Dietas de fontes de fibra não forrageira com redução de amidos para bovinos confinados

Abstract

High levels of starch in the diet can lead to a reduction in the digestibility of nutrients and lead to metabolic disorders in the animal, so the inclusion of fiber in the diet is essential, and sources containing higher concentrations of FeNDF should be prioritized, since this effectively stimulates rumination and rumen motility. Thus, the objective of this study was to evaluate the consumption and digestibility of diet ingredients in confined steers, as well as parameters of rumen fermentation, blood biochemistry, microbial protein synthesis and ingestive behavior, using diets with non-forage fiber sources and reducing the starch levels. The experiment was carried out in the experimental area of the Faculdade de Ciências Agrárias (FCA) of the Federal University of Grande Dourados, using 5 crossbred rumen-cannulated steers (416.9 ± 16.5 kg BW), randomly divided into a 5 x 5 Latin square. The experimental diets were formulated to contain the following percentages of ground corn in the total diet: 40, 20, 10 and 5%, and an additional treatment of 5% corn complexed in the pellet, which were distributed daily at 8:00 am. All diets were isonitrogenated with 13% CP and balanced according to the NRC, 2016. The animals that received diets with 10 and 5% ground corn had higher DM intake, with 8.26 and 7.97 kg/ day, compared to animals that received a with 20% and 5% complexed to the pellet, with respective 7.76 and 7.85 kg/day. In relation to neutral detergent fiber, the cattle that received treatments M10, M5F and M5P (2.80; 2.83; 2.81 kg/day respectively) had the highest consumption values, being lower for those fed with the M40 treatment (1.88 kg/day). The animals supplemented with a diet containing 5% of ground corn, obtained the highest DM digestibility in relation to the others (around 83.5%). The steers supplemented with the M10 and M5F diets showed the highest starch digestibility (96% and 98.95%, respectively) in relation to the other treatments, and regarding the NDF digestibility, the animals that received the M5F diet showed the best result. (87.6%), when compared to the other treatments, with the M40 and M20 diets having the worst results (80.9% and 79.9%). The lowest value of N excreted in the feces (41.61 g/day) was for cattle that received a diet with 5% corn, and consequently had higher values of absorbable N (134.15 g/day), as well as o N retained with a value of 115.70 g/day. Therefore, a diet containing 5% of ground corn is recommended, since the reduction in the level of starch and the increase in fiber improved parameters such as digestibility of DM, NDF, starch and CP, consequently resulting in greater microbial synthesis.