The authors point out that grass-fed cattle have an extra energy requirement for grazing activity, and that cattle fed on pasture grow more slowly – and have a lower weight at slaughter – than animals fed corn. "Each day added to the finishing period adds an extra daily maintenance cost, which must be accounted for in the environmental impact of the final product" they wrote. In addition, they claim that animals raised on pasture-based diets produce more ruminal acetic acid, and therefore more methane. Full Article at DairyReporter