in which, Yijklm is the dependent variable, µ is the average experimental value, Cowi is the random effect of cow, Treatmentj is the fixed effect of treatment j (j = CL or HS), Timek is the fixed effect of time k (k = number of day or week), (Treatment × Time)jk represents the effect of the interaction between treatment and time, Eijkl is the sampling error and eijklm is the error term.
Time (day or week) was modeled as a repeated measurement by using a first-order autoregressive covariance structure which was determined by the lowest Bayesian information criterion. When the interaction between treatment and time was significant (P ≤ 0.05), pair-wise comparisons of the individual means were performed using the Tukey–Kramer test. Differences between treatments were declared significant at P ≤ 0.05 and differences from P > 0.05 to P ≤ 0.10 were considered as trends.