Stable isotope profile (C, N, O, S) of Irish raw milk: Baseline data for authentication

Grass-based milk production is a major contributor to Irish agricultural output. The study characterized the Irish milk pool using stable isotope ratio analysis of carbon, nitrogen, oxygen and sulphur. Authentic raw milk samples were collected from 50 farms on five occasions over 13 months. Mean values of -27.11, 6.79, -3.27 and 6.16 parts per thousand were obtained for delta C-13, delta N-15, delta O-18 and delta S-34, respectively. delta C-13 values reflected a high level of grass input and values increased with increasing cereal concentrate feed input (P < 0.001). delta O-18 values were most negative in spring. There was a significant interaction between feed and season for delta C-13 and delta N-15 values (P < 0.05), with the impact of concentrate feeding most evident in spring. delta S-34 values were lowest at the highest level of concentrate input (P < 0.05). The isotopic values reported here describe the Irish milk pool and may offer the potential to discriminate Irish milk and dairy products from similar commodities from other countries.

Automated summary

Grass-based milk production is a significant aspect of Irish agricultural output, with stable isotope ratio analysis used to characterize the Irish milk pool. The isotopic values obtained provide insights into the impact of grass inputs and concentrate feed inputs on the isotopic composition of Irish milk. Seasonal variations and interactions between feed types and seasons were observed, with potential implications for discriminating Irish milk and dairy products from those of other countries.