Biomedical subjects

E K Inskeep

Publications and source records attributed to E K Inskeep.

At least 37 records · Page 2Linked to original sources

PubMed1997

Relationships of hormonal patterns and fertility to occurrence of two or three waves of ovarian follicles, before and after breeding, in beef cows and heifers.

Ovarian follicular waves were characterized before and after breeding in 52 lactating beef cows and 16 heifers. Effects of two (2 W) or three (3 W) waves of follicular development and associated patterns of concentrations of steroids in jugular serum on pregnancy rate were examined. Animals were observed for oestrus (= day 0) twice daily and inseminated artificially at second oestrus. Follicular development was monitored by ultrasonography and jugular blood samples were collected simultaneously on alternate days from day 6 after first oestrus until ovulation after the second oestrus and from day 6 after second oestrus (insemination) until next ovulation or day 24 of pregnancy. Pregnancy was determined by ultrasonography at 25 days after insemination. From individual patterns of growth or regression of the largest follicles, more of the 59 animals with oestrous cycles of 17 to 25 days had 2 W (51, 86%) than 3 W (8, 14%) during the oestrous cycle before breeding (P < 0.01). Cycles averaged 1.1 days longer (P < 0.10) and corpora lutea regressed later (P < 0.01) in animals with 3 W vs. those with 2 W, but mean oestradiol between 7 and 2 days before second oestrus (3.7 +/- 0.3 pg ml-1) did not differ between cycles with 2 W or 3 W. Ovulatory follicles in animals with 2 W differed from those with 3 W (P < 0.05) in day of detection (12.3 +/- 0.3 vs 16.5 +/- 0.5), growth rate (1.0 +/- 0.1 vs 1.5 +/- 0.1 mm day-1), interval from detection to ovulation (9.3 +/- 0.3 vs 6.3 +/- 0.7 days) and duration of dominance (4.0 +/- 0.2 vs 2.1 +/- 0.6 days). Pregnancy rates, 82% in cows with 2 W and 100% in cows with 3 W, did not differ (P > 0.05). During the period equivalent to an oestrous cycle after breeding, 29 (49%) of the 59 animals had 2 W and 30 (51%) had 3 W. Fewer animals with 2 W than 3 W after breeding became pregnant (16/23, 70% vs 26/27, 96%; P < 0.05), but patterns of concentrations of progesterone on days 6 through 14 or mean oestradiol on day 14 (2.6 +/- 0.2 pg ml-1) did not differ. In conclusion, fewer animals had 3 W than 2 W before breeding and fertility did not differ. During the equivalent of one oestrous cycle after breeding, approximately equal numbers of animals had 2 W or 3 W and fertility was greater for animals with 3 W.

Animals↗

PubMed1997

Ultrasonographic monitoring of antral follicle development in red deer (Cervus elaphus).

Ovarian follicular dynamics were monitored in 12 surgically modified red deer hinds (ovaries adhered to vaginal wall) by transvaginal real-time ultrasonography during the luteal cycle, anoestrus and induction of superovulation. All 12 hinds showed evidence of regular luteal (plasma progesterone) cyclicity during the breeding season, although luteal tissue was not observed on the ultrasonograms. During the normal luteal cycle (14-22 days) total numbers of follicles > 3 mm did not vary significantly by day (range of means: 1.8-3.4; P > 0.05). A single large (> or = 6 mm) follicle was usually present on all days except immediately after ovulation (day 0). However, the appearance of new follicles (> or = 3 mm) was not random, and was greatest on day 1 and day 14 (P < 0.05). Tracking of individual follicles revealed irregular waves of emergence and disappearance of the largest follicle, with either one (n = 1), two (n = 3) or three (n = 5) waves observed across nine luteal cycles. New follicles (> or = 3 mm) emerged after regression or ovulation of a large follicle, suggesting a dominance effect. There were no significant differences in the overall mean numbers of follicles during early, mid- and late anoestrus (September, November and April, respectively) but follicle turnover was more rapid during mid-anoestrus as evidenced by a significantly greater number of new small (> 3 mm) follicles (P < 0.001). Administration of superovulatory doses of ovine FSH during the breeding season resulted in a marked increase in the appearance of new follicles within 48 h of initiation of the injection regimen. By termination at 96 h, the time of progesterone withdrawal, the mean number of follicles > 3 mm was significantly higher than for control hinds (9.8 versus 3.0; P < 0.0001). While most follicles ovulated progressively 2-7 days later, about 40% persisted beyond this period. The study demonstrated the presence of discrete patterns of antral follicle growth and regression during the breeding and non-breeding seasons, with the luteal cycle characterized by a variable number (1-3) of dominant follicle waves. Anoestrus represents a period of dynamic changes in follicular turnover.

Anestrus↗

PubMed1997

Estrus and luteal function in suckled beef cows that were anestrous when treated with an intravaginal device containing progesterone with or without a subsequent injection of estradiol benzoate.

The objectives in this study were to determine whether treatment with progesterone (P4) via an intravaginal device would induce estrus and development of corpora lutea (CL) with typical life spans and whether treatment with estradiol benzoate (EB) following device removal would enhance the responses. At treatment initiation (d 0), suckled beef cows (n = 362) that were anestrous received one of the following: 1) an intravaginal device containing P4 for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (P4+EB), 2) an intravaginal device containing P4 for 7 d (P4), 3) a sham device for 7 d plus an injection of 1 mg of EB 24 to 30 h after device removal (EB), or 4) a sham device for 7 d (control). Progesterone treatment increased the proportion of cows that formed CL with a typical lifespan (P < .001) and exhibited behavioral estrus (P < .05). Treatment with EB in combination with P4 increased (P < .001) the proportion of cows that exhibited estrus. Treatment with P4 alone had no effect, but the combination of P4 and EB increased (P < .01) the proportion of cows that formed short-lived or typical lifespan CL by the end of the experiment compared with untreated cows. In summary, treatment with P4 increased the incidence of estrus and the proportion of cows that formed CL with a typical lifespan. Treatment with P4 resulted in resumption of luteal function in suckled beef cows that were anestrous, with most cows developing CL with a typical lifespan, whereas EB enhanced the expression of estrus.

Administration, Intravaginal↗

PubMed1996

Effect of peripheral concentrations of progesterone on follicular growth and fertility in ewes.

The effects of progesterone (P4) on follicular growth and fertility in ewes were examined. In Experiment 1, 22 ewes received either one or three packets of P4 (5 g/packet) or an empty packet subcutaneously (sc) from Days 5 to 15 of the estrous cycle (estrus = Day 0). On Day 6, P4-treated ewes received 12.5 mg of prostaglandin F2 alpha. Follicles > or = 3 mm in diameter were observed via transrectal ultrasonography daily from Day 4 through estrus, corpora lutea (CL) were observed 5 to 7 d after estrus. Ewes with low (LOW; < or = 1 ng/ml; n = 5), intermediate (MED; >1 and <2 ng/ml; n = 10), or normal (NOR; > or =2 ng/ml; n = 7) P4 in jugular plasma on Days 7 through 15 differed in follicular development. The largest follicle at estrus was larger in ewes with LOW vs. MED and NOR P4 (7.8 +/- 0.3 vs. 6.9 +/- 0.2 mm; P < 0.05). Treatments differed in proportions of multiple-ovulating ewes, in which the oldest ovulatory follicle was first observed before Day 10 (LOW: 3 of 3, MED: 6 of 10, NOR: 0 of 5, respectively; P < 0.05). Estradiol was higher early in the treatment period in LOW ewes than in MED and NOR ewes (day x treatment; P < 0.05). In Experiment 2, ewes received 5 mg of P4 in corn oil (low progesterone [LP]; n = 51) or 2 ml of corn oil (CON; n = 49) sc every 12 hr on Days 6 through 14 of the estrous cycle before mating. LP ewes received 15 mg of prostaglandin F2 alpha on Day 6. Mean serum P4 on Days 7 through 15 was 0.6 +/- 0.1 ng/ml in LP and 1.9 +/- 0.1 ng/ml in CON ewes. Eleven LP and 12 CON ewes were scanned daily from Day 4 through mating, and in all ewes (n = 93), CL were counted 10 d after mating and embryos were counted at 25, 40, and 60 d of gestation. In multiple-ovulating ewes, day of cycle of appearance was earlier for the oldest (Day 6.1 +/- 0.8 vs. 10.4 +/- 0.8) but not second oldest (Day 11.7 +/- 1.0 vs. 12.2 +/- 0.9) ovulatory follicles in LP compared with CON ewes. The conception rate was lower in LP (72%) than in CON ewes (98%; P < 0.01). However, numbers of CL 10 d after mating, and in pregnant ewes, numbers of embryos 25 d after mating and lambs born, did not differ with treatment. In summary, low P4 increased the size of the largest follicles and the age of the oldest ovulatory follicles. Embryos resulting from the ovulation of older and younger follicles in the same ewe did not differ in their ability to survive.

Animals↗

PubMed1996

Protein sources affect follicular dynamics in ewes near the onset of the breeding season.

The influence of source of protein during the luteal phase before a synchronized oestrus on the dynamics of follicular development, observed daily by ultrasonography, was assessed in ewes that were beginning the sexual season. Iso-nitrogenous amounts of soybean meal (SBM) or of a corn-gluten meal-ground-corn grain mixture (CGM-GC), or an iso-energetic amount of ground-corn grain (GC), were fed from four days before to four days after treatment with prostaglandin F2 alpha (PGF2 alpha). Feeding with SBM was associated with a higher frequency of short luteal phases (P < 0.02). Dynamics of follicular population were studied in ewes that ovulated after normal cycles. More follicles > or = 2 mm in diameter were observed on the ovaries of ewes fed SBM four days before PGF2 alpha treatment (P < 0.02), but the highest number was seen in ewes fed CGM-GC at the time of injection of PGF2 alpha (P < 0.08). Ewes fed SBM had larger follicles at last detection and ovulated earlier after PGF2 alpha treatment than their counterparts fed other diets (P < 0.001). Ovulatory follicles developed over a greater range of days in ewes with twin ovulations compared with ewes with single ovulations (P < 0.08). Serum concentrations of insulin were increased after four days of feeding with CGM-GC (P < 0.01), but not with SBM or GC, and reached a peak at the time of oestrus. In summary: (1) the source of dietary protein during the late-luteal phase affected follicular maturation after PGF2 alpha treatment; (2) insulin and glucose may be involved in this response and may play a role in ovarian follicular activity; and (3) twin ovulations appeared to result from both reduced atresia and increased recruitment of follicles.

Analysis of Variance↗

PubMed1996

Embryotoxicity of a regressing corpus luteum in beef cows supplemented with progestogen.

Postpartum cows with short-lived corpora lutea produce embryos that arrive at the uterus, but pregnancy rates are low even with exogenous progestogen. Four experiments were conducted to determine whether prostaglandin (PG) F2 alpha, known to cause early luteolysis, could have a direct effect on embryonic loss. Exogenous progestogen was injected s.c. twice daily in each experiment, starting 3 or 4 days after estrus (day of estrus = Day 0). Nonlactating, cycling beef cows were mated and injected i.m. every 8 h on Days 4 through 7 (experiment 1) or 5 through 8 (experiment 3) with either 15 mg PGF2 alpha or 3 ml saline. In experiment 1, cows in a third group received 1 g flunixin meglumine i.m. every 8 h. Ten of 18 PGF2 alpha-treated cows in experiment 3 were luteectomized on Day 5. Pregnancy rates were higher (p < 0.05) in cows given saline or flunixin meglumine (5 of 7) than in cows given PGF2 alpha (1 of 5) in experiment 1, and in cows given saline (6 of 9) or given PGF2 alpha, and luteectomized (8 of 10) than in cows given PGF2 alpha (2 of 8) in experiment 3. Postpartum beef cows, mated at weaning-induced first estrus, received i.m. injections every 8 h on Days 4 through 9 of 3 ml saline or 1 g flunixin meglumine (experiment 2); 14 flunixin meglumine-treated cows were luteectomized on Day 7. Pregnancy rates were higher in cows given flunixin meglumine and luteectomized (7 of 14) than in cows given saline (4 of 15) or flunixin meglumine alone (3 of 15; p < 0.05). In experiment 4, postpartum cows were luteectomized or sham-operated on Day 5. Pregnancy rates (2 of 13 and 2 of 14, respectively) did not differ. Thus, both reduction of endogenous PGF2 alpha and luteectomy were required for embryo survival in postpartum cows with short-lived corpora lutea, whereas luteectomy alone prevented effects of exogenous PGF2 alpha in cycling cows.

Animals↗

PubMed1996

Exogenous pulses of luteinizing hormone cause persistence of the largest bovine ovarian follicle.

The objectives of this study were, 1) to determine whether increased frequency of LH pulses, independent of changes in progesterone, will cause persistence of the first largest ovarian follicle (LF1) during the bovine estrous cycle and 2) to determine whether a follicle produced in this manner will ovulate after luteal regression. In Exp. 1, 32 nonlactating beef cows were randomized into four groups. Bovine LH was given as 50 micrograms i.v. every 2 h from 0800 on d 7 through 0800 on d 13 postestrus to cows in two groups, which in addition either received PGF2 alpha on d 12 and were allowed to ovulate (LHOV; Group 1) or were ovariectomized (LHOVX; Group 2) on d 13. Cows in Group 3 received progesterone via a used controlled internal drug releasing device (CIDR) on d 4 to 13, PGF2 alpha on d 6, and ovariectomy on d 13. These cows received 1 mL of saline i.v. every 2 h on d 7 to 13, as did those in Group 4 (SAL), but cows in Group 4 did not receive any PGF2 alpha. Proportion (percentage) of LF1 maintained until d 13 was similar in cows with CIDR (100) and on LH (88) but less in cows on SAL (36; P < .01). The LF1 were largest in cows with CIDR, smallest in cows on SAL, and intermediate in cows on LH (P < .001). During d 7 to 13, progesterone was lesser and estradiol was greater in peripheral plasma in cows with CIDR than in cows on LH or SAL (P < .001). In Experiment 2, beef heifers received 50 micrograms of bLH (LH; n = 5) or saline (SAL; n = 4) i.v. every 2 h from 0800 on d 7 until 12 h after signs of estrus were observed following PGF2 alpha on d 12. The LF1 were maintained by LH and 60% ovulated; all LF1 were replaced during treatment in heifers on SAL. The LF1 were larger in heifers on LH, but estradiol and progesterone did not differ between groups. In conclusion, an increased frequency of LH pulses during a normal luteal phase allowed LF1 to persist but did not increase secretion of estradiol.

Animals↗

PubMed1995

Effect of persistent follicles on early embryonic losses in beef cows.

Low doses of progestogens in regimens for synchronization of estrus result in persistent follicles (PF) and reduced conception rates in cattle. The effects of PF on recovery of oocytes/embryos, fertilization, and embryonic development were examined in beef cows. To produce PF, cows received a used Controlled Internal Drug Releasing device on Days 4 through 13 after pretreatment estrus (Day 0) and two injections of 20 mg prostaglandin (PG) F2 alpha, i.m., 12 h apart on Day 6 (PF; n = 20). Control cows received only PGF2 alpha on Day 6 so they would ovulate growing follicles (GF; n = 22). With this model, the largest (dominant) follicle from the first wave of follicular development was being ovulated in cows in each group. Cows were observed for estrus twice daily and were then mated to highly fertile bulls. Follicular development was monitored by ultrasonography on alternate days from Day 2 until estrus and then daily until apparent ovulation. Jugular blood samples were collected every other day from Day 2 through 6 days after mating at posttreatment estrus, when uteri were flushed nonsurgically. The ovulatory follicle, which was followed retrospectively and had been observed longer (14 +/- 1 vs. 8 +/- 1 days), was larger in PF (17.2 +/- 0.5 mm) than in GF (14.5 +/- 0.6 mm; p < 0.01). Mean estradiol-17 beta (E2) in jugular plasma during the 6 days before estrus was higher in PF than in GF (5.7 +/- 0.4 vs. 2.6 +/- 0.4 pg/ml; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Day of estrous cycle affects follicular dynamics after induced luteolysis in ewes.

Effects of day of estrous cycle and induced luteal regression on follicular dynamics in ewes were examined. In Exp. 1, ewes received PGF2 alpha (i.m.) on d 5, 8, or 11 after estrus (d 0) or saline on d 14 (n = 27, 27, 31, and 29, respectively). Ewes were laparotomized before treatment and again 48 h after induced estrus to record numbers, sizes, and locations of follicles > or = 2 mm and corpora lutea (CL). The two largest follicles (designated F1 and F2) and any of equal size (F1.5 and F2.5) were marked with India ink in stroma around the follicle. Ewes treated on d 8 ovulated fewer F1 and F1.5 (39%) than ewes treated on d 5 (69%; P < .05); d 11 (51%) and 14 (56%) were intermediate. In Exp. 2, ewes received PGF2 alpha on d 5 or 8 (n = 15/d). Ovaries were examined with transrectal ultrasonography daily from 4 d before PGF2 alpha until ovulation, and on d 5 and 8 after ovulation. Diameters, locations, and ranks (at time of PGF2 alpha) of follicles > or = 2 mm and CL were recorded. Ewes treated on d 8 ovulated fewer F1 and F1.5 (35%) than ewes treated on d 5 (86%; P < .05). Ovulatory follicles at time of PGF2 alpha were larger on d 5 (4.7 +/- .2 mm) than on d 8 (4.0 +/- .2 mm; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Factors that affect fertility during oestrous cycles with short or normal luteal phases in postpartum cows.

We have used a model to study infertility in postpartum cows. In mated cows with short luteal phases, daily supplementation with progestagen, beginning on day 3, failed to maintain pregnancy, despite the fact that fertilization, early embryo development and transport of the embryo into the uterus appeared to be normal. Normal embryos were transferred, on day 7 after oestrus, into cows with short luteal phases that received daily supplementation with progestagen, and embryos from cows with short luteal phases were transferred, on day 6 after mating, into cows with normal cycles. Pregnancy rates in each case were about half those achieved using progestagen-pretreated cows with normal luteal phases. In mated cows with short luteal phases supplemented with progestagen, pregnancy rates were markedly improved by removal of the regressing corpus luteum on day 4 or 5 after mating. In cows with normal cycles, fertility was lower when preovulatory concentrations of oestradiol were high for more than 3 days. This may result from persistent follicles, which develop when progesterone is low and frequency of tonic pulses of LH is high. In cows with such follicles, oocytes may resume maturation before the surge of LH, and embryos died in the oviduct before the 16-cell stage. Finally, in both early postpartum cows with transferred embryos and cows with normal cycles, excessive follicular development and high oestradiol during the luteal phase were detrimental to embryo survival. Treatments designed to maximize fertility in early postpartum cows must provide high progesterone and low oestradiol before mating and not yield luteolytic influences such as PGF2 alpha and oestradiol, both early after mating and during maternal recognition of pregnancy.

Animals↗

PubMed1994

Relationship of pregnancy rate to peripheral concentrations of progesterone and estradiol in beef cows.

The relationship between pregnancy rate and concentrations of progesterone (P(4)) and estradiol-17beta (E(2)) in serum was examined in inseminated beef cows. Jugular blood was collected twice daily on Days 4 through 7 and Days 14 through 17 after estrus to establish patterns of secretion of P(4) and E(2). Pregnancy rate was determined by palpation per rectum at 45 d. Mean concentrations of each hormone, ratio of E(2):P(4) and regressions of hormone on day were the variables measured for each of the 2 periods. Cows were classified into low (n=26), medium (n=50) and high (n=26) groups for each variable. The relationship of pregnancy rate to each variable was tested using Chi-square analyses. Pregnancy rates to the first service decreased linearly as relative mean concentrations of E(2) increased on Days 14 through 17 (P<0.05) but were not affected by any of the other hormonal variables studied during either period. Pregnancy rates to the second service were not related to concentrations of P(4) or E(2) during the luteal phase before mating (Days 14 through 17). The effects of pregnancy on concentrations of E(2) and P(4) also were tested. On Days 14 through 17, P(4) increased slightly in pregnant cows and declined slightly in nonpregnant cows (P<0.05), but pregnancy did not affect E(2) during either period or P(4) on Days 4 through 7. In summary, pregnancy rate to the first service decreased significantly as concentrations of E(2) increased on Days 14 through 17.

Journal Article↗

PubMed1993

Determination of early pregnancy in ewes utilizing transrectal ultrasonography.

Transrectal ultrasonography was used in ewes to determine the earliest day at which pregnancy could be detected, the number of embryos present, and the pattern of growth of the embryos. Twenty-one ewes were placed with 2 fertile rams and 20 ewes with 2 vasectomized rams. All ewes were treated to synchronize estrus and were observed for estrus twice daily. The 36 ewes that showed synchronized estrus were separated from the rams following mating. Transrectal ultrasonography was performed daily from estrus (Day 0) to Day 25 for all ewes and on Days 30, 35 and 40 post breeding for the 20 ewes mated to fertile rams. A 7.5 MHz transducer (human prostate, linear array) was utilized, with the ewes in dorsal recumbency in a tilting squeeze chute. Extraembryonic fluid and membranes were observed in the uterine horns ipsilateral to corpora lutea by Day 15 post breeding in all 17 ewes subsequently diagnosed as pregnant. Rhythmic pulsations (heartbeat) within the embryonic vesicles were first detected on Day 18 or 19. At least 1 embryo was detected by Day 20 in all the pregnant ewes, but not all the embryos were counted accurately until Day 25 (main effect of day; P < 0.05). Two ewes each had an embryo which died (absence of previously observed heartbeat) by Day 25 or Day 40, respectively, but each maintained the remaining embryos to term. The pattern of embryonic growth, as determined by crown-rump lengths on Days 20, 25, 30, 35 and 40, did not differ with the number of embryos carried (n = 1 to 4). In conclusion, transrectal ultrasonography was found to provide a rapid, accurate means for the early detection of pregnancy in ewes.

Journal Article↗

PubMed1993

Factors affecting fertility in the postpartum cow: role of the oocyte and follicle in conception rate.

Four experiments were designed to examine the contribution of the oocyte or the follicular, oviductal, or early uterine environments to low fertility associated with the first ovulation postpartum. At 17-25 days postpartum in experiments 1, 2, and 3, suckled beef cows were assigned at random to receive 6 mg norgestomet, via ear-implant, for 9 days (NOR) or to serve as controls (CON). Calves were weaned from all cows 7 days after assignment to treatment in order to induce estrus, an LH surge, ovulation, and subsequent formation of CL. As cows were detected to be in estrus, they were bred first by natural service and 12 h later by artificial insemination. In experiment 1, on Day 3 after estrus, the oviduct ipsilateral to the side of ovulation was removed and flushed for recovery of an embryo or oocyte. Rates of recovery (86%), fertilization (68%), and development of fertilized oocytes to the 4- to 8-cell stage (100%) did not differ between CON and NOR cows. In experiment 2, uteri were flushed nonsurgically on Day 6 after estrus. Rates of recovery of embryos from the uterus were similar between CON (86%) and NOR (71%) cows. In experiment 3, one half of the cows in each group (CON and NOR) were fed melengestrol acetate (MGA) beginning on Day 4 after estrus and continuing until Day 35. The remaining cows in each group served as controls. Treatment with NOR increased (p < 0.05) the proportion of cows that maintained pregnancy until Day 35 (9/22) as compared to controls (0/18).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Pregnancy rates for embryos transferred from early postpartum beef cows into recipients with normal estrous cycles.

Survival rate of embryos from first ovulations of postpartum cows with SHORT (6.9 +/- 0.3 days; n = 35) or NORMAL (17.1 +/- 0.3 days; n = 42) luteal phases and quality of the embryos on Day 6 were compared. At 19 to 23 days postpartum, cows were allotted to receive a norgestomet implant for 9 days (normal luteal phase) or to serve as untreated controls (short luteal phase). Calves were weaned 7 days after initiation of treatment to induce behavioral estrus in cows for mating. In 25 cows, growth of the ovulatory follicle was monitored by ultrasonography. On Day 6 after estrus, embryos were recovered nonsurgically, and live embryos were transferred into recipient cows exhibiting normal estrous cycles. The medium used to flush the embryos from the uterus of each donor cow was assayed for prostaglandin F2 alpha (PGF2 alpha). Days from calf removal to estrus and size of ovulatory follicles at ovulation (4.1 +/- 0.3 days and 16.7 +/- 0.7 mm, respectively) did not differ between NORMAL and SHORT cows. Interval from detection of the ovulatory follicle to ovulation was longer in NORMAL (10 +/- 0.7 days) than in SHORT cows (8 +/- 0.6 days; p < 0.05). Rates of recovery of an embryo or ovum (64%), rates of fertilization (65%), and quality or stage of development of Day 6 embryos did not differ between SHORT and NORMAL cows. Overall pregnancy rate from recovered oocytes was 13% for SHORT and 32% for NORMAL cows (p = 0.06); survival of fertilized oocytes was 23% for SHORT and 47% for NORMAL cows (p = 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Ovarian structures during the estrous cycle and early pregnancy in ewes.

The development of ovarian follicular and luteal structures during the estrous cycle and early pregnancy in ewes was examined. Ewes were treated with prostaglandin F2 alpha to induce estrus; they were placed with either two fertile or two vasectomized rams and observed for estrus twice daily. Beginning at estrus (Day 0), ovaries were scanned for CL and for follicles > or = 2 mm by transrectal ultrasonography daily for the first 25 days of pregnancy (PREG, n = 17 ewes) or until Day 8 of the second estrous cycle (CYC, n = 15 ewes). Jugular blood samples were collected at ultrasonography and on Days 30, 35, and 40 of gestation for RIA of progesterone and estradiol-17 beta. Total follicles (17.6 +/- 1.3), number of follicles > or = 4 mm in diameter (11.3 +/- 0.6), and number of follicles that became the largest during the first 16 days of pregnancy or the first estrous cycle (4.9 +/- 0.3) did not differ between PREG and CYC ewes. Number of newly detected follicles each day and difference in mean diameter between the largest two follicles and all other follicles were similar between PREG and CYC ewes until luteal regression. At that time, difference in diameter between the largest two follicles and all other follicles increased in CYC ewes in parallel with estradiol-17 beta in serum. Mean concentrations of progesterone in serum were higher in PREG than in CYC ewes (2.4 +/- 0.1 vs. 2.0 +/- 0.1 ng/ml; p < 0.05) before onset of luteal regression, but mean areas of CL did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Endocrine profiles and follicular development in early-weaned postpartum beef cows.

This study investigated whether treatment with progestagen, which improves fertility after early weaning in postpartum cows, altered concentrations of gonadotrophins or development and function of follicles. Patterns of luteinizing hormone (LH), oestradiol and follicle-stimulating hormone (FSH) and of follicular growth before first postpartum ovulation were compared in two experiments. At 17 to 25 days post partum, suckled anoestrous beef cows received an ear-implant containing 6 mg progestagen (norgestomet) for 9 days or served as untreated controls. Calves were weaned from all cows 7 days after initiation of treatment. Cows were observed for oestrous behaviour twice a day until 10 days after weaning. As expected, the proportion of anoestrous cows that formed a corpus luteum with a normal lifespan was greater (P < 0.01) in cows treated with norgestomet (Expt 1, 17 of 24; Expt 2, 18 of 22) than in control cows (Expt 1, 2 of 16; Expt 2, 3 of 18). In general, patterns of secretion of LH and oestradiol and of final growth of the preovulatory follicle did not differ between control and norgestomet-treated cows. However, there was a transient rise in FSH in association with weaning in control cows that did not occur in norgestomet-treated cows. In addition, mean LH increased more rapidly and mean oestradiol was higher during the 3 days immediately before the preovulatory surge of LH in the norgestomet-treated cows (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Modification by propylene glycol of ovulation rate in ewes in response to a single injection of FSH.

Five experiments were conducted with the objective of developing a method to induce superovulation in ewes with a single i.m. injection of FSH. This was achieved by injection of 10 mg FSH-P in propylene glycol at the same time as luteolysis was induced by cloprostenol on day 13 of the oestrous cycle (day 0 = oestrus). Experiments 1, 2, 3 and 5 were conducted in a single flock of Manchega ewes in Spain during the breeding season. Ovulation rates were determined at laparoscopy. In Expt 1, FSH-P was diluted in saline, and neither 5 mg FSH on day 1 nor 5 or 10 mg FSH-P on day 13 changed the ovulation rate after cloprostenol treatment on day 13. In Expt 2, FSH-P was diluted in propylene glycol and data were collected over 2 years. Ten milligrams FSH-P, on day 13 only, increased (P < 0.01) the mean number of corpora lutea to 5.5 compared with a control value of 1.5. Five milligrams FSH-P on day 13 only had no effect; however, 5 mg FSH-P on day 1 reduced the mean number of corpora lutea formed in ewes receiving 10 mg FSH-P on day 13 to 2.6 (P < 0.01). Saline and propylene glycol, as vehicles for 10 mg FSH-P, were compared directly at two times of injection in Expt 3. FSH-P increased the mean number of corpora lutea when injected on day 13 in propylene glycol (4.7) but not in saline (2.5; P < 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Influence of the corpus luteum of pregnancy on ovarian function in postpartum ewes.

This study was conducted to determine the effects of the corpus luteum (CL) of pregnancy and(or) the previously gravid uterine horn (g-UH) on the incidence and site of ovulation and the duration of luteal function in postpartum (PP) ewes. Ewes were laparotomized at d 60 to 80 of gestation and assigned to one of four groups: 1) single g-UH, CL left intact (SI, n = 35); 2) single g-UH, CL removed (SR, n = 30); 3) twin g-UH, CL on both ovaries left intact (TI, n = 21); and 4) twin g-UH, CL removed from one ovary (TR, n = 32). On d 20 PP, the number of follicles on each ovary was determined at laparoscopy, and ewes received (i.m.) 750 IU of hCG. Ovarian structures were determined at laparoscopy on d 24 PP. Blood samples were collected daily from d 20 to 40 PP and assayed for progesterone. more follicles (P < .05) were observed at laparoscopy on d 20 PP in SI/TI than in SR/TR groups (8.4 vs 6.0, respectively; SE = .4). Overall, 52% of the ewes had visible CL 4 d after hCG, and 73% of the ewes had elevated levels of progesterone by 7 d after hCG. The number of g-UH (S vs T) or status of the CL (I vs R) did not affect these responses. For SR ewes with hCG-induced CL on a single ovary, the incidence of CL formation on the ovary adjacent to g-UH was less (P < .05) than that for SI ewes (0 vs 57, respectively). Removal of the CL from S ewes, but not from T ewes, reduced follicular development and ovulation in response to hCG. Perhaps there is a positive systemic effect of the CL of pregnancy on postpartum ovarian function in ewes.

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