Detection of Hypoglycin A and MCPrG Metabolites in the Milk and Urine of Pasture Dairy Cows after Intake of Sycamore Seedlings

Hypoglycin A (HGA),methylenecyclopropylglycine (MCPrG),hypoglycinB (HGB), and & gamma;-glutamyl-& alpha;-(methylenecyclopropyl) glycine(& gamma;-glutamyl-MCPrG) are secondary plant metabolites occurringin sycamore maple (Acer pseudoplatanus) as well as several other Sapindaceae (e.g., Blighiasapida). By interfering with energy metabolism, theymay cause severe intoxication in humans and other species. However,to date, there is not enough data available concerning the intake,metabolism, or excretion of sycamore maple toxins in dairy cows. InMay 2022, five cows were observed over four days, when they had firstaccess to a pasture with two sycamore maples. Grazing of their seedlingsthat grew numerously in between the pasture plants was monitored bydirect observation. Milk samples were drawn both from individual cowsand from the bulk tank. Spontaneous urine samples were collected fromall cows on day 3 after access to the pasture. Seedlings (100 g) weresampled on the pasture and analyzed, together with milk and urinesamples, for sycamore toxins and their metabolites using liquid chromatography-tandemmass spectrometry and liquid chromatography-high-resolution mass spectrometry.Cows ingested sycamore seedlings while grazing. Values of HGA in milkwere below the limit of quantification. However, metabolites of HGAand MCPrG were detected in individual milk samples already at theend of the first day of grazing. Urine samples of all five cows showedhigher concentrations of conjugated HGA and MCPrG metabolites thanin milk. Observations suggest that dairy cows may have a low susceptibilitytoward sycamore maple toxins. However, whether this could be attributedto foregut fermenting species in general requires further elucidation.

Automated summary

This study observed the behavior of five dairy cows over four days when they first accessed a pasture with two sycamore maples. The results showed that the cows ingested sycamore seedlings while grazing. Metabolites of HGA and MCPrG were detected in individual milk samples on the first day of grazing, but HGA values in milk were below the limit of quantification. Higher concentrations of conjugated HGA and MCPrG metabolites were found in urine samples compared to milk. The study suggests that dairy cows may have a low susceptibility to sycamore maple toxins, but further research is needed to determine if this is due to foregut fermenting species in general.