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Introduction

For the remainder of the quarter, we are going to cover species and for each specie we will do ration formulation. Now although most ration formulation today is done on the computer, it is important to know how to do a few simple hand calculations. Nutrients are always, or almost always, quoted on a dry-matter basis. If you look in the back of your book, you will find nutrient composition tables. These are on both an as-fed and a dry-matter basis. As-fed is also known as air dry basis. It is pretty easy to understand as-fed because this is the form in which we offer feed to animals. For cattle, sheep and horses, we always express nutrients on a dry-matter basis. This can be found on pages 502-509. For some species, such as poultry and swine, we express their nutrient concentrations on an as-fed basis or air dry because, in general, these species consume diets that are 90% or greater in dry-matter. So exactly what is dry-matter? Dry-matter is the portion of a feedstuff that contains the nutrients that we are interested in balancing for or formulating a ration for. So exactly what nutrients are we interested in? Well, in general, all but water. Now we know that water is a very essential nutrient, maybe the most essential nutrient. But we always assume that animals are offered water free-choice and we are not feeding a feedstuff to meet the water requirement of an animal. Now dry-matter is particularly important in balancing rations for ruminants and horses because these animals typically consume feeds high in moisture, such as grass pasture, corn silage, grass silage and so forth.

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