Abstract
It has been hypothesized that the forage quality stay-green phenotypes of grain sorghum [Sorghum bicolor (L.) Moench] is greater than senescent cultivars. Quality evaluations included 0 h, 48 h and 7 d in situ digestions (ISDMD) and analysis of neutral and acid detergent fiber (NDF, ADF), soluble carbohydrates, and potential for prussic acid (HCN-p) and nitrate toxicity. The results of the quality analyses were compared to determine if all methods yielded comparable rankings of cultivars. Eight cultivars were tested during the 2000 growing season at Beeville and College Station, Texas. Included were a stay-green line, a senescent line, a leaf-disease resistant line, two hybrids (stay-green x disease resistant and senescent x disease resistant), a brown mid-rib variety (bmr), a low HCN-p line, and a commercial hybrid. Twelve cultivars were tested during the 2001 growing season at Corpus Christi and College Station, including a second stay-green line, three additional stay-green hybrids, and a second commercial hybrid (the low HCN-p line was not grown in 2001). The NDF, ADF, 48 h and 7 d ISDMD, soluble carbohydrates, grain and forage yields, and potential cyanide or nitrate toxicities were completed for leaf, stem, and axillary branches of plant residues. The 48 h and 7 d ISDMD of the stay-green line's leaf fraction in 2000 was significantly lower (P = .05) than the senescent line, while the NDF of the leaf and stem fractions of the stay-green lines in 2000 were significantly lower (P = .05) than all other cultivars except for the leaf-disease resistant line at Beeville. The NDF and ISDMD results for the stay-green lines were similarly during 2001. The bmr line had comparatively small ADF and large ISDMD during both years. There was no significant correlation between NDF/ADF, ISDMD at 48 h and 7 d, and soluble carbohydrate procedures due to the leaching of soluble carbohydrates during the 0-ISDMD used as a correction factor. None of the tested cultivars proved to be a genetic source for low HCN-p in axillary tillers.
Rhodes, Gregory Allen (2002). Forage quality of Sorghum crop residues after grain harvest. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -R504.