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Knowledge of past and present genetic diversity within a breed is critical for the design and optimization of breeding programs as well as the development of strategies for the conservation of genetic resources. The Polypay sheep breed was developed at the U.S. Sheep Experiment Station (USSES) in 1968 with the goal of improving productivity in Western U.S. range flocks. It has since flourished in the more intensively managed production systems throughout the U.S. The genetic diversity of the breed has yet to be documented. Therefore, the primary objective of this study was to perform a comprehensive evaluation of the genetic diversity and population structure of U.S. Polypay sheep using both pedigree- and genomic-based methods. Pedigree data from 193 Polypay flocks participating in the National Sheep Improvement Program (NSIP) were combined with pedigree records from USSES (n = 162,997), tracing back to the breed's origin. A subset of these pedigreed sheep from 32 flocks born from 2011 to 2023 were genotyped with the GGP Ovine 50K BeadChip containing 51,867 single nucleotide polymorphisms (SNPs). Four subgroups were used for the pedigree-based analyses: 1) the current generation of animals born in 2020-2022 (n = 20,701), 2) the current generation with a minimum of four generations of known ancestors (n = 12,685), 3) only genotyped animals (n = 1,856), and 4) the sires of the current generation (n = 509). Pedigree-based inbreeding for the full population was 2.2%, with a rate of inbreeding of 0.22% per generation. Pedigree-based inbreeding, Wright's inbreeding, and genomic inbreeding based on runs of homozygosity were 2.9%, 1.3%, and 5.1%, respectively, for the genotyped population. The effective population size ranged from 41 to 249 for the pedigree-based methods and 118 for the genomic-based estimate. Expected and observed heterozygosity levels were 0.409 and 0.403, respectively. Population substructure was evident based on the fixation index (F ST ), principal component analysis, and model-based population structure. These analyses provided evidence of differentiation from the foundation flock (USSES). Overall, the Polypay breed exhibited substantial genetic diversity and the presence of a population substructure that provides a basis for the implementation of genomic selection in the breed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wilson, Petersen, Brito, Freking, Nilson, Taylor, Murphy and Lewis.)

Ovarian ultrasonography and measurement of circulating concentrations of anti-Müllerian hormone (AMH) have been used to estimate follicle number and predict fertility in mammalian females, but no study has evaluated follicle number and circulating concentrations of AMH in ewes known to differ in fertility. We tested the hypothesis that ewes that had failed to lamb (BARREN) in four consecutive annual breeding seasons of 21-35 d have fewer follicles and diminished circulating concentrations of AMH compared to closely matched ewes that consistently produced lambs (FERTILE) under the same breeding protocols. Once identified, BARREN ewes (n = 19) were paired by breed and sire to a FERTILE control ewe (n = 19) and reproductive tracts were recovered at necropsy. Visible antral follicles in both ovaries were counted and a representative cross section of one ovary was embedded for histological evaluation of pre-antral follicle numbers. Paired t-tests indicated that BARREN ewes had fewer antral follicles, fewer primordial follicles, and decreased circulating concentrations of AMH compared to FERTILE ewes (P ≤ 0.01), but there were ewes in each fertility classification that had ovarian phenotypes like the opposite fertility classification. The best technologies we have currently for estimating follicle numbers are ultrasonography and measurement of circulating concentrations of AMH, but no single technique is perfect for predicting fertility. A better understanding of the under-lying biological mechanisms linking AMH, folliculogenesis, and fertility is required to improve the use of measurements of follicle number for predicting fertility in livestock., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Published by Elsevier B.V.)

Extensive sheep systems have lower inputs (e.g., feed, labor, infrastructure) but, generally, lower outputs per ewe than intensively managed flocks. Average ewe prolificacy is low (< 1.1 lambs per ewe) across the United States and traditional expectation is that costs required to support larger litters will not be recovered due to greater lamb mortality. The Composite-IV (C-IV) is a 50% Romanov, 25% Katahdin, and 25% White Dorper hair sheep developed and selected for enhanced reproductive efficiency at the U.S. Meat Animal Research Center. Objectives of the current study were to compare productivity of C-IV ewes (N = 404) to Katahdin (N = 342) and Polypay (N = 390), two popular maternal composite breeds, in a lower-input system. Experimental ewes were exposed to either rams of their own breed or Texel rams for the first time at 7 mo of age and remained in the same mating system for up to 4 yr. Ewes lambed on pasture from May to June and were expected to rear their lambs in the absence of supplemental feed and with minimal intervention. The ewe age × breed interaction effect impacted all annually recorded traits (P < 0.01) including number and total weight of lamb marketed at 25 wk per ewe exposed to mating (LS25 and LW25, respectively). Within all ages, LS25 of C-IV was greater (1.2 to 1.63 lambs; P < 0.01) than Katahdin (0.71 to 1.17 lambs) and Polypay (0.68 to 1.26 lambs) which were similar. At 1, 2, and 3-yr of age, C-IV ewes had, on average, 12 to 17 kg greater LW25 (P ≤ 0.01) than other breeds. Polypay LW25 was similar to Katahdin at 1 yr of age, but 8 to 13 kg greater (P < 0.01) at older ages. At 4 yr of age, LW25 was similar for C-IV and Polypay (63 and 62 kg, respectively). Overall, Texel mating improved LW25 by 3 kg compared to purebred mating (P < 0.01). Twin litters were most common within mature ewes (> 1 yr) of all breeds (52% to 65%); however, the proportion of triplet litters was numerically greater for C-IV (13%) than Katahdin (1%) or Polypay (4%). The frequency of mature ewes that gave birth to and reared twins (75% to 82%) was high for all breeds. Most triplet-bearing mature C-IV ewes reared twins (43%) though many reared triplets (39%). Ewe reproductive efficiency can be enhanced in lower-input systems by utilizing additive breed effects and heterosis in a complimentary crossbreeding program. More research is needed to identify indicator traits associated with lamb survival and to derive appropriate levels of prolificacy to fit specific management constraints., (Published by Oxford University Press on behalf of the American Society of Animal Science 2022.)

Polypeptide variation encoded by the ovine transmembrane protein 154 gene (TMEM154) is associated with susceptibility to ovine lentivirus, the causative agent of Ovine Progressive Pneumonia (OPP) and Visna/Maedi. Our aim was to compare the four most prevalent TMEM154 haplotypes on the incidence of infection and ewe productivity during natural multiyear virus exposure. Prospective cohort studies were designed to test gene action and estimate effects of TMEM154 haplotypes encoding distinctive variant residues: K35 (“1”), I70 (“2”), ancestral (“3”), and A4del/M44 (“4”). Exposure consisted of co-mingling infected ewes at a rate greater than 30% with serological status evaluated every four months. For ewes with one or two copies of the highly susceptible haplotypes “2” and ”3”, the infection prevalence steadily increased to nearly 100% at 55 months. Haplotypes “2” and “3” were equally susceptible and dominant to haplotype “1”. A difference was not detected (p < 0.53) in the magnitude of effect with haplotype combinations of “1” and ”4”. The ewe infection prevalence with “1,1”; “1,4”; and “4,4” was 10% to 40% at 55 months. The latter suggested that two copies of the K35 amino acid substitution (“1”) were as effective as a homozygous TMEM154 “knockout” with the frame-shift deletion mutation (“4”) in reducing infection susceptibility. When considering ewe reproductive performance, a difference was not detected when comparing haplotypes “2”, and “3” to each other, or “1” and “4” to each other. Our study indicated that ewes with two copies of the severely truncated versions of TMEM154 (“4,4”) had normal lamb productivity. Without complete understanding of the natural function of TMEM154 our recommendations to producers interested in using TMEM154 selection to reduce their flock’s genetic predisposition to OPP are encouraged to increase the frequency of TMEM154 haplotype K35 (“1”) since it encodes a full-length protein with minimal difference to the ancestral polypeptide.

Ovine progressive pneumonia virus (OPPV) is a small ruminant lentivirus that is widespread throughout U.S. sheep flocks. Infections with OPPV are lifelong and effects are multi-systemic with significant implications for animal well-being and productivity. A protein isoform with lysine at position 35 (K35, haplotype "1") encoded by the ovine transmembrane protein 154 (TMEM154) gene has been associated with reduced susceptibility to infection when two copies are present (i.e., diplotype "1,1"). Conversely, the ancestral protein isoform with glutamate at position 35 (E35, haplotype "3") is associated with high susceptibility to infection when at least one copy is present. The beneficial effect of TMEM154 K35 alleles on ewe productivity has not been previously measured in controlled challenge experiments and was a major objective of this study. Ewes with TMEM154 diplotypes "1,1"; "1,3"; and "3,3" (n = 31, 47, and 30, respectively) were born and reared by OPPV-infected dams and managed under continual natural exposure to OPPV. Ewes were tested for serological status at 4-mo intervals for up to 5.5 yr. The incidence of infection in ewes with diplotype "1,1" was 6.5% to 9.7% and significantly lower (P < 0.001) than ewes with diplotype "1,3" (60.5 to 97.3%) or "3,3" (64.0 to 91.4%). Furthermore, the incidence among ewes with diplotype "1,1" did not increase from 10 to 67 mo of age (P > 0.99), whereas the incidence among diplotype "1,3" and "3,3" ewes increased steadily until reaching an asymptote at approximately 52 mo of age. Total number and weight of lamb weaned per ewe exposed through 5.5 yr from ewes with diplotype "1,1" far exceeded (P ≤ 0.05) those with diplotypes "1,3" and "3,3" by, on average, 2.1 lambs and 40 kg, respectively. The present study confirmed that TMEM154 diplotype "1,1" animals have reduced incidence of OPPV infection and, correspondingly, improved productivity. In flocks with a high frequency of TMEM154 haplotype "3," selection for haplotype "1" appears to be a cost-effective approach to mitigate the impact of this economically important disease., (Published by Oxford University Press on behalf of the American Society of Animal Science 2021.)

Mechanisms in the brain controlling secretion of gonadotropin hormones in pigs, particularly luteinizing hormone (LH), are poorly understood. Kisspeptin is a potent LH stimulant that is essential for fertility in many species, including pigs. Neurokinin B (NKB) acting through neurokinin 3 receptor (NK3R) is involved in kisspeptin-stimulated LH release, but organization of NKB and NK3R within the porcine hypothalamus is unknown. Hypothalamic tissue from ovariectomized (OVX) gilts was used to determine the distribution of immunoreactive kisspeptin, NKB, and NK3R cells in the arcuate nucleus (ARC). Almost all kisspeptin neurons coexpressed NKB in the porcine ARC. Immunostaining for NK3R was distributed throughout the preoptic area (POA) and in several hypothalamic areas including the periventricular and retrochiasmatic areas but was not detected within the ARC. There was no colocalization of NK3R with gonadotropin-releasing hormone (GnRH), but NK3R-positive fibers in the POA were in close apposition to GnRH neurons. Treating OVX gilts with the progestin altrenogest decreased LH pulse frequency and reduced mean circulating concentrations of LH compared with OVX control gilts (P < 0.01), but the number of kisspeptin and NKB cells in the ARC did not differ between treatments. The neuroanatomical arrangement of kisspeptin, NKB, and NK3R within the porcine hypothalamus confirms they are positioned to stimulate GnRH and LH secretion in gilts, though differences with other species exist. Altrenogest suppression of LH secretion in the OVX gilt does not appear to involve decreased peptide expression of kisspeptin or NKB., (Published by Oxford University Press on behalf of Society for the Study of Reproduction 2021.)

The continuous development and application of technology for genetic improvement is a key element for advancing sheep production in the United States. The US sheep industry has contracted over time but appears to be at a juncture where a greater utilization of technology can facilitate industry expansion to new markets and address inefficiencies in traditional production practices. Significant transformations include the increased value of lamb in relation to wool, and a downtrend in large-scale operations but a simultaneous rise in small flocks. Additionally, popularity of hair breeds not requiring shearing has surged, particularly in semi-arid and subtropical US environments. A variety of domestically developed composite breeds and newly established technological approaches are now widely available for the sheep industry to use as it navigates these ongoing transformations. These genetic resources can also address long-targeted areas of improvement such as growth, reproduction and parasite resistance. Moderate progress in production efficiency has been achieved by producers who have employed estimated breeding values, but widespread adoption of this technology has been limited. Genomic marker panels have recently shown promise for reducing disease susceptibility, identifying parentage and providing a foundation for marker-assisted selection. As the ovine genome is further explored and genomic assemblies are improved, the sheep research community in the USA can capitalize on new-found information to develop and apply genetic technologies to improve the production efficiency and profitability of the sheep industry., (© 2021 The Authors. Animal Genetics published by John Wiley & Sons Ltd on behalf of Stichting International Foundation for Animal Genetics.)

The objective of this study was to evaluate wool (Dorset and Rambouillet) and hair (Dorper, Katahdin, and White Dorper) breeds for their ability to complement Romanov germplasm in an annual fall lambing system by estimating direct maternal grandsire and sire breed effects on economically important lamb and ewe traits. After 3 yr of evaluation under spring lambing, ewes of the five F1 types were transitioned to spring mating, exposed to composite terminal sires, and evaluated under a barn lambing system at 4, 5, and 6 yr of age. A total of 527 first generation crossbred (F1) ewes produced 1,151 litters and 2,248 lambs from 1,378 May exposures. After accounting for differences in dam age, birth type, and sex, lamb survival to weaning was unaffected by maternal grandsire breed (P = 0.30). However, lambs born to 50% Dorset (16.8 ± 0.21 kg) or 50% White Dorper ewes (16.8 ± 0.28 kg) were heavier at weaning than those born to 50% Katahdin dams (13.8 ± 0.32 kg; P < 0.001). Additionally, lambs born to 50% Dorset ewes were heavier than those born to 50% Rambouillet (16.0 ± 0.22 kg) and 50% Dorper ewes (15.7 ± 0.33; P ≤ 0.03), but no other pairwise maternal grandsire breed differences were observed (P ≥ 0.06). Ewe body weight (n = 3,629) was recorded prior to each of six possible mating seasons and, across ages, was greatest for Dorset- and Rambouillet-sired ewes (56.7 ± 0.44 and 56.5 ± 0.45 kg, respectively), intermediate for Dorper- and White Dorper-sired ewes (54.7 ± 0.78 and 54.1 ± 0.64 kg, respectively), and least for Katahdin-sired ewes (51.5 ± 0.45 kg). Fertility after spring mating (0.80 ± 0.03 to 0.87 ± 0.02), litter size at birth (1.46 ± 0.09 to 1.71 ± 0.07), and litter size at weaning (1.25 ± 0.06 to 1.46 ± 0.06) were not impacted by sire breed (P ≥ 0.16). Ewe longevity, assessed as the probability of being present after 6 production years, was also not affected by sire breed (0.39 ± 0.03 to 0.47 ± 0.03; P = 0.44). Rambouillet-sired ewes weaned more total weight of lamb (21.5 ± 0.94 kg) than Katahdin-sired ewes (17.8 ± 0.94 kg; P = 0.05), but no other sire breed differences were detected (P ≥ 0.07). Results demonstrated that incorporating the Romanov into a crossbreeding system is a practical means of improving out-of-season ewe productivity., (Published by Oxford University Press on behalf of the American Society of Animal Science 2020.)

The objective was to evaluate wool (Dorset and Rambouillet) and hair (Dorper, Katahdin, and White Dorper) breeds for their ability to complement Romanov germplasm in two distinct production systems by estimating direct sire and grandsire effects on lamb growth, survival, and ewe productivity traits. Rams of the five breeds (n = 75) were mated to Romanov ewes (n = 459) over a 3-yr period to produce five types of crossbred lambs (n = 2,739). Sire breed (P > 0.06) did not impact body weight or survival traits of the first-generation crossbred (F1) lambs. The productivity of retained crossbred ewes (n = 830) mated to Suffolk and Texel terminal sires was evaluated at 1, 2, and 3 yr of age in each production system. In the intensive production system, labor and harvested feed were provided for sheep that lambed in March in barns, and ewes were limited to rearing two lambs with additional lambs reared artificially. Ewes in the extensive production system lambed in May on pasture and were responsible for rearing all lambs born with no labor or supplemental feed provided before weaning. A total of 1,962 litters and 4,171 lambs from 2,229 exposures to two terminal sire breeds (Suffolk and Texel) were produced in the experiment. Crossbred ewes in the intensive production system were mated in October, resulting in larger litter sizes than crossbred ewes mated in December for the extensive production system. However, single- and twin-born lamb mortality was similar between the two systems that differed greatly in labor, feed, and facilities. Lambs produced in the intensive system received concentrate feed from an early age and were heavier at 24 wk of age than lambs produced in the extensive system. These outcomes resulted in greater 24-wk litter weight in the intensive than in the extensive system (P < 0.0001). Unexpectedly, the relative performance of crossbred types did not differ importantly between production systems. White Dorper × Romanov crossbred ewes had numerical advantages in productivity in each system; however, differences between ewe types were not significant. In the extensive system, without labor and shelter at lambing or supplemental feed until weaning, 3-yr-old crossbred ewes of all types averaged 1.78 lambs marketed per ewe lambing, and 40% of the ewes that gave birth to triplets weaned their entire litters. These results document that prolific sheep and extensive systems can be successfully combined if appropriate crossbred types are used., (Published by Oxford University Press on behalf of the American Society of Animal Science 2020.)

The U.S. Meat Animal Research Center was the first entity in the United States to import the Romanov breed and it has been maintained as a closed flock for over 30 yr. Incorporating this super-prolific breed into crossbred and composite populations has resulted in large improvements in ewe productivity. However, few have quantified factors contributing to genetic and nongenetic variation in ewe reproduction and lamb growth within purebred Romanov populations, which were the objectives of this study. The pedigree contained a total of 8,683 lambs born to 218 and 1,600 unique sires and dams, respectively. Number of lambs born on a per ewe exposed (NLBE) and lambing (NLBL) basis were analyzed in univariate repeatability animal models. As expected, the proportion of phenotypic variance (σP2) in litter size attributable to additive genetic (0.06 to 0.08) and permanent environmental (0.05 to 0.07) effects of the ewe was low. The service sire permanent environmental effect contributed to a small but significant amount of σP2 in NLBE (0.03) but not NLBL. However, the service sire additive genetic effect did not influence σP2 in NLBE or NLBL. Lamb body weight was recorded at birth (BWB) and upon weaning from either milk replacer (~30 d; BWW-N) or their dam (~60 d; BWW-D) and were analyzed in a three-trait model with random additive direct and maternal effects. Estimated direct heritabilities were low for all body weight (BW) traits (0.07 to 0.10). Maternal heritability was moderate for BWB (0.34) but low for weaning BW (0.11 to 0.18). This was the first to report direct and maternal genetic correlations between BW of nursery- and dam-reared lambs, and both were estimated to be moderate (0.43 to 0.47). Additionally, the direct and maternal effects of BWB were more strongly correlated with BWW-N (0.74 to 0.82) than BWW-D (0.17 to 0.33). Despite inbreeding coefficients having increased at a rate of 0.33% per birth year (1986 to 2019) in this flock, they were not consistently associated with reductions in ewe or lamb performance. Parameter estimates generally agreed with those from less-prolific breeds, and results indicate that selection can be an effective means of improving subcomponents of ewe productivity., (Published by Oxford University Press on behalf of the American Society of Animal Science 2020.)

Intrauterine position and sex of adjacent fetuses in litter bearing species have been implicated in physiological and behavioral differences of offspring. The effects of uterine position and sex status of flanking fetuses with crowded uterine conditions on fetal and placental growth rate was tested. Gilts were unilaterally hysterectomized-ovariectomized at 160 d of age and mated at approximately 280 d of age, with fetal harvest at 45, 65, 85, or 105 d of gestation. Uterine position relative to the cervix, fetal status (alive, dead, sex), fetal weight, and placental weight were recorded at harvest. Each fetus was coded as adjacent to 0, 1, or 2 opposite sex fetuses and analyzed using an ANOVA fitting contemporary group, line, and flanking fetal sex code as fixed effects with sire as a random effect. The fraction of live fetuses in each classification (0, 1, 2) was 26.4%, 50.1%, and 23.4%, respectively, indicating no effect on fetal survival. Fetal weight was affected by flanking sex status between 65 d (P <  0.05) and 105 d (P <  0.001), with means at 105 d of 800.0 ± 20.3, 748.5 ± 17.8, and 672.7 ± 25.2 g, respectively for flanking sex status codes 0, 1, 2. Placental weight was similarly affected (P <  0.01) by flanking sex code, but only at 105 d. It is concluded that fetal growth and placental development in pigs is influenced by sex status of adjacent fetuses. This could be a potential source of variation in behavioral and reproductive differences later in life., (Copyright © 2019. Published by Elsevier B.V.)

Objectives were to estimate reciprocal effects of Romanov and Rambouillet breeds on survival, growth, and reproductive traits of F1 progeny and direct breed effects (Suffolk and Composite - ½ Columbia, ¼ Hampshire, and ¼ Suffolk) on survival and growth traits of the subsequent terminally sired lambs. Mature Rambouillet ewes (n = 243) were exposed to 20 Romanov rams over two seasons producing 621 lambs for evaluation of growth and survival traits with 274 F1 ewes being evaluated for reproduction traits through 4 yr of age. Similarly, mature Romanov ewes (n = 116) were exposed to 20 Rambouillet rams producing 601 lambs for evaluation of growth and survival traits with 176 F1 ewes being evaluated for reproduction traits through 4 yr of age. A total of 433 of those F1 ewes produced 3,431 lambs (1,552 litters) from 1,634 exposures to terminal sires over 4 yr. Terminal sires consisted of 38 Suffolk and 44 Composite rams. Reciprocal crossbred ewe lambs were produced from dramatically different uterine and neonatal environments, with litter size at birth from Romanov dams exceeding those from Rambouillet dams by 1.52 lambs (P < 0.001) and birth weight of lambs from Romanov dams averaged 3.41 kg compared with 4.26 kg from Rambouillet dams. Differences in BW were still evident at 140 d (P < 0.001) for dam-reared lambs. However, reciprocal ewe first breeding BW of both types were similar (P = 0.38). Minimal differences were observed in performance of reciprocal cross ewes through 4 yr for productivity, longevity, or progeny growth and survival. One exception was BW at 140 d where an interaction of dam breed with terminal sire breed reached significance for both dam-reared (P = 0.05) and nursery-reared (P = 0.02) lambs. This interaction was due to the lower weight of Composite-sired lambs out of reciprocal cross ewes born from Rambouillet dams. Composite rams increased number born (P < 0.01) and number weaned (P < 0.05) of the reciprocal cross ewes. Suffolk rams increased (P < 0.001) BW and growth rates from birth to 140 d of terminal progeny. Thus, there were little cumulative differences accrued over the 4 yr and no differences were detected for cumulative kilogram of lamb generated at 140 d per ewe exposed. The practical outcome of this evaluation was that performance levels of both types of Romanov crossbred ewes was similar allowing the industry to produce the desired crossbred ewes without needing large purebred ewe flocks of the less numerous Romanov breed.

The pubertal transition of gonadotropin secretion in pigs is metabolically gated. Kisspeptin (KISS1) and neurokinin B (NKB) are coexpressed in neurons within the arcuate nucleus of the hypothalamus (ARC) and are thought to play an important role in the integration of nutrition and metabolic state with the reproductive neuroendocrine axis. The hypothesis that circulating concentrations of luteinizing hormone (LH) and expression of KISS1 and tachykinin 3(TAC3, encodes NKB) in the ARC of female pigs are reduced with negative energy balance was tested using ovariectomized, prepubertal gilts fed to either gain or lose body weight. Restricted feeding of ovariectomized gilts caused a rapid and sustained metabolic response characterized by reduced concentrations of plasma urea nitrogen, insulin, leptin, and insulin-like growth factor-1 and elevated concentrations of free fatty acids. The secretory pattern of LH shifted from one of low amplitude to one of high amplitude, which caused overall circulating concentrations of LH to be greater in restricted gilts. Nutrient-restricted gilts had greater expression of follicle-stimulating hormone and gonadotropin-releasing hormone receptor, but not LH in the anterior pituitary gland. Expression of KISS1 in the ARC was not affected by dietary treatment, but expression of TAC3 was greater in restricted gilts. These data are consistent with the idea that hypothalamic expression of KISS1 is correlated with the number of LH pulse in pig, and further indicate that amplitude of LH pulses may be regulated by NKB in the gilt.

Objectives were to document effects of the Texel myostatin mutation (MSTN) on growth and carcass traits and also test whether or not interactions with the callipyge mutation (CLPG) could be detected. Twelve rams heterozygous at both loci on the two different chromosomes were mated to 215 terminal-sire type composite crossbred ewes genotyped as non-carriers for both loci. A total of 365 lambs were born, 362 of those were genotyped and 236 lambs contributed carcass data to estimate effects and interactions among the four genotype combinations produced. The four genotype combinations were defined as follows: ++/++ for wild-type at both loci; ++/C+ for wild-type at MSTN and heterozygous at CLPG; M+/++ for heterozygous at MSTN and wild-type at CLPG; and M+/C+ for heterozygous at both loci. The two independently segregating sire-derived alleles represent different breed-of-origin contrasts at each locus (Texel vs. composite origin for MSTN and Dorset vs. Texel origin for CLPG). Birth weight was recorded on all lambs, and subsequent body weights were adjusted to 56 (weaning), 70, and 140 d of age. Within sire-sex-genotype subgroups, naturally reared lambs were assigned to one of eight slaughter groups accounting for variation in birth date. Lambs were serially slaughtered at weekly intervals, 30 lambs per group, from roughly 26 to 33 wk of age. In addition to standard carcass traits, subjective leg scores were assigned and widths of carcasses were measured at the widest points of the shoulder and rump. Differences in birth weight were detected (P < 0.01) for the combination of the two loci and birth type, with single-born differences among genotypes exceeding differences among twin born progeny. Those interaction differences among genotypes were not as important at weaning (P = 0.36). Impact on growth rate differences among the genotypes during the post-weaning period were variable and dependent on sex of the lamb (P < 0.01). A synergistic interaction between MSTN and CLPG was observed for leg muscling scores (P < 0.05) but no other measures of carcass shape were affected. One copy of MSTN had a more modest impact on fat deposition and muscle conformation than did CLPG and did not interact (all values P > 0.20). Although some non-additive interactions that vary by trait and sex were detected, in general the data are consistent with the two mutations acting on muscle growth through independent pathways.

Background: During late gestation the placental epithelial interface becomes highly folded, which involves changes in stromal hyaluronan. Hyaluronan is composed of glucoronate and N-acetyl-glucosamine. We hypothesized that supplementing gestating dams with glucosamine during this time would support placental folded-epithelial-bilayer development and increase litter size. In Exp. 1, gilts were unilaterally hysterectomized-ovariectomized (UHO). UHO gilts were mated and then supplemented daily with 10 g glucosamine ( n  = 16) or glucose (control, n  = 17) from d 85 of gestation until slaughter (d 105). At slaughter, the number of live fetuses was recorded and each live fetus and its placenta was weighed. Uterine wall samples adjacent to the largest and smallest fetuses within each litter were processed for histology. In Exp. 2, pregnant sows in a commercial sow farm were supplemented with either 10 g glucosamine or glucose daily from d 85 of gestation to farrowing. Total piglets born and born alive were recorded for each litter. In Exp. 3, the same commercial farm and same protocol were used except that the dose of glucosamine and glucose was doubled to 20 g/d., Results: In Exp. 1, the number of live fetuses tended to be greater in glucosamine-treated UHO gilts ( P  = 0.098). Placental morphometry indicated that the width of the folded bilayer was greater ( P  = 0.05) in glucosamine-treated gilts. In Exp. 2, litter size did not differ between glucosamine- and glucose-treated sows. However in Exp. 3, the increased dose of glucosamine resulted in a significant treatment by parity interaction ( P  ≤ 0.01), in which total piglets born and born alive were greater in glucosamine treated sows of later parity (5 and 6)., Conclusions: These results indicated that glucosamine supplementation increased the width of the folds of the placental bilayer and increased litter size in later parity, intact pregnant commercial sows.

Background :  Access to sheep genome sequences significantly improves the chances of identifying genes that may influence the health, welfare, and productivity of these animals.   Methods :  A public, searchable DNA sequence resource for U.S. sheep was created with whole genome sequence (WGS) of 96 rams.  The animals shared minimal pedigree relationships and represent nine popular U.S. breeds and a composite line.  The genomes are viewable online with the user-friendly Integrated Genome Viewer environment, and may be used to identify and decode gene variants present in U.S. sheep. Results :  The genomes had a combined average read depth of 16, and an average WGS genotype scoring rate and accuracy exceeding 99%.  The utility of this resource was illustrated by characterizing three genes with 14 known coding variants affecting litter size in global sheep populations:  growth and differentiation factor 9 ( GDF9), bone morphogenetic protein 15 ( BMP15 ), and bone morphogenetic protein receptor 1B ( BMPR1B ).  In the 96 U.S. rams, nine missense variants encoding 11 protein variants were identified.  However, only one was previously reported to affect litter size ( GDF9 V371M, Finnsheep).  Two missense variants in BMP15 were identified that had not previously been reported:  R67Q in Dorset, and L252P in Dorper and White Dorper breeds. Also, two novel missense variants were identified in BMPR1B :  M64I in Katahdin, and T345N in Romanov and Finnsheep breeds.  Based on the strict conservation of amino acid residues across placental mammals, the four variants encoded by BMP15 and BMPR1B are predicted to interfere with their function.  However, preliminary analyses of litter sizes in small samples did not reveal a correlation with variants in BMP15 and BMPR1B with daughters of these rams.  Conclusions : Collectively, this report describes a new resource for discovering protein variants in silico and identifies alleles for further testing of their effects on litter size in U.S. breeds., Competing Interests: Competing interests: No competing interests were disclosed.

Mechanisms governing the timing of puberty in pigs are poorly understood. A genome-wide association study for age at first estrus in pigs identified candidate genes including neuropeptide FF receptor 2 (NPFFR2), which is a putative receptor for RFamide-related peptides (RFRP). RFRP has been shown to negatively regulate secretion of reproductive hormones from hypothalamic and pituitary tissue of pigs in culture. Here, the porcine NPFFR2 gene was further screened and four potentially functional variants were identified to be associated with age at first estrus in pigs (1,288 gilts). The RFRP neurons in the porcine hypothalamus were localized in the paraventricular and dorsomedial nuclei with RFRP fibers in the lateral hypothalamic area. There were marked changes in expression of NPFF receptors in the anterior pituitary gland and hypothalamus of gilts beginning with the peripubertal period. The hypothesis that NPFF receptor function is related to secretion of luteinizing hormone (LH) in gilts was tested with various NPFF receptor ligands. The NPFF receptor antagonist RF9 stimulated a pulse-like release of LH in prepubertal gilts. The putative NPFF receptor agonist RFRP3 modestly suppressed LH pulses in ovariectomized (OVX) prepubertal gilts. A porcine-specific RFRP2 failed to have an effect on LH secretion in OVX prepubertal gilts despite its high degree of homology to avian gonadotropin-inhibitory hormone. Results indicate that an RFRP system is present in the pig and that NPFFR2 is important for pubertal onset in gilts. It is not clear if this regulation involves major control of LH secretion or another unknown mechanism., (© Published by Oxford University Press on behalf of Society for the Study of Reproduction 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Selection for 11 generations for uterine capacity (UC) increased litter size in gilts by 1.6 more fully formed pigs at birth compared to an unselected control line (CO) despite averaging one less ovulation. The objective of the present study was to quantify line by parity interactions and characterize litter performance traits of sows in each line at later parities. Gilts farrowed in contemporary groups of 19 litters and were maintained through four parities if successfully mated in that contemporary group. A total of 243 litters and 2639 piglets were analyzed. Fixed effects of farrowing group, line, parity (1-4), and two-way interactions involving line were fitted. Sire (n=57) of the sow within farrowing group and line was fitted as a random effect. No significant line by parity interactions were observed. Parity effects were detected (P<0.01) for individual piglet birth weight, pre-weaning gain, and weaning weight. Parity effects were also detected (P<0.05) for total number born, average and total litter birth weight, and average and total litter weaning weight. Selection line differences for litter traits were detected (P<0.05) for number stillborn piglets and approached significance (P=0.06) for number of piglets weaned. Retention of sows in the herd was greater (P<0.05) with an average of 2.33 parities for the UC line females compared to 1.87 parities for the CO line. This resulted in favorable cumulative lifetime productivity of the UC line for total number of piglets born, number of piglets born alive, litter birth weight, number of piglets weaned and litter weaning weight., (Copyright © 2016. Published by Elsevier B.V.)

The objectives of this study were to determine the effect of sex, sire line, and litter size on concentrations of acyl-ghrelin and total ghrelin in plasma of grow-finish pigs and to understand the relationship of plasma concentrations of ghrelin with feeding behavior, average daily gain (ADG), and back fat in grow-finish swine. Yorkshire-Landrace crossbred dams were inseminated with semen from Yorkshire, Landrace, or Duroc sires. Within 24 h of birth, pigs were cross-fostered into litter sizes of normal (N; >12 pigs/litter) or small (S; ≤ 9 pigs/litter). At 8 wk of age, pigs (n = 240) were blocked by sire breed, sex, and litter size and assigned to pens (n = 6) containing commercial feeders modified with a system to monitor feeding behavior. Total time eating, number of daily meals, and duration of meals were recorded for each individual pig. Body weight was recorded every 4 wk. Back fat and loin eye area were recorded at the conclusion of the 12-wk feeding study. A blood sample was collected at week 7 of the study to quantify concentrations of acyl- and total ghrelin in plasma. Pigs from small litters weighed more (P < 0.05) and tended (P = 0.07) to be fatter than pigs from normal litters. Postnatal litter size did not affect ADG, feeding behavior, or concentrations of ghrelin in plasma during the grow-finish phase. Barrows spent more time eating (P < 0.001) than gilts, but the number of meals and concentrations of ghrelin did not differ with sex of the pig. Pigs from Duroc and Yorkshire sires had lesser (P < 0.0001) concentrations of acyl-ghrelin than pigs from Landrace sires, but plasma concentrations of total ghrelin were not affected by sire breed. Concentrations of acyl-ghrelin were positively correlated with the number of meals and negatively correlated with meal length and ADG (P < 0.05). A larger number of short-duration meals may indicate that pigs with greater concentrations of acyl-ghrelin consumed less total feed, which likely explains why they were leaner and grew more slowly. Acyl-ghrelin is involved in regulating feeding behavior in pigs, and measuring acyl-ghrelin is important when trying to understand the role of this hormone in swine physiology., (Published by Elsevier Inc.)

The preweaning litter environment of gilts can affect subsequent development. In a recent experiment designed to test the effects of diet on gilt development, litter-of-origin traits including individual birth weights, immunocrits (a measure of colostrum intake), sow parity, number weaned, and individual weaning weights were collected for approximately 1,200 gilts that were progeny of approximately 300 sows. Subsequently, BW, LM area, and backfat were measured at 100 d of age and at 28-d intervals until slaughter (260 d of age). From 160 d of age to slaughter, gilts were observed daily for estrus. At slaughter, the reproductive tract and 1 mammary gland were recovered. The reproductive tract was classified as cyclic or prepubertal; the number of corpora lutea was counted. Uterine horn lengths and ovarian dimensions were measured. Uterus and ovary samples from every 10th gilt were prepared for histological evaluation of uterine gland development and follicle counts, respectively. Mammary gland tissue protein and fat were assayed. Day of the estrous cycle at slaughter was calculated using the first day of the most recent standing estrus (d 0) recorded previous to slaughter. Each gilt development trait was analyzed for association with each litter-of-origin trait, after adjusting for dietary treatment effects. Uterine length, ovarian dimensions, mammary gland protein and fat, and uterine gland development were also adjusted for day of the estrous cycle at slaughter. All litter-of-origin traits were associated ( < 0.05) with growth traits. Top-down (backward elimination) multiple regression analysis indicated that BW and LM accretion in gilts was positively associated with immunocrit ( < 0.01), birth weight ( < 0.01), preweaning growth rate ( < 0.01), and parity ( < 0.01). Backfat accretion was positively associated with preweaning growth rate ( < 0.01), number weaned ( < 0.05), and parity ( < 0.05). Age at puberty was associated with birth weight (positive; < 0.01) and preweaning growth rate (negative; < 0.01). Total uterine length was positively associated with only birth weights ( < 0.05). Mammary gland protein was negatively associated with preweaning growth ( < 0.01). Mammary gland fat was positively associated with birth weight and number of piglets weaned ( > 0.05). These results indicate that colostrum consumption, birth weights, preweaning growth rate, number weaned, and parity are associated with gilt development traits during later life.

The objective of this study was to determine the effect of ad libitum feeding diets differing in standard ileal digestible (SID) lysine and ME concentrations that bracket those fed to developing gilts in U.S. commercial settings. Average SID lysine and ME concentrations in diets currently fed to developing gilts were obtained from a poll of the U.S. commercial swine industry. Crossbred Large White × Landrace gilts (n = 1,221), housed in groups, were randomly allotted to 6 corn-soybean diets in a 2 × 3 factorial arrangement formulated to provided 2 SID lysine and 3 ME concentrations. Gilts received grower diets formulated to provide 1.02% (control = survey average) or 0.86% (control minus 15%) SID lysine and 2.94, 3.25, or 3.57 (survey average ME ± 10%) Mcal of ME/kg from 100 d of age until approximately 90 kg BW. Then, gilts were fed finisher diet containing 0.85% (control = survey average) or 0.73% (control minus 15%) SID lysine and 2.94, 3.26, or 3.59 (control ± 10%) Mcal of ME/kg until 260 d of age. Gilts were weighed, and backfat thickness and loin muscle area were recorded at the beginning of the trial and then every 28 d. Starting at 160 d of age, gilts were exposed daily to vasectomized boars and observed for behavioral estrus. At approximately 260 d of age, gilts were slaughtered and their reproductive tract was collected. Each reproductive tract was examined to determine whether the gilt was cyclic, the stage of estrus cycle, ovulation rate, and uterine length. Data were evaluated for normality and analyzed using mixed model methods. Average age at puberty was 193 d of age with a range from 160 to 265 d. When all gilts on trial at 160 d of age were included in the analysis, 91.0% reached puberty as determine by observation of standing estrus. Differences between dietary treatments on age at puberty or measurements of the reproductive tract were not detected. Growth rates to 160 d were not limiting for attainment of puberty in response to daily boar stimulation from 160 d.

Crossbreeding studies between Meishan (MS) and Large White (LW) pigs have illustrated that increased piglet growth before weaning is attributed to the maternal genotype of LW dams. The objective of this study was to determine the contributions of the maternal uterine environment (MUE), piglet genotype (PigG), piglet age (PA), and their interactions on piglet growth, lactation performance, milk composition, and piglet blood profiles during lactation following reciprocal embryo transfers between MS and White crossbred (WC) gilts. Twenty-five successful pregnancies were generated by embryo transfer in 2 farrowing years representing all MUE × PigG combinations: MS × MS (n = 4 litters), MS × WC (n = 7 litters), WC × MS (n = 7 litters), and WC × WC (n = 7 litters). At d 1 and 10 and at weaning, piglets (n = 147, n = 96, and n = 94, respectively) were weighed and blood samples were collected and measured for hematocrit, hemoglobin, glucose, nitrogen, NEFA, albumin, lactate, and cortisol. In addition, sows were manually milked from a medial mammary gland to determine milk composition. All data were analyzed by ANOVA using MIXED model procedures with the fixed effects of MUE, PigG, PA, and their interactions. Piglet weight was greater (P < 0.001) in piglets from WC dams compared to MS dams at d 10 and weaning but not at d 1. In addition, ADG were greater (P < 0.05) from piglets from WC dams compared to MS dams throughout lactation. However, milk composition was greater (P < 0.05) for GE and fat content from MS dams compared to WC dams, illustrating differences in milk quality between the breeds. There were significant MUE × PigG × PA interactions for hematocrit and hemoglobin levels in which greater (P < 0.001) levels were observed in MS piglets, irrespective of MUE, at d 1 of lactation and in MS piglets from MS dams at d 10 of lactation. Blood glucose was greater (P = 0.01) at d 1 in piglets from WC dams regardless of PigG but, at weaning, glucose was greater (P = 0.01) in WC piglets regardless of MUE. Serum NEFA levels were greater (P = 0.02) in piglets from MS dams throughout the lactation period. This study demonstrated that WC dams were superior to MS dams for piglet growth during lactation, in agreement with previous crossbreeding studies. However, blood components measured displayed complex interactions between the piglet and maternal breed, which signify possible mechanisms for improved preweaning survivability but slower lactational growth of MS piglets.

Prolactin (PRL), acting via the PRL receptor (PRLR), controls hundreds of biological processes across a range of species. Endocrine PRL elicits well-documented effects on target tissues such as the mammary glands and reproductive organs in addition to coordinating whole-body homeostasis during states such as lactation or adaptive responses to the environment. While changes in PRLR expression likely facilitates these tissue-specific responses to circulating PRL, the mechanisms regulating this regulation in non-rodent species has received limited attention. We performed a wide-scale analysis of PRLR 5' transcriptional regulation in pig tissues. Apart from the abundantly expressed and widely conserved exon 1, we identified alternative splicing of transcripts from an additional nine first exons of the porcine PRLR (pPRLR) gene. Notably, exon 1.5 transcripts were expressed most abundantly in the heart, while expression of exon 1.3-containing transcripts was greatest in the kidneys and small intestine. Expression of exon 1.3 mRNAs within the kidneys was most abundant in the renal cortex, and increased during gestation. A comparative analysis revealed a human homologue to exon 1.3, hE1N2, which was also principally transcribed in the kidneys and small intestines, and an exon hE1N3 was only expressed in the kidneys of humans. Promoter alignment revealed conserved motifs within the proximal promoter upstream of exon 1.3, including putative binding sites for hepatocyte nuclear factor-1 and Sp1. Together, these results highlight the diverse, conserved and tissue-specific regulation of PRLR expression in the targets for PRL, which may function to coordinate complex physiological states such as lactation and osmoregulation., (© 2015 Society for Endocrinology.)

Litter size and birth weights are limited by uterine capacity, defined as the ability of the uterus to maintain the appropriate development of some number of conceptuses. Uterine capacity is the result of the combined effects of uterine, placental and embryo/fetal function. The number of living conceptuses that the uterus is capable of supporting is greater during early gestation compared to later gestation. Plots of log fetal weight versus log placental weight also indicate that fetal weights are less sensitive to reduced placental weight (and therefore reduced intrauterine space) in early gestation compared to late gestation. However, even in late gestation, mechanisms still exist that maintain fetal growth when the size of the placenta is reduced. One such mechanism is likely to be improved development of the folded placental-epithelial/maternal-epithelial bilayer. Fold depth, and therefore the maternal fetal interactive surface, increases as gestation advances and is greater in placenta from small fetuses. On the fetal side of the placenta, the epithelial bilayer is embedded in stromal tissue. Glycosaminoglycans are major components of stroma, including hyaluronan and heparan sulfate. Hyaluronidases and heparanases are present within placental tissues, and likely play roles in modification of stromal components to facilitate fold development. Glycosaminoglycans are polymers of forms of glucose (glucosamine, glucuronic acid, iduronic acid) suggesting that glycosaminoglycan synthesis may compete with the glucose needs of the developing fetus. Pig conceptuses are fructogenic, such that a substantial portion of glucose transferred from mother to fetus is converted to fructose. Fructose is an intermediate product in the synthesis of glucosamine from glucose, and glucosamine is linked to regulation of trophoblast cell proliferation through regulation of mTOR. These findings suggest a link between glucose, fructose, glucosamine synthesis, GAG production, and placental morphogenesis, but the details of these interactions remain unclear. In addition, recent placental epithelial transcriptome analysis identified several glucose, amino acid, lipid, vitamin, mineral and hormone transporter mechanisms within the placenta. Further elucidation of mechanisms of placental morphogenesis and solute transport could provide clues to improving nutrient transport to the pig fetus, potentially increasing litter size and piglet birth weights.

Direct selection for uterine capacity (UC) increased the number of live pigs born. A method to indirectly estimate UC in developing gilts is needed for this trait to be incorporated into commercial selection strategies. We tested the hypothesis that selection for UC alters phenotypic characteristics of the reproductive tract of prepubertal gilts and that these changes could be estimated in live animals using transrectal ultrasound (TRU). Gilts from lines selected for UC and a randomly selected control (CO) line were submitted for TRU at 130, 150, or 170 d of age and harvested 24 h later (n = 10 gilts/line per age). Diameter of the uterine horn was measured (2 to 4 measurements per animal) at TRU. At harvest, measurements of the ovary (height, width, length, weight, and number of visible follicles >1 mm) and uterine horn (weight, length, diameter, and endometrial diameter) were taken. There was no line × age interaction for any of the traits. All ovarian traits increased (P < 0.03) with age. Weight and length of the uterine horn was not different at 130 or 150 d but were increased (P < 0.01) at 170 d of age. Diameter of the uterine horn tended (P = 0.06) to be increased at 170 d compared with 130 or 150 d, but age did not affect (P = 0.38) endometrial diameter. Ovarian weight and width were increased (P < 0.01) and ovarian length and height tended (P = 0.07) to be greater for UC than CO gilts, but the number of visible follicles did not differ. The UC gilts had increased (P < 0.02) weight of uterine horns, which tended (P = 0.09) to be longer than in the CO gilts. Diameter of the uterine horn and the endometrium were greater (P < 0.01) for UC gilts than for CO gilts. Uterine horn diameter measured with TRU was not affected by age or line and was not highly correlated with any of the measured traits. Selection for increased UC results in larger ovaries and uterine horns, but TRU was not useful for estimating these traits in gilts of the age studied.

The actions of prolactin (PRL) are mediated by both long (LF) and short isoforms (SF) of the PRL receptor (PRLR). Here, we report on a genetic and functional analysis of the porcine PRLR (pPRLR) SF. Three single nucleotide polymorphisms (SNPs) within exon 11 of the pPRLR-SF give rise to four amino acid haplotypes of the intracellular domain. We identified the dimorphic insertion of a short interspersed repetitive DNA element (PRE-1) along with 32 SNPs and four other insertion/deletion sites within the 3' untranslated region (UTR) of pPRLR-SF. The PRE-1 element reduced protein translation in vitro by 75%, whereas the combination of 10 SNPs and one insertion/deletion decreased translation by 50%. Full-length cDNAs for all four haplotypes of pPRLR-SF were cloned behind the elongation factor 1-alpha promoter and functionally analyzed in vitro. None of the haplotypes could initiate transcription from the ß-casein promoter, whereas all four were dominant negatives against PRL-activation of the pPRLR-LF. Two of the haplotypes completely inhibited pPRLR-LF activity at a four-fold excess, whereas the others required a six-fold excess to impart the same effect. The ligand binding affinities of the pPRLR-SF haplotypes did not differ. Expression of the pPRLR-SF increased linearly during gestation in the endometrium and was hormonally regulated in a tissue-specific manner in the mammary glands and uterus. In conclusion, we identified a PRE-1 and other SNPs in the pPRLR-SF 3' UTR that reduce protein expression and four haplotypes of the pPRLR-SF that suppress pPRLR-LF signaling and may differentially impact the phenotypic effects of PRL in vivo., (© 2013 Stichting International Foundation for Animal Genetics.)

Gilts that reach puberty at an earlier age with more backfat have greater lifetime productivity. Increased growth rates generally promote earlier age at first estrus; however, an association of age at first estrus with discrete measures of body fatness remains controversial. We tested the hypothesis that metabolic state as determined by concentrations of plasma urea nitrogen (PUN), which reflect lean tissue growth, were correlated with age at first estrus. Blood samples were collected from gilts (n = 337) at 102, 123, and 145 d of age during development. Concentrations of albumin, creatinine, glucose, and PUN were determined. Body weight and backfat thickness were determined at each time point. From 130 to 240 d of age, gilts were monitored for first pubertal estrus. Concentrations of creatinine increased whereas concentrations of glucose decreased with increasing age (P < 0.0001). Concentrations of albumin and PUN remained relatively stable throughout development. Average daily BW gain (r = 0.22) and change in backfat thickness (r = 0.29) had a positive phenotypic correlation (P < 0.0001) with PUN at 145 d of age. Concentrations of PUN at 102 and 123 d of age were not phenotypically correlated with pubertal age, but there was a moderately negative phenotypic correlation (r = -0.22; P < 0.0001) of PUN at 145 d of age with age at first estrus along with a negative genetic correlation (r = -0.42). The relationship of PUN with age at first estrus shifted from liner to quadratic with advancing age. These data demonstrate that near the age at which gilts are selected for entry into the breeding unit, those with greater PUN have increased BW and backfat thickness and display pubertal estrus earlier but that PUN does not account for additional variation in age at first estrus beyond growth rate or backfat. It is concluded that PUN can be used to select gilts with increased efficiency of nutrient use without negatively impacting pubertal development.

Endocrine, paracrine, and autocrine prolactin (PRL) acts through its receptor (PRLR) to confer a wide range of biological functions, including its established role during lactation. We have identified a novel first exon of the porcine PRLR that gives rise to three different mRNA transcripts. Transcription of this first exon is tissue specific, where it increases during gestation in the adrenal glands and uterus. Within the mammary glands, its transcription is induced by estrogen and PRL, while in the uterus, its expression is downregulated by progestin. The promoter region has an enhancer element located between -453 and -424 bp and a putative repressor element between -648 and -596 bp. Estrogen, acting through the estrogen receptor, activates transcription from this promoter through both E-box and transcription factor AP-2 α binding sites. These findings support the concept that the multilevel hormonal regulation of PRLR transcription contributes to the various biological functions of PRL.

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.

Selection for 11 generations in swine for ovulation rate (OR) or uterine capacity (UC) resulted in significant changes in component traits of litter size. Our objective was to conserve the unique germplasm for the future and to characterize sperm quality as a correlated response to the selection criterion imposed compared with an unselected control line (CO). Boars representing genetic diversity available in all 3 lines were produced in 2 farrowing seasons. Season 1 was born in September 2005 and was sampled for semen characteristics in October 2006. Season 2 was born in March 2006 and was sampled for semen characteristics in February and March 2007. Each boar (n = 60) was collected twice. The sperm-rich fraction was obtained, and volume and concentration of sperm cells were measured to estimate total sperm production. Each ejaculate was extended 1:3 (vol/vol) with Androhep Plus (Minitube, Verona, WI) and was packed for shipping to the National Animal Germplasm Program laboratory for processing into frozen straws. Semen quality was measured by computer-assisted semen analysis at 3 semen processing points: fresh (FR), 24 h after extender added (E), and postthaw (PT). A mixed model ANOVA was applied to the data. Fixed effects of farrowing season, line, and 2-way interactions were fitted. The random effect of boar (n = 60) within farrowing season and line was used to test line differences. Sperm concentration was not different (P = 0.18) among the lines (0.594 × 10(9), 0.691 × 10(9), and 0.676 × 10(9) cells/mL for CO, OR, and UC lines, respectively). However, significance (P = 0.04) was detected for the volume of the sperm-rich fraction, greatest for OR (86.4 mL), intermediate for UC (75.5 mL), and least for CO (70.2 mL). Line differences were thus detected (P = 0.02) for total sperm production per ejaculate, greatest for OR (54.9 × 10(9)), intermediate for UC (48.7 × 10(9)), and least for CO (40.5 × 10(9)). A larger percentage of progressively motile sperm and greater estimates of sperm velocity only at processing point E (P < 0.01) were detected in favor of CO. Estimates of motility, velocity, and other parameters of sperm movement measured on E processing points were positively correlated with the same estimates obtained PT, but the magnitude was low to moderate (r range -0.03 to 0.23). Thus, selection for component traits of female reproduction had a favorable effect on total sperm production of boars.

In commercial pigs, the greatest susceptibility for pre-weaning mortality occurs in low birth-weight piglets. Despite their overall decreased birth weight, Meishan (MS) piglets have decreased pre-weaning mortality rates compared with contemporary Western breeds. The objective of the current study was to determine the contributions of the maternal uterine environment, piglet genotype, and their interaction on the development of neonatal piglets pertaining to pre-weaning survivability using reciprocal embryo transfer between MS and White crossbred (WC) pigs. Twenty-five successful pregnancies were produced from 2 farrowing seasons, generating litters of maternal uterine environment (MUE) by piglet genotype (PigG) combinations; MS × MS (n = 4 litters), MS × WC (n = 7 litters), WC × MS (n = 7 litters), and WC × WC (n = 7 litters). At approximately 24 h of age (Day 1), piglets (n = 173) were weighed and a blood sample was taken. Hematocrit, hemoglobin, glucose, plasma urea nitrogen, albumin, NEFA, lactate, and cortisol were measured in all blood samples. Representative piglets (n = 46) from each litter were harvested and body measurements (i.e., organ weights, tissue glycogen content, and body composition) were determined. Piglet data were analyzed by ANOVA using MIXED model procedures. Both MUE (P < 0.001) and PigG (P < 0.01) affected piglet BW, illustrating that piglets gestated in WC gilts were heavier than piglets gestated in MS gilts, and WC piglets were heavier than MS piglets. Serum albumin concentrations were increased (P < 0.05) in MS piglets compared with WC piglets, indicating greater liver maturity. Significant MUE × PigG interactions were observed for hematocrit and hemoglobin, in which the greatest concentrations were observed in MS piglets gestated in MS and WC gilts, and the lowest concentrations were observed in WC piglets gestated in WC gilts, demonstrating increased oxygen-carrying capability. The percentage of fat and nitrogen, as well as the GE of the body, were greater (P < 0.05) in MS piglets, indicating greater energy stores. Liver, bicep femoris, and LM glycogen concentrations were greater (P < 0.01) in WC piglets compared with MS piglets, demonstrating increased glycogen catabolism in MS piglets. This study demonstrated limited interactions between the maternal uterine environment and piglet genotype on weaning survivability potential, suggesting that the MS piglet is a viable model for pre-weaning survivability.

The ovary and placenta are dynamic structures requiring constant modification both structurally and through cell-cell communication capabilities. The extracellular matrix and basement membranes are primarily composed of a milieu of glycosaminoglycans, including heparan sulfate and hyaluronan. Heparanase (HPSE) and hyaluronidases (HYAL) are responsible for degrading heparan sulfate and hyaluronan, respectively. Therefore, the objective of this study was to evaluate the relationship of SNPs distinct to HPSE, HYAL1, and HYAL2 with measurements of reproduction and production traits in swine. Single trait associations were performed on a Landrace-Duroc-Yorkshire population using SNPs discovered and identified in HPSE, HYAL1, and HYAL2. Analyses were conducted on an extended pedigree and SNPs were found to be associated with reproductive and production traits. Prior to multiple-testing corrections, SNPs within HPSE were weakly associated (P < 0.03) having additive effects with age at puberty (-2.5 ± 1.08 days), ovulation rate (0.5 ± 0.24 corpora lutea), and number of piglets born alive (0.9 ± 0.44 piglets). A HYAL1 and two HYAL2 SNP were nominally associated (P ≤ 0.0063) with number of piglets born alive after multiple-testing corrections (effects between 1.02 and 1.44 piglets), while one of the same HYAL2 markers maintained a modest association (P = 0.0043) having a dominant effect with number of piglets weaned (1.2 ± 0.41 piglets) after multiple-testing correction. Functionally, HPSE and HYAL1 and 2 have been shown to participate in events related to ovarian and placental activity. SNPs from these studies could potentially assist with understanding genetic components underlying sow lifetime productivity as measured by piglet survivability based on number born alive and number weaned, thereby contributing to a greater number of pigs/sow/year.

A substantial loss of embryos occurs between Days 30 and 40 of pregnancy in the pig under crowded intrauterine conditions, but it is not clear whether this loss affects the growth of adjacent conceptuses. Birth intervals are known to increase with decreasing litter size, but the factors responsible are unknown. Two possibilities are that increased birth weight associated with reduced litter size and the empty uterine space and resulting constricted uterine regions that occur in pigs with small litters may impair piglet delivery. To address these, pregnant gilts were laparotomized on Day 35 of pregnancy and one or two fetuses were manually crushed through the uterine wall on the ovarian or cervical end of each uterine horn to create an empty uterine space behind or in front of the litter of piglets, respectively, in relation to the route of delivery from the uterus. A subset of gilts was slaughtered at 105 days of gestation to confirm that the empty uterine spaces were successfully created and to determine their effects on placental and fetal weights of adjacent conceptuses. At slaughter, the lengths of all externally visible empty constricted regions of the uterus were measured. The uterine horns were opened and the lengths of each placenta were measured from the umbilicus toward the ovary and toward the cervix to assess whether placentas developed symmetrically, and then each fetus and placenta was weighed. Fetal crushing successfully created constricted empty uterine regions on the ovarian and cervical ends of the uterine horns. Ovarian-side placental lengths were greater than cervical-side for conceptuses adjacent to fetuses crushed on the ovarian end of the horn. Cervical-side placental lengths were greater than ovarian-side for conceptuses adjacent to fetuses crushed on the cervical end. Both placental and fetal weights were greater (10% and 6%, respectively, P<0.05) for conceptuses adjacent to crushed fetuses compared to nonadjacent conceptuses. Remaining gilts were farrowed to determine the effect of litter size, average birth weights, and treatment on birth intervals of piglets, which were monitored using 24-h video surveillance. The negative association between number of piglets born alive and average birth interval was confirmed and was not explained by litter size-induced reduction in litter average birth weights. Birth intervals and stillbirth rate did not differ between cervically- and ovarian-treated gilts. These results indicate that conceptus loss on Day 35 of gestation can benefit the growth of adjacent placentas and fetuses, but the benefit is small. Increased average birth weight and the presence of empty uterine space that occurs when litter size is reduced does not fully explain the effect of litter size on birth intervals., (Published by Elsevier B.V.)

Background: Genetic predisposition to scrapie in sheep is associated with several variations in the peptide sequence of the prion protein gene (PRNP). DNA-based tests for scoring PRNP codons are essential tools for eradicating scrapie and for evaluating rare alleles for increased resistance to disease. In addition to those associated with scrapie, there are dozens more PRNP polymorphisms that may occur in various flocks. If not accounted for, these sites may cause base-pair mismatching with oligonucleotides used in DNA testing. Thus, the fidelity of scrapie genetic testing is enhanced by knowing the position and frequency of PRNP polymorphisms in targeted flocks., Results: An adaptive DNA sequencing strategy was developed to determine the 771 bp PRNP coding sequence for any sheep and thereby produce a consensus sequence for targeted flocks. The strategy initially accounted for 43 known polymorphisms and facilitates the detection of unknown polymorphisms through an overlapping amplicon design. The strategy was applied to 953 sheep DNAs from multiple breeds in U.S. populations. The samples included two sets of reference sheep: one set for standardizing PRNP genetic testing and another set for discovering polymorphisms, estimating allele frequencies, and determining haplotype phase. DNA sequencing revealed 16 previously unreported polymorphisms, including a L237P variant on the F141 haplotype. Two mass spectrometry multiplex assays were developed to score five codons of interest in U.S. sheep: 112, 136, 141, 154, and 171. Reference tissues, DNA, trace files, and genotypes from this project are publicly available for use without restriction., Conclusion: Identifying ovine PRNP polymorphisms in targeted flocks is critical for designing efficient scrapie genetic testing systems. Together with reference DNA panels, this information facilitates training, certification, and development of new tests and knowledge that may expedite the eradication of sheep scrapie.

The trophoblast-endometrial epithelial cell bilayer of porcine placenta undergoes microscopic folding during gestation, and the folded bilayer is embedded in fetal placental stroma. We hypothesized that hyaluronan was a component of fetal placental stroma, and that hyaluronoglucosaminidases played a role in bilayer folding. Gilts were unilaterally hysterectomized-ovariectomized (UHO) at 160 days of age, mated at estrus and killed on days 25, 45, 65, 85 or 105 of gestation. Fetal placental tissues were collected to evaluate hyaluronan and hyaluronoglucosaminidase content. Fetal placental hyaluronan concentration increased (P<0.01) between day 25 and 45 of gestation, remained high throughout gestation, and was greater (P<0.05) in the fetal placenta of the smallest compared to the largest fetuses on day 105 of gestation. Hyaluronan was localized to fetal placental stroma. Three cDNAs for hyaluronoglucosaminidase 1 (two 1379 and one 1552bp) and one cDNA (1421bp) for hyaluronoglucosaminidase 2 were cloned from day-85 fetal placental RNA. Gene expression analysis indicated that the 1379bp form of hyaluronoglucosaminidase 1 mRNA did not differ, the 1552bp form increased, and the 1421bp form of hyaluronoglucosaminidase 2 decreased during pregnancy. Amount of all three mRNAs was greater (P<0.05) in fetal placenta of the smallest compared to the largest fetuses. Zymography indicated 70 and 55kd protein isoforms of hyaluronoglucosaminidase in fetal placental tissue. Both forms increased with advancing gestation and were greater in fetal placenta of the smallest compared to the largest fetuses (P<0.05). These results are consistent with a role for hyaluronan and hyaluronoglucosaminidases in the development of the microscopic folds of the pig placenta during gestation., (Published by Elsevier B.V.)

To increase our understanding of imprinted genes in swine, we carried out a comprehensive analysis of this gene family using two complementary approaches: expression and phenotypic profiling of parthenogenetic fetuses, and analysis of imprinting by pyrosequencing. The parthenote placenta and fetus were smaller than those of controls but had no obvious morphological differences at Day 28 of gestation. By Day 30, however, the parthenote placentas had decreased chorioallantoic folding, decreased chorionic ruggae, and reduction of fetal-maternal interface surface in comparison with stage-matched control fetuses. Using Affymetrix Porcine GeneChip microarrays and/or semiquantitative PCR, brain, fibroblast, liver, and placenta of Day 30 fetuses were profiled, and 25 imprinted genes were identified as differentially expressed in at least one of the four tissue types: AMPD3, CDKN1C, COPG2, DHCR7, DIRAS3, IGF2 (isoform specific), IGF2AS, IGF2R, MEG3, MEST, NAP1L5, NDN, NNAT, OSBPL1A, PEG3, APEG3, PEG10, PLAGL1, PON2, PPP1R9A, SGCE, SLC38A4, SNORD107, SNRPN, and TFPI2. For DIRAS3, PLAGL1, SGCE, and SLC38A4, tissue-specific differences were detected. In addition, we examined the imprinting status of candidate genes by quantitative allelic pyrosequencing. Samples were collected from Day 30 pregnancies generated from reciprocal crosses of Meishan and White Composite breeds, and single-nucleotide polymorphisms were identified in candidate genes. Imprinting was confirmed for DIRAS3, DLK1, H19, IGF2AS, NNAT, MEST, PEG10, PHLDA2, PLAGL1, SGCE, and SNORD107. We also found no evidence of imprinting in ASB4, ASCL2, CD81, COMMD1, DCN, DLX5, and H13. Combined, these results represent the most comprehensive survey of imprinted genes in swine to date.

Prolactin (PRL) acts through its receptor (PRLR) via both endocrine and local paracrine/autocrine pathways to regulate biological processes including reproduction and lactation. We analyzed the tissue- and stage of gestation-specific regulation of PRL and PRLR expression in various tissues of pigs. Abundance of pPRLR-long form (LF) mRNA increased in the mammary gland and endometrium during gestation while in other tissues it remained constant. There was a parallel increase in the abundance of the pPRLR-LF protein in the mammary gland and endometrium during gestation. We determined the hormonal regulation of pPRLR-LF mRNA expression in various tissues from ovariectomized, hypoprolactinemic gilts given combinations of the replacement hormones estrogen (E(2)), progestin (P), and/or haloperidol-induced PRL. Abundance of pPRLR-LF mRNA in kidney and liver was unaffected by hormone treatments. Expression of uterine pPRLR-LF mRNA was induced by E(2) whereas the effect of E(2) was abolished by co-administering P. The expression of pPRLR-LF mRNA in the mammary gland stroma was induced by PRL, whereas E(2) induced its expression in the epithelium. In contrast to these changes in pPRLR expression, pPRL expression was relatively constant and low during gestation in all tissues except the pituitary. Taken together, these data reveal that specific combinations of E(2), P, and PRL differentially regulate pPRLR-LF expression in the endometrium and mammary glands, and that the action of PRL on its target tissues is dependent upon pPRLR-LF abundance more so than the local PRL expression.

Heparanase (HPSE) is an endoglycosidase that specifically degrades heparan sulfate, which is an abundant glycosaminoglycan of the pig placenta. The aim of the present study was to clone cDNA encoding porcine HPSE and characterise the expression level and localisation of HPSE mRNA in porcine placentas throughout gestation. Placental tissues were collected from litters on Days 25, 45, 65, 85 and 105 of gestation. Three transcript variants similar to HPSE were identified in the pig placenta. In addition, the HPSE gene was mapped to pig chromosome 8 in close proximity to quantitative trait loci for litter size and prenatal survival. Real-time polymerase chain reaction and in situ hybridisation were used to characterise the expression of two HPSE variants, namely HPSE v1 and v2, in the pig placenta throughout gestation. The expression of HPSE v1 and v2 was elevated (P < 0.01) in placentas during very early gestation (Day 25) as well as during late gestation (Days 85 and 105). Finally, HPSE v1 and v2 mRNA were localised to the cuboidal trophoblast cells of the folded bilayer located nearest to the maternal endometrium. These findings illustrate that HPSE likely plays a role in the development and modification of the pig placenta, which has implications for litter size and prenatal survival.

Placental insufficiency results in fetal loss, low birth weight, stillbirth, preweaning mortality and poor growth. Placental development begins at conceptus elongation, which is a primary factor controlling the size of the placenta. After elongation, the allantois develops outward from the embryo to establish the allantochorion, which defines the size of the functional placenta. During implantation, chorionic trophoblasts adhere to endometrial epithelial cells. Placental structures known as areolae develop at the openings of the endometrial glands and take up endometrial gland secreted products (histotrophe). Between day 30 and 35 of gestation, the adhered trophoblast-endometrial epithelial bilayer undergoes microscopic folding. Fetal and maternal capillaries develop adjacent to the bilayer and blood flows are arranged in a cross-countercurrent manner. Except for nutrients secreted by the glands, nutrient exchange takes place between these capillaries within these folds. By day 85, the folds deepen and become more complex, increasing surface area. The epithelial bilayer thins and capillaries indent the plane of each layer (but do not penetrate), reducing distance between capillaries. The folded bilayer is surrounded by endometrial stroma on the maternal side and placental stroma on the fetal side. The fetal-placental stroma is partially composed of glycosaminoglycans, the most abundant being hyaluronan and heparan sulfate. Changes in both hyaluronoglucosaminidase and heparanase during placental development suggest that these enzymes play a role in placental development. In addition to structural modifications, various nutrient specific transport mechanisms exist. These mechanisms are likely to be as important to transport of specific nutrients as placental size or structure.

This chapter describes the application of functional genomic approaches to the study of imprinted genes in swine. While there are varied definitions of "functional genomics", in general they focus on the application of DNA microarrays, single nucleotide polymorphism (SNP) arrays, and other high coverage genomic analyses, and their combination with downstream methods of gene modification such as silencing RNA (siRNA) and viral and non-viral transfection. Between the initial data acquisition and the actual genetic manipulation of the system lies bioinformatics, where massive amounts of data are analyzed to extract meaningful information. This area is in constant flux with an increased emphasis on detection of affected pathways and processes rather than generation of simple affected gene lists. We will expand on each of these points and describe how we have used these technologies for the study of imprinted genes in swine. First we will introduce the biological question to provide context for the discussion of the functional genomic approaches and the types of information they generate.

Lines of pigs selected for increased uterine capacity have improved conceptus survival, whereas pigs selected for increased ovulation rate have decreased conceptus survival relative to an unselected control line. The objective of this study was to evaluate conceptus development during blastocyst elongation as a potential contributing factor to differences in conceptus survival rate among these pig lines. Conceptuses were recovered from pregnant control, uterine capacity, and ovulation rate line gilts at d 10 and 12 of gestation. At d 10 of gestation, conceptus morphologic diversity was assessed by comparing within-litter average conceptus diameter and the standard deviation of conceptus diameters. At d 12 of gestation, conceptus morphologic diversity was assessed by comparing blastocyst populations obtained from individual gilts. Real-time PCR analyses for transcripts involved in steroidogenesis, cellular differentiation, and immune responsiveness were performed on spherical, ovoid, and filamentous conceptuses recovered from these selection lines. Uterine flushings were also assayed for total protein and estradiol-17beta at d 10 and 12 of gestation. Morphological data were analyzed using ANOVA with the fixed effects of line, farrowing season, and their interactions. Conceptus mortality, uterine flushing, and real-time PCR data were analyzed using ANOVA with the fixed effects of line, day or blastocyst morphology, farrowing season, and their interactions. Conceptus mortality, measured as the ratio of conceptus recovery to ovulation rate, was not different between the lines on d 10 and 12 of gestation. There were no significant line effects for conceptus morphologic diversity at d 10 and 12 of gestation. Expression of transcripts associated with steroidogenesis (steroidogenic acute regulatory protein, cytochrome P450 side chain cleavage, and aromatase), cellular differentiation (cytokeratin-18 and vimentin), and immune responsiveness (interleukin-1beta) in spherical, ovoid, and filamentous conceptuses was not different between the lines. Furthermore, protein and estradiol-17beta in uterine flushings at d 10 and 12 of gestation were not different between the selection lines. These findings indicate limited, if any, deviations between these lines of pigs in conceptus development during blastocyst elongation and suggest that mechanisms involved in generating line differences in survival rate likely are manifested later in gestation.

Background: Genome-wide detection of single feature polymorphisms (SFP) in swine using transcriptome profiling of day 25 placental RNA by contrasting probe intensities from either Meishan or an occidental composite breed with Affymetrix porcine microarrays is presented. A linear mixed model analysis was used to identify significant breed-by-probe interactions., Results: Gene specific linear mixed models were fit to each of the log2 transformed probe intensities on these arrays, using fixed effects for breed, probe, breed-by-probe interaction, and a random effect for array. After surveying the day 25 placental transcriptome, 857 probes with a q-value < or = 0.05 and |fold change| > or = 2 for the breed-by-probe interaction were identified as candidates containing SFP. To address the quality of the bioinformatics approach, universal pyrosequencing assays were designed from Affymetrix exemplar sequences to independently assess polymorphisms within a subset of probes for validation. Additionally probes were randomly selected for sequencing to determine an unbiased confirmation rate. In most cases, the 25-mer probe sequence printed on the microarray diverged from Meishan, not occidental crosses. This analysis was used to define a set of highly reliable predicted SFPs according to their probability scores., Conclusion: By applying a SFP detection method to two mammalian breeds for the first time, we detected transition and transversion single nucleotide polymorphisms, as well as insertions/deletions which can be used to rapidly develop markers for genetic mapping and association analysis in species where high density genotyping platforms are otherwise unavailable.SNPs and INDELS discovered by this approach have been publicly deposited in NCBI's SNP repository dbSNP. This method is an attractive bioinformatics tool for uncovering breed-by-probe interactions, for rapidly identifying expressed SNPs, for investigating potential functional correlations between gene expression and breed polymorphisms, and is robust enough to be used on any Affymetrix gene expression platform.

Two cell lines, designated MARC.OVSM, and MARC.OKF, were initiated from the aorta and kidney, respectively, obtained from the Texel ram used to make the CHORI-243 Ovine BAC library. These cell lines have been submitted to the NIA Aging Cell Repository at the Coriell Cell Respositories, Camden, NJ, USA, and will be made publicly available.

The efficiency of nutrient transport from the pregnant female pig to the developing fetus depends on the size and function of the placenta. It has been reported that maternal and fetal blood vessels are arranged in a cross-countercurrent arrangement within placental microscopic folds. Thus, the blood supplies are in close apposition to each other within these microscopic folds, and maternal and fetal blood flows in approximately opposite directions perpendicular to the plane of the placenta. This arrangement indicates that the width of the microscopic folds influences placental efficiency. The objective of this study was to determine whether differences in pig placental microscopic fold development are associated with differences in fetal size or are influenced by selection for ovulation rate or uterine capacity. Gilts from a randomly selected control line, a line selected for ovulation rate, and a line selected for uterine capacity were slaughtered, and uterine wall samples were collected within the placentas associated with the largest and smallest fetuses in each litter on d 45, 65, 85, and 105 of gestation. The uterine wall samples were processed for histology and analyzed using computer-assisted morphometry. Average width of the placental folds and average width of the placental stroma above the folds were measured. To measure fold complexity, the length of the epithelial bilayer for a given length of placenta was also measured. The width of the folded bilayer increased significantly from d 65 to 105 and was greater in placentas associated with small fetuses compared with large fetuses on d 105 of gestation. In contrast, the width of the placental stroma above the folded bilayer decreased with gestation and decreased more rapidly in placenta associated with the smallest compared with the largest fetus. These results indicate that the width of the microscopic folds of the placental trophoblast/endometrial epithelial bilayer is increased in placenta associated with small fetuses, which we hypothesize will increase the surface area for interaction between maternal and fetal blood supplies, thus improving placental efficiency in response to reduced placental size.

Selection for 11 generations in swine for ovulation rate (OR) or uterine capacity (UC) resulted in 19.6% greater prenatal survival at term in UC compared with OR. Our objective was to characterize the number of fetuses throughout gestation in each line, including an unselected control (CO) line. Five hundred ninety-three gilts produced over 4 farrowing seasons were subjected to unilateral-hysterectomy-ovariectomy at 160 d of age and mated within line at 280 d of age. Gilts were assigned within sire family to be slaughtered (+/- 2 d) at d 25, 45, 65, 85, or 105 of gestation. Ovulation rate and number of live and dead fetuses were recorded for each pregnant gilt (n = 402). Fetal and placental weights were also recorded. Ovulation rate of OR line gilts (18.0 +/- 0.3 ova) exceeded (P < 0.001) CO and UC lines (15.0 +/- 0.3 and 14.0 +/- 0.3 ova, respectively). Line and gestational age interacted to affect number of live fetuses (P < 0.001). Least squares means for CO were 10.1, 8.3, 7.2, 6.7, and 7.3 live fetuses for d 25, 45, 65, 85, and 105, respectively (average SE = 0.46 fetuses). Corresponding means for OR were 13.4, 8.3, 7.9, 6.5, and 6.7 live fetuses, respectively (average SE = 0.44 fetuses). Means for UC were 10.2, 9.0, 8.5, 7.5, and 8.0 live fetuses, respectively (average SE = 0.47 fetuses). In each line, number of live fetuses at d 25 was approximately 72% of ovulation rate. Mortality to d 45 was greatest in OR, intermediate in CO, and least in UC. Reductions in live fetuses continued to occur from d 45 to 105, but line differences at d 45 were essentially maintained to d 105. Number of live fetuses in gilts at d 114 was estimated from each of the survival curves and predicted values of 7.0, 5.9, and 7.8 per uterine horn for CO, OR, and UC lines, respectively. Selection for uterine capacity improved fetal survival primarily during the time period between d 25 and 45. Relative growth rate coefficients throughout gestation for placental tissue indicated a change in rank of the line means, implicating a relative later growth pattern of placental tissue in the UC line.

Single nucleotide polymorphisms (SNPs) have become an important type of marker for commercial diagnostic and parentage genotyping applications as automated genotyping systems have been developed that yield accurate genotypes. Unfortunately, allele frequencies for public SNP markers in commercial pig populations have not been available. To fulfil this need, SNP markers previously mapped in the USMARC swine reference population were tested in a panel of 155 boars that were representative of US purebred Duroc, Hampshire, Landrace and Yorkshire populations. Multiplex assay groups of 5-7 SNP assays/group were designed and genotypes were determined using Sequenom's massarray system. Of 80 SNPs that were evaluated, 60 SNPs with minor allele frequencies >0.15 were selected for the final panel of markers. Overall identity power across breeds was 4.6 x 10(-23), but within-breed values ranged from 4.3 x 10(-14) (Hampshire) to 2.6 x 10(-22) (Yorkshire). Parentage exclusion probability with only one sampled parent was 0.9974 (all data) and ranged from 0.9594 (Hampshire) to 0.9963 (Yorkshire) within breeds. Sire exclusion probability when the dam's genotype was known was 0.99998 (all data) and ranged from 0.99868 (Hampshire) to 0.99997 (Yorkshire) within breeds. Power of exclusion was compared between the 60 SNP and 10 microsatellite markers. The parental exclusion probabilities for SNP and microsatellite marker panels were similar, but the SNP panel was much more sensitive for individual identification. This panel of SNP markers is theoretically sufficient for individual identification of any pig in the world and is publicly available.

Background: Presently, multiple options exist for conducting gene expression profiling studies in swine. In order to determine the performance of some of the existing microarrays, Affymetrix Porcine, Affymetrix Human U133+2.0, and the U.S. Pig Genome Coordination Program spotted glass oligonucleotide microarrays were compared for their reproducibility, coverage, platform independent and dependent sensitivity using fibroblast cell lines derived from control and parthenogenic porcine embryos., Results: Array group correlations between technical replicates demonstrated comparable reproducibility in both Affymetrix arrays. Glass oligonucleotide arrays showed greater variability and, in addition, approximately 10% of probes had to be discarded due to slide printing defects. Probe level analysis of Affymetrix Human arrays revealed significant variability within probe sets due to the effects of cross-species hybridization. Affymetrix Porcine arrays identified the greatest number of differentially expressed genes amongst probes common to all arrays, a measure of platform sensitivity. Affymetrix Porcine arrays also identified the greatest number of differentially expressed known imprinted genes using all probes on each array, an ad hoc measure of realistic performance for this particular experiment., Conclusion: We conclude that of the platforms currently available and tested, the Affymetrix Porcine array is the most sensitive and reproducible microarray for swine genomic studies.

We hypothesized that the ability of the fetus to alter nutrient shunting and organ growth might be associated with uterine capacity. White crossbred gilts from a randomly selected control line, a line selected for ovulation rate, and a line selected for uterine capacity (UC) were unilaterally hysterectomized-ovariectomized at 160 d of age, mated at estrus, and slaughtered at 45, 65, 85, and 105 d of gestation (9 to 18 gilts for each line x day combination). Analysis of the data revealed that heart weights and fetal weights were decreased in the ovulation rate line. No significant differences were obtained in fetal, placental, or fetal organ weights between the control and UC lines. Allometric growth of organs was assessed by examination of the slopes of the relationships between fetal weights and fetal organ weights after natural log transformation. Only the relative growth of the liver differed between selection lines and was greater (P = 0.01) in the UC compared with the control line during early pregnancy (d 45 and 65). Allometric growth of the fetal brain, liver, and heart differed with day of gestation. A brain-sparing effect was greater (P < 0.01) on d 85 and 105 compared with d 45 and 65. By contrast, a heart-sparing effect was present during early gestation and disappeared in later gestation. Fetal liver weights were hypersensitive to differences in fetal weights on d 45, possibly associated with placental effects on fetal liver weight. Fetal spleen weights were proportional to fetal weights throughout gestation. These results indicate that selection for ovulation rate decreased total fetal and fetal heart weights, and that selection for UC altered the relationship between total fetal and fetal liver weights during early gestation. Results further indicate significant changes in allometric growth of organs during gestation.