Studies on the influence of pyrrolizidine alkaloids (PA) on the health of dairy cows and on PA transfer to the milk

Abstract

The increasing spread of ragwort (Jacobaea vulgaris) poses a risk to livestock due to its toxic pyrrolizidine alkaloid (PA/PANO) content. These secondary plant metabolites can cause liver damage and may be transferred into milk. This study examined dose-dependent effects of PA/PANO exposure in dairy cows under controlled conditions. Twenty pluriparous German Holstein cows were divided to five groups: a water control, a molasses control, and three treatment groups receiving 0.47, 0.91, or 1.91 mg PA/PANO per kg body weight per day for 28 days. Clinical parameters and energy metabolism indicators remained unchanged, whereas liver enzymes (AST, GGT, GLDH) increased significantly the highest exposed group. Histological examination revealed immune cell infiltration, apoptotic hepatocytes, and enlarged hepatocyte nuclei. On average, 0.064% of ingested PA/PANO were transferred into milk, mainly as jacoline, jaconine, and jacobine.