Effects of Ophiopogon japonicus By-Products as a Replacement for Alfalfa Meal on Production Performance and Intestinal Health in Meat Rabbits

Ophiopogon japonicus (O. japonicus) by-products contain abundant nutrients and bioactive substances. In this study, we evaluated their effects on production performance and intestinal health in meat rabbits. Firstly, we measured the nutrient levels of O. japonicus by-products along with its digestibility in meat rabbits. Then, we replaced dietary alfalfa meal with O. japonicus by-products to evaluate its effects on growth performance, carcass traits, apparent digestibility, and intestinal immunity in meat rabbits. The results showed that the effects of O. japonicus by-products on growing meat rabbits varied over time. In the early phase (days 1–21), it significantly depressed average daily gain (ADG, p < 0.001) and average daily feed intake (ADFI, p < 0.001), and increased feed to gain ratio (F:G) (p < 0.001). However, in the later phase (days 22–35), a compensatory response emerged, with significantly increased ADG (p < 0.001) and reduced ADFI (p < 0.01) and F:G (p < 0.001). Despite this compensatory growth, the growth performance and feed efficiency for the entire experimental period were not improved. O. japonicus by-products decreased carcass weight significantly (p < 0.001), but did not significantly affect dressing percentage and meat traits (p > 0.05), while it significantly reduced the digestibility of crude protein (CP, p < 0.05), increased that of crude fiber (CF, p < 0.001), and reduced the activities of amylase (p < 0.01) and increased trypsin in cecal contents (p < 0.05). Additionally, O. japonicus by-products elevated the levels of secretory immunoglobulin A (sIgA) and interleukin-10 (IL-10) in ileal mucosa (p < 0.05). They did not significantly affect the cecal microbial community or short chain fatty acid (SCFA) levels (p > 0.05). Our research indicated that O. japonicus by-products possess a balanced nutritional composition and improve intestinal immunity in rabbit production, making them a viable feed ingredient to partially replace alfalfa meal.