Metabolite Profiling in the Liver, Plasma and Milk of Dairy Cows Exposed to Tansy Ragwort (Senecio jacobae) Pyrrolizidine Alkaloids.

BACKGROUND: Plant-derived pyrrolizidine alkaloids (PAs) in feed cause metabolic disturbances in farm animals resulting in high economic losses worldwide. The molecular pathways affected by these PAs in cells and tissues are not yet fully understood. The objective of the study was to examine the dose-dependent effects of orally applied PAs derived from tansy ragwort in midlactation dairy cows. METHODS: Twenty Holstein dairy cows were treated with target exposures of 0, 0.47, 0.95 and 1.91 mg of total PA/kg of body weight/d in control, PA1, PA2 and PA3, respectively, for 28 days. Liver tissue biopsy and plasma and milk samples were taken at day 28 of treatment to assess changes in metabolic pathways. A targeted metabolomics approach was performed to detect the metabolite profiles in all compartments. RESULTS: The PA-affected metabolite profiling in liver tissue, plasma and milk revealed changes in three substrate classes: acylcarnitines (ACs), phosphatidylcholines (PCs) and sphingomyelins (SMs). In addition, in the plasma, amino acid concentrations were affected by PA exposure. CONCLUSIONS: PA exposure disturbed liver metabolism at many sites, especially devastating pathways related to energy metabolism and to amino acid utilization, most likely based on mitochondrial oxidative stress. The effects on the milk metabolite profile may have consequences for milk quality.

Assessment of information as regards the toxicity of T-2 and HT-2 toxin for ruminants.

In 2011, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks for animal health related to the presence of T-2 (T2) and HT-2 (HT2) toxin in food and feed. No observed adverse effect levels (NOAELs) and lowest observed adverse effect levels (LOAELs) were derived for different animal species. In ruminants a LOAEL was established for the sum of T2 and HT2 of 0.3 mg/kg body weight (bw) per day, based on studies with calves and lambs. The CONTAM Panel noted that the effects observed in nutritionally challenged heifers and ewes give rise to the assumption that rumen detoxification of T2 may not always be complete and therefore effective to prevent adverse effects in ruminants. However, the limited data on the effects of T2 on adult ruminants did not allow a conclusion. The European Commission requested EFSA to review the information regarding the toxicity of T2 and HT2 for ruminants and to revise, if necessary, the established Reference Point (RP). Adverse effect levels of 0.001 and 0.01 mg T2/kg bw per day for, respectively, sheep and cows, were derived from case studies, estimated to correspond to feed concentrations of 0.035 mg T2/kg for sheep and 0.6 mg T2/kg for cows. RPs for adverse animal health effects of 0.01 mg/kg feed for sheep and 0.2 mg/kg feed for cows were established. For goats, the RP for cows was selected, in the absence of data that they are more sensitive. Based on mean exposure estimates performed in the previous Opinion, the risk of adverse health effects of feeds containing T2 and HT2 was considered a concern for lactating sheep. For milking goats, a comparison performed between dietary exposure and the RP derived for cows, indicates a potential risk for adverse health effects. For dairy cows and fattening beef, the risk is considered low.

Assessment of information as regards the toxicity of fumonisins for pigs, poultry and horses.

In 2018, the EFSA Panel on Contaminants in the Food Chain (CONTAM) adopted a Scientific Opinion on the risks for animal health related to the presence of fumonisins, their modified forms and hidden forms in feed. A no observed adverse effect level (NOAEL) of 1 mg/kg feed was established for pigs. In poultry a NOAEL of 20 mg/kg feed and in horses a reference point for adverse animal health effect of 8.8 mg/kg feed was established, referred to as NOAEL. The European Commission (EC) requested EFSA to review the information regarding the toxicity of fumonisins for pigs, poultry and horses and to revise, if necessary, the established NOAELs. The EFSA CONTAM Panel considered that the term reference point (RP) for adverse animal health effects better reflects the uncertainties in the available studies. New evidence which had become available since the previous opinion allowed to revise an RP for adverse animal health effects for poultry from 20 mg/kg to 1 mg/kg feed (based on a LOAEL of 2.5 mg/kg feed for reduced intestinal crypt depth) and for horses from 8.8 to 1.0 mg/kg feed (based on case studies on equine leukoencephalomalacia (ELEM)). For pigs, the previously established NOAEL was confirmed as no further studies suitable for deriving an RP for adverse animal health effects could be identified. Based on exposure estimates performed in the previous opinion, the risk of adverse health effects of feeds containing FB1-3 was considered a concern for poultry, when taking into account the RP of 1 mg/kg feed for intestinal effects. For horses and other solipeds, the risk is considered low, although a large uncertainty associated with exposure was identified. The same conclusions apply to the sum of FB1-3 and their hidden forms.

Impacts of parturition and body condition score on glucose uptake capacity of bovine monocyte subsets.

The peripartal period of dairy cows is associated with a higher incidence of infectious diseases like mastitis or metritis, particularly in high-yielding animals. The onset of lactation induces a negative energy balance and a shift of glucose distribution toward the udder. Glucose is used as primary fuel by monocytes which give rise to macrophages, key cells in the defense against pathogens. The aim of this study was to analyze whether animals with high or low body condition score (BCS) differ in composition and glucose uptake capacities of bovine monocyte subsets. Blood samples were taken from 27 dairy cows starting 42 days before parturition until day 56 after parturition. The cows were allocated to two groups according to their BCS. A feeding regime was applied, in which the BCS high group received higher amounts of concentrate before parturition and concentrate feeding was more restricted in the BCS high group after parturition compared with the BCS low group, to promote postpartal lipolysis and enhance negative energy balance in the BCS high group. Blood cell counts of classical (cM), intermediate (intM) and nonclassical monocytes (ncM) were increased at day 7 after calving. In the BCS low group intM numbers were significantly higher compared to the BCS high group at day 7 after parturition. Within the BCS low group cows suffering from mastitis or metritis showed significantly higher numbers of cM, intM and ncM at day 7 after parturition. Classical monocytes and intM showed similar glucose uptake capacities while values for ncM were significantly lower. Compared with antepartal capacities and irrespective of BCS and postpartal mastitis or metritis, glucose uptake of all monocyte subsets decreased after parturition. In conclusion, whereas glucose uptake capacity of bovine monocyte subsets is altered by parturition, it is not linked to the energy supply of the animals or to postpartal infectious diseases.

Effects of deoxynivalenol (DON) and related compounds on bovine peripheral blood mononuclear cells (PBMC) in vitro and in vivo.

The Fusarium toxin deoxynivalenol (DON) often co-occurs along with the acetylated derivatives 3-acetyl-DON and 15-acetyl-DON in diets for ruminants. De-epoxy-DON is formed by rumen micro-organisms, while the acetylated DON derivatives might also undergo ruminal metabolism with de-epoxy-DON as an end product. However, despite the fact that de-epoxy-DON is the predominant substance finally absorbed, a complete degradation of the mother compounds can not be assumed for all feeding and metabolic situations of the cow, and thus raising the question of their possible post-absorptive effects. Hence, the aim of the study was to examine the effects of all four compounds on the concanavalin A stimulated proliferation of bovine peripheral blood mononuclear cells (PBMC) using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) as indicator in vitro and ex vivo. Among the DON-related compounds, DON and 15-acetyl-DON resulted in a similar IC50 (i.e. the concentration where the proliferation was inhibited by 50%) of 0.5 µM, whereas 3-acetyl-DON was less toxic (IC50 = 2.6 µM), while actually no IC50 could be estimated for de-epoxy-DON which was characterized by a maximum inhibition of approximately 24% at the highest tested in vitro concentration of 18.29 µM. For the in vivo experiment, 14 Holstein cows were used and fed either an uncontaminated control diet (CON) or a diet contaminated with Fusarium toxins, with DON being the predominating toxin for 18 weeks when blood was collected for PBMC isolation and subsequent proliferation/viability assay. The complete diets for the CON and FUS group contained 0.4 and 4.6 mg DON/kg DM, respectively, at that time. Exposure of dairy cows to the FUS diet resulted in maximum serum de-epoxy-DON levels of 52 ng/ml (0.19 µM), while levels of the unmetabolized DON reached maximum levels of 9 ng/ml (0.03 µM). The PBMC of these cows were slightly less viable, by approximately 18% (p = 0.057), while stimulation capability was not decreased at the same time. Although de-epoxy-DON was characterized by the lowest in vitro toxicity among the tested DON-related compounds, there appeared to be a lower viability of the PBMC isolated from cows fed the FUS diet, which had nearly exclusively de-epoxy DON in serum beside slight traces of unmetabolized DON. Thus, the factors responsible for these apparent discrepancies need to be clarified.