Associações entre parâmetros da cinética de degradação ruminal e os constituintes da parede celular de quatro gramíneas tropicais

The association of digestible and indigestible cell wall contents, the in vitro dry mater digestibility, the digestion rate, lag phase and the relative gas volume produced from neutral detergent fiber potentially digestible were evaluated in tropical grasses samples. The samples were from setaria grass, hemarthria grass, angola grass and acroceres grass fertilized with 0, 100, 200, 300 and 400kg of N/ha and in the cutting ages of 28, 42, 56 and 70 days. The results were submitted to a factor analysis. It was opted for the adoption of three factors comprising 73,81% % of the total variation, where the first factor was strongly associated with the in vitro dry matter digestibility, neutral detergent fiber potentially digestible, lag and with relative gas volume. The second factor was connected to the indigestible neutral detergent fiber and with digestion rate, and the third factor was related to lignin. The neutral potentially digestible detergent fiber showed positive correlation (0.5294) with in vitro dry matter digestibility (P<0.01), for hermarthria grass at 42 days old. This grass showed better results when compared to the other grasses, and it presented higher values for in vitro dry matter digestibility (69.39%) and neutral detergent fiber potentially digestible (57.89%) and smaller production of relative gas volume (0,186mL/mg), that means better fermentation characteristics and utilization of carbon for energy production.