Effects of red clover isoflavone on lactation performance, milk quality and nitrogen metabolism in dairy cows.

Reducing nitrogen loss and improving nitrogen utilization efficiency in dairy cows can reduce economic costs and mitigate the environmental impact of nitrogen emissions. Red clover isoflavone, a natural compound derived from plant extract, has the advantage of biological safety. This study aimed to investigate the effects of red clover isoflavone on lactation performance and nitrogen metabolism in dairy cows. Sixty-eight Holstein cows (165 ± 21 d in milk, 710 ± 75 kg initial body weight, 2.30 ± 1.21 parities, 33.93 ± 3.81 kg/d milk yield) were chosen in a randomized complete block design. Cows were divided into 5 blocks by milk yield and randomly assigned to 4 treatments (17 cows per treatment). The experimental period lasted 84 d, during which cows were fed a basal diet supplemented with red clover extract (RCE) at 0, 2, 4, or 8 g/kg of total mixed rations (TMR) on a dry matter (DM) basis. These levels corresponded to red clover isoflavones of 0, 0.46 (0.31 g/kg formononetin and 0.15 g/kg biochanin A), 0.93 (0.67 g/kg formononetin and 0.26 g/kg biochanin A), and 1.83 g/kg (1.32 g/kg formononetin and 0.52 g/kg biochanin A), respectively. With increasing supplementation of RCE in TMR, milk yield increased quadratically by 4.65% to 9.64% (