Factors Affecting Efficiency of Net Ruminal Microbial Protein Synthesis in Cattle PDF Download

Author: Michael John Cecava
Publisher:
ISBN:
Category :
Languages : en
Pages : 238

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Book Description
Two experiments were conducted to examine factors that affect nutrient digestion and microbial protein synthesis in cattle. In the first study, four cannulated (rumen, proximal duodenum, terminal ileum) steers were used in a 4 $times$ 4 Latin square design experiment. Steers were fed corn/corn silage (low forage) or alfalfa hay/corn silage (high forage) diets twice or 12 times daily. Site of OM digestion shifted from the rumen to the small intestine and total tract OM digestion was increased when steers were fed the low forage diet. Nonbacterial N flows at the duodenum increased when steers were fed the low forage diet and when fed 12 times daily. Results of this study suggest that energy level of the diet can impact on site of nutrient digestion and supply of nutrients at different sites within the digestive tract. However, feeding frequency had minimal impact on digestive kinetics. In a concurrent project, effects of main treatment factors and bacterial harvesting techniques on bacterial composition were investigated. Whole ruminal contents were collected from steers and fluid- and particle-associated bacteria were obtained. Energy level, feeding frequency and pre-harvesting freezing had only minor effects on composition of harvested bacteria but differences were observed in fluid vs particle-associated or mixed populations of ruminal bacteria. In the second study, four multiple-cannulated steers were used in a 4 $times$ 4 Latin square design to examine effects of forage:concentrate ratio and ruminally degradable protein supply on microbial N Kinetics and net protein synthesis. Steers were fed ammoniated corn cob (high forage) or corn cob/ground corn/cornstarch (low forage) diets supplemented with soybean meal (SBM) or a combination of corn gluten meal and blood meal (CB). Efficiency of bacterial CF synthesis (E$sb{rm MCP}$) decreased when the low forage diet was fed but duodenal bacterial N flows were unaffected by energy level. Feeding SBM vs CB increased E$sb{rm MCP}$ and flow of bacterial N to the small intestine. It was concluded that inclusion of a ruminally degradable protein in the diet may synchronize release of nutrients from proteolysis with release of energy from fermentation.