The main site of conversion into vitamin A of ingested carotene is the intestinal wall, so that the absence of carotenoids from the tissues of these animals suggests that in them, carotenoids are either not absorbed into the circulation or are rapidly degraded in the tissues into colorless products.
Consequently the latter milks have less color than either Jersey or Guernsey. The minimum maintenance requirement of cattle for carotene is approximately 3.5 mg per 100 kg of body weight.
At least 50 to 75 percent more is needed for normal growth and maintenance of adequate plasma and liver levels.
Carotene in milk