The article presents experimental data on the effect of nickel citrate obtained using nanotechnology on the biochemical parameters of cows’ blood. The animals were divided into 3 groups. Group I was the control one. The animals of the II and III experimental groups received a feed additive of nickel citrate in the amount of 0.1 and 0.3 mg/kg of dry matter of the diet daily during the ninth month of lactation and the first two months after calving. It was found that the addition of both doses of nickel citrate to the transition cows diet contributed to positive changes in some biochemical parameters. A decrease in the content of lipid hydroperoxides, TBA-active products, as well as phenolic compounds was revealed. It should be noted that supplementation cows with nickel citrate in the first month after calving led to a significant increase in the content of lipid hydroperoxides by 15.1% in the third experimental group (P<0.01) against decrease in the level of TBARS by 14.8% compared with the control group (P<0.05). Feeding cows of nickel citrate in the amount of 0.1 mg/kg of dry matter stimulated the binding of free phenols and increased the concentration of their conjugated compounds, particularly phenolglucuronides, in the blood of animals of experimental group II by 20.2% (P<0.05). Instead, the use of nickel citrate in the amount of 0.3 mg/kg of dry matter contributed to a more pronounced activation of detoxification function with increasing concentrations of phenolsulfates and phenolglucuronides in the blood of animals of experimental group III compared with animals of control group by 23.1 and 21.2% (P<0.05).