Performance of dairy cows fed forage and grain separately versus a total mixed ration.

Forty multiparous cows beyond peak production were fed forage ad libitum behind Calan doors and grain at 1 kg/2.5 kg milk through a computer controlled feeder, and 40 similar cows were fed a total mixed ration balanced for 32 kg milk behind Calan doors ad libitum. Based on mean milk production from d 16 through 21 of a preliminary period, cows were balanced into two groups within each group of 40 cows. Both groups received the originally assigned ration during d 22 through 49. During d 50 through 77, 20 cows were switched abruptly to the other ration and 20 remained on the original. Cows fed forage and grain separately had milk yields similar to those fed total mixed ration. Dry matter intake was lower for cows fed forage and grain separately from d 22 through 49 due to reduced forage intake and was also lower from d 50 through 77 due to decreased grain intake. Four percent fat-corrected milk production efficiency was higher for cows fed forage and grain separately. Abruptly changing cows from one feeding system to another did not influence milk yield, milk composition, or body weight gain. The computer controlled feeder system is an effective method to allot grain according to milk production requirements in freestall housing.