Variação estacional das populações de protozoários ciliados (Protista, Ciliophora) do rúmen de ovinos (Ovis aries L.) mantidos em pastagens naturais no semi-arido de Pernambuco, Brasil

Abstract

The ciliate protozoan of the rumen are part of the ruminal microbiota, and together with bacteria, fungus and flagellate protozoa, they participate of the fermentative digestion of the ruminants. However, there are controversial aspects about the hole of these microorganisms it the metabolism of the host, in part due to the complexity of the population dynamics, and also to the interrelations between protozoan, the host, and other ruminal microorganisms. The objective of this work was to characterize the ciliate protozoa populations in the rumen of Santa Inez crossbred sheep, verifying the effects of the seasonality and also aspects related to the diurnal changes of these populations. It was used five sheep fistulated in the rumen, maintained in natural pasturage of caatinga (scrubland) vegetation at the state of Pernambuco, Brazil. The samples were collected in july 2005 (rainy season) and january 2006 (dry season). The composition of animals diet was determined through the extrusa analysis. The samples were obtained at intervals of two hours, being the first sample took before the releasing of the animals, in a total of six samples. The samples were fixed in formalin at 18, 5% (v/v). The feed composition of the sheep during the rainy season was predominantly composed of herbaceous species, and at the dry season by species shrub, denoting the effect of the seasonality on the sheep feed habits. It was identified and quantified Dasytricha, Diplodinium, Diploplastron, Entodinium, Eodinium, xviii Elytroplastron, Enoploplastron, Epidinium, Eremoplastron, Eudiplodinium, Isotricha, Metadinium e Ophryoscolex. Eodinium and Enoploplastron genders were observed just at the rainy season. Diplodinium, Elytroplastron, Metadinium and Ophryoscolex didn’t show variations in the population concentration as a function of the season. It was observed the predominance of the gender Entodinium at both seasons; however, at the dry season it was noted significant decrease in the concentration of this gender, and increase in greater ophryoscolecidae and Isotrichidae. The total number of protozoa was significantly reduced during the dry season. Diploplastron and Entodinium showed variations in their populations concentrations, due to the time of sampling. The number ciliates undergoing division was not correlated with the sampling times. Stable division rate appears to contribute to maintenance of ciliates concentrations in the rumen. The ruminal pH was negatively correlated with sampling times, and was not correlated with the number of protozoa, probably because the variations observed included parameters considered ideal for establishment and maintenance protozoa populations of rumen. It was observed predatory behavior of Elytroplastron on Enoploplastron, Epidinium and Entodinium; besides cannibalism between organisms of the Elytroplastron gender. The registration of fiber ingestion and starch granules formation at the cytoplasm indicates cellulolytic and amilollytic activities, attributed to these microorganisms in the ruminal environment.