Effect of dominant follicle removal before superstimulation on follicular growth, ovulation and embryo production in Holstein cows

This study was to investigate whether removing the dominant follicle 48 h before superstimulation influences follicular growth, ovulation and embryo production in Holstein cows. After synchronization, ovaries were scanned to assess the presence of a dominant follicle by ultrasonography with a real-time linear scanning ultrasound system on Days 4, 6 and 8 of the estrus cycle (Day 0 = day of estrus). Twenty-six Holstein cows with a dominant follicle were divided into 2 groups in which the dominant follicle was either removed (DFR group, n=13) by ultrasound-guided follicular aspiration or left intact (control group, n=13) on Day 8 of the estrus cycle. Superovulation treatment was initiated on Day 10. All donors were superovulated with injections of porcine FSH (Folltropin) twice daily with constant doses (total: 400 mg) over 4 d. On the 6th and 7th injections of Folltropin, 30 mg and 15 mg of PGF2alpha (Lutalyse) were given. Donors were inseminated twice at 12 h and 24 h after the onset of estrus. Embryos were recovered on Day 6 or 7 after AI. During superstimulation, the number of follicles 2 to 5 mm (small), 6 to 9 mm (medium) and > or = 10 mm (large) was determined by ultrasonography on a daily basis. At embryo recovery, the number of corpora lutea (CL) was also determined by ultrasonography and blood samples were collected for analysis of progesterone concentration. Follicular growth during superstimulation was earlier in the DFR group than in the control group. The number of medium and large follicles was greater (P < 0.01) in the DFR group than in the control group on Days 1 to 2 and Days 3 to 4 of superstimulation, respectively. The numbers of CL (9.6+/-1.1 vs 6.1+/-0.9) and progesterone concentration (30.9+/-5.4 vs 18.6+/-3.5 ng/mL) were greater (P < 0.05) in the DFR group than in the control group, respectively. The numbers of total ova (7.7+/-1.3 vs 3.9+/-1.0) and transferable embryos (4.6+/-0.9 vs 2.3+/-0.8) were also greater (P < 0.05) in the DFR group than in the control group, respectively. It is concluded that the removal of the dominant follicle 48 h before superstimulation promoted follicular growth, and increased ovulation and embryo production in Holstein cows.     

Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 +/- 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 +/- 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 +/- 1 or 71 d +/- 1 d of gestation for evaluation of reproductive performance. Age (190 +/- 3 d vs 195 +/- 3 d) and body weights (106 +/- 2 kg vs 106 +/- 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 +/- 0.7 vs 12.9 +/- 0.9, P = 0.31) and 71 d (13.9 +/- 0.6 vs 12.4 +/- 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 +/- 0.7 vs 9.7 +/- 0.7) but not at 71 d (10.0 +/- 1.1 vs 9.6 +/- 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.     

Effect of buffalo follicular fluid treatment on follicle population and ovulation rate in guinea pigs

A number of workers have studied the effect of follicular fluid (FF) on the secretion of follicular stimulating hormone (FSH) but little is known about its potential as a regulator of ovarian activity, including ovulation rate. This paper describes the effect of charcoal treated-buffalo follicular fluid (buFF) treatment on follicular growth and ovulation rate in guinea pigs. Eighteen guinea pigs in three groups of 6 each were given 0.2 ml buFF at 12 hr interval for 3 days at different stages of estrous cycle viz., early-luteal, mid-luteal or follicular phase. One control group received equal volume of saline. Estrus was monitored every morning and evening by inspection of the opening of vaginal membrane and its cytology. All animals were sacrificed at 24 hr after the onset of estrus. Both the ovaries were dissected out, weighed and number of ovulation points recorded. One ovary from each animal was processed for histological examination to determine the population of healthy and atretic follicles. In early-luteal and follicular phase-treated animals the onset of estrus was delayed (P < 0.01) and ovulation rate was not affected. However, estrus occurred at normal when the treatment was initiated at midluteal stage and 50% animals failed to ovulate in this group. The total follicle population at metestrus increased significantly in all treated animals because of increase in number of follicles of size class II (400 to < 600 microns diam.). Atresia was also declined due to treatment. These results demonstrated that the buFF contained some inhibitory substances that delayed the onset of estrus in guinea pigs.     

Effects of recombinant human follicle stimulating hormone on follicle development and ovulation in the mare

The only gonadotrophin preparation shown to stimulate commercially useful multiple ovulation in mares is equine pituitary extract (EPE); even then, the low and inconsistent ovulatory response has been ascribed to the variable, but high, LH content. This study investigated the effects of an LH-free FSH preparation, recombinant human follicle stimulating hormone (rhFSH), on follicle development, ovulation and embryo production in mares. Five mares were treated twice-daily with 450 i.u. rhFSH starting on day 6 after ovulation, coincident with PGF(2alpha) analogue administration; five control mares were treated similarly but with saline instead of rhFSH. The response was monitored by daily scanning of the mares' ovaries and assay of systemic oestradiol-17beta and progesterone concentrations. When the dominant follicle(s) exceeded 35 mm, ovulation was induced with human chorionic gonadotrophin; embryos were recovered on day 7 after ovulation. After an untreated oestrous cycle to 'wash-out' the rhFSH, the groups were crossed-over and treated twice-daily with 900 i.u. rhFSH, or saline. At the onset of treatment, the largest follicle was <25 mm in all mares, and mares destined for rhFSH treatment had at least as many 10-25 mm follicles as controls. However, neither dose of rhFSH altered the number of days before the dominant follicle(s) reached 35 mm, the number of follicles of any size class (10-25, 25-35, >3 mm) at ovulation induction, the pre- or post-ovulatory oestradiol-17beta or progesterone concentrations, the number of ovulations or the embryo yield. It is concluded that rhFSH, at the doses used, is insufficient to stimulate multiple follicle development in mares.     

The influence of insulin administration after weaning the first litter on ovulation rate and embryo survival in sows

Primiparous crossbred sows (n = 43), lactating for an average of 21.1 +/- 0.1 d and weaning 8.7 +/- 0.1 pigs, were used to evaluate the influence of insulin on ovulation rate and embryo survival. The sows were maintained on 2.3 kg/head/d of a 14% protein gestation diet during pregnancy, fed ad libitum during lactation, given 2.7 kg/head/d from weaning until re-breeding and fed 2.3 kg/head/d after mating. Beginning the day after weaning (Day 0) sows were treated with 0.4 IU/kg body weight (BW) insulin (n = 21) or were administered an equivalent volume of saline (n = 22) for 4 d. Beginning on Day 3 and continuing until Day 14 after weaning, the sows were checked for estrus twice daily and were artificially inseminated using pooled semen from 2 fertile boars. At slaughter (days 30 to 40 of gestation), ovaries and uteri were collected, and the ovulation rate, embryo number and viability, and uterine weight and length were evaluated and recorded. Use of insulin decreased the average interval from weaning to estrus compared with saline by increasing percentage in estrus by Day 14 after weaning (5.0 +/- 0.57 vs 6.9 +/- 0.56 d, respectively; P < 0.03). Ovulation rate, number of embryos, embryo survival, and average uterine length and weight were not influenced by insulin treatment. Overall, insulin affected reproductive efficiency in primiparous sows by increasing the percentage of sows in estrus.     

Concentrations of gonadotropins,estradiol and progesterone in sows selected on an index of ovulation rate and embryo survival

The objective of this study was to determine concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P₄) and 17β-estradiol (E₂) in sows from a line selected on an index which emphasized ovulation rate (Select) and from a control line. A further classification of the sows in each line was made according to the estimated number of ovulations during an estrous cycle. Sows in the Select line were ranked into a high (HI) or low group (LI) when their estimated number of ovulations were 25 or more and 14 to 15, respectively. Sows of the control line were classified into groups as high (HC) or low (LC) when the estimated values for ovulation rate were 14–15 and 8–9 ovulations, respectively. Blood samples were collected every 12 h during a complete estrous cycle and samples were analyzed for concentrations of FSH and LH. Samples collected every 24 h were assayed for P₄ and E₂. Mean concentrations of FSH, LH, P₄ and E₂ did not differ (P>0.10) between lines or between HI and LI or HC and LC groups. Selection of pigs for ovulation rate and embryonal survival did not affect concentrations of FSH, LH, P₄ and E₂ in sows during the estrous cycle.     

Recovery rates and embryo quality following dominant follicle ablation in superovulated cattle

To determine the association between dominant follicle ablation and the outcome of a superovulatory regimen, two data sets were constructed from records of 171 recoveries from non-ablated cows and 1214 recoveries from cows that underwent follicular ablation prior to FSH treatment. Data set 1 included all cows with 2 or more records (n = 1385). Data set 2 included paired data for 87 cows which had at least 2 records of both ablated and non-ablated superovulatory attempts. Dominant follicle ablation was performed by use of transvaginal, ultrasound guided aspiration 48 hr prior to the start of FSH. The same FSH protocols were used for both ablated and non-ablated cows. For all cows (data set 1), more total ova/embryos were recovered from the ablation group (12.1+/-0.3 vs 10.5+/-0.8; P=0.06). This difference could be accounted for by greater numbers of non-transferable embryos in the ablation group (6.5+/-0.2 vs 5.3+/-0.6; P>0.01). For the paired data (data set 2), greater numbers of total ova/embryos recovered from the ablation group (12.8+/-1.0 vs 9.7+/-0.7; P=0.01) could also be accounted for by higher numbers of nontransferable embryos in this group (7.8+/-0.8 vs 4.5+/-0.4; P>0.01). There were no differences between groups for high quality embryos, percent cows producing no ova/embryos or percent cows producing no transferable embryos. These data support the premise that synchronization of follicular waves following dominant follicle ablation increases total ova/embryo output. However, the additional embryos were primarily nontransferable thereby negating potential economic gains.     

Effect of a unilateral or bilateral twin embryo distribution on twinning and embryo survival rate in the cow

Uni- and bilateral twin embryo distributions were effected by the transfer of one embryo on Day 7 to the ipsi- or contralateral uterine horn of previously inseminated heifers (123, Exp. 1) or cows (95, Exp. 2). The embryo transfers were surgical in Exp. 1 and non-surgical in Exp. 2. Transferred and native embryos were distinguished by breed. Embryo survival rate was measured in a proportion (N = 40) of the heifers at Day 53 of gestation and in the remainder of the heifers and all of the cows at term. In the heifers (Exp. 1) overall pregnancy rates of 76% and 75% were recorded after uni- and bilateral twin embryo distributions respectively. Twinning rates of 55% and 60% at Day 53 of gestation and 60% and 60% at term were recorded for uni- and bilateral distributions respectively. In the cows (Exp. 2) calving rates of 61% and 63% and twinning rates of 33% and 38% were recorded following uni- and bilateral twin embryo distributions respectively. When the data from both experiments were combined, overall embryo survival rates were similar for both twin embryo distributions although the ipsilateral transfer of an embryo reduced the survival rate of the native embryo. It is concluded that the confinement of two embryos in one uterine horn on or after Day 7 does not depress pregnancy, twinning or overall survival rate to term.     

Effect of follicle diameter on oocyte apoptosis, embryo development and chromosomal ploidy in prepubertal goats

The aim of this study was to assess the following parameters in prepubertal goat oocytes of different follicle diameter (≥3 mm, <3 mm, control): oocyte diameter, early (Annexin-V) and late (TUNEL) apoptosis, embryo development and chromosomal ploidy of these blastocysts using Fluorescence In Situ Hybridization (FISH). Before in vitro maturation, oocytes were measured and stained with Annexin-V or TUNEL. The rest of the oocytes were matured, fertilized, and cultured in vitro for 8 days. Oocytes from follicles of ≥3 mm showed greater mean oocyte diameter (128.27 ± 7.20 μm vs. 125.35 ± 7.59 μm), higher percentages of TUNEL positive (42.86 vs. 24.23%), higher cleavage (47.85 ± 3.98 vs. 23.07 ± 2.44 %) and blastocyst rates (19.77 ± 3.04 vs. 4.11 ± 1.10 %) than oocytes from follicles of <3 mm.. Blastocyst mean cell numbers did not show differences between follicular groups (123.83 ± 49.62 vs. 104.29 ± 36.09 for follicles of ≥3 mm and <3 mm, respectively). A total of 54 blastocysts with 7084 nuclei were hybridized with specific probes to chromosomes X and Y. Ninety-eight percent (98%) of the embryos presented at least one cell carrying an abnormal number of chromosomes, but 78% of them presented less than 25% of chromosomal abnormal cells. No differences in the percentage of blastocysts with abnormal ploidy were found in embryos produced from oocytes of different follicle diameter.     

Administration of human chorionic gonadotropin at embryo transfer induced ovulation of a first wave dominant follicle, and increased progesterone and transfer pregnancy rates

We hypothesized that administration of hCG to recipients at embryo transfer (ET) would induce accessory CL, increase serum progesterone concentrations, and reduce early embryonic loss (as measured by increased transfer pregnancy rates). At three locations, purebred and crossbred Angus, Simmental, and Hereford recipients (n = 719) were assigned alternately to receive i.m. 1,000 IU hCG or 1 mL saline (control) at ET. Fresh or frozen-thawed embryos were transferred to recipients with a palpable CL on Days 5.5 to 8.5 (median = Day 7) of the cycle (Locations 1 and 2), or on Day 7 after timed ovulation (Location 3). Pregnancy diagnoses (transrectal ultrasonography) were done 28 to 39 d (median = 35 d) and reconfirmed 58 to 77 d (median = 67 d) post-estrus. At Location 1 (n = 108), ovaries were examined at pregnancy diagnosis to enumerate CL. More (P < 0.001) pregnant hCG-treated cows (69.0%) had multiple CL than pregnant controls (0%). Serum progesterone (ng/mL) determined at Locations 1 and 2 (n = 471) at both pregnancy diagnoses in pregnant cows was greater (P ≤ 0.05) after hCG treatment than in controls (first: 8.1 ± 0.9 vs 6.1 ± 0.8; second: 8.8 ± 0.9 vs 6.6 ± 0.7), respectively. Unadjusted pregnancy rates at the first diagnosis were 61.8 and 53.9% for hCG and controls. At the second diagnosis, pregnancy rates were 58.6 and 51.3%, respectively. Treatment (P = 0.026), embryo type (P = 0.016), and BCS (P = 0.074) affected transfer pregnancy rates. Based on odds ratios, greater pregnancy rates occurred in recipients receiving hCG, a fresh embryo (66.3 vs 55.5%), and having BCS >5 (62.3 vs 55.3%). We concluded that giving hCG at ET increased incidence of accessory CL, serum progesterone in pregnant recipients, and transfer pregnancy rates. Furthermore, we inferred that increased progesterone resulting from hCG-induced ovulation reduced early embryonic losses after transfer of embryos to recipients.     

The relation between patterns of ovarian follicle growth and ovulation rate in sheep

The number and growth rate of follicles within classes based on granulosa volume were determined for ovaries taken from groups of 4-5-year-old, fine-wool Merino ewes drawn at different times of the year from a single strain flock maintained at Armidale, N.S.W. The breeding season of the flock normally extends from February to October and the mean ovulation rate rises from about 0.5 in February to about 1.8-1.9 during April-May. Ewes sampled when they were anoestrous or had one (single-ovulatory) or two (twin-ovulatory) recent corpora lutea did not differ in respect to the mean total number of ovarian follicles, the mean number of follicles in individual classes, the time for follicles to complete their rapid growth stage, or the incidence of follicle atresia. However, the ovaries of twin-ovulatory ewes contained significantly more follicles in the two terminal classes within the rapid growth stage than did the ovaries of single-ovulatory or anoestrous ewes (2.2 v. 0.9 and 1.0). This difference was attributed to the differing numbers of follicles per day entering into the rapid growth stage (5.2, 4.5 and 3.7 respectively in twin-ovulatory, single-ovulatory and anoestrous ewes).     

Superovulatory responses in dairy cows following ovulation of the dominant follicle of the first wave

In the present study we investigated the effect of hCG administration on Day 7 (Day 0 = day of standing estrus) to ovulate the dominant follicle of the first wave and the associated increase in progesterone concentration on subsequent superovulatory response in dairy cows. Twenty cyclic lactating cows were allocated at random to 2 groups: control (n = 10) and hCG-treated (n = 10). The ovaries of each cow were scanned using an ultrasound scanner on Day 7, to confirm the presence of the dominant follicle and thereafter every other day until embryo recovery. All cows received a total dose of 400 mg Folltropin-V in decreasing amounts for 5 days (Days 9 to 13) and 35 mg PGF(2alpha) on Day 12. In addition, the treated cows received 1000 IU hCG on Day 7. All cows were inseminated twice during estrus, and the embryos were collected 7 days later by a nonsurgical procedure. Blood smaples were taken at different times of the treatment period for progesterone determination. All cows possessed a dominant follicle at Day 7, and all but one of the hCG-treated cows ovulated the dominant follicle and formed an accessory corpus luteum. Plasma progesterone concentrations were significantly higher (P<0.01) in hCG-treated cows than control cows on the first day of Folltropin treatment and on the day of PGF(2alpha) injection. The mean number of follicles at estrus, the number of ovulations, the total number of embryos and the number of transferable embryos were not different (P>0.05) between control and hCG-treated cows.     

Effect of short-term preservation of sea lamprey gametes on fertilisation rate and embryo survival

We assessed the effect of short-term (4.7–75.3 h) storage at low temperature (approximately 1 °C) on the viability of sea lamprey ( Petromyzon marinus L.) gametes. Hatching success decreased with storage time, but more than 20% eggs hatched even after 75.3 h of preservation. However, storage time drastically reduced the survival rate to the burrowing stage (i.e. the last prelarval stage), which decreased from 76% when the gametes were stored for 4.7 h to 0% after 75.3 h of storage.     

FSH influences follicle viability, oestradiol biosynthesis and ovulation rate in Romney ewes

Injection of steroid-free bovine follicular fluid (bFF; 2 X 5 ml s.c. 12 h apart) into anoestrous ewes lowered plasma FSH concentrations by 70% and after 24 h had significantly (P less than 0.01) reduced the number of non-atretic follicles (greater than or equal to 1 mm diam.) without influencing the total number of follicles (greater than 1 mm diam.) compared to untreated controls. Hourly injections of FSH (10 micrograms i.v. NIH-FSH-S12) for 24 h did not influence the number of non-atretic follicles but did negate the inhibitory effects of bFF on follicular viability. Hourly injections of FSH (50 micrograms i.v., NIH-FSH-S12) + bFF treatment for 24 h significantly increased the total number of non-atretic follicles, and particularly the number of medium to large non-atretic follicles (greater than 3 mm diam.) compared to the untreated controls (both P less than 0.01). The 10 micrograms FSH regimen (without bFF) significantly increased aromatase activity in granulosa cells from large (greater than or equal to 5 mm diam.; P less than 0.01) but not medium (3-4.5 mm diam.) or small (1-2.5 mm diam.) follicles compared to controls. The 10 micrograms FSH + bFF regimen had no effect on granulosa-cell aromatase activity compared to the controls. However, the 50 micrograms FSH plus bFF regimen increased the aromatase activity of granulosa cells from large, medium and small non-atretic follicles 2.6-, 8.3- and greater than or equal to 11-fold respectively compared to that in the control cells. Ewes (N = 11) that ovulated 2 follicles had significantly higher plasma FSH concentrations from 48 to 24 h and 24 to 0 h before the onset of a cloprostenol-induced follicular phase (both P less than 0.01) than in the ewes (N = 12) that subsequently ovulated one follicle. Hourly FSH treatment (1.6 micrograms i.v., NIAMDD-FSH-S15) for 24 h but not for any 6 h intervals between 48 and 24 h or 24 and 0 h before a cloprostenol-induced luteolysis also resulted in significant increases (P less than 0.05) in the number of ewes with 2 ovulations.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of asynchronous superinduction on embryo survival and range of blastocyst development in swine

The importance of uniform development of blastocysts was examined by comparing the effects of asynchronous superinduction (Day 6 embryos into Day 7 pregnant recipients and Day 7 embryos into Day 6 pregnant recipients) on the range of embryo development at Days 12 and 13 to subsequent survival to Day 30. Twenty gilts were used to produce five Day 7 recipients that received Day 6 embryos and five Day 6 recipients that received Day 7 embryos. Embryos from the Day 7 and Day 6 recipients were examined 6 days later. Recovered embryos ranged morphologically from spherical to filamentous blastocysts. This range of embryos was within the limits of that previously observed for naturally mated sows. However, recovered blastocysts from the Day 6 embryos transferred into Day 7 recipients were morphologically more variable and proportionately less developed than the blastocysts from the Day 7 embryos transferred into Day 6 recipients. Forty additional gilts were subsequently utilized to generate 20 recipients (10 recipients per transfer group) that were examined on Day 30. More Day 7 embryos transferred into Day 6 recipients survived (p less than 0.05) than Day 6 embryos transferred into Day 7 recipients. These experiments suggested that greater variation in early development of embryos, within litters, subsequently resulted in greater mortality of embryos.     

Effect of variation in embryo stage on the establishment of pregnancy, and embryo survival and growth in ewes with two embryos

Embryos at different stages of development were transferred to recipient ewes on Day 6 to investigate the effect of variation in stage of development on embryo survival and growth. Three groups of ewes received 2 embryos that were at the same stage of development, Day 4, Day 6 or Day 8. A fourth group received 1 Day-4 and 1 Day-8 embryo. At autopsy on recipient Day 34 there were no significant differences in embryo survival (Day 4, 34%; Day 6, 50%; Day 8, 46%; and Day 4 and 8, 48%). Fetuses developing from Day-8 embryos were heavier than others (Day 4, 1.10 +/- 0.06 g; Day 6, 1.15 +/- 0.06 g; Day 8, 1.41 +/- 0.08 g; P less than 0.05). In Group 4 neither survival nor growth of embryos was significantly affected by the presence of an embryo at a different stage of development. The ability of the uterus to stimulate development of a relatively retarded embryo is confirmed. Apparently the uterus has less effect in slowing the development of advanced embryos.     

Markers of follicle function in Belclare-cross ewes differing widely in ovulation rate.

High prolificacy due to a gene that has a large effect on ovulation rate has been noted in Booroola and Inverdale ewes. High prolificacy in the Belclare breed (a composite developed from stocks selected for very large litter size or high ovulation rate) may be related to the segregation of two genes. The aims of this study were (i) to compare the morphological and functional features of ovulatory follicles from carriers (which could only be heterozygous for the genes of interest) and non-carriers, and (ii) to identify markers of the Belclare genes among secreted or cellular ovarian proteins. Belclare carrier ewes had more ovulatory follicles (4.9 +/- 0.4) than did non-carrier ewes (2.0 +/- 0.2) (P < 0.001). Ovulatory follicles from carriers were also smaller (4.4 +/- 0.1 mm versus 5.7 +/- 0.2 mm, P < 0.001) and contained a significantly reduced number of granulosa cells (P < 0.001). However, the proportion of proliferating granulosa cells in ovulatory follicles was similar in both groups. The in vitro secretion of steroids per follicle was only marginally lower in follicles from Belclare carriers compared with non-carriers. Furthermore, similar concentrations of steroidogenic enzymes were present in both groups, indicating that steroidogenic potential per granulosa cell is similar between carriers and non-carriers. Possible markers of the Belclare genes were identified among cellular proteins of follicular walls by two-dimensional PAGE and image analysis. Two spots at 78 and 49 kDa were always absent in samples from non-carriers. When secreted proteins in follicles from carriers were compared with those from non-carriers, two spots at 53 and 41 kDa were restricted to samples from carriers and three spots at 97, 91 and 45 kDa were unique to samples from non-carriers. Interestingly, the spot at 91 kDa is also affected by the Booroola gene.     

Plasma progesterone profiles,ovulation rate,donor embryo yield and recipient embryo survival in native Saloia sheep in the fall and spring breeding seasons

The response to superovulatory (SOV) and estrus synchronization (ES) treatments and the fertility of donor (n=68) and recipient (n=118) Saloia ewes was evaluated in the fall and spring breeding seasons. The proportion of acyclic ewes at treatment time was significantly higher in the spring than in the fall (42.6% versus 4.0%, P<0.00001). Donors treated with eCG had a significantly higher mean number of follicles over 5mm in diameter in the ovaries at embryo recovery and a significantly lower mean efficiency of recovery than FSH-treated ewes. These negative effects were more pronounced in the fall than in the spring, which resulted in a significantly lower mean number of total and fertilized ova recovered from eCG-treated ewes, compared to FSH donors in the fall, but not in the spring. Season had no significant effect on the ovulation rate and plasma P4 concentrations of recipients treated with a progestagen plus eCG combination. Although the recipient lambing and embryo survival rates were higher in the fall than in the spring the differences were not significant. No significant differences were observed in the ovulation rate or P4 concentrations of recipients that lambed compared to those that did not lamb. These preliminary results show that, in Portugal, response of Saloia ewes to SOV or ES treatments and donor fertility following the SOV treatment were similar in the spring and the fall, which suggests that in the spring acyclic ewes are in moderate anestrus. The effect of season on fertility following embryo transfer should be confirmed in further studies involving a larger number of animals. The semilaparoscopic transfer method reported here allowed lambing and embryo survival rates higher (although not significantly) than a standard surgical approach.     

The relationship between ovulation rate and embryonic survival in gilts

Norwegian Landrace gilts were inseminated on the second day of their second oestrus and slaughtered 28 to 34 days after insemination. The number of corpora lutea (ovulation rate) and normal embryos was counted and the embryonic survival rate was calculated for the 306 pregnant gilts. Mean (+/-S.D.) ovulation rate, number of normal embryos and embryonic survival rate were 14.17+/-2.48, 10.55+/-3.30 and 74.8%+/-20.7%, respectively. The significant (P<0.001) curvilinear regression of embryonic survival rate on ovulation rate gives a maximum embryonic survival rate at 13.2 ovulations. Increased ovulation rate gives increased number of normal embryos up to 18.1 ovulations. Ovulation rate should be considered when assessing factors affecting embryonic survival in pigs.