Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
Poster Abstracts 39
P034
Potency of several GnRH agonists (Buserelin, Dalmarelin,
Gonavet and Gonazon) versus natural GnRH (Cystorelin)
in an in vitro functional assay.
Driancourt, MA 1 *, Fournier, R 2 , Ptaszinska, M 3 , Doornmalen, E 4 , Blomenrohr,
M 4
1Reproduction, Intervet Pharma R&D, France; 2 Intervet France, France;
3Intervet International Bv, The Netherlands; 4 Organon Bv, The Netherlands
Natural GnRH and several GnRH analogues are widely used to
synchronize oestrus and ovulation, as well as for treatment of
reproductive pathologies (cysts) in cattle. However, the relative
potency of each agonist relative to natural GnRH is not known. The
aim of the present study was to use an in vitro test (measuring
receptor activation) to compare the potency of natural GnRH (as
Cystorelin) versus several GnRH agonists. The agonists included
were Depherelin (D- Phe6-LHRH) (Gonavet, Veyx Pharma),
Lecirelin (D-Tle6, ProNHEt9- LHRH) (Dalmarelin, Fatro/Virbac),
Buserelin (D-Ser(But)6, Pro9-NEt- LHRH)(Receptal, Intervet) and
Azagly-nafarelin (D-Nal(2)6, α-aza-Gly10-LHRH)(Gonazon,
Intervet).The in vitro test used a CHO cell line expressing the human
GnRH receptor gene together with a beta lactamase reporter gene. In
this test, cells form β lactamase upon GnRH stimulation. B-lactamase,
in turn, cleaves a fluorogenic membrane permeable substrate (CCF4).
Non-responsive cells with low β lactamase appear green, while
responsive cells with high β lactamase appear blue. In the present
experiment, CHO-GnRH-R-β-lactamase bearing cells were plated for
16-20h before being challenged with GnRH. Cells were then
incubated with a range of concentrations of each test compound. Five
hours later, fluorogenic substrate (CCF4) was added to the cells and
the cells were incubated for 2h . The microplate was read with 405nm
excitation and 460 and 530nm emission. The data were plotted as a
ratio of the emissions at 460 (blue) and 530nM (green). Two separate
experiments were run, each dose response curve being generated by
four replicates. The effects of the different concentrations of GnRH or
GnRH agonists applied were compared using EC 50 (concentration
of GnRH applied generating a half maximum response) for each
compound. The sigmoid shapes of the dose-response curves were
similar in both experiments. In both assays, the dose-response curves
describing receptor activation by the different GnRH could be divided
into two sub-groups. On one hand, Buserelin, Azagly-nafarelin and
Depherelin displayed similar dose response curves resulting in similar
EC50-values (0.7 to 1.6ng/ml). On the other hand, Cystorelin and
Lecirelin (which behaved similarly) displayed higher EC50-values (8
to 15ng/ml). In both assays the slopes of the dose-response curves
proved similar, irrespective of the compound tested. The use of this
cell line therefore proved to be a potent tool to compare potencies of
different GnRH agonists.
P035
Screening of parturition time models of Holstein breed in
a dairy herd in Karaj suburb
Ebrahimi, A 1 *; Gharaghoozloo, F 2 ; Vojgani, M 2
1Department of Clinical Science, Faculty of Veterinary Medicine, Islamic Azad
University, Garmsar Branch, 2 University of Tehran, Iran
The influences of breeding group, age of dam, sex, calving problems
like dystocia, abortion and some calving abnormalities, like stillbirth
on the time of day of parturition were studied. Cross-sectional surveys
of 6606 calving records between 1989 and 2005 were analyzed by the
least-squares and the chi-squared procedures. The cases were divided
based on the time of parturition within 24 hours in four groups of six
hours each, as follows: 0-6, 7-12, 13-18, 19-24 hour with their
belonging calving numbers of 1762, 1787, 2031 and 1027,
respectively. The distribution within these groups were characterized
with the following percentages based on the calving process: normal
calving: 86.8, 79.4, 78.7 and 84.8, dystocia (grade one): 2.5, 5.3, 6.6
and 2.2, dystocia (grade two): 10.6, 14.7, 14.3 and 12.6, severe
dystocia (grade three): 0.2, 0.7, 0.4 and 0.4. The cases were divided in
four groups according to the seasonal distribution of parturitions so
24,4% of all parturitions occurred during spring, 26.2% during
summer, 26% during autumn and 23.4% during winter. The seasonal
occurrence of stillbirth were 3.9, 4, 3.8 and 5.5%, respectively
(P=0.06). The seasonal occurrence of dystocia were16.8, 14.8, 18.7
and 22.4% with P