Resistência à moagem e composições morfológica e química dos capins marandu, mavuno, dunamis e camello

Abstract

The objective of this study was to evaluate the chemical composition and resistance to grinding of the grazable extract of Marandu grass and three Urochloa spp. hybrids (Mavuno, Dunamis and Camelo grasses) in spring and summer and to verify if there is a correlation between these characteristics in these forages. For this purpose, samples of the grazable extract (15 cm residue) were collected in twelve plots composed of four forage species: Marandu grass and three Urochloa spp. hybrids (Mavuno, Dunamis and Camelo) in two seasons of the year (spring and summer). The experiment was conducted in a randomized block design (RBD) with plots repeated in time (seasons of the year), with four treatments (grasses) and three replicates (plots). Resistance to grinding was performed according to the method proposed by Hughes et al. (1998). The chemical analyses measured were dry matter (DM), crude protein (CP), neutral detergent insoluble fiber (NDF), acid detergent insoluble fiber (ADF), lignin (LIG), indigestible NDF (iNDF) and in vitro dry matter digestibility (IVDMD). The means obtained were compared using the mean test at a 5% probability level for type I error. Also, the physical analyses (resistance to grinding) were correlated with the chemical analyses using Pearson's correlation. Camello grass had a higher NDF content in the spring and a higher ADF content in the summer than the other grasses. Despite the higher NDF content in Camello grass, it presented a lower iNDF, when expressed as a percentage of NDF, together with Dunamis grass. Dunamis grass had a lower crude protein (CP) content when compared to the other hybrids during the spring, while Camello and Mavuno grasses had higher CP contents. There was no difference between the grasses for the ADF/NDF ratio, as well as for the DMIVD. It was concluded that the grazable extract of Camello grass has a higher concentration of NDF and ADF when compared to the other grasses, in spring and summer, as well as greater presence of live stem and dead stem in its composition, which causes greater resistance to grinding. However, despite the higher fiber content, the material has a low content of iNDF, showing that it´s a fiber with better potential for use by animal. The physical analysis of resistance to grinding shows a correlation with the morphological components of the pasture, as well as with the fiber content, but has a negative correlation with the fiber digestibility parameters.