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

This Article 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 Google Scholar Google Scholar Articles by Lemal, D. Articles by Ketelslegers, J.-M. Search for Related Content PubMed PubMed Citation Articles by Lemal, D. Articles by Ketelslegers, J.-M.

Effect of Pituitary Somatotropin Injections on Plasma Insulin-Like Growth Factor I and Somatotropin Profiles in Growing Heifers¹

Faculty of Agronomy and Husbandry Station, B-5800 Gembloux, Belgium, University of North Carolina, Chapel Hill, NC 27599 and University of Louvain, B-1200 Brussels, Belgium

Abstract

Effects of daily injections of pituitary-derived bovine somatotropin (bST) for 6 wk were evaluated in 10 growing heifers and compared to 9 placebo-treated control animals. Bovine somatotropin was injected at 50µg/kg BW each day. Body weight and growth, plasma concentrations of insulin-like growth factor I (IGF-I) and somatotropin (ST) were assessed. To measure plasma concentrations of IGF-I, we validated a RIA in which bovine plasma samples were extracted with acid-ethanol, a method that resulted in greater than 90% recovery of IGF-I. Average daily gain was similar during the first 4 wk of the experiment in both control and bST-treated groups; however, at the end of the experimental period (wk 4 and 6) ADG was greater (P < .05) in bST-treated heifers (1.24 ± .21 kg/d vs .75 ± .25 kg/d). Plasma IGF-I from wk 2 to wk 6 were increased in bST-treated animals (452 ± 97 ng/ml at wk 2; 683 ± 106 ng/ml at wk 6) compared with controls (293 ± 62 ng/ml at wk 2 (P < .01) and 293 ± 115 ng/ml at wk 6 (P < .001). Moreover, ADG over the 6-wk experimental period was correlated with mean IGF-I concentrations determined over the same period (r = .55; P < .01). As expected, mean plasma ST concentrations were increased in bST-injected animals from wk 1 to 6. Gel chromatographic profiles of bovine plasma exhibit a 150,000 molecular weight ST-dependent binding protein-IGF-I complex and a 30,000 molecular weight non-ST-dependent complex. This study validates a method for measuring IGF-I in cattle, and shows a positive relationship among IGF-I and ADG after ST treatment. No correlation, however, was found between plasma ST and growth performance.

¹ We are grateful to J. J. Van Wyk and M. E. Svoboda (Univ. of North Carolina) for the generous gift of purified human IGF-I, to L. L. Anderson (Iowa State Univ.) for plasma from a hypophysectomized calf and its age-matched control and to the Boxmeer Co. (Holland) for bovine somatotropin. Support for these studies was provided by National Institute of Health (USPHS) Research Grants AM 01022 and HD 08299 and by Institut pour l'Encouragement de la Recherche Scientifique dans l'lndustrie et l'Agriculture Research Grant 5081A.

² Chaire de Biologie Moléculaire et Physiologie Animale, Faculté des Sciences Agronomiques, B-5800 Gembloux, Belgium

³ Station de Zootechnie, Centre de Recherches Agronomiques, B-5800 Gembloux, Belgium

⁴ Dept. of Pediatr., Univ. of North Carolina.

⁵ Unité de Diabétologie et Nutrition, Université de Louvain.