Context Utilising crop residues is an effective strategy to compensate for the shortage of common feed resources. Different processing methods can improve the nutritional value of these by-products. Aims This study aimed to investigate the effect of sodium hydroxide (NaOH, 50 g/kg dry matter (DM)), calcium oxide (CaO, 160 g/kg DM), hydrobromic acid (HBr, 60 mL/kg DM), and hydrogen peroxide (H2O2, 57 mL/kg DM) processing on the nutritional value of common bean (Phaseolus vulgaris) residues (CBR). Methods The chemical composition of the samples was determined using standard methods. In addition, a degradability trial was conducted using the nylon-bag technique. Furthermore, in vitro digestibility of the samples was determined by the batch-culture method. Moreover, the X-ray powder diffraction technique was used to calculate the crystallinity degree of the samples. Key results Chemical processing was effective on the chemical composition of the residues (P < 0.05). Treatments of CaO, H2O2, and NaOH increased the ash content. Chemicals reduced the neutral detergent fibre and acid detergent fibre. Other treatments, excluding CaO, increased total digestible nutrients, net energy for lactation, and net energy for gain. NaOH, H2O2 and HBr treatments increased the effective ruminal degradability of DM at ruminal outflow rates of 0.02, 0.05, and 0.08/h (P < 0.0001). Chemical processing caused a decrease in gas production (GP) and estimated parameters of CBR (P < 0.0001). The decrease in GP, short-chain fatty acids, metabolisable energy, and organic-matter digestibility in the NaOH and CaO treatments was more than in HBr and H2O2 treatments. After 24 h of incubation, all treatments except CaO increased the partitioning factor and decreased the gas yield (P < 0.0001). Furthermore, processing with NaOH and H2O2 increased the microbial biomass (P = 0.0128) and its efficiency (P < 0.0001) at the end of a 24 h incubation period. Moreover, different treatments reduced the crystallinity degree of CBR compared with the control. Notably, the lowest crystallinity percentage was observed in HBr-treated samples. Conclusions This study shows that chemical treatments (except for CaO) improve CBR nutritional value under in vitro and in situ conditions. Implications In vivo tests are required to validate the results.
