Reproduction In Pigs Research Articles

Distribution of runs of homozygosity in Chinese and Western pig breeds evaluated by reduced‐representation sequencing data

Inbreeding, which has several causes including genetic drift, population bottlenecks, mating of close relatives and selection, can leave tracts of runs of homozygosity (ROH) along genomes. Recently, decreasing performance on reproductive traits, which might have resulted from inbreeding, has been observed in Chinese pigs. In this study, 830 individuals from Western and Chinese pig breeds were genotyped using the reduced-representation sequencing method. After imputation and quality control, 60850 high-confidence SNPs were retained for ROH detection. A simulation was performed to explore the reliability of ROH detection with imputed data. Different ROH-related variables were compared between imputed and non-missing genotypes used in ROH detection. Furthermore, ROH islands were evaluated and annotated to find genes influenced by inbreeding in these pigs. The simulation results showed that imputed data with 0.7 as the average missing genotype rate and three heterozygotes allowed in a sliding window have comparable ROH detected compared with data with no missing genotypes. Compared with Western pig breeds, Chinese pigs had more autosomes covered by ROH longer than 5Mb, indicating higher inbreeding in Chinese pigs in recent times. Genes related to reproduction, immunity, meat quality and adaptability in Chinese pigs and several genes related to growth speed and immunity in Western pigs were observed in short ROH islands. The reproduction-related gene PRM1 was found to be located in the most frequent long ROH island in Chinese pigs, which might explain the decreasing fertility in Chinese pig breeds.

Mutations in cytochrome B gene effects female reproduction of Ghungroo pig

Cytochrome B is an important polypeptide of the mitochondria helpful in energy metabolism through oxidative phosphorylation. Cytochrome B plays an immense role in the reproduction of animals and due to its mutation prone nature, it can affect the basic physiology of animals. Cytochrome B affects reproductive system in males and equally plays an important role in transferring and providing energy in the development of the embryo, zygote, and oocytes precisely in females. The present study was conducted on Ghungroo pig to study their molecular and reproductive traits and the effect of the cytochrome B gene in the female reproduction of the Ghungroo pig. Although studies are available for cytochrome B gene analysis for evolutionary studies through phylogenetic analysis. This is the first report for the study of Cytochrome B gene on reproduction in pigs. Cytochrome B gene was sequenced and seven SNPs were observed out of which three were non-synonymous. INDEL mutation was detected in Variant B which had lead to Frame Shift mutation resulting in a stop codon AGA. The effect in the reproductive traits of the sow was studied due to the occurrence of nucleotide substitution. Bioinformatics analysis (I-mutant, PROVEAN, and SIFT) had revealed that the mutations were deleterious for the mutant type. Mutation leading to alterations in post-translational modification sites as phosphorylation site, leucine-rich nuclear export signal, occurrence of transmembrane helices, arginine and lysine peptide cleavage site for the mutant variant had resulted in a reduced physiological response. 3 D protein structure, (predicted through bioinformatics analysis) for cytochrome B has revealed distinct structural differences in mutated form with truncated protein by RMSD analysis through TM-Align software. Associated studies of genotype variants with reproductive traits have revealed the significant effect of variants of cytochrome B gene on reproductive traits namely litter size at first, second and third furrowing, piglet mortality, age at first furrowing and furrowing interval. Mitochondrial gene as Cytochrome B variants might be used as a marker for studying female reproduction of Ghungroo sow in future.

Genome-wide DNA methylation profiles of porcine ovaries in estrus and proestrus.

DNA methylation is an important epigenetic modification involved in the estrous cycle and the regulation of reproduction. Here, we investigated the genome-wide profiles of DNA methylation in porcine ovaries in proestrus and estrus using methylated DNA immunoprecipitation sequencing. The results showed that DNA methylation was enriched in intergenic and intron regions. The methylation levels of coding regions were higher than those of the 5'- and 3'-flanking regions of genes. There were 4,813 differentially methylated regions (DMRs) of CpG islands in the estrus vs. proestrus ovarian genomes. Additionally, 3,651 differentially methylated genes (DMGs) were identified in pigs in estrus and proestrus. The DMGs were significantly enriched in biological processes and pathways related to reproduction and hormone regulation. We identified 90 DMGs associated with regulating reproduction in pigs. Our findings can serve as resources for DNA methylome research focused on porcine ovaries and further our understanding of epigenetically regulated reproduction in mammals.

Whole-genome association and genome partitioning revealed variants and explained heritability for total number of teats in a Yorkshire pig population.

ObjectiveThe study was designed to perform a genome-wide association (GWA) and partitioning of genome using Illumina’s PorcineSNP60 Beadchip in order to identify variants and determine the explained heritability for the total number of teats in Yorkshire pig.MethodsAfter screening with the following criteria: minor allele frequency, MAF≤0.01; Hardy-Weinberg equilibrium, HWE≤0.000001, a pair-wise genomic relationship matrix was produced using 42,953 single nucleotide polymorphisms (SNPs). A genome-wide mixed linear model-based association analysis (MLMA) was conducted. And for estimating the explained heritability with genome- or chromosome-wide SNPs the genetic relatedness estimation through maximum likelihood approach was used in our study.ResultsThe MLMA analysis and false discovery rate p-values identified three significant SNPs on two different chromosomes (rs81476910 and rs81405825 on SSC8; rs81332615 on SSC13) for total number of teats. Besides, we estimated that 30% of variance could be explained by all of the common SNPs on the autosomal chromosomes for the trait. The maximum amount of heritability obtained by partitioning the genome were 0.22±0.05, 0.16±0.05, 0.10±0.03 and 0.08±0.03 on SSC7, SSC13, SSC1, and SSC8, respectively. Of them, SSC7 explained the amount of estimated heritability along with a SNP (rs80805264) identified by genome-wide association studies at the empirical p value significance level of 2.35E-05 in our study. Interestingly, rs80805264 was found in a nearby quantitative trait loci (QTL) on SSC7 for the teat number trait as identified in a recent study. Moreover, all other significant SNPs were found within and/or close to some QTLs related to ovary weight, total number of born alive and age at puberty in pigs.ConclusionThe SNPs we identified unquestionably represent some of the important QTL regions as well as genes of interest in the genome for various physiological functions responsible for reproduction in pigs.

Distribution of the pig gastrin-releasing peptide receptor and the effect of GRP on porcine Leydig cells

Gastrin-releasing peptide (GRP) is a mammalian bombesin (BN)-like peptide which plays a role in a number of important physiological functions via its receptor (gastrin-releasing peptide receptor, GRPR) in most animals. However, little is known about the gene encoding GRPR and its functions (especially reproduction) in pigs. In this study, we first cloned and analyzed the pig GRPR cDNA. Then we systematically investigated the expression levels of GRPR mRNA by relative real-time PCR (RT-PCR), and analyzed the distribution of the GRPR protein in pig tissues via immunohistochemistry (IHC). Finally, we studied the effect of GRP on testosterone secretion and GRPR (mRNA and protein) expression in Leydig cells. Results showed that the pig GRPR cDNA cloned at 1487bp, including one open reading frame (ORF) of 1155bp and encodes 384 amino acids. Significantly, compared with other species, the cDNA sequence and amino acid sequence of the pig GRPR were highly homologous and conservative. The RT-PCR results showed that: in the central nervous system (CNS) and the pituitary, GRPR mRNA was found in the cerebellum, hypophysis, spinal cord and hypothalamus; in the peripheral tissues, GRPR mRNA was mainly expressed in the pancreas, esophagus, ovary, testis, spleen, thymus, jejunum lymph node, muscle and fat. Moreover, the IHC results showed that GRPR immunoreactivity was widely distributed in the pig tissues and organs, such as the pancreas, esophagus, testis, ovary, spleen, pituitary gland and adrenal gland. In addition, we found that GRP promotes testosterone secretion, and increases GRPR mRNA and protein expression in cultured Leydig cells in vitro. These molecular and morphological data not only describe the anatomical locations of GRPR in pigs, but also provide the theoretical foundation for further research into its possible physiological functions in pigs. These results suggest that the GRP/GRPR system may play an important role in regulating the reproductive system of the boar.

Physiological mechanisms through which heat stress compromises reproduction in pigs.

Seasonal variations in environmental temperatures impose added stress on domestic species bred for economically important production traits. These heat-mediated stressors vary on a seasonal, daily, or spatial scale, and negatively impact behavior and reduce feed intake and growth rate, which inevitably lead to reduced herd productivity. The seasonal infertility observed in domestic swine is primarily characterized by depressed reproductive performance, which manifests as delayed puberty onset, reduced farrowing rates, and extended weaning-to-estrus intervals. Understanding the effects of heat stress at the organismal, cellular, and molecular level is a prerequisite to identifying mitigation strategies that should reduce the economic burden of compromised reproduction. In this review, we discuss the effect of heat stress on an animal's ability to maintain homeostasis in multiple systems via several hypothalamic-pituitary-end organ axes. Additionally, we discuss our understanding of epigenetic programming and how hyperthermia experienced in utero influences industry-relevant postnatal phenotypes. Further, we highlight the recent recognized mechanisms by which distant tissues and organs may molecularly communicate via extracellular vesicles, a potentially novel mechanism contributing to the heat-stress response.

Genetic control of complex traits, with a focus on reproduction in pigs.

Reproductive traits are complex, and desirable reproductive phenotypes, such as litter size or semen quality, are true polygenetic traits determined by multiple gene regulatory pathways. Each individual gene contributes to the overall variation in these traits, so genetic improvements can be achieved using conventional selection methodology. In the past, a pedigree-based-relationship matrix was used; this is now replaced by a combination of pedigree-based- and genomic-relationship matrices. The heritability of reproductive traits is low to moderate, so large-scale data recording is required to identify specific, selectable attributes. Male reproductive traits-including ejaculate volume and sperm progressive motility-are moderately heritable, and could be used in selection programs. A few high-merit artificial-insemination boars can impact many sow populations, so additional knowledge about male reproduction-specifically pre-pubertal detection of infertility and the technologies of semen cryopreservation and sex sorting-should further improve global breeding efforts. Conversely, female pig reproduction is currently a limiting factor of genetic improvement. Litter size and farrowing interval are the main obstacles to increasing selection intensity and to reducing generation interval in a breeding program. Age at puberty and weaning-to-estrus interval can be selected for, thereby reducing the number of non-productive days. The number of piglets born alive and litter weights are also reliably influenced by genetic selection. Characterization of genotype-environment interactions will provide opportunities to match genetics to specific farm systems. Continued investment to understand physiological models for improved phenotyping and the development of technologies to facilitate pig embryo production for genetic selection are warranted to ensure optimal breeding in future generations.

Genome-editing technologies to improve research, reproduction, and production in pigs.

The ability to directly manipulate the pig genome through genetic engineering has been available to the research community for over three decades. This technology has progressed from the random insertion of foreign DNA, via a variety of techniques (pronuclear microinjection, sperm mediated gene transfer, and integration of mobile genetic elements), to manipulation of endogenous genes, via homologous recombination in somatic cells followed by somatic cell nuclear transfer. Over the last few years, designer nucleases facilitated the development of techniques that provide efficient ways to introduce foreign DNA or to modify endogenous genes in eggs, zygotes, or somatic cells. Together, these genome-editing technologies have essentially removed the obstacles to gene manipulation in swine. Although the regulatory environment is still unclear for agricultural applications, genetic engineering of pigs will continue to advance biomedicine and biology. In addition, genetic engineering is now sufficiently simple and efficient that agricultural research can now ask basic and applied questions that are not hampered by limited funding.

Associations of genetic polymorphisms with reproduction and meat quality characteristics in Chinese Hebao pigs

The Hebao pig is a Chinese breed with high fecundity and vitality and excellent meat quality. This study aimed to explore polymorphisms of genes related to reproductive characteristics (ESR and FSHβ) and meat quality (MC4R, H-FABP, and A-FABP) by polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) in Hebao and commercial pigs (Landrace, Duroc, and Large White). Hebao and commercial pig crossbreeds were compared for fattening performance, reproduction traits, and carcass and meat quality. Piglet number per litter in pigs harboring the AA genotype for ESR was highest, with a significant difference between Landrace and Hebao pigs. For FSHβ, the AA genotype in Hebao and Duroc pigs produced the largest litter. The most abundant AA genotype in Hebao pigs produced lower backfat thickness compared with each commercial breed. Genotype distribution of H-FABP and A-FABP was significantly different between Hebao pigs and commercial pigs, reflecting Hebao pigs’ significant higher intramuscu...

Effect of Endogenous Faecal Glucocorticoid Metabolites on Reproduction in Wild Pigs - A Non Invasive Approach

Wild pigs are found to be the most prolific, very intelligent and secretive. These animals are adaptive ecological generalists and survive in wide range of habitats worldwide. The reproductive traits of wild pigs are extraordinary showing high prolificacy. Corticosteroids can exert inhibitory and facilitory effects on reproduction. In order to assess the attributable stress on reproduction a non-invasive method of assessing faecal glucocorticoid metabolites was applied in this study. Samples from wild pigs from three different regions were collected and were subjected to Enzyme Linked Imuno Sorbent Assay (ELISA). The purpose of this paper is to discuss the effect of stress on reproduction in wild pigs. Corticosteroids may act at the level of the ovary to suppress aromatase activity and thereby reduce the elevated circulating estrogens considered by many to be responsible for hyper secretion of Lutenizing Hormone (LH). Interestingly the acute level of stress is found to be facilitory and the chronic found to be inhibitory.

Uterine biology in pigs and sheep

There is a dialogue between the developing conceptus (embryo-fetus and associated placental membranes) and maternal uterus which must be established during the peri-implantation period for pregnancy recognition signaling, implantation, regulation of gene expression by uterine epithelial and stromal cells, placentation and exchange of nutrients and gases. The uterus provide a microenvironment in which molecules secreted by uterine epithelia or transported into the uterine lumen represent histotroph required for growth and development of the conceptus and receptivity of the uterus to implantation. Pregnancy recognition signaling mechanisms sustain the functional lifespan of the corpora lutea (CL) which produce progesterone, the hormone of pregnancy essential for uterine functions that support implantation and placentation required for a successful outcome of pregnancy. It is within the peri-implantation period that most embryonic deaths occur due to deficiencies attributed to uterine functions or failure of the conceptus to develop appropriately, signal pregnancy recognition and/or undergo implantation and placentation. With proper placentation, the fetal fluids and fetal membranes each have unique functions to ensure hematotrophic and histotrophic nutrition in support of growth and development of the fetus. The endocrine status of the pregnant female and her nutritional status are critical for successful establishment and maintenance of pregnancy. This review addresses the complexity of key mechanisms that are characteristic of successful reproduction in sheep and pigs and gaps in knowledge that must be the subject of research in order to enhance fertility and reproductive health of livestock species.

No effect of the plant growth regulator, chlormequat, on boar fertility

Chlormequat is a commonly used plant growth regulator in agriculture. Defined levels of chlormequat residue are allowed in food and an acceptable daily intake is defined for humans. However, there are results in the literature suggesting that a daily intake below the acceptable level for human is detrimental for mammalian reproduction. In the present experiment we investigated the effect of chlormequat at levels up to that acceptable for humans on reproduction in male pigs. Chlormequat (also known as chlorocholine chloride (CCC)) was mixed into the diet and given to the experimental animals at three levels (three treatment groups), i.e. 0 mg CCC/kg BW per day (Control), 0.025 mg CCC/kg BW per day and 0.05 mg CCC/kg BW per day. Eight mother sows per treatment group were used in the experiment. From the day of insemination, the mother sows received the experimental diets. The piglets were weaned at 4 weeks of age and two boar littermates continued on the same treatment as the dam until maturity and delivery of semen for in vitro fertilization (IVF) and in vivo fertilization. Semen volume, sperm concentration and fraction of live sperms were not (P ⩾ 0.46) detrimentally affected by chlormequat intake. The fraction of oocytes developing to more than the one-cell stage at day 5 after IVF was not (P = 0.88) detrimentally affected by chlormequat intake. Chlormequat intake did not detrimentally affect the fraction of gilts being pregnant after one insemination (P = 0.65) or the number of embryos in the pregnant gilts (P = 0.36). Serum chlormequat concentration was 0.9 μg/kg in the 0.025 mg CCC/kg BW per day group and 1.8 μg/kg in the 0.05 mg CCC/kg BW per day group, but was below the detection limit in control animals. In conclusion, the plant growth regulator chlormequat could not be proven to be detrimental to the selected reproduction traits in male pigs. This is in contrast to existing results from the male mouse.

Stress and its influence on reproduction in pigs: a review

The manifestations of stress, defined as a biological response to an event that the individual perceives as a threat to its homeostasis, are commonly linked to enhanced activity of the hypothalamo-pituitary-adrenal (HPA) axis and the activation of the sympathetic adreno-medullary (SA) system. Activation of the HPA system results in the secretion of peptides from the hypothalamus, principally corticotropin releasing hormone (CRH), which stimulates the release of adrenocorticotropic hormone (ACTH) and beta-endorphin. ACTH induces the secretion of corticosteroids from the adrenal cortex, which can be seen in pigs exposed to acute physical and/or psychological stressors. The present paper is a review of studies on the influence of stressors on reproduction in pigs. The effects of stress on reproduction depend on the critical timing of stress, the genetic predisposition to stress, and the type of stress. The effect of stress on reproduction is also influenced by the duration of the responses induced by various stressors. Prolonged or chronic stress usually results in inhibition of reproduction, while the effects of transient or acute stress in certain cases is stimulatory (e.g. anoestrus), but in most cases is of impairment for reproduction. Most sensitive of the reproductive process are ovulation, expression of sexual behaviour and implantation of the embryo, since they are directly controlled by the neuroendocrine system.

In vivo and in vitro effects of the mycotoxins zearalenone and deoxynivalenol on different non-reproductive and reproductive organs in female pigs: A review

This review summarizes the toxicological data on the effects of the mycotoxins zearalenone (ZON), its metabolites, and deoxynivalenol (DON) on different parameters relating to reproductive and non-reproductive organs in female pigs. In vivo, 22 mg ZON kg−1 in the diet cause alterations in the reproductive tract of swine such as in the uterus, and affects follicular and embryo development. ZON and its metabolites have been shown to bind competitively to oestrogen receptors in an in vitro system. The feeding of pigs with a 9 mg DON kg−1-contaminated diet can act on protein synthesis, humoral and cellular immune response depending on dose, exposure and timing of functional immune assay, and affect liver and spleen cell structures. Beside these effects, reproductive alterations were observed in pigs, too. Both in vivo and in vitro exposure to DON decreased oocyte and embryo development. In vitro application of DON to uterine cells inhibits their proliferation rate and modulates the process of translation at a different molecular level when compared with the in vivo application. The histopathological results provide evidence of spleen and liver dysfunction in the absence of clinical signs, especially in pigs fed higher concentrations of Fusarium toxin-contaminated wheat. Prepuberal gilts react more sensitively to DON > ZON feeding compared with pregnant sows. In the liver, histopathological changes such as glycogen decrease and interlobular collagen uptake were only observed in prepuberal gilts, whereas enhancement of haemosiderin was found in both perpuberal gilts and pregnant sows. This review presents some of the current knowledge on the biological activities of ZON and DON in pig. Altogether, ZON affects reproduction of pigs most seriously because it possesses oestrogenic activity. However, DON affects reproduction in pigs via indirect effects such as reduced feed intake, resulting in reduced growth or impairment of function in vital organs such as liver and spleen.

Susceptibility of reproduction in female pigs to impairment by stress or elevation of cortisol

It is generally agreed that stress can impair reproduction. Furthermore, it is often thought that cortisol, which is secreted during stress as a result of activation of the hypothalamo-pituitary adrenal axis, is associated with this stress-induced impairment of reproduction. It has been hypothesized that reproduction in females is particularly susceptible to disruption by acute stress during the series of endocrine events that induce estrus and ovulation. Nevertheless, we found no support for this conjecture when we subjected female pigs to repeated acute stress or repeated acute elevation of cortisol during the period leading up to estrus and ovulation. Conversely, studies have demonstrated that prolonged stress and sustained elevation of cortisol can disrupt reproductive processes in female pigs. Nevertheless, in each study that demonstrated this effect, there were some animals subjected to the prolonged stressor or the sustained elevation of cortisol in which the reproductive parameters that were measured were not affected by the treatment. We propose that reproduction in female pigs is resistant to the effects of acute or repeated acute stress or acute or repeated acute elevation of cortisol even if these occur during the series of endocrine events that induce estrus and ovulation. Furthermore, while reproductive processes in some individuals are compromised, reproduction in a proportion of female pigs appears to be resistant to the effects of prolonged stress or sustained elevation of cortisol.

Factors regulating ovarian function in pigs

The hormonal interactions of the hypothalamic–pituitary–ovarian–uterine axis are accountable for a normal reproduction in female pigs. It is of importance to have knowledge of estrous symptoms and hormonal profiles around ovulation. The introduction of the transrectal ultrasonography in sows has given us the possibility to study ovarian activity in conscious animals and relate the timing of estrus to ovulation. Combining this technique with measuring of several hormones like luteinizing hormone (LH), follicle-stimulating hormone (FSH), inhibin, estradiol, progesterone, insulin-like growth hormone I (IGF-I), prostaglandin F 2α (PGF 2α) metabolite, oxytocin, facilitate our knowledge about the sequence of ovarian events. Evidence suggests that activation of the hypothalamic–pituitary–adrenal axis may hamper the normal gonadotropin secretion and in consequence, the ovarian function. The metabolic status during lactation, weaning of piglets and social stress might affect onset of ovarian activity and the related estrous behavior. The role of seminal plasma, artificial insemination and presence of the boar might also be included as factors regulating the temporal kinetics of ovulation, corpus luteum development, uterine function and steroid production in the ovary. Studies using a simulated stress by means of adrenocorticotrophic hormone (ACTH) administration or food deprivation are tools in understanding how the ovary is susceptible to impairment. The intention of this paper is to review current knowledge concerning the endocrine aspects of normal and stress-influenced ovarian function in pigs.

Expression of nitric oxide synthase isoforms in the porcine ovary during follicular development

The expression of nitric oxide synthase (NOS) isoforms in the ovaries of pigs was examined to study the involvement of nitric oxide, a product of NOS activity, in the function of the ovary. Western blot analysis detected three types of NOS in the ovary, including constitutive neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS); eNOS immunoreactivity was more intense compared with that of iNOS or nNOS. Immunohistochemical studies demonstrated the presence of nNOS and eNOS in the surface epithelium, stroma, oocytes, thecal cells, and endothelial cells of blood vessels. Positive immunoreactions for nNOS and iNOS were detected in the granulosa cells from multilaminar and antral follicles, but not in those of unilaminar follicles. iNOS was detected in the surface epithelium, oocytes, and theca of multilaminar and antral follicles. Taking all of the findings into consideration, the observed differential expression of the three NOS isoforms in the ovary suggests a role for nitric oxide in modulating reproduction in pigs.

A genome scan for quantitative trait loci and imprinted regions affecting reproduction in pigs

Quantitative trait loci for reproductive traits in a three-generation resource population of a cross between low-indexing pigs from a control line and high-indexing pigs from a line selected 10 generations for increased index of ovulation rate and embryonic survival are reported. Phenotypic data were collected in F2 females for birth weight (BWT, n = 428), weaning weight (WWT, n = 405), age at puberty (AP, n = 295), ovulation rate (OR, n = 423), number of fully formed pigs (FF, n = 370), number of pigs born alive (NBA, n = 370), number of mummified pigs (MUM, n = 370), and number of stillborn pigs (NSB, n = 370). Grandparent, F1, and F2 animals were genotyped for 151 microsatellite markers. Sixteen putative QTL (P < 0.10) for reproductive traits were identified in previous analyses of these data with single QTL line-cross models. Data were reanalyzed with multiple QTL models, including imprinting effects. Data also were analyzed with half-sib models. Permutation was used to establish genome-wide significance levels ( = 0.01, 0.05, and 0.10). Thirty-one putative QTL for reproductive traits and two QTL for birth weight were identified (P < 0.10). One Mendelian QTL for FF (P < 0.05), one for NBA (P < 0.05), three for NSB (P < 0.05), three for NN (P < 0.05), seven for AP (P < 0.10), five for MUM (P < 0.10), and one for BWT (P < 0.10) were found. Partial imprinting of QTL affecting OR (P < 0.01), BWT (P < 0.05), and MUM (P < 0.05) was detected. There were four paternally expressed QTL for NN (P < 0.10) and one each for AP (P < 0.05) and MUM (P < 0.10). Maternally expressed QTL affecting NSB (P < 0.10), NN (P < 0.10), and MUM (P < 0.10) were detected. No QTL were detected with half-sib analyses. Multiple QTL models with imprinting effects are more appropriate for analyzing F2 data than single Mendelian QTL line-cross models.

Census of genes expressed in porcine embryos and reproductive tissues by mining an expressed sequence tag database based on human genes.

A total of 98,898 expressed sequence tags (ESTs) derived from embryos and reproductive tissues in pigs were identified in the GenBank "est_others" database. Pig embryos were collected at 11, 12, 13, 14, 15, 20, 30, and 45 days after gestation. The reproductive tissues were sampled from testis, ovary, endometrium, hypothalamus, anterior pituitary, uterus, and placenta. A gene-oriented approach was developed to annotate these porcine EST sequences to census the genes expressed from these sources. Of the 33 308 mRNA sequences from the human genes used as references (data accessed on 1 November 2002), 9410 had the porcine EST homologs expressed in embryos and 11 795 had the EST homologs expressed in reproductive tissues. The entire genome contributes at least 28.3% of its genes to embryo development and 35.4% of its genes to reproduction. Using the EST entry numbers as indicators of gene expression, we determined that the gene expression patterns differ significantly between embryos and reproductive tissues in pigs. The basic active genes were identified for each source, but most of them are not coexpressed abundantly. Few genes were expressed on the Y chromosome (P < 0.01), but they may represent counterparts of the double-dose genes that remain active in an inactivated X chromosome in females but are needed for proper development and growth. The census provides a panel of transcripts in a broad sense that can be used as targets to study the mechanisms involved in embryo development and reproduction in pigs and other mammals, including humans.

Relation between early fear- and anxiety-related behaviour and maternal ability in sows

Fear induced by exposure to humans, and anxiety induced by novel environmental changes may both function as stressors and have negative effects on reproduction in pigs. An earlier experiment indicated that reactions to humans and novelty had some repeatability between the ages of 8 and 24 weeks, thus reflecting personality traits. The present experiment therefore tested for predicted negative relationships between behaviour related to fear and anxiety measured at 8 weeks of age and later reproduction in 30 sows. Factor analysis of behaviour in a voluntary human approach test performed in the home cage and a novel object test performed in a novel arena indicated that behavioural measures related to investigation of these stimuli loaded on separate factors and may therefore reflect independent underlying dimensions. One factor related to investigation of the human was interpreted as reflecting the level of fear of humans, while another was correlated to investigation of the novel object and interpreted as indicating novelty-induced anxiety. Factor scores were generated for ‘fear’ and ‘anxiety’ and used in regression analysis as predictors of maternal behaviour and reproductive parameters. Higher levels of fear of humans were associated with longer durations of farrowing, larger variation in inter-birth intervals, and a higher number of piglets dying without milk in their stomachs. The duration of farrowing was positively correlated to the number of live born piglets dying within 3 weeks of age. Higher fear also tended to associate with a higher number of stillborn and a higher number of live born piglets dying within 3 weeks of age. High anxiety only tended to be associated with a higher number of stillborn. These results are interpreted as supporting the hypothesis that there are negative associations between fear of humans and maternal ability in sows.