Effect of pituitary somatotropin injections on plasma insulin-like growth factor I and somatotropin profiles in growing heifers.

Lemal, D;Renaville, R;Claes, V;Ruelle, L;Ketelslegers, Jean-Marie;et.al.
(1989) Journal of Animal Science : leading source of new knowledge and perspectives in animal science — Vol. 67, n° 10, p. 2715-2723 (1989)

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  • Lemal, D
    Author
  • Renaville, R
    Author
  • Claes, V
    Author
  • Ruelle, L
    Author
  • Fabry, JeanUCLouvain
    Author
  • Ketelslegers, Jean-MarieUCLouvain
    Author
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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 50 micrograms/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 less than .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 less than .01) and 293 +/- 115 ng/ml at wk 6 (P less than .001). Moreover, ADG over the 6-wk experimental period was correlated with mean IGF-I concentrations determined over the same period (r = .55; P less than .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.
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Lemal, D., Renaville, R., Claes, V., Ruelle, L., Fabry, J., Burny, A., Underwood, L. E., & Ketelslegers, J.-M. (1989). Effect of pituitary somatotropin injections on plasma insulin-like growth factor I and somatotropin profiles in growing heifers. Journal of Animal Science : leading source of new knowledge and perspectives in animal science, 67(10), 2715-2723. https://hdl.handle.net/2078.5/51489 (Original work published 1989)