Epsilon Archive for Student Projects

Abstract

Methane (CH4) is a strong greenhouse gas (GHG) linked to climate change, and dairy farms are a key source of these emissions. Most studies look at enteric CH4 from digestion, but manure stored on farms also adds to the total emissions. Feed efficiency (FE) is the ability of an animal to convert feed into productive output (e.g., milk) and is commonly measured using residual feed intake (RFI), which is defined as the difference between an animal’s actual and its predicted feed intake based on maintenance and production requirements. More efficient animals are typically consuming less feed for a given level of production, although this relationship is not always consistent. Differences in FE and diet may influence the quantity and composition of excreted organic matter (OM), which can affect CH4 production during manure fermentation. This study looked at how FE and diet affect CH4 from dairy cow manure.
A total of 16 dairy cows were used in a 2×2 factorial design in a previous study, differing in FE classified as efficient (E) or inefficient (INE), and diets differed in forage-to-concentrate (F:C) ratio, with treatments of 55:45 (F55) and 70:30 (F70). Manure samples were collected from all cows and were incubated at 22 °C in the lab.
The results showed that CH4 production from manure was not significantly affected by FE or diet composition. Although manure from feed-efficient cows produced more total gas, CH4 production remained similar across treatments. Other fermentation parameters, including pH, dry matter (DM) disappearance, and volatile fatty acids (VFA), were also comparable among groups.
In conclusion, FE and diet composition did not affect CH4 production from dairy cow manure. In a related experiment conducted with the same animals, efficient cows produced less enteric CH4, whereas manure CH4 production remained unchanged across efficiency groups in the present study. These findings suggest that improving FE can reduce enteric CH4 emissions without increasing emissions from manure, indicating no trade-off between enteric and manure CH4 production.
These findings also suggest that changes in diet alone may not be sufficient to reduce CH4 emissions from manure. Instead, improving manure management practices may be an effective approach for reducing overall CH4 emissions from dairy production systems.