However, if efficiency is defined as human edible output divided by human edible input, efficiency is higher. Fundamental nutrients are water, CHO, fat, protein, vitamins and minerals. In general, ingested nutrients are metabolized to meet an animal's energy requirement. This may be supplied by CHO, fat or protein. Minerals and vitamins act as co-factors in metabolic reactions.
Metabolic reactions occur in water.
That is why water is an essential nutrient. Nutritionists combine knowledge in feed contents, animal requirements, physiology and many other factors to manage nutritional needs of livestock.