Publication Database

Transfer of plant toxins from feed into milk – a challenge for future sustainable milk production Systems? (2024)

Art

Hochschulschrift

Autor

Engel, Anna Maria (WE 4)

Quelle

Berlin: Mensch und Buch Verlag, 2024 — viii, 147 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/44956

Kontakt

Institut für Tierernährung

Königin-Luise-Str. 49
14195 Berlin
+49 30 838 52256
tierernaehrung@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Climate change presents significant challenges for agriculture. The emission of greenhouse gases calls for a reassessment that influences the manufacture and processing of animal feed. Sustainable solutions, such as cultivating domestic grains as protein sources and adopting techniques like grazing livestock on grasslands and agroforestry, will gain importance. However, certain plants that are increasing in significance possess SPM. SPM serve various significant functions and have diverse effects on their surroundings. In addition to benefiting the plant and its environment, the primary motivation for producing these compounds is to provide a growth advantage and protection against herbivore predators, ensuring plant survival and reproduction. Nevertheless, ingestion of plants with SPM still occurs resulting in a possible risk to both animals and consumers if there is a transfer of SPM via feed into food of animal origin, especially into milk. For some SPM transfer into the milk is already investigated while for others there is still lack of data as summarized in Chapter I. Chapter I reviews the current literature on two secondary plant metabolites for which there is still a lack of data on their occurrence and possible transfer to milk, although there are indications that transfer may be possible. The QA are naturally occurring alkaloids in Fabaceae. Their best-known representative with a wide range of applications in animal nutrition, due to their beneficial protein content, are lupins, which are subdivided into sweet and bitter lupins depending on their QA content. QAs have multiple toxicological effects that result in a so-called anticholinergic syndrome causing among other coordination disorders, respiratory paralysis, tachyarrhythmia or cardiac arrest. Due to its chemical structure, a transfer into the milk of cows was suspected, but there are no data so far. Sapindaceae, a different botanical family, possesses recognized toxic properties. Within this family, certain SPM, namely HGA, MCPrG, and HGB, have led to significant toxic effects in humans, horses, and wild ruminants. Important representatives of the Sapindaceae are sycamore maple trees, which can be found in meadows and fields with contents on HGA, MCPrG and HGB in their seeds and seedlings. Initial studies suggest that these SPM may be transferred into the milk of mares or cows after ingestion of seeds or seedlings. Nonetheless, thorough research on the effects of these substances and their excretion in milk has not been conducted in dairy cows. Chapter II therefore explains the aims and hypothesis of the current thesis. The main part of this thesis consists of two published manuscripts summarized in Chapter III and IV. The primary objective was on increasing knowledge on the transfer QA into the milk of dairy cows as well as on the intake of maple toxins HGA, MCPrG and HGB and their subsequent Transfer into the milk of dairy cows. These efforts aimed to provide a more comprehensive assessment of the risks posed to both animals and consumers. Furthermore, a toxicokinetic model was derived to predict the feed to food transfer for QAs (published in Engel et al. 2022, Chapter III). The first study was conducted as a feeding trial in four Holstein-Friesian dairy cows. During the trial rapeseed meal was switched for either one or two kg of narrow-leafed lupins (L. angustifolius variety Boregine) for seven days as experimental periods with respective depuration periods. During these periods milk was sampled twice daily and analyzed on their respective QA content with an in-house validated novel LC/MS-MS method. Furthermore, milk ingredients were monitored regularly. Based on the data three-compartment toxicokinetic model was derived to predict feed to food transfer. The results reveal that an intake of 1’774 mg QA per cow per day had no effects on animal health. Thereby, the pattern of the used lupin was like those already reported for narrow-leafed lupins even though total QA content was in the upper range of reported QA contents. Already the administration of 1 kg of lupins resulted in a transfer of QA into milk with different transfer rates for all QAs. Administration of twice the number of lupins (2 kg) showed a significant dosedependent transfer of QA into milk. Calculation of individual transfer rates revealed transfer rates differing from 1.05% for isolupanine to 3.74% for multiflorine (Chapter III). With maximum QA contents in milk a preliminary risk assessment was made for high consumers (P95) indicating a potential risk for consumers in this scenario (Chapter III). Nevertheless, data on toxicokinetic and occurrence of QA in feed and food is lacking. Chapter IV aimed to investigate if there is an intake of sycamore seedlings by dairy cows while grazing and if so, if there is a transfer of their SPM into milk without the occurrence of clinical signs as known for other herbivores like horses after SPM ingestion. For that, five cows were subjected to an observational study over 4 days. Cows had access to a pasture with numerous seedlings growing between grass over a defined period. Additionally, they received a partial mixed ration in the barn ad libitum and concentrate feed suitable for their respective milk yields. Milk of individual cows was sampled twice daily as well as bulk tank milk of the whole herd (n=87) and analyzed on their content of HGA, MCPrG, HGB and their respective metabolites with a novel validated LC/MS-MS method. Experimental plots were placed on the pasture and seedlings were counted and photographed daily before cows were allowed to graze. Additionally, cows were observed by two independent observers and intake was captured if possible. Already on the first day, intake of sycamore maple seedlings was observed in dairy cows as a by-product of grazing. Noteworthily, only respective conjugated metabolites of HGA and MCPrG were measured in milk samples already on day 1 after grazing. Urine samples revealed MCPA-G contents above contents measured in diseased Peré David’s deer without the appearance of clinical symptoms. Statistical analysis revealed an increasing trend in MCPA-G contents in milk. There is still lack of data on toxicological effects of conjugated metabolites, but cows may be in general less susceptible to maple toxin intoxication. In conclusion, the present thesis highlights that a transfer of the investigated secondary plant metabolites into milk is possible. Current developments in relation to climate change call for a fundamental rethink of the agricultural sector. The significance of local forage and agroforestry methods is increasingly acknowledged. Further investigations are imperative to appraise the potential risk to consumers and to provide suggestions for farm management, feeding, and grazing practices. In the case of lupins, preliminary risk assessment revealed a possible Risk for certain consumer groups. However, the risk to the consumer can be further investigated and reduced by testing the lupins available on the market for their QA content, adapting the recommendations for use and carrying out additional toxicological studies. For SPM found in Sapindaceae including A. pseudoplatanus is remains uncertain whether the conjugated metabolites of HGA and MCPrG found in the milk of individual cows as well as bulk tank milk represent a potential risk to consumers. Nevertheless, both uptake by cows with apparently reduced susceptibility and the possibility of transfer were demonstrated which emphasizes the necessity to produce additional data. To promote sustainable agriculture, it is necessary to enhance the use of indigenous legumes like lupins and pasture farming. This progression necessitates a comprehensive analysis ofthe linked hazards. By establishing these potential threats, we can advance our knowledge of farming and agriculture and create positive environmental impacts that counteract climate change.