Effects Of Dietary Lysozyme On Growth Performance, Intestinal Morphology, Immunity And Intestinal Microbiota In Weaning Piglets

Lysozyme is a hydrolysis enzyme that can hydrolyze cell wall of bacteria. As functional protein with antibacterial effects, lysozyme is a potential substitute for antibiotics that is safe and effective. Lysozyme was documented to be capable of improving growth performance and intestinal health of weaning piglets. However, the optimal supplementary level of lysozyme in feed that can substitute antibiotics is still unclear. The protective effect of dietary lysozyme on intestine of E.coli challenged weaning piglets is also not well revealed. Therefore, the present study was conducted to determine the effect of dietary lysozyme levels on the growth performance, intestinal morphology and immunological function of weaning piglets and the effect of dietary lysozyme on intestinal morphology and microbiota of Ecoli challenged piglets.Trial 1 The effect of dietary lysozyme levels on growth performance, intestinal morphology and immunological function of weaning pigletsThe trial was conducted based on a one-factor design. A total of 150 piglets (Duroc x Landrace x Yorkshire,7.32 ± 0.90 kg) weaned at 25 day of age were randomly assigned to 6 treatments according to weight and sex, and each treatment included 5 replicates with 5 pigs in each replicate. Dietary treatments were designed as follows:(1) control group (fed the basal diet); (2) antibiotic group (basal diet+20 mg/kg Colistin Sulphate +50 mg/kg Kitasamycin); (3) L30 group (basal diet+30 mg/kg lysozyme); (4) L60 group (basal diet+60 mg/kg lysozyme); (5) L90 group (basall diet+90 mg/kg lysozyme); (6) L120 group (basal diet+120 mg/kg lysozyme). The whole experimental period was 28 days. On day 14 and 28 of dietary treatment, blood samples were collected to determine total complement activity, lysozyme activity and IFN-y concentration in serum. On day 28 of dietary treatment,4 pigs from control group, antibiotic group, L60 group and L90 group were killed. Peritoneal macrophage was collected to determine phagocytic activity. Ileum sample were collected for mRNA analysis. Samples of duodenum, jejunum and another portion of ileum were collected for morphological analysis. Results were as follows:(1) From day 0 to day 14 of dietary treatment, piglets fed control diet, antibiotic diet and diets containing different levels of lysozyme gained BW at the same rate (P>0.05). However, from day 14 to day 28 of dietary treatment and during the whole experimental period, piglets fed diet including antibiotics as well as 90 and 120 mg/kg lysozyme had greater (P< 0.05) ADG than piglets fed control diet. No significant difference was observed among groups regarding the average daily feed intake and feed conversation rate during any period of the dietary treatment (P>0.05).(2) Antibiotics and lysozyme supplementation had no effect on morphology of the ileum. Piglets from antibiotic group, L60 group and L90 group had greater (P< 0.05) villus height and villus height to crypt depth ratio in duodenum compared with piglets from control group. In addition, piglets fed diet supplemented with antibiotics and 90 mg/kg lysozyme had lower (P< 0.05) crypt depth and greater (P< 0.05) villus height to crypt depth ratio in jejunum compared with piglets fed control diet.(3) Activities of CH50 and lysozme in serum of piglets were not different (P> 0.05) among groups both at day 14 and 28 of the trial. Whereas, piglets fed diet containing 60 and 90 mg/kg lysozyme as well as antibiotic diet had greater (P< 0.05) phagocytic activity of peritoneal macrophage than piglets fed control diet(4) The mRNA expression of TNF-α, IFN-γ, IL-8 and TGF-β were not different (P> 0.05) among the dietary treatments.Trial 2 The effect of dietary lysozyme on growth performance, intestinal morphology and microbiota of E.Coli challenged weaning pigletsThe trial was conducted based on a 2 by 2 factorial design. A total of 60 weaning piglets (Duroc × Landrace × Yorkshire) were assigned by sex and body weight to 4 treatments (C-E.Coli、C+E.Coli、L-E.Coli、L+E.Coli), and each treatment included 15 replicates with1 pig in each replicate. Piglets in C-E.Coli and C+E.Coli group were fed with basal diet while piglets in L-E.Coli and L+E.Coli group were fed with basal diet supplemented with 100 mg/kg lysozyme. The trial began from the day when piglets were weaned and that day was designated as day 0 of treatment. On day 11 of dietary treatment, all piglets were weighed and blood samples were collected. Piglets from C+E.Coli and L+E.Coli group were then orally challenged with 2×109 CFU E.Coli. After 24 hours, Ecoli challenge was repeated one more time. Piglets from C-E.Coli and L-E.Coli group were orally gavaged with LB medium. On day 14 of dietary treatment,6 pigs from each group were sacrificed. Duodenum, jejunum and ileum samples were collected for determination of intestinal morphology. digesta in ileum and colon was collected for determination of intestinal microbiota.Results were as follows:(1) Average daily gain, average daily feed intake and gain:feed ratio were not affected by lysozyme supplementation or E.Coli challenge (P>0.05).(2) E.Coli challenge increased crypt depth in jejunum and ileum of piglets (P<0.05). Dietary lysozyme decreased (P< 0.05) crypt depth in jejunum while increased (P<0.05) villi height in ileum and villi height to crypt depth ratio in duodenum, jejunum and ileum of piglets. Compared with piglets from C-E.Coli group, piglets from L-E.Coli group had decreased (P<0.05) crypt depth in jejunum and increased (P<0.05) villi height and villi height to crypt depth ratio in ileum. Moreover, piglets from L+E.Coli group had lower (P<0.05) crypt depth in duodenum and ileum and higher (P<0.05) villi height to crypt depth ratio than piglets from C+E. Coli group.(3) E.Coli challenge increased (P<0.05) E.Coli count while decreased (P<0.05) lactobacillus and bifidobacterium count in ileum and colon of piglets. Dietary lysozyme decreased (P<0.05) E.Coli count while increased (P<0.05) lactobacillus and bifidobacterium count in ileum and colon of piglets. Compared with piglets from C+E.Coli group, piglets from L+E.Coli group had lower(P<0.05) E.Coli count and higher (P<0.05) lactobacillus count in ileum and colon and higher (P<0.05) bifidobacterium count in ileum. Piglets from L-E. Coli group had lower (P<0.05) E. Coli count in ileum while had greater (P<0.05) lactobacillus and bifidobacterium count in ileum and colon than piglets from L+E. Coli group.Conclusions:(1) Dietary lysozyme can accelerate the growth of weaning piglets by improving gut health and immunological function.(2) Dietary lysozyme can improve gut morphology, ameliorate intestinal injure and relieve weaning stress of E.Coli challenged piglets.(3) Supplementing 90 mg/kg lysozyme is as effective as antibiotics (20 mg/kg Colistin Sulphate+50 mg/kg Kitasamycin) in improving the growth performance of weaning piglets.