A study of the growth of the alimentary tract of the young cockerel

Nutrients central to maintaining intestinal absorptive efficiency and barrier integrity with fowl

The small intestinal mucosa acts to recover nutrients from the lumen while providing a barrier against potential hazards. Its unstirred water layer (USWL) at the lumen interface involves membrane associated mucin linearly protruding from underlying microvilli that entangles secretory mucin released from local goblet cells. Both mucin sources are dominated by repetitive O-glycosylated areas dependant on threonine, serine, glycine, and proline. Secretory mucin differs from membrane attached mucin by further employing multiple cystines that interconnect these areas into a net-like molecular sieve. All of the glycosylated areas have ionizable acidic groups credited with reducing pH from that in the lumen to create a micro environment favoring enzymes finalizing digestion while optimizing nutrient terms for absorption. Erosion of the USWL and/or abuse of the membrane due to lumen threats require continuous repair. The aforementioned amino acids are necessary in substantial amounts while vitamin B6 collaborates with vitamin A as meaningful cofactors for mucin synthesis. Marginal inadequacies of these nutrients during inordinate demand are expected to impair mucin replacement. In turn, marginal increases in feed conversion likely occur while fostering the probability of necrotic enteritis together with gizzard erosions. Abuse of the absorptive membrane is of particular concern from fatty acid hydroperoxides because of their continual presence in feed and inability of the USWL to provide protection. These hydroperoxides threaten membrane integrity by their inclusion in micelles during digestive events with fat thereby permitting transit through the USWL. Once coalesced with membrane phospholipids, structural aberrations are visualized as interfering with nutrient recovery while enabling leakage of cell contents to potentiate wet excreta. Inclusion of dietary vitamin E along with vitamin A into micelles with fatty acid hydroperoxides provides relief by quenching further peroxidation. Assuring cystine, threonine, glycine, and serine that are directly available as such together with vitamins A, E, and B6 represents one approach toward optimizing maintenance of the intestinal mucosa.

Metabolisable energy content of diets and broiler performance as affected by wheat specific weight and enzyme supplementation

1. Two experiments were performed with male, Ross broiler chicks to study the relationship between wheat specific weight and performance parameters and the effects of xylanase inclusion in diets of different wheat specific weight (SW). 2. In both studies wheat was incorporated at 667 g/kg and a protein concentrate based on soyameal 50, full fat soyameal, extrupro and herring meal and formulated to provide (g/kg) crude protein 370, crude oil 140, crude fibre 45, crude ash 110 was incorporated at 333 g/kg. 3. In Experiment 1, 3 wheats (69, 67, 57, SW respectively) without or with enzyme (Avizyme TX, Finnfeeds International) and in Experiment 2, 6 wheats (81, 77, 76, 70, 64, 61 SW respectively) were used and diets were fed ad libitum to individually caged birds. 4. In Experiment 1 the feeding period was 7 to 28 d and a total excreta collection was made from 14 to 20 d for determination of apparent metabolisable energy (AME) content. Experiment 2 started at 4 d with excreta collections from d 6 to 9, 10 to 12 and 13 to 19 inclusive for AME measurements. 5. In Experiment 1 there were no significant effects of wheat on dry matter (DM) intake but liveweight gain (LWG) and gain:food were significantly better for 67 SW than for 57 SW. Food enzyme inclusion improved LWG and gain:food but there was a significant wheat/enzyme interaction for gain:food with no improvement due to enzyme addition for 67 SW but a 5% improvement for 57 SW. There was no significant effect of wheat or enzyme addition on the measured AME contents of the diets. 6. In Experiment 2, although not statistically significant, there were large numerical differences in food intake between diets, with the lowest values occurring for 64 SW. For the complete period, wheat variety tended to affect LWG (P=0.057) with the best and worst results recorded for the 2 low SW wheats. Gain:food was significantly affected by wheat, the poorest values occurring with 64 SW and the best with 77 SW Diet AME content was also affected by wheat variety (P<0.01) but the low result obtained for 61 SW was not mirrored in the gain:food value. The lack of correlation between diet AME values and gain:food could not be attributed to differences in protein or amino acid content of the diets. 7. In Experiment 2 diet AME content increased from period 1.1 (6 to 9 d) to period 2 (13 to 20 d) by 7% but interpretation is hampered by the short adaptation period (2 d) prior to period 1.1. The AME values obtained in both studies during the 3rd week of age were towards the upper end of the range of values in the literature. 8. In Experiment 2 there was a good correlation (r2=0.95) between SW and wheat starch content and between SW and calculated wheat AME content (r2=0.40, P<0.001) but a poor correlation between SW and gain:food. There was also a high correlation between wheat AME content and starch content (r2=0.41, P<0.001). Taken together with the results of Experiment 1 it appeared that starch content is a better measure of wheat quality than specific weight.

Weight of internal organs and carcase yield of early food restricted broilers broilers

1. Effects of food restriction on growth rate and relative growth rates of supply organs (liver, heart, lungs and kidneys, digestive tract) and demand organs (breast, back, thighs, abdominal fat) of broiler chickens were studied. 2. Birds were restricted in intake to 50% (group FI 50) or 75% (group FI 75) of ad libitum from 5 to 11 d of age; all birds were fed ad libitum from 12 to 39 d of age. 3. Relative growth rates from 12 to 39 d of age of group FI 50 were higher (P < 0.05) than group FI 75 and control group. 4. No significant differences in food conversion ratio, carcase fat and abdominal fat between groups were observed. 5. At 12 d of age, relative weight of the empty digestive tract of group FI 50 was higher (P < 0.05) than that of the control group and group FI 75. 6. The increased weight of the empty digestive tract may have contributed to the ability of the chickens to achieve compensatory growth after the restriction period.

Scanning electron microscopic observations on the intestinal villi in growing White Leghorn and broiler chickens from 1 to 30 days of age

1. To obtain intestinal morphological data demonstrating the faster growth rate in broiler (BR) than in White Leghorn (WL) chickens, villi of the duodenum, jejunum and ileum were examined from 1 to 30 d of age by scanning electron microscopy. 2. At the first day after hatching, villi of each intestinal segment showed a finger-like shape in both breeds. Villi developed to a plate-like shape in the duodenum, a wave-like shape in the jejunum and a tongue-like shape in the ileum at 30 d of age via the common plate-like villi at 10 d of age. The fundamental villous shape and arrangement seem to be accomplished by 10 d of age; two types of obliquely elongated plate-like villi showed a zigzag arrangement, adjoining at an angle of 40 degrees to 60 degrees like an oblique T-shape. It is suggested that such a villous arrangement would be more effective for nutrient absorption by inducing a long zigzag flow of ingesta. 3. Compared with WL, even at the first day after hatching BR had many more developed epithelial cell protrusions over the whole apical surface of the duodenal villi. In WL the protrusions were not so apparent and located only in the central area of the villous tip. Furthermore, at 10 d of age BR showed more developed and larger villi, many wider microvilli at the apical portion of villi and more active extrusions of epithelial cells from the tip of the duodenal and jejunal villi. 4. These morphological characteristics of villi in early life in BR suggest a greater absorptive surface area and a more active intestinal function, permitting the faster growth rate of BR immediately after hatching.

Determination of bile acid pool size, turnover time, and distribution of male broiler chicks during the first 6 weeks posthatch using SEHCAT, a gamma ray-emitting bile acid analogue

A bile acid analogue, SEHCAT (tauro-23-75SE-selena-homocholic acid), was used to determine bile acid pool size, turnover time, and distribution in the developing broiler chick. Bile acid pool size was significantly affected by age and followed a quintic trend (a fifth degree polynomial). It remained steady until 30 days of age when it decreased significantly and then rose significantly at 37 days of age. The bile acid pool half-life remained constant until 28 days of age when it increased significantly and then held steady until it increased again at 8 wk of age following a quartic trend. The distribution of bile acids was affected by age with the amount in the gizzard, duodenum, cloaca, liver, and gall bladder varying significantly with age. Jejunal, ileal, and cecal bile acids did not vary significantly with age. Liver bile acid levels followed a quintic trend, rising until 23 days of age and dropping sharply at 30 days of age and holding steady.

Caecal growth in the domestic fowl following surgical manipulation

1. Some effects of removing increasing proportions of the left caecum on the remaining caecal tissue and on the right caecum were studied in young chicks during a period of 35 d. The chicks were 22 d old when the operations were carried out. 2. No differences were detected between the gains in weight of the control and experimental groups of birds. 3. A marked negative linear relationship was observed between the dry weight of the amount of caecal tissue removed when the birds were 22 d old and weight of the left caecum at the end of the experiment. 4. The average growth rate of the left caecum (g dry tissue/week) was found to be dependent on the estimated weight of caecal tissue remaining after surgery. 5. No evidence was obtained to indicate that the growth of the right caecum responded to the removal of the left caecal tissue. 6. The morphology and histology of the operated caeca were found to be similar to the equivalent regions of the unoperated caeca. Surgical interference was not followed by any major changes in mucosal architecture. 7. In birds which had experienced unilateral caecectomy, the discharge of caecal faeces usually stopped for about 2 d. When caecal defaecation was resumed, the pattern of defaecation appeared to be the same as that observed in sham-operated birds with both caeca intact.