The difference between the price paid by the refrigerators for pedigree-cattle and the price of animals of creole blood, which the local market takes, hurries up the transformation of the herd. In order to watch reproduction and nurse the pasture, the ranches put up wire-fences. But the breeding methods are especially modified by the introduction of lucerne. It spread in the south of Cordoba and west of the Buenos Aires province from 1895 onward, and from 1905 onward in part of the San Luis province. There were already small lucerne farms in the Buenos Aires province. A description that was written at the end of the eighteenth century speaks of lucerne farms round the town which were reserved for feeding draught cattle.[95] But the area from which the cultivation of lucerne started at the close of the nineteenth century is the district of the Cordoba province that is crossed by the line from Rosario to Cordoba, completed about 1870 to Bellville and Villa Marina. The lucerne farms there were not created by the breeders, and the lucerne was at first intended for export to Rosario and Buenos Aires in the form of dry fodder. The trade in dry fodder has remained good there. The 1908 Census gives 128 square kilometres of lucerne for cutting in the Tercero Abajo department (Villa Maria) and 267 square kilometres in the Union department (Bellville).[96] [95] Fernando Barrero, _Descripcion de las provincias del Rio de la Plata_ (published by the Argentine Ministry of Foreign Affairs, Buenos Aires, 1911). [96] Amongst the specialized industries connected with the development of the lucerne farms we must mention the growing of lucerne for seed, which has settled in the dry zones, where the lucerne is not so much invaded by other species; for instance, the district of Madanos, west of Bahia Blanca. [Illustration: MAP III.--THE CATTLE-BREEDING AREAS. _The density of the herd is slight in the maize belt. It is considerable in the centre and east of the Pampean region, which supply the refrigerators with pedigree stock of good weight. The density is considerable also in the north of Mesopotamia, but the cattle there are less valuable and are taken by the saladeros of the Uruguay. The presence of the tick, which inoculates cattle with Texas fever, is the chief obstacle to the improvement of the herd in the north of Argentina._ To face p. 188.]