Effect Of Two Lactic Acid Bacteria On Growth Performance,intestine Flora And Intestine Morphology Of Juvenile Cobia (Rachycentron Canadum)

In this study,we investigate the effects of Lactobacillus sp.and Enterococcus faecalis on the growth performance,digestive enzymes,immune enzyme activities,intestinal flora and intestinal morphology of juvenile cobia(Rachycentron Canadum).A total of 525 cobia with an initial average weight of 10.66±0.09 g were randomly assigned into 7 groups in triplicates with 3 individuals per replicate,25 juvenile cobia on every tank.Seven diets were supplemented with 0.1%(T1-0.1%),0.3%(T1-0.3%),0.5%(T1-0.5%)Lactobacillus sp.and 1%(T2-1%),3%(T2-3%),5%(T2-5%)Enterococcus faecalis respectively in a basal diet.Feeding twice a day(8:00 and 16:00),for approximately ten weeks.The results are shown as follows:1.Effects of Lactobacillus sp.and Enterococcus faecalis on the growth performance,digestive enzymes,immune enzyme activities of juveniles cobia(Rachycentron Canadum)The results show,adding Lactobacillus sp.and Enterococcus faecalis to the feed significantly increase the rate of weight gain and specific growth rate of cobia fish,and significantly reduce the feed coefficient.When the Lactobacillus sp.addition ratio is 0.3%and the Enterococcus faecalis addition ratio is 3%,both the weight gain rate and the specific growth rate reached the corresponding maximum values.The addition of Lactobacillus sp.and Enterococcus faecalis can significantly increase the intestinal digestive enzyme and trypsin digestive enzyme activities of juvenile cobia.The trypsin goes upward as the addition of proportion increasing.The activity of superoxide dismutase and lysozyme in the intestine of cobia with Lactobacillus sp.and Enterococcus faecalis was higher than that of the control group.2.Comparative analysis of the effects of two lactic acid bacteria on intestinal microflora structure of juvenile cobia(Rachycentron Canadum)With the addition of two kinds of lactic acid bacteria,the diversity and abundance of intestinal flora increased.Adding 5% of Enterococcus faecalis to the diet compared with the control group significantly improve the diversity of intestinal flora;The OTUs values of the lactic acid bacteria addition group were higher than those of the control group.It indicates that the addition of lactic acid bacteria can increase the richness and diversity of the intestinal flora of cobia in different degrees,with no significant difference.Adding two probiotics,Lactobacillus sp.and Enterococcus faecalis,can significantly improve the relative abundance of probiotic bacteria such as Thiopseudomonas,Marinobacterium,Lysinibacillus,Halomonas,Candidatus Arthromitus,Lactobacillus in the intestinal tract of cobia;the diversity of bacterial communities in the intestinal tract of juvenile cobia;and it has positive effect on the healthy intestinal microbes of juvenile cobia.3.Effects of Lactobacillus sp.and Enterococcus faecalis on the intestinal morphology of juvenile cobia(Rachycentron Canadum)The results of intestinal morphology measurement showed that the intestinal villus height of cobia was increased to different degrees after adding two kinds of lactic acid bacteria to the feed;and the addition of Lactobacillus spp.and Enterococcus faecalis in the feed significantly improve the intestinal velvet gland ratio.The ratio of velvet gland increased with the increase of the amount of velvet gland,indicating that the two lactic acid bacteria have a promoting effect on the intestinal villi of cobia,and have a positive effect on the digestion and absorption function of cobia.After the intestinal tissue was sliced and two lactic acid bacteria were added to the feed,the intestinal villus height of the cobia was increased to varying degrees.Especially after the intestine is most obvious,the change rule of the number of hindgut villi is consistent with the change law of the weight gain rate and specific growth rate of cobia.It can be speculated that the hindgut of cobia fish is the main place for digestion,absorption and transformation of nutrients.