Embryonic development in progestogen-supplemented cows administered prostaglandin F2a

Author

Mitchell Earl Hockett

Date of Award

10-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

F. Neal Schrick

Committee Members

Stephen Oliver, Fred Hopkins

Abstract

An experiment was performed to examine the effects of elevated concentrations of prostaglandin F_2α (PGF_2α) on embryonic development in cows supplemented with exogenous progestogen. Cows were inseminated artificially at estrus (day 0) and 12 h later. A synthetic progestogen (melengestrol acetate; 4 mg/cow*day^-1) was supplemented in feed from days 3 through 8. Cows were allotted randomly to receive either 15 mg PGF_2α (TRT; n=14) or saline (CON; n=10) at 0600, 1400 and 2200 h from days 5 through 8. Blood samples were collected at 0600 and 2200 h from days 5 day 8 for determination of progesterone and 13,14-dihydro-15-keto- PGF_2α, (PGFM) . Single embryos were recovered on day 8 by flushing the uterine horn ipsilateral to the corpus luteum (CL) as determined by ultrasonography on day 5. Each embryo was assigned a quality score of 1 (excellent) to 4 (poor), and stage of embryo development was recorded. Concentrations of progesterone were lower from days 5 to 8 in TRT versus CON cows (0.3 ± 0.14 vs 2.01 ± 0.16 ng/mL, respectively; P=0.0001). Overall, PGFM concentrations from days 5 to 8 were elevated in TRT cows (553.2 ± 42.1 pg/mL) compared to CON cows (13.2 ± 50.1 pg/mL; P=0.0001). Embryo quality scores were elevated in TRT cows compared to CON cows (2.9 vs 1.6, respectively; P=0.059). Percentage of embryos considered transferrable (quality scores 1, 2, and 3) was decreased by administration of PGF_2α (Fisher's exact test, P=0.003). Nine of fourteen (64%) TRT embryos were retarded in development at day 8, whereas four of fourteen (29%) TRT embryos developed to expanded blastocyst. All CON embryos developed beyond the morula stage; eight of ten (80%) developed to the expanded blastocyst and two of ten (20%) reached the blastocyst stage upon recovery (Fisher's exact test, P=0.003).

In conclusion, treatment of progestogen-supplemented cows with PGF_2α reduced quality and retarded development of embryos prior to the blastocyst. Decreased fertility in conditions elevating PGFM concentrations may be a result of retarded development or reduced quality by PGF_2α.

Recommended Citation

Hockett, Mitchell Earl, "Embryonic development in progestogen-supplemented cows administered prostaglandin F2a. " Master's Thesis, University of Tennessee, 1998.
https://trace.tennessee.edu/utk_gradthes/6736