Document Type

Thesis - Open Access

Award Date

2015

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Robbi H. Pritchard

Keywords

chromium, insulin, steers

Abstract

A series of experiments were conducted to evaluate the influence of supplemental dietary chromium (0 or 400 ppb) on insulin responsiveness in finishing steers (Exp 1. and Exp 2.), and energy status in newly weaned steers upon introduction to the feedlot (Exp 3.). To evaluate insulin responsiveness, two models were used with finished steers of different ages: Exp 1. 12 steers; 24 mo old (BW=783 ± 29 kg); and Exp 2. 24 steers; 14 mo old (BW=625 ± 24 kg). A jugular infusion of insulin (0.45 IU bovine insulin/ kg of BW0.75, INS) was pulse dosed 2 h post-prandial. A jugular infusion of PBS (SHAM) was included in Exp. 2. Blood samples were collected at -30, 120, 195, 255, and 315 min)\ relative to the morning feed delivery after 84 d (Exp 1.) and 86 d (Exp 2.) on test diets. No diet x time interactions were detected for any plasma metabolites in old or young steers. In Exp 2., INS effectively cleared plasma glucose (GLS). Diet had no impact on changes in GLS in Exp 2. Diet had no impact (P > 0.20) on plasma concentrations of insulin in either experiment. In Exp 2., there tended (P=0.10) to be a diet x insulin interaction for post-infusion insulin levels. Insulin values were similar for all steers at (t195) and (t315) and elevated at (t255) for non-Cr fed steers subjected to INS. At t120, CrP caused greater (P < 0.05) plasma urea-N (PUN) concentrations when compared to CON in Exp 1. but not in Exp 2. Effects of Cr on PUN in Exp 1. may be due to improved insulin sensitivity affecting AA uptake in the peripheral tissue of old, heavy steers. In Exp 3., there were no diet x day interactions (P>0.20) for GLS, insulin, or PUN. The GLS and PUN levels were similar between diets (P > 0.20). Insulin levels were higher (P0.20) between diets on d 5 and higher (P < 0.05) on d 12 in calves fed CrP. The shift in NEFA on d 12 coincided with a spike in insulin levels. Both events occurred at the time that NEG intake was approaching the acclimated plateau and neither event impacted glucose status. The effective use of chromium in feedlot diets is likely dictated by age dependent differences in insulin sensitivity, metabolite needs for growth, and the degree of stress that ultimately result in a chromium deficient state.

Library of Congress Subject Headings

Beef cattle -- Feeding and feeds Beef cattle -- Metabolism Dietary supplements -- Physiological effect Chromium

Description

Includes bibliographical references (pages 58-62)

Format

application/pdf

Number of Pages

75

Publisher

South Dakota State University

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Rights Statement

In Copyright