indicated a trend for a difference (P = 0.10) in milk fat concentration within 2 d for cows fed K carbonate sesquihydrate as compared with the control diet. By d 3, the difference in milk fat concentration between diets was significant (P < 0.05). Milk fat concentration of DCAD+ tended to be greater than the control group (P = 0.06) during the recovery period (period 3) with the cessation of K carbonate sesquihydrate supplementation. This may indicate that the effects of K carbonate sesquihydrate supplementation on milk fat may influence fat metabolism via the biohydrogena