BIOLOGY Volume 1 - A Guide to General Biology - 2004

8. HETEROTROPHIC NUTRITION

8.7. Human Nutrition

8.7.11. Milk

Milk is the sole food received by most mammals During the first weeks of life. It contains virtually the complete set of nutrients required for this developmental stage—CARBOHYDRATES, Proteins, fats, minerals (particularly calcium, magnesium, phosphorus, and potassium), as well as a wide range of Vitamins. The only essential component missing from milk in sufficient quantities is iron, which is a constituent of Blood Hemoglobin. However, this issue is addressed by the fetus itself, which accumulates iron transferred from the mother and stores it in its body until birth. This reserve is sufficient to sustain the infant until it transitions to solid food.

8.9. At the beginning of the 20th century, Frederick Gowland Hopkins of Cambridge conducted a famous experiment in which two groups of young rats (8 rats in each group) were fed a diet consisting of pure casein (milk protein), starch, sucrose, lard, inorganic salts, and Water. One group of rats additionally received 3 ml of milk daily for the first 18 days. On the 18th day, milk was removed from the diet of the first group, but was then given to the rats In the second group. The results of the experiment are shown in Fig. 8.26.

a) What hypothesis could you propose based on the presented graphs?

b) Justify your answer.

c) Why can adults not subsist on milk alone?

Class="center">

Fig. 8.26. Hopkins's experiment on feeding young rats with milk.