Estradiol production by preimplantation blastocysts and increased serum progesterone following estradiol treatment in llamas

Estradiol is a potential candidate for the blastocyst signal responsible for maternal recognition of pregnancy in the llama (Lama glama). Two experiments were conducted to determine if the llama blastocyst produces estradiol during the presumed period of maternal recognition of pregnancy and if exogenous estradiol can extend the luteal phase. In Experiment 1, llamas were superovulated with eCG and mated 7 days later (Day 0=day of mating). Blastocysts were collected nonsurgically on Days 7, 9, or 11 or at necropsy on Days 13 and 15 post-mating and cultured for 48h. Conditioned medium was recovered, replaced with fresh medium at 24-h intervals, and assayed for estradiol-17beta. Estradiol production (pg/blastocyst) over the 48-h culture increased (P<0.05) by day of gestation where more estradiol (P<0.05) was produced by Day 11 compared to Day 7 blastocysts, Day 13 compared to Days 7-11 blastocysts, and Day 15 compared to Days 7-13 blastocysts. A dramatic increase was observed between Days 11 and 13 when estradiol production by Day 13 blastocysts increased (P<0.05) more than 50-fold. In Experiment 2, 30 females were induced to ovulate with hCG (Day 0=day of hCG injection). Starting on Day 7 and continuing through Day 15, animals received daily injections i.m. of 0 (n=11), 5 (n=7), or 10mg (n=12) estradiol benzoate (EB) dissolved in isopropylmyristate. Sera were collected immediately prior to each injection and on Days 16, 17, 18, 20, and 22 and analyzed for progesterone. Progesterone concentrations were greater (P<0.05) on Days 14, 15, 16, and 17 in llamas treated with 10mg EB compared to llamas treated with 0mg EB. These results demonstrate that llama blastocysts produce estradiol and exogenous estradiol can enhance and transiently extend luteal progesterone production. Estradiol produced by the preimplantation llama blastocyst may play a role in maternal recognition of pregnancy and early luteal support.     

Polymorphism of the pig 17beta-hydroxysteroid dehydrogenase type1 (HSD17B1) gene and its association with reproductive traits

17beta-Hydroxysteroid dehydrogenase type 1 (HSD17B1) is a key enzyme of 17beta-estradiol biosynthesis, which might play an important role in follicular development of the ovary. In this study, we isolated the complete coding sequence of porcine HSD17B1 gene and its unique intron sequences of porcine HSD17B1 gene, identified a single nucleotide polymorphism (SNP: A/C) in intron 4, and developed a PCR-MvaI-RFLP genotyping assay. Association of the SNP and litter size was assessed in two populations (purebred Large White and a experimental synthetic Line (DIV) sows). Statistical analysis demonstrated that, in the first parity, AC animals in experimental synthetic Line (DIV) sows had 0.52 more piglets born compared to the CC animals (P<0.05). In the all parities, pigs with the AA genotype had an additional 1.11 and 0.96 piglets born alive compared to the CC animals (P<0.05) in both experimental synthetic Line (DIV) and purebred Large White, respectively. Experimental synthetic Line (DIV) sows inheriting the AC genotype had additional 0.84 piglets born alive compared to the CC animals (P<0.01) in all parities. In addition, significant additive effect of -0.55+/-0.24 piglets/litter and -0.48+/-0.22 piglets/litter on piglet born alive was detected in both experimental synthetic Line (DIV) sows and purebred Large White lines (P<0.05), respectively. Therefore, HSD17B1 gene was significantly associated with litter size in two populations and could be a useful molecular marker in selection for increasing litter size in pigs.     

Exogenous prostaglandin F(2)alpha at time of ovulation improves reproductive efficiency in repeat breeder sows

In order to determine if PGF(2)alpha could improve fertility in repeat breeder females when added to semen used for artificial insemination (AI) the following trial was performed. In a large indoor Hungarian production unit of 2000 sows, 667 repeat breeding females were assigned to two groups and were treated as follows: Group 1 (n=322), received PGF(2)alpha, added to the semen immediately before AI; Group 2 (n=345), received AI with untreated semen. Conception rate, farrowing rate, subsequent total and live born litter size and subsequent weaning to estrus intervals were evaluated. Conception and farrowing rates revealed highly significant differences between the PGF(2)alpha-treated and nontreated animals (P<0.001). Subsequent total born (P<0.07), and live born litter size (P<0.13), and subsequent weaning to estrus intervals (P<0.23) showed no significant differences. It is reasonable to suggest that exogenous PGF(2)alpha added to AI semen improves conception and farrowing rates.     

Endocrine, luteal and follicular responses after the use of the short-term protocol to synchronize ovulation in goats

The effect of the so-called Short-Term Protocol (5-day progesterone treatment+PGF(2)alpha) on ovarian activity and LH surge was studied in goats. The goats received 250IU eCG at the time of device withdrawal (eCG group; n=7), or 200microg of EB (estradiol benzoate) 24h after device withdrawal (EB group; n=8), or received neither eCG nor EB (control group; n=8). The Short-Term Protocol induced greater (4.1+/-1.1ng/ml) progesterone serum concentrations at 24h after start of the treatment, that declined to 0.2+/-0.1ng/ml at 12h after device withdrawal. In all of the groups, the maximum concentration of estradiol-17beta was reached at about 36h after device withdrawal. Maximum concentration was greater in the EB group (76.9+/-24.6pmol/l) than in the control group (41.8+/-9.0pmol/l; P<0.01), with the eCG group showing intermediate concentration (70.3+/-32.5pmol/l; P=NS). The LH peak occurred earlier in the eCG group (38.4+/-2.0h after device withdrawal) and in the EB group (41.0+/-4.1h), than in the control group (46.3+/-5.1h; P<0.05). Ovulation occurred earlier in the eCG group (5/7) and in the EB group (8/8) (58.8+/-2.7h and 63.0+/-5.6h, respectively), than in the control group (7/8) (70.2+/-8.3h; P<0.05). In summary, the Short-Term Protocol induced similar concentrations of progesterone among treated goats. In addition, eCG or EB resulted in a similar increase in estradiol-17beta and a similar LH surge, which induced ovulation in most females (86.7%) in a consistent interval (about 60h) after the end of progesterone exposure.     

Timing of insemination relative to ovulation in pigs: effects on sex ratio of offspring

The objective of the present study was to identify effects of the interval between insemination and ovulation in pigs on the sex ratio and sex ratio dispersion of offspring. Crossbred sows that had farrowed 2 to 9 litters were weaned (Day 0) and came into estrus between Days 3 and 7 after weaning. Ultrasonography was performed every 6 h, from 12 h after the onset of estrus until ovulation had been observed. The sows were inseminated once at various intervals from the onset of estrus. At farrowing, the numbers of viable piglets and dead piglets were recorded per sow. In four 12-h intervals between insemination and ovulation (36 to 24 h before ovulation, 24 to 12 h before ovulation, 12 to 0 h before ovulation and 0 to 12 h after ovulation), the total number of piglets was (mean+/-SEM) 10.8+/-1.2 (n=15); 13.4+/-0.7 (n=23); 13.2+/-0.9 (n=21); and 12.1+/-1.0 (n=16), respectively (P>0.05). The percentage of male piglets per litter in the four 12-h intervals was 52.1+/-3.6, 50.5+/-2.7, 54.9+/-2.8 and 47.8+/-4.5, respectively (P>0.05). Sex ratio was not influenced by litter size (P>0.05), and its distribution was normally dispersed (i.e., as expected under a binomial distribution) in all 4 intervals between insemination and ovulation (P>0.05).     

Exogenous steroid effects on litter size and early embryonic survival in swine

These studies confirm the efficacy of 12.5 mug estrone and 25 mg progesterone, administered on Days 16 and 17 of pregnancy, on increased litter size in swine. Substitution of estradiol (with ten-fold greater biological activity) for estrone in this regimen eliminated the positive effect on litter size and estradiol given alone at dosages of 3.1 and 6.3 mug were without effect. However, when estradiol was given in combination with progesterone (25 mg) at a dosage equivalent to 10% the effective estrone dosage (1.25 mug), a 22.6% increase in total pigs born per litter over controls was observed. Estrone alone at dosages of 6.25 and 12.5 mug did not alter litter size. At a dosage of 18.75 mug, an 8.7% decrease in total pigs born was noted. The amniotic fluid from sows treated for ten days with 12.5 mug estrone and 25 mg progesterone near the time of implantation, had significantly higher protein concentration, pH and osmolality.     

Induction of ovarian follicular wave emergence in wapiti (Cervus elaphus)

Two experiments were done to test the effects of treatments designed to electively induce ovarian follicular wave emergence in wapiti for the purpose of group synchronization. In Experiment 1, hinds were assigned randomly to three groups and given saline im (controls; n=5), 5mg of estadiol-17ss im (n=4), or 5mg estradiol-17ss plus 100mg progesterone im (n=5). In Experiment 2, hinds were assigned randomly to two groups and given no treatment (controls; n=6), or transvaginal ultrasound-guided follicle ablation (n=7). In both experiments, ovarian follicular dynamics were monitored by daily transrectal ultrasonography from Day 0 (day of treatment) to Day 9. In Experiment 1, blood samples were collected at each examination for measurement of serum concentrations of progesterone and FSH. Both experiments were conducted during the late anestrous period (July and August). The mean (+/-S.E.M.) day of wave emergence did not differ between the control and estradiol alone groups, but tended to be later in the estradiol plus progesterone group Day 4.0+/-0.7, Day 3.5+/-0.3, and Day 5.2+/-0.2, respectively; P=0.06). The interval from treatment to wave emergence was less variable in the estradiol plus progesterone group (P<0.05) and tended to be less variable in the estradiol-alone group (P=0.07) than in the control group. The day of wave emergence was more variable (P<0.05) and tended to be later (P=0.10) in the control group compared to the ablation group (Day 2.5+/-0.8 versus Day 1.4+/-0.2). All three treatments were effective in synchronizing ovarian follicular wave emergence among a group of wapiti hinds. Follicle ablation may be an alternative method for synchronization of follicular waves in estrus synchronization and superstimulatory protocols.     

The effect of exogenous estradiol benzoate and altrenogest on uterine and ovarian blood flow during the estrous cycle in mares

In recent years, a positive relationship between genital perfusion and fertility has been established; in species other than horses, uterine and ovarian perfusion was improved by exogenous estrogen but impaired by exogenous progestin. The goal of the present study was to investigate the effect of exogenous estrogen and progestin on uterine and ovarian blood flow in cycling mares. Five Trotter mares were examined daily during three estrous cycles. Mares were given no treatment, altrenogest (0.044 mg/kg BW) orally from Day 0 (ovulation) to Day 14 and estradiol benzoate (5mg i.m.) on Days 0, 5, and 10, in three cycles, respectively. There was no difference ( P > 0.05 ) in the length of untreated versus estrogen-treated cycles ( 22.8 +/-1.3 days and 23.2 +/= 1.5 days, respectively), but cycle length was increased (P < 0.05) in progestin-treated cycles (26.0 +/- 1.2). To facilitate comparisons among cycles with different lengths, data from Days 0 to 15 (diestrus) and from Days -6 to -1 (estrus) were analyzed. Transrectal Doppler sonography was used to evaluate blood flow in both uterine arteries and in the ovarian artery ipsilateral to the preovulatory follicle during estrus and ipsilateral to the corpus luteum during diestrus. Blood flow was assessed semiquantitatively using the pulsatility index (PI); high PI values indicated high resistance and a low perfusion and vice versa. An immediate effect of treatments occurred only after the administration of estradiol benzoate on Day 0; uterine PI values decreased (P < 0.05) between Days 0 and 1 and estrogen-treated mares but increased (P < 0.05) at the corresponding time in untreated cycles. Mean PI values for the uterine and ovarian arteries during both diestrus and estrus were higher (P < 0.05) in estrogen-treated versus untreated mares. Furthermore, mean uterine PI values during diestrus and estrus were higher (P< 0.05) in altrenogest-treated versus untreated mares. Neither estrogen nor altrenogest treatments had a significant immediate effect on ovarian PI values. Compared to untreated cycles, mean ovarian PI values were elevated (P < 0.05) only in the estrus following altrenogest administration. In conclusion, exogenous estrogen and progestin both decreased genital perfusion in cycling mares.     

Components of litter size in gilts with different prolactin receptor genotypes

Behavioral estrus and components of litter size at Day 35/36 of pregnancy were studied in gilts with prolactin receptor (PRLR) genotype AA (n=9), AB (n=25), and BB (n=22). This PRLR polymorphism (two alleles, A and B) has been associated with litter size, although it is not known whether the polymorphism itself causes differences in litter size or whether it is a marker for a closely linked causative gene. Estrus length in three successive estrous cycles was not affected by genotype, but estrous cycle length tended (P<0.1) to be longer for AA gilts compared to AB and BB gilts. AA gilts had a significantly (P<0.05) higher ovulation rate (21.5+/-0.9) than BB gilts (18.7+/-0.6), resulting in a numerically higher number of embryos at Day 35/36 (17.0+/-1.3, 15.6+/-0.8, and 13.7+/-0.9 for AA, AB, and BB gilts, respectively) which may lead to a subsequent difference in litter size. Ovulation rate of AB gilts (20.0+/-0.5) was intermediate. Genotype affected the total weight of the ovaries (P<0.05). Even after subtraction of the total weight of corpora lutea, ovarian weight in AA gilts was highest (16.6+/-1.0 g), in BB lowest (13.4+/-0.6g), and in AB gilts intermediate (15.0+/-0.6g; P<0.05). Unlike AB gilts, in AA and BB gilts uterine length was adapted to litter size, which led to longer (P<0.05) uteri for AA gilts (669+/-28 cm) compared to BB gilts (566+/-18 cm). Furthermore, embryos of AA gilts had heavier placentae (52.5+/-3.4 g) and larger implantation surface areas (309+/-19 cm(2)) than embryos of BB (42.0+/-2.3g, P<0.05; 256+/-12 cm(2), P<0.1) or AB (43.2+/-2.0 g, P<0.1; 257+/-11 cm(2), P<0.05) gilts. Results of this experiment show that the PRLR gene or a very closely linked gene affects porcine ovaries, uterus, and placenta in a way that might lead to differences in litter size. Since other genes and also environmental factors, however, might change the effect within the 112 days to parturition, it is preferable to state that the PRLR gene is a candidate gene for ovulation rate rather than for litter size.     

Reproductive performance of early-weaned female swine according to their estrus profile and frequency of artificial insemination

We determined the estrus profile (weaning-to-estrus interval (WEI), estrus duration (ED), and frequency of estrus per detection period) in 184 female swine and estimated the effect of the WEI, ED and frequency of artificial insemination (AI) on farrowing rate (FR) and litter size. Estrus detection was done at 8:30 a.m. and 5:00 p.m. The WEI was categorized as short (<100 h), medium (100-120 h) and long (>120 h). The ED was categorized as short (<60 h), medium (60-72 h) and long (>72 h). Mean lactation length was 14.6 days, mean WEI was 124.5 h and mean ED was 69 h. In each weaning group, females received either one or two AI, following a breeding schedule based on the estrus profile. In single-mated females, Al was performed 36 h after the beginning of estrus. In double-mated females, the first AI was done 24 h after the beginning of estrus and the second AI occurred 12 h later. The period of estrus detection had no effect (P > 0.05) on WEI, ED, FR, total born (TB) and live born litter size (LB). Mean FR was 82.6%, mean TB was 10.0% and mean LB was 9.2%. Mean ED was shorter (P < 0.03) for females having medium and long WEI (67.0 and 65.4 h, respectively) than for those having short WEI (72.2 h). A linear regression analysis identified a weak (R2 = 0.02) but significant negative association between ED and WEI (P = 0.05). The WEI did not influence FR (P > 0.05). Total litter size for females having short WEI (9.4) was lower (P < 0.03) than for those having long WEI (10.4). Also, LB for females having medium and long WEI (9.7-9.8) was higher (P < 0.05) than for those having short WEI (8.7). AI frequency had no effect on FR (P > 0.05). TB and LB litter size were lower (P < 0.05) for single-mated females (9.6 and 9.0, respectively) than for double-mated females (10.7 and 9.6, respectively). Double Al was associated with higher subsequent litter size. However, breeding schedules based only on estrus profile may not be precise in determining ideal breeding time, since females having short WEI had the longest ED and produced the lowest litter size.     

The role of LH pulse frequency in ACTH-induced ovarian follicular cysts in heifers

The aim of the present study was to induce ovarian cysts experimentally in cattle using ACTH and to closely examine the role of LH pulse frequency in ovarian cyst formation. Five regularly cycling Holstein-Friesian heifers (15-18-month-old) were used. Ovaries were scanned daily using an ultrasound scanner with a 7.5 MHz rectal transducer. Daily blood samples were obtained via tail venepuncture for hormone analyses. Additional blood samples (for FSH and LH pulses) were obtained through an indwelling jugular vein catheters every 15 min for 8 h on Days 2 (early luteal phase; ELP), 12 (mid-luteal phase; MLP) and 19 (follicular phase; FP) of control estrous cycle and on alternate days during follicular cyst (FC) formation and persistence. Cysts were induced using subcutaneous injections of ACTH (Cortrosyn) Z; 1 mg) every 12 h for 7 days beginning on Day 15 of the subsequent estrous cycle. Plasma concentrations of progesterone (P4), estradiol-17beta, FSH and LH were determined by double antibody radioimmunoassay while cortisol concentration was determined by enzyme immunoassay (EIA). Ovarian follicular and endocrine dynamics were normal during the control estrous cycles. Ovarian follicular cysts were induced in four of the five heifers. Mean maximum size of cysts was larger (P<0.05) than that of ovulatory follicles (26.78+/-3.65 versus 14.1+/-0.90 mm), respectively. Cortisol levels were increased during ACTH treatment. High concentrations of estradiol and low progesterone were observed after cyst formation. LH pulse frequency was significantly reduced (P<0.05) during cyst formation and persistence compared to ELP (7.5+/-0.75) and FP (6.5+/-0.58), but was not significantly (P=0.23) different from MLP (2.8+/-0.29) pulses. Mean LH pulse amplitude and concentrations were not different. Similarly, the mean pulse frequency, amplitude and concentration of FSH were not different between control study and cystic heifers. These results suggest that the LH pulse frequency observed following ACTH treatment may interact with high estradiol concentration to induce ovarian cyst formation in heifers.     

5个与猪产仔数相关基因的效应分析

为了比较不同基因对猪产仔数效应大小,在相同的大白 （158头）、长白 （224头）猪群中采用PCR-RFLP法进行了ESR、FSHβ、PRL、PRLR、NCOA1 5种与产仔数相关基因的基因型频率检测及不同基因型的总产仔数和产活仔数效应分析,结果表明,对相同母猪群产仔数影响效应最大的是PRLR和NCOA1基因,AA型比BB型母猪总产仔数高2.28~3.33头（P<0.01）,产活仔数高1.57~3.30头（P<0.01）,其次为ESR和FSHβ基因,BB型比AA型母猪总产仔数高0.55~1.18头（P<0.05,长白例外）,产活仔数高0.37~1.20头（P<0.05）。PRL基因对产仔数效应不显著。     

Effects of estrogen and prostaglandin on progesterone-delayed farrowing

Effects of estradiol benzoate and prostaglandin F(2alpha) (PGF(2alpha)) on concentrations of progesterone and estrogen in serum and the percentage of live births were determined in 21 gilts treated with exogenous progesterone in late gestation. All gilts received progesterone (25mg s.c. four times daily) from Days 108 through 113 of gestation. Gilts receiving no other treatments (controls) had elevated levels of progesterone through 1800 h on Day 114 (29.2 +/- 11.4 ng/ml) and farrowed at 115.6 +/- 0.3 d of gestation with a relatively low percentage of live births (66.8 +/- 17.3). Gilts treated with PGF(2alpha) administered at 0600 h on Day 114 had less (P<0.01) progesterone by 1800 h (7.0 +/- 1.3 ng/ml) relative to that of the controls, but they had similar gestation lengths (115.5 +/- 0.3) and percentages of live births (50.0 +/- 16.2). Administration of estradiol benzoate (10 mg) to gilts at 0600 h on Day 114 did not reduce progesterone on Day 114 or the gestation length relative to that of the control gilts, but it did increase (P<0.05) the percentage of live births (100%).     

Prostaglandin F2alpha supplemented semen improves reproductive performance in artificially inseminated sows

The objective of this study was to assess the effects of the addition of prostaglandin F2alpha (PGF2alpha) to semen, to increase reproductive performance in sows. Sows in 11 large production units, were inseminated (AI) either with PGF2alpha enriched fresh semen (group 1, n=1258) or with untreated fresh semen (group 2, n=1101). Conception rate, regular return to estrus, farrowing rate, subsequent total and live-born litter size, subsequent weaning to estrus intervals, pigs born and pigs weaned per sow per year were evaluated. Conception and farrowing rates, as well as regular returns to estrus were altered beneficially (P<0.001) with PGF2alpha supplemented semen. Subsequent total-born (P<0.06) and subsequent live-born (P<0.15) litter size, as well as subsequent weaning to estrus intervals (P<0.22), were not affected to the same extent. Total pigs born (P<0.05) and pigs weaned (P<0.04) per sow per year were increased by using PGF2alpha supplemented semen.     

Improved conception in timed-artificial insemination using a progesterone-releasing intravaginal device and Ovsynch protocol in postpartum suckled Japanese Black beef cows

The primary objective was to determine the effect of supplemental progesterone, administered via an intravaginal device (CIDR), on conception rates to timed-artificial insemination (timed-AI) in postpartum suckled Japanese Black beef cows treated with the Ovsynch protocol. A secondary objective was to compare the effects of treatments on plasma concentrations of progesterone and estradiol. Cows in the control group (Ovsynch, n=38) received a standard Ovsynch protocol (100 microg GnRH analogue on Day 0, 500 microg PGF2alpha analogue on Day 7, and 100 microg GnRH analogue on Day 9), with AI on Day 10, approximately 20 h after the second GnRH treatment. Cows in the treatment group (Ovsynch+CIDR; n=40) received a standard Ovsynch protocol plus a CIDR for 7 days (starting on Day 0). Plasma progesterone concentrations were determined on Days 0, 1, 7, 9, 10, and 17 and plasma estradiol-17beta concentrations were determined on Days 7, 9, 10, and 17. The odds ratio for likelihood of conception was 3.29 times greater (P=0.02) in the Ovsynch+CIDR group compared to Ovsynch group. The conception rate was greater (P=0.03) in the Ovsynch+CIDR group than in the Ovsynch group (72.5% versus 47.7%). Insertion of a CIDR device significantly increased plasma progesterone concentrations only on Days 1 and 7 (P<0.001 and P=0.05, respectively), but had no significant effect on plasma estradiol-17beta concentrations. Including a CIDR with the Ovsynch protocol significantly improved conception rates in postpartum suckled Japanese Black beef cows.     

The effect of hCG administration five days after insemination on the first service conception rate of anestrous dairy cows

The aim of this study was to investigate the effect of treating anovulatory anestrous (AA) dairy cows with 1500 IU of hCG IM, 5 d after insemination, on their first service conception rate. A clinical trial was conducted during the 2003/2004 breeding season involving 442 AA dairy cows in six herds. On Day -8, all cows were treated with a progesterone-containing intravaginal device (Cue-Mate). The devices were removed on Day -2, and on Day -1 all cows received an IM injection of 1mg of estradiol benzoate. Cows in the control group (n=220) received no further treatments. Cows in the treatment group (n=222) which had been inseminated on Days 0 or 1 were treated with 1500 IU of hCG IM 5 d after insemination. Blood was collected from 30 cows (15 in each group) on Days 5 and 12 after AI for analysis of plasma P4 concentration. There was no difference in first service conception rates between the control and treatment groups (46.3% versus 43.6%, respectively; P=0.68), despite the fact that plasma P4 concentrations were higher in the treatment group on Day 12 (4.9+/-1.3 ng/mL versus 6.2+/-2.7 ng/mL for control and treatment groups, respectively; P<0.01). In conclusion, 1500 IU of hCG 5 d after insemination did not improve first service conception rate in AA dairy cows.     

Increased ovulation rate in gilts after oral administration of epostane

In Phase I of this study to enhance ovulation rate and hence litter size, gilts received 0 (sham control), 0.625, 1.25, 2.5 or 5.0 mg epostane/kg body weight on Days 10, 11 and 12 of the oestrous cycle (5 gilts/group). After epostane treatment, plasma progesterone concentrations were reduced (P less than 0.01) in a dose-related manner, % progesterone decline = 21.30 x square root of (dose) + 10.45, R2 = 0.70, but recovered to pretreatment levels by 24 h. In Phase II the effects of epostane on ovulation rate and litter size were tested at two study centres. At each centre 108 gilts were treated with the same doses of epostane as used in Phase I and the doses were given for 7 days (Days 15-21) or 12 days (Days 10-21) during the first oestrous cycle. Gilts were inseminated twice during the oestrus after treatment and were slaughtered 30 days later. Mean (+/- s.d.) ovulation rate was 16 +/- 2.7 (N = 8) and 21 +/- 4.0 (N = 61) for control and epostane-treated gilts in Centre A and 12 +/- 2.4 (N = 5) and 17 +/- 3.8 (N = 55) respectively in Centre B (P less than 0.01 for both) and was dose related (ovulation rate = 3.38 x square root of (dose) + 16.17, R2 = 0.31). The effects of 7- or 12-day epostane treatment on ovulation rate were not different (P greater than 0.05), indicating that effects of treatment after Day 14 of the oestrous cycle are most important to subsequent ovulation frequency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ovarian antral follicle cauterization on the interestrus interval of the gilt

The objective of the present study was to determine if destruction of ovarian antral follicles by laser-cauterization affects CL lifespan during the estrous cycle of the gilt. Cyclic gilts were randomly assigned to either SHAM, laser (L) or laser-estradiol (L-E2) treatment groups, with the L-E2 group receiving a 5-mg intramuscular (i.m.) injection of estradiol-17beta cypionate at the time of the first surgery. Ovarian antral follicles were laser-cauterized on either Days 12 and 14 (L12) or Days 14 and 17 (L14) of the estrous cycle. In the L12-E2 group, 3 of 4 gilts had extended mean interestrus intervals of more than 22 days compared with 0 of 4, 0 of 6, 0 of 7 and 1 of 5 gilts in the SHAM, L12, L14 and L14-E2 groups, respectively. The L12-E2 gilts had a longer (P<0.05) mean interestrus interval (23.5+/-1.3 days) than the L12 (20.0+/-1.1 days), L14 (20.7+/-1.0 days) and SHAM (20.5+/-1.3 days). The mean interestrus interval of L14-E2 gilts (21.8+/-1.2 days) did not differ from those of the L12-E2 group or the L12, L14 and SHAM group gilts. Six additional gilts were injected with 5 mg estradiol cypionate-17beta to serve as nonsurgical controls for E2 treatment. Gilts (3 of 3) given an E2 injection on Day 12 had extended mean interestrus interval (26.0+/-2.6 days), while 2 of 3 gilts injected with E2 on day 14 had extended mean interestrus intervals (27.7+/-2.1 days). These results indicate that in cyclic gilts destruction of ovarian follicles by laser-cauterization did not affect CL lifespan, and that luteolysis is not dependent on the presence of antral follicles.     

Effect of feeding fungal endophyte (Acremonium coenophialum )-infected tall fescue seed on reproductive performance in CD-1 mice through continuous breeding

This study was designed to assess the effect of endophyte-infected (Acremonium coenophialum ) tall fescue (KY-31) seed (80% infected) on reproductive performance in CD-1 mice by continuous breeding. Twenty-four pairs of 70-d-old CD-1 mice were randomly allocated to four diets: 1) mouse chow ad libitum; 2) 40% infected fescue seed and 60% chow (w/w); 3) reduced intake (100% chow) similar to the intake, adjusted daily, in Diet 2; and 4) 60% infected fescue seed and 40% chow. Males and females were randomly paired (six pairs/treatment) and placed on the above diets. The mice were fed the corresponding diets for 80 d, although the pairs were separated on Day 60 (prior to the birth of the 3rd litter) and the females were monitored for one additional gestation period (20 d). The pregnancy data (litters produced) among the four treatments were 100.0 (18), 77.8 (14), 100.0 (18) and 80.0% (12) respectively. Similarly, the average number of pups born per litter among the four treatments was 11.8, 9.3, 10.1, and 9.8. When the chow treatment (1 and 3) and the fescue treatments (2 and 4) were pooled and compared, the percent pregnancy was 100.0 (n = 36) and 78.8 (n = 26), and the pups born per litter (means +/- SEM) were 11.0 +/- 0.5 and 9.5 +/- 0.6, respectively. Also the intervals between the three litters born during the 60-d cohabitation period were 21.6 +/- 1.1 and 24.5 +/- 0.9 d for the chow and fescue treatments, respectively. The results point out that 40 and 60% infected fescue seed in the diet of mice does influence (P < 0.05) their reproductive capacity as measured by percent pregnancy and litter size.     

An abnormal pattern of embryonic development during early pregnancy in aging rats

There is recent evidence that a decline in fertility and litter size precedes the cessation of regular estrous cyclicity in middle-aged female rats. This decline in litter size is related to a decrease in the number of normal blastocysts that are present on Day 5 of gestation, immediately prior to implantation. Thus, the pattern of embryonic development during the first 5 days of pregnancy may be altered in middle-aged rats, resulting in fewer implanting embryos and smaller litter sizes. The present study examined the ovulation rates, fertilization rates, and the patterns of embryonic development in regularly cyclic, young and middle-aged females during the first 5 days of pregnancy. Examination of the numbers of ovulated ova revealed that the ovulation rate was significantly reduced in 12- to 14-mo-old females (13 mo; 9.0 +/- 1.0/rat), but not in 9- to 11-mo-old females (10 mo; 12.2 +/- 0.8/rat), as compared to that in young animals (12.8 +/- 1.0/rat). However, there was no decrease in fertilization rate in either the 10-mo or 13-mo group. While the total numbers of embryos present on Days 2-5 were similar among all 3 groups, embryos from 10-mo females displayed a delayed pattern of development and an increased incidence of morphological abnormalities. These changes in embryo development were even more pronounced in the 13-mo group. By Day 5 of pregnancy there was a significant reduction in normal blastocysts in 10-mo (7.3 +/- 1.2/rat) and 13-mo (6.0 +/- 1.6/rat) rats, as compared to young females (10.6 +/- 0.9/rat).(ABSTRACT TRUNCATED AT 250 WORDS)