Determination of the leaf: Stern ratio, protein content and phytochemical prospection of the Arachis pintoi forage peanut

Arachis pintoi, cv. Belmonte is reported by its high crude protein (CP) content, being cultivated on pastures systems. However, forage legumes are related to the presence of secondary metabolites in its constitution related to reduction in its consumption when grazed. For this, samples of forage was collected in an area of planting already established in October 2015, at 3 months of age after the last cut, in the Forage Section of the Instituto de Zootecnia, and sent to the Animal Nutrition and Natural Products Chemistry laboratories, both from Universidade Federal Rural do Rio de Janeiro (UFRRJ). The A. pintoi was sampled in four repetitions of 400 g each, cut 5 cm from soil level and separated into the following parts: whole plant, branches and leaf after weighing were sent to drying ventilation oven at 55 ?C for 72 h, and part of whole plant portion was dried in the shade to prevent evaporation of volatile secondary metabolites. After this step, the plant portions were ground in a Wiley mill using 1 mm sieve screens. The samples dried in greenhouses were determined the crude protein (CP) by the Kjeldahl method. 658.75 g of dry material in the shade were submitted to exhaustive cold maceration with hexane and methanol solvents (both of Vetec mark), the obtained extracts were concentrated in rotary evaporator apparatus, yielding 8.52 g of hexane extract and 50.01 g of methanol extract which were referred to the identification of classes of secondary metabolites in accordance with the methods described in Matos (1988). The A. pintoi presented a leaf:stem ratio 1.23 and crude protein of the portions, whole plant, leaves and branches was 25.52; 15.4 and 14.51%, respectively. Showing the difference between the content found on the legume leaves for the other portions by Tukey test (P = 0.000). Secondary metabolites as steroids, triterpenoids, cumarines, cardiotomic glucosides, saponins and tannins were determined. From these results it might be concluded that A. pintoi cv. Belmonte might be employed on animal nutrition for its CP levels and leaves quantity, as reported in the scientific literature. However, saponins and tannins influence its intake and/or animal performance. Already other classes of metabolites present in the fodder need studies to determine which promotes effect when used in animal feed.