Abstract: [Objective] To investigate the effects of ensiled rice straw on growth performance, economic benefits, fecal odor substances, and intestinal microecology of growing-finishing pigs. [Methods] Twelve Jinhua pigs were selected at each of three weight grades with initial body weights of （29.88±3.45） kg （L）, （48.58±6.51） kg （M）, and （63.08±5.22） kg （H）, respectively. Each grade was randomly divided into three treatments: positive control group, negative control group and experimental group, with 4 pigs per treatment and 1 pig per replicate. The positive control group was fed complete feed, the negative control group was fed 97% complete feed + 3% dry rice straw powder, and the experimental group was fed 95% complete feed + 5% ensiled rice straw powder. The pre-feeding period lasted 7 d. The formal experiment lasted 31 d for the L and M grades, and 60 d for the H grade. At the end of the experiment, growth performance indicators and fecal odor substances contents were determined, economic benefits were calculated and analyzed, and intestinal microecological structure was detected. [Results] ①During the 31-day experimental period, there were no significant differences in final body weight and average daily gain among all treatments in the L, M and H grades （P>0.05）; during the 60-day experimental period in the H grade, the difference in average daily gain among treatments tended to be significant （P=0.072）, and the average daily gain of the experimental group was 4.66% and 17.62% higher than that of the positive and negative control groups, respectively. ②Numerically, in the L grade, the weight gain cost of the experimental group was higher than those of the positive and negative control groups, and the weight gain benefit and profit were lower than those of the positive and negative control groups. In the M and H grades, the weight gain costs of the experimental group were lower than those of the positive and negative control groups, and the weight gain benefits and profits were higher than those of the positive and negative control groups. ③In the H grade, the difference in fecal ammonia nitrogen content among treatments tended to be significant （P=0.087）. The ammonia nitrogen content in the experimental group was 23.85% lower than that in the positive control group and 10.63% higher than that in the negative control group. ④At the phylum level, the abundance of Desulfobacterota in feces differed significantly among treatments in the H grade （P<0.05）; the abundance in the experimental group was close to that in the positive control group and 0.28% lower than that in the negative control group; the abundance of Fibrobacterota tended to differ significantly （P=0.097）; the abundance in the experimental group was close to that in the positive control group and 0.59% lower than that in the negative control group. At the genus level, the abundance of Limosilactobacillus differed extremely significantly among treatments （P<0.01）; the abundance in the experimental group was close to that in the positive control group and 3.60% higher than that in the negative control group; the abundances of Lactobacillus and p-251-o5 tended to differ significantly （P=0.077 and P=0.061, respectively）; the abundance of Lactobacillus in the experimental group was 5.95% and 9.39% higher than those in the positive and negative control groups, respectively, and the abundance of p-251-o5 was 2.78% and 10.09% lower than those in the positive and negative control groups, respectively. [Conclusion] In summary, dietary supplementation with 5% ensiled rice straw in medium- and high-weight Jinhua growing-finishing pigs exerts no negative effects on growth performance, can reduce production cost, improve economic benefits, decrease the emission of fecal odor substances, increase the abundance of beneficial intestinal microbiota in feces, and improve the composition of intestinal microorganisms.

Key words: ensiled rice straw, pigs, growth performance, economic benefits, fecal odor substances, intestinal microbiota