Red clover isoflavonoids in feed, plasma and milk of ruminants
Year: 2015
Type: dissertation
Abstract: Forage legumes such as red clover (Trifolium pratense L.) are used due to their ability to fix atmospheric nitrogen. Red clover has a high crude protein content and sufficient digestible fibre. Red clover silage tends to increase dry matter intake and milk yield in dairy cows. The use of clover silage can lead to desirable changes in milk fatty acid composition, promote growth and increase live-weight gain in ewes and lambs. The literature review focuses on the principal isoflavones in red clover, their metabolism in the rumen and conjugation and excretion. The role of equol is reviewed regarding concentrations in plasma and milk. Red clover varieties studied contained isoflavones; formononetin (6.0–7.9 mg/g in dry matter (DM)), biochanin-A (3.7–6.1 mg/g in DM), genistein (0.5-0.6 mg/g in DM) and daidzein (0.2–0.30 mg/g in DM). There were significant differences in isoflavone contents. The isoflavone content was highest in cultivar Ilte, which had the highest concentration of formononetin. The effect of growing conditions (year), growth stage (harvest) and habitat (site) were significant for formononetin concentrations. The total isoflavone and formononetin concentrations were highest under poor weather conditions, at the northern location and with later harvest. In the feeding experiment, the ewes were fed red clover (RC) silage that contained on average 6.8 mg/g of formononetin in DM. Timothy/meadow fescue (Phleum pratense L./Festuca pratensis Huds.) grass silage did not contain any isoflavones. In the RC group, estimated daily intake of isoflavones was 10.5 g formononetin. The major part of formononetin ingested was metabolized, contributing to the increase of equol in the serum (average level of 7.7 mg/l). In HPLC analyses, the serum of ewes contained solely (S)-equol. The ewes of RC group gained weight faster (P<0.001) and were significantly heavier (P<0.01) at the end of the experiment. All ewes became pregnant. There were no significant differences in the time of conception, numbers or weight of foetuses or numbers of ovulations. The mass of the uterus was significantly greater (P<0.01) in the RC group compared with that in the control group. This difference was mainly explained by the increase of foetal fluids in the RC group (P<0.01). In the dairy cow feeding experiment, the RC silages contained 3.0–6.5 mg/g formononetin in DM. Grass silage did not contain any isoflavones. The formononetin contents of the red clover were highest for the shortest growthperiod. The daily intake per cow of daidzein was 1.7–2.6 g and of formononetin 27–76 g. The equol concentration in plasma was 4.6–8.4 mg/l. Intake of formononetin was strongly associated with the equol concentration in plasma (R2 0.71). Equol contents in plasma were significantly higher (P<0.01) for the RC than for the cows fed grass silage. Plasma equol contents were significantly higher (P<0.001) for fed silages, where the growth period were shortest. Equol concentrations in the milk of cows fed RC were 458–643 µg/l and daily secretion of equol in milk was estimated to be 12–19 mg/day. Intake of formononetin was only weakly associated with equol concentration in milk (R2 0.20). Equol concentrations were also analysed from organic and conventionally produced commercial milk samples. Organic skimmed milk contained 411 µg/l of equol and conventionally produced 62 µg/l. The HPLC method provided excellent accuracy and sensitivity for quantification of isoflavonoids from fodder, blood, and milk samples. (S)-equol was the main isoflavonoid detected. It is suggested that the estrogenic effects of metabolic equol in sheep reported earlier are solely or predominantly due to (S)-equol. In Finnish landrace sheep, the fecundity of ewes was not reduced by feeding RC. The volume of foetal fluids, however, increased, which could increase the risk of vaginal prolapse before term. A strong association between formononetin intake and equol concentration in plasma was demonstrated. The equol content in cow’s milk can be as high as 600 µg/l with RC silage feeding, even though only a small part of the formononetin is secreted into milk as the metabolite equol. Milk equol is derived from the formononetin of RC silage and RC-fed cows’ milk can be considered as a source of equol in human nutrition.
Source: Työväentutkimus Vuosikirja
Author: Eeva Mustonen
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2189502038