Effect of long-term treatment with recombinant bovine somatotropin andestradiol on hormone concentrations and ovulatory response ofsuperovulated cattle

摘要

The objective was to assess effects of long-term treatment with recombinant bovine somatotropin (bST) and estradiol-17 beta (E2) on the number of follicles that ovulated in response to FSH. Non-lactating Holstein and Jersey cows (Trial 1, n=27) and Angus cows and heifers (Trial 2, n=35) received two ear implants of E2 and biweekly injections of bST in a 2 x 2 arrangement of treatments. Estradiol implants were removed 74.6 +/- 1.1 d after insertion and 18.1 +/- 0.9 d after the last biweekly injection of bST. Cows were stimulated with FSH-P beginning 2 d after removal of E2 implants, and PGF2alpha (PGF) was given on the third day of FSH treatment. Ovaries were collected to determine the number of CL at 1 to 2 wk after treatment with PGF. In Trial 2 only, cattle were inseminated at estrus and embryos were collected 6 to 8 d later. Implants of E2 increased (P < 0.01) serum E2 8-fold initially and E2 was still elevated 5-fold at removal of implants. Injections of bST increased (P < 0.01) serum growth hormone (GH) 15-fold and insulin-like growth factor-I (IGF-I) 3-fold. In Trial 1, number of CL was increased by the combination of bST+E2 (P < 0.01). In Trial 2, E2 increased the number of CL (P < 0.05), and bST increased the number of total ova and transferable embryos (P < 0.01). We conclude that long-term treatment with bST and E2 may interact to enhance follicular development and ovulatory response to FSH.