In addition to milk's being a principal source of calcium, it has protein for healthy muscle growth, nutrition and human health. But there seems to be little common interest in the many protein constituents of milk's total protein. Now, after decades of research, the protein content in milk is partially used in payment to dairy farmers. Consumers presumably are more concerned with protein than with the traditional milk fat content differences. Because the trait for milk protein content is inherited, cows and bulls can be selected for these differences.
New cow strains with higher protein content are possible if that's what the consumer wants.
If food taste preference research can be believed, consumers prefer milk with a higher protein content. Market trends, however, show only that the consumer is interested in less milk fat, not in more protein. All-Jersey and Golden Guernsey are two such examples, but they lost market share. Increasing milk consumption is of primary interest to dairy farmers, who receive a higher income when milk is used as fluid milk. They receive less money for milk that goes into manufacturing cheese, yogurt and powder.