1. A study was conducted on the pattern of development of the intestinal mucosa of the Steggles x Ross (F1) strain of broiler chickens reared on a commercial starter diet. The mechanisms underlying the structural changes were also assessed. 2. In relation to body weight, small intestinal weight peaked at 7 d of age and declined subsequently. There was also a reduction in the relative weights of the gizzard and yolk sac with age. The length of the small intestine and its regions increased with age. 3. Crypt depth increased with age in the duodenum and jejunum while villus height increased significantly with age in all three regions of the small intestine. There were also significant changes in apparent villus surface area in the three regions, while interactions between age and intestinal region were significant in the case of crypt depth and villus height. 4. There were significant differences between the age groups in the mucosal protein content of jejunal and ileal homogenates, both tending to peak at 7 d of age. The DNA content of the intestinal mucosa declined with age in the three regions of the small intestine. While there was an increase in RNA content in the duodenum and ileum, there was a reduction in the jejunum. 5. Protein: DNA ratio increased between hatch and 21 d of age in all intestinal regions. Protein: RNA ratio decreased with age in the duodenum and ileum but increased in the jejunum. There were significant increases in RNA: DNA ratio in the duodenum and ileum but no changes were observed in the jejunum. The interactions between age and intestinal region were significant for all biochemical indices assessed. 6. At all ages, enterocyte proliferation at the jejunum was completed and quantifiable within 1 h of administration of 5-bromo-2'-deoxyuridine (BrDU). Subsequent assessment revealed an increase in crypt column count and number of BrDU-labelled cells. The rate of cell migration increased with age while there was a decline in the distance migrated in proportion to mucosal depth. The estimated life-span of enterocytes and time spent by enterocytes in the crypt varied with age. In d-old and 7-d-old chicks, migration was complete or nearly complete within 96 h of cell birth. 7. Although the intestinal mucosa of the strain was structurally developed at hatch, there was much change in structure with age, especially over the first 7 d post hatch. The rate of development was most rapid in the jejunum but the other regions are also important, on account of villus height or relative length of the region.
A study was conducted to evaluate the response of broiler chickens to a commercial synthetic mannan oligosaccharide, Bio-Mos 2 (BM), included in sorghum/lupin-based diets at 0.0, 1.0, 3.0 or 5.0 g kg À1 diet. The diets were fed between 7 and 28 days of age, and both the gross response and mechanisms involved were evaluated. The highest level of BM in the diet resulted in longer (P < 0.01) jejunal villi than those observed at other levels of supplementation. The RNA content of the ileal mucosal homogenate was signi®cantly greater (P < 0.05) in chicks raised on diets supplemented with 3.0 and 5.0 g BM kg À1 diet than in other groups. The protein/DNA ratio of the jejunal mucosal homogenate was also higher (P < 0.05) in chicks fed the 1.0 g BM kg À1 diet than in chicks fed the other diets. The protein/RNA and RNA/DNA ratios in ileal homogenates were signi®cantly (P < 0.01) in¯uenced by the presence of BM in the diet. There were signi®cantly greater speci®c activities of maltase (P < 0.01), leucine aminopeptidase (P < 0.05) and alkaline phosphatase (P < 0.001) in the jejunum as a result of supplementation with BM. Digestive enzyme activities in the ileum were unaffected. L-Tryptophan uptake by jejunal brush-border membrane vesicles was signi®cantly higher (P < 0.01) in chicks raised on the 5.0 g BM kg À1 diet than in the other chicks. The supplement led to minor improvement in body weight but no improvement in feed conversion ratio. These effects were related to changes in digestive enzyme activities and, perhaps, amino acid transport. INTRODUCTIONOligosaccharides occur naturally in many feed ingredients, the most common natural forms being the raf®nose series oligosaccharides. Raf®nose series oligosaccharides do not succumb to animal enzymes and tend to accumulate towards the posterior end of the gastrointestinal tract (GIT) where they are digested by microbial enzymes, to release gases that cause¯atulence in non-ruminant animals. 1,2 Previous research has therefore tended to attribute the poor growth of animals on legume seeds to the presence of oligosaccharides. This has been disputed by more recent research.
In poultry nutrition, most attention is given to protein products, due to the importance of protein as a major constituent of the biologically active compounds in the body. It also assists in the synthesis of body tissue, for that renovation and growth of the body. Furthermore, protein exists in form of enzymes and hormones which play important roles in the physiology of any living organism. Broilers have high dietary protein requirements, so identification of the optimum protein concentration in broiler diets, for either maximizing broiler performance or profit, requires more knowledge about birds' requirements for protein and amino acids and their effects on the birds' growth performance and development. It also requires knowledge about the protein sources available that can be used in poultry diets. The broad aim of this review is to highlight the importance of some of the available high-quality specialized protein products of both animal and plant origins which can be explored for feeding broiler chickens. Minimization of the concentration of anti-nutritional factors (ANFs) and supplementation with immunologically active compounds are the main focus of gut health-promoting broiler diets. These diet characteristics are influenced by feed ingredient composition and feed processing. The general hypothesis is that these protein products are highly digestible and devoid of or contain less ANFs. Feeding these products to broiler chicks, especially at an earlier age, can assist early gut development and digestive physiology, and improve broiler growth performance and immunity.
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