Nutritional parameters of beef heifers fed diets with different roughages

The purpose of this study was to evaluate intake, digestibility and efficiency of microbial protein synthesis of beef heifers fed with sugarcane silage with different calcium oxide (CaO) levels (0, 7.5; 15 g/kg), fresh sugarcane and corn silage. The same concentrate was offered at 5 g/kg bodyweight (BW) for every diet. Five ruminally and abomasally fistulated beef heifers (373.8 +/- 33.12 kg BW) were used in a 5 x 5 Latin square design. Heifers fed sugarcane silage diets presented lower dry matter (DM) intake than those fed fresh sugarcane. Corn silage provides greatest DM intake compared with other roughages. CaO levels had a quadratic positive effect (P < 0.05) on DM and total digestible nutrients (TDN). For TDN intake (3.43 + 4.39 CaO - 2.56 CaO2) the maximum TDN intake of 5.31 kg/day was obtained at 8.6 g/kg CaO. The total apparent digestibility for neutral detergent fibre increased with CaO levels. An increase in nitrogen balance was observed with the inclusion of CaO in the sugarcane silage. Corn silages-based diets provide greater DM intake and digestibility and nitrogen balance compared with the diets based on sugarcane. Adding CaO to sugarcane as it is ensiled improves DM intake and TDN than diet sugarcane silage without CaO. However, the use of high levels of CaO (15 g/kg) in sugarcane at ensiling decreases the diet intake. Based on the maximum energy intake, the use of 8.6 g/kg CaO in sugarcane at ensiling is recommended.