title: Effects of minerals on feed degradation and protein synthesis by rumen micro-organisms in a dual effluent fermenter.
abstract: In dual outflow continuous fermenters on a 75:25 hay/barley diet, feed degradation and protein synthesis by mixed rumen microbes were tested in relation to the concentrations of HPO4(2-), HCO3- and Cl- and Na+/K+ ratio in artificial saliva, by applying a 16-run Franquart design, and by fitting second-order polynomial models. The HPO4(2-), HCO3-, Cl- concentrations and Na+/K+ ratio ranged from 0.1 to 4 g.L-1, from 0.5 to 7 g.L-1, from 0.1 to 0.5 g.L-1 and from 0.5 to 15 g.g-1, respectively. Buffer salts, particularly HPO4(2-), were the major factors while Cl- concentration had negligible effects on microbial metabolism. Maximal neutral detergent fibre, acid detergent fibre and organic matter degradabilities occurred at intermediate values of HPO4(2-) and HCO3- concentrations. The outflow of microbial protein and the efficiency of microbial protein synthesis, which varied from 26.2 to 37.1 g.N.kg-1 of organic matter truly degraded, reached minima at the centre of the experimental domain.
mesh_terms: D000821:Animal Feed; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D019149:Bioreactors; D002712:Chlorides / Q000494:pharmacology; D005285:Fermentation; D008903:Minerals / Q000494:pharmacology*; D010710:Phosphates / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D014176:Protein Biosynthesis; D012044:Regression Analysis; D012417:Rumen / Q000382:microbiology*; D012463:Saliva / Q000737:chemistry; D012964:Sodium / Q000494:pharmacology