Volatile Fatty Acids in Ruminal Fluid Can Be Used to Predict Methane Yield of Dairy Cows

Abstract

The dry matter intake (DMI) of forage-fed cattle can be used to predict their methane emissions. However, many cattle are fed concentrate-rich diets that decrease their methane yield. A range of equations predicting methane yield exist, but most use information that is generally unavailable when animals are fed in groups or grazing. The aim of this research was to develop equations based on proportions of ruminal volatile-fatty-acids to predict methane yield of dairy cows fed forage-dominant as well as concentrate-rich diets. Data were collated from seven experiments with a total of 24 treatments, from 215 cows. Forage in the diets ranged from 440 to 1000 g/kg. Methane was measured either by open-circuit respiration chambers or a sulfur hexafluoride (SF6) technique. In all experiments, ruminal fluid was collected via the mouth approximately four hours after the start of feeding. Seven prediction equations were tested. Methane yield (MY) was equally best predicted by the following equations: MY = 4.08 × (acetate/propionate) + 7.05; MY = 3.28 × (acetate + butyrate)/propionate + 7.6; MY = 316/propionate + 4.4. These equations were validated against independent published data from both dairy and beef cattle consuming a wide range of diets. A concordance of 0.62 suggests these equations may be applicable for predicting methane yield from all cattle and not just dairy cows, with root mean-square error of prediction of 3.0 g CH4/kg dry matter intake.

Genetic parameters for methane emission traits in Australian dairy cows

“…However, methane may be isolated from this problem because it is strongly related to the breakdown of feed and the digestive capabilities of the animal, rather than the focus of energy partitioning to a specific output. More recently, Williams et al (2019) showed that VFA proportions in ruminal fluid can be used to predict methane yield, and they suggested that their approach is among the cheapest methods for estimating methane yield of dairy cows. Thus, proxy methane phenotypes related to RMP may be able to be estimated.…”

Feeding Grazing Dairy Cows With Different Energy Sources on Recovery of Human-Edible Nutrients in Milk and Environmental Impact

“…Importantly, one limitation of our study is that we estimated methane production using volatile fatty acid stichometry rather than directly measuring it. Using volatile fatty acid stichometry to estimate methane production has been widely used in previous studies because of the strong relationship between rumen fermentation parameters and methane (Cabezas-Garcia et al, 2017;Williams et al, 2019;De Souza et al, 2020). It is important to recognize uncertainty and variability in methane across different methods (Hristov et al, 2018); however, the method used still is feasible to compare differences across treatments.…”

“…Two 50-mL samples of ruminal fluid were then preserved by the addition of 1.0 mL of 50% H 2 SO 4 and stored at −20 • C. Ruminal fluid samples were thawed at room temperature and centrifuged (15,000 × g, 4 • C, 30 min), and the supernatant was analyzed for volatile fatty acids by gas chromatography (Erwin et al, 1961) and ammoniacal nitrogen by the phenol-hypochlorite procedure (Chaney and Marbach, 1962). Methane was calculated using volatile fatty acid stoichiometry as previously reported (De Souza et al, 2020) according to the equations proposed by Williams et al (2019).…”

Measurement of Enteric Methane Emissions by the SF6 Technique Is Not Affected by Ambient Weather Conditions

“…However, due to the limited sampling times used in these latter methods [ 5 ], and the marked diurnal patterns in the magnitude of MeP from dairy cows [ 6 ], some researchers have questioned the suitability of these recent methods for quantifying daily MeP of individual cows [ 7 , 8 ]. Proxy methods for estimating daily MeP or MeY of individual animals are numerous, including predictions based on dry matter intake (DMI) [ 9 ], feed composition [ 10 ], methane to carbon dioxide ratio in breath [ 11 ], milk fatty acids [ 12 ], and volatile fatty acids in ruminal fluid [ 13 ]. However, proxy methods have generally had poor predictive accuracy and therefore have limited applicability in terms of predicting MeP from individual animals [ 14 ].…”