HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mader, T. L. Articles by Kreikemeier, W. M. Search for Related Content PubMed PubMed Citation Articles by Mader, T. L. Articles by Kreikemeier, W. M.

Effects of growth-promoting agents and season on blood metabolites and body temperature in heifers^1,2

T. L. Mader^*,3 and W. M. Kreikemeier

^* Department of Animal Science, University of Nebraska, Concord 68728; and and Alltech Biotechnology, Heartland Regional Office, Columbus, NE 68601

³ Corresponding author: tmader{at}unlnotes.unl.edu

To assess the efficacy of growth-promoting agents among seasons, triiodothyronine (T₃), thyroxine (T₄), plasma urea nitrogen (PUN), IGF-I, and tympanic temperature (TT) were measured in summer and winter studies. Heifers (n = 9/pen) were allotted to 12 pens in both December and June. Pens were assigned to 1 of 6 growth promotant treatments: control (no growth promotant), estrogenic implant (E), trenbolone acetate implant (TBA), E + TBA (ET), melengestrol acetate (MGA), and ET + MGA (ETM). Blood samples were collected from 4 heifers per pen per study on d 0, 28, 56, and 84 via jugular puncture. Near the midpoint of both studies, TT were obtained from the heifers. There was a season by sample day interaction for all blood metabolites (P < 0.05). During the winter, IGF-I levels peaked on d 28, whereas T₃, T₄, and PUN peaked on d 56. In the summer, IGF-I levels increased from d 0 to 28 and remained elevated throughout the study. Season by growth promotant interactions (P < 0.05) indicated that in the winter ET increased T₃, whereas TBA alone decreased both T₃ and T₄, compared with control, or ET, and ETM treatment groups. Across seasons, treatments ET and ETM increased (P < 0.05) IGF-I and decreased (P < 0.05) PUN. However, E, TBA, and MGA alone had no effect on IGF-I or PUN concentrations. The maximum TT was greater (P < 0.01) in the summer than in the winter, whereas the minimum TT was lower (P < 0.01) in the summer. Mean TT did not differ among growth-promoting treatments. However, in the summer and over both seasons, the maximum TT was lower (P < 0.05) in E-, MGA-, and ETM-treated heifers. Although limited growth promotant by season interactions existed, changes in blood metabolite levels resulting from the use of growth promotants do not appear to influence seasonal changes in body temperature as measured by TT.

Key Words: anabolic steroid • body temperature • feedlot • heifer • season • serum hormone

This article has been cited by other articles:

				J. L. Amundson, T. L. Mader, R. J. Rasby, and Q. S. Hu Environmental effects on pregnancy rate in beef cattle J Anim Sci, December 1, 2006; 84(12): 3415 - 3420. [Abstract] [Full Text] [PDF]