Ever wonder why animals and humans need to eat?
Nutrients are needed to maintain normal body function. These nutrients can be broken into 6 major classes:
These nutrients, which are essential for life, are obtained through the diet. Animal nutritionists formulate diets by blending ingredients together in such a way that all nutritional needs are met. They do this while trying to keep the cost of the diet low and while trying to minimize any excess nutrients in the diets, which can lead to increased nutrient excretion.
How do nutritionists know what minerals animals require?
Animal Scientists study nutrient requirements by investigating how including different amounts of each nutrient in the diet affects animal performance parameters like growth rate, feed intake and feed efficiency (how much weight does the animal gain per pound of feed consumed). They investigate, not just how fast they gain weight, but what is the composition of that gain. How much is muscle? How much is fat? How much is bone? They also investigate things like nutrient pools in the body. Minerals are a good example of this. Some nutrients are stored in bone or in the liver. Others are excreted in the urine if fed in excess, while absorption efficiency may diminish when others are fed in excess. They may also investigate any effects on animal health, immunity, general metabolism, etc. Ultimately, a group of scientists gets together every few years to review mineral requirements and puts the findings together in a publication. You might think that nutrient requirements shouldn't change over time, but they do because the animals change, the feed ingredients change, and our understanding of nutrient requirements continues to evolve. If we use pigs as an example, today's pigs eat less per day than their predecessors, but they gain more weight per day, and overall they are much leaner. Therefore, the diet for a pig today needs to be more nutrient dense.
Nutrient requirements for almost all species are published by National Research Council (NRC). Links are included below:
Nutrient Requirements of Horses
Nutrient Requirements of Swine
Nutrient Requirements of Dairy Cattle
Nutrient Requirements of Beef Cattle
Nutrient Requirement of Dogs and Cats
Nutrient Requirements of Poultry
Nutrient Requirements of Small Ruminants