Effects of a Protein-Binding Additive and Brown Sorghum Bran Extract on In Vitro Rumen Fermentation, Intestinal Digestibility and Amino Acid Profiles of Protein Meals

Excessive protein degradation reduces protein-use efficiency in ruminants. This in vitro study evaluated brown-sorghum-bran extract (SBE; 20 or 40 g/kg DM), BioProtect (15 or 30 mL/kg DM), and tannic acid (30 g/kg DM; positive control) in soybean and canola meals. Gas production and ammonia-N were assessed over 24 h; protein digestion and amino acid concentrations were also determined. Gas production and ammonia-N were generally lower in treated meals, with responses dependent on substrate, additive and incubation time (p ≤ 0.003). Substrate × additive interactions affected RDP, RUP and IVIDP (p < 0.001). The higher inclusion rates, 40 g/kg DM SBE and 30 mL/kg DM BioProtect, did not differ from tannic acid in RDP, RUP or IVIDP within either substrate. After in vitro intestinal digestion, total EAA showed a substrate × additive interaction (p = 0.033); 30 mL/kg DM BioProtect and 40 g/kg DM SBE produced among the highest total EAA concentrations in both substrates. Among the individual acid-hydrolysable EAA recovered from the liquid fraction after in vitro intestinal digestion, only methionine concentration was affected by additive treatment (p < 0.001). Overall, 30 mL/kg DM BioProtect and 40 g/kg DM SBE produced the most consistent responses for RDP, RUP and IVIDP; however, total digested CP decreased slightly (p < 0.001), and amino-acid responses were variable. In vivo studies are required to determine effects on amino-acid supply and animal responses.