Enteric methane emission from grazing dairy cows receiving corn silage or ground corn supplementation

This study assessed the effects of corn silage or ground corn supplementation on CH4 emission, milk production and total dry matter (DM) intake by dairy cows under lenient grazing conditions. Twelve Holstein x Jersey dairy cows were divided into 6 homogeneous groups and randomly distributed among the experimental treatments, which were compared using a replicated 3 x 3 Latin square design over three periods of 17 days (evaluation period of 5 days). The dairy cows strip-grazed a mixture of annual ryegrass (Lolium multifiorwn) and oat (Avena saliva) grass. The treatments consisted of three feeding strategies: one without supplementation (the WS strategy), one supplemented with ground corn (the GC strategy; 3.2 kg as DM basis), and one supplemented with corn silage (the CS strategy; 4.2 kg as DM basis). The post-grazing sward height (average = 8.8 cm) was held constant between treatments by reducing the herbage allowance (HA) in the supplemented treatments. The HA values were 41.3, 30.8 and 34.6 kg of DM/cow/day for the WS, CS, and GC treatments, respectively. Daily enteric CH4 emission was measured using the sulfur hexafluoride (SF6) tracer gas technique. The CH4 yield (g/kg of DM intake) decreased in the GC treatment group compared to the WS and CS treatments, although the CH4 emission (g/day) and CH4 intensity (g/kg of milk) did not differ between treatments, averaging 337 g/day and 15.1 g/kg milk, respectively. The total DM intake increased by 2.9 kg/day, and milk production increased by 1.4 kg/day in the GC treatment group compared to the WS group, whereas the total DM intake increased by 1.5 kg/day, and milk production did not differ between the CS and WS treatment groups. In conclusion, it was possible to reduce the HA and maintain or increase the total DM intake with corn silage or ground corn supplementation, respectively. In dairy cows grazing temperate grass under lenient grazing conditions, corn silage and ground corn supplementation were effective for reducing CH4 yield but not CH4 intensity.