Poder germinativo de sementes de capim-annoni-2 (Eragrostis plana Ness) recuperadas em fezes de bovinos

Abstract

RESUMO -Objetivou-se com este trabalho avaliar o efeito do processo de digestão de bovinos sobre o poder germinativo de sementes de capim-annoni-2 (Eragrostis plana Ness) recuperadas nas fezes. As sementes (6 g, 27.273 sementes) foram colocadas no saco ventral do rúmem de oito novilhos fistulados, mantidos em gaiolas para ensaios metabólicos. Quarenta e três por cento das sementes fornecidas aos animais foram recuperadas nas fezes: aquelas recuperadas nos três primeiros dias corresponderam a 97,2% da quantidade de sementes fornecidas. Somente 7,2% das sementes recuperadas, equivalente a 3,1% da quantidade de sementes fornecidas, apresentaram viabilidade. O tempo de permanência no trato digestivo foi a principal causa do desaparecimento das sementes consumidas e da perda de seu poder germinativo. A ausência de sementes de capim-annoni-2 nas fezes ocorre a partir do oitavo dia após a ingestão, assim, bovinos devem permanecer em quarentena por sete dias em área livre de capim-annoni-2 para limpeza do trato digestivo.Palavras-chave: campo natural, dispersão de invasoras, ingestão de sementes, invasão biológica, transporte de sementes Germination of capim-annoni-2 (Eragrostis plana Ness) seeds recovered in bovine fecesABSTRACT -This work was carried out with the objective of evaluating the effect of the bovine digestion process on the germination capacity of the capim-annoni-2 (Eragrostis plana Ness) seeds recovered in feces. The seeds (6 g, 27,273 seeds) were placed in a ruminal ventral sack of eight fistulated steers kept in pen trial. Forthy-three percent of the offered seeds were recovered in the feces. Seeds recovered in the first three days corresponded to 97.2% of the offered seeds. Only 7.2% of the recovered seeds germinated and represented 3.1% of the offered seeds. The permanence time in the digestive trait was the main cause for the disappearance of consumed seeds and for the loss in their germination capacity. The absence of capim-annoni-2 seeds in the feces occurs in the eighth day after ingestion, then, bovines should be kept in quarantine for seven days in an area free of capim-annoni-2 seeds to clean their digestive trait.

Prevention of natural grassland invasion by Eragrostis plana Nees using ecological management practices

“…This fact occurred due to the effect of the initial level of intense soil disturbance (low native pasture + soil scarification) that, in conditions of available resources, favored the recruitment and growth of the South African lovegrass. This higher forage dry mass of South African lovegrass can also be explained by its type of growth habit (tussock) associated with its animal rejection due to its high percentage of lignin (10%) and neutral detergent fiber (80%) (Medeiros et al, 2009). The forage dry mass of dead + senescent material bound to the plants (FDMDS) and total forage dry mass (FDMT) were higher in the exclusion management regime, intermediate in the rotational grazing regime and lower in the continuous grazing regime.…”

“…The invasion occurs according to many factors such as climatic regions, disturbance regimes, presence of herbivores and the fluctuation of available resources like water, light, and nutrients in the plant community. In the case of the natural grassland of Rio Grande do Sul, invasion is facilitated by the high frequency of soil gaps, originated by the continuous grazing system (Medeiros et al, 2009). On the gaps, nutrients, water and light available offer favorable conditions for recruitment of endemic plants and allochthonous based on the soil seed bank (Davis et al, 2000).…”

“…It is believed that these factors are the main causes of invasion of South African lovegrass in the natural grassland in Rio Grande do Sul (Medeiros & Focht, 2007). Its expansion results from the ingestive behavior of animals under continuous grazing, which, in the best period of growing pasture (Spring), prefer to ingest the native prostrate species with higher nutritional value rather than South African lovegrass (Medeiros et al, 2009). In this condition of selective grazing, the South African lovegrass grows in low competition, producing intense flow of panicles from November to March.…”

“…In this condition of selective grazing, the South African lovegrass grows in low competition, producing intense flow of panicles from November to March. Under these conditions, when forage quality starts to diminish in the Summer, the animals attempt to compensate their diet by ingesting South African lovegrass (Medeiros et al, 2009), preferring the panicles, the most palatable part of the adult plant (Reis, 1993). One fraction of the seeds produced falls off the panicle and accumulates in the soil seed bank.…”

“…One fraction of the seeds produced falls off the panicle and accumulates in the soil seed bank. The animals ingest another seed fraction, along with the panicles, which is distributed locally by the feces or, in the case of animal transport, invades areas in other regions through the seeds preserved, which are viable for up to 3 days in the feces after ingestion (Lisboa et al, 2009).…”