The former Barra Slaughterhouse was an important municipal structure managed by the Leal Senado (now IAM, the Municipal Affairs Bureau), featuring a series of three buildings, which were used for slaughtering cattle and pigs, with their barns in the vicinity. It was the only municipal abattoir in the Macao Peninsula in the twentieth century. According to the Governor's Order no. 75 of the Official Gazette dated 22 October 1873, a slaughterhouse was completed at the Barra area and placed under the management of the Leal Senado. The Macao Urban Material Improvement Report, dated 20 November 1883, published by the Portuguese Macao government, points out that the municipal slaughterhouse was "one of the factors contributing to the poor hygiene of the city", in that it was "not in a satisfactory condition in terms of equipment, with poor ventilation, insufficient space, a gravel floor, and a tendency to seepage" (referring to the seepage of blood-contaminated wastewater on the gravel floor). Therefore, the committee responsible for studying the improvement of the material conditions of Macao recommended that the abattoir be relocated to the vicinity of the Fort Dona Maria II. However, according to the historical records and plan, the government started to build ancillary facilities such as corrals and troughs in the vicinity of the former Barra Slaughterhouse site in 1887, and on the plan there is already the existing complex, which was not in such poor conditions as described in the aforesaid report, and the abattoir has not been relocated away from the Barra area. Therefore, the structure is presumed to have been built after 1883 but before 1887 and was altered between 1916 and 1917 to form a complex comprising animal storage facilities, offices, and an abattoir. The entire structure is clearly visible in historical photographs from the 1920s and aerial photographs from 1941, standing along the Barra Dock.
The laws and regulations related to animal slaughtering in Macao had also been improving. According to the Regulation of the Slaughterhouses, published in the Official Gazette of the Portuguese Macao government on 8 July 1882, there were official slaughtering facilities, supervised by the Leal Senado, as early as before 1857, when there were also relevant laws and regulations. The Regulation of the Slaughterhouses stipulated that all animals used for food must be quarantined for examination before they could be kept in the barns, and that they must be slaughtered, quartered, and washed in the Barra Slaughterhouse before they could be sent to the market for sale. In the following year, the Portuguese Macao government published the Macao Urban Material Improvement Report dated 20 November 1883, which reiterated the regulations on the slaughterhouse, including the proposal to build annex buildings and the treatment to be given to livestock offal. In 1925, the government promulgated a new Regulation of the Slaughterhouses, the Regulation of the Cattle Barns, and the Regulation of the Swine Barns, thus improving the slaughtering facilities and hygiene regulations of the Barra Slaughterhouse and installing machinery to make the abattoir safer and more efficient.
As the slaughtering demand continued to increase, one of the barns adjacent to the abattoir was converted to be a part of the slaughterhouse, which helped to separate the slaughtering of swine and cattle. It was not until 1987 when the municipal slaughtering service was formally relocated to Ilha Verde that the Barra Slaughterhouse and its associated buildings ended their more than a century-long historical mission and were converted into dormitories, offices, and archives.
The former Barra Slaughterhouse, which has stood on the side of Barra Hill for over a century, was an important municipal development in Macao in the late 19th and early 20th centuries. The complex was designed to meet the hygienic requirements of an abattoir for the purpose of slaughtering, while its exterior design is characterised by eclectic architecture, a typical integration of functionality and aesthetics, a representative of the city’s municipal development of its time. As early as a century ago, Macao started to regulate the supply, examination, slaughtering, distribution, and transportation of animals for food and set up a system of municipal supervision, which was an indicator of the city's modernisation. The Barra Slaughterhouse and its rules and regulations were important symbols of such modernisation, and an essential testament to Macao's gradual progress in urban development.