Least-Cost Complete Rations for Dairy Cows

Two least-cost linear programmed computer formulated ration~ were compared to a conventionally fornmlated ration in a 20-week continuous trial. ]q'orty-eight cows averaging 57 days post-partum were randomly assigned to three treatments. Ration treatments were: 1) least-cost constant (LCC), fornmlated using the past year's prices; 2) least-cost variable (LCV), refornmlated biweekly with price changes: and 3) a conventionally formulated control (no urea). Corn silage, the sole forage, and grain were thoroughly mixed and bunk fed ad libitmn, ttations were desig'ned to be nutritionally comparable. LCC and LCV rations were programmed for a maxinmm of 1% urea (air-dry basis). LCV ration ingredients were changed abruptly at biweekly reformulations.