Influence of a Silvopastoral System on Anatomical Aspects and Dry Matter Quality of Mombasa and Marandu Grasses

The goal of this paper was to evaluate the influence of the shading levels in a silvopastoral system on the association of anatomical structures with nutritional parameters and gas production of Poaceae species. Plants of two forage species (Panicum maximum cv. Mombasa and Brachiaria brizantha cv. Marandu) were exposed to three shading levels (full sun, 25 and 50%). The shading was arranged in contiguous bands, and treatments were allocated in a completely randomized design with four replications. Leaf blades were measured for parenchyma thickness (mesophyll), vascular bundle components (metaxylem and metaphloem), vascular bundle sheath, sclerenchymatic sheath, sclerenchymatic cap, sclerenchymatic extension, and epidermis secondary growth. In addition, measures of NDF and ADF contents, gas production, and dry matter degradability at 96 h incubation were also obtained. The results were subjected to t-test at 5% and correlation analysis for each genotype and shading level. The proportion of lignifying tissues such as secondary wall thickening and sclerenchyma was reduced under shading on an average of 66% and 60%, respectively. The proportions of metaphloem in Mombasa and Marandu grasses under the full sun were 5.5% and 3.7%, respectively. However, this response was reversed with shading, reducing the proportion of metaphloem in Mombasa. Gas production in shaded Marandu grasses was higher than was in Mombasa grasses because of the higher proportion of metaphloem. Considering the anatomical traits and gas production for shaded plants, Marandu grass showed the highest dry matter degradability if compared to Mombasa.