Authors : K. R. McLeod , R. L. Baldwin , T. S. Rumsey , T. H. Elsasser , S. Kahl and M. N. Streeter
Abstract: The objective of this study was to determine the effects of oral administration of a subtherapeutic amount of chlortetracycline (CTC) on plasma concentrations of insulin-like growth factor-1 (IGF-1) in bovine receiving two levels of dietary protein. Thirty-two beef steers, weighing 286 ? 3 kg, were allotted randomly by weight to a factorial arrangement of treatments consisting of diets containing either marginal (10%) or adequate (13%) amounts of crude protein supplemented with a corn meal carrier (500 g/d) containing either 0 or 350 mg CTC. Blood samples were collected from each steer via jugular puncture on d 0, 7, 14, 28, 56, and 84 and plasma concentrations of IGF-1 were determined by radioimmunoassay. Across the 84-d sampling period, mean plasma IGF-1 concentration was greater (P < .03) in steers fed 13% protein compared with those fed 10% protein. However, there was a tendency (P < .11) for a CTC ? dietary protein interaction. Analysis within d revealed that on d 7 and 14 plasma IGF-1 concentration in steers fed 10% protein was greater for those receiving CTC compared with those fed carrier alone (CTC ? dietary protein, P < .10). However, by d 28 only a numerical difference was observed and by d 56 this temporal effect of CTC was no longer apparent. Results from this study suggest that oral administration of a subtherapeutic amount of CTC increases circulating IGF-1 concentrations in a temporal fashion in steers when dietary protein supply is marginal.
K. R. McLeod , R. L. Baldwin , T. S. Rumsey , T. H. Elsasser , S. Kahl and M. N. Streeter , 2003. Influence of Subtherapeutic Chlortetracycline and Dietary Protein on Circulating Concentration of Insulin-Like Growth Factor-1 in Growing Beef Steers . Journal of Animal and Veterinary Advances, 2: 531-535.