RESUMO
The aim of the study was to determine the ruminal degradability of dry matter (DM), daidzein, genistein, glycitein and total isoflavones in ground full-fat soybean (GFFS) and solvent-extracted soybean meal (SSBM) using the in sacco method. The experiment was carried out in three replications on ruminally cannulated sheep that were fed twice a day with a diet consisted of hay and supplemental mixture (6:4, DM basis). The nylon bags with 2 g feed samples ground to 2 mm were incubated in the rumen for 0, 2, 4, 8, 16 and 24 h. The effective degradability (ED) of DM, daidzein, genistein, glycitein and total isoflavones was calculated at outflow rate of 0.06 h. The ED of DM in GFFS was 77.8% and was higher than in SSBM being 71.8% (p < 0.001). The ED of daidzein (96.8%) and genistein (93.6%) was higher for SSBM compared with GFFS (93.9% and 92.8%, p < 0.001 and p = 0.003, respectively) while ED of glycitein was lower for SSBM than for GFFS (75.5 and 81.7%, respectively, p < 0.001). All isoflavones in the incubations were extensively degraded in the rumen, and regardless of dietary source, they were almost completely degraded after 16 h of incubation. Further, the disappearance patterns, that is the functions describing the time courses of the analyte disappearance, were assessed. The disappearance patterns of daidzein, genistein, glycitein and total isoflavones were similar and showed greater disappearance of mentioned isoflavones from SSBM compared to GFFS (p < 0.001 for daidzein, genistein and total isoflavones and p = 0.002 for glycitein). The study provides knowledge on the effect of processing on degradability of isoflavones in rumen that can be used to clarify the interrelationship between isoflavones and rumen microbiota.
