In vitro prediction of methane production by lactating dairy cows

The aim of this thesis was to determine the relationship (if any) between in vivo CH4 production obtained using climate controlled respiration chambers and in vitro CH4 production using the gas production technique. The in vitro techniques are routinely used to evaluate the nutritional quality of feeds and feed ingredients as they have an advantage of being less expensive, less laborious and allow maintenance of more precise experimental conditions than in vivo studies. It is well known that gas in the gas production (GP) technique is produced after the fermentation of the substrate where CO2 and methane (CH4) are produced as direct gas, and indirect gas is produced from the buffering of short chain fatty acids (SCFA). Studies investigating the relationship between in vitro and in vivo CH4 production by cows fed the same feed as substrate used in in vitro incubations are rare in the literature. It is important to have an accurate prediction on CH4 production of rations to be fed in practice. Therefore, the Dutch government financed a large program to determine the actual CH4 emission from dairy cattle in vivo, using climate respiration chambers (CRCs). This offered the unique opportunity to conduct parallel in vitro experiments with the aim to derive accurate in vitro prediction equations for CH4 production. Such equations can subsequently be used in practice to reduce CH4 emission. In vivo CH4 production of dairy cows cannot be predicted by in vitro CH4 production using the automated batch culture gas production technique, even if the cows are adapted to the substrate under investigation, The main predictors of CH4 production by dairy cattle are related to diet composition (NDF, CP and OM), In vitro CH4 production varies based on whether donor cows are adapted to a respective ration or not although the differences observed in thesis were minor