Influence of chlortetracycline and dietary protein level on visceral organ mass of growing beef steers

Thirty-two beef steers (285 +/- 3 kg BW) were used to determine the effects of chlortetracycline and dietary protein level on visceral tissue mass, chemical composition, intestinal morphology, and proliferation rate indices. Steers were allotted randomly by weight to a factorial arrangement of dieta...

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Bibliographic Details
Published in:Journal of animal science 2000-12, Vol.78 (12), p.3169-3176
Main Authors: Baldwin, R. L, McLeod, K. R, Elsassert, T. H, Kahl, S, Rumsey, T. S, Streeter, M. N
Format: Article
Language:English
Subjects:
Administration, Oral
Animal productions
Animals
Biological and medical sciences
Body Weight - drug effects
Cattle
Cattle - growth & development
Cell Division - drug effects
Chlortetracycline - administration & dosage
Chlortetracycline - pharmacology
Dietary Proteins - administration & dosage
Dietary Proteins - pharmacology
Digestive system
Enterocytes - cytology
Enterocytes - drug effects
Fundamental and applied biological sciences. Psychology
Male
Proteins
Random Allocation
Terrestrial animal productions
Tissues
Vertebrates
Viscera - drug effects
Viscera - growth & development
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Summary:Thirty-two beef steers (285 +/- 3 kg BW) were used to determine the effects of chlortetracycline and dietary protein level on visceral tissue mass, chemical composition, intestinal morphology, and proliferation rate indices. Steers were allotted randomly by weight to a factorial arrangement of dietary treatments consisting of either 10 or 13% CP diets top-dressed with a corn meal carrier (500 g/d) containing either 0 or 350 mg of chlortetracycline. After 84 d, steers were slaughtered and visceral organs removed and separated. Rinsed wet tissue mass was recorded; total RNA, total DNA, tissue DM, and tissue N content were determined; and tissue sections were prepared for immunohistochemical analysis. Thin tissue sections were evaluated to determine crypt depth and villus height as well as proliferation rate by immunohistochemical detection of the nuclear antigen Ki67. Rumen and abomasum weights and small intestinal length were greater (P < 0.04) in steers fed the 13% CP diet than in those fed the 10% CP diet on both an absolute weight basis and a percentage of empty BW. Chemical composition of the small intestinal and ruminal segments were largely unaffected by increased dietary protein. Increasing the dietary CP also increased the villus height in duodenal (P = 0.02) and the crypt depth of jejunal (P = 0.03) sections. Dietary administration of chlortetracycline decreased (P < 0.01) small intestinal weight both on absolute and empty BW bases. Nitrogen and RNA concentrations of the small intestinal segments were unaffected (P > 0.1) by dietary administration of subtherapeutic levels of chlortetracycline; however, because of increases (P < 0.05), or tendencies for an increase (P < 0.1), in the tissue content of DNA, the ratio of N to DNA was decreased (P < 0.05) or tended to be decreased (P < 0.1) in the small intestinal segments of the chlortetracycline-treated animals. The observed decrease in small intestinal epithelial mass does not appear to be due to alterations in cell proliferation rate but rather cell size. Consistent with this finding, cell proliferation, as determined by Ki67 antigen staining, was not affected by dietary treatment. Chlortetracycline administration decreased small intestinal mass that may be a result of decreased cell size.
ISSN:0021-8812
1525-3163
0021-8812
DOI:10.2527/2000.78123169x