Effect of monensin supplementation on ruminal and postruminal digestion in sheep and on adaptation of ruminal microbes

Three experiments were conducted to examine the effects of an ionophore, monensin sodium, on digestion in sheep. The first experiment was concerning alterations induced by long-term supplementation and subsequent withdrawal of the ionophore. The diet was a pelleted mixture of 43% native prairie hay, 34% corn grain, and 21% lupin grain plus 100 g wheat straw. Monensin (33 ppm) was added to the diet of four wethers, and four other animals served as controls and consumed an identical diet. without monensin. Monensin supplementation increased (P <.05) ruminal propionate while decreasing (P <.05) acetate levels throughout the 146-d experiment. Withdrawal caused acetate to return to control levels but decreased (P <.05) propionate. During ionophore supplementation, the digestibilities of organic matter (OM) and dry matter (DM) were increased (P <.05) by an average of 8 and 9%, respectively. Apparent digestibility ' of N was increased from 75 to 77% after 19 d of supplementation. There was an augmentation (P <.05) in the flow of bacterial N at the duodenum after 96 d of supplementation. This effect disappeared with ionophore withdrawal. In a second experiment, the effect of monensin on postruminal digestion was examined in three trials with six wethers. There were three treatments: control, dietary monensin, and monensin infused into the duodenum. The diets were the same as in the previous experiment. Dietary monensin caused the same changes in ruminal VFA as in the previous experiment. Infused monensin had no effect on VFA. Dietary monensin increased (P <.05) trypsin activity at the ileum. Dietary ionophore did not alter nutrient digestibilities, but shifted (P <.O5) the site of OM and DM digestion from the cecum to before the terminal ileum by 14 and 10%, respectively. In an in vitro experiment rumen contents from monensin-adapted and nonadapted sheep were compared with and without additional ionophore in a 6 h incubation system. Rumen contents from adapted sheep did not differ from contents of nonadapted sheep in the quantity of microbial N synthesized. With monensin addition to the incubation, microbial synthesis dropped by 49% in nonadapted microorganisms. In adapted contents, the decrease in synthesis was only 9%. Monensin-adapted microbes degraded (P <.O1) more protein substrate than those which were not adapted.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Animal Science

Department dc:contributor.department

Animal Science

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1987

Author dc:creator

• Rogers, Michaela G.

Chairs dc:contributor.committeechair

• Fontenot, J.P.
• Thivend, P.

Committee members dc:contributor.committeemember

• Ferry, James G.
• Gerken, Hubert J. Jr.
• Jouany, J.P.
• McCarthy, Farabee D.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

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

Handle dc:identifier.uri

http://hdl.handle.net/10919/49879

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/49879