Ovarian response and follicular development in heifers treated with FSH injected by subcutaneous route followed by intramuscular buster 48 later
Keywords:
heifers, FSH, route, superovulationAbstract
A single injection of FSH applied by subcutaneous (sc) route induces superovulation in bovines. However, sc injection results in a brief surge in FSH plasmatic levels. Therefore, we speculate that FSH may be necessary to instigate the final development of some follicle. This study was done to evaluate the ovarian response of heifers treated with a intramuscular (im) subidose of FSH 48 hours after the initial sc injection. Fifteen crossbreed heifers were treated with a progestagen vaginal implant (CIDR-B) and injected im with 2.5 mg estradiol benzoate. Four days later, heifers were assigned randomly in 3 groups of 5 animals each and superovulated with pFSH as follows: group 1 and 2 received a sc injection of 400IU and 380 IU, respectively, while group 3 received 400 IU injected im in decreasing sub-doses (80-80; 60-60; 40-40 e 20-20UI) at 12- hour intervals during four consecutive days. The CIDR-B was withdrawn forty-eight hours after the initial FSH injection and heifers were injected im with 150-mcg of cloprostenol. Additionally, group 2 was injected im with 80 IU of pFSH. Heifers from all groups were inseminated 48 and 62 hours after the cloprostenol injection. Evolutions of follicular growth and pFSH plasmatic levels were monitored daily during the superovulation process. Embryo collection and corpora lutea (CL) estimation were done seven days after insemination. Data were submitted to analysis of variance (Proc GLM do SAS). There was no significant difference in follicular growth among the groups. Plasmatic pFSH concentration increases in the first few hours after the initial im or sc injection and decrease to basal levels after 24 hours in groups 1 and 2, while pFSH concentration of group 3 remained high until the end of the treatment. Group 2 had a second surge after the additional im injection of pFSH. There was no difference in CL number (8.4 ± 1.7; 10.2 ± 2.8 and 11.0 ± 2.6) and recovered embryos (5.3 ± 1.8, 6.1 ± 2.1 and 6.3 ± 2.0) of groups 1; 2 and 3, respectively. It was concluded that an additional sub-dose of FSH, injected 48h after one single sc injection of FSH, does not improve the superovulatory response of heifers.
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