Optimizing Soybean Protein Protection Through Roasting: Effects of Temperature and Heating Duration on <i>In Vitro</i> Fermentability and Digestibility

Abstract Soybean ( Glycine max L.) is a high-quality protein source for dairy cow rations but contains high levels of rumen degradable protein (RDP), necessitating protection. Producing protected protein through roasting has shown variable results, particularly in determining the optimal temperature and duration of heating. This study aimed to determine the optimal temperature and duration for protecting soybean protein using the roasting method, observed by in vitro fermentability and digestibility. A Randomized Block Design was employed with five treatments: unroasted soybeans (R1), soybeans roasted at 180°C for 30 min (R2), soybeans roasted at 180°C at 40 min (R3), soybeans roasted at 200°C 30 min (R4), soybeans roasted at 200°C at 40 min (R5), and four groups based on rumen sampling. Data were analyzed using analysis of variance (ANOVA) and, if significant (p&lt;0.05), followed by the Duncan test. The results showed that the roasting method decreased NH3, dry matter, and organic matter digestibility (DMD and OMD) (p&lt;0.01). However, this method significantly increased VFA production and the populations of protozoa and rumen bacteria (p&lt;0.01). The R4 was optimal for protecting soybean protein in the rumen, as indicated by a reduction in NH3 and an increase in total VFA without significantly decreasing DMD and OMD.