PSXI-19 Production and Nitrogenous compounds of genotypes of dwarfish elephant grass (Pennisetum purpureum, Schum) under rotational grazing.

Abstract

The grasses are the primary source of crude protein for ruminant animals under pasture, therefore the evaluation and the correct characterization of the fractions of its nitrogenous compounds are important to reduce costs, as well as, to make possible to reach higher productive levels. The fractions of the nitrogenous compounds in the leaf blade of genotypes of dwarfish elephant grass submitted to four grazing frequencies were studied. Three genotypes were evaluated in a randomized blocks design in split plot with three replicates. The parcels corresponded to the three genotypes (CNPGL 92198-7, CNPGL 9434-3 and cv Mott), and the sub parcels, to four grazing frequencies: resting time of 30 and 45 days, respectively, the rainy and dry seasons, and resting time until that the forage sward reached 90, 95 and 100% of luminous interception. Cv Mott and the genotype CNPGL 92198-7 showed higher levels of the fraction B1 that corresponds to the soluble proteins and of fast ruminal degradation. For the other nitrogenous fractions, there was no significant difference among genotypes and the cv Mott. The largest averages for the fractions A and B1 were observed in the rainy season. The genotypes with larger height of the forage canopy in the pre grazing were the cv. Mott and the genotype CNPGL 92198-7, while the genotype CNPGL 9434-3 presented the largest tillering rate. The effect of the season of the year on the analyzed variables confirms the behavior sharply seasonal of the dwarfish elephant grass.