Omasal flow and ruminal kinetics in dairy cows fed diets with different levels of insoluble indigestible Neutral Detergent Fiber (iNDF)

Abstract

It is extremely important to know the carbohydrates used in feeding dairy cows and their effects on productive performance; insoluble neutral detergent fiber (NDF) is required in the composition of the diet and makes up a large part of the roughage proportion and has the potential to fill the rumen and limit dry matter intake. Furthermore, the indigestible fraction of NDF (iNDF) is characterized as an NDF residue during a specific fermentation time, and this indigestible fraction comprises cellulose, hemicellulose that are linked to lignin, which prevents its degradation regardless of the time it remains in the rumen; influencing fiber effectiveness, intestinal filling, digestion dynamics and forage passage rate. Some studies manipulating different heights of cuts in the corn plant for silage with the objective of evaluating the changes of NDF forage in the diet of dairy cows observed effects on fermentation and ruminal metabolism, improvement in starch digestibility, attenuation of the effects on fiber degradation due to to changes in the rumen retention time of feed. Despite these effects found in the literature, changing the cutting height for corn silage in an attempt to manipulate the forage iNDF content that will be offered to dairy cows has not yet been well investigated. Therefore, the present study aims to evaluate increasing levels of iNDF in the diet of dairy cows and their effects on nutrient intake and digestibility, ruminal fermentation, ruminal kinetics and relative population of ruminal bacteria, omasal flow, sorting index, feeding behavior, milk yield and composition, excretion of purine derivatives and nitrogen balance. (AU)