Anotace:
The work evaluates the content of nutrients, rumen digestibility of NDF, degradability of CP, and intestinal digestibility of rumen un-degradable proteins in protein forages and concentrated feeds. The analysis of nutrient content confirmed along with the increase of plant maturity expressed by the increase of NDF, a significant decrease of NFC and CP in the regression dependence R2 = 0.7649 and R2 = 0.7116, respectively. The in situ method after 30 hours of incubation confirmed the higher NDF digestibility (P <0.001) of young roughages. The degradability of CP in alfalfa and grass silages was on average 78.7 ±6.1% or 63.7 ±9.7%. Higher protein degradability was confirmed in early-stage forages compared to mature forages for alfalfa (P <0.05) and grass (P <0.01) silages. Intestinal digestibility of un-degradable proteins determined by the modified three-step method was on average 64.1 ±2.5% in alfalfa silages and 51.0 ±5.6% in grass silages, with a statistically significant decrease (P <0.05) in mature forages. The obtained values of rumen degradability of crude protein confirmed a significant difference (P <0.001) between concentrates ranging from 20.3 to 76.0% (mean 58.1 ±3.0%) according to heat treatment. Intestinal digestibility of un-degraded protein varied from 54.5 ±1.4% in raw soybean to 95.2 ±1.0% in corn gluten feed. This study showed that the digestibility factor of crude protein and intestinal digestibility methods for protein feeds can be used in models to optimize the protein nutrition of dairy cows.