| Sixteen Holstein dairy cows were blocked into groups of 4 averaging 610.9 +/- 29.4 kg body weight, a parity of 3 +/- 0.44 and 50.7 +/- 8.4 days in milk. Within blocks, cows were allocated randomly to 4 treatments: intensively or extensively managed pasture with either a grain-based supplement or one with sugar replacing 19 % (w/w, DM basis) of the grain. Supplement was fed at the rate of one kg 4 kg-1 milk up to 8kg cow -1 d-1. Rumen fluid was sampled from one cannulated cow per group before, 1 and 2 h following the evening supplementation. Five days of breath sampling ensued for determination of methane emission using the S hexafluoride (SF6) method. Four percent fat-corrected milk (FCM) production averaged 33.5 kg d-1 and was not affected by treatment. Sugar did not affect rumen fluid pH and concentration of even-chain fatty acids. Methane production was not statistically different among treatments (p <0.05), averaging 9.4 g L-1 FCM. In conclusion, increasing intensity of clipping and harrowing pasture and feeding sugar at 18 % of concentrate DM may not mitigate methane production of grazing dairy cattle. |
