Co-occurrence of phytoestrogens, pyrrolizidine alkaloids and other plant secondary metabolites in rations of dairy cattle in Punjab, Pakistan

In this study 49 plant secondary metabolites such as phytoestrogens (PEs) and pyrrolizidine alkaloids (PAs) were determined in dairy total mixed rations (TMR) collected from dairy farms in Punjab, Pakistan. A validated multi-metabolite method based on liquid chromatography/tandem mass spectrometry (LC - MS/MS) was used to screen a range of plant-derived metabolites. Across 30 TMR samples, PEs and other bioactive compounds, including PAs, were found at mean levels of 42,300 +/- 25,400 and 340 +/- 249 mu g/kg dry matter, respectively, with 100% occurrence of PEs daidzein, genistein and glycitein, followed by biochanin A (96%), genistin (96%), daidzin (93%), glycitin (93%) and coumestrol (83%). All PEs, except biochanin A, coumestrol and ononin, positively correlated with proportions of corn grain, soybean meal, canola meal and molasses (p < 0.01). In conclusion, the widespread presence of PEs and PAs requires investigation of their effects in animals, to determine maximum levels in feed, considering animal and food safety perspectives.