The effect of Dietary Fiber Source and Threonine Level on Growth Performance, Nutrients Digestibility and Digesta Characteristics of Broiler Chickens in a Period of 24 Days

The aim of this study was to survey the effect of different dietary fiber source and thereonine levels on growth response, nutrients digestibility and some digesta characteristics of broiler chickens. A total of 180 day-old male Ross 308 chicks were used  in a completely randomized design with a factorial arrangement of 2×3 with 4 replicates of 6 birds each for a period of 24 days. The diets consisted of two fiber sources (pea hull and sugar beet pulp) with 5 percent and three levels of threonine (90, 100 1nd 110 percent of recommended level). According to the results, a significant interaction was found between fiber source and threonine level on feed intake (P<0.05), where the chickens on sugar beet pulp containing diet with deficient threonine consumed lower feed than those on similar diet containing pea hull. There were no significant interactions between fiber source and threonine level on birds’ weight gain and feed conversion ratio. Lower weight gain and higher feed conversion ratio were observed by sugar beet pulp than pea hull (P<0.05). Digestibility of dry matter, organic matter and crude fat, as well as apparent metabolizable energy was decreased by inclusion of sugar beet pulp in the diet (P<0.05). Deficiency of threonine in the diet decreased the digestibility of organic matter (P<0.05). The use of sugar beet pulp decreased pH value of gizzard and cecal digesta, and increased the viscosity of jejunal and ileal digesta in comparison with pea hull (P<0.05). Relative weight of gizzard was increased by pea hull compared with sugar beet pulp (P<0.05). In conclusion, compared with pea hull, sugar beet pulp by increasing digesta viscosity decreased nutrients digestibility and broiler performance, and except for feed intake, non-remarkable interaction was illustrated between fiber source and threonine level.