Carotene content in cow’s milk

Carotene occurs in the forages consumed by cattle and is the precursor of physiological active vitamin A. The ability to convert carotene into vitamin A before it is secreted into the milk varies with different breeds.

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.

The Guernsey cow (or Jersey) secretes a large proportion of vitamin A as carotene, while other breeds such as Holstein-Friesian and Ayrshire produce a milk low in carotene but equally high in vitamin A on a fat basis.

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 content in cow’s milk

Carotene: precursor of vitamin A

The two primary isomers of carotene are:
*α-Carotene
*β-Carotene

β-Carotene is the more common form. β-Carotene (C40H56) is a fat soluble plant pigment found in red, orange and yellow vegetables and fruits.

β-Carotene is converted to vitamin A (retinal, retinol, retinoic acid), when the body is in short supply. It is an antioxidant – a compound that blocks the action of activated oxygen molecules that can damage cells.

Vitamin A is essential for the human body in that it assists the body’s immune system and helps battle eye disease, such as cataracts and night blindness, various skin ailments such as acne, signs of aging, and various forms of cancer.

Commercially, β-Carotene is used as a safe food coloring. β-Carotene is the most plentiful of the orange-yellow plant pigments in foods, and it has the highest vitamin A activity.

Because of differences in uptake, storage and chemical processing, only about one-sixth of the β-Carotene in a plant food ends up as vitamin A (retinol) in the body.
Carotene: precursor of vitamin A

What is vitamin A?

Vitamin A is a fat soluble vitamin. It is found only in animals, although a number of plants contain carotene, from which vitamin A can be produced in the body once the plants containing carotene are eaten.

Vitamin A may be formed in the body from the yellow pigments (containing carotene) of many fruits and vegetables, especially carrots. Vitamin A is also found in the fats and especially in the liver oils many saltwater fish.

Vitamin A is required for vision. Epithelial cells (those cells present in the lining) of body cavities and in the skin and glands) require vitamin A. This vitamin also required for resistance to infection.

Deficiency of vitamin A may cause impairment in bone formation, impairment of night vision, malfunction of epithelial tissues, and defects in the enamel teeth.
What is vitamin A?