PSVI-1 - Effects of dietary nonforage fiber sources and starch levels on nutrition digestion and rumen fermentation of fattening Hu lambs

The primary objectives of this experiment were to study the effects of fiber sources [beet pulp (BP) vs. soybean hull (SH)] and dietary starch levels [low = 22%  dry matter (DM), medium = 25% DM, and high = 27% DM] on nutrition digestion, rumen parameters and rumen bacteria in fattening Hu lambs. A total of 360 Hu lambs were assigned a 2×3 factorial arrangements, including a 63-day experimental periods. Six diets were formulated to include two fiber sources and three starch levels, and the samples including feed, feces, rumen contents, and rumen fluids were collected in different experimental periods. Analysis of fiber sources and starch levels was performed using two‐way ANOVA by SPSS software version 17.0 (IBM, Armonk, NY, United States). The digestibility of neutral detergent fiber (NDF) declined in (P = 0.005) increasing starch contents. Increasing starch levels increased the concentrations of propionate (P = 0.002) and valerate (P = 0.001) and decreased the concentrations of acetate (P < 0.001) and the ratio of acetate/propionate (P = 0.005). At the genus level, increasing starch levels reduced the abundance of Butyrivibrio_2 (P = 0.020). Nevertheless, the ADF digestibility was greater (P < 0.01) in lambs fed SH than lambs fed BP. The concentrations of butyrate were higher (P = 0.005) while the rumen pH was less (P = 0.001) in lambs fed BP than those fed SH. Fiber sources influenced the abundance of Succiniclasticum, Candidatus_Saccharimonas, Ruminococcus_1 and Christensenellaceae_R-7, which were higher in lambs fed SH compared with those fed BP (P < 0.05). In summary, the interaction of fiber sources and starch levels had no differences on growth performance, and lambs fed SH increased final BW compared lambs fed BP. Fiber sources mainly changed the abundance of cellulolytic bacteria in the rumen community.