In vitro rumen degradation, fermentation, and methane production of five bakery by-products

Utilising bakery by-products ( BBPs ) in ruminant diets could promote circularity and waste management. This study aimed to investigate the effect of different BBPs, specifically wholemeal crumbed bread ( WMB ), white crumbed bread ( WB ), plain cracker feed ( CF ), flavoured cracker feed ( FCF ), and biscuit meal ( BM ), on rumen degradability, fermentation characteristics, and methane ( CH 4 ) emissions by employing a 72-h in vitro gas production system. The basal substrate consisted of dried, ground grass silage, wheat, and dried corn distillers’ grains, while the BBPs mainly and partially replaced wheat grain, and in the case of WMB, WB, FCF, and BM soyabean meal as well. Fermentation kinetics were determined by fitting gas and CH 4 production curves to nonlinear models. In vitro dry matter degradability ( IVDMD ) was lower ( P = 0.007) in WMB and FCF compared with CON. Propionate concentration was higher ( P < 0.001) in WMB, WB, CF, and BM than in CON, whereas valerate concentration was higher ( P = 0.004) in WMB and WB compared with the other treatments. The acetate:propionate and (acetate+butyrate)/propionate ratios were greater ( P < 0.001) in CON than in WMB, WB, CF, and BM. Total gas production kinetics also differed, with the fractional rate constant being higher ( P < 0.001) in WB and BM compared with CON, and the half-life being longer ( P < 0.001) in CON than in the BB P s treatments. The partitioning factor was highest in CON and lowest in CF ( P < 0.05). The asymptotic CH 4 production was higher in CON than in WB, FCF, and BM. In terms of fermentation kinetics, the fractional rate constant of CH 4 production was higher in WB than in CON and WMB, while the half-life of fermentation of the degradable fraction of each substrate was longer in CON than in WB, CF, FCF, and BM. However, the CH 4 yield expressed per unit of DM degraded did not differ significantly among treatments ( P > 0.05). The inclusion of WMB and BM, although resulting in lower IVDMD, was associated with higher propionate concentrations, indicating a shift in fermentation pattern. Despite no effect on cumulative CH 4 yield, WB and FCF altered fermentation kinetics, indicating differences in modelled CH 4 production patterns rather than in total CH 4 yield.