Sites of organic acid production and pattern of digesta movement in the gastrointestinal tract of geese

An investigation into the influence of age on the standardized amino acid digestibility of wheat and sorghum in broilers

Standardized ileal digestibility coefficients (SIDC) of nitrogen (N) and amino acids (AA) in wheat and sorghum at 6 different ages (d 7, 14, 21, 28, 35, and 42) of broilers were determined. Two assay diets were formulated to contain 93.8% of each grain as the sole source of AA in the diet. Titanium dioxide (0.5%) was added as an indigestible marker. Each assay diet was fed to 6 replicate cages housing 14 (d 7), 12 (d 14), 10 (d 21), 8 (d 28), 8 (d 35), and 6 (d 42) birds per cage for 4 d prior to ileal digesta collection. The apparent ileal digestibility coefficients (AIDC) were standardized by using the age-appropriate basal endogenous AA losses. In the case of wheat, AIDC of N and all AA increased (linear or quadratic, P < 0.05 to 0.001) with advancing age. No age effect was noticed on the SIDC of N, average of indispensable (IAA) and dispensable AA (DAA), though the average of total AA (TAA) tended (linear, P = 0.09) to increase as birds grew older. In sorghum, the AIDC of N, average of IAA and DAA were unaffected (P > 0.05) by age. The SIDC of N, average SIDC of IAA, DAA and TAA were higher at d 7, reduced at d 14 and then plateaued. Among the IAA, the SIDC of Arg, His, Ile, Leu, Lys, Thr, Val, and the SIDC of all individual DAA (except Cys) decreased with age (linear or quadratic, P < 0.05 to 0.001) with higher values at d 7. The higher SIDC values determined at d 7 were due to higher EAA losses during wk 1. The results showed that broiler age influences AA digestibility and this may need be considered in practical feed formulations. The age effect is variable depending on the grain type and specific AA.

Studies on the weight of the gastrointestinal tract, digesta composition and occurrence of gastro- and enteroliths in adult domesticated ostriches fed different diets

Comminuting the ingested material in the stomach and fermentation in the large intestine of ostriches, allows an efficient utilization of fiber-rich feedstuffs. The entire gastrointestinal tract (GIT) of 61 adult ostriches (both sexes; av. age of 15 mo), which had previously been fed a ration consisting of either haylage and pelleted compound feed (HP) or haylage, corn silage and pelleted compound feed (HCP), was the subject of the present investigations. The weight of the different compartments of the GIT was measured. The digesta was differentiated into inorganic and organic substances. Wet sieving was used to separate the collected stones (>19 mm), small stones (1 mm), and sand (<1 mm). Ostriches fed the HCP diet had a significantly higher empty gizzard weight (3,435 g) compared to those fed the HP diet (3,064 g). Additionally, the weight of the empty cecum (left and right parts) was increased (P < 0.05) for ostriches fed the HCP diet (107 and 122 g, respectively) in comparison to those fed the HP diet (93.4 and 108 g, respectively). The weight of pure digesta in the gizzard and left or right cecum for ostriches fed the HP diet was higher (1,640, 448, and 471 g, respectively) compared to those fed the HCP diet (P < 0.05). The contents of crude ash and HCl-insoluble ash in the digesta of all the GIT compartments were higher for ostriches fed the HP diet in comparison to those fed the HCP diet (P < 0.05). Independent of the type of the offered diet, the large stones occurred only in the proventriculus and gizzard (2.71 and 4.76%, respectively), while sand dominated in the distal colon (30.3%). The high proportion of stones in the gizzard form the "mechanical equipment" which enables the animals to grind basic feed such as corn silage or haylage, and these are almost completely excreted as sand. Continuous stone replacement for ostriches is necessary but the amount mostly depends on the type of feed.

Basal ileal endogenous amino acid flow in broiler chickens as influenced by age

The current study was carried out to measure the basal ileal endogenous amino acid (EAA) flow in male broilers (Ross 308) at different ages (d 7, 14, 21, 28, 35, and 42), following the feeding of a nitrogen-free diet. Titanium dioxide (5 g/kg) was included as an indigestible marker. The nitrogen-free diet was offered for four days prior to ileal digesta collection to 6 replicate cages housing 14 (d 3–7), 12 (d 10–14), 10 (d 17–21), 8 (d 24–28), 8 (d 31–35), and 6 (d 38–42) birds per cage. The basal EAA flow was calculated as g/kg DM intake. The amino acid (AA) profile of endogenous protein, expressed as g/100 g protein, was also calculated. The basal endogenous flow of nitrogen and all individual and total AA decreased quadratically (P < 0.05 to 0.001), with flows being higher on d 7, then decreasing on d 14, plateauing until d 35 and decreasing further on d 42. The concentrations of Trp, Cys, and Gly in the endogenous protein increased linearly (P < 0.01 to 0.001) with advancing age, whereas a linear decrease (P < 0.001) was noted for Lys. A quadratic influence (P < 0.05 to 0.001) was observed for the concentrations of Ile, Leu, Met, Val, and Asp. These changes in the endogenous protein profile may be attributed to variations in the contribution of endogenous sources with age but delineating the exact contribution of different sources is complicated. Overall, the current findings suggest that the basal ileal EAA flow is influenced by broiler age and age-specific EAA flows may need to be considered to standardize the AA digestibility.

Avian Physiology: Are Birds Simply Feathered Mammals?

There are marked differences between the physiology of birds and mammals. These reflect the evolutionary distance between the two classes with the last common ancestor estimated as existing 318 million years ago. There are analogous organ systems in birds and mammals. However, marked differences exist. For instance, in the avian gastro-intestinal tract, there is a crop at the lower end of the esophagus. This functions both to store feed and for microbial action. The avian immune system lacks lymph nodes and has a distinct organ producing B-lymphocytes, namely the bursa Fabricius. The important of spleen has been largely dismissed until recently. However, its importance in both innate and specific immunity is increasingly recognized. There is a major difference between birds and mammals is the female reproductive system as birds produce large yolk filled eggs. The precursors of the yolk are synthesized by the liver. Another difference is that there is a single ovary and oviduct in birds.

Comparative study of protease hydrolysis reaction demonstrating Normalized Peptide Bond Cleavage Frequency and Protease Substrate Broadness Index

Two commercial proteases (subtilisin-typed FNA from Bacillus amyloliquefaciens, and chymotrypsin-like NPP from Nocardiopsis prasina), porcine pepsin, porcine pancreatin having protease activity and their combinations were studied in vitro by LC-MS for their ability to digest soy protein isolate (SPI) under conditions close to those found in the stomach (pH 3.7) and small intestine (pH 6.5). The total number of peptides generated, and their size distribution were obtained under each set of the digestion conditions. These peptides were grouped according to their C-terminal amino acid (AA) residue (P1) and mass, based on which two concepts were proposed, i.e., Normalized Peptide Bond Cleavage Frequency (NPBCF) and Protease Substrate Broadness Index (PSBI). At pH 3.7, FNA+pepsin increased PSBI vs. pepsin alone by 2.7 and 4.9 percentage points (p.p.) at a SPI:protease ratio of 20:1 and 100:1, respectively. At pH 6.5, FNA+pancreatin improved PSBI by 9.1 and 10.2 p.p. at SPI:protease 20:1 and 100:1, respectively, vs. pancreatin alone. NPP generated 38% more peptides than FNA when administered with pancreatin at SPI:protease 200:1:1 and pH 6.5, but FNA alone (28.9) or FNA+pancreatin (29.1) gave a higher PSBI than pancreatin (22.2), NPP (20.3) and NPP+pancreatin (22.0). At pH 3.7 FNA generated 59% and 39% of peptides of pepsin at SPI:protease of 20:1 and 100:1, respectively, and both groups of peptides had similar size distribution. At pH 6.5 more small sized peptides were generated by FNA or FNA+pancreatin than pancreatin and NPP alone or pancreatin+NPP. In conclusion, FNA showed complementary effects with pepsin and pancreatin in terms of PSBI and generated more small sized peptides compared to NPP.

Effect of dietary fibre and grit on performance, gastrointestinal tract development, and grit pattern of goose

1. This study aimed to investigate effects of dietary fibre and grit on growth performance, gastrointestinal tract development, and gizzard grit retention of geese. 2. The trial had a 3 × 2 factorial design consisting of three levels of dietary crude fibre (CF, 4%, 7% and 10%, adjusted by grass powder), with or without grit addition (1-4 mm river sand). 3. In total, 648, 22-d-old male goslings were randomly allotted to six treatments (six pens/treatment). At 49 d and 70 d of age, one goose per pen was euthanised to collect samples. 4. The birds fed 10% CF had decreased feed conversion ratio (FCR) during 22-49 d, but this effect was less in older geese. Increasing dietary CF levels increased relative weights of gizzards for geese aged 49 d and 70 d. Grit addition decreased the relative weights of gizzard and duodenum of geese aged 49 d. The gizzard of geese could selectively retain grit from feed even with no grit added. With adequate supply, most grit in gizzard was 0.45-3 mm in size. 5. In conclusion, supplement of CF and grit mainly affected gastrointestinal tract, and the amount of CF affected FCR. Geese aged 22-49 d could utilise dietary CF levels of 4%-7% and older birds could feed on diets with up to 10% CF. The gizzard of goose selectively retained grit of a particle size of 0.45-3 mm.

Determination of gastrointestinal passage rate using three different markers in laying hens

The titanium dioxide (TiO₂ ) marker technique is currently widely practiced as a method to evaluate gastrointestinal (GI) passage rate in poultry. However, this method requires sacrificing the animal to obtain digesta samples, is labour-intensive and eliminates the possibility of follow-up studies with the same individual. The aim of this study was to evaluate whether the radiographic methods barium-impregnated polyethylene spheres (BIPS) and barium sulphate (BaSO₄ ) suspension are in agreement with the TiO₂ technique and can be used as an alternative method for GI passage rate determination in laying hens. Whole-body radiographs were taken at different time points. Hens of group 3 (n = 55) were orally inoculated with 5 g of feed mixed with 0.15 g TiO₂ , 5 hens per time point sacrificed, and whole gastrointestinal organs (crop, proventriculus, gizzard, small intestine and large intestine) were collected and analysed for TiO₂ content. The average marker passage rate of hens administered BaSO₄ was significantly faster than those administered BIPS (gizzard: 15.2 hr vs. 43.2 hr; small intestine: 15.2 hr vs. 38.4 hr, respectively). A greater percentage of BIPS remained in the crop at 0, 0.5, 2, 3 and 8 hr post-inoculation (p.i.) and in the gizzard at 2, 24, 36 and 48 hr p.i. (all p < 0.05) compared to TiO₂ . In conclusion, the evaluation of the GI transit time is feasible using BIPS, TiO₂ and BaSO₄ . The evaluation of the GI transit time using BIPS and BaSO₄ needs further investigation.

Response of goose intestinal microflora to the source and level of dietary fiber

Geese are capable of digesting and making use of a high-fiber diet, but the mechanism is not well understood and would be of great significance for the development and utilization of roughage resources. In this study, we investigated the effect of dietary fiber (source: corn stover and alfalfa, included at 5% or 8%) on microflora in goose intestines. We used 35-day-old Carlos geese in which we first studied the influence of fiber ingestion on diet digestibility and immune organ indices of geese and found that high dietary fiber (8% content) significantly increased feed intake, the digestibility of neutral and acid detergent fiber, and thymus, bursa, and spleen size. Subsequently, we investigated the effect of dietary fiber on the microbial flora in the various intestinal segments by high throughput sequencing. The bacterial diversity and relative abundance were significantly affected by the type and amount of dietary fiber fed, including that of cellulolytic bacteria such as Bacteroides, Ruminococcus, Clostridium, and Pseudomonas spp. Finally, we isolated and identified 8 strains with cellulolytic ability from goose intestine and then analyzed their activities in combination. The optimal combination for cellulase activity was Cerea bacillus and Pseudomonas aeruginosa. This study has laid a theoretical and practical foundation for knowledge of the efficient conversion and utilization of cellulose by geese.

Effects of dietary protein and energy levels on digestive enzyme activities and electrolyte composition in the small intestinal fluid of geese

The present study was conducted to evaluate the effects of dietary protein and energy levels on digestive enzymes and electrolyte composition in jejunum of geese. A 3×3 factorial and completely randomized design was adopted with three protein levels and three energy levels. The experiment included four replicates for each treatment, and three geese for each replicate. Isovolumetric supernate from centrifugal jejuna fluid were mixed in each replicate. Activities of digestive enzymes and ions were analyzed. The results showed trypsin and chymotrypsin activities were significantly increased with increasing of dietary protein and energy levels (P<0.05). The concentrations of Ca²⁺ and pH value were significantly decreased by increased dietary protein and energy levels. However, no significant differences were found for the activities of amylase and cellulase, as well as the concentration of Na⁺ among groups with different protein and energy levels. In conclusion, digesta enzymes and electrolytes in the small intestine adapted to the protein and energy levels. The activities of protease, rather than amylase and cellulase were induced with increasing of protein and energy levels. The imbalance of positive and negative ions was possibly adjusted by the fluctuant concentrations of K⁺ , Cl^- and Ca²⁺ for maintaining normal physiological function.

Impacts of dietary calcium, phytate, and nonphytate phosphorus concentrations in the presence or absence of phytase on inositol hexakisphosphate (IP6) degradation in different segments of broilers digestive tract

A total of 1,440 straight-run Heritage 56M × fast-feathering Cobb 500F broiler birds were fed from 11 to 13 d of age to determine the impacts of calcium (Ca), phytate phosphorus (PP), nonphytate P (NPP) and phytase concentrations on the myo-inositol hexakisphosphate (IP6) flow through the different parts of gastrointestinal tract (GIT). The experiment was a 2×2×2×3 randomized block design with 2 Ca (0.7 and 1.0%), 2 PP (0.23 and 0.34%), 2 nPP (0.28 and 0.45%) and 3 phytase (0-, 500-, and 1,000-phytase unit (FTU)/kg) concentrations. The experiment was replicated twice (block) with 3 replicates per treatment (TRT) of 10 birds per block. Concentration of IP6 in crop, proventriculus (PROV) plus (+) gizzard (GIZ) and distal ileum digesta as well as the ileal IP6 disappearance was determined at 13 d of age. In crop, higher IP6 concentration was seen with increased Ca (P < 0.05). Despite the interaction between PP and phytase, higher dietary PP led to greater IP6 concentration (P < 0.05). Similar main effects of PP and phytase were also seen in Prov+Giz and ileum (P < 0.05) without interactions. Interaction between Ca and nPP on IP6 concentration was seen in Prov+Giz (P < 0.05). Decreased ileal IP6 disappearance was found at higher Ca (62.3% at 0.7% Ca vs. 57.5% at 1.0% Ca; P < 0.05). In general, adding phytase improved IP6 degradation but the degree of impact was dependent on nPP and PP (P < 0.05). In conclusion, phytase inclusion significantly reduced IP6 concentration and IP6 disappearance in distal ileum regardless of GIT segments or diet composition, but impacts of dietary Ca, nPP, and PP differed depending on GIT segment examined.

Effect of dietary coarsely ground corn on broiler live performance, gastrointestinal tract development, apparent ileal digestibility of energy and nitrogen, and digesta particle size distribution and retention time

Dietary structural material has been reported to improve broiler live performance and gastrointestinal tract (GIT) function. In this 50 d cage study, the effects of coarsely ground corn (CC) inclusion on broiler live performance, GIT development, apparent ileal digestibility (AID) of energy and nitrogen (N), and digesta particle size distribution and retention time were investigated. This study included 3 CC inclusions (0, 25, and 50% fine corn [FC] replaced by CC), with 6 replicate cages of 10 birds per treatment. The feed conversion ratio (FCR) at 35 and 42 d was improved (P<0.01) as the dietary inclusion of CC increased without effect on feed intake. The 50% CC diet increased absolute and relative gizzard weight at 42 d of age as compared to diets with 0 and 25% CC (P<0.01). Dietary CC increased absolute proventriculus weight at 28 d of age (P<0.05). A numerically lower gizzard digesta pH (P<0.08) was observed at 28 d but not 42 d of age, and there was no difference in proventriculus, jejunum, or ileum digesta pH at 28 or 42 d of age. The 25 and 50% CC treatments increased the digesta retention time at 30 and 45 d of age (P<0.05 and P<0.01, respectively). The 25 and 50% CC treatments improved AID of energy by 7.1 and 8.2%, respectively, when compared with the 0% CC treatment, and they improved AID of N by 12.2 and 12.4%, respectively (P<0.01). The digesta particles in the jejunum exhibited a similar distribution, with a dgw (geometric mean diameter by mass) of 218, 204, and 181 μm when 0, 25, of 50% CC diets were consumed, respectively. In conclusion, birds fed pelleted and screened diets that contained 25 and 50% CC exhibited increased BW, improved FCR, and increased AID of energy and N, which was probably due to enhanced gizzard development and greater digesta retention time.

Screening of Lactobacillus strains of domestic goose origin against bacterial poultry pathogens for use as probiotics

Lactobacilli are natural inhabitants of human and animal mucous membranes, including the avian gastrointestinal tract. Recently, increasing attention has been given to their probiotic, health-promoting capacities, among which their antagonistic potential against pathogens plays a key role. A study was conducted to evaluate probiotic properties of Lactobacillus strains isolated from feces or cloacae of domestic geese. Among the 104 examined isolates, previously identified to the species level by whole-cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and analysis of 16S-23S regions of rDNA, dominated Lactobacillus salivarius (35%), followed by Lactobacillus johnsonii (18%) and Lactobacillus ingluviei (11%). All lactobacilli were screened for antimicrobial activity toward Salmonella Enteritidis, Escherichia coli, Clostridium perfringens, Staphylococcus aureus, Pasteurella multocida, and Riemerella anatipestifer using the agar slab method and the well diffusion method. Lactobacillus salivarius and Lactobacillus plantarum exhibited particularly strong antagonism toward all of the indicator strains. In the agar slab method, the highest sensitivity to Lactobacillus was observed in R. anatipestifer and P. multocida, and the lowest in E. coli and S. aureus. The ability to produce H₂O₂was exhibited by 92% of isolates, but there was no correlation between the rate of production of this reactive oxygen species and the antimicrobial activity of Lactobacillus sp. All lactobacilli showed resistance to pH 3.0 and 3.5 and to 2% bile. The data demonstrate that Lactobacillus isolates from geese may have probiotic potential in reducing bacterial infections. The antibacterial activity of the selected lactobacilli is mainly due to lactic acid production by these bacteria. The selected Lactobacillus strains that strongly inhibited the growth of pathogenic bacteria, and were also resistant to low pH and bile salts, can potentially restore the balance of intestinal microflora in geese and could offer an alternative to antibiotic therapy.

Characterizing the avian gut microbiota: membership, driving influences, and potential function

Birds represent a diverse and evolutionarily successful lineage, occupying a wide range of niches throughout the world. Like all vertebrates, avians harbor diverse communities of microorganisms within their guts, which collectively fulfill important roles in providing the host with nutrition and protection from pathogens. Although many studies have investigated the role of particular microbes in the guts of avian species, there has been no attempt to unify the results of previous, sequence-based studies to examine the factors that shape the avian gut microbiota as a whole. In this study, we present the first meta-analysis of the avian gut microbiota, using 16S rRNA gene sequences obtained from a range of publicly available clone-library and amplicon pyrosequencing data. We investigate community membership and structure, as well as probe the roles of some of the key biological factors that influence the gut microbiota of other vertebrates, such as host phylogeny, location within the gut, diet, and association with humans. Our results indicate that, across avian studies, the microbiota demonstrates a similar phylum-level composition to that of mammals. Host bird species is the most important factor in determining community composition, although sampling site, diet, and captivity status also contribute. These analyses provide a first integrated look at the composition of the avian microbiota, and serve as a foundation for future studies in this area.

Effects of diet type and ingredient composition on rate of passage and apparent ileal amino acid digestibility in broiler chicks

This experiment evaluated rate of passage (ROP) and apparent ileal amino acid digestibility (AIAAD) of 4 diets varying in ingredient composition fed to broilers from 14 to 22 d of age. Two hundred and 88 Ross × Ross 708 chicks (12 birds per cage; 0.45 m(2) per bird) were randomly assigned to 24 cages (6 replicate cages per treatment) at 1 d of age. Experimental diets were 1) corn-soybean meal-based (CSM) diet containing porcine meat and bone meal (MBM; 5% inclusion), 2) CSM diet containing distillers dried grains with solubles (DDGS; 5% inclusion), 3) semipurified (SP) diet containing MBM (38% inclusion), and 4) SP diet containing DDGS (76% inclusion). Diets were formulated to contain 20% CP and were adequate for vitamins and minerals. Experimental diets were provided from d 14 to 22. On d 18, a total excreta collection was conducted every hour for 12 h from 0800 to 1900 h to determine ROP, and AIAAD was determined on d 22. Time of 1% TiO(2) excretion (T1), 50% TiO(2) excretion (T50), and mean retention time (MRT) were used to express ROP. The SP-MBM diet reached T1 (P < 0.05) faster than the SP-DDGS or 2 CSM diets. However, T50 indicated a faster (P < 0.05) ROP for SP-DDGS than the 2 CSM diets, and no significant difference was observed between the 2 SP diets. The MRT of the SP-DDGS diet (5.13 h) was less (P < 0.05) than the MRT of the SP-MBM, CSM-MBM, and CSM-DDGS diets, which resulted in values of 5.48, 5.62, and 5.58 h, respectively. In general, the AIAAD values were higher (P < 0.05) for the 2 CSM diets than for SP diets. Except for His, no statistical differences were observed between the AIAAD of the 2 CSM diets. Comparing the 2 SP diets, AIAAD was usually similar or higher (P < 0.05) for SP-DDGS, except for His, Lys, and Gly, which were higher (P < 0.05) for SP-MBM. Based on T50 and MRT, SP diets containing DDGS had a faster ROP in broilers than CSM diets or SP diets containing MBM.

Spatiotemporal mapping of the motility of the isolated chicken caecum

We studied the caecal contractile activity of the chicken (Gallus gallus) using single caeca that had been cannulated at their proximal and distal ends, and in paired caeca, maintained in situ on excised segments of gut that were cannulated at the colonic and small intestinal ends. Longitudinal and circular contractile patterns were characterised using high-definition spatiotemporal mapping. Low amplitude longitudinal contraction waves of frequency 14.1 cycles/min occurred in the absence of major contractile events. These were termed fast phasic and appeared to be mediated by slow waves. The nature of major spontaneous contractions occurring in the single caecum varied with the level of caecal distension. Type A contractions occurred when the caecum was not distended, originated from variable sites and propagated in both directions. Type B or C contractile events occurred when the caecum was moderately or fully distended, originated from a predominantly distal site and propagated proximally. On diameter maps, each type B event comprised a succession of contractions which had similar propagation speeds, frequency and direction to fast phasic contractions. Type C events were comprised of a succession of higher amplitude contractions with no appreciable propagation. Perfusion of saline via the colon resulted in fluid entering both caeca and the onset of aborad contractions in their proximal canals. Saline was also seen to flow between caeca during contractile events however no saline was seen to enter the small intestine as has been postulated by other workers.

Examination of the microbial ecology of the avian intestine in vivo using bromodeoxyuridine

Bromodeoxyuridine, a thymidine analogue that can be incorporated into the DNA of actively dividing cells, has been used in vivo to identify intestinal bacteria that are metabolically active in 3-week-old turkey poults during an acute period of feed withdrawal. Automated ribosomal intergenic spacer analysis was used to identify amplicons unique to animals subjected to feed withdrawal. One amplicon was unique to fasted birds while two amplicons were present in 60% of fasted birds and absent in all fed birds. Sequence analysis of 16S ribosomal genes indicated the caecal communities of all birds were dominated by Clostridiaceae while also harbouring low levels of metabolically active gamma-proteobacteria and Bacteroides. Twenty per cent of clones from the fasted animals were identified as belonging to the genus Papillibacter, suggesting these microbes may be specifically dividing in response to environmental conditions present in the caeca of fasted birds.

Development of the activities of pancreatic and caecal enzymes in White Roman goslings

1. This study was to investigate the development of the activities of pancreatic and caecal enzymes in White Roman goslings from hatching to 28 d of age. 2. A total of 80 1-d-old goslings were used. At hatching, 3 and 7 d of age, 16 goslings (8 males and 8 females) were used. At 11, 14, 21 and 28 d of age, 8 goslings, 4 males and 4 females were selected. The activities of amylase, lipase, trypsin and chymotrypsin in each segment of the small intestine (duodenum, jejunum, ileum) and their contents and the activity of cellulase in the caecal contents were measured. 3. The specific activity (SA) of amylase in the duodenal mucosa and contents increased significantly both from 11 to 14 and 14 to 21 d of age and declined after 28 d of age. In the jejunum and ileum, there was a significant peak in the SA of amylase in the mucosa in goslings from 7 to 21 d of age. On average, the SA of lipase of mucosa and content in the small intestine was initially low but gradually increased from 14 to 21 and from 21 to 28 d of age. 4. The SA of trypsin in the contents of the duodenum and the jejunum increased both from 7 to 11 and 11 to 14 d of age and there was high activity in the ileal contents from 14 to 21 d of age. From 3 to 14 d of age, the SA of chymotrypsin in the duodenal mucosa significantly increased and peaked. There was a significant peak at 11 d of age in the SA of chymotrypsin in the duodenal or jejunal contents and in the ileal contents at 7 d. The SA of cellulase in the caecal contents increased linearly with age, reaching a plateau at 28 d of age. 5. The rate of activity development varied from hatching to 28 d of age. However, the mean SA of amylase and lipase of intestinal contents reached a peak at 21 d, trypsin and chymotrypsin at 11 d and cellulase at 28 d of age, respectively. The quantitative changes in SA of cellulase, amylase, lipase, trypsin and chymotrypsin increased by about 4-, 3-, 5-, 2- and 3-fold, respectively, in the intestinal content of goslings. Thus, development of proteases in the intestine of goslings peaked more rapidly than amylase, lipase and cellulase during the first 4 weeks.

Viscoelastic properties of the small intestinal and caecal contents of the chicken

We measured the coefficients of viscosity, shear rates and shear stresses of chicken small intestinal and caecal contents, including solid particles, using a tube-flow viscometer. The coefficients of viscosity of chicken small intestinal and caecal contents were correlated negatively with their shear rates, a characteristic typical of non-Newtonian fluids. The coefficient of viscosity of the small intestinal contents was lower than that of the caecal contents at a shear rate of 1 s(-1). Chicken caecal contents were more viscous than pig caecal contents. The exponential relationship between shear stress and shear rate showed that chicken small intestinal and caecal contents had an apparent Herschel-Bulkley fluid nature. These results indicate that solid particles, including uric acid crystals, are mainly responsible for the viscosity of the digesta in the chicken.

Effect of feeding whole cereals on performance, starch digestibility and duodenal particle size distribution in broiler chickens

1. An experiment was conducted to study the effects of whole wheat, oats and barley at different inclusion levels on performance, starch digestibility, duodenal particle size distribution, gizzard weight and pH of gizzard contents for broiler chickens. 2. Feed consumption and weight gain were significantly reduced when ground cereals were replaced by whole cereals (P < 0.05). However, feed conversion efficiency was not affected by inclusion of up to 440 g/kg of whole wheat, and up to 300 g/kg of whole oats and barley. 3. Duodenal particle size was measured by laser diffraction to below 1 micron in size. A remarkably large proportion of particles were below 100 microns, with as much as 50% of the particles in the duodenum being below 40 microns in size. Inclusion of moderate amounts of whole cereals reduced the duodenal mean particle size. Large inclusions of whole cereals decreased (P < 0.05) the proportion of particles up to 40 microns in size, and increased (P < 0.05) the proportion with size between 100 and 300 microns. 4. Starch digestibility was improved (P < 0.05) by replacing ground wheat or barley with whole wheat or barley. 5. There was no consistent effect of cereal species or feed form on the pH value of the gizzard contents.

Quantification of digesta flow into the caeca

1. A caecal intubation technique was developed to determine the amount of digesta that enters the caeca of fed and feed-deprived chickens. 2. Dry matter intakes per day for control and caecostomised chickens were not significantly different. 3. For fed and feed-deprived roosters, water intake was significantly increased by caecostomy in control birds and was significantly increased by feeding. 4. Amount of caecal dry matter excretion was significantly increased by feeding, but no difference in caecal water excretion was observed. 5. The ratio of caecal excretion (caecal/total excretion) of dry matter and water tended to decrease in response to feeding. 6. It is concluded that dry matter entry into the caeca represents 18% or 25% of the total dry matter excretion in fed or feed-deprived birds, respectively. Corresponding values for water entry are 17 and 26%. Therefore, the caeca play an important role in water balance.

Effects of caecal ligation and colostomy on water intake and excretion in chickens

1. The effect of caecal ligation and colostomy on water intake and excretion were examined in chickens fed a low-protein diet or a low-protein diet supplemented with urea. 2. When fed a low-protein diet, the water intake and the ratio of water intake to food intake were increased by colostomy (P < 0.05) but not changed further by caecal ligation of colostomised chickens. 3. When fed a low-protein diet supplemented with urea, the amount of water intake and the ratio of water intake to food intake were not changed by either treatment. 4. Total water excretion was much higher in the colostomised plus caeca-ligated chickens than in other 3 groups fed both types of diet (P < 0.05). 5. The amount of faecal water excretion was increased by cecal ligation in colostomised chickens fed either diet (P < 0.01). 6. No effect of any treatment on water balance was observed in chickens fed either diet. 7. It is concluded that the lower intestine plays a useful role in the water economy of chickens fed a low-protein diet or a low-protein diet supplemented with urea.

Effect of fasting on small intestinal antiperistalsis in the Nicholas turkey (Meleagris gallopavo)

Small intestinal refluxes (SIRs) were monitored in the gastrointestinal tract of Nicholas turkeys via implanted strain gage transducers and radiographic observations. It was determined that reflux of ingesta from the small intestine into the gizzard was a result of a single antiperistaltic contraction. Radiographic observation indicated that the antiperistaltic contraction originated in the ileum 88% of the time and the duodenum 12% of the time. Each antiperistaltic contraction was preceded by a single peristaltic contraction. No gastric contractions occurred during SIRs. Fasting for 12 to 24 hr significantly increased the frequency of occurrence of SIRs in the Nicholas turkey (P < 0.0001) but had no significant effect on the velocity of the peristaltic and antiperistaltic contractions or on recovery time to pre-SIR gastric contractile frequency. The pooled mean velocity of peristaltic contractions was determined to be 10.55 +/- 3.68 cm/sec, and that of antiperistaltic contractions was determined to be 12.12 +/- 3.69 cm/sec. The pooled mean recovery time to pre-SIR gastric contraction frequency was 28.31 +/- 8.25 sec. It has been suggested that the SIR may be a mechanism of maximizing nutrient utilization by the turkey.

Significant role of the nitrogen recycling system through the ceca occurs in protein-depleted chickens

This study focuses on the role of the ceca in nitrogen nutrition in chickens (Gallus domesticus). Urea is a very good nitrogen tracer for these studies. Little urea is synthesized by chickens due to the absence of carbamyl phosphate synthetase, an essential enzyme initiating the urea cycle. Urea is utilized by chickens when crystalline amino acid diets low in nonessential nitrogen or diets containing low concentrations of intact protein are fed, and most ureolytic activity is found in the ceca. Dietary urea was absorbed intact from the upper intestine of the chicken. The absorbed urea was excreted into ureteral urine that refluxed from the cloaca into the colon and ceca where urea was degraded to ammonia. Presumably the ammonia was incorporated into amino acids by cecal microorganisms and some urea, amino acids and proteins were absorbed from the ceca. These were utilized by the chickens. A beneficial role of ceca in the nitrogen metabolism in the chicken is, therefore, conservation of urinary nitrogen in protein-depleted chickens.

Ligation of caeca improves nitrogen utilisation and decreases urinary uric acid excretion in chickens fed on a low protein diet plus urea

1. The effect of the ligation of the caeca on nitrogen utilisation and nitrogen excretion was examined in conventional chickens fed a diet containing 50 g protein/kg plus urea. 2. Ligation of the caeca significantly improved nitrogen balance and utilisation by up to more than 2 times as much as those of controls (P < 0.05). 3. The treatment significantly decreased uric acid excretion by 77 mg nitrogen/day (P < 0.01) and also total nitrogen excretion (P < 0.05): the former decrease almost explained the latter. 4. No effect of the ligation of caeca on urea and ammonia excretion was observed. 5. It is concluded that nitrogen metabolism in chickens is affected by possible changes in caecal fermentation by preventing entry into the caeca of substances from urine and digesta.

Digestibility of water-soluble pectin and organic acid losses in intact or cecectomized adult cockerels

Two experimental diets consisting of a basal diet either undiluted or diluted with 1% pectin-based gelling agent were given to intact or cecectomized adult cockerels for a balance experiment. The digestibilities of the water-soluble added pectin were 83.2 and 61.4% in intact and cecectomized birds (P < .05), respectively. Lactic acid excretion varied from 407 to 2,692 mg/kg, acetic acid from 790 to 1,214 mg/kg, propionic acid from 108 to 240 mg/kg, and butyric acid from 50 to 90 mg/kg dry matter intake. Organic acid excretions were the lowest for intact birds fed the basal diet and the highest for cecectomized birds fed the pectin diet. Addition of pectin induced an increase (P < .001) in organic acid excretion, especially for lactic acid in cecectomized birds. Organic acid excretion was greater (P < .001) in cecectomized than in intact cockerels. The increase in organic acid excretion induced by pectin addition amounted to 9 and 62% of the digested fraction of pectin in intact and cecectomized cockerels, respectively. The results showed the water-soluble nonstarch polysaccharides to be digested both in ceca and upper tract. It was also shown that the major part of organic acids produced from fermentation are absorbed in the ceca.

Interspecific variation in sugar and amino acid transport by the avian cecum

Previous studies of cecal sugar and amino acid transport in the domestic chicken led to a widely held generalization that the avian cecum is unimportant as a site of nutrient transport. In fact, we found that the uptake capacity of the cecum for hexose sugars and amino acids is substantial in some species of birds. Cecal transport of glucose was measurable in all five study species (Canada goose, sage grouse, domestic chicken, red-necked phalarope, and rock dove), approached or exceeded intestinal levels in the grouse and phalarope, and accounted for between 0.1% (rock dove) and 49% (sage grouse) of the whole gut's integrated uptake capacity. Proline uptake averaged higher in the proximal portion of the cecum than in any region of the small intestine for all species but the goose. The ceca contributed between 2% (rock dove) and 25% (sage grouse) of the gut's integrated uptake capacity for proline. Similar ranges were found for fructose, lysine, leucine, and aspartate. Future studies should be undertaken to search for phylogenetic and ecological correlates of the interspecific variation in cecal transport and to determine how nutrient transport integrates with other functions of the avian cecum.

Absorption by the cecum of wild birds: is there interspecific variation

The major functions proposed for the avian cecum--energy balance and osmoregulation--involve absorption of material from the cecum, yet little is known of these absorptive processes in wild birds. The magnitude of transport of compounds from the ceca depends on the concentrations of compounds in the ceca, the presence of transport pathways for those compounds, and the size of the reabsorptive surface. Interspecific variation in size of avian ceca is well documented, but the other two determinants of absorption are much less well studied. All ceca examined contained acetic, propionic, and butyric acid; water content varies from less than 70 to greater than 90%. Most other constituents have been quantified in just one or two species. A model for cecal transport, derived from studies of mammalian ceca but consistent with observations on birds, is described. A luminal (mucosal) Na+/H+ exchanger couples the absorption of Na+ to that of volatile fatty acids, which are absorbed in their uncharged (protonated) form; these two compounds are thereby mutually stimulatory in their absorption. The cecum also absorbs water, sodium, carbon dioxide, and probably some nitrogenous compounds (e.g., ammonia). Too few data exist to analyze interspecific variation in cecal transport in birds. However, variations in the following characteristics do exist: cecal contents, cecal absorptive surface area, transport characteristics of other regions of avian intestine (e.g., rectum), cecal transport among mammalian species, and histology of avian ceca. Studies of the physiological consequences of these variation should yield insight into the function and contributions of the avian cecum.