Using dDual-flow continuous culture system to evaluate ruminal fermentation responses to micronutrients supplementation

Abstract

Evaluations of the effects of nutrients on ruminal fermentation have been primarily focused on macronutrients. Concentrations at which micronutrients are commonly fed allow for smaller magnitude impacts on fermentation than other nutrients included at greater concentrations. The dual-flow continuous culture system is a useful model that has been proved to accuratelly simulate ruminal microbial fermentation, allowing to precisely control multiple factors that affect fermentation. The objective of this dissertation was to evaluate the impact of micronutrients on ruminal fermentation using the dual-flow continuous culture as a model. In our first study, shown in Chapter 3, our objective was to evaluate if protection of copper sulfate (CuSO4) and sodium selenite (Na2SeO3 ) by lipid-microencapsulation would alter ruminal microbial fermentation. We concluded that protection of CuSO4 affected VFA synthesis by increasing butyrate molar proportion at the expense of molar proportion of acetate; while Na2SeO3 protection affected N metabolism by tending to reduce microbial degradation of dietary N. Our second study (Chapter 4) aimed to evaluate CaMg(CO3)2 and CaMg(OH)4 alone or in combination as sources of inorganic Mg and their impact on microbial ruminal fermentation. 15 It was concluded that inclusion of CaMg(OH)4 in diets as a source of Mg, either alone or combined with CaMg(CO3)2, allowed for similar microbial fermentation variables and alkalinizing effect than a control diet formulated with MgO plus sodium sesquicarbonate as a buffer. The objectives of our third study (Chapter 5) were to evaluate the effects of unprotected choline chloride on ruminal fermentation, and to investigate if those effects depend on dietary NDF concentration. We concluded that unprotected choline chloride alters ruminal fermentation by increasing synthesis of propionate at the expense of acetogenesis, and that such effects depend on dietary NDF concentration...