In this study,we investigated the effects of high ambient temperature on lipid metabolism in finishing pigs.Sixteen pigs（（79.6±1.2） kg） were randomly assigned to two groups：（1） ambient temperature of 30℃ with ad libitum access to feed（HT;n=8） and（2） ambient temperature of 22℃ and fed the average amount consumed by eight pigs in HT group on the previous day（PF;n=8）.After 21 days of constant exposure to different environmental conditions,all the pigs were euthanized,and blood and tissue samples were obtained.High ambient temperature increased the proportion of backfat（P=0.04,＋21.6%）and flare fat（P〈0.01,＋43.3%）.Compared with pair-fed pigs,the activities of fatty acid synthase（FAS） and malic enzyme in backfat and flare fat were lower（P〈0.05） in heat-stressed pigs,as were the amounts of acetyl-CoA-carboxylase and FAS in the longissimus muscle（LM）,the amount of FAS in backfat（P〈0.01）,and FAS activity in the liver（P〈0.01）.Ambient temperature did not affect the amount of hormone-sensitive lipase in different tissues.The amount of lipoprotein lipase in flare fat tended to be higher（P=0.09,＋28.3%）,and the activities of β-hydroxyacyl coenzyme A dehydrogenase in front and back of LM were lower（P〈0.01,-48.3 and-49.8%,respectively） at 30℃ than at 22℃.The plasma concentration of high-density lipoprotein tended to be lower（P=0.08）,but the plasma concentrations of very low-density lipoprotein（VLDL）（P=0.09,＋50.0%） and nonestesterified fatty acid（NEFA）（P=0.04,＋44.2%） were higher in heat-stressed pigs.We concluded that high ambient temperature depressed de novo fatty acid synthesis in both adipose tissues and the liver.However,β-oxidation of fatty acid in skeletal muscles was also inhibited in the high-temperature environment.As a result,more plasma NEFAs were used to synthesize VLDLs in the liver and were absorbed by adipose tissues.This may be one reason that high ambient temperature enhances the accumulation of backfat
