Metabolic adaptation to energetic demands of early lactation in Holstein Friesian and Simmental cows.

Holstein Friesian (HF) is the highest-performing dairy breed worldwide. However, this breed is prone to suffer from health disorders and infertility due to metabolic instability. The aim of the study was to use the metabolic differences between to breed, German HF and German Simmental (SI), for discussion of the biological impact of well-known and novel pathways and their respective indicators. Therefore, a targeted metabolomics approach combined with an examination of classical clinical chemistry using plasma samples was used to describe the metabolic status 42 days before expected calving and at day 21 of lactation. In total, 27 multiparous cows (HF n = 17, SI n = 10) were enrolled in the study. All cows were kept on the same farm under identical management, feeding and housing conditions. BW of HF cows dropped while SI cows maintained their BW but produced less milk than HF cows during the first weeks of lactation. Differences were detected for the following indicators and related pathways, and were used to assess their biological impact. Branched-chain amino acids such as leucine and isoleucine at day +21 remained as high as at day -42 in HF cows; however, in SI cows, a clear drop in these amino acids was observed indicating less body protein mobilisation in this breed. Alpha amino-adipic acid and kynurenine as markers for oxidative stress balance were increased at day +21 in HF cows, only reflecting a metabolically more tensed condition in HF cows. As a conclusion, these findings confirm the impact of these metabolites on a higher risk to suffer from metabolic disorders.