栄養・飼養Ⅰ

[II-20-17] Plasma concentrations of methionine, homocysteine, cysteine, and vitamin B₆ in lactating cows in winter and summer

*Suttida Prombood¹, Taketo Obitsu¹, Toshihisa Sugino¹, Yuzou Kurokawa¹, Thanutchaporn Kumrungsee¹ (1. Hiroshima Univ.)

[Introduction] This study compared plasma concentrations of methionine (Met), homocysteine (Hcys), cysteine (Cys), and vitamin B₆ in lactating cows obtained from two experiments conducted in winter and summer to clarify their Met and vitamin B₆ status. [Methods] Two experiments were conducted with lactating cows in early winter (Nov; n=29) and summer (Aug; n=18) in a free stall barn equipped with a robotic milking. Cows were given a concentrate diet at milking and partial mixed rations (TDN: winter; 69%, summer; 73%) in both experiments. Milk production and dry matter intake (DMI) were recorded for one week, and tail blood was collected at 4h after initial feeding on a day during the observation period. [Results] Averages of milk production and DMI did not differ between two experiments. In summer, the concentration of plasma Hcys and Cys showed negative correlations with milk yield, whereas these trends were not observed in winter. Plasma Met and pyridoxal-5'-phosphate concentrations had no relationship with milk yield in both seasons. In summer, the utilization of Cys may increase in high-yielding cows, which would be supported by sufficient vitamin B₆ status.