Variation in carbohydrate and protein fractions, energy, digestibility and mineral concentrations in stover of sorghum cultivars

The nutritional attributes of stover from 11 sorghum cultivars (SP 18005A x 220-2,3,6,7; PC-5; GGUB44 x SSG-59-3; ICSV-700; CSV-17; NRF-526; FM-1; SPV-1616; PVK-809; UPMC-503; and HC-308), selected on the basis of their diverse genetic backgrounds and use, were evaluated to aid in selecting parents superior in protein concentration and digestibility for use in sorghum breeding programs. Samples of stovers were collected after grain harvesting and analyzed. The CP concentrations in different cultivars differed (3.7-6.7%; P< 0.05) as did NDF, ADF, cellulose and lignin concentrations (P< 0.05). Total carbohydrate, non-structural carbohydrate and structural carbohydrate concentrations differed (P< 0.05) amongst cultivars as did carbohydrate fractions (CA, CB1, CB2, CC; P< 0.05). Protein fractions (PB1, PB2, PB3 and PC) except PA differed (P< 0.05). Concentrations of stover protein fractions PA and PB3 were lower than PB1, PB2 and PC. Unavailable protein fraction PC was highest (P< 0.05) in stover of SPV-1616 (36.8% CP) and lowest in ICSV-700 (20.4% CP). Concentrations of gross energy (GE), digestible energy (DE), metabolizable energy (ME) and total digestible nutrients (TDN) varied (P< 0.05) and ICSV-700 had highest concentrations of DE, ME and TDN (2.60 kcal/g DM, 2.13 kcal/g DM and 59.0%, respectively). Energetic efficiency for maintenance (NEM), lactation (NEL) and growth (NEG) differed (P< 0.05) with ranges of 1.13.-1.42, 0.41.-0.70 and 0.95.-1.33 kcal/g DM, respectively. Values for estimated DM intake, estimated digestible DM and relative feed value for stovers also varied (P< 0.05) with ranges of 1.76.-2.19%, 55.3.-61.4% and 75.4.-104.1%, respectively. In vitro dry matter digestibility was highest (P< 0.05) for cultivars PVK-809 (55.7%) and ICSV-700 (54.3%). Macro-and micro-mineral concentrations also differed (P< 0.05) across cultivar stovers. The wide genetic variability for nutritional attributes in stovers of sorghum cultivars indicates significant potential for improvement of stover quality through sorghum improvement programs, but care needs to be taken that grain and stover yields do not suffer.