Öz
In recent years, use of plant bioactive compounds such as saponins in animal nutrition has been of increasing interest, particularly in Europe because of the EU ban on use of growth promoting antibiotics, including ionophores, in livestock production. The purpose of this research was to evaluate the effects of Yucca schidigera powder (YS), containing steroidal saponins, supplementation to diets of lactating dairy cows on oxidant-antioxidant balance in the blood and, concentrations of urea nitrogen and malondialdehyde in milk. In the study, 10 Holstein cows in the mid lactation, with an average milk yield of 20.7 kg (±3.1 kg)/day and a live weight of 552 kg (±30 kg), were used. The blood and milk samples were taken from all animals fed the same diet at 2 h after feeding. After that, YS was added at the rate of 1500 mg/kg DM to the concentrate mixture of the same animals. All animals were fed the concentrate mixture with YS for 15 days and the blood and milk samples were taken at 15th d of feeding with YS and 2 h after feeding. The concentrations of malondialdehyde (MDA), reduced glutathione (GSH), vitamin A, β-carotene, ammonium nitrogen and antioxidant activity (AOA), superoxide dismutase (SOD) and catalase (CAT) activities were determined in the blood. The levels of MDA and urea nitrogen, and milk quality parameters were measured in the milk. In statistical analysis, paired t-test method was used in SPSS computer program to compare the levels between before feeding with YS and after feeding with YS in the same animals. The concentrations of MDA and ammonium nitrogen were lower (p< 0.05), the levels of GSH and β-carotene were higher (p< 0.05) after feeding with YS than that before feeding with YS in the blood of cows. In the milk of cows, the concentrations of MDA and urea nitrogen were lower (p< 0.05) and the rate of fat % was higher (p< 0.05) after feeding with YS than that before feeding with YS. Those results are the first results showing that the YS decreased the lipid peroxidation and urea nitrogen concentration in the milk of dairy cows. The results indicate that YS may have a potential for use as a natural antioxidant source in dairy cow nutrition and contribute to the protection of their health.