Grãos secos de destilaria em suplementos para bovinos em terminação a pasto

Abstract

DDG (Dried Distillers Grains) is a by-product of high nutritional value, resulting from the production of ethanol from grains such as corn and sorghum, and may be an alternative for inclusion in the supplementation of cattle on pasture. The objective was to evaluate the inclusion of increasing levels of DDG on the nutritional parameters and ruminal fermentation of cattle kept on pasture. Five steers, male, castrated, equipped with a rumen cannula weighing 450±50kg, aged 18 months, kept in Marandu grass pasture, and randomly distributed in a 5x5 Latin square were used. DDG was included in the supplements in the following proportions: 0, 100, 150, 200 and 300 g/kg DM. The variables evaluated were forage availability, intake and total apparent digestibility of nutrients, in situ ruminal degradability of DM and CP, balance of nitrogen compounds, microbial protein synthesis and rumen fermentation. Data were analyzed using SAS and submitted to analysis of variance, at a significance level of 5%, being evaluated by simple polynomial regression. The total availability of pasture and green matter presented averages of 2.0 t/ha and 1.3 t/ha, respectively, allowing selectivity by the animals. As the levels of DDG increased in the supplements, there was a decrease in the fraction “a” and a linear increase in potential degradability (DP), as well as in the effective degradability (DE) 5%/h (P= 0.004) of grain dry matter distillery dry. At the passage rate of 2%/h, DE had a quadratic effect (P=0.016) and had its highest value with the inclusion of 300g/kg (63.44%) of DDG. In the DDG protein degradation results, the “a” fraction was decreased and the DP increased linearly (P= 0.012). The highest DE rate was 41.57% with 300g/kg of inclusion (DE 2%/h), evidencing high protein escape in the rumen. Pasture consumption showed a quadratic behavior (P=0.032) and, according to its equation, the optimal level of inclusion of DDG for maximum consumption was 16.55%. Consumption may have been influenced by increased degradation of supplements, in view of a higher rate of passage, driving an increase in pasture consumption. The digestibility of NDF (P=0.001) and MO (P=0.046) increased with up to 200g/kg of DDG inclusion. There was a quadratic effect (P<0.05) on N-consumed (P=0.032), with no influence on the other parameters of the balance of nitrogen compounds. The concentrations of Isovalerate (P=0.001), branched-chain fatty acids (AGCR) (P=0.004) and the production of enteric CH4 (P=0.022) decreased linearly with the inclusion of DDG, showing a decrease in energy losses by the animals. The DDG proved to be a rich source of non-degradable protein in the rumen (PNDR) and given the data obtained, the recommended inclusion levels of DDG in supplements for pasture-raised cattle are from 150 to 200g/kg in DM.