Effects of Long-Term Dietary Inclusion of Citrus Pomace on Growth Performance, Intestinal Morphology, Digestive Enzyme Activity, Antioxidant Status, and Colonic Microbiota in Tibetan Pigs

This study aimed to evaluate the impacts of dietary inclusion of citrus pomace on growth performance, intestinal morphology, digestive enzyme activity, antioxidant status, and colonic microbiota in Tibetan pigs in a 90-day feeding trial. Eighty Tibetan pigs (75-day-age, 16.62 ± 1.50 kg) were divided into four dietary treatment groups, each containing four replicates with five pigs per replicate. The experimental diets comprised a control diet alongside three diets incorporating 5%, 10%, or 15% citrus pomace, respectively. The results showed that the feed conversion ratio of pigs was lower in the 5% citrus pomace group compared to the other three treatment groups. Compared to the control group, dietary inclusion of 5% citrus pomace increased villus height in the duodenum and jejunum of pigs. Additionally, it elevated β-amylase activity in the duodenum while increasing sucrase activity in the jejunum. Furthermore, dietary inclusion of 5% citrus pomace enhanced lipase activity in the duodenum, jejunum, and ileum of pigs compared to the control group. It also significantly increased catalase activity in the serum of pigs. However, dietary inclusion of 5% citrus pomace decreased the abundances of <i>Lactobacillaceae</i> and <i>Lactobacillus</i> while increasing the abundances of <i>Streptococcaceae</i>, <i>Turicibacteraceae</i>, <i>Streptococcus</i>, and <i>Turicibacter</i> in the colonic digesta of pigs. Collectively, long-term dietary inclusion with 5% citrus pomace reduced the feed conversion ratio, improved intestinal morphology, enhanced digestive enzyme activity in the small intestine, and elevated serum antioxidant status, while exerting complex effects on colonic microbiota in Tibetan pigs. Future research should prioritize in vitro fermentation to develop fermented citrus pomace as a feed ingredient for pigs.