Oxygen and Hydrogen Isotope Composition of Silage Water
2014
Sun, Luanzi | Auerswald, Karl | Schaufele, Rudi | Schnyder, Hans
Silage is an important dietary water source that influences the oxygen and hydrogen isotopic composition of domestic herbivores and their products. Silage sampled fresh from the silo had 18O- and 2H-depleted tissue water when compared with fresh pasture grass sampled around midday during the silage-making seasons. During exposure in the feed bunk, silage water became increasingly enriched in 18O and 2H. When δ18O was plotted against δ2H, the slope of the regression was less during daytime than during night-time. Exposure to 18O- and 2H-enriched or -depleted water vapor inside sealed glass containers led to strong changes in the isotope composition of silage water. The results resembled predictions from the Craig–Gordon isotope model of evaporation. The atmospheric conditions during exposure (relative humidity, exposure time, and isotopic composition of the air vapor) in the feed bunk thus strongly affect the isotopic composition of silage water ingested by domestic herbivores.
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