Effect of Genotype and Microbial Inoculants on Quality, Fermentation, and In Vitro Digestibility of Barley at Early Dough Stage of Maturity

A 2 × 2 × 2 factorial experiment was conducted to study the individual and combined effects of barley variety (Tarım 92 and Bravo), homofermentative inoculant (HMF; Lactobacillus plantarum and Enterococcus faecium), and heterofermentative inoculant (HTF; Lactobacillus buchneri) on the fermentation characteristics, chemical composition, nutritive value indices, and in vitro digestibility of whole-crop barley silages which were harvested at the early dough stage. Forty-eight laboratory silos (six replicates per treatment) were ensiled for 120 days. Tarım 92 silage exhibited superior fermentation stability across all treatments, with pH ranging from 4.11 to 4.30, Flieg points of 102.94–115.47, and lower NH3-N concentrations (142.01–173.72 mg/kg TN (total nitrogen)), reflecting better protein preservation than Bravo silage. In contrast, the poorest fermentation outcome (pH 5.24; Flieg 47.06; NH3-N 307.48 mg/kg TN) was exhibited by the Bravo silage inoculated with only homofermentative inoculants. Significant three-way interaction effects were detected among barley variety, homofermentative inoculant, and heterofermentative inoculant (p < 0.05). The dual-inoculated Tarım 92 silage showed the optimum in vitro digestibility and nutritional value (TDN 77.14%; NEL 1.81 Mcal kg−1 DM; RFV 176.25; ADF 18.75%; IVOMD 65.72%; predicted DMI 3.06% BW), while higher amounts of butyric acid and NH3-N suggested that better nutritional value was not always accompanied by better protein preservation. The combined inoculation also yielded the best outcomes within Bravo treatments (RFV 144.00), whereas HTF inoculation alone reduced IVDMD and IVOMD below uninoculated controls. Overall, these results show that the response to microbial inoculation is genotype-dependent and a combination of homofermentative and heterofermentative inoculation for high-dry-matter barley varieties can enhance nutritive value and digestibility. However, fermentation quality indicators, particularly butyric acid and NH3-N, require consideration in the selection of technique.