Effects Of Probiotics Or Soybean Oil On Growth Performance And Intestinal Flora Of Grass Carp

Grass carp is the largest freshwater economic fish in China.In this study,probiotics or soybean oil were added to the practical feed of grass carp respectively.The production performance,physiological and biochemical indexes and intestinal flora of grass carp were evaluated,aimed to improve the grass carp feed utilization rate,reduce nitrogen emissions,and provide certain reference data to develop efficient,environmentally friendly feeds for grass carp.The results were as follows:1.Effects of probiotics on production performance,physiological and biochemical indicators and intestinal flora of grass carp.In order to explore the possibility of improving feed utilization ratio with different probiotics.1260 tail grass carp(110.23 ±0.43 g)were randomly divided into 3 groups,with 6 repetitions in each group,added 0%,0.5% and 2% probiotics respectively.The production performance,physiological and biochemical index were measured after raised 60 days.The fecal bacterial composition was investigated by Miseq high-throughput sequencing of the V3-V4 region of the 16 SrDNA gene.Results showed:(1)The addition amount of 2% probiotics significantly increased weight gain rate and specific growth rate of grass carp(P<0.05),and decreased the feed conversion ratio,viscerasomatic index(P<0.05),reduced nitrogen emissions.(2)The addition amount of 2% probiotics significantly decreased glutamase and glutamase transaminase in grass carp serum(P<0.05),and increased the catalase and superoxide dismutase(P<0.05).(3)The activity of intestinal enzyme was increased with the addition of probiotics,and there were differences in different regions.The addition amount of 2% probiotics significantly increased the activity of midgut amylase,midgut lipase and postgut lipase(P<0.05).The activity of 0.5% amylase in the anterior intestine was the highest,which was significantly different from that in the group of 2%(P<0.05).(4)The addition amount of 2% probiotics significantly reduced the abundance of Fusobacteria,significantly increased the abundance of Cyanobacteria and Mycobacteria,and decreased the abundance of Cetobacterium(P<0.05).Results showed :Probiotics formed by combination of Bacillus subtilis,yeasts and Lactobacillus affected the diversity and richness of intestinal flora,improved the antioxidant capacity of liver,increased the activity of amylase and lipase.And it increased protein deposition rate,promoted grass carp growth,increased meat yield,reduced the feed coefficient and reduced nitrogen emissions.In this study,grass carp had the best production performance,which could improve economic and ecological benefits,after adding 2% probiotics in practical feed.2.Effects of soybean oil on the production performance,physiological and biochemical indexes and intestinal flora of grass carp.In order to use fat effectively,save protein and reduce nitrogen emissions,1260 tail grass carp(112.25±1.14g)were randomly divided into 3 groups,with 6 repetitions in each group.Each group had 6 repetitions,and 0%,3% and 6% soybean oil was added to grass carp's practical feed,and grass carp was raised for 42 days.Results showed:(1)The 6% soybean oil group significantly increased the weight gain rate,specific growth rate and viscerasomatic index(P<0.05),but also significantly increased the crude fat content of whole fish,muscle and liver of grass carp(P<0.05).(2)6% soybean oil group significantly increased triglyceride,high-density lipoprotein,low density lipoprotein and midgut lipase activity in serum(P<0.05).(3)Soybean oil reduced the abundance of Fusobacteria and increased the abundance of Firmicutes and Bacteroides,but it was not significant(P>0.05);At the genus level,the addition of soybean oil decreased the abundance of Cetobacterium and increased Erysipelatoclostridium,Bacteroides and Romboutisa abundance,but it was not significant(P>0.05).Results showed: Reasonable increase feed fat content could improve the utilization rate of feed protein,promote the growth of grass carp and reduce nitrogen emissions by raising the grass carp lipid metabolism and intestinal lipase activity.But it would increase the crude fat content of grass carp.In this study,when the amount of soybean oil was 6%,the growth effect of turbot was the best and the economic benefit was the best.