Milk production and composition, and methane emissions from dairy cows fed lucerne hay with forage brassica or chicory

摘要

Forage brassica and chicory crops provide an alternative to perennial grass pastures as a forage supply for grazing dairy cows during summer, but there is little information about their effects on milk production and methane (CH4) emissions. Thirty-two Holstein-Friesian cows were fed for 10 days on a diet of lucerne cubes (750 g/kg DM) and grain (250 g/kg DM) (CON) or diets in which forage brassica (410 g/kg DM, FBR) or reproductive-stage chicory (410 g/kg DM, RCH) were offered with lucerne cubes (340 g/kg DM) and grain (250 g/kg DM). Cows offered the FBR diet produced more energy-corrected milk (25.4 kg/day) than did cows offered the CON diet (22.7 kg/day, P=0.001), even though DM intake was not different for cows between the two groups (20.6 kg/day on average). In contrast, cows offered the RCH diet produced less energy-corrected milk (19.3 kg/day) than did cows in the other two groups (P=0.001), reflecting the lower DM intake by cows offered the RCH diet (17.7 kg/day, P < 0.01). Methane yield (g CH4/kg DMI) was lower (P < 0.01) on the CON (21.0) and FBR (20.5) diets than on the RCH diet (26.1). Methane intensity (g/kg energy-corrected milk) was different (P < 0.01) for all diets, with CON (19.4) being intermediate, FBR (17.3) lowest and RCH (23.8) the greatest. Diet type was associated with differences in the proportions of only a small number of specific milk fatty acids, and differences in proportions of specific fatty acids were not related to CH4 emissions.