Effect of feeding two types of concentrates in morning and evening meals and two types of fat supplement on diurnal patterns of plasma parameters in lactation dairy cows

The diurnal patterns of feed intake and TMR composition influence blood parameters in dairy cows; however, the effect of feeding TMR with different compositions in the morning and evening meals is not well characterized. In a completely random design, forty Holstein cows (110 ± 30 days postpartum) were randomly assigned to four treatment groups, with 10 cows per treatment. The treatments were as follows: a base diet containing 50 % cereal starch from barley grain and 50 % cereal starch from corn grain in the morning and evening meal + either prilled fatty acids supplement (EqP) or calcium salts of fatty acids supplement (EqCS); a base diet containing 25 % cereal starch from barley grain, 75 % cereal starch from corn grain in the morning meal, and 75 % cereal starch from barley grain and 25 % cereal starch from corn grain in the evening meal + either prilled fatty acids supplement (DiP) or calcium salts of fatty acids supplement (DiCS). Dry matter intake was affected by treatments (P ˂ 0.01). The highest intake was observed for EqP, EqCS, DiP,and DiCS. 3.5 % fat-corrected milk and milk fat percentage was significantly higher for EqP than other treatments (P ˂ 0.01), but other milk components were not significantly different among treatments (P ˃ 0.05). A significant difference was observed for glucose, cholesterol, TG, AST, and insulin concentration among treatments (P ˂ 0.01). The concentrations of all plasma parameters (glucose, cholesterol, TG, BUN, AST, insulin, and NEFA) significantly changed over 24-h period (P ˂ 0.01). Plasma concentrations of glucose, cholesterol, TG, BUN, AST, insulin, and NEFA displayed a treatment-by-time interaction (P ˂ 0.01). In general, changes in the cereal starch ratio (corn and barley) in TMR in each meal during a day affect the 24-h concentration of plasma parameters, but there was no strong evidence of leverage for cows’ metabolism.