Beef cattle finishing diets have high energy contents, which represents a challenge for the stability of ruminal ecosystem. With the increasing popularity of sugarcane silage by farmers, it becomes essential to understand the effect of supplementing with different levels and sources of non-fiber carbohydrates (NFC) on rumen metabolism and animal performance. The objective of this study is to quantify the effect of partial replacement of ground corn by flaked corn or citrus pulp in two levels of concentrate in the diet on performance, carcass characteristics, ruminal fermentation, degradation kinetics, ruminal passage of fiber, total digestibility of DM and starch. The study will consist of six experimental diets based on sugarcane silage with two concentrate levels on diet (60% or 80% concentrate on dry matter) and three sources of non-fiber carbohydrates (NFC): ground corn will be partially replaced for flaked corn or citrus pulp. For determining animal performance and carcass characteristics, 108 young Nellore bulls weighting approximately 350 kg will be used, housed in 36 concrete pens, three animals per pen, in a randomized block design with six replicates. Intake will be regulated for each stall by daily weighting of diet and orts. Periodic weighing of the animals after 16h starvation will be made to estimate average daily gain and feed efficiency. Fat deposition and muscle growth will be evaluated by ultrasonography at the beginning and end of the experimental period. Blood samples will be collected for dosage of serum glucose, urea nitrogen, total protein and albumins. For measuring ruminal kinetics six rumen cannulated Nellore steers will be used at a 6x6 Latin Square design. Total rumen mass and volume will be determined by rumen emptying. Samples will be taken from both, solid and liquid phases, for determining the size of the rumen pool and digest components. Samples from the diet, orts and rumen digest will be measured for nutrient content. Indigestible NDF will be estimated as NDF content after 264h of in situ incubation. Rumen liquid volume and rate of passage will be calculated using polyethylene glycol 4,000 MW.
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