Effects Of Different Carbohydrates On Colony Population,Wax Production And Web Lipid Metabolism Of Honeybees

Carbohydrate,the energy support for bee’s various life activities,provides the main raw material for bee wax secretion.In beekeeping,honey,sucrose and high fructose corn syrup（HFCS）are used to fee honeybee.However,the effects of these carbohydrate diets on the wax production performance and its mechanism of honeybees are not clear.In this study,Apis mellifera ligustica were fed three different types of carbohydrate diets,including honey,sucrose and HFCS.The effects of different carbohydrates on wax secretion and its metabolic mechanism were investigated by measuring the wax secretion performance,colony reproduction performance and web lipid metabolome.This study provides theoretical basis for the selection and utilization of different types of carbohydrate feed in beekeeping.In this study,15 Apis mellifera colonies with similar population were randomly divided into 3 groups with 5 replicates per group.The colonies were fed with honey,sucrose and fructose corn syrup,respectively.The feeding period was 60 days,including 24 days of pre-feeding period and 36 days of experimental period.Water and pollen intake ad libitum.Colony population,cap sealing,and wax production were measured on days 12,24,and 36day of the experimental period.The beeswax of workers was collected to determine the size.On day 21,1-day-old newly emerged workers were labeled,and 9-,15-and 21-day-old workers were collected to determine midgut thickness,hemolymph physiological and biochemical indexes,crude fat content,antioxidant and immune-related enzyme activities and gene expression levels,as well as key enzyme activities and gene expression levels of wax synthesis pathway.The web of 15-day worker bees in each group was dissected for lipidomics analysis.The results show that:1)The colony population of honey group and sucrose group was significantly higher than that of HFCS group（P<0.05）,but there was no significant difference between honey group and sucrose group（P>0.05）.The amount of lid sealing of bees fed honey group was significantly higher than that of sucrose group and HFCS group（P<0.05）,despite there was no significant difference in the amount of lid sealing between sucrose group and HFCS group（P>0.05）.The results showed that honey,the natural feed for honeybee colonies,had significantly better performance than sucrose and HFCS in promoting colony reproduction.2)During the experiment period,the wax production of bees fed with honey was 56.7%higher than that of HFCS group（P<0.05）.The wax production of bees fed with honey was13.6%higher than that of sucrose group,and that of bees fed with sucrose was 49.8%higher than that of HFCS group.The wax size of workers in honey and sucrose groups was significantly higher than that in HFCS group（P<0.05）,but there was no significant difference between honey and sucrose groups（P>0.05）.The results showed that honey was superior to sucrose and sucrose was superior to HFCS.3)The midgut thickness of 15-day worker bees in honey group was significantly higher than that of sucrose and HFCS groups（P<0.05）.The contents of hemolymph triglyceride and high density lipoprotein in 15-day worker bees fed honey group were significantly higher than those in sucrose group and f HFCS group（P<0.01）,but there was no significant difference between sucrose group and HFCS group（P>0.05）.The crude lipid content of worker bees in honey group at 15 days was significantly higher than that in sucrose group and HFCS group（P<0.01）.The results showed that feeding honey could increase the body fat content and benefit for the fatty acid synthesis.4)The activities of catalase（CAT）and phenol oxidase（PO）in 15-day worker bees fed sucrose group were significantly higher than those in HFCS group（P<0.05）,but there was no significant difference between honey group and sucrose group（P>0.05）.The activity of lysozyme（LZ）in 15-day worker bees in honey group and sucrose group was significantly higher than that in HFCS group（P<0.05）,but there was no significant difference between honey group and sucrose group（P>0.05）.The defensin and abaecin gene expression levels of 15-day worker bees in honey group and sucrose group were significantly higher than those in HFCS group（P<0.05）,but there was no significant difference in gene expression levels between honey group and sucrose group（P>0.05）.The results showed that honey and sucrose significantly improved the immune function of honeybees compared with HFCS.5)The activities of fat-acyl-Co A reduced enzyme（FAR）and wax ester synthase（WS）in15 days of worker bees fed honey were significantly higher than those in sucrose and HFCS groups（P<0.05）,but there was no significant difference in the activities between sucrose and HFCS groups（P>0.05）.The activities of fatty acid synthesis-related enzymes lipoyl Co A carboxylase（ACC）,fatty acid synthetase（FAS）and fatty acid dehydrogenase（FAD）in15-day worker bees fed honey group and sucrose group were increased（P>0.05）.The results showed that honey and sucrose increased the activity of key enzymes in the wax synthesis pathway and promoted the wax synthesis.6)Fatty acid analysis of worker bee webs showed that phosphatidylserine（PS）,phosphatidylcholine（PC）,free fatty acid,triglycerides（FFA）,phosphatidylethanolamine（PE）and triglyceride（TG）were the main lipids in the web of worker bees.Sucrose group had the highest abundance of medium FFA and C₂₂-C₃₂ long chain fatty acids（P<0.05）.The abundance of TG in the web of worker bees in honey group was significantly higher than that in sucrose and HFCS groups（P<0.05）.The unsaturation of PC in the web of worker bees in sucrose group was significantly higher than that in honey and HFCS groups（P<0.05）.The results showed that sucrose group enhanced the formation of long chain fatty acids as substrate of the wax synthesis pathway and promoted the wax synthesis.This study showed that the different type of carbohydrate affected colony population and wax secretion performance.Feeding honey enhanced the colony population and increased the wax performance of bee colonies.Feeding sucrose promoted the formation of long chain fatty acids,the substrate of waxy synthesis pathway,which was conducive to waxy synthesis.Compared with honey and sucrose,HFCS had no effect on wax secretion of honeybees.