Answer to Question 1
Energy-yielding nutrients are supplied as lactose and triacylglycerols. Amino acids, vitamins, and minerals help to facilitate growth. Nutrients also help a newborn maintain body heat.
Answer to Question 2
Animals at different phases of life need different nutrients for their different bodily needs. Animals that are on milk need highly digestible nutrients. Early growth requires extra amino acids, vitamins and minerals, and energy to support organ mass accretion. Adult animals need less, but will vary based on activity levels. Pregnant and lactating animals need an increased intake of the same balanced feed, and in some cases increased intake of foods with increased nutrient density.