Effects of forage-to-concentrate ratio in prepartum diet on the dry matter intake and milk yield of periparturient cows during hot weather.

摘要

Effects of prepartum diets on DM intake (DMI) around parturition and on milk production and composition in early lactation during a hot summer were investigated. 9 cattle due to calve in July or Aug. were assigned to 2 groups and fed either control (group C; 4 cattle) or high-concentrate (group H; 5 cattle) diets to meet 110% of their energy requirements from 18 days before their expected calving date to parturition. The proportion of concentrate in the control diet was 35%, and that in the high-concentrate diet was 45%. For 21 days after parturition, all cattle were fed the same diets for lactation ad libitum. The DMI of cattle in group H almost met their energy requirements. In group C, the DMI was decreased relative to group H and the concn. of plasma non-esterified fatty acids was significantly higher before parturition (P < 0.05). Therefore, the cattle in group C were thought to be energy deficient before parturition. After parturition, there were no significant differences in DMI between the 2 groups. The milk yield of cattle in group H tended to be higher than that of cattle in group C at 21 days after parturition. Milk protein yield was significantly higher in group H 21 days after parturition relative to group C (P < 0.05), but there were no significant differences in milk composition between the 2 groups.