Start Date: Jul 31, 2007
End Date: Jul 30, 2012
Changes in testicular composition and volume will be monitored during pubertal development to establish their relationship with testicular size and sperm production at maturity. Histological approaches and ultrasonography in combination will be used to develop a non-invasive protocol. Genomic scans on these same boars will identify QTL associated with sperm production. In a sub-population of these boars, individual differences in viability of sperm cells will be assessed during cold storage and following cryopreservation. A series of experimental approaches will investigate uterine capacity. RNA from placental tissues collected between days 25 to 45 of gestation from lines of pigs selected for ovulation rate or uterine capacity will be hybridized to porcine arrays to yield expression differences in the placental transcriptome related to line and stage of gestation. Identification of polymorphisms in differentially expressed genes will establish haplotype associations for uterine capacity and fetal survival. A catalog of imprinted genes will be established for porcine placenta and evaluated for coding region polymorphisms identified in Meishan x White Composite embryos. The contribution of placental fold development to placental efficiency will include gene sequence variation in hyaluronidase and heparanase and the association of this variation with differences in litter size and piglet birth weights. Laser capture micro-dissection combined with suppressive-subtraction hybridization will define expression differences between placental trophoblast cell types during late gestation. Impact of farrowing intervals on stillbirths will be monitored with 24-hr video recording of parturition and correlated with piglet survival and growth during lactation. A second experiment will investigate the effect of dietary creatine on farrowing intervals, stillbirth, and preweaning survival. Further investigation will include treatment of late pregnant sows with monoclonal antibodies against the alpha subunit of the porcine insulin receptor to interfere with insulin binding to its receptor with the goal of increasing fetal, blood glucose concentrations. Additionally, the variation among sows in their ability to recover from a glucose challenge will be associated with subsequent piglet fat levels and liver glycogen levels at birth and preweaning survival. Reciprocal transfer of embryos from Meishan and crossbred gilts will explore the contributions of embryonic and maternal genotypes on development of neonatal pigs and growth of piglets prior to weaning. This will define molecular markers (genes and proteins) within uterine, fetal, and placental tissues during late gestation to examine in subsequent studies for their association with perinatal piglet survival. The association of weaning to estrous intervals with growth characteristics and age at puberty will be assessed in conjunction with determination of plasma urea nitrogen and creatinine as markers of muscle turnover. Plasma leptin and glucose will be monitored as markers for metabolic status. DNA will be genotyped and analyzed for QTLs associated with age at puberty and days to estrus after weaning.