Year of Publication

2013

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture

Department

Animal and Food Sciences

First Advisor

Dr. Kyle McLeod

Abstract

The impact of lactate producing direct-fed microbial (DFM) on growth performance and rumen fermentation in beef cattle was explored in four studies. Experiment 1 studied the interaction between DFM and degradable intake protein (DIP) supply in receiving cattle. No differences (P≥0.06) in intake, morbidity, or immune response were observed; however, during the first 28 d gain and efficiency responses to DFM were dependent on DIP (DIP×DFM P≤0.05). Experiment 2 showed that in vitro gas production and select endpoint metabolites differed (P≤0.04) with DFM application. Experiment 3 compared lactate producing DFM to a lactate producing/utilizing DFM in finishing cattle. No differences (P≥0.14) in intake, gain, efficiency, or carcass characteristics were observed between control and lactate DFM; however, gain and growth efficiency differed (P≤0.05) between the lactate producing and lactate producing/utilizing DFM during the later portions of feeding. Experiment 4 studied the impact of DFM on ruminal fermentation, lactate utilization, and total tract digestibility. Ruminal pH and molar proportions of acetate were increased (P≤0.05) with DFM; however, lactate utilization and total tract digestibility did not differ (P≥0.33). The studies suggest that DFM improve growth performance during receiving and responses are at least partly mediated through differences in ruminal fermentation.

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