Species Variability

Milk fat is the most variable component of milk. It ranges from a little over 1% to greater than 50 %. Aquatic mammals typically have high milk fat percentage.

Lactose ranges from only a trace to less than 7%. Some species have very little lactose in milk, such as the bear and kangaroo. These must have some other osmole in order to maintain milk in osmotic balance with blood plasma as milk is being synthesized. These species often have another sugar (for example the kangaroo has a trisaccharide) as the major osmole.

Milk protein concentration varies considerably, but not as much as milk fat varies among species. Ranges from 1% to about 14%. Generally milk protein percentage is positively correlated with milk fat percentage. If one is high, the other is usually high.