Effects Of Different Sugar On Gut Hetalth And Gut Microbiota Of Overwintering Honeybees

During winter of northern China,honeybees can't access to food from the outside nature without nectar source,and can only consume stored sugars.Therefore,the quality of winter food directly affected the health of honeybees.Naturally,honey is the main food for honeybees in the winter.However,sucrose and high fructose syrup are usually used as the food for honeybees in the commercial beekeeping because beekeeper took out all honey stored in colony for economic benefit.There is not enough scientific basis when beekeepers selecting the food for honeybees.And for this reason,it is vital to exploring different sugar which is more suitable for the feed in winter,that are honey,high fructose syrup and sucrose.The experiment was conducted to study the effects of different sugar on gut microbiota,intestinal physicochemical indexes and intestinal tissue development of overwintering honey bees,to recommend the alternative wintering dietary for beekeepers.Nine overwintering colonies of honeybees(Apis mellifera ligustica)with the same colony population were used in this experiment.The nine colonies were randomly divided into three groups,and each group contained three colonies.Each group was fed different food— honey,sucrose and high fructose syrup — from Nov 2nd to Nov 22 before winter.In order to determine the intestinal digestive enzyme activity,samples were collected in early November,early January and early March,respectively.And,in early January,we collected samples to determine the intestinal tissue development and antioxidant enzymes genes expression.And,the midgut and rectum were collected in early November and early January,respectively.The midgut and rectum were sampled to determine the bacterial composition using the Illumina MiSeq platform to target the V4 regions of 16 S rDNA.The results showed as follows: 1.The effects of different sugar on intestinal digestive enzyme activity and antioxidant enzymes genes expression of overwintering honey bees:(1)Fructose corn syrup group and honey group amylase activity was significantly higher than that of sucrose group in early January(P<0.05).(2)Different sugars did not significantly affect the activity of sucrase(P>0.05).(3)Protease activity of fructose corn syrup group was obviously higher than that of sucrose group and honey group in January(P<0.05).(4)The relative expression of Sod1 gene from sucrose group was obviously higher than that of fructose corn syrup group and honeygroup(P<0.05).2.The effects of different sugar on intestinal tissue development:The midgut wall thickness of sucrose group and honey group were obviously higher than that of fructose corn syrup group(P<0.01).The midgut crypt deepness of sucrose group and honey group were obviously higher than that of fructose corn syrup group(P<0.01).3.Honeybee gut microbiota is altered by sugar feed type and overwintering:(1)the most abundant bacteria are Proteobacteria(63.17%),Firmicutes(17.61%),Actinobacteria(4.06%)and Bacteroidetes(1.72%)at the level of Phylum.Moreover,Lactobacillus(15.91%)and Bifidobacterium(3.24%)were the most abundant bacterium at the level of Genus.(2)Actinobacteria,Bifidobacterium,Alphaproteobacteria and Rhizobiales increased in the colonies with sucrose,while Gammaproteobacteria and Pasteurellales increased in the colonies with honey.Moreover,Betaproteobacteria and Neisseriaceae increased in the colonies with high fructose syrup.On the whole,diet can alter the gut bacteria composition of honeybees,Honey can improve intestinal digestive enzyme activity in overwintering honeybees,honey and sucrose are beneficial to the growth of intestinal tissue in the overwintering honeybees,and sucrose could improve the overwintering honeybee intestinal antioxidant gene expression.Therefore,honey and sucrose as better feed of honeybee wintering than fructose corn syrup.