Five multiparous Holstein cows averaging 525.91 kg BW and 85 days in milk were assigned in a 5 x 5 Latin square to evaluate the effects of corn silage replacement by sugarcane plus whole cottonseed. Cows were cannulated in the rumen and proximal duodenum and were fed a 50:50 concentrate:forage diet (DM basis). Treatments were defined by the replacement of corn silage by chopped sugarcane (whole plant) plus whole cottonseed in the following proportions: 100:0 (control); 75:25; 50:50; 25:75; 0:100 in the DM basis. Dry matter intake (DMI) of cows fed 100, 75, and 50% corn silage diets was higher (P 0.05) by treatment diets. Total digestibilities of crude protein in diets containing up to 50% of sugarcane were lower than in diets containing 75 or 100% of sugarcane. Ruminal ammonia concentration decreased (P<0.05) with sugarcane and whole cottonseed inclusion. Concentrations of acetic, propionic and butyric acids as well as total volatile fatty acids concentration were higher (P<0.05) with sugarcane inclusion up to 50% level. Corn silage can be replaced by sugar cane plus whole cottonseed up to 50% level of forage in the diet without negative effect on nutrient utilization by dairy cows producing up to 18 kg milk/day. KEY WORDS: Digestibility, NDF, volatile fatty acid.