Plasma GH, IGF-I, and conception rate in cattle treated with low doses of recombinant bovine GH.
Blood and uterine concentrations of GH and insulin-like growth factor (IGF)-I are correlated with improved fertility in cattle. We tested incremental doses of a 14-d sustained release recombinant bovine GH (rbGH) to increase blood GH and IGF-I (Experiments 1 and 2). Conception rate after administration of an optimized rbGH dose was also tested (Experiment 3). In Experiment 1, lactating Holstein cows (n = 18) were randomly assigned to receive 0 (n = 5), 100 (n = 5), 200 (n = 5), or 500 (n = 3) mg sc rbGH. Increasing the doses of rbGH was associated with increased serum concentrations of GH and IGF-I. The 100- and 200-mg doses caused an IGF-I release that was below and above, respectively, the perceived optimum response. Therefore, Experiment 2 was designed to test a rbGH dose (167 mg), which was intermediate to the doses tested in Experiment 1. Lactating and nonlactating postpartum beef cows were treated with 0 (n = 9) or 167 (n = 9) mg rbGH at insemination. Plasma concentrations of GH and IGF-I were greater in rbGH-treated cows than in controls. Lactating cows had initial IGF-I concentrations that were lower than nonlactating cows. The 167-mg dose of rbGH increased plasma IGF-I concentrations in lactating cows to the levels of those of nonlactating cows. In Experiment 3, cows and heifers were administered either 0 or 167 mg rbGH at insemination. The conception rate for rbGH-treated and control cows was 54.4 and 49.5% (n = 617), and 46.0 and 46.3% for heifers (n = 1123), respectively. Herd (P<0.01) and parity (P<0.01) affected conception rate, but conception rates for rbGH and control cattle were similar. In summary, low doses of rbGH increased blood GH and restored blood IGF-I concentrations in lactating cows to those of nonlactating cows, but the conception rate in cows and heifers was not affected by administration of 14-d sustained-release rbGH at insemination.
Bilby
C R
CR
Department of Animal Science, University of Missouri, Columbia 65211, USA.
Bader
J F
JF
Salfen
B E
BE
Youngquist
R S
RS
Murphy
C N
CN
Garverick
H A
HA
Crooker
B A
BA
Lucy
M C
MC
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D019382:Human Growth Hormone / Q000008:administration & dosage*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D007774:Lactation / Q000502:physiology; D010298:Parity; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone