Online feeding behavior monitoring of individual group-housed grow-finish pigs using a low-frequency RFID electronic feeding system.

Early identification of animals in need of management intervention is critical to maximize animal health and welfare and minimize issues with productivity. Feeding behavior, captured by automated feeding systems, can be used to monitor the health and welfare status of individual pigs. Here, we present a framework for monitoring feeding behavior of grow-finish pigs in real time, using a low-frequency radio frequency identification (RFID) system. Using historical data, an autoregressive linear model for predicting daily time at the feeder was developed and utilized to detect anomalous decreases in feeding behavior associated with health status of the pig. A total of 2,826 pigs were individually monitored with our warning system over the entire grow-finish period, and health warnings were compared to caretaker diagnoses. The system detected 55.7% of the caretaker diagnoses, and on average these events were detected 2.8 d earlier than diagnosis by the caretaker. High numbers of potentially spurious health warnings, generated by the system, can be partly explained by the lack of a reliable and repeatable gold standard reference data set. Results from this work provide a solid basis for monitoring individual animals, but further improvements to the system are necessary for practical implementation.

Impacts of Farrowing Pen Design, Season, and Sow Parity on Litter Performance and Piglet Mortality.

Piglet mortality during lactation is a significant concern in swine production, influenced by complex interactions involving sow, piglet, environmental, and management factors. While crushing by the sow may be the ultimate cause of piglet mortality, there are many factors influencing the outcome, including parity, thermal stress, and animal housing systems. New farrowing systems are continuously being developed; however, it is difficult for producers to make decisions without any scientific basis. This study aimed to assess the impact of different farrowing pen layouts on piglet performance, considering parity and season. A total of 546 sows and 9123 piglets were monitored across 36 lactation cycles. Sows were randomly assigned to three farrowing pen layouts (standard, diagonal, and offset) in three rooms (20 sows by room). All farrowing pens had the same space allocations (2.7 m by 1.8 m and 2.1 m by 0.6 m for the sow area). The three types of farrowing pens were blocked by position within the room. Piglet performance traits (percent of stillborns, percent of mortality, percent of overlays, and average daily weight gain: ADG) and sows traits (health and parity) were monitored following US Meat Animal Research Center (USMARC) procedures. Results indicated that treatment, parity, and season influenced some piglet performance traits. The offset farrowing pen had a lower percent of stillborns compared to the standard. No significant differences were observed between the diagonal crate and the other treatments. When evaluating high mortality sow (>two piglets), the offset and standard treatments had a lower percent of overlays. Piglets from first-parity sows had lower ADG than those from higher-parity sows. A higher percent of overlays were observed in Autumn and Summer compared to Spring and Winter, and Summer had lower average daily weight gain than other seasons. The results suggest that modifying the layout (offset), with sows placed further away from the heating source, can reduce the percent of overlays in sows with high mortality (>2 piglets). In addition, the influence of season on the piglet production traits demonstrated the importance of proper management of the environment, even in systems with a certain level of climatic control.

A compendium of genetic regulatory effects across pig tissues.

The Farm Animal Genotype-Tissue Expression (FarmGTEx) project has been established to develop a public resource of genetic regulatory variants in livestock, which is essential for linking genetic polymorphisms to variation in phenotypes, helping fundamental biological discovery and exploitation in animal breeding and human biomedicine. Here we show results from the pilot phase of PigGTEx by processing 5,457 RNA-sequencing and 1,602 whole-genome sequencing samples passing quality control from pigs. We build a pig genotype imputation panel and associate millions of genetic variants with five types of transcriptomic phenotypes in 34 tissues. We evaluate tissue specificity of regulatory effects and elucidate molecular mechanisms of their action using multi-omics data. Leveraging this resource, we decipher regulatory mechanisms underlying 207 pig complex phenotypes and demonstrate the similarity of pigs to humans in gene expression and the genetic regulation behind complex phenotypes, supporting the importance of pigs as a human biomedical model.

Statistical and machine learning approaches to describe factors affecting preweaning mortality of piglets.

High preweaning mortality (PWM) rates for piglets are a significant concern for the worldwide pork industries, causing economic loss and well-being issues. This study focused on identifying the factors affecting PWM, overlays, and predicting PWM using historical production data with statistical and machine learning models. Data were collected from 1,982 litters from the U.S. Meat Animal Research Center, Nebraska, over the years 2016 to 2021. Sows were housed in a farrowing building with three rooms, each with 20 farrowing crates, and taken care of by well-trained animal caretakers. A generalized linear model was used to analyze the various sow, litter, environment, and piglet parameters on PWM. Then, different models (beta-regression and machine learning model: a random forest [RF]) were evaluated. Finally, the RF model was used to predict PWM and overlays for all listed contributing factors. On average, the mean birth weight was 1.44 kg, and the mean mortality was 16.1% where 5.55% was for stillbirths and 6.20% was contributed by overlays. No significant effect was found for seasonal and location variations on PWM. Significant differences were observed in the effects of litter lines on PWM (P < 0.05). Landrace-sired litters had a PWM of 16.26% (±0.13), whereas Yorkshire-sired litters had 15.91% (±0.13). PWM increased with higher parity orders (P < 0.05) due to larger litter sizes. The RF model provided the best fit for PWM prediction with a root mean squared errors of 2.28 and a correlation coefficient (r) of 0.89 between observed and predicted values. Features' importance from the RF model indicated that, PWM increased with the increase of litter size (mean decrease accuracy (MDA) = 93.17), decrease in mean birth weight (MDA = 22.72), increase in health diagnosis (MDA = 15.34), longer gestation length (MDA = 11.77), and at older parity (MDA = 10.86). However, in this study, the location of the farrowing crate, seasonal differences, and litter line turned out to be the least important predictors for PWM. For overlays, parity order was the highest importance predictor (MDA = 7.68) followed by litter size and mean birth weight. Considering the challenges to reducing the PWM in the larger litters produced in modern swine industry and the limited studies exploring multiple major contributing factors, this study provides valuable insights for breeding and production management, as well as further investigations on postural transitions and behavior analysis of sows during the lactation period.

Identifying Early-Life Behavior to Predict Mothering Ability in Swine Utilizing NUtrack System.

Early indicator traits for swine reproduction and longevity support economical selection decision-making. Activity is a key variable impacting a sow's herd life and productivity. Early-life activities could contribute to farrowing traits including gestation length (GL), number born alive (NBA), and number weaned (NW). Beginning at 20 weeks of age, 480 gilts were video recorded for 7 consecutive days and processed using the NUtrack system. Activity traits included angle rotated (radians), average speed (m/s), distance traveled (m), time spent eating (s), lying lateral (s), lying sternal (s), standing (s), and sitting (s). Final daily activity values were averaged across the period under cameras. Parity one data were collected for all gilts considered. Data were analyzed using linear regression models (R version 4.0.2). GL was significantly impacted by angle rotated (p = 0.03), average speed (p = 0.07), distance traveled (p = 0.05), time spent lying lateral (p = 0.003), and lying sternal (0.02). NBA was significantly impacted by time spent lying lateral (p = 0.01), lying sternal (p = 0.07), and time spent sitting (p = 0.08). NW was significantly impacted by time spent eating (p = 0.09), time spent lying lateral (p = 0.04), and time spent sitting (p = 0.007). This analysis suggests early-life gilt activities are associated with sow productivity traits of importance. Further examination of the link between behaviors compiled utilizing NUtrack and reproductive traits is necessitated to further isolate behavioral differences for potential use in selection decisions.

Relationships of genomic estimated breeding values for age at puberty, birth weight, and growth during development in normal cyclic and acyclic gilts.

Managing replacement gilts to reach optimal body weight and growth rate for boar stimulation and first breeding is a key component for sow reproductive longevity and producer profitability. Failure to display pubertal estrus remains a major reason that gilts are culled from the herd. Puberty is metabolically gated so evaluating phenotypic and genetic relationships between birth weight and growth traits with age at puberty and acyclicity can provide valuable insight for efficient gilt development. Data on a litter of origin of the gilt, average daily gain at different stages of development, and age at puberty were available for age-matched cyclic (n = 4,861) and acyclic gilts (prepubertal anestrus, n = 578; behavioral anestrus, n = 428). Genomic estimated breeding values were predicted for each trait using genomic best linear unbiased prediction. Primiparous sows produced more acyclic gilts than multiparous sows (P < 0.05). Accounting for effects of parity and litter size, prepubertal anestrus gilts were heavier at birth and behaviorally anestrus gilts grew faster during the finisher period compared to cyclic gilts (P < 0.05), reflecting possible prenatal programming that negatively affects optimal pubertal development and antagonistic effects between adolescent growth and expression of estrus of gilts from first parity sows. Regression of phenotypic age at puberty with lifetime growth rate (birth to selection) showed a negative linear relationship whereas genomic estimated breeding values showed a negative quadratic relationship indicating that gilts with the least and greatest growth are less optimal as replacements. The slopes of these relationships are small with low negative phenotypic (r = -0.06) and genetic correlations (r = -0.13). The addition of data from acyclic gilts did not substantially change the estimates for genetic relationships between growth and pubertal onset. Although this study identified differences in birth weight and growth rate between cyclic and acyclic gilts the genetic relationships are weak, suggesting that genetic selection for these traits can be achieved separately. Avoiding the smallest and largest gilts in a cohort born to first parity sows could result in gilts with optimal development and reduce the proportion of replacement gilts that are acyclic.

Failure to display pubertal estrus is major reason replacement gilts are culled from the herd. Two types of prebreeding estrus failure are delay in attaining puberty due to sexual immaturity known as prepubertal anestrus (PPA) and silent ovulation without signs of estrus known as behavioral anestrus (BA). For efficient gilt development, it is important to understand what contributes to these acyclic phenotypes. Comparison of birth weight and growth rate in age-matched cyclic, PPA, and BA gilts showed that PPA gilts were heavier at birth and BA gilts grew faster during the finisher period, reflecting negative effects of larger birth weight and faster growth on sexual maturity and behavioral estrus. The genetic relationship between growth and puberty onset indicated that gilts with the least and greatest growth rates are less optimal as replacements. A selection criterion to avoid the smallest and largest gilts in a cohort could result in gilts with optimal development for boar stimulation and reduce the proportion of acyclic gilts. This management strategy would be most effective if targeted to first parity sows.

gBLUP-GWAS identifies candidate genes, signaling pathways, and putative functional polymorphisms for age at puberty in gilts.

Successful development of replacement gilts determines their reproductive longevity and lifetime productivity. Selection for reproductive longevity is challenging due to low heritability and expression late in life. In pigs, age at puberty is the earliest known indicator for reproductive longevity and gilts that reach puberty earlier have a greater probability of producing more lifetime litters. Failure of gilts to reach puberty and display a pubertal estrus is a major reason for early removal of replacement gilts. To identify genomic sources of variation in age at puberty for improving genetic selection for early age at puberty and related traits, gilts (n = 4,986) from a multigeneration population representing commercially available maternal genetic lines were used for a genomic best linear unbiased prediction-based genome-wide association. Twenty-one genome-wide significant single nucleotide polymorphisms (SNP) located on Sus scrofa chromosomes (SSC) 1, 2, 9, and 14 were identified with additive effects ranging from -1.61 to 1.92 d (P < 0.0001 to 0.0671). Novel candidate genes and signaling pathways were identified for age at puberty. The locus on SSC9 (83.7 to 86.7 Mb) was characterized by long range linkage disequilibrium and harbors the AHR transcription factor gene. A second candidate gene on SSC2 (82.7 Mb), ANKRA2, is a corepressor for AHR, suggesting a possible involvement of AHR signaling in regulating pubertal onset in pigs. Putative functional SNP associated with age at puberty in the AHR and ANKRA2 genes were identified. Combined analysis of these SNP showed that an increase in the number of favorable alleles reduced pubertal age by 5.84 ± 1.65 d (P < 0.001). Candidate genes for age at puberty showed pleiotropic effects with other fertility functions such as gonadotropin secretion (FOXD1), follicular development (BMP4), pregnancy (LIF), and litter size (MEF2C). Several candidate genes and signaling pathways identified in this study play a physiological role in the hypothalamic-pituitary-gonadal axis and mechanisms permitting puberty onset. Variants located in or near these genes require further characterization to identify their impact on pubertal onset in gilts. Because age at puberty is an indicator of future reproductive success, these SNP are expected to improve genomic predictions for component traits of sow fertility and lifetime productivity expressed later in life.

Selecting for replacement gilts is challenging because sow reproductive traits are lowly heritable and expressed late in life. Age at puberty is the earliest indicator of future reproductive success of gilts. Genetic selection for early onset of puberty could be feasible with the availability of molecular genetic predictors for age at puberty. To identify genomic sources associated with variation in age at puberty in gilts, a large-scale genome-wide association study was conducted at the U.S Meat Animal Research Center, Clay Center, Nebraska. Novel genomic associations for age at puberty were identified. Several candidate genes identified for age at puberty are involved in signaling pathways that regulate ovarian functions and pubertal onset. Potential causative genetic variants for age at puberty were identified within the candidate genes. These novel SNP are important new markers for use in genomic selection of replacement gilts with early puberty and provide critical new insight into biological mechanisms important for pubertal development in gilts.

Determining the Presence and Size of Shoulder Lesions in Sows Using Computer Vision.

Shoulder sores predominantly arise in breeding sows and often result in untimely culling. Reported prevalence rates vary significantly, spanning between 5% and 50% depending upon the type of crate flooring inside a farm, the animal's body condition, or an existing injury that causes lameness. These lesions represent not only a welfare concern but also have an economic impact due to the labor needed for treatment and medication. The objective of this study was to evaluate the use of computer vision techniques in detecting and determining the size of shoulder lesions. A Microsoft Kinect V2 camera captured the top-down depth and RGB images of sows in farrowing crates. The RGB images were collected at a resolution of 1920 × 1080. To ensure the best view of the lesions, images were selected with sows lying on their right and left sides with all legs extended. A total of 824 RGB images from 70 sows with lesions at various stages of development were identified and annotated. Three deep learning-based object detection models, YOLOv5, YOLOv8, and Faster-RCNN, pre-trained with the COCO and ImageNet datasets, were implemented to localize the lesion area. YOLOv5 was the best predictor as it was able to detect lesions with an mAP@0.5 of 0.92. To estimate the lesion area, lesion pixel segmentation was carried out on the localized region using traditional image processing techniques like Otsu's binarization and adaptive thresholding alongside DL-based segmentation models based on U-Net architecture. In conclusion, this study demonstrates the potential of computer vision techniques in effectively detecting and assessing the size of shoulder lesions in breeding sows, providing a promising avenue for improving sow welfare and reducing economic losses.

Dam parity structure and body condition during lactation influence piglet growth and gilt sexual maturation through pre-finishing.

Energy demands during lactation greatly influence sow body condition and piglet performance. We hypothesized that primiparous sows or sows with reduced body condition would produce piglets with reduced growth and delayed sexual maturation. Eight weekly farrowing seasons were used to evaluate sow body condition (post-farrowing, PF and weaning, WN) and piglet growth from 157 dams. Body condition was measured at PF and WN using sow calipers (last rib and hip) and 10th rib ultrasound. Sows were categorized as thin, moderate, or fat by caliper (PF or WN). Individual pig weights were recorded on approximately 1, 10, WN, 45, 100, and 145 d of age. At 100 and 145 d of age, 10th-rib backfat and loin eye area were measured on 567 pigs and first estrus was monitored in 176 gilts reserved for breeding selection beginning at approximately 170 d of age. Sows had similar (P > 0.10) PF last rib caliper measurements but at WN, first parity sows had the smallest caliper measurements compared to other parities (P < 0.05). Parities 1, 2, and 3 sows had similar (P > 0.10) loin eye area at PF; however, at WN first parity sows had the smallest loin eye area (P < 0.05; 38.2 ± 0.63 cm2). Parity 1 sows had the greatest (P < 0.05) reduction of backfat and loin eye area over the lactation period (-2.9 ± 0.31 mm and -2.6 ± 0.49 cm2, respectively). At 1 d of age and WN, piglets from first parity sows weighed the least (P < 0.05) but were the heaviest (P < 0.05) at 100 and 145 d of age. Pigs from first parity litters had larger (P < 0.05) loin eye area at 100 and 145 d of age and greater backfat (P < 0.05) at 145 d of age. Fat sows at WN (last rib or hip) had the lightest (P < 0.05) piglets at 10 d of age and WN. However, at 45 d of age, piglets from fat sows (last rib or hip) were heavier (P < 0.05) than piglets from moderate and thin sows. Tenth rib backfat at 100 and 145 d of age tended (P < 0.10) to be less in pigs reared by thin sows (PF and WN hip). Tenth rib loin eye area was similar among pigs reared by fat, moderate, or thin sows. Gilts developed in litters from fourth parity sows had (P < 0.05) delayed age at puberty in contrast to gilts from first or third parity sows (200.9 ± 4.96 d vs. 189.0 ± 2.29 d and 187.5 ± 2.84 d, respectively). Although progeny body weights were typically less from first parity dams through 45 d of age, these progeny were similar or heavier at 100 and 145 d of age in contrast to progeny from other parities. Furthermore, gilt progeny from first parity dams did not have delayed pubertal attainment.

Young female swine have a greater challenge successfully producing and raising a litter of piglets as they are still maturing themselves and nursing is an extremely energy demanding event. Piglet growth during the nursing phase can have extended impact on growth and development later in life. Piglets raised by young first-time mothers were smaller at birth and weaning but grew to similar weight and body composition later in life as their contemporaries raised by older more mature mothers. Young female pigs raised by first-time mothers had similar or better sexual maturity than counterparts raised by mature mothers. These findings indicate that piglets reared by first time mothering dams will not have detrimental effects on maturity and reproductive parameters. Producers can confidently select females that were reared by first-time mothers for the breeding herd without sacrificing quality.

Potential functional variants in AHR signaling pathways are associated with age at puberty in swine.

Puberty in female pigs is defined as age at first estrus and gilts that have an earlier age at puberty are more likely to have greater lifetime productivity. Because age at puberty is predictive for sow longevity and lifetime productivity, but not routinely measured in commercial herds, it would be beneficial to use genomic or marker-assisted selection to improve these traits. A GWAS at the US Meat Animal Research Center (USMARC) identified several loci associated with age at puberty in pigs. Candidate genes in these regions were scanned for potential functional variants using sequence information from the USMARC swine population founder animals and public databases. In total, 135 variants (SNP and insertion/deletions) in 39 genes were genotyped in 1284 phenotyped animals from a validation population sired by Landrace and Yorkshire industry semen using the Agena MassArray system. Twelve variants in eight genes were associated with age at puberty (P < 0.005) with estimated additive SNP effects ranging from 1.6 to 5.3 days. Nine of these variants were non-synonymous coding changes in AHR, CYP1A2, OR2M4, SDCCAG8, TBC1D1 and ZNF608, two variants were deletions of one and four codons in aryl hydrocarbon receptor, AHR, and the most significant SNP was near an acceptor splice site in the acetyl-CoA carboxylase alpha, ACACA. Several of the loci identified have a physiological and a genetic role in sexual maturation in humans and other animals and are involved in AHR-mediated pathways. Further functional validation of these variants could identify causative mutations that influence age at puberty in gilts and possibly sow lifetime productivity.

Feeding behavior of grow-finish swine and the impacts of heat stress.

Heat stress has negative impacts on pork production, particularly in the grow-finish phase. During heat stress events, the feeding behavior of pigs is altered to reduce heat production. Several different systems have been developed to study feeding behavior. Most systems are not accurate representations of grow-finish commercial production as feed intake is monitored for only one pig at a time. The objective of this study was to utilize a feed monitoring system, representative of commercial conditions, to determine feeding behavior patterns of grow-finish pigs throughout the year and to identify changes that occurred during heat stress events. Feeder visit data were collected on barrows and gilts (n = 932) from three different sire breeds, Landrace, Yorkshire, and Duroc, between May 2014 and April 2016. Days in the study were partitioned into groups based on their maximum temperature-humidity index (THI), where a THI less than 23.33 °C was classified as "Normal", a THI between 23.33 and 26.11 °C was classified as "Alert", a THI between 26.11 and 28.88 °C was classified as "Danger", and a THI greater than 28.88 °C was classified as "Emergency". Feeding behavioral differences among breeds and sex were observed across all THI categories. Landrace-sired pigs had fewer feeder visits compared to Duroc- and Yorkshire-sired pigs. Gilts had fewer feeder visits than barrows in all THI categories. Differences in feeding behavior patterns between THI categories demonstrated that heat stress reduced the feeding duration of Landrace-sired pigs without any dramatic effects on the other pigs in the study. During elevated temperatures, all pigs tended to increase feeding events during the early (03:00-05:59) and late (18:00-20:59) periods of the day. Utilizing a feed monitoring system that is a more accurate representation of commercial conditions will lead to a greater understanding of feeding behavior among breed types and sexes during heat stress, allowing producers to enhance their ability to properly care for their pigs during both normal and heat stress events.

An improved pig reference genome sequence to enable pig genetics and genomics research.

BACKGROUND: The domestic pig (Sus scrofa) is important both as a food source and as a biomedical model given its similarity in size, anatomy, physiology, metabolism, pathology, and pharmacology to humans. The draft reference genome (Sscrofa10.2) of a purebred Duroc female pig established using older clone-based sequencing methods was incomplete, and unresolved redundancies, short-range order and orientation errors, and associated misassembled genes limited its utility. RESULTS: We present 2 annotated highly contiguous chromosome-level genome assemblies created with more recent long-read technologies and a whole-genome shotgun strategy, 1 for the same Duroc female (Sscrofa11.1) and 1 for an outbred, composite-breed male (USMARCv1.0). Both assemblies are of substantially higher (>90-fold) continuity and accuracy than Sscrofa10.2. CONCLUSIONS: These highly contiguous assemblies plus annotation of a further 11 short-read assemblies provide an unprecedented view of the genetic make-up of this important agricultural and biomedical model species. We propose that the improved Duroc assembly (Sscrofa11.1) become the reference genome for genomic research in pigs.

Effects of Farrowing Stall Layout and Number of Heat Lamps on Sow and Piglet Production Performance.

Most farrowing facilities in the United States use stalls and heat lamps to improve sow and piglet productivity. This study investigated these factors by comparing production outcomes for three different farrowing stall layouts (traditional, expanded creep area, expanded sow area) and use of one or two heat lamps. Data were collected on 427 sows and their litters over one year. Results showed no statistical differences due to experimental treatment for any of the production metrics recorded, excluding percent stillborn. Parity one sows had fewer piglets born alive (p < 0.001), lower percent mortality (p = 0.001) and over-lay (p = 0.003), and a greater number of piglets weaned (p < 0.001) with lower average daily weight gain (ADG) (p < 0.001) and more uniform litters (p = 0.001) as compared to higher parity sows. Farrowing turn, associated with group/seasonal changes, had a significant impact on most of the production metrics measured. Number of piglets born influenced the percent stillborn (p < 0.001). Adjusted litter size had a significant impact on percent mortality (p < 0.001), percent over-lay (p < 0.001), and number of piglets weaned (p < 0.001). As the number of piglets weaned per litter increased, both piglet ADG and litter uniformity decreased (p < 0.001). This information can be used to guide producers in farrowing facility design.

A Survey of Copy Number Variation in the Porcine Genome Detected From Whole-Genome Sequence.

Copy number variations (CNVs) are gains and losses of large regions of genomic sequence between individuals of a species. Although CNVs have been associated with various phenotypic traits in humans and other species, the extent to which CNVs impact phenotypic variation remains unclear. In swine, as well as many other species, relatively little is understood about the frequency of CNV in the genome, sizes, locations, and other chromosomal properties. In this work, we identified and characterized CNV by utilizing whole-genome sequence from 240 members of an intensely phenotyped experimental swine herd at the U.S. Meat Animal Research Center (USMARC). These animals included all 24 of the purebred founding boars (12 Duroc and 12 Landrace), 48 of the founding Yorkshire-Landrace composite sows, 109 composite animals from generations 4 through 9, 29 composite animals from generation 15, and 30 purebred industry boars (15 Landrace and 15 Yorkshire) used as sires in generations 10 through 15. Using a combination of split reads, paired-end mapping, and read depth approaches, we identified a total of 3,538 copy number variable regions (CNVRs), including 1,820 novel CNVRs not reported in previous studies. The CNVRs covered 0.94% of the porcine genome and overlapped 1,401 genes. Gene ontology analysis identified that CNV-overlapped genes were enriched for functions related to organism development. Additionally, CNVRs overlapped with many known quantitative trait loci (QTL). In particular, analysis of QTL previously identified in the USMARC herd showed that CNVRs were most overlapped with reproductive traits, such as age of puberty and ovulation rate, and CNVRs were significantly enriched for reproductive QTL.

Evaluation of genotype quality parameters for SowPro90, a new genotyping array for swine1.

Understanding early predictors of sow fertility has the potential to improve genomic predictions. A custom SNP array (SowPro90 produced by Affymetrix) was developed to include genetic variants overlapping quantitative trait loci for age at puberty, one of the earliest indicators of sow fertility, as well as variants related to innate and adaptive immunity. The polymorphisms included in the custom genotyping array were identified using multiple genomic approaches including deep genomic and transcriptomic sequencing and genome-wide associations. Animals from research and commercial populations (n = 2,586) were genotyped for 103,476 SNPs included in SowPro90. To assess the quality of data generated, genotype concordance was evaluated between the SowPro90 and Porcine SNP60 BeadArray using a subset of common SNP (n = 44,708) and animals (n = 277). The mean genotype concordance rate per SNP was 98.4%. Differences in distribution of data quality were observed between the platforms indicating the need for platform specific thresholds for quality parameters. The optimal thresholds for SowPro90 (≥97% SNP and ≥93% sample call rate) were obtained by analyzing the data quality distribution and genotype concordance per SNP across platforms. At ≥97% SNP call rate, there were 42,151 SNPs (94.3%) retained with a mean genotype concordance of 98.6% across platforms. Similarly, ≥94% SNPs and ≥85% sample call rates were established as thresholds for Porcine SNP60 BeadArray. At ≥94% SNPs call rate, there were 41,043 SNPs (91.8%) retained with a mean genotype concordance of 98.6% across platforms. Final evaluation of SowPro90 array content (n = 103,476) at ≥97% SNPs and ≥93% sample call rates allowed retention of 89,040 SNPs (86%) for downstream analysis. The findings and strategy for quality control could be helpful in identifying consistent, high-quality genotypes for genomic evaluations, especially when integrating genotype data from different platforms.

Using SNP Weights Derived From Gene Expression Modules to Improve GWAS Power for Feed Efficiency in Pigs.

The "large p small n" problem has posed a significant challenge in the analysis and interpretation of genome-wide association studies (GWAS). The use of prior information to rank genomic regions and perform SNP selection could increase the power of GWAS. In this study, we propose the use of gene expression data from RNA-Seq of multiple tissues as prior information to assign weights to SNP, select SNP based on a weight threshold, and utilize weighted hypothesis testing to conduct a GWAS. RNA-Seq libraries from hypothalamus, duodenum, ileum, and jejunum tissue of 30 pigs with divergent feed efficiency phenotypes were sequenced, and a three-way gene x individual x tissue clustering analysis was performed, using constrained tensor decomposition, to obtain a total of 10 gene expression modules. Loading values from each gene module were used to assign weights to 49,691 commercial SNP markers, and SNP were selected using a weight threshold, resulting in 10 SNP sets ranging in size from 101 to 955 markers. Weighted GWAS for feed intake in 4,200 pigs was performed separately for each of the 10 SNP sets. A total of 36 unique significant SNP associations were identified across the ten gene modules (SNP sets). For comparison, a standard unweighted GWAS using all 49,691 SNP was performed, and only 2 SNP were significant. None of the SNP from the unweighted analysis resided in known QTL related to swine feed efficiency (feed intake, average daily gain, and feed conversion ratio) compared to 29 (80.6%) in the weighted analyses, with 9 SNP residing in feed intake QTL. These results suggest that the heritability of feed intake is driven by many SNP that individually do not attain genome-wide significance in GWAS. Hence, the proposed procedure for prioritizing SNP based on gene expression data across multiple tissues provides a promising approach for improving the power of GWAS.

Genome-wide association of changes in swine feeding behaviour due to heat stress.

BACKGROUND: Heat stress has a negative impact on pork production, particularly during the grow-finish phase. As temperature increases, feeding behaviour changes in order for pigs to decrease heat production. The objective of this study was to identify genetic markers associated with changes in feeding behaviour due to heat stress. Feeding data were collected on 1154 grow-finish pigs using an electronic feeding system from July 2011 to March 2016. In this study, days were classified based on the maximum temperature humidity index (THI) during the day as "Normal" (< 23.33 °C), "Alert" (23.33 °C ≤ × < 26.11 °C), "Danger" (26.11 °C ≤ × < 28.88 °C), and "Emergency" (≥ 28.88 °C). Six hundred and eighty-one pigs that experienced more than one THI category were genotyped using a variety of SNP platforms, with final genotypes imputed to approximately 60,000 markers. RESULTS: A genome-wide association study (GWAS) for change in feeding behaviour between each pair of THI categories (six pairs) was conducted. Estimates of heritability for differences in feeding activity between each of the THI categories were low (0.02 ± 0.03) to moderate (0.21 ± 0.04). Sixty-six associations which explained more than 1% of the genomic variation for a trait were detected across the six GWAS, with the smallest number of associations detected in comparisons with Emergency THI. Gene ontology enrichment analysis showed that biological processes related to immune response and function were over-represented among the genes located in these regions. CONCLUSIONS: Genetic differences exist for changes in feeding behaviour induced by elevated ambient temperatures in grow-finish pigs. Selection for heat-tolerant grow-finish pigs should improve production efficiency during warm months in commercial production. Genetic variation in heat shock, stress response and immune function genes may be responsible for the observed differences in performance during heat stress events.

Polymorphism in the intron 20 of porcine O-linked N-acetylglucosamine transferase.

OBJECTIVE: O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) catalyzes the addition of O-GlcNAc and GlcNAcylation has extensive crosstalk with phosphorylation to regulate signaling and transcription. Pig OGT is located near the region of chromosome X that affects follicle stimulating hormone level and testes size. The objective of this study was to find the variations of OGT between European and Chinese pigs. METHODS: Pigs were tested initially for polymorphism in OGT among European and Chinese pigs by polymerase chain reaction and sequencing at the U.S. Meat Animal Research Center (USMARC). The polymorphism was also determined in an independent population of pigs including European and Chinese Meishan (ME) breeds at the National Institute of Animal Science (NIAS, RDA, Korea). RESULTS: The intron 20 of OGT from European and Chinese pigs was 514 and 233 bp, respectively, in the pigs tested initially. They included 1 White composite (WC) boar and 7 sows (2 Minzu×WC, 2 Duroc [DU]×WC, 2 ME×WC, 1 Fengzing×WC) at USMARC. The 281-bp difference was due to an inserted 276-bp element and GACTT in European pigs. When additional WC and ME boars, the grandparents that were used to generate the 1/2ME×1/2WC parents, and the 84 boars of 16 litters from mating of 1/2ME×1/2WC parents were analyzed, the breeds of origin of X chromosome quantitative trait locus (QTL) were confirmed. The polymorphism was determined in an independent population of pigs including DU, Landrace, Yorkshire, and ME breeds at NIAS. OGT was placed at position 67 cM on the chromosome X of the USMARC swine linkage map. CONCLUSION: There was complete concordance with the insertion in European pigs at USMARC and NIAS. This polymorphism could be a useful marker to identify the breed of origin of X chromosome QTL in pigs produced by crossbreeding Chinese and European pigs.

Genomics and metabolomics of post-weaning return to estrus.

The weaning-to-estrus interval is a multifaceted trait that has the potential to substantially improve production efficiency in today's global swine industry, if variation in this measure can be reduced. Systems-biology approaches should help close the knowledge gap and increase selection tools and management strategies-such as gilt development programs, farrowing, and lactation feeding programs-to decrease the weaning-to-estrus interval. Metabolomics, the study of small compounds within biofluids and tissues, provides links between genotype and phenotype. Given the complexity and influence of the environment on the weaning-to-estrus interval, incorporating metabolomics data will provide valuable insight and guidance for future physiological as well as genetic and genomic strategies to reduce this interval, thereby improving sow productivity.

Relationship of neuropeptide FF receptors with pubertal maturation of gilts.

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.