Effects Of Environmental Temperature On Energy Metabolism Of Growing Pigs

In this experiment,A total of 36 crossbred barrows(Duroc × Large White × Landrace)were used to investigate the energy metabolism of growing pigs at different ambient temperatures using the open-circuit respiratory chambers.Also,the metabolic metabolomics and hormonal markers in growing pigs were identified using Gas Chromatography-Mass Spectrometry and Liquid Chromatography-Mass Spectrometry techniques.Experiment 1:Effect of ambient temperature on energy metabolism of growing pigs.36 crossbred barrows with an initial body weight of 25.0±1.2 kg were allotted into 6 open-circuit respiratory chambers with 6 temperature gradients(18,21,24,27,30 and 33 ?,respectively).The experimental period was divided into 6 stages with each stage containing 7 days for adjustment and 6 days for the trial.The digestible energy and metabolizable energy were measured by total collection method,and the net energy values were measured using indirect calorimetry method.The metabolites and hormone markers in plasma were measured.Blood samples were collected from the anterior vena cava of pigs at the end of each stage of the experiment.The results show that different environmental temperature had a significant impact on average daily feed intake,heat production,protein deposition and retained energy deposition of growing pigs(P<0.01).The highest feed intake was 1.47 kg/d at 18? and the lowest was 1.11 kg/d at 31.6 ?;With the increase of ambient temperature,the deposition of protein and retained energy deposition firstly increased and then decreased(P<0.01).At 24?,the deposition of protein and retained energy deposition of growing pigs were the highest,and entropy of respiratory firstly increased and then decreased with the increment of ambient temperature.Under the condition of fasting,entropy of respiratory was significantly affected by the ambient temperature(P<0.01).Experiment 2:Determination of plasma metabolism and serum hormones in growing pigs at different ambient temperatures.The results showed that environmental temperature had no significant effect on the concentration of insulin and glucagon in the blood samples of growing pigs,and with the increment of ambient temperature,the concentration of glucagon in growing pigs firstly increased and then decreased(P<0.01).The lowest concentration of glucagon was 63.16 ng/ml at 27?,and the highest was 98.11 ng/ml at 31.6?.The concentration of triiodothyronine in blood sample of growing pigs decreased significantly with the increment of ambient temperature(P= 0.02),and the highest was 0.63 ng/ml at 18?,the lowest was 0.51 ng/ml at 31.6?.The concentration of thyroxin and cortisol in blood sample of growing pigs decreased significantly with the increment of ambient temperature,The highest concentrations of thyroxin and cortisoal was observed at 18?(58.60 ng/ml and 69.23 ng/ml),respectively,while the lowest values of these two hormones were 30.96 ng/ml and 29.05 ng/ml at 31.6?,respectively.The effects of different ambient temperatures on metabolite presence in plasma of growing pigs were analyzed using LC-MS.The results showed that different ambient temperatures had a significant effect(P<0.05)on the metabolic patterns of pigs.Separation trends were observed when pig were reared under 21?,27 ? and 33?.By comparing HMDB,KEGG database and standard mass spectrometry,it is concluded that environmental temperature mainly causes the changes of carbohydrate,amino acid metabolism and fat metabolism in growing pigs,Carbohydrate metabolism mainly includes the changes of plasma lactate,glucose and galactose,which increased significantly the content of lactate in blood,and decreased the concentration of glucose and galactose(P<0.01).The amino acid metabolism mainly includes of proline,hydroxyl-proline,cysteine,omithine,creatine and other small molecules.The fatty acids metabolism includes linoleic acid,four arachidonic acid,bile acids,sphingomyelin,phyto-sphingosine,stearic acid and its derivatives,which will lead to linoleic acid and its metabolites increased significantly in high temperature environment.