Nutritional values and chemical composition of tropical pastures as potential sources of α-tocopherol and condensed tannin

Abstract

Tropical pastures can be important natural sources of antioxidant compounds and may impact production and quality of animal protein with repercussions on human health. The objective of this study was to evaluate the concentrations of α-tocopherol, condensed tannin (CT) and nutritional values of important tropical species used in grazing. The species included guinea grass (Panicum maximum), bermudagrass (Cynodon spp.), pigeon pea (Cajanus cajan), soybean (Glycine max), creeping beggarweed (Desmodium incanum), macrocephala stylo (Stylosanthes macrocephala) and pinto rhizoma peanut (Arachis pintoii). The species were distributed in a randomised block design with four replicates each. There were no differences in α-tocopherol between the mid and late growing season; there were likewise no differences among forage species. The highest (P = 0.02) concentrations of CT were observed in creeping beggarweed (66.5 ± 13.8 g kg⁻¹ dry matter [DM]), pinto (15.7 ± 5.2 g kg⁻¹ DM) and pigeon pea (8.7 ± 0.8 g kg⁻¹ DM). Among these species, creeping beggarweed showed the highest percentage of extractable CTs (68% of total CT) and was the only species where the CT showed biological activity (protein precipitation by phenols = 60.1 g kg⁻¹ DM). Among the tropical grasses and legumes, creeping beggarweed could become an important CT source for animal production.