THE ALTERATION OF MILK CONTENT BY GENETIC ENGINEERING AND RECOMBINANT DNA-MEDIATED SELECTION TECHNIQUES

Since the advent of gene cloning technology, suggestions have been made of specific alterations that could be engineered into the genomes of cattle, sheep or goats to alter their milk composition. These alterations could affect milk protein characteristics or quantity in ways which might be of benefit to milk processing and dairy product manufacturing industries. Other changes could improve the suitability of bovine milk for human consumption. In addition, animals could be engineered to synthesize valuable foreign proteins, such as pharmaceuticals, to be secreted in milk. In this paper, we evaluate these suggestions critically, taking into account current understanding of milk composition and processing, as well as recent information concerning the structure and regulation of genes coding for proteins involved in determining milk content. All these suggested alterations depend on successful production of transgenic animals capable of efficiently expressing introduced genes. The view is examined that some improvements in type or amount of certain milk proteins might better be achieved by conventional breeding practices, or by breeding systems that would rely on recombinant DNA techniques for methods of selection. Key words: Casein, beta-lactoglobulin, α-lactalbumin, plasmin, transgenic, bovine, ovine, lactose