The Effects of Composite Alkali-Stored Spent Substrate on Carcass Quality, Rumen Fermentation, and Rumen Microbial Diversity in Goats.

The objective of this study was to investigate the effects of composite alkali-stored spent substrate (SHMS) on carcass quality, rumen fermentation, and rumen microbial diversity in goats. Twenty-four 6-month-old Chuanzhong black goats with similar body weights (20 ± 5 kg) were selected and randomly divided into four groups ( = 6 per group) and received four treatments: 0% (control group, CG); 20% (low-addition group, LG); 30% (moderate-addition group, MG); and 40% (high-addition group, HG) of SHMS-replaced silage corn and oat hay. The experiment lasted for 74 days (including a 14 d adaptation period and a 60 d treatment period). The results of this study showed that MG and HG significantly improved the marble score of goat meat ( < 0.05). The flesh color score significantly increased in each group ( < 0.05). The fat color scores significantly increased in LG and MG ( < 0.05). There were no significant effects on the pH value or shear force of the longissimus dorsi in each group ( > 0.05). The cooking loss in MG was higher than that in CG ( < 0.05). The histidine and tyrosine contents in each group of muscles significantly increased ( < 0.05), with no significant effect on fatty acids ( > 0.05). The rumen pH of MG significantly decreased ( < 0.05), while the total volatile fatty acids (TVFAs) and ammoniacal nitrogen (NH-N) increased by 44.63% and 54.50%, respectively. The addition of the SHMS altered both the alpha and beta diversities of the rumen microbiota and significant differences in the composition and structure of the four microbial communities. The dominant bacterial phylum in each group were Firmicutes and Bacteroidetes, with as the dominant bacterial genus. Correlation analysis revealed that rumen bacteria are closely related to the animal carcass quality and rumen fermentation. In the PICRUSt prediction, 21 significantly different pathways were found, and the correlation network showed a positive correlation between the and 7 metabolic pathways, while the C5-branched dibasic acid metabolism was positively correlated with nine bacteria. In summary, feeding goats with an SHMS diet can improve the carcass quality, promote rumen fermentation, and alter the microbial structure. The research results can provide a scientific reference for the utilization of SHMS as feed in the goat industry.