Macroenvironment effects on oocytes and embryos in swine

Effect of split weaning on follicle development and oocyte quality in multiparous sows

Increasing piglet weaning age while maintaining the reproductive efficiency of the breeding herd depends on being able to stimulate sows to ovulate during lactation without reducing subsequent pregnancy rates and litter sizes. Embryo survival is affected by the quality of the oocytes shed at ovulation, and oocyte quality is profoundly impacted by the follicular environment in which the oocyte matures. This study determined the effect of reducing suckled litter size from 11 to 7 piglets on day 18 of lactation on the ovarian follicular environment and oocyte developmental competence at day 21 of lactation. Thirty-nine, Large White X Landrace sows (parity 3.2 ± 0.2; mean ± SEM; range 2-6) had their litter size either maintained at 11 piglets (control); or reduced to seven piglets on day 18 of lactation (split wean (SW)). Sows were slaughtered on day 21 of lactation and ovaries were collected for analysis of follicular fluid composition and in vitro blastocyst development rates. There was no effect of split weaning on fertilisation rate and development to blastocyst stage; however, a greater proportion of blastocysts from control sows were classified as early blastocyst stage. Furthermore, follicular fluid concentrations of oestradiol were higher in SW sows. Together, these results indicate split weaning prior to mating in lactation alters the ovarian follicular environment and while blastocyst development rates were unaffected, embryos from control sows may be of poorer quality as indicated by a delay in development.

Effects of dietary coenzyme Q10 supplementation during gestation on the embryonic survival and reproductive performance of high-parity sows

BACKGROUND

Fertility declines in high-parity sows. This study investigated whether parity-dependent declines in embryonic survival and reproductive performance could be restored by dietary coenzyme Q10 (CoQ10) supplementation.

METHODS

Two experiments were performed. In Exp. 1, 30 young sows that had completed their 2^nd parity and 30 high-parity sows that had completed their 10^th parity, were fed either a control diet (CON) or a CON diet supplemented with 1 g/kg CoQ10 (+ CoQ10) from mating until slaughter at day 28 of gestation. In Exp. 2, a total of 314 post-weaning sows with two to nine parities were fed the CON or + CoQ10 diets from mating throughout gestation.

RESULTS

In Exp. 1, both young and high-parity sows had a similar number of corpora lutea, but high-parity sows had lower plasma CoQ10 concentrations, down-regulated genes involved with de novo CoQ10 synthesis in the endometrium tissues, and greater levels of oxidative stress markers in plasma and endometrium tissues. High-parity sows had fewer total embryos and alive embryos, lower embryonic survival, and greater embryo mortality than young sows. Dietary CoQ10 supplementation increased the number of live embryos and the embryonic survival rate to levels similar to those of young sows, as well as lowering the levels of oxidative stress markers. In Exp. 2, sows showed a parity-dependent decline in plasma CoQ10 levels, and sows with more than four parities showed a progressive decline in the number of total births, live births, and piglets born effective. Dietary supplementation with CoQ10 increased the number of total births, live births, and born effective, and decreased the intra-litter covariation coefficients and the percentage of sows requiring farrowing assistance during parturition.

CONCLUSIONS

Dietary CoQ10 supplementation can improve the embryonic survival and reproductive performance of gestating sows with high parity, probably by improving the development of uterine function.

Changes in piglet and litter characteristics across parities in two highly prolific sow hybrids in an outdoor organic herd

High piglet mortality constitutes a welfare challenge in organic pig production. Litter characteristics were investigated from parities 1-5 of two hyper-prolific hybrids with different selection traits in an organic commercial herd (DanBred vs. Topigs Norsvin [TN70]). TN70 sows had more functional teats than DanBred sows, and their offspring had higher birth weights. Several interactions between hybrid and parity were found. The total born increased with higher parity and was more pronounced for DanBred sows. Litter weight at weaning was higher in parities 1-4 for TN70 compared with DanBred, and within DanBred parities 4 and 5 had higher litter weight at weaning than parity 1. The survival rate was higher for TN70 in parities 1 and 2 compared with DanBred, and for both hybrids, the survival rate was higher in parities 1 and 2 compared with parities 4 and 5. The number of weaned piglets was stable across parities 1-4 but lower in parity 5 for both hybrids. Thus, despite a lower number of total born piglets in TN70, TN70 sows weaned the same number of piglets as DanBred, with a lower mortality rate and a heavier litter at weaning.

Estrus Synchronization of Replacement Gilts Using Estradiol Cipionate and PGF2α and Its Effects on Reproductive Outcomes

In this study, we evaluated the effectiveness of using estrogen-induced prolonged luteal function followed by prostaglandin F2 alpha (PGF2α) treatment to synchronize estrus in gilts. On day12 of the estrus cycle (D0 = first day of standing estrus), 52 gilts were assigned at random to two experimental groups: non-treated gilts (CON, n = 22), serving as controls, and prolonged luteal function group (CYP, n = 30), receiving a single treatment with 10 mg of estradiol cypionate intramuscularly Starting on day 12, blood samples were collected for estradiol and progesterone assays. Estrus detection started on day 17. Gilts from the CON group were inseminated at the onset of natural estrus. On day 28 CYP gilts were treated with PGF2α to induce luteolysis and inseminated at the onset of estrus. Gilts were slaughtered 5 d after the last insemination. A single treatment with estradiol cypionate prolonged luteal function in 90% of treated gilts. The duration of the estrous cycle was longer (p < 0.0001) for CYP gilts compared to CON gilts. CYP gilts showed synchronized estrus 3.96 ± 0.19 d after induction of luteolysis. The conception rate was similar (p = 0.10) for CON and CYP gilts. No difference was observed in the embryo recovery rate (p = 0.18) and total number of embryos per female (p = 0.06). The percentage of unfertilized oocytes, fragmented embryos and viable embryos was similar among females from CON and CYP groups (p > 0.05). The treatment of gilts with a single application of 10 mg of estradiol cypionate on day 12 of the estrous cycle was effective in prolonging luteal function and treatment with PGF2α resulted in synchronized estrus. Additionally, the synchronization protocol had no deleterious effect on fertility and embryonic development.

Pregnancy in pigs: the journey of an early life

Embryo mortality is responsible for greater losses in litter size in pigs. It is well known that pregnancy establishment is a complex process, and important changes occur continuously in both the corpora lutea and the endometrium, which varies depending on the pre-natal development phase: embryonic, pre-implantation or fetal stages. The placenta is a key organ responsible for the exchange of nutrients, metabolites and respiratory gases between mother and fetuses. The porcine placenta is diffuse, epitheliochorial, and placentation begins with implantation, which involves specialized cell adhesion and cell migration, leading to the attachment of the trophectoderm to the uterine endometrial lumen epithelium. The efficiency with which the placenta provides adequate amounts of nutrients and oxygen to the fetus is crucial for proper fetal growth and development. In the last decades, emphasis on selection for sow prolificacy has resulted in a substantial increase in the number of piglets born per litter, which had a direct effect on piglet quality, compromising birth weight and litter uniformity. Placental insufficiency will lead to fetal intrauterine growth restriction. This review addresses the main events of early embryo development, including preimplantation and implantation periods. In addition, placentation and its role on fetal development are covered, as well as intrauterine growth restriction, as it is a natural condition in the pig, with long lasting detrimental effects to the production chain.

Expression of the Bone Morphogenetic Protein-2 (BMP2) in the Human Cumulus Cells as a Biomarker of Oocytes and Embryo Quality

BACKGROUND

The members of the transforming growth factor-B superfamily, as the bone morphogenetic proteins (BMPs) subfamily and anti-Müllerian hormone (AMH), play a role during follicular development, and the bone morphogenetic protein-2 (BMP2), AMH, and THY1 are expressed in ovaries.

AIM

This study was designed to define whether or not the expressions of these proteins in human cumulus cells (CCs) can be used as predictors of the oocyte and embryo competence.

SETTINGS AND DESIGN

The study included nine female patients who were diagnosed as idiopathic infertility, aged 25-33 years (median 30 years) and underwent Assisted Reproductive Technologies.

MATERIALS AND METHODS

The CCs from 60 oocyte-cumulus complexes obtained from the nine patients were evaluated with immunofluorescence staining in respect of BMPs, AMH and THY1 markers. The CCs surrounding the same oocytes were evaluated separately according to the oocyte and embryo quality.

STATISTICAL ANALYSIS

Quantitative data were statistically analyzed for differences using the two-sided Mann-Whitney U test (P < 0.05).

RESULTS AND CONCLUSIONS

Significant differences in immunofluorescence staining were observed in oocyte quality and embryo quality for the BMP2 only (P < 0.05). No significant differences were observed for AMH or CD90/THY1.

CONCLUSION

These results demonstrated that there is a significant difference in the expression of BMP2 in the CCs of good quality oocytes and subsequently a good embryo.

Reproduction of group-housed sows

The sow is a social animal in her behavior throughout the reproductive cycle. An exception to her preference for being a part of a social group occurs one to two1–2 d days prior to farrowing, when she separates from her group and seeks for isolation in order to build up a nest. She then spends the first week or two with her piglets, mainly in the nest. After this short period of separation of 1–2 weeks, she brings her litter with her and rejoins the group. In modern intensive pig production, the sow is often restricted to an individual cage for lactation and, in many European countries, she may still spend additional periods in stalls during pregnancy. In the intensive production, isolation of the sow from the rest of the group is therefore a relatively long period of six to ten6-10 weeks, which creates a challenge for the social memory of the sow. While grouping of sows during lactation is an interesting option, until now this is encountered mostly in organic or otherwise extensive farming systems, such as outdoor farming. However, the present society is asking for more animal friendly models of production and there appears to be more need for studies of group housing issues during lactation. Grouping of sows after weaning causes stress, which imposes risks for fertility. Thus, timing of grouping is probably very critical. It is well documented that the embryonic period of the pregnancy, lasting up to Day 35, is more vulnerable for loss of pregnancy than the subsequent fetal period. There are indications that stress of grouping may cause some harm to vitality parameters of blastocysts already while at the site of fertilization in the oviduct. Later on, during the critical periods of maternal recognition of pregnancy, endocrinological models testing maintenance of pregnancy suggest that chronic stress lasting for more than two2 days may cause abortion and loss of the whole litter. However, the sow may be resistant, in terms of her reproductive function, to acute stress lasting for hours or up to a day. In conclusion, grouping of sows during lactation may be of interest in the future. At present, issues of group housed sows after weaning and early pregnancy seem to be of most practical relevance. Chronic stress of sows lasting for more than two2 days may lead to loss of the whole litter.

Within-litter variation in birth weight: impact of nutritional status in the sow

Accompanying the beneficial improvement in litter size from genetic selection for high-prolificacy sows, within-litter variation in birth weight has increased with detrimental effects on post-natal growth and survival due to an increase in the proportion of piglets with low birth-weight. Causes of within-litter variation in birth weight include breed characteristics that affect uterine space, ovulation rate, degree of maturation of oocytes, duration of time required for ovulation, interval between ovulation and fertilization, uterine capacity for implantation and placentation, size and efficiency of placental transport of nutrients, communication between conceptus/fetus and maternal systems, as well as nutritional status and environmental influences during gestation. Because these factors contribute to within-litter variation in birth weight, nutritional status of the sow to improve fetal-placental development must focus on the following three important stages in the reproductive cycle: pre-mating or weaning to estrus, early gestation and late gestation. The goal is to increase the homogeneity of development of oocytes and conceptuses, decrease variations in conceptus development during implantation and placentation, and improve birth weights of newborn piglets. Though some progress has been made in nutritional regulation of within-litter variation in the birth weight of piglets, additional studies, with a focus on and insights into molecular mechanisms of reproductive physiology from the aspects of maternal growth and offspring development, as well as their regulation by nutrients provided to the sow, are urgently needed.

Differences in X-chromosome transcriptional activity and cholesterol metabolism between placentae from swine breeds from Asian and Western origins

To gain insight into differences in placental physiology between two swine breeds noted for their dissimilar reproductive performance, that is, the Chinese Meishan and white composite (WC), we examined gene expression profiles of placental tissues collected at 25, 45, 65, 85, and 105 days of gestation by microarrays. Using a linear mixed model, a total of 1,595 differentially expressed genes were identified between the two pig breeds using a false-discovery rate q-value ≤0.05. Among these genes, we identified breed-specific isoforms of XIST, a long non-coding RNA responsible X-chromosome dosage compensation in females. Additionally, we explored the interaction of placental gene expression and chromosomal location by DIGMAP and identified three Sus scrofa X chromosomal bands (Xq13, Xq21, Xp11) that represent transcriptionally active clusters that differ between Meishan and WC during placental development. Also, pathway analysis identified fundamental breed differences in placental cholesterol trafficking and its synthesis. Direct measurement of cholesterol confirmed that the cholesterol content was significantly higher in the Meishan versus WC placentae. Taken together, this work identifies key metabolic pathways that differ in the placentae of two swine breeds noted for differences in reproductive prolificacy.

Methyl donor supplementation of gestating sow diets improves pregnancy outcomes and litter size

Maternal intake of B-vitamin and methyl donors can affect sow prolificacy. A total of 1079 Large White/Landrace sows (parities 2–9 at mating) were used in a 2 by 2 by 2 factorial design to determine the effects of two levels of betaine supplementation (0 versus 3 g added betaine/kg feed), two levels of folic acid plus vitamin B12 supplementation (0 versus 20 mg/kg folic acid plus 150 µg/kg vitamin B12) during gestation, and two parity groups (parity 2 and 3 versus parity 4 and greater) on litter size and pregnancy outcomes. The number of sows returning to oestrus post-insemination, as well as the number of early (<Day 30) and late (>Day 30) pregnancy losses were recorded. At farrowing, the total number of piglets born, the number of piglets born alive and dead, as well as the number of mummified fetuses were recorded. Pre-prandial blood samples were collected from a subset of 20 sows/treatment on Days 3, 30 and 107 of gestation to analyse homocysteine. The incidence of early pregnancy loss was reduced (P < 0.001) by folic acid plus vitamin B12 supplementation (0.03 versus 0.07). There was a significant interaction between parity at mating (parities 2 and 3 versus parity 4 and greater) and the addition of betaine or folic acid plus vitamin B12 to the gestation diet on litter size. Litter size was higher (0.5 piglets; P < 0.05) for betaine supplemented, compared with unsupplemented, parity 4 plus sows. Folic acid plus vitamin B12-supplemented parity 2 and 3 sows gave birth to more (P < 0.05) piglets than all other treatment groups. Folic acid plus vitamin B12 supplementation decreased (P < 0.001) plasma homocysteine concentration by 2.2 and 2.8 μM, respectively, on Days 3 and 107 of gestation. However, betaine supplementation decreased (P < 0.05) homocysteine on Day 3 only. Overall, folic acid plus vitamin B12 supplementation decreased incidences of early pregnancy failure and increased litter size in early parity sows, while betaine increased litter size in older parity sows.

Fertility of sows fed ad libitum with a high fibre diet during pregnancy

The effect of ad libitum (ADLIB) feeding strategy on the fertility of the group housed sow was studied in a prospective field trial during 1.5 years. All study animals farrowed under standard farrowing circumstances in crates, and they were provided with an ad libitum feeding throughout the 30-day lactation. After weaning, animals were randomly allocated to one of the two dry sow feeding strategies (AD LIB or CONT). After oestrus detection in groups, they were artificially inseminated and moved into pregnancy pens with partially slatted floor, in groups of 40 sows each. The ADLIB sows (n = 447) were loose housed and provided with ad libitum access to 7.7 MJ/kg feed high in fibre from two feeders per group. The control sows (n = 479; CONT) were also loose housed and given a standard dry sow feed in feeding stalls once a day (2.5 kg/day. The energy content of the feed was 9.3 MJ/kg NE). The feeding strategy (ADLIB vs CONT) had no effect on pregnancy rate (85.8 vs 90.9, p > 0.05), weaning to oestrus interval (7.7 vs 7.3 days, p > 0.05), piglets born alive (11.5 ± 3.5 vs 11.6 ± 3.3, p > 0.05), stillborn piglets (1.2 ± 1.8 vs 0.9 ± 1.5, p > 0.05) nor on progesterone concentration (p > 0.05). CONT sows weaned more piglets (9.7 ± 2.2 vs 9.4 ± 2.0, p < 0.01), whereas the piglets of AD LIB sows were heavier at weaning (8.8 ± 0.9 vs 8.0 ± 1.3 kg, p < 0.05). In conclusion, ad libitum feeding with a high in fibre diet during pregnancy did not affect the reproductive performance.

Restricted feed intake in lactating primiparous sows. I. Effects on sow metabolic state and subsequent reproductive performance

The effects of feed restriction (60% of anticipated feed intake; Restrict; n = 60) during the last week of a 21-day lactation in primiparous sows compared with feeding at 90% of anticipated feed intake (Control; n = 60) on sow metabolic state, litter growth and sow reproductive performance after weaning were compared. Metabolisable energy (ME) derived from feed was lower, ME derived from body tissues was higher and litter growth rate was reduced (all P < 0.05) in Restrict sows during the last week of lactation. Treatment did not affect weaning-to-oestrus interval, pregnancy rate, ovulation rate, embryonic survival or the number of live embryos (P > 0.05) at Day 30 of gestation: However, embryo weight was greater (P < 0.05) in Control than in Restrict sows (1.55 ± 0.04 vs 1.44 ± 0.04 g, respectively). These data suggest the biology of the commercial sow has changed and reproductive performance of contemporary primiparous sows is increasingly resistant to the negative effects of lactational catabolism. Overall, catabolism negatively affected litter weaning weight and embryonic development of the next litter, but the extent to which individual sows used tissue mobilisation to support these litter outcomes was highly variable.

Pig preovulatory oocytes modulate cumulus cell protein and gene expression in vitro

This study investigated the changes in protein and gene expression in oocytectomized cumulus cells (OOX) of medium-sized follicles from gilts, cultured with or without denuded oocytes isolated from large oestrogenic sow follicles. Proteomic analysis identified 14 proteins that were differentially expressed in OOX, of which the protein 14-3-3 eta, a signal transduction pathway modulator, was down-regulated in the presence of oocytes. Oocyte co-culture also down-regulated FSHR mRNA expression in OOX, as measured by real-time PCR, and FSHR and 14-3-3 eta mRNA abundance were positively correlated. The oocyte also up-regulated HSD3B mRNA, suggesting an effect on cumulus cell progesterone synthesis. Together with data on gene expression in granulosa cells during the follicular phase of the sow oestrous cycle, this study suggests that modulation of the expression of steroidogenesis related proteins and genes in cumulus cells by the porcine preovulatory oocyte reflects the specific physiological requirements of the preovulatory follicle.