Equação de predição do volume de gases através da pressão para ensaio in vitro no norte do Tocantins e implicações em diferentes altitudes.

Abstract

A prediction equation that establishes the relationship between pressure and gas volume can replace manual volume readings. This study serves to determine a prediction equation that correlates values of pressure and volume of gases for use in food evaluation by the semi-automatic in vitro gas production technique. The following was used with experimental diets 3 different ratio roughages: concentrate (100:0, 50:50 and 75:25) containing Mombaça grass silage and a commercial concentrate, and four levels of Propylene Glycol (PG) (0%, 2%, 4% and 6% of the volume of content to be incubated). A total of 1 g of each diet was incubated in 150 mL flasks with 90 mL culture medium, 10 mL ruminal inoculum, and the appropriate PG levels (two repetitions per diet). Gas pressure and volume readings were taken using a transducer. The data were used in the regression analysis, resulting in the estimation of gas volume from the pressure. The generated equation volume as a function of pressure presented curve with quadratic behavior was (V = –0.0195 + 3.7989P + 0.2174P2). The coefficient “b” of the second degree function multiplied by pressure (P) was 3.7989 at an altitude of 240 m. Local altitude influences the relationship between pressure and gas volume.