The objective was to evaluate the structural, yield and nutritional characteristics of biomass sorghum BRS 716 managed in different row planting spacing and harvest age in a semiarid region of Brazil. Three row spacing (45, 70 and 90 cm; plots) and four maturity at harvest (70, 100, 130 and 160 days; subplots) were evaluated following a randomized block design in a 3 x 4 split plot arrangement, with eight blocks. The useful area was 3 x 15 m. Variation in soil fertility in the area was the blocking factor. There was interaction between row spacing and maturity at harvest (P < 0.05) on plant height (P = 0.01), dry matter yield (DMY; P < 0.01) and proportion of senescent material (P = 0.01). The DMY observed at the age of 160 days and spacing of 90 cm was 41.40% higher than the DMY at the same age and in spacings of 45 and 70 cm (mean of 21.45 t/ha). As the maturity at harvest increased, there was a reduction in the crude protein content (P < 0.01), potential degradability (P < 0.01) and effective degradability (P < 0.01) of dry matter, and the content of non-fiber carbohydrates (P < 0.01), total digestible nutrients (P < 0.01) and the readily soluble fraction (P < 0.01) of the dry matter increased. Considering the yield and nutritional characteristics of biomass sorghum BRS 716 managed in the semiarid region for silage production, the row spacing of 90 cm and the maturity at harvest of 160 days after planting are recommended.

This study addressed the different proportions of millet and sorghum silage biomass BRS 716 (BRS-716 silage) in the diet of crossbred heifers ½ to ¾ Holstein x Zebu on their nutrient intake, and digestibility, microbial protein synthesis, nitrogen balance, ingestive behavior, and growth performance. Five experimental diets with 0, 25/75, 50/50, 75/25, and 100% of BRS-716 silage in compared to millet silage were evaluated. The roughage: concentrate ratio in the total dry matter (DM) of the diets was 75:25. The diets were evaluated in ten heifers with an initial body weight of 264.95 ± 19.4 kg (± SEM), following the experimental design in two 5 x 5 Latin squares, simultaneously. The increase in the proportion of BRS-716 silage in the diet of crossbred dairy heifers did not change the dry matter intake (DMI), total digestible nutrients, indigestible neutral detergent fiber (iNDFI), and metabolizable energy. The means observed for DMI, and iNDFI were 7.85 kg/day, and 1.18 kg/day, respectively. For the excretion of purine derivatives, and microbial synthesis, there was no significant effect (P > 0.05), the mean microbial crude protein synthesis was 503.37 g/day. The different proportions of the BRS-716 silage, and millet silage did not change the final body weight (P = 0.89), weight gain (P = 0.08), feed efficiency (P = 0.50), and the body measurements of heifers (P > 0.05). The final body weight and average daily gain of heifers were 278.46 kg, and 0.795 kg/day, respectively. The millet silage, and BRS-716 silage in the diet of crossbred Holstein x Zebu heifers, used exclusively or combined in different proportions, allow dry matter intake, and nutrients, digestibility, nitrogen balance, microbial crude protein synthesis, ingestive behavior, and performance similar body.