O uso de monensina sódica e probióticos para o controle de acidose ruminal subaguda em ovinos

O objetivo deste trabalho foi validar um protocolo para a indução de acidose ruminal subaguda (SARA) (Experimento 1) e testar a eficácia do probiótico Saccharomyces cerevisiae ou monensina na prevenção da queda do pH do fluido ruminal em ovinos (Experimento 2). No Experimento 1, seis ovelhas foram mantidas em jejum por dois dias e, em seguida, alimentadas basicamente com concentrado durante quatro dias. Nesse protocolo as ovelhas mantiveram o pH do fluido ruminal abaixo de 6,0 por 75 horas consecutivas. No Experimento 2, 18 ovelhas foram distribuídas em três grupos: controle (GC, n = 6), monensina (GM, n = 6) e o grupo probiótico (GP, n = 6). SARA foi induzida de acordo com o Experimento 1. PG apresentaram valores de pH mais baixos (5,7 ± 0,1) do que o GC (6,0 ± 0,1) (P = 0,05), enquanto GM (5,7 ± 0,1) foi semelhante durante a indução de SARA. A indução SARA reduziu a população de protozoários no rúmen (P < 0,05) e aumentou a concentração de cloreto no líquido ruminal (P < 0,01). Durante a SARA observou-se aumento das concentrações séricas de fósforo (P < 0,01), AST (P < 0,01) e GGT (P < 0,01), mas reduziu a de LDH (P < 0,01). Em conclusão, o protocolo utilizado para a indução de SARA foi capaz de manter o pH do rúmen entre 5,5-6,0 por períodos superiores a 48 horas. No entanto, a suplementação com monensina e probióticos não foi eficaz na prevenção das alterações nos parâmetros ruminais e séricos durante SARA.The aim of this work was to validate a protocol for induction of subacute ruminal acidosis (SARA) (Experiment 1) and test the efficiency of probiotic Saccharomyces cerevisiae or monensin to avoid pH ruminal drops in sheep (Experiment 2). In Experiment 1, six ewes were fasted for two days and then fed most with concentrate during four days. Ewes in this protocol had ruminal fluid pH below 6.0 and kept it for 75 consecutive hours. In Experiment 2, 18 sheep were distributed into three groups: Control (CG, n = 6), monensin (MG, n = 6) and probiotic group (PG, n = 6). SARA was induced according Experiment 1. PG had lower pH (5.7 ± 0.1) than CG (6.0 ± 0.1) (P = 0.05), while MG (5.7 ± 0.1) was similar to both during SARA induction. SARA induction reduced ruminal protozoa population (P < 0.05) and increased chloride concentrations in ruminal fluid (P < 0.01). In serum, SARA increased concentrations of phosphorus (P < 0.01), AST (P < 0.01) and GGT (P < 0.01), but reduced LDH (P < 0.01). In conclusion, the protocol used for SARA induction was able to maintain ruminal pH between 5.5-6.0 for more than 48 hours. However, monensin and probiotics supplementation was not effective in preventing changes in ruminal and serum parameters during SARA

Effects of epibiosis on consumer-prey interactions

In many benthic communities predators play a crucial role in the population dynamics of their prey. Surface characteristics of the prey are important for recognition and handling by the predator. Because the establishment of an epibiotic assemblage on the surface of a basibiont species creates a new interface between the epibiotized organism and its environment, we hypothesised that epibiosis should have an impact on consumer-prey interactions. In separate investigations, we assessed how epibionts on macroalgae affected the susceptibility of the latter to herbivory by the urchin Arbacia punctulata and how epibionts on the blue mussel Mytilus edulis affected its susceptibility to predation by the shore crab Carcinus maenas. Some epibionts strongly affected consumer feeding behavior. When epibionts were more attractive than their host, consumer pressure increased. When epibionts were less attractive than their host or when they were repellent, consumer pressure decreased. In systems that are controlled from the top-down, epibiosis can strongly influence community dynamics. For the Carcinus/Mytilus system that we studied, the insitu distribution of epibionts on mussels reflected the epibiosis-determined preferences of the predator. Both direct and indirect effects are involved in determining these epibiont-prey-consumer interactions

The Bacterial Symbiont Wolbachia Induces Resistance to RNA Viral Infections in Drosophila melanogaster

Wolbachia are vertically transmitted, obligatory intracellular bacteria that infect a great number of species of arthropods and nematodes. In insects, they are mainly known for disrupting the reproductive biology of their hosts in order to increase their transmission through the female germline. In Drosophila melanogaster, however, a strong and consistent effect of Wolbachia infection has not been found. Here we report that a bacterial infection renders D. melanogaster more resistant to Drosophila C virus, reducing the load of viruses in infected flies. We identify these resistance-inducing bacteria as Wolbachia. Furthermore, we show that Wolbachia also increases resistance of Drosophila to two other RNA virus infections (Nora virus and Flock House virus) but not to a DNA virus infection (Insect Iridescent Virus 6). These results identify a new major factor regulating D. melanogaster resistance to infection by RNA viruses and contribute to the idea that the response of a host to a particular pathogen also depends on its interactions with other microorganisms. This is also, to our knowledge, the first report of a strong beneficial effect of Wolbachia infection in D. melanogaster. The induced resistance to natural viral pathogens may explain Wolbachia prevalence in natural populations and represents a novel Wolbachia–host interaction

Cutaneous Bacteria of the Redback Salamander Prevent Morbidity Associated with a Lethal Disease

Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an infectious disease that causes population declines of many amphibians. Cutaneous bacteria isolated from redback salamanders, Plethodon cinereus, and mountain yellow-legged frogs, Rana muscosa, inhibit the growth of Bd in vitro. In this study, the bacterial community present on the skin of P. cinereus individuals was investigated to determine if it provides protection to salamanders from the lethal and sub-lethal effects of chytridiomycosis. When the cutaneous bacterial community was reduced prior to Bd exposure, salamanders experienced a significantly greater decrease in body mass, which is a symptom of the disease, when compared to infected individuals with a normal bacterial community. In addition, a greater proportion of infected individuals with a reduced bacterial community experienced limb-lifting, a behavior seen only in infected individuals. Overall, these results demonstrate that the cutaneous bacterial community of P. cinereus provides protection to the salamander from Bd and that alteration of this community can change disease resistance. Therefore, symbiotic microbes associated with this species appear to be an important component of its innate skin defenses