A combination of performance potential and feed intake influences nutrient needs. To satisfy the needs at each stage of production, the nutrient content in the diet is modified based on feed consumption. Nutrient requirements are also influenced by environmental factors such as temperature and humidity, which affect digestion and absorption. For example, hens that can eat more tend to have lower requirements for nutrients that are dependent on absorption into the bloodstream like calcium and phosphorus. On the other hand, they need more nutrients that are primarily used for body maintenance such as magnesium and potassium. Hens that eat less need more of these types of nutrients in their diets. Also, the type of protein in the hen's diet may influence her requirement for certain amino acids. For example, hens that produce eggs with high quality proteins such as albumin require more lysine than hens that produce low-quality proteins such as shell. Finally, the level of activity a hen performs daily affects her requirement for some nutrients. Hens that walk around much of the day use up more energy (calories) than resting hens, so they need more food energy and therefore more protein, fat, and mineral nutrients. Hens that roam more extensively also have higher requirements for some vitamins like A, D, E, and K.