Methane Production by two Breeds of Cattle in Tropical Conditions

This work aimed to measure methane emission by the most frequently used cattle for milk production in Brazil, Gyr and F1 Holstein x Gyr heifers feeding Tifton 85 (cynodont spp.) hay. Methane production was measured by a respirometric technique in six F1 Holstein x Gyr and six Gyr heifers fed Tifton 85 hay (Cynodon spp.) in a tie stall system consuming. After 21 adaptation days on feeding, heifers weighed 450kg and an apparent digestibility assay was performed. Feed intake and faecal production were measured for five days by total collection. Animals were housed for 24 hours in the respirometric chamber (open circuit type) receiving the experimental diet to quantify methane emission. Although dry matter (DM) intake was higher for crossbred heifers, nutrients digestibility was similar between breeds. Related to diet characteristics methane production was similar between genetic groups, with average values of 26.4 L methane/kg dry matter intake (L/kg DM), 43.2 L/kg digestible dry matter, 35.716 L/kg neutral detergent fiber, 57.3 L/kg digestible neutral detergent fiber, 29.5 L/kg organic matter and 45 L/kg digestible organic matter. Daily Methane production of crossbred heifers was higher than Gyr (173.76 versus136.77 L/d), due to higher DM intake of these animals. More productive animals may produce more methane per day because of the higher consumption of DM, so methane production data should be analyzed by relative and not absolute numbers.