Abstract: This work aimed to evaluate the effect of lyophilized cells of Lactobacillus paracasei KL1, a strain with good fermentation performance and bile salt hydrolase activity isolated from Tibetan kefir, on lipid peroxidation in laying hens. A total of 120 laying hens were divided into experimental groups with dietary supplementation of low, medium and high doses (105, 106 and 107 CFU per animal per day) of the freeze-dried culture and control group fed a basal diet alone for 11 weeks. Serum antioxidant parameters were measured during the experimental period, and all the animals were slaughtered for the measurement of liver fat content and liver histological examination by biopsy. Our experimental data demonstrated that liver fat contents in the medium- and high-dose groups were significantly reduced by 32.4% and 48.2% (P < 0.01), respectively, while a reduction of only 9.4% was observed for the low-dose group as compared with the control group. Oil red O staining of liver slices showed that Lactobacillus paracasei KL1 reduced the deposition of fat droplets in the liver in a dose-dependent manner. The results of antioxidant assays indicated that serum total antioxidant capacity was significantly higher by 16.3%, 13.9% and 14.8% in the three treatment groups than in the control group, respectively. Serum superoxide dismutase (SOD) activity levels in the medium-dose group were increased significantly by 19.4%, and by 11.3% and 16.4% in the low- and high-dose groups, respectively in comparison with the control group. However, malondialdehyde (MDA) content and glutathione peroxidase (GSH-Px) activity had no significant change (P > 0.05). The above results suggested that Lactobacillus paracasei KL1 has the ability to strongly inhibit lipid peroxidation in the liver of laying hens.

Key words: Lactobacillus paracasei, animal experiment, fatty liver, lipid oxidation