Effects of Compound Microecological Preparation Supplementation on Production Performance and Nutrient Apparent Digestibility in Hu Sheep from the Rumen Perspective

This study evaluates the effects of a compound microecological preparation named ATABG, which is composed of antimicrobial peptide ID13 and <i>Saccharomyces boulardii</i>, on Hu sheep's growth performance, feed digestibility, and rumen parameters. A total of 40 three-month-old Hu sheep (21.65 ± 0.33 kg) were randomly assigned to two groups: the control group (Con), which received a basal diet, and the experimental group (ATABG), which received the same diet supplemented with 1 g/kg ATABG on a dry matter basis. After a 10-day pre-feeding period to adapt the animals to the experimental diet, dry matter intake and weight gain were recorded during the subsequent 63-day trial period. Body weight was measured on days 1, 21, 42, and 63 of the trial, and animals were slaughtered on day 63 to collect rumen fluid and tissue. Results indicated that ATABG supplementation significantly increased the apparent digestibility of crude protein, neutral detergent fiber, acid detergent fiber, and organic matter (<i>p</i> < 0.05). Rumen fluid analysis revealed increased microbial protein concentration and cellulase activity (<i>p</i> < 0.05) in the ATABG group. Microbiota analysis indicated that ATABG increased the relative abundance of <i>Ruminococcus</i> and Proteobacteria, elevated Firmicutes, and reduced Bacteroidota (<i>p</i> < 0.05). Correlation analysis showed <i>Ruminococcus</i> was positively associated with crude protein digestibility, while <i>Quinella</i> correlated with growth-related indices (r > 0.4, <i>p</i> < 0.05). In conclusion, ATABG supplementation improves protein digestibility and rumen microbial protein synthesis by enriching <i>Ruminococcus</i> and enhancing cellulase activity, potentially optimizing nitrogen utilization in Hu sheep.