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GnRH injection
before artificial insemination (AI) alters follicle dynamics
in Iranian Holstein cows
E. Dirandeh, H.
Kohram* and A. Z. Shahneh
Department of Animal Science, College of Agriculture and
Natural Resources, University of Tehran, Karaj, Iran.
*Corresponding author. E-mail:
kohram@can.ut.ac.ir.
Tel.: +98-261-2248082.
Fax: +98-261-2246752.
Accepted 21 May, 2009 |
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The objective of the present study was to evaluate the
ovarian response of cows to gonadotropin-releasing hormone
(GnRH) injection on day 6 of the estrous cycle. The estrous
cycles of 10 cows were synchronized with 2 intramuscular
(im) injections of prostaglandin F2α given 11 d apart. The
cows were randomly assigned to 1 of 2 treatments. Cows in
the control treatment received no treatment, whereas GnRH6
cows received a GnRH injection on d 6 of the estrous cycle
(estrus = d 0). Daily, from estrus d 0 to the next estrus d
23, cows had their ovaries scanned by ultrasound. Profiles
of the mean number of follicles (that is, 4 - 6 mm and ≥ 7
mm) and the diameter of the largest follicle (F1) were
compared by least squares analysis of variance using the
general linear model (GLM) procedure of SAS. In response to
an injection of GnRH, the number of small follicles in group
GnRH6 on day 6 (1.5 ± 0.6 follicles) increased (P ≤ 0.05) on
day 8 (5.0 ± 0.7 follicles) and the number of medium and
large follicles (≥ 7 mm) on day 6 (2.0 ± 0.5 follicle)
decreased (P ≤ 0.05) on day 9 (0.8 ± 0.6 follicles). In
conclusion, an injection of GnRH on day 6 of the estrous
cycle could promote the emergence of a new follicular wave
in cows.
Key words:
Ultrasonography, follicle, GnRH, Iranian Holstein cows. |
