Avaliação de um “blend” de óleos essenciais na fermentação in vitro de dietas a base de forragem e de alto concentrado para ruminantes

Abstract

Ionophore antibiotics are the main additives used in ruminant diets with a known ability to manipulate rumen fermentation. Still, their use raises concerns about the possible development of antibiotic resistance mechanisms by bacteria. In this sense, secondary plant compounds, such as essential oils (EO = cinnamaldehyde and garlic oil), have been more recently studied as potential additives in the diets of ruminant animals that can be used to replace ionophores. Based on the above, the present work was developed to evaluate doses (equivalent to zero; 133; 266, and 350 mg/ (animal x/day)) of an EO blend (NE300) on the in vitro ruminal fermentation of diets based on forage (study 1, Marandu das Águas and dry grass) and high concentrate diet (study 2), with monensin as a positive control. For this, about 0.5000g of samples of Marandu grass or a high concentrate diet were weighed and placed in 100 mL amber flasks, in quadruplicate, to which the respective doses of additives (EO or monensin) were also added. as well as 40 ml of buffer and 10 ml of rumen inoculum. Afterward, the flasks received rubber caps and aluminum seal, being incubated at 39oC for 96 hours for the forage-based diet and 48 hours for the high-concentrate diet. The variables analyzed were total gas production, gas production rate, in vitro dry matter digestibility (IVDM), the concentration of ammonia and VFAs in the liquid in the flasks, and estimation of methane production. In study 1, the EO doses or the addition of monensin did not affect (p<0.05) the total gas production, the gas production rate, the IVDMD, the entirety production, and the proportion of VFA and the concentration of N-NH3. However, higher values (p>0.05) were found for kd, IVDMD, and N-NH3 for the forage obtained in the water than obtained in the year’s dry season, reflecting the former’s better nutritional value. NE300 doses caused a quadratic effect on DIVFDN, with no interaction effect between additive and forage. In study 2, NE300 doses did not affect the variables analyzed, but the addition of monensin reduced total gas production, kd, IVDMD, and N-NH3 concentration compared to NE300. Doses of EO NE300 equivalent to those recommended for use in practical situations (350 mg/animal/day) when tested in vitro did not influence the variables indicating changes in rumen fermentation when evaluated for Marandu grass-based and high concentrate diets. Therefore, higher doses should be evaluated in vitro and in vivo.