Effects of recombinant bovine somatotropin implants on serum concentrations of somatotropin, insulin-like growth factor-I and blood urea nitrogen in steers.
Four cross-bred beef steers averaging 346 kg were used in a 4 x 4 Latin square design to determine the effect of prolonged-release recombinant bovine somatotropin (rbGH) implants on serum concentrations of somatotropin (GH), insulin-like growth factor-I (IGF-I) and blood urea nitrogen (BUN). Recombinant bGH implants of 0, 40, 80 or 160 mg were administered subcutaneously in the tailhead during the 4 trial periods. Each steer received each treatment starting at 06:00 on day 0 with 21 days between treatments. Jugular vein blood samples were collected on days 0, 1, 2 and 3 (4 day time course for GH, IGF-I and BUN) and every 15 min (GH profile) for 6 h on day 3. Serum baseline GH values were higher (P < 0.10) for the 80 and 160 mg treatments than for the control, and peak amplitude was decreased (P < 0.05) by the 40 and 160 mg treatments. There was a trend (P < 0.11) for fewer GH peaks during the 160 mg treatment. Somatotropin concentrations decreased from day 1 to day 3 (P < 0.05) in a linear manner. Serum IGF-I concentrations increased (P < 0.05) in a linear dose-dependent manner from the 0 mg to the 160 mg treatment. BUN concentrations were not significantly altered by rbGH treatment. Results from this experiment indicate that rbGH implants significantly increase serum IGF-I and GH baseline concentrations while suppressing GH peak amplitude in finishing steers.
Roeder
R A
RA
Department of Animal and Veterinary Science, University of Idaho, Moscow 83844-2330.
Garber
M J
MJ
Dalke
B S
BS
Kasser
T R
TR
Veenhuizen
J
J
Schelling
G T
GT
D000818:Animals; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000097:blood*; D004343:Drug Implants; D013006:Growth Hormone / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011994:Recombinant Proteins / Q000494:pharmacology
D004343:Drug Implants; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone