Óleo essencial de Caju (Anacardium Occidentale l.) na fermentação ruminal in vitro de dietas com diferentes relações volumoso: concentrado

Abstract

Livestock farming is one of the sources responsible for expelling methane (CH4), originating from the enteric fermentation of ruminants, however, manipulation with the use of antibiotics to reduce production and improve the efficiency of use of diets by ruminants has been prohibited, for example in countries of the European Union. In the search for natural alternatives to replace antibiotics, plant essential oils (EO) are a good option, as they exert antimicrobial activity, especially against gram-positive bacteria. The cashew tree (Anacardium occidentale L.) is a plant originating in Brazil, and the antibiotic effect of its EO has been known for 60 years. Therefore, the objective was to evaluate the effect of adding cashew EO to diets with different forage:concentrate ratios on in vitro ruminal fermentation. The experiment was carried out at the Federal University of Northern Tocantins (UFNT), Campus de Araguaína - TO. Ruminal inoculum was obtained from three fistulated cattle (250 ± 25 kg body weight). The experiment was conducted in a randomized block design with a 4 × 3 factorial arrangement, with the factors being the three diets and three levels of oil addition, totaling nine treatments and four blocks (donor animals). The treatments consisted of three diets with different forage:concentrate ratios (100:0; 67:33, 33:67 and 0:100) and the addition of three levels of cashew EO (0; 1 and 2%). Ruminal dry matter degradation, gas production and methane production, a gas of environmental interest, were evaluated. The curves generated in gas production were compared using parallelism and identity tests. The remaining data obtained were subjected to analysis of variance, the means of the diets were compared using the Tukey test at a 5% probability of type I error. Analyzing the kinetics of ruminal fermentation, it was observed that the total production of gases ( parameter A) was higher for diets formulated with a higher proportion of concentrate and lower for diets formulated with a lower proportion of roughage, regardless of the level of inclusion of cashew essential oil. The inclusion of cashew essential oil in diets has little influence on rumen degradability in vitro and its effect on methane production in vitro depends on the forage:concentrate ratio of the diet. The inclusion of 1 or 2% of Cashew EO reduces the degradability of dry matter, but does not alter the degradability of organic matter. Diets with higher proportions of concentrate reduce methane production, and the inclusion of 1% cashew essential oil further stimulates this reduction.