According to the Livestock Census of the mainland of the Kingdom of Portugal (1870), the definition of Bísaro is the name given in the provinces of central and northern kingdom to the esgalgado pig, piernialto ears and falls, to distinguish it from roundwood and piernicorto pork Alentejo. The Celtic name was used by Sanson to express the antiquity of this type of pig, which was the only one that existed in the Celtic peoples of ancient Gaul.

J.F. Macedo Pinto in 1878 in the Compendium of Veterinary wrote: (...) "Bizaro Type 1 or Celtic - The descendants of these breeds of wild and common boar belongs exclusively to Europe. They are distinguished by the following characteristics: head short and thick flat face, long snout, large mouth, large ears, which droop down below the line of the eyes, elongated body, arched back, chest with the vertical diameter much larger than the horizontal which gives them the boat-like shape, long legs, and black bristles with most individuals. The many races that are found throughout> Europe, mainly in the north hardly differ from each other by their degree of corpulence. Our common breed of pigs in the Northern provinces also enters in this type that has a slow development, completing their growth at 2 years of age and therefore it is difficult for them to gain weight. It gives good meat, but are very bony and atocinan little. (…)
 

(…) "In Trás-os-Montes, Minho, Beira and Extremadura north of the river Tajus, this type dominates; varieties distinguished by their bulk, colour and a larger or smaller number of sows. Pigs have been found measuring 1.5 meters from head to tail and about 1 meter tall, weighing 200 to 250 kg. In the largest part of our country they are black; the ones that are all white and fat, which the illustrious vet S.B. Lima (1) claims to have seen in Monsão and Valladares, are the ones we call ´gallegos´, originating from the Spanish province Galicia. Black or white, or even spotted, some that have many bristles and others, which are called ´molariños´, that have little bristles and a smooth, soft skin are the ones thought to be more flavourful. In general all our animals are slow-growing (adult pigs need two to five years to grow) and it is hard for them to get fat, producing more lean meat than fat and accumulate it more like lard in thick layers of fat. Most of the animals eat little, especially during the priming time and their complexion is not the most robust." (...)

Virgílio Taborda wrote in 1932: (...)" The guy who set up in Trás-os-Montes the bulk of the species is bísaro, of slow growth, difficult to fatten up and richer in meat than in fat ....." "Potatoes and chestnut found in abundance in the groves form the basis of their diet, especially in the period of feeding. In many places, pigs roam free in the fields, ... .., benefiting from the acorns of the oaks (...)

Póvoa Janeiro in 1944 in a farming bulletin wrote: "The group shows the intellectual state that is the race. It shows slow and ungraceful movements. They are very prolific; litters sometimes contain twenty or more piglets. Looking at the quality of the meat we can say it is lean and low fat. The streaky bacon is little and the taste varies with the alimentation of the animals”.

In 1967 Ramiro Ferrão and J. Alves Mira state: "To the north of the river Tajus, a pig is bred of a type of meat that comes from the ethnic group revered to as Celtic trunk of the species that usually dominate the areas of industrial land in the south" (...)

(...) The pig that lives in the regions north of the river Tajus is specially designed for meat production which unfortunately is accompanied by the production of bone and skin, which greatly devalues it (...)