Dynamics of the solid and liquid phases in the gastrointestinal tract of dairy cows in tropical forage

Abstract

The objectives of this study was to evaluate the effects of different amounts of concentrate, three (SU1) and six (SU2) kg of concentrate, on the dynamics of the solid and liquid phases in lactating Holland cows handled in fertilized Coastcross forage. For the determination of the parameters of the particle kinetics in the gastrointestinal tract, the models of Grovum e Willians (1973) and Dhanoa et al. (1985) were used, checking which provided the best predicted values of chromium excretion in the faeces and for the parameters of the solid-phase kinetics, biologically acceptable, in face of the experimental diets. The Coastcross handled in intermittent foraging, with lots of five animal units (UA)/ha had on average 11.7% PB, 70.2% FDN, 35.2% FDA and 63.8% of DIVMS. The different amounts of concentrate provided a mean dietary ingestion of 13.6% and 14.6% of MS, having nutrient percentages in the MS of the diet of 13.6% and 15.2% PB, 2.6% and 3.2% EE and FDN of 64.0% and 59.0%, respectively. The parameters of the flux kinetics of particles in the gastrointestinal tract were not altered by the different amounts of concentrate. The model of Dhanoa et al. (1985) was more effective in the determination of the parameters related to the rate of flux. The evaluated parameters for the liquid-phase kinetics were not influenced by the greater ingestion of concentrate.