Biotechnological applications of research on animal pigmentation.

The implications of primary research on pigmentation for the colour manipulation of animal species of economic importance, and the facilitation of specific processes in biotechnology are discussed. Pigment technologists, especially poultry and fish nutritionists, are concerned with achieving the often specific type and degree of coloration demanded by consumers of various products (notably egg yolk, eggshell, broiler skin and salmon flesh). In most instances involving melanin (pelage, plumage and integument) and porphyrin (eggshell) pigments, the desired coloration is achieved through the use of alternate alleles at gene loci controlling the characters of interest. In contrast, coloration involving carotenoids is controlled primarily through pigment supplementation in the diet. The difference between carotenoids and other pigments involves the strict dietary origin of the former. Factors other than pigment availability, such as body condition, hormonal status and genetic constitution, also affect coloration. Although day-old chicks can be sexed by visual inspection of their genitalia, matings resulting in sex-associated phenotypes are in wide use. The genetic markers involved affect the colour of the plumage. The cloning of genes involved in pigmentation offers the prospect of deciphering the genetic control of animal pigmentation and modifying it to meet specific pigmentation needs.