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Title: Embryo transfer in Angus and Brahman recipient cows: effect of two methods of estrus synchronization on induced estrus and pregnancy

item Chase, Chadwick - Chad
item Hammond, Andrew - Andy

Submitted to: Revista Cientifica-Universidad Del Zulia Faculatad De Ciencia Veterinarias Division De Investigacion
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2009
Publication Date: 12/1/2009
Citation: Chase, C.C., Jr., Vargas, C.A., Hammond, A.C., Olson, T.A., Griffin, J.L., Murphy, C.N., Tewolde, A., Fields, M. 2009. Embryo transfer in Angus and Brahman recipient cows: effect of two methods of estrus synchronization on induced estrus and pregnancy. Revista Cientifica-Universidad Del Zulia Faculatad De Ciencia Veterinarias Division De Investigacion. XIX(6):630-638.

Interpretive Summary: The success of an embryo transfer program is based on a multitude of factors including how closely the estrous cycle of the donor (at embryo collection) is associated with the recipient (or surrogate at embryo transfer). Thus, the estrous cycles of cattle are commonly synchronized using progestogen-based or prostaglandin-based protocols. These protocols were developed mostly using non-Brahman type cattle. Because we are located in the subtropics (Brahman are important) and needed a successful embryo transfer program, our objectives were to utilize two commonly used synchronization procedures (progestogen or prostaglandin) in Angus and Brahman recipients. Over a three year period 88 Angus and 87 Brahman cows were used. One-half were synchronized using prostaglandin (Lutalyse) and the other one-half using progestogen (Syncro-Mate-B). The procedure for administering prostaglandin was an injection on Days 0, 11, and 12. This sequence (three injections) differed from most protocols (two injections) in that the second shot given in most protocols was divided in one-half and administered as two shots 24 hours apart. The procedure for administering progestogen was an ear implant and injection on Day 0 and removal of the implant on Day 9. Both synchronization procedures were effective (greater than 85%) in inducing estrus in the recipients. Likewise, estrus was induced effectively (greater than 85%) in both Angus and Brahman recipients. Overall pregnancy rates to embryo transfer averaged 51.4%. The highest pregnancy rate (60%) was observed when estrus was perfectly aligned between the recipient and the donor. Misalignment of plus 24 to minus 24 hours resulted in an acceptable 51.5% pregnancy rate. Estrous cycles can be synchronized in both Angus and Brahman cows for use in an embryo transfer program culminating with acceptable pregnancy rates.

Technical Abstract: Over a 3-yr period, 88 Angus and 87 Brahman cows were used as recipients to determine the effects of breedtype and method of estrous synchronization on induced estrus and subsequent pregnancy following embryo transfer. Estrus was synchronized in recipients using either prostaglandin-F (PGF; Lutalyse) or progestogen (PRO; Syncro-Mate-B). Recipients were treated (im) with PGF on Day -11 (25 mg), 0 (12.5 mg), and 1 (12.5 mg). Recipients were treated with PRO on Day -9 (6 mg norgestomet ear implant and 2 mL (im) of 3 mg of norgestomet and 5 mg of estradiol valerate) and the ear implant was removed on Day 0. Embryos were randomly transferred to recipients synchronous +24 to -24 h with a 7-d embryo. Both synchronization methods (PGF vs PRO) were similarly effective in inducing estrus (89.8 vs 86.7%). Percentage of induced estrus was similar between Brahman (91.0%) and Angus (85.6%). Recipients treated with PGF had a longer (P = 0.001) interval to estrus than PRO treated recipients (77.4 vs 60.1 h). Estrus response in Angus was earlier (P = 0.043) than in Brahman (65.4 vs 72.2 h). Pregnancy rates in recipients closely synchronized (0 h) was 60.0%, within +12 and -12 h was 56.0%, and within +24 and -24 h was 51.5%. Four-yr-old recipients had lower pregnancy rates (34.8%) than did 5-yr-old (60.9%) or greater than 6-yr-old (70.0%) recipients. Embryo quality groups 1 and 2, had pregnancy rates of 58.9 and 38.8%, respectively (P < 0.05). Our results indicate that PGF, when administered as a split-second dose, is as effective in synchronizing estrus in Angus and Brahman as PRO. Asynchrony of embryo age with recipient stage of cycle up to +24 or -24 h did not significantly affect pregnancy rates.