The animal article of the month for May is “Effect of altering ruminal pH by dietary buffer supplementation on methane emissions from sheep fed forage rape” by Sun et al.

Enteric methane from farmed ruminants accounts for approximately one-fifth of agricultural emissions globally. Understanding how different feeds influence the production of methane from ruminants is important because feeding management is one of the pillars of animal husbandry. In many temperate countries, grazed forages are the main type of feed eaten by ruminants. Our previous studies have demonstrated that feeding forage rape (a member of the Brassica genus) results in lower methane emissions from ruminants, compared to ryegrass-based pastures.

The mechanisms mediating these low emissions when feeding forage rape are still unclear. In our earlier studies, we found that sheep fed forage rape had, among other rumen features, lower ruminal pH values than sheep fed a ryegrass pasture. We hypothesised that this low pH is a key factor contributing to the difference in methane emitted when forage rape and ryegrass are digested. To test this hypothesis, we manipulated the ruminal pH in sheep fed forage rape, by supplementing the diet with sodium carbonate, an alkaline substance, which would abolish the methane-depressing effects of low pH.

In our study, adding 5% of sodium carbonate in the diet of sheep did not immediately affect the methane yield (i.e., methane emitted per unit of forage eaten). However, after one week, the yield of methane increased by about a third. Methane yield measured from sheep continued to be greater (by 40%) when sodium carbonate was supplemented at 8% of the diet. When sodium carbonate was removed from the diet, the methane yield difference quickly disappeared. Our study is unique as it instigated a change in pH without resorting to a change in diet, and therefore it provides direct evidence that ruminal pH influences methane emissions. Our study suggests that feeding practices that reduce the mean ruminal pH levels, such as concentrate supplementation or feeding high sugar containing diets, could result in less methane emitted and help our environment. Because rumen pH is important for animal health and welfare, more research is required to develop feeding systems that meet both the environmental and animal welfare goals of livestock production.

The animal article of the month for May “Effect of altering ruminal pH by dietary buffer supplementation on methane emissions from sheep fed forage rape”  is available Open Access.

Authors: X. Z. Sun, R. Harland and D. Pacheco

The animal Article of the Month is selected by the Editor-in-Chief and is freely available for one month. View the recent selections