Heat stress affects fecal microbial and metabolic alterations of primiparous sows during late gestation

Background:Heat stress(HS)jeopardizes intestinal barrier functions and augments intestinal permeability in pigs.However,whether HS-induced maternal microbial and metabolic changes in primiparous sows during late gestation remains elusive.We present here,a study investigating the fecal microbial and metabolic responses in late gestational primiparous sows when exposed to HS.Methods:Twelve first-parity Landrace×Large White F1 sows were randomly assigned into two environmental treatments including the thermoneutral(TN)(18–22℃;n=6)and HS(28–32℃;n=6)conditions.Both treatments were applied from 85 d of gestation to farrowing.The serum and feces samples were collected on d 107 of gestation,for analyses including intestinal integrity biomarkers,high-throughput sequencing metagenomics,short-chain fatty acid(SCFA)profiles and nontargeted metabolomics.Results:Our results show that HS group has higher serum Heat shock protein 70(HSP70),lipopolysaccharide(LPS)and lipopolysaccharide-binding protein(LBP)levels.The gut microbial community can be altered upon HS by usingβ-diversity and taxon-based analysis.In particular,the relative abundance of genera and operational taxonomic units(OTUs)related to Clostridiales and Halomonas are higher in HS group,the relative abundance of genera and OTUs related to Bacteroidales and Streptococcus,however,are lower in HS group.Results of metabolic analysis reveal that HS lowers the concentrations of propionate,butyrate,total SCFA,succinate,fumarate,malate,lactate,aspartate,ethanolamine,β-alanine and niacin,whereas that of fructose and azelaic acid are higher in HS group.These metabolites mainly affect propanoate metabolism,alanine,aspartate and glutamate metabolism,phenylalanine metabolism,β-alanine metabolism,pantothenate and CoA biosynthesis,tricarboxylic acid cycle(TCA)and nicotinate and nicotinamide metabolism.Additionally,correlation analysis between significant microbes and metabolites indicated that the HS-induced microbiota shift is likely the cause of changes of intestinal metabolism.Conclusions:Taken together,we reveal characteristic structural and metabolic changes in maternal gut microbiota as a result of late gestational HS,which could potentially provide the basis for further study on offspring gut microbiota and immune programming.

Effects of shape and particle size on the photocatalytic kinetics and mechanism of nano-CeO_(2)

Nanomaterials have been widely applied to many fields because of their excellent photocatalytic performance.The performance is closely related to the catalytic kinetics,but it is not completely clear about the influencing regularities of shape and particle size on the photocatalytic kinetics of nanomaterials and the photocatalytic kinetic mechanism.In this paper,nano-CeO_(2)with different shapes and particle sizes were prepared,the kinetic parameters of adsorption and photocatalytic degradation were determined,and the effects of shape and particle size on the kinetics of adsorption and photocatalysis and photocatalytic mechanism were discussed.The results show that the shape and particle size have significant influences.With the decreases of diameter,the performances of adsorption and photocatalysis of nano-CeO_(2)are improved;and these performances of spherical nano-CeO_(2)are greater than those of linear nano-CeO_(2).The shape and particle size have no effects on the kinetic order and mechanism of the whole photocatalytic process.Then a generalized mechanism of photocatalytic kinetics of nanomaterials was proposed and the mechanism rate equation was derived.Finally,the conclusion can be drawn:the desorption of photodegradation products is the control step of photocatalytic kinetics,and the kinetic order of photocatalytic degradation reaction is 1.The mechanism is universal and all nanomaterials have the same photocatalytic kinetic mechanism and order.