Stage of maturity (SM) and cutting time (CT) are important factors affecting the feedingvalue of alfalfa hay in ruminants. No data is currently available about the effects of includ-ing alfalfa hay cut at different CT and SM in total mixed rations (TMR) containing highlevels of concentrates on dairy cows performance. The objective of this study was to inves-tigate the effects of including 200 g/kg dry matter (DM) alfalfa hay cut at two CT (18:00 and06:00 h) and three SM (early bud, late bud and early flower) in a TMR with 650 g/kg DMconcentrates and 150 g/kg DM barley silage on dairy cows performance, diet digestibilityand feeding behavior. Eighteen cows were used in a cyclic change over design with six treat-ments (2 CT × 3 SM) in three 21 d periods. Leaf:stem ratio, crude protein (CP) and solublecarbohydrate (SC) concentration of alfalfa hay decreased with advancing maturity. Includ-ing alfalfa hay with advancing maturity in the TMR decreased CP intake (kg/d) and fecal N(g/100 g DM) concentration in dairy cows (P<0.05). Neutral detergent insoluble CP (NDICP)and acid detergent fiber (ADF) of alfalfa hay, mean particle size and physically effective fac-tor of TMR and eating behavior (min/kg DMI) of dairy cows increased with advancing alfalfahay maturity (P<0.05). Cutting alfalfa hay in the afternoon vs. morning increased leaf:stemratio, leaf content and SC concentration (P<0.05). Feeding TMR with afternoon cut alfalfahay to dairy cows increased apparent total tract digestibility of DM, organic matter (OM)and CP and serum total protein and decreased fecal nitrogen production (N; g/d), fecalN:milk N ratio (P<0.05) and tended to decrease fecal N concentration (g/100 g DM; P<0.10).At the early bud and early flower stage, afternoon cutting vs. morning cutting increasedDM, OM and CP digestibility, serum total protein and decreased fecal nitrogen production(g/d) in dairy cows. At the late bud stage, afternoon cutting vs. morning cutting improvedmilk lactose and total solid non-fat yield (SNF; kg/d; P<0.05). In general, alfalfa hay CT at different SM had more effect on nutrient digestibility and N metabolism than on animalproduction. In conclusion, stage of maturity of alfalfa hay included in TMR did not greatlyaffect dairy cow performance when it was included at a rate of 200 g/kg DM. The TMRs withalfalfa hay cut in the afternoon improved N efficiency in dairy cows.

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