Effects of ruminal nutrient degradability on volatile fatty acid dynamics, ruminal epithelial gene expression, and post-absorptive system

This study evaluated degradable nutrient supply effects on VFA concentrations, fluid flux and pool sizes, rumen epithelial metabolic and absorptive genes, and post-absorptive muscle and blood responses. Six ruminally cannulated Holstein heifers (BW=330 ± 11.3 kg) were used in a partially replicated Latin Square experiment with four treatments consisting of beet pulp or timothy hay and barley or corn grain. Periods were18 d with 3 d diet adaptation and 15 d of treatment. During each period, d 10 to 14 was used for in situ nutrient degradation assessment, d 16 to 18 was used for rumen fluid sampling, and d 18 was used for rumen papillae and skeletal muscle biopsies and blood sampling. In situ ruminal starch disappearance rate (barley 7.61 to 10.5 %/h vs corn 7.30 to 8.72%/h; P = 0.05) and extent of fiber disappearance (timothy hay 22.2 to 33.4 % DM vs beet pulp 34.4 to 38.7 % DM P=0.0007) differed significantly among diets. Acetate (P = 0.02) and isovalerate (P = 0.008) molar percentages (% mol) were increased by timothy hay, but propionate (P = 0.06) and valerate (P = 0.10) molar percentages were decreased. Corn increased propionate (P = 0.02) and valerate (P = 0.049) molar percentage, but decreased butyrate (P = 0.04) molar proportion. Fluid volume and fluid passage rate, and individual VFA pool sizes were not influenced by diet (P > 0.05). Four epithelial genes, two metabolic and two absorptive, had increased expression on timothy hay diets (P < 0.15). Blood acetate concentration was influenced by treatment (P = 0.067) but no other blood metabolites were. Skeletal muscle metabolic rate was significantly increased on corn diets (P = 0.023). The results of this study provide a whole-system snapshot of how the rumen environment changes on diets differing in nutrient degradability and how the post-absorptive system adapts in response.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Animal and Poultry Sciences

Department dc:contributor.department

Animal and Poultry Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2019

Author dc:creator

• Beckett, Linda Marie

Chair dc:contributor.committeechair

• White, Robin R.

Committee members dc:contributor.committeemember

• Rymph, Mary Beth Hall
• Wilson, Thomas Bain

• volatile fatty acids
• nutrient degradability
• rumen epithelium
• skeletal muscle metabolic rate

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:18059

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/87471