عنوان مقاله [English]
Introduction Like to broiler chickens most of the ostrich breeding cost is related to the price of nutrition. Given the higher ability of ostriches to using the dietary fiber, it is expected that the using of cheaper feeds may be provide diet with lower prices. Agricultural by-products such as sugar beet pulp and various types of brans are rich sources of fibers, each with different percentages of soluble and insoluble fibers. Ostrich (Struthio camelus) has a long rectum (about 8 meters) that occupies about 57 % of the length of its gastrointestinal tract, but in the broiler chicken the rectum is only about 3 % of gut tract. The microorganisms in the ostrich's large intestine can digest 38% of cellulose and 68% of hemicellulose. The dietary fiber is divided into two types of water-soluble and water-insoluble. The water-insoluble fibers are including cellulose, lignin and a part of hemicellulose. Due to the higher passage rate of the digestive tract, they are less fermentable than soluble fibers. Water-soluble fibers are mainly including pectin, gum, and mucilage. Soluble fibers reduce the contact of enzymes with digesta, due to increase viscosity, thereby reducing digestion and absorption of nutrients in the gastrointestinal tract. Due to the fact that the effect of soluble and insoluble fibers in the digestive tract is different from each other and so far no research has been done on the effect of fiber source in ostriches. This study was aimed to determine the nutritional value and digestibility of nutrients of diets containing two fiber sources soluble and insoluble in ostrich chicks.
Materials and Methods In order to evaluate the feasibility of using the higher levels of soluble and insoluble fibers in ostrich’s diet, this experiment was undertaken using 30 ostrich chicks in a completely randomize design with 5 treatments and 6 replicates in each treatments (one bird in each replicate) in three periods; prestarter (1- 2 months), starter (2- 4 months) and grower (4-6 months). The experimental treatments were as follows: 1-Control diet with standard fiber level, 2- Treatment contains 2% more soluble fiber than control (sugar beet pulp as the source of soluble fiber), 3- Treatment contains 4% more soluble fiber than control (Sugar beet pulp as a source of soluble fiber), 4- Treatment contains 2% more insoluble fiber than control (wheat bran as a source of insoluble fiber) and 5- Treatment contains 4% more insoluble fiber than control (wheat bran as a source of insoluble fiber). A total 30 ostrich chicks were reared at an average weight of 3082± 202.37 grams in cages. In order to determine the digestibility of nutrients, AME and AMEn, the total excreta were collected. Nutrients contents of feed and excreta were measured according to AOAC (1997) methods. The raw energy of feed and excreta was measured by the calorimeter bomb apparatus. Megazim kit was used to measure the total dietary fiber (AOAC Official Method 991.43). The amount of soluble fiber was calculated by subtracting the insoluble fiber from total dietary fiber. Data were analyzed using SAS software (2002) using mixed procedure for repeated measurements with a significance level of 0.05 by Tukey Cramer method.
Results and Discussion Data showed that fiber source had no effect on nutrient digestibility. Ostrich rectum is longer than its small intestine (the rectum occupies 57% of the digestive tract and small intestine occupies 29% of the digestive tract) and a good place to ferment the plant fibers. Fiber digestive bacteria such as fibrobacter succinogenes and ruminococcus flavafaciens in ostrich's ceca and other fermenter bacteria in the ostrich's rectum enable it to have the proper ability to utilize fiber sources. Since the beginning of the experiment was from the age of one month, ostrich chicks had sufficient ability to use different fiber sources. The difference in the rate of digestive contents through the consumption of soluble or insoluble fiber sources had no significant effect on digestibility of nutrients. Soluble and insoluble fibers digestibility and ash digestibility increased with ageing (p < 0.0001). As birds age increase the bacterial activity increase in the rectum and ceca. There was no significant difference in AME in treatments that had more soluble fiber compared with the control group, but AME and AMEn increased significantly with increasing insoluble fiber compared to treatments that had more soluble fiber (p < 0.0001). Which is probably related to the effect of insoluble fiber in the small intestine. Insoluble fiber diets improve the efficiency of nutrients utilization due to increasing the villi height to crypt depth ratio, therefore increased AME and AMEn. The differences in AME and AMEn with consumption of insoluble fiber source in comparison with other treatments are related to the greater effect of different fiber sources on the small intestine. Insoluble fiber decreases the viscosity of digestive contents and increases the effect of digestive enzymes secreted from intestinal cells (such as alpha amylase) and improve the digestion of starch and other nutrients and increase the energy obtaining from the diet by the ostriches. AMEn significantly increased with aging that may due to the increase of the activity of older birds, increase the energy required for maintenance and activity and hence more consumption of energy by the bird. The microbial population of the cecum and colon of the ostrich (from 3 weeks onwards) is similar to the rumen, which has the ability to ferment the fiber and produce volatile fatty acids, which these volatile fatty acids provide part of the metabolizable energy.
Conclusion According to the results of this study, a suitable range for soluble and insoluble fibers in ostriches diets from one to two months old were suggested to be 7.5 to 11.5 percent and 16 to 20 percent, at the age of 2 to 4 months 7.6 to 11.6 percent and 20 to 24 percent and at the age of 4 to 6 months 8.25 to 12.25 percent and 25.5 to 29.5 percent, respectively.