubation behaviour than doves injected with saline vehicle. However, the prolactin treatment failed to maintain incubation behaviour to the same extent as that observed in non-isolated untreated breeding pairs. Liver and body weights were higher and testicular weights lower in birds treated with high doses of prolactin than in non-isolated birds which had been incubating for 14 days. Good dose-response relationships were established between body, liver, crop and testes weights and the dose of prolactin administered. However, only a weak dose-response relationship was observed between prolactin and the maintenance of incubation behaviour. Overall, females injected with prolactin displayed more quiet sitting behaviour, less body weight gain and more gonadal regression than males injected with prolactin. Males in untreated breeding pairs had higher liver weights and lower crop weights than females. It is concluded that prolactin plays a role in maintaining readiness to incubate in doves, but that other factors may also contribute to this response. Further, it appears that prolactin mediates several target tissue changes which are sex-specific during incubation.

Crop volume of chickens as affected by body size, sex, and breed.

Single Comb White leghorn (SCWL) hens, broiler cockerels, and two weight classes of SCWL roosters were utilized to determine the relationships of breed, sex, and body size to crop volume. Crop volume was significantly different (P less than .05) among all types of birds examined. Significant differences (P less than .05) of crop volume per kilogram body weight occurred between birds of opposite sex within a breed and between birds of identical sex but differing breed. However, within a breed, birds of identical sex but differing body size exhibited similar crop volume (cc/kg body weight).

The digestive tract of the whiteback griffon vulture and its role in disease transmission among wild ungulates.

The digestive tract of the whiteback vulture (Gyps africanus) is described. Some disease organisms were fed to a captive bird to discover if they could survive passage through the tract, and the role of these scavenging birds in the spread of diseases among wild ungulates is discussed.