In Vitro Digestibility of Forages

Forages are a necessary component of diets for lactating dairy cows because they provide coarse fiber needed to optimize rumen function. However, forages alone provide insufficient nutrients to achieve high milk yield, and they must be supplemented with other feed ingredients. Because forage quality is highly variable, their quality must be assessed before diets are formulated. Forages have been traditionally analyzed for crude protein and fiber concentrations because of their direct effect on diet formulation. More recently, in vitro neutral detergent fiber digestibility (IVFD) has been identified as an important quality parameter that is highly variable among forages and has consistent effects on productivity of dairy cows. However, it is important to understand the unique characteristics and limitations of in vitro measurements of forage NDF digestibility to maximize the benefit of enhanced IVFD. This paper will answer some frequently asked questions regarding the interpretation and utilization of IVFD data of forages.