Diversidade populacional de protozoários e cinética ruminal em ovinos mantidos em vegetação de caatinga

Abstract

The objective of this work was to determine the number and genus of ciliate protozoa in the rumen, ruminal fermentation parameters and microbial protein synthesis in sheep raised in the caatinga. The chemical composition of the extrusa, dry matter (CMS), organic matter (CMO), crude protein (CPB), neutral detergent fiber (CFDN) and total digestible nutrients (CNDT), pH, acids Volatile fatty acids, ammonia, estimation of microbial production, renewal time, rate of disappearance of MS, OM and NDF, number and genus of ciliated protozoa of the rumen. The experiment was carried out from September 2004 to July 2005. Ninety castrated Santa Inês sheep were used, with permanent cannulae in the rumen, kept in the caatinga, receiving water and mineral mixture `ad libitum¿. The nutrient intake as a function of live weight and the unit of metabolic size was higher in May 2005, when there was greater forage availability. The mean pH ranged from 7.07 (before feeding) to 6.31 (10 hours post). The mean values ​​for renewal time and disappearance rate did not show a significant difference (P> 0.05) and were 22.56; 22.08 and 21.42 hours and 4.9; 5.0 and 5.1% / h for MS, MO and FDN, respectively. The concentration of volatile fatty acids (VFA) presented diurnal variation with linear behavior (P <0.05) and during the year of study, being lower in the months of May and July of 2005, however the molar proportion remained practically unchanged, and Was on average 75.0: 18.6: 6.4 for acetate, propionate and butyrate, respectively. The concentrations of ammonia presented linear increases (P <0.05) with the collection time, ranging from 10.53 to 18.24 mg of ammonia / 100 mL of ruminal liquid, before and 10 hours after feeding, respectively. The yield and efficiency of microbial protein synthesis were higher than May 2005, when the ammonia concentration in ruminal fluid was higher. Protozoa of the genera Diplodinium, Diploplastron, Elitroplastron, Entodinium, Enoploplastron, Eodinium, Epidinium, Isotricha, Metadinium, Ophryoscolex and Polyplastron, with predominance of the Entodinium genus (around 90%) were found. Of the subclass Holotricha was registered only the genus Isotricha that represented on average 1.94% of the population. The percentage of protozoa only varied (P <0.05) for the genus Eodinium, being higher in May 2005, which can be justified by the high crude protein content (17.82%) and hemicellulose (18.56% ) In this month. This indicates that, although the average and total number of protozoa vary, the population remained stable throughout the year. Regarding the time of collection, only pH, mean Entodinium concentration and total number of protozoa presented a significant difference (P <0.05), being higher at hour zero. The other genera also presented the same behavior, thus reflecting the stability of the ruminal environment for animals without access to nocturnal feeding. The protozoa of the Entodiniomorpha subclass present a high positive correlation (P <0.05) with the level of total digestible nutrients and crude protein of the diet. This reflects the need, by the microorganism, for energy and protein for synthesis (cell division) and storage.