| چکیده انگلیسی مقاله |
Introduction: In poultry breeding farms, density is one of the important factors in terms of welfare, production, and health in poultry. Density can be defined as the number of birds per unit area or kilograms per unit area. High density reduces body heat loss, bad air quality due to its improper exchange, increased ammonia level, and reduced access to food and water, which leads to reduced feed efficiency. It seems that the stress caused by high density can upset the balance of the microbial population of the digestive system. Improving the microbial population of the gastrointestinal tract through the addition of different sources of insoluble fiber may be beneficial for the development of the health and growth performance of broiler chickens grown at high densities. In Iran, rice hull is obtained as waste from rice grain processing, which contains a high percentage of insoluble fibers. Sunflower husks, as a byproduct, contain a significant amount of fiber. On the other hand, the sunflower hull is the outer covering of the sunflower seed. Sunflower hull and rice hull have high fiber and low energy. Considering the negative effects of high density and the positive impact of fibrous sources, the present study investigated the influence of different insoluble fiber sources on the performance and microbial population of the caecum in broiler chickens raised at high density. Materials and methods: The experiment was performed with 390 one-day-old broiler chicks of Ross 308 strain in a completely randomized design with a 2×3 factorial arrangement and five replications. The experiment included two density levels (10 and 16 birds per square meter) and three fiber sources (diet without fiber, diet containing sunflower hull, and rice hull). Characteristics of feed intake, body weight gain, and feed conversion ratio were measured regularly and blood factors and bacterial counts were sampled on the last day after slaughter. Results and discussion: There was no significant difference between the fiber source and density in different growing periods on average feed consumption and relative weight of different carcass components (P<0.05). High density resulted in a decrease in feed intake in the starter, finisher, and overall period compared to normal density (P<0.05). Birds fed with different fiber sources showed higher feed intake compared to the control treatment in the growth, finisher, and overall period of the experiment (P<0.05). Birds fed with a diet containing sunflower hull and rice hull in normal density conditions showed higher weight gain compared to other treatments in the final period. The best feed conversion ratio was observed in the rice hull treatment at the normal density level in the final and overall period of the experiment (P<0.05). Birds fed with sunflower hull in normal density and rice hull in high density showed a significant increase in blood HDL concentration compared to other treatments (P<0.05). Birds reared at high density showed significantly higher blood glucose, cholesterol, and LDL concentrations compared to birds reared at normal density (P<0.05). It may be the reason for the increase in LDL, glucose, and blood cholesterol concentration in high density, negative responses such as an increase in corticosterone level, an increase in lipid peroxidation, production of free radicals, and an increase in immunosuppression in chickens reared in high density. The interaction effect of fiber source and density level had no significant effect on Coliform and Escherichia coli populations in cecum (P<0.05). In the presence of sunflower hull and rice hull, high density led to a significant increase in the population of cecal Lactobacillus compared to normal density (P<0.05). In the absence of fiber, high density caused a significant decrease in the cecum Lactobacillus population compared to normal density (P<0.05). Diet is a major environmental factor that can directly affect the nature of the microbiota in the host. Conclusions: The results of this study showed that the use of fiber could improve the feed conversion ratio in high-density rearing conditions compared with birds fed a diet free of fiber and in normal-density rearing conditions. In addition, the use of sunflower hull and rice hull led to increased feed intake, weight gain, cecal Lactobacillus population, and improved feed conversion ratio in broiler chickens. Compared to birds reared at normal density, birds reared at high density showed a decrease in feed consumption, a decrease in weight gain, and an increase in the population of the cecal Coliform population. |