Brown adipose tissue (BAT) is critical for mammal's survival in the cold environment. UCP1 is responsible for the thermogenesis in the BAT and is recognized as a specific marker for BAT. Pig is a useful medical model for humans due to its similarity in size and physiology. Pig is also important economically as a meat‐producing livestock. A previous study identified brown adipocytes in different pig adipose tissues by microscopic and electron microscopic methods. In one immunoblotting study, UCP1 was not detected in any porcine adipose tissues by the rabbit anti‐rat UCP1 antibody. But, a recent study showed that UCP1 protein is present in porcine adipose tissue and is responsive to postnatal leptin treatment. These authors used an ovine UCP1 antibody in their immunoblotting assay. However, the positive result may be explained by non‐specific hybridization with other mitochondrial anion carrier proteins, such as UCP2 or UCP3 by the antibody used in the previous study. Therefore, whether BAT or more precisely UCP1 protein, exists in pig has never been conclusively established. The objective of this study was to ascertain whether pig has UCP1 protein.In this study, we used rapid amplification of cDNA ends (RACE) technique to obtain the UCP1 mRNA 3′ end sequence, confirmed only exons 1 and 2 of the UCP1 gene are transcribed in the pig. We then cloned the pig UCP1 gene exons 1 and 2, and used these two exons to express pig UCP1 protein by E. coli BL21. We purified and used the expressed pig UCP1 protein as antigen for antibody production in a rabbit. Immunoblotting assay was conducted using inguinal fat, interscapular fat, epididymal fat, retroperitoneal fat, supraclavicular fat, perirenal fat, neck fat, liver, muscle from pigs. Mice BAT was used as a positive control. Our rabbit anti‐pig UCP1 antibody can hybridize with mice UCP1 protein (about 35KD) and pig UCP1 (about 15KD) expressed by E. coli BL21, but could not detect UCP1 protein in any pig tissues. Our data clearly show only exons 1 and 2 of UCP1 gene are transcribed in pig adipose tissue, but the truncated pig UCP1 mRNA is not being translated. Since these results unequivocally demonstrate that pig has no UCP1 protein; therefore, the pig has no brown adipose tissue.Support or Funding InformationThis work was supported by the National High Technology Research and Development Program 863 (#2013AA102502); the National Natural Science Foundation of China (#31372283); The Team Project of Guangdong Agricultural Bureau (#2016LM2148) and the Natural Fund Key Projects of Guangdong Province (#2015A030311006). C.H. is supported by the USDA National Institute of Food and Agriculture, Hatch project HAW‐H2037, managed by the College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa.