Files in this item
|(no description provided)|
|Title:||Diurnal Variation Patterns in the Rumen of Cattle: Studies of Bacterial Numbers, Carbohydrate-Specific Groups and Ruminal Fluid Parameters|
|Author(s):||Leedle, Jane Alice Zeigler|
|Department / Program:||Dairy Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Animal Culture and Nutrition|
|Abstract:||Diurnal variation in the size and composition of mixed rumen bacterial populations in cattle fed either high forage or high concentrate diets (maintenance intake levels) was followed after a once daily feeding. Samples of ruminal contents were collected from rumen-fistulated, Holstein steers at -1, +2, 4, 8, 12 and 16 h after feeding. The bacterial population of each was separated from feed particles, protozoa and ruminal fluid by differential centrifugation. The population was then assessed for total and viable cell counts and bacterial cell constituents. After the viable bacterial count was determined, the colonies were replica plated onto an array of differential media. These media were previously shown to separate the rumen bacterial population into groups on the basis of carbohydrate substrate utilization specificities. Colonies which developed on these media represented the major carbohydrate metabolizing groups comprising the bacterial population at the time of sampling. Fermentation acids, carbohydrate and ammonia levels were also determined in the corresponding ruminal fluid samples and the pH levels were measured.
Results showed that total bacterial numbers remained fairly constant throughout the diurnal period regardless of the diet fed. However, the number of viable bacteria decreased rapidly after feeding reaching its lowest level at 2 or 4 h post-feeding. Thereafter the viable population increased gradually, reaching its highest number at 16 h post-feeding. Changes in the major carbohydrate metabolizing groups within the bacterial population were, in general, not related to the theoretical pattern of ruminal fermentation for the primary carbohydrate components (soluble sugars, starch, pectin, hemicellulose and cellulose) in the diets fed. The most striking observation was that the soluble carbohydrate utilizing bacteria predominated at all times in both diets. Xylan and pectin degrading bacteria comprised about one half and one third of the population, respectively (slightly less on the high concentrate diet). These groups reached maximum representation between 8 and 12 h post-feeding. The cellulolytic bacteria represented the least numerous group of those tested and peaked in population density at 16 h post-feeding. Bacterial cell constituents calculated on a dry weight basis were as expected for a predominantly Gram negative bacterial population. Fermentation acids, pH profiles and carbohydrate and ammonia concentrations in the ruminal fluid did not change substantially over the diurnal period monitored and were within normal ranges for these parameters for both diets.
Results of these studies were largely unexpected. Of particular interest was the apparent lack of difference between the bacterial flora composition of steers consuming high forage or high concentrate diets (75%/25%; metabolizable energy basis). Previous experiments by the author had revealed substantial differences between bacterial carbohydrate metabolizing group composition when animals were fed corn and corn silage (85%/15%) or alfalfa hay and concentrate mix (70%/30%) at 1.25 times maintenance. These latter diets, however, were calculated on a dry matter basis and thus contained different levels of caloric nutrients. In the diurnal studies, both diets provided the ruminal studies, both diets provided the ruminal microorganisms equivalent nutrients varying only with respect to the form of the predominant caloric materials. Consequently, both diets resulted in ruminal fermentation acid productions which apparently did not surpass the ruminal buffering capacity provided by the saliva and blood. These data suggest that normal ruminal function was not disturbed simply by the type of diet fed. The data also imply that pH, which remained between 6 and 7 during most of the diurnal period, is a primary factor governing the size and composition of the rumen microbial population.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2014-12-16|