Objective:

To characterize the agronomic performance and chemical composition of cultivated species in a Voisin rational grazing system, in the humid tropic of Los Santos, Panama.

Materials and Methods:

The yield and nutritional value of a group of cultivated species were evaluated, with 24 paddocks and 1,9 days of average occupation. The system was grazed with 53 Zebu-based steers and their F1 and F2 crossings (Zebu x Holstein). The main indicators measured were: total forage production (kg DM/ha/rotation), forage supply per species and percentages of DM, CP, ADF, NDF, IVDMD30, ME, Ash, Ca and P. The data were processed using simple classification variance analysis. The statistical package IBM® SPSS® Statistics version 22 was used.

Results:

Forage production varied between 3 344 and 4 442 kg DM/ha/rotation. The highest pasture yield was obtained in the rainy season. The best yields (p < 0,001) were obtained in the genus Megathyrsus (cvs. Tanzania and Massai), with offers of 34,9 and 31,9 t DM/ha/year, higher than those of the different Urochloa cvs. Regarding the availability of DM/ha/rotation, the lowest values were achieved in the cultivars Toledo and Humidicola. The quality was higher in the rainy season. The high average DM in the dry season (40,80 %) conditioned low CP values (6,85 %), low energy content (1,57 Mcal/kg), low digestibility (55,7 %) and high contents of NDF (74,2%).

Conclusions:

The average yield and pasture supply of the species were acceptable for the prevailing edaphoclimatic conditions in the ecosystem, since no irrigation or external fertilization was used; although they decreased in the dry season, as well as the nutritional quality. The genus Megathyrsus stood out for its better production indicators; while Arachis pintoi Krapov. & W.C. Greg stood out for its high nutritional value.

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