Inverkan av foders växtöstrogener på fysiologiska processer hos produktions- och sällskapsdjur

Phytoestrogens are secondary metabolites produced by plants. Among the plants that make phytoestrogens are soya, red clover and some types of grass. The name phytoestrogen is a collective term for compounds such as genistein, daidzein, biochanin A and formononetin. These compounds are similar to oestradiol-17β in their chemical structure. Because of this similarity, they can attach to the same binding site as regular oestradiol-17β. These binding sites are receptors called alpha (ERα) and beta (ERβ). Phytoestrogen can cause certain problems when sheep graze on phytoestrogen rich grass. Sheep can get reproductive disorders such as producing fewer lambs or difficulty getting pregnant. Phytoestrogen like formononetin can however have positive effects. If grass contains low concentration of formononetin, we can see a clear weight gain in lambs. The same problem emerges in cow, when they are fed on red clover. Their reproductive disorders however, are slightly weaker than in sheep. One problem that can occur in cows fed on clover is silent heat because phytoestrogens are inhibiting the heat in some cows. Another problem associated with phytoestrogens is that they occur in milk in the form of equol. Soy is widely used in pet food because it is inexpensive and it is a rich source of protein. One effect that has been observed is an increase in total and free thyroxin (T4).