Detection of dietary changes by intra-tooth carbon and nitrogen isotopic analysis: An experimental study of dentine collagen of cattle (Bos taurus)

Hypsodont teeth potentially contain a record of dietary or environmental changes occurring during their growth. The aim of our study is to understand how a dietary change is recorded in dentine collagen. Analyses were conducted on five steers (Bos taurus) raised in an experimental farm. From birth until weaning the steers were fed on a C₃ diet; after weaning they were fattened on a C₄/C₃ mixed diet until slaughter. Dentine collagen was sampled on demineralized molars from top to bottom. The change from the C₃ to the C₄/C₃ diet and weaning are both reflected in intra-tooth variations in δ¹³C and δ¹⁵N values, respectively. The abrupt change in carbon isotopic composition of the diet is reflected by a progressive change of the dentine collagen δ¹³C values. The gradual change may reflect sampling strategy and/or gradual turnover of the metabolic nutrient pool. The weaning process is reflected by a decrease in δ¹⁵N that exactly coincides with increase in δ¹³C. This demonstrates that when steers are weaned to a protein-poor diet, δ¹⁵N traces the cessation of suckling. Archaeological applications of this study are considered, including determination of the duration of lactation in prehistoric herds, and detection of residential mobility in cattle herders.