Least-Cost Complete Rations for Dairy Cows

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Abstract
Two least-cost linear programmed computer formulated rations were compared to a conventionally formulated ration in a 20-week continuous trial. Forty-eight cows averaging 57 days post-partum were randomly assigned to 3 treatments. Ration treatments were: 1) least-cost constant (LCC), formulated using the past year''s prices; 2) least-cost variable (LCV), reformulated 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 libitum. Rations were designed to be nutritionally comparable. LCC and LCV rations were programmed for a maximum of 1% urea (air-dry basis). LCV ration ingredients were changed abruptly at biweekly reformulations. Dry matter consumption per 100 kg body weight, actual milk, fat-corrected milk (FCM) production, milk fat and solids-not-fat (SNF) percentages, and body weight gains were not significantly affected by ration treatment. Abrupt ration changes did not under conditions at this research significantly (P< .05) affect animal performance. Daily feed costs were reduced significantly (P < .05) for the LCC and LCV rations, respectively, compared to the control. Analysis of opportunity costs indicated that the addition of urea accounted for about 60% of the cost reduction attributable to the least-cost rations.

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