This study evaluated the response of dairy heifers fed corn based silage with 1.3 kg/day of concentrated in comparison with three sugar cane-based diets corrected with 1% of urea + ammonium sulphate (9:1) (urea), with 1.3; 2.0 and 2.7 kg/day of concentrate. A total of 20 heifers were used (12 Holstein breed and 8 Brown Swiss breed heifers) in a randomised block design, with 5 blocks formed on the basis of initial live weight and breed. The consumption of dry matter, organic matter and neutral detergent fiber did not differ between corn-silage based diet and sugar-cane based diet. Higher consumption of ether extract was found when diet based on corn silage was supplied in comparison to those based on sugar cane. Intakes of total carbohydrate and non-fibrous carbohydrates differed between corn silage diet and those based on sugarcane (1.3 and 2.0 kg concentrate). Total digestible nutrient intake observed with supply of the diet based on corn silage was lower than that obtained with sugar cane (2 kg concentrate). Diets had a significant effect on coefficients of digestibility of crude protein, ether extract, total carbohidrates and neutral detergent fiber. There was no significant difference on total weight gain neither on average daily gain between the corn-silage based diet and the sugar-cane diet with 2.7 kg of concentrate in relation to the sugar-cane diets. Ruminal pH did not differ at collection times among experimental diets. The lowest concentration of N-NH3 was observed in animals fed corn silage-based diet 3 hours after feeding compared to the sugar cane-based treatments. A milk production system with heifers calving at 24 months and fed a diet containing moderate to high concentrate levels (± 45:55, forage:concentrate), sugar cane forage added with 1% of a mixture of urea + ammonium sulfate (9:1, urea:ammonium sulphate) can be a substitute for corn silage.
dairy heifers; ruminal pH; urea
