The objetives of this research were to detect how many days were necessary to animals adapt to the diets, by measuring intake; to evaluate the effect of crescent levels of wheat middlings as a replacement for corn meal in the diets on the milk production and composition, the intake and apparent digestibilities of dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), ether extract (EE), total carbohydrates (TC), crude protein (CP), intake of total digestible nutrient (TDN) and non fiber carbohydrate (NFC), as well as diets economical evaluation. Twelve Holstein cows were allotted to four balanced 4 x 4 Latin square design in accordance with the lactation period. The four experimental diets were formulated to contain 70% corn silage and 30% of concentrate. Crescent levels of wheat middlings were used in the concentrate (0, 33, 67 e 100%) as a replacement for corn meal, for the treatment 1, 2, 3 and 4, respectively. All diets were isoproteics, with aproximately 15% CP. Five days was enough for adaptation of the animals to the rations. There was linear increase in the intake of NDF, expressed as kg/day and %LW and linear decrease in the intake of NFC, however there was no change in the intake of DM, OM, CP, EE, TC and TDN. The total apparent digestibilities of DM, OM, TC and CP presented a linear decrease response, with increasing levels of wheat middlings in the diets. However, the total apparent digestibilities of EE and NDF did not change. The milk production corrected or not for 3.5% fat and milk protein, fat, milk dry matter and deffated milk contents were not influenced by the wheat middlings levels in diets.
corn silage; corn meal; lactating cows; total mix ration
