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Biomedical subjects

P N Hobson

Publications and source records attributed to P N Hobson.

At least 19 recordsLinked to original sources
PubMed1982

Microbial ecology and activities in the rumen: part 1.

This review describes the progress which has been made during the last 10 to 15 years in the field of rumen microbiology. It is basically an account of new discoveries in the bacteriology, protozoology, biochemistry, and ecology of the rumen microbial population. As such it covers a wide range of subjects including the isolation and properties of methanogenic bacteria, the role of rumen phycomycete fungi, anaerobic energy conservation, and general metabolic aspects of rumen microorganisms. It also attempts, however, to describe and develop new concepts in rumen microbiology. These consist principally of interactions of the microbemicrobe, microbe-food and microbe-host types, and represent the main areas of recent advance in our understanding of the rumen ecosystem. The development of experimental techniques such as chemostat culture and scanning electron microscopy are shown to have been instrumental in progress in these areas. The paper is concluded with an assessment of our present knowledge of the rumen fermentation, based on the degree of success of experiments with gnotobiotic ruminants inoculated with defined flora and in mathematical modeling of the fermentation. The efficacy of chemical manipulation of the fermentation in ruminant is also discussed in this light.

Amino Acids↗
PubMed1981

Growth and rumen function of gnotobiotic lambs fed on starchy diets.

Four gnotobiotic lambs were fed, after weaning, on a pelleted concentrate diet containing 90% barley. They were inoculated with a defined flora of 11 species of bacteria designed to reproduce the feed digestion of the conventional lamb. Cultural assessments of the growth of the bacteria and analysis of rumen fermentation products showed that rumen function was near normal, and the lambs grew steadily. However, at an age of about 115 to 130 d, rumen function seemed to fail in three of the lambs and they rapidly lost weight and died. The fourth lamb was removed from isolation at about the same time, when there was some slight indication of loss of rumen function. Kept among conventional lambs it then continued to gain weight as did the conventional animals, but its rumen flora changed. The main species in the defined flora remained as major components of the rumen population after the lamb had been exposed to other animals, but in addition a mixed population of other bacteria, like that in conventional animals, quickly developed. Other experiments showed that gnotobiotic lambs could be routinely weaned on to a concentrate feed containing 45% barley and 50% grass and that, when the lambs were inoculated with a defined flora similar to that given to the lambs in the first experiment, an adequate rumen fermentation could be established and the animals would grow. On changing to an all-grass feed, however, rumen function declined and the lambs ceased to grow. A change back to the barley/grass diet restored rumen fermentation and lamb growth, but whereas amylolytic bacteria were present in normal numbers, cellulolytic bacteria were absent and there appeared to be little, if any, fibre digestion. However, the rumen function again appeared to fail at about the same age of lamb as in the first experiment.

Animal Feed↗
PubMed1976

Rumen micro-organisms in red deer, hill sheep and reindeer in the scottish highlands.

The micro-organisms in rumen samples from Red deer, hill sheep and reindeer grazing their natural pastures in the Scottish Highlands were examined at different seasons over a number of years. The total counts of bacteria and protozoa varied with the seasons, and were lowest in winter when fermentative activity was also at its lowest. As is usual in roughage-fed ruminants, viable counts were only a very small proportion of the total counts. The reindeer rumens had the highest concentrations of bacteria. There were no consistent differences in the types of bacteria between seasons, but although there were no bacteria peculiar to any animal species the balance of predominant types varied between the species. The principal types of bacteria were similar to those found in domesticated ruminants. The numbers of protozoa in the Red deer were higher than those in the sheep, and the concentrations in reindeer were higher than those generally reported for domesticated cattle or sheep. A number of species of protozoa were found in each animal and the predominant species differed in the different animals.

Animals↗
PubMed1976

Rumen function in red deer, hill sheep and reindeer in the scottish highlands.

Red deer, sheep and reindeer grazing on their normal hill ranges were examined at intervals over a period of four years. Samples from the digestive tract were taken at different seasons and processed in the field. The Red deer and reindeer were killed before samples were taken; rumen samples from the sheep were taken by stomach tube, but a number of animals were also killed at different seasons to correlate stomach tube and whole rumen samples. The animals sampled were representative of the general condition of the herds. Examinations were made for parasites and any pathological conditions. In most instances parasitic infections were slight. Apparent seasonal changes were found in the compositions of the diets. The Red deer and sheep ate principally heather and grass, the proportion of heather increasing in the winter. The reindeer ate mainly grass in the summer, with lichens and grass forming the winter diet, and these animals seemed to have a higher nutritional status in the winter than did the other two species. The weights of the animals and of their rumen contents, the concentrations of rumen ammonia and volatile fatty acid, and the rates at which different dietary components were fermented are recorded. Rumen fermentation was low in winter and the diets were generally inadequate for the animals. A lack of nitrogen seemed to be a major factor. Some data on caecal contents are also given.

Ammonia↗
PubMed1976

Defined bacterial populations in the rumens of gnotobiotic lambs.

Five gnotobiotic lambs were fed on sterile diets until they were killed at 13 to 21 weeks of age. They were dosed orally with different combinations of 11 species of rumen bacteria. The biochemical reactions of each of the bacteria inoculated had been determined in pure culture in vitro, and they were chosen to perform the main reactions known to be associated with digestion in the normal mature rumen. Two of the bacteria could not be reisolated, but the remainder had established readily in the rumen, forming stable, mixed, defined populations. The total numbers of bacteria in the rumen, and the viable counts of most of the individual species were comparable to those of normal sheep. The concentration of volatile fatty acids was lower, however, and in four of the lambs there was a higher proportion of butyric acid and a lower proportion of propionic acid than in normal sheep. Cellulolytic, ureolytic, and methanogenic activities appeared to be taking place and lactate-utilizing bacteria appeared to reverse the accumulation of lactate which resulted from the activity of lactate-producing bacteria. Some of the bacteria also established at high levels in the caecum.

Acetates↗