Litter-of-origin trait effects on gilt development.

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.

Age at puberty, ovulation rate, and uterine length of developing gilts fed two lysine and three metabolizable energy concentrations from 100 to 260 d of age.

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.

Differences in transcript abundance of genes on BTA15 located within a region associated with gain in beef steers.

Using results from a previous GWAS, we chose to evaluate seven genes located within a 229Kb region on BTA15 for variation in RNA transcript abundance in a library of tissue samples that included adipose, liver, rumen papillae, spleen, muscle, and small intestine epithelial layers from the duodenum, ileum and jejunum collected from steers (n = 14) with positive and negative residual GN near mean dry matter intake (DMI). The genes evaluated were two olfactory receptor-like genes (LOC525033 and LOC618173), RRM1, STIM1, RHOG, PGAP2, and NUP98. The rumen papillae transcript abundance of RHOG was positively correlated with residual GN (P = 0.02) and ruminal STIM1 exhibited a trend towards an association with residual GN (P = 0.08). The transcript abundance of one olfactory receptor (LOC618173) in the ileum was also positively associated with residual GN (P = 0.02) and PGAP2 and LOC525033 in the ileum displayed trends for association with GN (P ≤ 0.1). To further evaluate the differential expression detected in the ileum and rumen of these animals, the transcript abundance of STIM1 and RHOG in the rumen and of PGAP2 and the olfactory receptors in the ileum were assessed in an additional group of 32 animals with divergent average daily gain (ADG) and average daily feed intake (ADFI) collected over two groups. The olfactory receptor, LOC525033, was not expressed in the ileum for the majority of these animals. Only RHOG showed a slight, but non-significant trend towards greater expression in animals with greater gain. We have detected differences in the transcript abundance of genes within this region in the rumen and ileum of animals selected for greater and less residual gain; however, we were unable to validate the expression of these genes in the larger group of cattle possibly due to the differences in phenotype or contemporary group.

Relationships between day one piglet serum immunoglobulin immunocrit and subsequent growth, puberty attainment, litter size, and lactation performance.

Colostrum affects gut and uterine gland development in the neonatal piglet, suggesting that subsequent growth and reproductive performance may be affected. Measuring immunoglobulin in piglet serum using the immunoglobulin immunocrit on Day 1 of age provides a simple, inexpensive indication of the amount of colostrum acquired by the piglet in the first day of life. Relationships between serum immunoglobulin immunocrit measures and subsequent growth rates, age at puberty, incidence of puberty failure, litter size, and lactation performance were examined in pigs born and subsequently farrowing between 2009 and 2013. Immunoglobulin immunocrit measures were collected on 16,762 piglets on Day 1 of age. Of these piglets, BW measurements were available from 15,324 (7,684 males and 7,640 females) piglets at a range of ages from weaning to 200 d of age, allowing an assessment of growth rates. Age at puberty was recorded from a subset of 2,857 of the females after observing them for estrous behavior from approximately 170 to 250 d of age. To examine relationships between d 1 immunocrit and puberty failure, gilts with immunocrit measures that failed to reach puberty (n = 119) were matched with littermate gilts with immunocrit measures that achieved puberty (n = 167). Similarly, number born alive was collected on a subset (n = 799) of females from first to fourth parities for which d 1 immunocrits were measured on them as neonates. Finally, d 1 immunocrit effect on adult lactational competence was assessed by measuring litter average (offspring of 440 females) and litter average piglet preweaning growth rate (offspring of 774 females) in females where d 1 immunocrits were available from them as neonates. Results indicated that low d 1 immunocrits were subsequently associated with reduced growth (P < 0.01), increased age at puberty (P < 0.01), reduced number born alive (P < 0.05), reduced litter average immunocrit (P < 0.05), and reduced litter average preweaning growth rate during lactation (P < 0.05). This suggests that management efforts to improve the amount of colostrum ingested by neonatal piglets would result in beneficial changes in production efficiency, particularly for gilts destined for the breeding herd. It also suggests that the immunoglobulin immunocrit can be useful in monitoring colostrum ingestion to maximize the beneficial effects of colostrum on subsequent performance.

Contributions of the maternal uterine environment and piglet genotype on weaning survivability potential: II. Piglet growth, lactation performance, milk composition, and piglet blood profiles during lactation following reciprocal embryo transfers between Meishan and White crossbred gilts.

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.

Genomewide association analysis for average birth interval and stillbirth in swine.

Reproductive efficiency has a great impact on the economic success of pork production. Stillborn pigs and average birth interval contribute to the number of pigs born alive in a litter. To better understand the underlying genetics of these traits, a genomewide association study was undertaken. Samples of DNA were collected and tested using the Illumina Porcine SNP60 BeadChip from 798 females farrowing over a 4-yr period (all first parity). Birth intervals and piglet birth status (stillborn or alive) were determined by videotaping each farrowing event. A total of 41,148 SNP were tested using the Bayes C option of GenSel (version 4.61) and 1-Mb windows. These 1-Mb windows explained proportions of 0.017, 0.002, 0.032, 0.029, and 0.030 of the total variation, respectively, for litter average birth interval after deletion of the last piglet born, last birth interval in the litter, number of stillborn piglets ignoring the last piglet born, number of stillborns in the last birth position, and percent stillborn ignoring the last piglet. Significant 1-Mb nonoverlapping SNP windows were identified by using a conservative approach requiring 1-Mb windows to have a genetic variance ≥1.0% of genomic variance and these were considered to be QTL. Quantitative trait loci were located for number of stillborn piglets ignoring the last piglet born (1 QTL), number of stillborns in the last birth position (1 QTL), and percent stillborn ignoring the last piglet (3 QTL). In addition, 2, 13, 3, and 6 suggestive 1-Mb nonoverlapping SNP windows were identified for litter average birth interval after deletion of the last piglet born, number of stillborn piglets ignoring the last piglet born, number of stillborns in the last birth position, and percent stillborn ignoring the last piglet, respectively. Possible candidate genes affecting both birth interval and stillbirth included () and (). Possible genes affecting only birth interval included (), and (), and those affecting only stillbirth included (), LOC100518697 (a nostrin-like gene), and (). The QTL and the suggestive 1-Mb nonoverlapping SNP windows may lead to genetic markers for marker assisted selection, marker assisted management, or genomic selection applications in commercial pig populations.

Identifying genetic loci controlling neonatal passive transfer of immunity using a hybrid genotyping strategy.

Colostrum intake is critical to a piglet's survival and can be measured by precipitating out the γ-immunoglobulins from serum with ammonium sulfate (immunocrit). Genetic analysis of immunocrits on 5312 piglets indicated that the heritabilities (se) for direct and maternal effects were 0.13 (0.06) and 0.53 (0.08) respectively. To identify QTL for direct genetic effects, piglets with the highest and lowest immunocrits from 470 litters were selected. Six sets of DNA pools were created based on sire of the litter. These 12 DNA pools were applied to Illumina Porcine SNP60 BeadChips. Normalized X and Y values were analyzed. Three different SNP selection methods were used: deviation of the mean from high vs. low pools, the deviation adjusted for variance based on binomial theory and ANOVA. The 25 highest ranking SNPs were selected from each evaluation for further study along with 12 regions selected based on a five-SNP window approach. Selected SNPs were individually genotyped in the 988 piglets included in pools as well as in 524 piglets that had intermediate immunocrits. Association analyses were conducted fitting an animal model using the estimated genetic parameters. Nineteen SNPs were nominally associated (P < 0.01) with immunocrit values, of which nine remained significant (P < 0.05) after Bonferroni correction, located in 16 genomic regions on 13 chromosomes. In conclusion, the pooling strategy reduced the cost to scan the genome by more than 80% and identified genomic regions associated with a piglet's ability to acquire γ-immunoglobulin from colostrum. Each method to rank SNPs from the pooled analyses contributed unique validated markers, suggesting that multiple analyses will reveal more QTL than a single analysis.

Effect of essential fatty acid and zinc supplementation during pregnancy on birth intervals, neonatal piglet brain myelination, stillbirth, and preweaning mortality.

Omega fatty acids and zinc contribute to physiological pathways that could affect the farrowing process, stillbirth, preweaning mortality, and postweaning return to estrus. To determine effects of omega fatty acids and zinc on these reproductive traits, gilts were mated and fed either a control diet, a diet supplemented with 1.09% Gromega, a diet supplemented with 0.07% zinc sulfate, or a diet supplemented with both Gromega and zinc sulfate from d 80 of gestation until farrowing. Farrowings were video recorded to obtain birth intervals for each piglet, and the number of live and stillborn piglets was recorded. On d 1 after farrowing, piglets were weighed, and the smallest piglet in each litter was sacrificed. A blood sample was collected to measure the immunoglobulin immunocrit ratio, and brain, cerebellum, brain stem, full and empty stomach (to calculate stomach content weight), and heart weights were recorded. Because myelination of specific brain regions may affect preweaning mortality, brain stem, cerebellum, and spinal cord tissues were measured for content of myelin basic proteins and myelin lipids. For remaining piglets, survival to weaning and weaning weights were recorded. Results indicated a weak positive correlation (r = 0.23, P < 0.05) between immunocrit values and brain stem high molecular weight myelin basic protein. There was also a Gromega × zinc supplementation interaction (P < 0.05) on brain stem high molecular weight myelin basic protein in which the combined treatment was greater than the control or each supplement alone. Zinc treatment decreased stillbirth rate during prolonged farrowing and subsequent preweaning survival of low birth weight piglets. Gromega increased overall stillbirth rate and increased the stillbirth rate during prolonged farrowing. There were no relationships between myelin measurements and preweaning survival. In conclusion, combined Gromega and zinc supplementation appeared to improve myelination, but zinc alone improved stillbirth and preweaning survival.

DNA polymorphisms and transcript abundance of PRKAG2 and phosphorylated AMP-activated protein kinase in the rumen are associated with gain and feed intake in beef steers.

Beef steers with variation in feed efficiency phenotypes were evaluated previously on a high-density SNP panel. Ten markers from rs110125325-rs41652818 on bovine chromosome 4 were associated with average daily gain (ADG). To identify the gene(s) in this 1.2-Mb region responsible for variation in ADG, genotyping with 157 additional markers was performed. Several markers (n = 41) were nominally associated with ADG, and three of these, including the only marker to withstand Bonferroni correction, were located within the protein kinase, AMP-activated, gamma 2 non-catalytic subunit (PRKAG2) gene. An additional population of cross-bred steers (n = 406) was genotyped for validation. One marker located within the PRKAG2 loci approached a significant association with gain. To evaluate PRKAG2 for differences in transcript abundance, we measured expression in the liver, muscle, rumen and intestine from steers (n = 32) with extreme feed efficiency phenotypes collected over two seasons. No differences in PRKAG2 transcript abundance were detected in small intestine, liver or muscle. Correlation between gene expression level of PRKAG2 in rumen and average daily feed intake (ADFI) was detected in both seasons (P < 0.05); however, the direction differed by season. Lastly, we evaluated AMP-activated protein kinase (AMPK), of which PRKAG2 is a subunit, for differences among ADG and ADFI and found that the phosphorylated form of AMPK was associated with ADFI in the rumen. These data suggest that PRKAG2 and its mature protein, AMPK, are involved in feed efficiency traits in beef steers. This is the first evidence to suggest that rumen AMPK may be contributing to ADFI in cattle.

Effect of creatine supplementation during the last week of gestation on birth intervals, stillbirth, and preweaning mortality in pigs.

We hypothesized that creatine supplementation would reduce birth intervals, stillbirth rate, and preweaning survival in pigs because of its reported improvement of athletic performance in humans. In Exp. 1, gilts (n = 42) and first parity sows (n = 75) were mated at estrus. Beginning on d 110 of gestation, dams received either no treatment or 20 g creatine daily until farrowing. At farrowing in November 2008, pigs were monitored by video camera to determine individual piglet birth intervals. On d 1, piglets were weighed, euthanized, and the cerebellum, brain stem, and spinal cord were collected from the largest and smallest piglets in each litter to measure myelin basic proteins, myelin cholesterol, glucocerebrosides, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelin. Preweaning mortality of the remaining piglets was recorded, including whether a piglet had been overlayed by the dam. A second experiment was performed using gilts (n = 90), farrowing in July 2010, to test differential effects of creatine supplementation during hot, humid weather when dams typically have more difficulty farrowing. Once again, gilts were provided either no supplementation or 20 g creatine daily from d 110 to the day of farrowing. Gilts were video recorded during farrowing, piglets were weighed on d 1, and preweaning mortality (including overlays) was recorded. In Exp. 1, creatine supplementation had no effect on birth intervals or stillbirth rate. Creatine supplementation improved the amount of myelin lipids in brain regions of piglets, particularly the brain stem. Creatine supplementation also reduced overlays of low birth weight piglets from gilts but not second parity sows. Data from Exp. 2 were combined with gilt data from Exp. 1 to examine the effect of creatine, season, and their interaction. There were no effects of treatment or season on birth intervals, stillbirth rates, or overall preweaning mortality. Creatine treatment reduced the incidence of overlays in low birth weight piglets in the combined data set. These results suggest that creatine supplementation improved myelination and may reduce the incidence of low birth weight piglets being crushed by the dam.

Identification of an ionotropic glutamate receptor AMPA1/GRIA1 polymorphism in crossbred beef cows differing in fertility.

A proposed functional polymorphism in the ionotropic glutamate receptor AMPA1 (GRIA1) has been reported to influence antral follicle numbers and fertility in cows. Repeat breeder cows that fail to produce a calf in multiple seasons have been reported to have reduced numbers of small (1 to 3 mm) antral follicles in their ovaries. Therefore, we tested the hypothesis that this GRIA1 polymorphism was affecting antral follicle numbers in repeat breeder cows. Repeat breeder cows (n = 64) and control cows (n = 72) that had always produced a calf were housed in a dry lot and observed twice daily for behavioral estrus. Blood samples were collected, and cows were genotyped for this GRIA1 polymorphism and for a polymorphism in the GnRH receptor (GnRHR) that was proposed to influence age at puberty. On d 3 to 8 after estrus cows were slaughtered, and reproductive organs were collected to determine antral follicle count, ovary size, and uterine horn diameter. Repeat breeder cows were older at first calving than control cows (P = 0.006). The length (P = 0.03) and height (P = 0.02) of the ovary contralateral to the corpus luteum (CL) were greater in control cows than repeat breeder cows. The endometrial diameter in the horn ipsilateral to the CL was greater in the control cows than the repeat breeder cows. Repeat breeder cows had fewer small (1 to 5 mm) antral follicles than control cows (P = 0.003); however, there was no association between GRIA1 genotype and antral follicle number. The GnRHR polymorphism was associated with age at first calving because cows that were homozygous for the C allele had a greater age at first calving than heterozygous cows or cows that were homozygous for the T allele (P = 0.01). In the granulosa cells from small (1 to 5 mm) antral follicles, mRNA abundances of 2 markers of oocyte quality, anti-Müllerian hormone and pentraxin 3, did not differ between fertility groups (P ≥ 0.12). We conclude that this GRIA1 polymorphism exists in beef cows but that it does not influence antral follicle numbers. The association between GnRHR genotype and age at first calving is likely not causal as this polymorphism is not functional. The utility of this polymorphism as a genetic marker for early conception in heifers will require further validation. Screening postpartum cows by ultrasonography to determine antral follicle numbers may aid in making culling decisions.

A simple novel measure of passive transfer of maternal immunoglobulin is predictive of preweaning mortality in piglets.

Two factors that contribute to preweaning mortality in piglets are the initiation of lactation by sows and their ability to nurse their piglets. The objective of this study was to determine if the quantification of the transfer of immunoglobulins (Igs) from sow to piglet could act as a measure of these sow factors in terms of their influence on preweaning mortality. To measure passive transfer, a simple, rapid Ig immunocrit method was developed. For validation, the smallest piglets from 204 gilts were sacrificed on day 1 after birth and blood was collected. Piglet serum Ig concentrations were measured three ways: (1) by protein A sepharose precipitation, SDS-PAGE, and densitometry of the IgG heavy chain; (2) by precipitation of Ig with (NH(4))(2)SO(4) followed by spectrophotometric measurement; and (3) by precipitation of Ig with (NH(4))(2)SO(4) and measurement of the ratio of precipitate to sample volume using a hematocrit microcapillary (the Ig immunocrit method). Results from the (NH(4))(2)SO(4) methods correlated (r=0.86) with those obtained using SDS-PAGE. Day 1 weights and immunocrit ratios and preweaning survival data were then collected from every piglet from first (n=90), and second (n=145) parity sows. Bodyweight and immunocrit ratios accounted for 4.8% and 16.7% (P<0.01) of the variation in preweaning mortality, respectively. Litter average immunocrit ratios were not correlated with preweaning mortality. In conclusion, the Ig immunocrit method is a simple, rapid measure of passive transfer from sow to piglet, and is useful in assessing the initiation of colostrum and the nursing ability of sows, and the effect of these events on preweaning piglet mortality.

Comparison of myelination between large and small pig fetuses during late gestation.

We compared myelination of the cerebellum, brain stem, and spinal cord in the largest and smallest pig fetuses within a litter during late gestation. Gilts were killed on Days 92, 100, and 110 of gestation and these neural tissues were obtained from the largest and smallest fetuses in each litter. Myelin basic protein (MBP) mRNA was quantified in each tissue using real time reverse transcriptase polymerase chain reaction (rtPCR). Myelin was recovered from each tissue and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and thin layer chromatography (TLC) was used to measure MBP and lipids, respectively. MBP mRNA increased with advancing gestation in all three tissues examined (P≤0.05) and was less in brain stem of small piglets compared to large piglets (P<0.01). Two coomassie stained protein bands (HMBP and LMBP) were observed by SDS-PAGE. Six prominent lipid bands were obtained by TLC (cholesterol, hydroxy(h)-cerebroside, nonhydroxy(nh)-cerebroside, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelin). Significant day by fetal size interactions for cerebellar MBP and lipids indicated that cerebellar myelination in the smallest fetuses was less compared to the largest fetuses on Days 100 and 110 of gestation. Myelin MBP and lipid obtained from brain stem increased with advancing gestation and LMBP and lipids were less in small piglets compared to large piglets. In contrast, myelination in spinal cord increased with day of gestation but was not different between smallest and largest fetuses. These results confirm that myelination of the cerebellum and brain stem, but not spinal cord, is reduced in small fetuses during late gestation.

Contributions of the maternal uterine environment and piglet genotype on weaning survivability potential: I. Development of neonatal piglets after reciprocal embryo transfers between Meishan and White crossbred gilts.

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.

MicroRNA expression profile in bovine cumulus-oocyte complexes: possible role of let-7 and miR-106a in the development of bovine oocytes.

The objectives of this study included: (1) identify the expression of miRNAs specific to bovine cumulus-oocyte complexes (COCs) during late oogenesis, (2) characterize the expression of candidate miRNAs as well as some miRNA processing genes, and (3) computationally identify and characterize the expression of target mRNAs for candidate miRNAs. Small RNAs in the 16-27 bp range were isolated from pooled COCs aspirated from 1- to 10-mm follicles of beef cattle ovaries and used to construct a cDNA library. A total 1798 putative miRNA sequences from the cDNA library of small RNA were compared to known miRNAs. Sixty-four miRNA clusters matched previously reported sequences in the miRBase database and 5 miRNA clusters had not been reported. TaqMan miRNA assays were used to confirm the expression of let-7b, let-7i, and miR-106a from independent collections of COCs. Real-time PCR assays were used to characterize expression of miRNA processing genes and target mRNAs (MYC and WEE1A) for the candidate miRNAs from independent collections of COCs. Expression data were analyzed using general linear model procedures for analysis of variance. The expression of let-7b and let-7i were not different between the cellular populations from various sized follicles. However, miR-106a expression was greater (P<0.01) in oocytes compared with COCs and granulosa cells. Furthermore, all the miRNA processing genes have greater expression (P<0.001) in oocytes compared with COCs and granulosa cells. The expression of potential target mRNAs for let-7 and let-7i (i.e., MYC), and miR-106a (i.e., WEE1A) were decreased (P<0.05) in oocytes compared with COCs and granulosa cells. These results demonstrate specific miRNAs within bovine COCs during late oogenesis and provide some evidence that miRNAs may play a role regulating maternal mRNAs in bovine oocytes.

Effect of empty uterine space on birth intervals and fetal and placental development in pigs.

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.

A low-fat liquid diet increases protein accretion and alters cellular signaling for protein synthesis in 10-day-old pigs.

Previous research showed that neonatal pigs respond to decreases in energy density of liquid diets with increased feed intake, resulting in similar performance to pigs fed a more energy-dense diet. The objective of this experiment was to determine whether a high- (25%, HF) or low-fat (2%, LF) liquid diet would affect nutrient accretion rate and select proteins involved in energy homeostasis and protein synthesis in early weaned pigs. Ninety-six pigs, with an initial BW of 3,637 +/- 85 g, were weaned from the sow at 10 d of age and utilized in a randomized complete block design. Pigs were blocked by BW and then assigned to pens (8 pigs/pen). Diets were formulated to provide a constant AA:ME ratio and were fed for 10 d. Pigs were killed at 10, 15, and 20 d of age, at which time blood and LM were collected, and carcasses were prepared for body composition analysis. Blood was analyzed for plasma urea nitrogen (PUN) and NEFA. Longissimus dorsi was analyzed via western immunoblot for mammalian target of rapamycin (mTOR) and adenosine 5' monophosphate-activated protein kinase (AMPK) phosphorylation. Pigs gained 347 +/- 11 g/d, which resulted in an ending BW of 6,858 +/- 135 g, regardless of dietary treatment (P > 0.49). Pigs fed the LF diet consumed 25% more milk than pigs fed the HF diet (2,853 +/- 86 vs. 2,269 +/- 79 g dry feed.pen(-1).d(-1); P < 0.01), which resulted in similar calculated ME intakes between dietary treatments (9.9 +/- 0.2 vs. 10.5 +/- 0.2 Mcal.pen(-1).d(-1); P > 0.5). Feed conversion (G:F) was 24% greater in HF-fed compared with LF-fed pigs (P < 0.01). Circulating NEFA (40 +/- 14 vs. 138 +/- 21 microEq/L; P < 0.01) and PUN (3.0 +/- 0.6 vs. 17.7 +/- 0.8 mM; P < 0.01) concentrations were less in LF pigs compared with HF pigs after 10 d of dietary treatments. Pigs consuming the LF diet had a 21% increase in protein accretion (50.5 +/- 2.8 vs. 61.2 +/- 2.8 g/d; P < 0.04) and a 71% reduced lipid accretion rate (28.8 +/- 2.0 vs. 8.3 +/- 2.3 g/d; P < 0.001). Phosphorylation of AMPK was 29% less (P < 0.03) in LF pigs compared with HF pigs, whereas mTOR phosphorylation was increased by 37% in LF pigs (P < 0.01). We conclude that feeding a LF liquid diet to pigs weaned from the sow at 10 d of age increases feed intake to regulate energy intake while maintaining growth performance. In addition, 10-d-old pigs consuming a liquid LF diet have increased protein deposition by a mechanism mediated through AMPK and mTOR.

Proportion of the litter farrowed, litter size, and progesterone and estradiol effects on piglet birth intervals and stillbirths.

Stillbirth in swine ranges from 2 to 9%, resulting in a significant loss of piglets. Previous studies clearly indicate a relationship between prolonged birth intervals and stillbirth, but factors influencing birth intervals are not fully known. To characterize birth intervals and stillbirth, farrowing was recorded during three farrowing seasons. Blood samples were collected on d 110 and d 113 of gestation, and were assayed for progesterone and estrogen. Relationships between estrumate (cloprostenol sodium, an analogue of prostaglandin F(2alpha)) usage, litter size, proportion of the litter farrowed, progesterone and estrogen concentrations, birth intervals, and stillbirth were analyzed using regression analysis. A clear relationship between birth intervals and stillbirth was observed. Stillbirth rate was unaffected by birth intervals of <1 h, and increased (P < 0.01) for birth intervals >1 h. A significant negative association between litter size and birth intervals was observed (P < 0.01). Birth intervals were unaffected by proportion of the litter farrowed until the last piglet in the litter, whose birth interval increased dramatically (1.5-fold; P < 0.01). Stillbirth rates increased as proportion of the litter farrowed increased, and a dramatic increase in stillbirth occurred for the last piglet in the litter. Neither d 110 nor 113 plasma progesterone concentrations were associated with litter size, birth intervals, or stillbirth rates. Curvilinear relationships were present between d 110 or 113 plasma estradiol concentrations and litter size. However, neither d 110 nor 113 estradiol concentrations were associated with birth intervals or stillbirth rates. These results indicate that (1) birth intervals greater than 1 h are associated with increased stillbirth; (2) larger litter size reduces birth intervals; (3) the last piglet in the litter has both a prolonged birth interval and increased risk of stillbirth; (4) plasma progesterone before farrowing does not influence birth intervals or stillbirth; and (5) plasma estradiol does not influence birth interval or stillbirth, despite a positive relationship between litter size and plasma estradiol. An understanding of the effects of litter size and proportion of the litter farrowed on birth intervals might be exploited to decrease stillbirth in piglets.

Development of the pig placenta.

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.