Abstract
Sections from cattle hair serve as an isotopic archive—they contain information on the cattle diet from different time periods. We tested the reliability of 13C signatures (δ13C) in cattle tail switch hair to retrospectively trace back the annual dietary proportion of maize of different production systems without having to sample and analyze the feed. Furthermore, we investigated if differences in dietary proportion of maize during summer and winter feeding can be detected in a single tail switch hair by sampling hair only once a year. We sampled hair and obtained information on management and annual composition of diets on 23 cattle farms in northern Germany. Farms differed in dietary proportions of maize, grass and concentrates as well as in grazing regime (year-round grazing, summer grazing, no grazing). We found that the annual mean δ13C values (δ13CY) of two hair sections that contain the isotopic information of summer and winter feeding is a robust indicator for the annual proportion of maize in cattle diet on a farm. The grazing regimes could clearly be distinguished by analyzing seasonal mean δ13C values (δ13CS). We could also demonstrate short term changes in the diet changes by means of δ13CS. We conclude that the method can be used in different cattle production systems to check on dietary proportions of maize for a period of one year before sampling of hair.
Highlights
In dairy cows there seems to be an on-going trend to increasing milk yields which require higher energy contents in the diet that are often provided by silage maize and concentrates
The δ13CY values in cattle tail switch hair of each farm were highly correlated with the annual dietary proportion of maize (Table 3)
The dietary proportions of grass and concentrates were correlated with δ13CY in cattle hair because the dietary proportions of maize, grass and concentrates were highly intercorrelated (Table 3)
Summary
In dairy cows there seems to be an on-going trend to increasing milk yields which require higher energy contents in the diet that are often provided by silage maize and concentrates. Maize is comparably easy to cultivate at reasonable costs and the area that is cultivated with maize for dairy production in Germany has increased during the last half century [1, 2]. Maize is often cultivated in intensive cattle production systems with N surpluses resulting in a potential risk for larger N emissions compared to grassland-based forage production [3]. Pasture-based systems are regarded as more friendly for the environment, as promoting animal-welfare, and are thought.
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