The effects of beet pulp substitution for corn silage and barley grain on feed intake, milk production, chewing and sorting behaviors, ruminal fermentation, digestibility, and cost over income of feed were evaluated by using eight multiparous Holstein cows in a duplicated 4 × 4 Latin square design with 21-d periods. Cows were in mid-lactation (45.4 ± 3.6 kg/d milk production and 116 ± 10 days in milk) with an average body weight of 666 ± 10 Kg. Experimental diets consisted of 40% forage (corn silage and alfalfa hay) and 60% concentrate. Treatments were 0, 12, 18, and 24 % dietary dry matter of beet pulp that were substituted for an equal portions of barley grain and corn silage. Increasing beet pulp in the diet caused the proportion of the particles retained on the top sieve of the ( 19 mm), the second sieve (8-19 mm) and pan reduced linearly. While the proportion of the particles retained on the third sieve (1.18-8) increased linearly ( P 0.001). Increasing beet pulp in diet caused a linear increase in peNDF 1.18 ( P 0.002) and decrease in peNDF 8 ( P 0.001). Increasing beet pulp in the diet caused a linear increase in dry matter intake ( P = 0.01). Milk yield, 3.5% FCM, ECM, and the production of protein, lactose, and fat as well as the percentage of protein, lactose and fat were unaffected by the treatment. Increasing beet pulp in diet caused a linear decrease in feed efficiency (MY/DMI) ( P = 0.03). Rumen pH, propionate concentration and acetate to propionate ratio were not affected with the replacement. However, acetate ( P = 0.02) and butyrate ( P = 0.01) concentration increased linearly. Increasing beet pulp in diet caused a linear decreasing in rumen ammonia nitrogen ( P = 0.003). Also, increasing beet pulp in diet tended to linearly decrease milk urea nitrogen ( P = 0.06). Dry matter and organic matter digestibility were not affected by treatments. However, digestibility of dry matter and organic matters tended to increase linearly with increasing beet pulp. Increasing beet pulp caused a linearly decrease in chewing activity ( P = 0.007) but, eating activity was not affected by the diet ( P = 0.29). Increasing beet pulp led to reducing the price per kg of diet and in treatment with 24% beet pulp income was 7005 rials (per cow per day) more than control treatments. Given that the average of THI- index was equal to 70.5, cows were under heat stre increasing beet pulp caused a linearly decrease in respiration rate ( P = 0.009), which can indicatied reduction heat stress by increasing the beet pulp. Body weight, BCS and back fat thickness were not affected by treatments. The results indicated that under heat stress condition and in diets with high concentrate, beet pulp can be successfully substituted for barley grain and corn silage up to 24% of diet.