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The Professional Animal Scientist 23 (2007):509–512 Estradiol Cypionate did not Affect Pregnancy Rates of Beef Cattle
Synchronized with a Modified
Timed Artificial Insemination
Protocol
J. M. Howard,* R. Manzo,* F. Frago,* D. G. Falk,* J. B. Glaze, Jr.,† J. C. Dalton,‡
and A. Ahmadzadeh*1
*Department of Animal and Veterinary Science, University of Idaho, Moscow 83844; †Twin Falls
Research and Extension Center, Twin Falls, Idaho 83303; and ‡Caldwell Research and Extension
Center, Caldwell, Idaho 83605
nated by a single inseminator. Pregnancy ABSTRACT
status was determined by ultrasonogra- A study was conducted to determine Data were analyzed by logistic regres- the effect of inclusion of estradiol cypio- sion. Pregnancy per AI (53.3% COS-ECP nate (ECP) in a conventional gonadotro- vs. 57.0% COS-C) and 70-d pregnancy tropin-releasing hormone (GnRH)-
pin-releasing hormone (GnRH)-prosta- rates to AI and natural service (92.2% prostaglandin F2α (PGF2α)-GnRH
glandin F2α (PGF2α)-GnRH-timed AI pro- COS-ECP vs. 90.3% COS-C) did not dif- fer between treatments. Days postpartum pregnancy rates in beef cattle. The objec- had no effect on the odds ratio of preg- tive was to determine if administration nancy. The results indicate that the incor- of 0.25 mg of ECP at the time of the sec- poration of 0.25 mg of ECP into the Co- ond GnRH injection would effectively in- synch protocol did not affect pregnancy crease conception to AI and improve preg- per AI and 70-d pregnancy rates in beef nancy rates. Cows were presynchronized with an i.m. injection of 25 mg of PGF2α on d 14. On d 0, Cosynch (COS) Key words: timed artificial insemina-
was initiated with administration of 100 µg GnRH (i.m.) followed 7 d later with 25 mg of PGF2α (i.m.). On d 9 cows were paired by age, BCS, and BW and INTRODUCTION
assigned randomly to receive either ECP; n = 90) or GnRH (100 µg) + vehi- cle (COS-C; n = 93). Following treat- ment, all cows were immediately insemi- hormone (LH) surge) decreased se-
rum estradiol (E2) and reduced fertil-
treatment of cattle 48 h after PGF2α MATERIALS AND METHODS
Animals and Treatments
Statistical Analysis
using SAS (SAS Inst. Inc., Cary, NC).
RESULTS AND DISCUSSION
being obese (Richards et al., 1986).
synch (COS) protocol was initiated
no effects of treatment (P > 0.9) on with an i.m. injection of 100 µg of tion of 25 mg of PGF2α (i.m.). Cows by treatment (P > 0.9) and averaged ment (COS-ECP; n = 93) or control
(COS-C; n = 90). The COS-ECP cows
received (i.m.) GnRH (100 µg) + 0.25 of 0.25 mg estradiol cypionate (ECP)
GnRH injection (GnRH d 0, PGF2α d µg) + cottonseed oil (1 mL).
A Modified Timed Artificial Insemination Table 1. Body weight, BCS, and ages of cows treated with Cosynch
with and without estradiol cypionate1
Treatment2
1Means ± SD.
2COS-ECP: Cosynch was initiated with the administration of 100 µg GnRH (d 0)followed by PGF2α on d 7. On d 9 cows received (i.m.) GnRH (100 µg) + 0.25 mgof estradiol cypionate (ECP) in cottonseed oil (1 mL) and were immediatelyinseminated. COS-C: Cosynch was initiated with the administration of 100 µgGnRH (d 0) followed by PGF2α on d 7. On d 9 cows received (i.m.) GnRH (100 µg)+ cottonseed oil (1 mL) and were immediately inseminated.
Figure 1. Pregnancy per AI and 70-dpregnancy rates of cows that receivedCosynch (COS-C; n = 93) or Cosynch with estradiol cypionate (COS-ECP; n = 90). treated cows as shown by Sellars et al.
concentrations between COS-ECPand COS-C cows. Consequently, AI atthe time of ECP administration maynot allow adequate time for E2 con- Table 2. Odds ratio estimates for pregnancy per AI of beef cows
centration to positively affect fertility.
treated with Cosynch with (COS-ECP) and without estradiol cypionate
(COS-C)1
transport likely occurred when theuterine environment of the ECP- confidence limits
estimate2
P value
induced E2 depression and thus im-prove fertility of the Cosynch proto- 1COS-ECP: Cosynch was initiated with the administration of 100 µg GnRH (d 0) followed by PGF2α on d 7. On d 9 cows received (i.m.) GnRH (100 µg) + 0.25 mg of estradiol cypionate (ECP) in cottonseed oil (1 mL) and were immediatelyinseminated. COS-C: Cosynch was initiated with the administration of 100 µg 2α on d 7. On d 9 cows received GnRH (100 µg) + cottonseed oil (1 mL) and were immediately inseminated.
2Odds ratio estimates: a value greater than 1 indicates increased risk for conception whereas a value lower than 1 indicates a reduced risk for conception.
Moreover, the same dose of ECPtended to improve conception in beef (ECP) into a timed artificial insemination pro- productive management on reproductive and lactational performance of Holstein dairy rates in beef cattle. J. Anim. Sci. 81(Suppl.
Sellars, C. B., J. C. Dalton, R. Manzo, J. Day, Bathla, H., S. S. Guraya, and G. K. Sangha.
1999. Role of estradiol in the capacitation and dence of ovulation and conception rates after acrosome reaction of hamster epididymal sper- incorporating estradiol cypionate into a timed matozoa in the isolated uterus of mice incu- bated in vitro. Indian J. Physiol. Pharmacol.
Stevenson, J. S., Y. Kobayashi, M. P. Shipka, and K. C. Rauchholz. 1996. Altering concep- Geary, T. W., and J. C. Whittier. 1998. Effects tion of dairy cattle by gonadotropin-releasing of a timed insemination following synchroni- hormone preceding luteolysis induced by pros- IMPLICATIONS
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ministration of estrogen to estrous rabbits.
Corah. 2000. Synchronizing estrus and(or) ovulation in beef cows after combinations of Langendijk, P., E. G. Bouwman, N. M. Soede, GnRH, norgestomet, and prostaglandin F2α M. A. M. Taverne, and B. Kemp. 2002. Myo- with or without timed insemination. J. Anim.
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