| Phytoestrogens are the kind of bioactive substances which are structurally similar to animal oestrogen and have oestrogenic or antioestrogenic biological function. Phytoestrogens have positive or negative function in the animal. Certain phytoestrogens may improve animal growth performance and immunity. However if the animals graze overfull phytoestrogens, they would affect the reproductive system of the animals, ruminants would be particularly in the risk. So understanding kinds and content variation of phytoestrogen at the different growth stage is significant to the efficient use of pasture and phytoestrogens in animal production.Red clover (Trifolium pratense L.) and white clover (Trifolium repeus L.) are forage legumes with excellent quality, and they have been grown abroad in foreign and have great potential at home. In this experiment, an investigation on kind and concentration variation of phytoestrogens was carried out in red clover (cv: Great harvest and Canadian common) and white clover (cv: Haiha, Rivendel and Koala) followed their growth stage in a field trial.The results were as follows.Formononetin, genistein, biochanin A and daizdein were detected in leaves and stemsof red clover, but daizdein was not found in roots. Formononetin was a main phytoestrogenand the content was significantly higher than others (p<0.05 ) .Biochanin A Content inleaves was significantly higher than daizdein and genistein, but there was not significantdifference among them in stem.Phytoestrogens content changed differently in the cultivars and the organs at the vegetative stage. Formononetin content trended to increase in roots ( p<0.05 ) , and reduced in stems followed growing in Great harvest. The highest concentration was 5695.78μg/g on 10 April and then reduced to 3519.58μg/g later in leaves. In Canadian common, formononetin content gradually increased from 2724.98μg/g to 6026.65 μglg in leaves and changed greatly without rule in roots and stems. Genistein content declined in red clover stems with growth, but increased first and reduced later in roots and leaves. Maximal genistein content occurred on the middle April in roots and leaves of Great harvest, but on 10 April in roots and leaves of Canadian common. The maximal biochanin A contentoccurred on 24 April in roots and leaves, and on 10 April in stems of Great harvest, but on 7 May in stems and leaves, and on 10 April in roots of Canadian common. Dadzein content changed without rule.Phytoestrogen kinds had no difference between red clover cultivars, but phytoestrogen content was significantly different. Phytoestrogens content in Canadian common roots were higher than in Great harvest roots, and there was significant difference in total phytoestrogen content between roots of two cultivarsFormononetin, genistein and a little biochanin A were detected in white clover, and a little coumestrol occurred in its roots. Formononetin content was a main phytoestrogen and significantly higher than others (p<0.05 )Formononetin content in roots was higher than in stems and leaves of Haifa and Rivendel, but Koala was quite reverse. Genistein content in roots was lower than in stems and leaves.Genistein content was from 2.22 to 40.17μg/g in roots, stems and leaves of white clover, changed without rule before pre-blooming stage, and reached higher content in the early bloom stage and reduced later. Formononetin content changed from 24.50 to 536.73μg/g without rule with growth. Compared with Haifa and Koala, formononetin content changed widely in roots, stems and leaves of Rivendel; genistein content had no change and difference among the cultivars. Among the Cultivars, formononetin and total phytoestrogens content in Rivendel were higher than in Koala; formononetin content from 5.21 to28.28μg/g in Haiha was not different to Koala and Rivendel.The results showed that the phytoestrogens like formononetin in red clover and white clove had significant difference among organs and different growth stages and cultivars.
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