Isolation of a probiotic lactic acid bacteria and effects of fermented feed prepared from it on growth performance, serum antioxidant and immune indexes for piglets

In order to find new probiotic lactic acid bacteria which can be used to product fermented feed for piglets, lactic acid bacteria were isolated and purified from the feces of healthy piglets using MRS medium. The strain was identified through 16S rDNA sequencing combined with physiological and biochemical experiments. On this basis, a composite inoculum of probiotic lactic acid bacteria and Bacillus cereus PBC-1 added to the base diet and was used to produce fermented feed. 128 healthy twenty-eight-day-old crossbred piglets were randomly divided into 4 groups: control group and 2%, 5% and 10% fermented feed groups with 3 replicates per group and 10 piglets per replicate. The piglets in the control group were fed the basal diet, and the piglets in 2%, 5% and 10% fermented feed groups were fed the trial diet supplemented with 2%, 5% and 10% fermented feed instead of the corresponding proportion of the basal diet, respectively. The pre-test period was 2 days and the experimental period was 28 days. At the end of the experimental period, the average daily feed intake, average daily weight gain and diarrhea rate of piglets were counted. Blood samples was collected from each piglet and serum was separated. Serum antioxidant indexes, immune indexes and inflammatory factors were detected by kit. The results showed that a strain of Lacticaseibacillus casei was isolated from the feces of healthy piglets and named ZYSJ-2. Compared with the control group, the average daily feed intake of piglets in 2%, 5% and 10% fermented feed groups was not significantly different（P＞0.05）, but the average daily weight gain was significantly increased（P＜0.05）, the diarrhea rate of piglets was significantly decreased（P＜0.05）. Serum total antioxidant capacity（T-AOC） and activities of glutathione peroxidase（GSH-Px）, total superoxide dismutase（T-SOD） and catalase（CAT） were significantly increased（P＜0.05）, while serum malondialdehyde（MDA） concentration was significantly decreased（P＜0.05）. The mass concentrations of serum immunoglobulin A（IgA）, immunoglobulin M（IgM） and immunoglobulin G（IgG） of piglets in 2%, 5% and 10% fermented feed groups were significantly higher than those in the control group（P＜0.05）, and the mass concentrations of inflammatory factors interleukin-1β（IL-1β）, interleukin-6（IL-6）, interleukin-10（IL-10） and tumor necrosis factor-α（TNF-α） were significantly lower than those in the control group（P＜0.05）. These results indicated that the screened ZYSJ-2 could be used for the production of fermented feed for piglets. The composite fermented feed prepared with Lacticaseibacillus casei ZYSJ-2 and Bacillus cereus PBC-1 could improve the growth performance of piglets, enhance their antioxidant capacity and immune abilities, and improve their health level. It was appropriate to mix the composite fermented feed with the basal diet of piglets at a ratio of 5%.