Respirometria e determinação das exigências de energia e produção de metano de fêmeas bovinas leiteiras de diferentes genótipos

Abstract

Standart procedures were estimated in order to calibrate a respirometric chamber for large animals at Metabolism and Calorimetry Laboratory of Veterinary Scholl of Federal University of Minas Gerais, Brazil. Correction factors were calculated for oxigen, carbon dioxide and methane gases, and values were 1.0001; 0.8972 and 1.0755. The nutricional requirements of net energy for maintenance (NEm) of Gir, Holstein and crossbred F1 Holstein-Gir heifers fed tropical grass hay using respirometric technique were determined. The concentration of injected gases (carbon nitrogen, methane and carbon dioxide) was compared to the analysed values. NEm for F1 and Holstein animals were similar (102.3 Kcal/LW0.75). These value was lower for Gir heifers, that had 85.2 Kcal/LW0.75 NEm. Metane production was similar between heifers, 33.7L/kg dry matter intake and 41.9L/kf neutral detergent fiber intake.