Project Number: WVA00321
CRIS Number: 0130690
Multi-State Project: NE-161
ASSOCIATION OF FERTILITY WITH TEMPORAL CHANGES IN OVARIAN FUNCTION OF DOMESTIC RUMINANTS
Investigators: Inskeep, E. K., Dailey, R. A., Lewis, P. E.
Performing Department: Animal & Veterinary Science -- 1877
Start Date: 10/01/1996
Termination Date: 09/30/2002
Reporting period: 01/01/2001 to 12/31/2001
Progress Report:
Effects of treatment with PGF2alpha during the early and mid-luteal phases on three components of the endothelin system: endothelin-converting-enzyme-1 (ECE-1), ET type A receptors (ETA) and ET-1 were examined in the bovine CL. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to evaluate the mRNA encoding ECE-1, ETA and ET-1. The ECE-1 and ETA proteins were evaluated by semi-quantitative Western Blotting. ET-1 mRNA was increased significantly by 2 h after the second of a series of injections of PGF2alpha 8 h apart on Day 10 and remained 66 and 54% higher at 24 and 48 h, but did not change in CL of cows treated on Day 4. Expression of the ETA and ECE-1 genes did not differ in the Day-4 and Day-10 CL and was not influenced by treatment with PGF2alpha. Patterns of progesterone in serum and other characteristics of the cow were studied as predictors of pregnancy maintenance during the period from day 30 to day 60 after breeding in dairy cows (N = 211) on 2 farms. Overall rate of late embryonic and early fetal morality was 10.9% (13% on farm 1 and 7% on farm 2). Late embryonic (Day 45 of gestation) losses accounted for 65.2% and 34.8% of total losses, respectively. Cows with two CL maintained fewer pregnancies than cows with a single CL (73.7 vs. 91%; p < 0.01). Pregnancy loss prior to Day 45 was greater (p < 0.01) in cows with low serum concentrations of progesterone at 28 to 37 days of gestation. Pregnancy loss after Day 45 was not related to concentrations of progesterone. Cows that were fattest (BCS 3.5 or greater) failed to maintain pregnancies more often than cows with BCS 3.25 or less (p < 0.05). In ewes, fetal mortality (from Day 45 to term; 14%) was greater than late embryonic mortality (from Day 25 to Day 45; 4%). Losses occurred throughout pregnancy, included both complete loss of the pregnancy and loss of one or more embryos or fetuses from a multiple pregnancy without complete loss, and lead to fewer twins born than were present at pregnancy diagnosis. Treatment with 154 mg long acting recombinant bovine growth hormone 2 days before breeding increased (P < 0.001) both free (4.37 plus or minus .68 vs .70 plus or minus .04 ng/ml) and total (490 plus or minus 5 vs 177 plus or minus 13 ng/ml) circulating IGF-I 6 days after estrus (8 days after injection). This treatment tended to increase (P < 0.07) birth weight of lambs (4.5 plus or minus .2 vs 5.1 plus or minus .2 kg) without increasing incidence of dystocia. Treatment of ewes on days 5 and 6 of gestation with 500 micrograms (but not 125 and 250 micrograms) of estradiol-17 beta increased uterine luminal IGF-I content when compared to controls (P < .05; 14.4 plus or minus 2.5 ng vs 8.4 plus or minus 1.5 ng). Further studies of effects of growth hormone and estradiol on conception rates and embryonic growth and survival have been initiated in both dairy and beef cows and in ewes.
Publications:
Knights, M., T. Hoehn, P. E. Lewis and E. K. Inskeep.2001 Effectiveness of intravaginal progesterone inserts and FSH for inducing synchronized estrus and increasing lambing rate in anestrous ewes. J. Anim. Sci. 79:1120-1131.
Knights, T. D. Maze, P. J. Bridges, P. E. Lewis, E. K. Inskeep. 2001 Short-term treatment with a controlled internal drug releasing (CIDR) device and FSH to induce fertile estrus and increase prolificacy in anestrous ewes. Theriogenology 55:1181-1191.
Wright, M. F., B. Sayre, E. K. Inskeep and J. A. Flores. 2001 Prostaglandin F2a regulation of the bovine corpus luteum endothelin system during the early and midluteal phase. Biology of Reproduction 65:1710-1717.
Costine, B. A., B. L. Sayre and E. K. Inskeep. 2001 Embryotoxicity of a regressing corpus luteum in the ewe. Reproduction 122:883-887.
Costine, B. A. 2000 Evidence for a systemic embryotoxic effect of early luteal regression in the ewe. M. S. Thesis. West Virginia University.
Candler, J. B. 2001 Effect of concentrations of progesterone on follicular development and fertility in beef cows. M. S. Thesis. West Virginia University.
Impact:
Findings in this project to date have opened the possibility that late embryonic and early fetal mortality in cattle can be overcome by methods to increase luteal function during the period of attachment and placentation of the conceptus, Days 30 to 40 of gestation. We now have a basis to propose further work to delineate the causes of reduced luteal function during that period and to evaluate the roles of the conceptus and the dam in determination of pregnancy retention or loss after Day 30 of pregnancy.