Isotopic composition of cow tail switch hair as an information archive of the animal environment

Abstract

Using isotopic signatures from animal tissue, it is possible to recover certain information about the environment of the animal - notably the diet - at the time the hair was laid down. In the case of tail switch hair of cattle, a single hair may often represent an archive of information spanning a year or more in time. Isotopic analysis by mass spectrometry is now becoming cheap enough to be considered accessible for routine diagnostic or scientific investigation. The ratios of 13carbon (C):12carbon and 15nitrogen (N):14nitrogen ar e ideal for such investig ation, since C and N are constituents of all animal proteins. This paper explains the theory of isotopic analysis in layman's terms, and repor ts an exper iment in which tail switch hair of 9 cattle from three Northland dairy farms was analysed in a 'proof of concept' study, to demonstrate the information-retrieval potential offered by isotopic analysis. Changes in isotopic abundance are measured in parts per thousand (, ‰). When matching signatures on replicate hairs, the average distance from the 'interpolation' line was ± 0.13‰ for 13C, and ± 0.11‰ for 15N. In contrast to this, differences in 13C between different hair segments analysed exceeded 11‰ , while between farm dif ferences in 15N exceeded 2.0‰ . We suggest possible reasons for these differences in isotopic signature. Keywords: 13C, 15 N, isotopic archive, nutritional ecology, stable isotope