CHEMICAL AND ELECTRON-MICROSCOPIC STUDIES OF CATTLE (BOS-TAURUS) WITH4 TYPES OF PHENOTYPIC PIGMENTATION

The biological behavior of the pigmentary phenotypes of four breeds of cattle has been analysed: the black pigmentation of Holstein Friesian ; the red pigmentation of Limousin; the dilution in Charolais; and the postnatal disappearance of red pigmentation in Chianina. The analytic techniques included the characterization of melanins by high-performa nce liquid chromatography, the examination of follicular melanocytes b y light microscopy, and the examination of melanosomes by electron mic roscopy. The black phenotype was very strongly eumelanogenic. The red phenotype in Limousin is polymorphic: individual follicular melanocyte s contain both mature eumelanosomes and pheomelanosomes. Charolais and Chianina cattle exhibited a dramatic reduction in melanogenic activit y, which was characterized by the almost exclusive presence of prephao emetanosomes in Charolais and of immature premelanosomes in Chianina. In the dilute Charolais phenotype, the density of distribution of foll icular melanocytes also seemed to be reduced. The genes that are respo nsible for these four phenotypes seem to act on the maturation, differ entiation, and density of distribution of the melanosomes.