Óleos essenciais no metabolismo, na população microbiana e produção de metano entérico em ovinos

Abstract

The objective of this study was to evaluate the effect of a mixture of essential oils on ruminal metabolism, microbial population and methane production in sheep. Nine cannulated sheep of the Santa Inês breed (55 ± 11.1 kg) were used, which received a basal diet containing three levels of inclusion of essential oils (MSOE): zero (control), 200 (low) and 400 (high) mg MSOE / kg MS consumed. The experimental period lasted 69 days, divided into three periods of 23 days, the first 15 days for adaptation of the animals and the last 8 days for data and sample collection. The experimental design was the Latin square 3x3, with three squares simultaneously. For the measurement of fatty acids, ammoniacal nitrogen and microbial population, four collections of ruminal liquid were performed per period: Time 0; Time 24, Time 168 and Time 360. The concentrations of short chain fatty acids were determined using a gas chromatograph. Ammoniacal nitrogen was determined by steam distillation. In addition, nutrient digestibility (dry and organic matter, insoluble fiber in neutral and acid detergent, cellulose, hemicellulose and crude protein) was determined. The microbial nitrogen balance was analyzed by high performance liquid chromatography. The quantification of the different groups of microorganisms, such as total bacteria, Butyrivibrio fibrisolvens, Clostridium sp., Fibrobacter succinogenes, Anaerobic fungi, Ruminococcus flavefaciens and Selenomonas ruminatium was estimated by the amplification of 16S rDNA gene sequences with specific primers by the qPCR technique. A functional primer (mcrA) was used for the Archeae methanogenic. The counting of the number of protozoa was performed by light microscopy. For the measurement of methane emission, the animals were kept individually in respiratory chambers. There was no effect of the level of inclusion of MSOE on nutrient digestibility. As for dry matter intake, live weight of animals and methane production, a treatment effect was observed, in which treatment with 400 mg MSOE / kg DM consumed showed lower methane production, with live weight and dry matter consumption lower than the others. The protozoan population was higher in the treatment with 400 mg MSOE / kg MS consumed. As for microbial nitrogen, an increase in the control treatment was observed. There was no treatment effect on the microorganisms Total bacteria, Clostridium sp., Fibrobacter succinogenes, Total anaerobic fungi, Archeae methanogenic and Ruminococcus flavefaciens. The population of Butyrivibrio fibrisolvens, presented a quadratic effect, with an increase in the relative expression, relative to the control treatment, in the treatment with 200 mg MSOE / kg MS consumed. The population of Selenomonas ruminantium and protozoa presented an increase for the treatment with 400 mg MSOE / kg MS consumed. When time is taken into account, it can be seen that at time 0, regardless of the treatment, there is a larger microbial population, with a higher production of short-chain fatty acids and ammoniacal nitrogen production. In general, the mixture of essential oils was not able to significantly alter the studied microbial population, except for the increase of the populations Butyrivibrio fibrisolvens, Selenomonas ruminantium and protozoa. Thus, treatment with 400 mg MSOE / kg DM seems to be able to decrease the methane production of sheep due to the increase of propionate.