Resumo

POSADA, Sandra L; NOGUERA, Ricardo  e  BOLIVAR, Diana. Relationship between pressure and volume for the implementation of the gas production technique, in vitro, in Medellín, Colombia.. Rev Colom Cienc Pecua [online]. 2006, vol.19, n.4, pp.407-414. ISSN 0120-0690.

The in vitro gas production technique is a method that allows the determination of the extent and kinetics of degradation of food as a function of the gas volume obtained during fermentation. Gas quantification can be done with the use of transducers measuring the pressure originated by the gas in fermentation flasks. The objective of this work was to establish a regression equation that relates gas pressure (P) and volume (V), for the implementation of in vitro gas production technique, according to the height over the sea level condition of our laboratory, in Medellín, Colombia. For this purpose, six different tupes of forage were inoculated with ruminal liquor and feces from Holstein cows. The pressure generated by the gas accumulated in the upper part of the incubation flasks was measured through a pressure transducer connected to a digital reader. Gas was extracted with a syringe until the pressure registered in the reader was zero. The equation was obtained using PROC REG of the SAS program: V = -0,1375+(5,1385*P)+(0,0777*P2), R² = 0,99. Establishing this equation is necessary because the Boyle and Gay-Lussac´s law doesn’t allow the estimation of the volume of gas diluted in the liquid phase. Similarly, the volume of gas accumulated in the upper part of the flasks varies as a function of the atmospheric pressure, therefore demanding the respective adjustment. The obtained equation is representative for ruminal liquor, feces and a wide range of forages with different fermentation potential. Thus, the equation was standardized for future research.

Palavras-chave : atmospheric pressure; fermentation; food evaluation.

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