Growth performance, nutrient digestibility, blood profile, gut health and La deposition of weaning rabbits fed with a low dosage of La2O3

The previous studies found that livestock supplemented with lanthanum (La) complex such as rare earth element-enriched yeast had better growth performance and gut microbiota, and it is assumed that these results may be mainly due to La3+. This study was conducted to evaluate whether La3+ could improve growth performance, nutrient digestibility, blood profile and gut health, also had no La deposition problem in weaning rabbits. La3+ was supplemented to the rabbit diet as La2O3 which dosage was low. A total of 216 weaning rabbits were randomly allotted into 3 treatments, with 6 replicates per treatment and 12 rabbits per replicate in a feeding trial. Treatments included: 1) basal diets (CON); 2) CON + 100 mg/kg of La2O3 (LA1); 3) CON + 200 mg/kg of La2O3 (LA2). Overall, gain-to-feed ratio was increased quadratically (P < 0.05) as increasing level of La2O3 in diets. At the end of the feeding trial, rabbits in the LA1 group had higher (quadratic, P < 0.05) duodenal villus height and calmodulin mRNA expression level in the duodenal epithelial cells respect to the other groups. No difference was found in La deposition in muscle between groups. Chyme samples were collected in the sacculus rotundus from CON, LA1, LA2 and diarrheal rabbits for analyzing gut microbial. Gut microbial in the LA1 group was associated with a higher (P < 0.05) alpha diversity by Shannon index compared to the CON and diarrheal rabbits. It was found that the count of g_Lactobacillus, g_Romboutsia, g_Alistipes and f_Ruminococcaceae was higher (P < 0.05) and the count of g_Escher ichia-Shigella was lower (P < 0.05) in no-diarrheal rabbits compared with diarrheal ones. Thus, weaning rabbits fed with a low dosage of La2O3 had better growth performance and gut health, and the deposition problem of La was not found in muscle, which relieved the weaning stress and could be a novel and functional additive in diets of weaning mammals.