Metabolism of isoflavones and effect on reproductive performance of sows fed red clover ( Trifolium pratense )

The use of red clover (Trifolium pratense) silage in sow diets may improve welfare and feed resource efficiency, but its high phytoestrogen (PE) content raises concern about reproductive effects. This study examined isoflavone metabolism and reproductive performance in 22 Yorkshire sows fed either red clover silage (RCS; 17.1 g PE kg−¹ DM) or white clover silage (WCS; 0.7 g PE kg−¹ DM) over two reproductive cycles. Concentrations of formononetin, biochanin A, daidzein, genistein, and equol were analysed in faeces, urine and blood plasma. Sows fed RCS showed higher total PE and equol levels, indicating efficient microbial conversion and systemic exposure. No adverse impacts on reproduction traits, reproduction organs, farrowing performance or litter characteristics were observed. These findings demonstrate that sows may tolerate PE from red clover silage without negative reproductive effects and support knowledge on inclusion of forage silage in sow diets.