Interactions between different source of fiber and threonine on gastrointestinal development, nutrients digestibility and immune system of broiler chickens

Aslani Kordkandi, Gholamreza (2020) Interactions between different source of fiber and threonine on gastrointestinal development, nutrients digestibility and immune system of broiler chickens. Doctoral thesis, University of Mohaghegh Ardabili.

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Abstract

Research Aim: The study was carried out to investigate the effect of different sources of fiber and different levels of the threonine amino acid on growth performance, gastrointestinal tract development and immune system of broilers. Methodology:. In the first experiment, pectin and cellulose along with two sources of fiber, pea hull and sugar beet pulp were examined in terms of chemical composition, viscosity, water holding capacity and metabolizable energy. In the second experiment, the effect of pectin and cellulose (Vitacell), and three levels of threonine (recommended level and 10% less or more) were studied on growth performance, nutrient digestibility, organ relative weights, jejunum morphometry of 180 male Ross 308 chicks reared in cage by employing a completely randomized design with 2×3 factorial arrangement for a period of 24 days. The third experiment studied the effect of two commercial fiber sources of pea hull and sugar beet pulp and the three levels of the amino acid, threonine, on growth performance, nutrient digestibility, digesta characteristics, digestive and immune organ weights, humoral and cellular immunity and morphology of male chicks jejunum, and similar to the second experiment was done in cage. The fourth experiment was performed to investigate the effect of litter type (litter containing wood shaving floor and wired floor) and different levels of threonine amino acid (as mentioned above) on growth performance, gastrointestinal tract weight, digestive organ weights, digesta characteristics and jejunal morphometry of male chicks by employing a completely randomized design with a 2×3 factorial arrangement. Findings: In the first experiment, some differences were observed in chemical composition, viscosity, water holding capacity and metabolizable energy of the studied fibers. The amount of apparent metabolizable energy, crude protein, crude fiber, NDF and ADF of pea hull was more than sugar beet pulp. However, although the two synthetic fibers of cellulose and citrus pectin were almost similar in terms of gross energy, dry matter, ash and crude fat, pectin had higher crude protein than cellulose (2.15 vs. 0.7%). In the second experiment, cellulose caused an increase in feed intake and weight gain, and a decrease in feed conversion ratio in starter and grower periods and growth (P <0.05). Moreover, the deficient level of threonine compared with the recommended and excess levels caused a decrease in feed intake, weight gain and feed conversion ratio during the experimental period. The highest weight gain was belonged to the chickens on recommenced and excess levels of threonine in the presence of cellulose (P <0.05). Nutrients digestibility increased by cellulose compared with pectin (P <0.05). The deficient level of threonine decreased the digestibility of nutrients compared with the recommenced and excess levels (P <0.05). The relative weight of gizzard was increased by dietary cellulose (P <0.05). Diets containing cellulose and recommenced or excess levels of threonine increased villi height, villi surface area and the number of goblet cells in jejunum (P <0.05). The highest villi height and surface area, and the number of goblet cells were observed by cellulose and threonine recommenced or excess levels (P <0.05). In the third experiment, pea hull increased feed intake (in starter period) and improved weight gain and feed conversion ratio (during the starter and grower periods) (P <0.05). Diet containing deficient threonine level reduced feed intake and weight gain, and increased feed conversion ratio during the starter period (P <0.05). The lowest feed intake was observed in the presence of deficient level of threonine and sugar beet pulp (P <0.05). Nutrients digestibility were significantly increased by pea hull compared with sugar beet pulp (P <0.05). Pea hull increased the relative weight of gizzard compared with sugar beet pulp and the lowest relative weight of bursa of Fabricius was observed with the deficient level of threonine (P <0.05). Pea hull increased the percentage of tibia ash compared with sugar beet pulp (P <0.05). The recommended and excess levels of threonine compared with the deficient level increased the response of immunity against sheep red blood cell and Ig G, as well as the cellular immunity in the first 12 hours following Phytohemagglutinin injection (P <0.05). In the fourth experiment, the wood shaving litter increased feed consumption and weight gain (during the starter period) in comparison with wire floor (P <0.05). The recommended and excess levels of threonine compared with the deficient level increased feed intake and weight gain (during the grower and whole experimental periods) and improved feed conversion ratio (in starter and whole experimental periods) (P <0.05). Wood shaving floor along with the excess level of threonine showed the highest feed intake during the grower period (P <0.05). Wood shaving, also, reduced the abdominal fat (P <0.05). The wood shaving increased villi height and surface area, and the thickness of muscle layer of jejunum (P <0.05). The recommended and excess levels of threonine in comparison with the deficient level increased villi height, villi height to crypt depth ratio, villi surface area and the number of goblet cells (P <0.05). There was a significant interaction between the type of litter and threonine levels on villi surface area and the highest surface area was observed by wood shaving floor and threonine recommended and excess levels (P <0.05). Conclusion: Dietary soluble fibers in comparison with the insoluble fibers reduce the performance of bird by increasing the digesta viscosity and impairing the development and function of the gastrointestinal tract. The Deficiency of threonine also worsens the bird's growth response due to its adverse effects on intestinal development, the immune system, and nutrient digestion. The most important interactions between fiber and dietary threonine levels were observed in the starter period in relation to weight gain. The recommended level of threonine leads to favorable responses and thus, there is no need to add the extra levels. Consumption of fiber from the litter source is also an issue that has significant effects on the development of the digestive tract, nutrient digestibility and growth performance.

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