Genomic regions, candidate genes, and pleiotropic variants associated with physiological and anatomical indicators of heat stress response in lactating sows.

BACKGROUND: Heat stress (HS) poses significant threats to the sustainability of livestock production. Genetically improving heat tolerance could enhance animal welfare and minimize production losses during HS events. Measuring phenotypic indicators of HS response and understanding their genetic background are crucial steps to optimize breeding schemes for improved climatic resilience. The identification of genomic regions and candidate genes influencing the traits of interest, including variants with pleiotropic effects, enables the refinement of genotyping panels used to perform genomic prediction of breeding values and contributes to unraveling the biological mechanisms influencing heat stress response. Therefore, the main objectives of this study were to identify genomic regions, candidate genes, and potential pleiotropic variants significantly associated with indicators of HS response in lactating sows using imputed whole-genome sequence (WGS) data. Phenotypic records for 18 traits and genomic information from 1,645 lactating sows were available for the study. The genotypes from the PorcineSNP50K panel containing 50,703 single nucleotide polymorphisms (SNPs) were imputed to WGS and after quality control, 1,622 animals and 7,065,922 SNPs were included in the analyses. RESULTS: A total of 1,388 unique SNPs located on sixteen chromosomes were found to be associated with 11 traits. Twenty gene ontology terms and 11 biological pathways were shown to be associated with variability in ear skin temperature, shoulder skin temperature, rump skin temperature, tail skin temperature, respiration rate, panting score, vaginal temperature automatically measured every 10 min, vaginal temperature measured at 0800 h, hair density score, body condition score, and ear area. Seven, five, six, two, seven, 15, and 14 genes with potential pleiotropic effects were identified for indicators of skin temperature, vaginal temperature, animal temperature, respiration rate, thermoregulatory traits, anatomical traits, and all traits, respectively. CONCLUSIONS: Physiological and anatomical indicators of HS response in lactating sows are heritable but highly polygenic. The candidate genes found are associated with important gene ontology terms and biological pathways related to heat shock protein activities, immune response, and cellular oxidative stress. Many of the candidate genes with pleiotropic effects are involved in catalytic activities to reduce cell damage from oxidative stress and cellular mechanisms related to immune response.

Genomic predictions and GWAS for heat tolerance in pigs based on reaction norm models with performance records and data from public weather stations considering alternative temperature thresholds.

Genetic improvement of livestock productivity has resulted in greater production of metabolic heat and potentially greater susceptibility to heat stress. Various studies have demonstrated that there is genetic variability for heat tolerance and genetic selection for more heat tolerant individuals is possible. The rate of genetic progress tends to be greater when genomic information is incorporated into the analyses as more accurate breeding values can be obtained for young individuals. Therefore, this study aimed (1) to evaluate the predictive ability of genomic breeding values for heat tolerance based on routinely recorded traits, and (2) to investigate the genetic background of heat tolerance based on single-step genome-wide association studies for economically important traits related to body composition, growth and reproduction in Large White pigs. Pedigree information was available for 265,943 animals and genotypes for 8686 animals. The studied traits included ultrasound backfat thickness (BFT), ultrasound muscle depth (MDP), piglet weaning weight (WW), off-test weight (OTW), interval between farrowing (IBF), total number of piglets born (TNB), number of piglets born alive (NBA), number of piglets born dead (NBD), number of piglets weaned (WN) and weaning-to-estrus interval (IWE). The number of phenotypic records ranged from 6059 (WN) to 172,984 (TNB). Single-step genomic reaction norm predictions were used to calculate the genomic estimated breeding values for each individual. Predictions of breeding values for the validation population individuals were compared between datasets containing phenotypic records measured in the whole range of temperatures (WR) and datasets containing only phenotypic records measured when the weather station temperature was above 10°C (10C) or 15°C (15C), to evaluate the usefulness of these datasets that may better reflect the within-barn temperature. The use of homogeneous or heterogeneous residual variance was found to be trait-dependent, where homogeneous variance presented the best fit for MDP, BFT, OTW, TNB, NBA, WN and IBF, while the other traits (WW and IWE) had better fit with heterogeneous variance. The average prediction accuracy, dispersion and bias values considering all traits for WR were 0.36 ± 0.05, -0.07 ± 0.13 and 0.76 ± 0.10, respectively; for 10C were 0.39 ± 0.02, -0.05 ± 0.07 and 0.81 ± 0.05, respectively; and for 15C were 0.32 ± 0.05, -0.05 ± 0.11 and 0.84 ± 0.10, respectively. Based on the studied traits, using phenotypic records collected when the outside temperature (from public weather stations) was above 10°C provided better predictions for most of the traits. Forty-three and 62 candidate genomic regions were associated with the intercept (overall performance level) and slope term (specific biological mechanisms related to environmental sensitivity), respectively. Our results contribute to improve genomic predictions using existing datasets and better understand the genetic background of heat tolerance in pigs. Furthermore, the genomic regions and candidate genes identified will contribute to future genomic studies and breeding applications.

Investigating the impact of non-additive genetic effects in the estimation of variance components and genomic predictions for heat tolerance and performance traits in crossbred and purebred pig populations.

BACKGROUND: Non-additive genetic effects are often ignored in livestock genetic evaluations. However, fitting them in the models could improve the accuracy of genomic breeding values. Furthermore, non-additive genetic effects contribute to heterosis, which could be optimized through mating designs. Traits related to fitness and adaptation, such as heat tolerance, tend to be more influenced by non-additive genetic effects. In this context, the primary objectives of this study were to estimate variance components and assess the predictive performance of genomic prediction of breeding values based on alternative models and two independent datasets, including performance records from a purebred pig population and heat tolerance indicators recorded in crossbred lactating sows. RESULTS: Including non-additive genetic effects when modelling performance traits in purebred pigs had no effect on the residual variance estimates for most of the traits, but lower additive genetic variances were observed, especially when additive-by-additive epistasis was included in the models. Furthermore, including non-additive genetic effects did not improve the prediction accuracy of genomic breeding values, but there was animal re-ranking across the models. For the heat tolerance indicators recorded in a crossbred population, most traits had small non-additive genetic variance with large standard error estimates. Nevertheless, panting score and hair density presented substantial additive-by-additive epistatic variance. Panting score had an epistatic variance estimate of 0.1379, which accounted for 82.22% of the total genetic variance. For hair density, the epistatic variance estimates ranged from 0.1745 to 0.1845, which represent 64.95-69.59% of the total genetic variance. CONCLUSIONS: Including non-additive genetic effects in the models did not improve the accuracy of genomic breeding values for performance traits in purebred pigs, but there was substantial re-ranking of selection candidates depending on the model fitted. Except for panting score and hair density, low non-additive genetic variance estimates were observed for heat tolerance indicators in crossbred pigs.

Longitudinal genomic analyses of automatically-recorded vaginal temperature in lactating sows under heat stress conditions based on random regression models.

BACKGROUND: Automatic and continuous recording of vaginal temperature (TV) using wearable sensors causes minimal disruptions to animal behavior and can generate data that enable the evaluation of temporal body temperature variation under heat stress (HS) conditions. However, the genetic basis of TV in lactating sows from a longitudinal perspective is still unknown. The objectives of this study were to define statistical models and estimate genetic parameters for TV in lactating sows using random regression models, and identify genomic regions and candidate genes associated with HS indicators derived from automatically-recorded TV. RESULTS: Heritability estimates for TV ranged from 0.14 to 0.20 over time (throughout the day and measurement period) and from 0.09 to 0.18 along environmental gradients (EG, - 3.5 to 2.2, which correspond to dew point values from 14.87 to 28.19 ËšC). Repeatability estimates of TV over time and along EG ranged from 0.57 to 0.66 and from 0.54 to 0.77, respectively. TV measured from 12h00 to 16h00 had moderately high estimates of heritability (0.20) and repeatability (0.64), indicating that this period might be the most suitable for recording TV for genetic selection purposes. Significant genotype-by-environment interactions (GxE) were observed and the moderately high estimates of genetic correlations between pairs of extreme EG indicate potential re-ranking of selection candidates across EG. Two important genomic regions on chromosomes 10 (59.370-59.998 Mb) and16 (21.548-21.966 Mb) were identified. These regions harbor the genes CDC123, CAMK1d, SEC61A2, and NUDT5 that are associated with immunity, protein transport, and energy metabolism. Across the four time-periods, respectively 12, 13, 16, and 10 associated genomic regions across 14 chromosomes were identified for TV. For the three EG classes, respectively 18, 15, and 14 associated genomic windows were identified for TV, respectively. Each time-period and EG class had uniquely enriched genes with identified specific biological functions, including regulation of the nervous system, metabolism and hormone production. CONCLUSIONS: TV is a heritable trait with substantial additive genetic variation and represents a promising indicator trait to select pigs for improved heat tolerance. Moderate GxE for TV exist, indicating potential re-ranking of selection candidates across EG. TV is a highly polygenic trait regulated by a complex interplay of physiological, cellular and behavioral mechanisms.

Interactions between corticotropin releasing factor signaling and prophylactic antibiotics on measures of intestinal function in weaned and transported pigs.

The study objective was to evaluate the interaction between corticotrophin releasing factor (CRF) receptor signaling and prophylactic antibiotic administration on intestinal physiology in newly weaned and transported pigs. Pigs (n = 56; 5.70 ± 1.05 kg) were weaned (20.49 ± 0.64 d), a blood sample was taken, and then pigs were given an intraperitoneal injection of saline (SAL; n = 28 pigs) or a CRF receptor antagonist (CRFA; n = 28 pigs; 30 µg/kg body weight; Astressin B), and then were transported in a livestock trailer for 12 h and 49 min. A second and third intraperitoneal injection was given at 4 h 42 min and 11 h 36 min into the transport process, respectively. Following transport, 4 SAL and 4 CRFA pigs were blood sampled and euthanized. The remaining 48 pigs were individually housed and given dietary antibiotics [AB; n = 12 SAL and 12 CRFA pigs; chlortetracycline (441 ppm) + tiamulin (38.6 ppm)] or no dietary antibiotics (NAB; n = 12 SAL and 12 CRFA pigs) for 14 d post-transport. Blood was collected at 12 h and on d 3, 7, and 14, and then pigs were euthanized on d 7 (n = 24) and d 14 (n = 24) post-weaning and transport. Circulating cortisol was reduced (p = 0.05) in CRFA pigs when compared to SAL pigs post-weaning and transport. On d 7, jejunal villus height and crypt depth was greater overall (p < 0.05) in AB-fed pigs versus NAB-fed pigs. On d 14, ileal crypt depth was reduced (p = 0.02) in CRFA pigs when compared to SAL pigs. Jejunal CRF mRNA abundance tended to be reduced (p = 0.09) on d 7 in CRFA pigs versus SAL pigs. On d 14, jejunal tumor necrosis factor-alpha was reduced (p = 0.01) in AB-fed pigs versus NAB-fed pigs. On d 7, change in glucose short-circuit current tended to be increased (p = 0.07) in CRFA pigs fed the AB diet when compared to CRFA pigs fed the NAB diet. In conclusion, CRFA pigs and pigs fed AB had some similar biological intestinal function measures post-weaning and transport.

Genetic parameters for automatically-measured vaginal temperature, respiration efficiency, and other thermotolerance indicators measured on lactating sows under heat stress conditions.

BACKGROUND: Genetic selection based on direct indicators of heat stress could capture additional mechanisms that are involved in heat stress response and enable more accurate selection for more heat-tolerant individuals. Therefore, the main objectives of this study were to estimate genetic parameters for various heat stress indicators in a commercial population of Landrace × Large White lactating sows measured under heat stress conditions. The main indicators evaluated were: skin surface temperatures (SST), automatically-recorded vaginal temperature (TV), respiration rate (RR), panting score (PS), body condition score (BCS), hair density (HD), body size (BS), ear size, and respiration efficiency (Reff). RESULTS: Traits based on TV presented moderate heritability estimates, ranging from 0.15 ± 0.02 to 0.29 ± 0.05. Low heritability estimates were found for SST traits (from 0.04 ± 0.01 to 0.06 ± 0.01), RR (0.06 ± 0.01), PS (0.05 0.01), and Reff (0.03 ± 0.01). Moderate to high heritability values were estimated for BCS (0.29 ± 0.04 for caliper measurements and 0.25 ± 0.04 for visual assessments), HD (0.25 ± 0.05), BS (0.33 ± 0.05), ear area (EA; 0.40 ± 0.09), and ear length (EL; 0.32 ± 0.07). High genetic correlations were estimated among SST traits (> 0.78) and among TV traits (> 0.75). Similarly, high genetic correlations were also estimated for RR with PS (0.87 ± 0.02), with BCS measures (0.92 ± 0.04), and with ear measures (0.95 ± 0.03). Low to moderate positive genetic correlations were estimated between SST and TV (from 0.25 ± 0.04 to 0.76 ± 0.07). Low genetic correlations were estimated between TV and BCS (from - 0.01 ± 0.08 to 0.06 ± 0.07). Respiration efficiency was estimated to be positively and moderately correlated with RR (0.36 ± 0.04), PS (0.56 ± 0.03), and BCS (0.56 ± 0.05 for caliper measurements and 0.50 ± 0.05 for the visual assessments). All other trait combinations were lowly genetically correlated. CONCLUSIONS: A comprehensive landscape of heritabilities and genetic correlations for various thermotolerance indicators in lactating sows were estimated. All traits evaluated are under genetic control and heritable, with different magnitudes, indicating that genetic progress is possible for all of them. The genetic correlation estimates provide evidence for the complex relationships between these traits and confirm the importance of a sub-index of thermotolerance traits to improve heat tolerance in pigs.

l-Glutamine supplementation reduces gastrointestinal permeability and biomarkers of physiological stress in preweaning Holstein heifer calves.

l-Glutamine supplementation improves gastrointestinal and immune function in dairy calves during controlled immune and stress challenges. However, it is unknown whether supplementing milk replacer (MR) with l-glutamine improves preweaning dairy calf health and welfare under production conditions. Therefore, the study objective was to evaluate the effects of supplementing MR with l-glutamine on gastrointestinal permeability, immune function, growth performance, postabsorptive metabolic biomarkers, and physiological stress response in preweaning dairy calves. In 3 repetitions, Holstein heifer calves (n = 30; 1.5 ± 0.5 d old; 37.1 ± 0.86 kg body weight) were blocked by serum total protein, body weight, and age, and provided MR (3.8 L/calf per d; 24% CP, 17% fat, 12.5% solids) supplemented with l-glutamine (GLN; 10g/kg MR powder; n = 5 calves/repetition) or nonsupplemented (NSMR; n = 5 calves/repetition). Calves were individually housed with ad libitum starter grain and water access until weaning (56.4 ± 0.5 d old). At 1 and 6 wk of age, urinary catheters were placed, and calves were orally dosed with 1 L of chromium (Cr)-EDTA. Urine samples were collected over a 24-h period for Cr output analysis as an in vivo biomarker of gastrointestinal permeability. Blood was collected on study d 1, 5, 7, 14, 21, 42, and 56 to measure white blood cell counts, cortisol, insulin, glucose, nonesterified fatty acids, serum amyloid A, haptoglobin, and neutrophil: lymphocytes. Two study intervals were used in the statistical analyses, representing greater (P1; wk 1-3) and reduced (P2; wk 4-8) enteric disease susceptibility. Data were analyzed using PROC GLIMMIX in SAS 9.4 (SAS Institute Inc.) with calf as the experimental unit. Overall, total urinary Cr output was reduced in GLN versus NSMR calves. Total Cr output was reduced at 1 wk of age in GLN versus NSMR calves, but no differences were detected at 6 wk of age. Neutrophil:lymphocyte was decreased both overall and during P2 in GLN versus NSMR calves, and neutrophil counts tended to be reduced in GLN versus NSMR calves during P2. No MR treatment differences were detected for average daily feed intake, average daily gain, body measurements, postabsorptive metabolic biomarkers, disease scores, and therapeutic treatments between GLN and NSMR calves. In summary, l-glutamine supplementation reduced gastrointestinal permeability and biomarkers of physiological stress in preweaning Holstein heifer calves.

Differential Responses of Physiological Parameters, Production Traits, and Blood Metabolic Profiling between First- and Second-Parity Holstein Cows in the Comparison of Spring versus Summer Seasons.

Heat stress (HS) negatively influences cows' welfare and productivity. Therefore, a better understanding of the physiological and molecular mechanisms of HS responses from multiple parities is paramount for the development of effective management and breeding strategies. In comparison with first-parity cows in the spring (Spring-1), first-parity cows in the summer (Summer-1) had a significantly higher rectal temperature (RT), respiration rate (RR), drooling score (DS), and daily activity (DA), while lower (P < 0.05) daily rumination (DR), seven-day average milk yield (7AMY), milk yield on sampling day (MY_S), milk yield on test day (MY_T), and lactose percentage (LP) were observed. When comparing the spring (Spring-2) and summer (Summer-2) of the second-parity cows, significant differences were also found in RT, RR, DS, DA, and DR (P < 0.05), corresponding to similar trends with the first parity while having smaller changes. Moreover, significantly negative impacts on performance traits were only observed on fat percentage (FP) and LP. These results showed that there were different biological responses between first- and second-parity Holstein cows. Further, 18 and 17 metabolites were involved in the seasonal response of first- and second-parity cows, respectively. Nine differential metabolites were shared between the two parities, and pathway analyses suggested that cows had an inhibited tricarboxylic acid cycle, increased utilization of lipolysis, and a dysregulated gut microbiome during the summer. The metabolites identified exclusively for each parity highlighted the differences in microbial response and host amino acid metabolism between two parities in response to HS. Moreover, glucose, ethanol, and citrate were identified as potential biomarkers for distinguishing individuals between Spring-1 and Summer-1. Ethanol and acetone were better predictors for distinguishing individuals between Spring-2 and Summer-2. Taken together, the present study demonstrated the impact of naturally induced HS on physiological parameters, production traits, and the blood metabolome of Holstein cows. There are different biological responses and regulation mechanisms between first- and second-parity Holstein cows.

Investigating the effects of jute nesting material and enriched piglet mats on sow welfare and piglet survival.

Domesticated sows are motivated to perform nesting behavior prior to farrowing, and nesting material can reduce piglet cold stress. However, nesting material may not be practical in most production systems due to the potential for clogging slurry systems. Therefore, the study objectives were to assess an alternative nesting material provided prior to farrowing on sow welfare and piglet survival, and to investigate the effect of the entire nesting environment on piglet survival and growth performance. We hypothesized that the provision of jute nesting material would decrease sow stress and farrowing duration, and that nesting mat provision would allow piglets to remain euthermic and improve survival and growth. Sows (N = 20) were randomly assigned to one of two treatments: a farrowing crate with three pieces of 40.6 × 21.6 cm jute nesting material (Nest; n = 10) and two enriched piglet mats made from an acrylic board (28.0 × 86.4 cm) covered with a microfiber material, or a farrowing crate without nesting material (Control; n = 10) and one standard plastic piglet mat (28.0 × 86.4 cm). Jute pieces were attached to the front of the crate to prevent substrate from falling through the slatted floors. Saliva samples were collected to measure cortisol and immunoglobulin A (IgA), on days -1, 0, 1, and 2 relative to farrowing, and a final sample was collected at weaning (day 16.9 ±â€…0.18). Blood was collected from four piglets per litter to measure immunoglobulin G (IgG) at 48 h, day 7, and weaning. Piglet skin temperature (TS) was measured on two piglets per litter using an infrared camera for 3 d after birth at 0800, 1200, 1600, and 2000 h. One piglet was randomly chosen from the heat lamp and nonheat lamp side of the crate to measure TS. Video was continuously coded for observations of jute- and crate-directed interactions. Data were analyzed as a mixed model analysis of variance in SAS 9.4. Nest sows performed less crate-directed behavior than Control sows (P = 0.02). Cortisol tended to be reduced in Nest sows (P = 0.08) when compared to Controls, but no differences in IgA concentrations (P > 0.40) were detected. Nest piglets tended to be heavier on day 7 (P < 0.10), had greater IgG concentrations (P = 0.03), and had greater TS (P = 0.02) versus Controls. No farrowing duration or number of stillbirth differences were observed (P > 0.70). The jute material and piglet nests positively impacted sow welfare and piglet measures but did not translate into improved piglet survival.

Evaluating the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars.

An accurate understanding of boar temperature preferences may allow the swine industry to design and utilize environmental control systems in boar facilities more precisely. Therefore, the study objective was to determine the temperature preferences of sexually mature Duroc, Landrace, and Yorkshire boars. Eighteen, 8.57 ± 0.10-mo-old boars (N = 6 Duroc, 6 Landrace, and 6 Yorkshire; 186.25 ± 2.25 kg) were individually tested in thermal apparatuses (12.20 m × 1.52 m × 1.86 m) that allowed free choice of their preferred temperature within a 8.92 to 27.92 ºC range. For analyses, the apparatuses were divided into five thermal zones (3.71 m2/thermal zone) with temperature recorded 1.17 m above the floor in the middle of each zone. Target temperatures for thermal zones 1 to 5 were 10, 15, 20, 25, and 30 ºC, respectively. All boars were given a 24-h acclimation phase followed by a 24-h testing phase within the thermal apparatuses. Daily feed allotments (3.63 kg/d) were provided to each boar and all boars were allowed to consume all feed prior to entering the thermal apparatus. Water was provided ad libitum within the thermal apparatuses with 1 waterer per thermal zone. During testing, boars were video recorded continuously to evaluate behavior (inactive, active, or other), posture (lying, standing, or other), and thermal zone the boar occupied. All parameters were recorded in 15 min intervals using instantaneous scan sampling. Data were analyzed using GLM in JMP 15. For the analyses, only time spent lying or inactive were used because they were observed most frequently (lying 80.02%, inactive 77.64%) and were deemed to be associated with comfort based on previous research. Percent time spent active (19.73%) or standing (15.87%) were associated with latrine or drinking activity and were too low to accurately analyze as an indicator of thermal preference. Breed did not affect temperature preference (P > 0.05). A cubic regression model determined that boars spent the majority of their time inactive at 25.50 ºC (P < 0.01) and lying (both sternal and lateral) at 25.90 ºC (P < 0.01). These data suggest that boar thermal preferences did not differ by breed and that boars prefer temperatures at the upper end of current guidelines (10.00 to 25.00 ºC).

Evaluating phenotypes associated with heat tolerance and identifying moderate and severe heat stress thresholds in lactating sows housed in mechanically or naturally ventilated barns during the summer under commercial conditions.

An accurate understanding of heat stress (HS) temperatures and phenotypes that indicate HS tolerance is necessary to improve swine HS resilience. Therefore, the study objectives were 1) to identify phenotypes indicative of HS tolerance, and 2) to determine moderate and severe HS threshold temperatures in lactating sows. Multiparous (4.10 ± 1.48) lactating sows and their litters (11.10 ± 2.33 piglets/litter) were housed in naturally ventilated (n = 1,015) or mechanically ventilated (n = 630) barns at a commercial sow farm in Maple Hill, NC, USA between June 9 and July 24, 2021. In-barn dry bulb temperatures (TDB) and relative humidity were continuously recorded for naturally ventilated (26.38 ± 1.21 °C and 83.38 ± 5.40%, respectively) and mechanically ventilated (26.91 ± 1.80 °C and 77.13 ± 7.06%, respectively) barns using data recorders. Sows were phenotyped between lactation days 11.28 ± 3.08 and 14.25 ± 3.26. Thermoregulatory measures were obtained daily at 0800, 1200, 1600, and 2000 h and included respiration rate, and ear, shoulder, rump, and tail skin temperatures. Vaginal temperatures (TV) were recorded in 10 min intervals using data recorders. Anatomical characteristics were recorded, including ear area and length, visual and caliper-assessed body condition scores, and a visually assessed and subjective hair density score. Data were analyzed using PROC MIXED to evaluate the temporal pattern of thermoregulatory responses, phenotype correlations were based on mixed model analyses, and moderate and severe HS inflection points were established by fitting TV as the dependent variable in a cubic function against TDB. Statistical analyses were conducted separately for sows housed in mechanically or naturally ventilated barns because the sow groups were not housed in each facility type simultaneously. The temporal pattern of thermoregulatory responses was similar for naturally and mechanically ventilated barns and several thermoregulatory and anatomical measures were significantly correlated with one another (P < 0.05), including all anatomical measures as well as skin temperatures, respiration rates, and TV. For sows housed in naturally and mechanically ventilated facilities, moderate HS threshold TDB were 27.36 and 26.69 °C, respectively, and severe HS threshold TDB were 29.45 and 30.60 °C, respectively. In summary, this study provides new information on the variability of HS tolerance phenotypes and environmental conditions that constitute HS in commercially housed lactating sows.

Climate change and the associated increase in global temperatures have a well-described negative impact on swine production. Therefore, improving swine heat stress resilience is of utmost importance to reduce the deleterious effects of heat stress on swine health, performance, and welfare. Genomic selection for heat stress resilience may be a viable strategy to improve swine productivity in a changing climate. However, identifying environmental conditions that constitute heat stress and deriving novel traits that can be easily collected on farm and provide accurate and precise predictions of heat stress tolerance is a necessary step. The present study demonstrated that housing conditions had a limited influence on heat stress tolerance phenotypes, several anatomical and thermoregulatory measures were correlated, and housing conditions impacted heat stress threshold temperatures. Results from this study may be applied to large-scale phenotyping initiatives to develop or refine genomic selection indexes for heat stress resilience in pigs.

A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows.

BACKGROUND: Although thermal indices have been proposed for swine, none to our knowledge differentiate by reproductive stage or predict thermal comfort using behavioral and physiological data. The study objective was to develop a behavior and physiology-based decision support tool to predict thermal comfort and stress in multiparous (3.28 ± 0.81) non-pregnant (n = 11), mid-gestation (n = 13), and late-gestation (n = 12) sows. RESULTS: Regression analyses were performed using PROC MIXED in SAS 9.4 to determine the optimal environmental indicator [dry bulb temperature (TDB) and dew point] of heat stress (HS) in non-pregnant, mid-gestation, and late-gestation sows with respiration rate (RR) and body temperature (TB) successively used as the dependent variable in a cubic function. A linear relationship was observed for skin temperature (TS) indicating that TDB rather than the sow HS response impacted TS and so TS was excluded from further analyses. Reproductive stage was significant for all analyses (P < 0.05). Heat stress thresholds for each reproductive stage were calculated using the inflections points of RR for mild HS and TB for moderate and severe HS. Mild HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 25.5, 25.1, and 24.0 °C, respectively. Moderate HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 28.1, 27.8, and 25.5 °C, respectively. Severe HS inflection points were similar for non-pregnant and mid-gestation sows (32.9 °C) but differed for late-gestation sows (30.8 °C). These data were integrated with previously collected behavioral thermal preference data to estimate the TDB that non-pregnant, mid-gestation, and late-gestation sows found to be cool (TDB < TDB preference range), comfortable (TDB = TDB preference range), and warm (TDB preference range < TDB < mild HS). CONCLUSIONS: The results of this study provide valuable information about thermal comfort and thermal stress thresholds in sows at three reproductive stages. The development of a behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows is expected to provide swine producers with a more accurate means of managing sow environments.

Smart capsule for targeted proximal colon microbiome sampling.

The gastrointestinal (GI) tract, particularly the colon region, holds a highly diverse microbial community that plays an important role in the metabolism, physiology, nutrition, and immune function of the host body. Accumulating evidence has revealed that alteration in these microbial communities is the pivotal step in developing various metabolic diseases, including obesity, inflammatory bowel disease (IBD), and colorectal cancer. However, there is still a lack of clear understanding of the interrelationship between microbiota and diet as well as the effectiveness of chemoprevention strategies, including pre and probiotic agents in modifying the colonic microbiota and preventing digestive diseases. Existing methods for assessing these microbiota-diet interactions are often based on samples collected from the feces or endoscopy techniques which are incapable of providing information on spatial variations of the gut microbiota or are considered invasive procedures. To address this need, here we have developed an electronic-free smart capsule that enables site-specific sampling of the gut microbiome within the proximal colon region of the GI tract. The 3D printed device houses a superabsorbent hydrogel bonded onto a flexible polydimethylsiloxane (PDMS) disk that serves as a milieu to collect the fluid in the gut lumen and its microbiome by rapid swelling and providing the necessary mechanical actuation to close the capsule after the sampling is completed. The targeted colonic sampling is achieved by coating the sampling aperture on the capsule with a double-layer pH-sensitive enteric coating, which delays fluid in the lumen from entering the capsule until it reaches the proximal colon of the GI tract. To identify the appropriate pH-responsive double-layer coating and processing condition, a series of systematic dissolution characterizations in different pH conditions that mimicked the GI tract was conducted. The effective targeted microbial sampling performance and preservation of the smart capsule with the optimized design were validated using both realistic in vitro GI tract models with mixed bacteria cultures and in vivo with pigs as an animal model. The results from 16s rRNA and WideSeq analysis in both in vitro and in vivo studies showed that the bacterial population sampled within the retrieved capsule closely matched the bacterial population within the targeted sampling region (proximal colon). Herein, it is envisioned that such smart sampling capsule technology will provide new avenues for gastroenterological research and clinical applications, including diet-host-microbiome relationships, focused on human GI function and health. STATEMENT OF SIGNIFICANCE: The colonic microbiota plays a major role in the etiology of numerous diseases. Extensive efforts have been conducted to monitor the gut microbiome using sequencing technologies based on samples collected from feces or mucosal biopsies that are typically obtained by colonoscopy. Despite the simplicity of fecal sampling procedures, they are incapable of preserving spatial and temporal information about the bacteria through the gastrointestinal (GI) tract. In contrast, colonoscopy is an invasive and impractical approach to frequently assess the effect of dietary and therapeutic intake on the microbiome and their impact on the health of the patient. Here, we developed a non-invasive capsule that enables targeted sampling from the ascending colon, thereby providing crucial information for disease prediction and monitoring.

Technical Note: A procedure to place urinary catheters in 1- and 6-week-old preweaned Holstein heifer calves for the in vivo evaluation of intestinal permeability.

Oral administration of indigestible markers and subsequent urine collection is a useful method to determine in vivo gastrointestinal tract (GIT) permeability in cattle for research purposes. However, urine sampling techniques often rely on total waste collection, which reduces the ability to perform more frequent sampling and obtain accurate volumes and sterile samples. An alternative is urethral catheterization, though the feasibility of this technique has not been thoroughly tested in preweaned Holstein heifer calves. The study objective was to develop a urethral catheter placement procedure in preweaned Holstein heifer calves for continuous and accurate urine collection to evaluate GIT permeability using an indigestible marker. Fifteen Holstein heifer calves had catheters placed at approximately 1 wk (8.0 ± 1.5 d) and 6 wk (40.0 ± 1.5 d) of age. During the procedure, calves were individually housed and restrained. The vulva was sterilized and then a sterile, lubricated speculum was inserted into the vagina. A sterile 0.09 cm diameter guidewire was guided into a lubricated, sterile 10 French Foley catheter. The catheter was inserted at approximately 5 through 7 cm into the urethral opening, guided into the bladder, and the catheter balloon was filled with 10 mL of water. The guidewire was removed, and urine flow confirmed correct placement before a 4-L urinary drainage bag was attached to the catheter. After catheterization (24 h), 1 L of chromium (Cr)-ethylenediaminetetraacetic acid was orally dosed to the calves. Calf health observations were made six times over a 48-h period, and any occurrence of vaginal discharge, tissue discharge in catheter, bleeding, inflammation, or abnormal urine was considered a localized reaction. The proportion of localized reactions for each age group was determined using Microsoft Excel, and the total Cr output was analyzed using PROC GLIMMIX. Localized reactions occurred for 20.0% of the 1-wk-old calves and 13.3% of the 6-wk-old calves. In the first 4 h, urine was collected every 15 min, and there were no overall Cr output differences (P = 0.38; 10.28 ± 3.21 mg Cr) when comparing 1- and 6-wk-old calves. However, 1-wk-old calves tended (P = 0.08) to have greater overall Cr output at 480 min (19.2%) and 1,440 min (41.9%) when compared with 6-wk-old calves. In summary, urinary catheterization is a viable urinary collection method for the determination of in vivo GIT permeability in preweaned Holstein heifer calves.

Neonatal calves are highly susceptible to enteric disease during their first few weeks of life, and enteric disease is the leading cause of preweaning morbidity and mortality. A consequence of enteric disease is greater gastrointestinal tract (GIT) permeability in neonatal calves, which is also influenced by reduced intestinal maturity and environmental factors. Therefore, an accurate and precise method of evaluating GIT permeability in neonatal calves is necessary to develop appropriate treatment and mitigation strategies. The oral administration of indigestible markers and measurement of their presence in urine is an accepted method to determine the total GIT permeability in mature heifers. However, current urine collection methods in preweaned heifer calves may not be reliable. Therefore, the study objective was to develop a urinary catheterization method to collect urine accurately and precisely for the in vivo determination of GIT permeability in 1- and 6-wk-old Holstein heifer calves. It was determined that the urinary catheterization procedure and collection system developed in this study were viable and could be applied when evaluating GIT permeability in preweaned Holstein heifer calves using orally dosed indigestible markers.

In Utero Heat Stress Has Minimal Impacts on Processed Pork Products: A Comparative Study.

This study aimed to determine what effects in utero heat stress (IUHS) in pigs may have on quality of processed pork products. In two experiments, patties and emulsion sausages were prepared from lean and fat from pigs subjected to IUHS or in utero thermoneutral (IUTN) conditions. Patties formulated to contain 25% added fat had altered textural properties compared to those without additional fat, as shown by lower hardness, cohesiveness, springiness, and chewiness values (p < 0.05), which was not affected by IUHS treatment. Neither fat content nor IUHS treatment affected fluid losses of patties (p > 0.05). In general, 25% added fat patties had greater L*, a*, b*, hue angle, and chroma values than lean patties (p < 0.05). However, 25% added fat patties from the IUHS treatment maintained superior color stability during aerobic display, despite lean patties from this treatment exhibiting increased lipid oxidation (p < 0.05). For emulsion sausages, minimal differences in quality attributes and oxidative stability were found between treatment groups. Subcutaneous fat from IUHS pigs had greater C20:1 and C20:2 than IUTN (p < 0.05), although the magnitude of these differences was slight. Overall, the findings of this study suggest IUHS would have minimal impacts on the functional properties of raw pork, resulting in similar final quality of processed products to IUTN.

Characterizing the effect of incrementally increasing dry bulb temperature on linear and nonlinear measures of heart rate variability in nonpregnant, mid-gestation, and late-gestation sows.

Characterizing the sow physiological response to an increased heat load is essential for effective heat stress mitigation. The study objective was to characterize the effects of a 400-min heating episode on sow heart rate variability (HRV) at different reproductive stages. HRV is a commonly used noninvasive proxy measure of autonomic function. Twenty-seven sows were enrolled in the study according to their gestation stage at time of selection: 1) nonpregnant (NP; n = 7), 2) mid-gestation (MID; 57.3 ± 11.8 d gestation; n = 11), and 3) late-gestation (LATE; 98.8 ± 4.9 d gestation; n = 8). The HRV data utilized in the study were collected from each pig as the dry bulb temperature in the room increased incrementally from 19.84 ± 2.15 °C to 35.54 ± 0.43 °C (range: 17.1-37.5 °C) over a 400-min period. After data collection, one 5-min set of continuous heart rate data were identified per pig for each of nine temperature intervals (19-20.99, 21-22.99, 23-24.99, 25-26.99, 27-28.99, 29-30.99, 31-32.99, 33-34.99, and 35-36.99 °C). Mean inter-beat interval length (RR), standard deviation of r-r intervals (SDNN), root mean square of successive differences (RMSSD), high frequency spectral power (HF), sample entropy (SampEn), short-term detrended fluctuation analysis (DFAα1), and three measures (%REC, DET, LMEAN) derived from recurrence quantification analysis were calculated for each data set. All data were analyzed using the PROC GLIMMIX procedure in SAS 9.4. Overall, LATE sows exhibited lower RR than NP sows (P < 0.01). The standard deviation of r-r intervals and RMSSD differed between each group (P < 0.01), with LATE sows exhibiting the lowest SDNN and RMSSD and NP sows exhibiting the greatest SDNN and RMSSD. Late-gestation sows exhibited lower HF than both MID and NP sows (P < 0.0001), greater DFA values than NP sows (P = 0.05), and greater DET compared to MID sows (P = 0.001). Late-gestation also sows exhibited greater %REC and LMEAN compared to MID (P < 0.01) and NP sows (all P < 0.01). In conclusion, LATE sows exhibited indicators of greater autonomic stress throughout the heating period compared to MID and NP sows. However, temperature by treatment interactions were not detected as dry bulb increased. Future studies are needed to fully elucidate the effect of gestational stage and increasing dry bulb temperature on sow HRV.

Pregnant pigs may be at a higher risk of poor physiological outcomes due to heat exposure compared to mature female pigs that are not pregnant. The purpose of this study was to evaluate the stress response of pregnant pigs to increasing environmental temperatures using heart rate variability, a noninvasive measure commonly used to evaluate the physiological stress response. Our findings show that pregnant pigs, particularly those who are closer to giving birth, exhibit greater evidence of physiological stress compared to pigs who are not pregnant. However, we did not find evidence that increasing environmental temperature throughout the experimental period was a primary reason for the increased stress exhibited by pregnant pigs. It is possible that the physiological changes that normally occur during pregnancy may have masked the physiological stress response typically associated with increased heat exposure.

Electronically controlled cooling pads can improve litter growth performance and indirect measures of milk production in heat-stressed lactating sows.

Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production. However, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., total heat production [THP]) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg body weight [BW]) and litters were assigned to either an ECP (n = 3/repetition) or a non-functional ECP (NECP; n = 3/repetition) and placed into farrowing crates within indirect calorimeters from days 3.7 ± 0.5 to 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 0.26 °C nighttime to 33.09 ± 0.19°C daytime). On days 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine THP and THP/kg BW0.75. Body temperature (TB) was measured hourly using vaginal implants, and respiration rate (RR; breaths per minute [bpm]) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Sow feed intake (FI) was assessed daily. Litter weights were obtained at birth, on days 4, 8, 14, and 18 of lactation, and at weaning. Data were analyzed using PROC GLIMMIX with sow and/or litter as the experimental unit. An overall decrease (P < 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40 °C) was observed in ECP vs. NECP sows. An increase in THP (P < 0.01; 20.4%) and THP/kg BW0.75 (P < 0.01; 23.1%) was observed for ECP when compared with NECP sows and litters. Litter average daily gain and weaning weight were increased (P < 0.05; 25.0 and 19.2%, respectively) for ECP vs. NECP litters. No FI differences were observed (P = 0.40) when comparing ECP (5.66 ± 0.31 kg/d) and NECP (5.28 ± 0.31 kg/d) sows. In summary, ECPs improve litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical HS.

Lactating sows are heat stress sensitive due to greater feed intake and metabolic heat production to support milk production. Therefore, heat-stressed lactating sows reduce their feed intake and undergo physiological changes that prioritize survival over productivity which reduces milk production. Reduced milk production has negative downstream effects on the litter and can decrease litter growth performance and health status. The negative effects of heat stress on lactating sows may be ameliorated by using electronically controlled cooling pads. Electronically controlled cooling pads improve the ability of lactating sows to maintain a normal body temperature under heat stress conditions. However, it is unknown whether these pads can improve lactating sow feed intake, milk production, and subsequently litter performance under heat stress conditions. It was determined that electronically controlled cooling pads were effective in increasing piglet body weight gain and weaning weight and increasing indirect measures of sow milk production independent of greater sow feed intake. In addition, the electronically controlled cooling pads allowed sows to maintain a normal body temperature under heat stress conditions. These data suggest that electronically controlled cooling pads can be an effective technology to improve lactating sow and litter performance under heat stress conditions.

Small intestinal sampling capsule for inflammatory bowel disease type detection and management.

Although serum and fecal biomarkers (e.g., lactoferrin, and calprotectin) have been used in management and distinction between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), none are proven to be a differential diagnostic tool between Crohn's disease (CD) and ulcerative colitis (UC). The main challenge with laboratory-based biomarkers in the stool test is the inability to indicate the location of the disease/inflammation in the gastrointestinal (GI) tract due to the homogenous nature of the collected fecal sample. For the first time, we have designed and developed a battery-free smart capsule that will allow targeted sampling of inflammatory biomarkers inside the gut lumen of the small intestine. The capsule is designed to provide a simple and non-invasive complementary tool to fecal biomarker analysis to differentiate the type of IBD by pinpointing the site of inflammatory biomarkers secretion (e.g., small or large bowel) throughout the GI tract. The capsule takes advantage of the rapid change from an acidic environment in the stomach to higher pH levels in the small intestine to dissolve a pH-sensitive polymeric coating as a means to activate the sampling process of the capsule within the small intestine. A swelling polyacrylamide hydrogel is placed inside the capsule as a milieu to collect the sampled GI fluid while also providing the required mechanical actuation to close the capsule once the sampling is completed. The hydrogel component along with the collected GI fluid can be easily obtained from the capsule through the screw-cap design for further extraction and analysis. As a proof of concept, the capsule's performance in sampling and extraction of bovine serum albumin (BSA) and calprotectin - a key biomarker of inflammation - was assessed within the physiologically relevant ranges. The ratio of extracted biomarkers relative to that in the initial sampling environment remained constant (∼3%) and independent of the sampling matrix in both in vitro and ex vivo studies. It is believed that the demonstrated technology will provide immediate impact in more effective IBD type differential diagnostic and treatment strategies by providing a non-invasive assessment of inflammation biomarkers profile throughout the digestive tract.

Characterizing the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat stressed pigs at 10 and 15 weeks of age.

In utero heat stress alters postnatal physiological and behavioral stress responses in pigs. However, the mechanisms underlying these alterations have not been determined. The study objective was to characterize the postnatal hypothalamic-pituitary-adrenal axis response of in utero heat-stressed pigs. Pigs were subjected to a dexamethasone suppression test followed by a corticotrophin releasing hormone challenge at 10 and 15 weeks of age. Following the challenge, hypothalamic, pituitary, and adrenal tissues were collected from all pigs for mRNA abundance analyses. At 10 weeks of age, in utero heat-stressed pigs had a reduced (P < 0.05) cortisol response to the corticotrophin releasing hormone challenge versus controls. Additionally, the cortisol response tended to be greater overall (P < 0.10) in 15 versus 10-week-old pigs in response to the dexamethasone suppression test. The cortisol response tended to be reduced overall (P < 0.10) in 15 versus 10-week-old pigs in response to the corticotrophin releasing hormone challenge. Hypothalamic corticotropin releasing hormone mRNA abundance tended to be greater (P < 0.10) in in utero heat-stressed versus control pigs at 15-weeks of age. In summary, in utero heat stress altered some aspects of the hypothalamic-pituitary-adrenal axis related to corticotropin releasing hormone signaling, and age influenced this response.

Evaluation of sow thermal preference across three stages of reproduction.

The metabolic heat production of modern pigs has increased by an average of 16%, compared with sows of 30 years ago. Therefore, it is likely that temperature recommendations require updating to meet the needs of modern pigs. The objective of this study was to evaluate whether different reproductive stages of sows altered thermal preference and if current recommendations required updating. Twenty multiparous sows (3.4 ± 1.2 parity) in different reproductive stages (nonpregnant: n = 7; mid-gestation: 58.5 ± 5.68 d, n = 6; and late-gestation: 104.7 ± 2.8 d, n = 7) were tested. Thermal preference was individually tested, and sows could freely choose a temperature, using a thermal gradient between 10.4 and 30.5 °C. Sows were given 24 h to acclimate to the thermal apparatus. Before testing began, sows were given daily feed allotment and returned to the apparatus. Video from the 24-h test period was used to record sow behavior (time spent inactive), posture (upright and sternal and lateral lying), and location using instantaneous scan samples every 15 min. Data were analyzed using PROC MIXED procedure in SAS 9.4. A cubic regression model was used to calculate the sow's most preferred temperature based on the location, or temperature, in which they spent the most time. The preference range was calculated using peak temperature preference ±SE for each sow. The reproductive stage altered where sows spent their time within the thermal gradient (P < 0.01). Late-gestation sows preferred cooler temperatures (14.0 °C) than mid-gestation (14.8 °C; P < 0.01) and nonpregnant sows (14.8 °C; P < 0.01). In summary, sow thermal preferences were within the lower half of the current recommended range (10 to 25 °C). This indicates that temperatures at the higher end of the recommended range could be uncomfortable to sows and that the thermal comfort zone of sows may be narrower than recommendations indicate.