Effects of replacing finely ground corn with whey permeate on the performance of early- and mid-lactation dairy cows

Objective: Our objective was to evaluate the effects of substituting sugar from whey permeate for starch from finely ground corn fed to mid- or early-lactation cows on DMI and milk yield and composition. Materials and Methods: Two trials were conducted with 48 Holstein cows ill each. In Exp. 1,18 mid-lactation cows (116 +/- 18 DIM) were used in a 10-wk randomized block design. In Exp. 2, 18 early-lactation cows (37 2 DIM) were used in a 12-wk completely randomized design trial. In both experiments, cows were fed a basal diet during a 2-wk preliminary- period and then switched to 1 of 3 experimental diets. Whey permeate (WP) was substituted for finely ground corn to provide 0 (CONT), 3.1 (3WP), or 6.1% (6WP) supplement sugar in the rations. Prilled fat was added to maintain NE concentrations, and proportions of other ingredients were adjusted to maintain similar concentrations of dietary CP and NDF. Intake, milk yield and composition, BW, and BCS were monitored throughout the trial. Results and Discussion: The DMI tended to be greater for cows fed WP in Exp. 1, but no differences were observed in Exp. 2. No differences were observed in milk yield or concentration of components in either experiment. Yield of milk protein and solids-not-fat tended to be lower for cows fed diets containing WP compared with CONT. In Exp. 1, dairy efficiency (ECM/DMI) was lower for WP because of the tendency for greater DMI compared with CONT, but no differences in dairy efficiency were observed Exp. 2. No differences were observed in change of BW or BCS in either experiment. Implications and Applications: Results of these trials indicate that finely ground corn can be replaced by WP without affecting milk yield and component concentrations, or change in BW and BCS. However, diets containing 6WP tended to reduce yield of milk protein and lactose. Mid-lactation cows had lower dairy efficiency due to a tendency for greater MU, but DMI arid dairy efficiency of early-lactation cows was not affected.