A nutrient is defined as any substance that provides nourishment for the growth and maintenance of life. Nutrients are classified in several ways. First consider whether they are needed in large amounts, called macronutrients (protein, fats, and carbohydrates) or whether they are needed in small amounts, called micronutrients (vitamins and minerals). Nutrients are further classified based on whether they are essential or nonessential. Essential nutrients are things that the animal or human cannot make at all, or cannot make in sufficient quantities to sustain life. They are essential because the nutrients must be obtained through the diet. A non-essential nutrient is a nutrient that the animal or human can make in sufficient quantities. For example, the microbial population in a horse’s digestive system produces B-vitamins through the fermentation of dietary fiber. Therefore, B-vitamins are considered a non-essential nutrient in the horse.
Every living thing has nutrient requirements which are the amount of each nutrient needed to sustain life. These requirements are hugely variable and depend on species, size, purpose, workload, age, and so on. The nutrient requirements for livestock are published by species through the National Research Council and nutrient requirements for humans are published by the World Health Organization. All living things require six essential nutrients to sustain life. Those nutrients are water, protein, carbohydrates, fats, vitamins, and minerals.
Water is an essential nutrient responsible for dissolving and transporting nutrients, chemical reactions, body fluid levels, temperature regulation, and cell shape. Water requirements tend to vary greatly between individuals.
Two of our essential nutrients provide primarily energy (calories) to the diet. These are carbohydrates and fats. Carbohydrates include simple sugars like glucose, complex sugars like glycogen, starches, and structural or fiber carbohydrates. The second nutrient that provides energy in a diet is fat, which provides 2.25 more energy to the diet than an equal amount of carbohydrates. Fats are digested into essential fatty acids (including Omega 3 and 6) that can be used for energy and also carry fat-soluble vitamins.
The final macronutrient on our list is protein, which is required for the growth and maintenance of the body including muscles, hair, skin, enzymes, and more. Contrary to what some believe, protein is not used as an energy source. Proteins provide amino acids that are used to build things like hormones, antibodies, muscle fiber, and so on.
Our two micronutrients, vitamins and minerals, are organic and inorganic compounds, respectively, that are essential for things like body structure and maintenance, chemical processes, muscle function, immune function, reproduction, and so on. Within these, there are fat-soluble vitamins A, D, E, and K, and also water-soluble vitamins C and B-complex. A primary difference in the two is that fat-soluble vitamins accumulate in the body and can eventually become toxic, while water-soluble vitamins are excreted in excess. On the flip side, we break minerals down into macrominerals including calcium, chloride, phosphorus, sodium, etc and microminerals like chromium, selenium, iron, copper, etc. Mineral deficiencies or toxicities can show up as a wide variety of symptoms and should be evaluated with a medical professional or veterinarian.
Our focus in the Lincoln County Extension Office is on livestock production and management, and my personal specialty and background is in livestock nutrition and ration balancing. If you need help evaluating a diet or connecting to some human nutrition resources, please reach out to us and let us know at uge3181@uga.edu or 706-359-3233.
