Carry-over of pyrrolizidine alkaloids from feed to milk in dairy cows

Abstract

Pyrrolizidine alkaloids are toxins present in many plants belonging to the families of Asteraceae, Boraginaceae and Fabaceae. Particularly notorious are pyrrolizidine alkaloids present in ragwort species (Senecio), which are held responsible for hepatic disease in horses and cows and may lead to the death of the affected animals. In addition, these compounds may be transferred to edible products of animal origin and as such be a threat for the health of consumers. To investigate the possible transfer of pyrrolizidine alkaloids from contaminated feed to milk, cows were put on a ration for 3 weeks with increasing amounts (50-200 g day(-1)) of dried ragwort. Milk was collected and sampled twice a day; faeces and urine twice a week. For milk, a dose-related appearance of pyrrolizidine alkaloids was found. Jacoline was the major component in milk despite being a minor component in the ragwort material. Practically no N-oxides were observed in milk, notwithstanding the fact that they constituted over 80% of the pyrrolizidine alkaloids in ragwort. The overall carry-over of the pyrrolizidine alkaloids was estimated to be only around 0.1%, but for jacoline 4%. Notwithstanding the low overall carry-over, this may be relevant for consumer health considering the genotoxic and carcinogenic properties demonstrated for some of these compounds. Analysis of the faeces and urine samples indicated that substantial metabolism of pyrrolizidine alkaloids is taking place. The toxicity and potential transfer of metabolites to milk is unknown and remains to be investigated.

Occurrence of pyrrolizidine alkaloids in animal- and plant-derived food: results of a survey across Europe

“…But contrary to the putative causative plants, where a ratio between free base and N-oxide form is always observed, only PAs in the free-base form were found and no N-oxides were detected. This is in accordance with the PA transfer study conducted by Hoogenboom et al (2011), who attributed this to the role of the rumen in digesting the plant material, whereby the N-oxides are degraded or converted to free bases. Interestingly, in this transfer study it was reported that for three of the PAs detected in this survey (jacoline, senkirkine, and otosenine) the carryover rate was relatively high (Hoogenboom et al 2011).…”

“…This is in accordance with the PA transfer study conducted by Hoogenboom et al (2011), who attributed this to the role of the rumen in digesting the plant material, whereby the N-oxides are degraded or converted to free bases. Interestingly, in this transfer study it was reported that for three of the PAs detected in this survey (jacoline, senkirkine, and otosenine) the carryover rate was relatively high (Hoogenboom et al 2011). The relatively high incidence of PAs present in milk (around 6%) may appear surprising, but a similar rate of 5-10% positive samples has been found in two follow-up surveys on milk, sampled in Germany and in the Netherlands (unpublished data).…”

“…For animal-derived food, no large-scale investigations have been published; but PAs have been detected during carryover studies in milk (Dickinson et al 1976;Hoogenboom et al 2011) and eggs (Edgar and Smith 2000;Diaz et al 2014;Mulder et al 2016b). Previous carryover studies with ragwort in cows revealed a dose-related appearance of PA in milk and the overall carryover of PAs was estimated to bẽ 0.1%, but for specific compounds up to 4% (Dickinson et al 1976;Hoogenboom et al 2011).…”

“…Previous carryover studies with ragwort in cows revealed a dose-related appearance of PA in milk and the overall carryover of PAs was estimated to bẽ 0.1%, but for specific compounds up to 4% (Dickinson et al 1976;Hoogenboom et al 2011). As bees also forage on plants containing these alkaloids, consequently, these compounds have been frequently detected in honey (Beales et al 2004;Boppre et al 2005;Kempf et al 2010;Dübecke et al 2011;EFSA 2011, Griffin et al 2015, Bodi et al 2014.…”

Hepatic Lipodystrophy in Galloway Calves

“…In contrast to reports of studies showing a transplacental transfer of PAs, 9,10,42 1 experimental study failed to detect abnormalities in fetuses after feeding a lethal dose to the respective dams. 20 While excretion of PAs into the milk could be detected, 17,28 no consensus of its effects after ingestion by the respective newborn and suckling animals exists. Dickinson and colleagues 6 could not detect any histological alterations of the liver or increased concentration of liverspecific parameters in newborn calves after feeding a nonlethal dose of PAs to the respective dams.…”