Variability in Chemical Composition and Digestibility of Twelve By-Product Feedstuffs Utilized in the California Dairy Industry1

The objective of this descriptive study was to measure the amount of variability in the composition of 12 by-product feedstuffs commonly used in rations for lactating dairy cows in California. This study followed a prior descriptive study that was designed to provide the beginning of a nutrient database of by-product feedstuffs. Eleven of the by-product feedstuffs were from a single manufacturer source, with only soybean samples obtained from multiple sources. Samples of each by-product feedstuff were obtained from various locations in California and several locations outside the state. Variability in chemical composition and digestibility are discussed within each of the by-product feedstuff subgroups. Variation generally tended to be within acceptable ranges, although a wider variability was observed when sample numbers were smaller or the absolute value of the nutrient being measured was low.