Consequences of kinetics of ruminal degradation on ruminal metabolism and zootechnical performances

Abstract

Research of the last decades have demonstrated that the kinetics of ruminal degradation of feeds vary largely in function of their nature and of the constituent. It can therefore be envisaged to take the opportunity of this variability to formulate compound feeds or mixed diets which are more and less rapidly degraded or more and less synchronized between the carbohydrates and proteins degradation rates in comparison with the microbe requirements.

Experimental data related to the influence of the variations of these phenomena on ruminal digestion and zootechnical performances show that the effects are less important that could be a priori imagined. It is therefore necessary to explain that fact. It seems that numerous structures and phenomena of delay allow to smooth efficiently the dynamic variations of degradation processes between feeds or constituents. Several examples are evoked. For nitrogenous products smoothing phenomena particularly occur by a transient storage of peptides before microbial captation and nitrogenous recycling by protozoa and blood urea recycling. For energy nutrients, it seems that the most important transient storage of energy is in the form of polysaccharidic storage within the microbial cells. The dynamic approach of ruminal digestion also emphasizes that microbial growth rate is limited and less variable in short term, even if sufficient nutrients are available. Some comments and explanations are made on this aspect.