Influence of major minerals on rumen microbiota.

The supply of minerals needed to meet rumen microbe requirements should match the amount of energy available for fermentation. Therefore, we attempt to assess microbial requirements for phosphorus (P), sulfur (S) and magnesium (Mg) in terms of fermentable organic matter at the rumen level (OMF) or in terms of digestible matter in the total tract (OMD). In vivo, about 5 g of P and 1.

Effect of different levels of phosphorus on rumen microbial fermentation and synthesis determined using a continuous culture technique.

A continuous culture technique was used to study the phosphorus requirements of rumen micro-organisms. Solutions of artificial saliva containing 120, 80, 40 and 0 mg inorganic phosphorus (Pi)/l were infused into the reaction vessels previously inoculated with rumen contents, resulting in Pi concentrations in the vessel contents of 48, 28, 4 and less than 1 mg/l respectively. Various fermentative and synthetic characteristics were examined.

Effects of phosphorus deficiency on rumen microbial activity associated with the solid and liquid phases of a fermentor (Rusitec).

The rumen simulation technique (Rusitec) has been used to study the effects of phosphorus (P) deficiency on bacterial protein synthesis and chemical composition and on adenosine triphosphate (ATP) concentrations in the solid and liquid phases of fermentors. 16 g DM of a P-deficient mixed diet was put into each vessel daily and the vessels were infused with about 1 l of a P-deficient (0 mg of P) or P-supplemented (120 mg of P/l) buffer. Two vessels per treatment were used, and during a second experimental period the deficient and supplemented buffers were interchanged to determine the effects of P repletion and depletion.