Substitution of sugar cane with steam-treated eucalyptus (Eucalyptus grandis): effects on intake and growth rate of dairy heifers

Steam treatment has been considered a promising technology for upgrading fibrous materials for ruminant feeding. The aim of this study was to assess the effects of substitution of sugar cane with steam-treated eucalyptus (STE) chips (157°C, 140 min, 23 g H2SO4 kg−1 dry matter (DM) eucalyptus, without explosive decompression) on intake and growth rate of dairy heifers. The STE was washed with water to remove solubilized hemicellulosic sugars before it was used in the feeding trial. The control diet consisted of 55% sugar cane and 45% concentrate and the two other dietary treatments were obtained by substituting 35 and 70% of the sugar cane with STE residue. A split plot design experiment involving six Holstein heifers per treatment and three periods of 21 days each was used. Chemical composition of the ingredients, in vitro degradability of the roughages, animal intake and growth rate were measured. Extensive hemicellulose solubilization (> 90%) occurred during steam treatment and a significant increase of in vitro 48 h degradability (untreated eucalyptus 11.3%, STE residue 51.5%) suggested that steam treatment was effective in upgrading the ruminal degradation of eucalyptus. Increasing levels of dietary substitution of sugar cane with STE residue (i.e. 0, 35 and 70%) did not significantly affect (P>0.05) DM intake (9.7, 10.0, 9.4 kg) or growth rate (0.80, 0.68, 0.78 kg day−1).