In Vivo and In Vitro Characterization of the Recently Emergent PRRSV 1-4-4 L1C Variant (L1C.5) in Comparison with Other PRRSV-2 Lineage 1 Isolates.

The recently emerged PRRSV 1-4-4 L1C variant (L1C.5) was in vivo and in vitro characterized in this study in comparison with three other contemporary 1-4-4 isolates (L1C.1, L1A, and L1H) and one 1-7-4 L1A isolate. Seventy-two 3-week-old PRRSV-naive pigs were divided into six groups with twelve pigs/group. Forty-eight pigs (eight/group) were for inoculation, and 24 pigs (four/group) served as contact pigs. Pigs in pen A of each room were inoculated with the corresponding virus or negative media. At two days post inoculation (DPI), contact pigs were added to pen B adjacent to pen A in each room. Pigs were necropsied at 10 and 28 DPI. Compared to other virus-inoculated groups, the L1C.5-inoculated pigs exhibited more severe anorexia and lethargy, higher mortality, a higher fraction of pigs with fever (>40 °C), higher average temperature at several DPIs, and higher viremia levels at 2 DPI. A higher percentage of the contact pigs in the L1C.5 group became viremic at two days post contact, implying the higher transmissibility of this virus strain. It was also found that some PRRSV isolates caused brain infection in inoculation pigs and/or contact pigs. The complete genome sequences and growth characteristics in ZMAC cells of five PRRSV-2 isolates were further compared. Collectively, this study confirms that the PRRSV 1-4-4 L1C variant (L1C.5) is highly virulent with potential higher transmissibility, but the genetic determinants of virulence remain to be elucidated.

Field Implementation of Forecasting Models for Predicting Nursery Mortality in a Midwestern US Swine Production System.

The performance of five forecasting models was investigated for predicting nursery mortality using the master table built for 3242 groups of pigs (~13 million animals) and 42 variables, which concerned the pre-weaning phase of production and conditions at placement in growing sites. After training and testing each model's performance through cross-validation, the model with the best overall prediction results was the Support Vector Machine model in terms of Root Mean Squared Error (RMSE = 0.406), Mean Absolute Error (MAE = 0.284), and Coefficient of Determination (R2 = 0.731). Subsequently, the forecasting performance of the SVM model was tested on a new dataset containing 72 new groups, simulating ongoing and near real-time forecasting analysis. Despite a decrease in R2 values on the new dataset (R2 = 0.554), the model demonstrated high accuracy (77.78%) for predicting groups with high (>5%) or low (<5%) nursery mortality. This study demonstrated the capability of forecasting models to predict the nursery mortality of commercial groups of pigs using pre-weaning information and stocking condition variables collected post-placement in nursery sites.

Evaluation of oxidized beta-carotene on sow and piglet immune systems, sow reproductive performance, and piglet growth.

This study aimed to determine if supplementation of oxidized-beta carotene (OxC-Beta) improved sow reproductive performance, litter growth performance, vitamin A status, and ability to alter immune cells abundance in sows and piglets, subsequent litter performance, and nursery growth performance. On approximately day 60 of gestation and through the lactation period, 194 sows (blocked by parity) were assigned to a common gestation diet or the common diet supplemented with 80 ppm oxidized beta-carotene (OxC-Beta, Aviagen, Ottawa, ON, Canada). A subset of sows (N = 54 per treatment) were sampled for blood and body weight recorded at the beginning of the study, farrowing, and weaning. A blood sample was taken from a subset of piglets at birth and weaning, and all piglet weights were recorded. Blood was analyzed for vitamin A as retinol concentrations and immunoglobulin G (IgG) and immunoglobulin M (IgG) levels were assessed from the sow's blood. Twelve pigs (N = 6 per treatment) were euthanized at birth and weaning. The livers were collected and analyzed for the Kupffer cell phagocytic activity through flow cytometry. Whole blood was analyzed via flow cytometry for cluster of differentiation (CD335, CD8, and CD4). Colostrum during farrowing and milk at weaning were analyzed for IgG and IgA concentrations. Data were analyzed via SAS 9.4 using MIXED and frequency procedures where appropriate. No differences (P > 0.05) between dietary treatments were observed in sow reproductive performance, feed intake, wean to estrus interval, or piglet growth performance. No differences (P > 0.05) were observed in the plasma or liver for vitamin A. No differences (P > 0.05) were observed in the composition of the colostrum or milk. No immunological differences (P > 0.05) were observed in the piglets' liver and blood or sow antibodies in colostrum and milk. The supplementation of OxC-Beta did (P < 0.05) decrease IgM and tended (P < 0.10) to decrease IgG in sow plasma. No differences (P > 0.05) were observed in the reproductive performance of subsequent litter information from the sows. Gilt litter weaning weight and feed intake were reduced (P < 0.05) compared to sow performance. In conclusion, the supplementation of OxC-Beta at 80 ppm from day 60 of gestation through lactation does not affect the reproductive performance of sows, litter growth performance, vitamin A status, piglet immune status, and antibodies or composition in colostrum and milk.

Beta-carotene is a known antioxidant found in most red and orange-pigmented vegetables and has been documented to have health benefits. However, beta-carotene has been reported to gain oxygen molecules spontaneously, thus oxidizing it. Oxidized beta-carotene has been recognized to provide potential health benefits to animals, although its functions are independent of beta-carotene. Sows in this study were supplemented with an oxidized beta-carotene product to evaluate whether the product could improve reproductive performance, including the number of piglets born alive, piglet birth weight, weaning weight, sow milk quality, and immune function of both the sow and piglets. There were no significant findings between the reproductive performance or difference in colostrum and milk composition of the control sows and the sows supplemented with the product. There was also no difference in piglet growth between the two groups. The product did not affect the measured immune functions of the piglets. However, immunoglobulin G tended to decrease with the use of the product, and there was a decrease in immunoglobulin M. Overall, supplementing the oxidized beta-carotene product did not affect the reproductive performance of sows or the growth performance of piglets.

Risk factors associated with sow mortality in breeding herds under one production system in the Midwestern United States.

Sow mortality has significantly increased throughout the world over the past several years, and it is a growing concern to the global swine industry. Sow mortality increases economic losses, including higher replacement rates, affects employees' morale, and raises concerns about animal well-being and sustainability. This study aimed to assess herd-level risk factors associated with sow mortality in a large swine production system in the Midwestern United States. This retrospective observational study used available production, health, nutritional, and management information between July 2019 and December 2021. A Poisson mixed regression model was used to identify the risk factors and to build a multivariate model using the weekly mortality rate per 1000 sows as the outcome. Different models were used to identify the risk factors according to this study's main reasons for sow mortality (total death, sudden death, lameness, and prolapse). The main reported causes of sow mortality were sudden death (31.22 %), lameness (28.78 %), prolapse (28.02 %), and other causes (11.99 %). The median (25th-75th percentile) distribution of the crude sow mortality rate/1000 sows was 3.37 (2.19 - 4.16). Breeding herds classified as epidemic for porcine reproductive and respiratory syndrome virus (PRRSV) were associated with higher total death, sudden death, and lameness death. Open pen gestation was associated with a higher total death and lameness compared with stalls. Pulses of feed medication was associated with lower sow mortality rate for all outcomes. Farms not performing bump feeding were associated with higher sow mortality due to lameness and prolapses, while Senecavirus A (SVA)-positive herds were associated with a higher mortality rate for total deaths and deaths due to lameness. Disease interactions (herds Mycoplasma hyopneumoniae positive and epidemic for PRRSV; SVA positive herds and epidemic for PRRSV) were associated with higher mortality rates compared to farms with single disease status. This study identified and measured the major risk factors associated with total sow mortality rate, sudden deaths, lameness deaths, and prolapse deaths in breeding herds under field conditions.

Utilizing productivity and health breeding-to-market information along with disease diagnostic data to identify pig mortality risk factors in a U.S. swine production system.

Aggregated diagnostic data collected over time from swine production systems is an important data source to investigate swine productivity and health, especially when combined with records concerning the pre-weaning and post-weaning phases of production. The combination of multiple data streams collected over the lifetime of the pigs is the essence of the whole-herd epidemiological investigation. This approach is particularly valuable for investigating the multifaceted and ever-changing factors contributing to wean-to-finish (W2F) swine mortality. The objective of this study was to use a retrospective dataset ("master table") containing information on 1,742 groups of pigs marketed over time to identify the major risk factors associated with W2F mortality. The master table was built by combining historical breed-to-market performance and health data with disease diagnostic records (Dx Codes) from marketed groups of growing pigs. After building the master table, univariate analyses were conducted to screen for risk factors to be included in the initial multivariable model. After a stepwise backward model selection approach, 5 variables and 2 interactions remained in the final model. Notably, the diagnosis variable significantly associated with W2F mortality was porcine reproductive and respiratory syndrome virus (PRRSV). Closeouts with clinical signs suggestive of Salmonella spp. or Escherichia coli infection were also associated with higher W2F mortality. Source sow farm factors that remained significantly associated with W2F mortality were the sow farm PRRS status, average weaning age, and the average pre-weaning mortality. After testing for the possible interactions in the final model, two interactions were significantly associated with wean-to-finish pig mortality: (1) sow farm PRRS status and a laboratory diagnosis of PRRSV and (2) average weaning age and a laboratory diagnosis of PRRS. Closeouts originating from PRRS epidemic or PRRS negative sow farms, when diagnosed with PRRS in the growing phase, had the highest W2F mortality rates. Likewise, PRRS diagnosis in the growing phase was an important factor in mortality, regardless of the average weaning age of the closeouts. Overall, this study demonstrated the utility of a whole-herd approach when analyzing diagnostic information along with breeding-to-market productivity and health information, to measure the major risk factors associated with W2F mortality in specified time frames and pig populations.

Review of regulations and indications for the use of in-feed antimicrobials for production animals.

Antimicrobials have been fed to livestock for more than 60 years. Veterinarians and producers saw tremendous gains in health and performance, and usage became widespread. Over time, improved management reduced some of the benefit of many feed-through antimicrobials except for a few important diseases. As a result of concerns about antimicrobial resistance, the US FDA restricted the use of medically important antimicrobials. Starting in 2017, medically important antimicrobials were restricted to therapeutic purposes only, and only under the order of a veterinarian. The aim of this review is to provide an overview of commonly used antimicrobials in livestock feed and regulatory changes regarding the veterinary feed directive. When used judiciously, in-feed antimicrobials are an important tool to ensure the health and welfare of food animals while preserving the effectiveness for animals and humans.

Whole-herd risk factors associated with wean-to-finish mortality under the conditions of a Midwestern USA swine production system.

Swine wean-to-finish (W2F) mortality is a multifactorial, dynamic process and a key performance indicator of commercial swine production. Although swine producers typically capture the relevant data, analysis of W2F mortality risk factors is often hindered by the fact that, even if data is available, they are typically in different formats, non-uniform, and dispersed among multiple unconnected databases. In this study, an automated framework was created to link multiple data streams to specific cohorts of market animals, including sow farm productivity parameters, sow farm and growing pig health factors, facilities, management factors, and closeout data from a Midwestern USA production system. The final dataset (master-table) contained breeding-to-market data for 1,316 cohorts of pigs marketed between July 2018 and June 2019. Following integration into a master-table, continuous explanatory variables were categorized into quartiles averages, and the W2F mortality was log-transformed, reporting geometric mean mortality of 8.69 % for the study population. Further, univariate analyses were performed to identify individual variables associated with W2F mortality (p < 0.10) for further inclusion in a multivariable model, where model selection was applied. The final multivariable model consisted of 13 risk factors and accounted for 68.2 % (R2) of the variability of the W2F mortality, demonstrating that sow farm health and performance are closely linked to downstream W2F mortality. Higher sow farm productivity was associated with lower subsequent W2F mortality and, conversely, lower sow farm productivity with higher W2F mortality e.g., groups weaned in the highest quartiles for pre-weaning mortality and abortion rate had 13.5 %, and 12.5 %, respectively, which was statistically lower than the lowest quartiles for the same variables (10.5 %, and 10.6 %). Moreover, better sow farm health status was also associated with lower subsequent W2F mortality. A significant difference was detected in W2F mortality between epidemic versus negative groups for porcine reproductive and respiratory syndrome virus (15.4 % vs 8.7 %), and Mycoplasma hyopneumoniae epidemic versus negative groups (13.7 % vs 9.9 %). Overall, this study demonstrated the application of a whole-herd analysis by aggregating information of the pre-weaning phase with the post-weaning phase (breeding-to-market) to identify and measure the major risk factors of W2F mortality.

A case study of ventilation shutdown with the addition of high temperature and humidity for depopulation of pigs.

CASE DESCRIPTION: In February 2020, a swine farm operating in multiple states throughout the Midwest began to evaluate emergency plans to respond to potential impacts of the COVID-19 pandemic. CLINICAL FINDINGS: From February through April, extensive mitigation strategies were implemented in anticipation of market disruption. The farm consulted the AVMA Guidelines for the Depopulation of Animals to identify preferred methods for depopulation of swine; however, none of these methods were feasible. When the first US packing plant closed in April 2020 because of human COVID-19 infection, the farm began to evaluate whether ventilation shutdown plus (VSD+) could be used for depopulation. TREATMENT AND OUTCOME: Through proof-of-concept trials, a method for ventilation shutdown with the addition of supplemental temperature and humidity was developed. A single location with 4 barns that could be retrofitted for the process was selected, and between April and June 2020, 243,016 pigs were depopulated (59,478 nursery and 183,538 finishing pigs). Mean ± SD time to silent (the time when no sounds could be heard and no motion seen) was 55.4 ± 14.5 minutes for the nursery pigs and 65.0 ± 18.1 minutes for the finishing pigs. Only 728 (0.300%) pigs required manual euthanasia at the end of the depopulation process. CLINICAL RELEVANCE: Efficacy exceeded AVMA recommendations for the use of VSD+ (> 95% mortality rate in < 1 hour). Findings could potentially guide the use of this method for mass depopulation in the event of a foreign animal disease outbreak or severe market disruption in the future.

Methods for reproductive tract scoring as a tool for improving sow productivity.

Improving sow lifetime productivity is essential for maximizing farm profitability. Study objectives were to determine the accuracy for different vulva scoring methods in a commercial production system and to assess whether gilt reproductive tract scoring [evaluated by vulva width (VW)] prior to puberty could serve as useful gilt selection criteria. To accomplish this objective, 958 prepubertal replacement gilts in a commercial system were evaluated at approximately 15 wk of age. Gilt body weight (BW) was recorded in addition to 4 different methods to evaluate VW. Methods for VW assessment included digital caliper measurement (mm), visual evaluation and scoring by trained farm personnel [Farm Score (FS)], and 2 methods using scoring tools [Vulva Score Method A and B (VSA and VSB, respectively)] specifically calibrated from the VW distribution measured on gilts from previous studies. The VSA and FS methods assigned gilts to one of 3 categories (S, M, L, and 1, 2, 3, respectively) whereas VSB classified gilts vulvas using a 5-point scoring system (1 to 5). At 15 wk of age, a low proportion of variability in vulva size (27.8 ± 0.1 mm) could be explained by BW (62.2 ± 0.2 kg; R 2 = 0.05). All 3 scoring methods were effective in categorizing gilts based upon VW, as the measured VW size within methods differed by score (P < 0.01). The proportion of gilts achieving their first parity increased with score for VSA (64.7%, 73.2%, and 84.4%; P = 0.02), VSB (66.0%, 71.7%, 79.2%, 76.4%, and 84.2%; P = 0.02), and FS (67.2%, 75.0%, and 88.8%; P = 0.03), but VSA, VSB, and FS did not influence percentage of gilts achieving their second parity (P = 0.32, 0.29, and 0.30, respectively). Litter performance of gilts scored as M or L using VSA improved with an increased total born over 2 parities compared to those scored as S (23.96 vs. 26.38 pigs; P < 0.01) as well as born alive (21.13 vs. 23.05 pigs; P < 0.05). Results were similar for VSB, where scores 2 to 5 had greater total born (23.97 vs. 26.33 pigs; P < 0.01) and born alive (21.11 vs. 23.02 pigs; P < 0.05) through 2 parities compared to gilts scored 1. Using the FS method, total born pigs tended to be increased (P = 0.06) through 2 parities for gilts having a 2 or 3 vulva score compared to those scored as a 1. Collectively, assessing VW at approximately 15 wk of age may identify sows with improved productivity through 2 parities as breeding herd females.

At the Intersection of Industry, Academia, and Government: How Do We Facilitate Productive Precision Livestock Farming in Practice?

This commentary is a comprehensive synthesis of ideas generated from a workshop, hosted by Iowa State University, encompassing precision livestock farming (PLF) research and applications for industry-academia. The goal of this workshop was to demonstrate existing institution research and strategically propel further PLF development and industry adoption. Six key thematic areas were identified from participant discussion: sensors and algorithms, implementation, economic feasibility, data, rural and societal impacts, and education and training. These themes were used to focus discussion on identifying the new knowledge needed to drive implementation and examine current and future challenges of implementing PLF. At the convergence of industry and academia sits a unique opportunity to create mutually beneficial relationships that accomplish the individual needs of all parties. Productive PLF is currently hindered by numerous technical and non-technical challenges, but an increasing demand and optimistic outlook may result in rapid producer adoption. To foster harmonious partnerships among industry, academia, and government, a nexus at the intersection of multiple disciplines and basic/applied sciences is needed to thrust future success.

Mortality Patterns in a Commercial Wean-To Finish Swine Production System.

Modern commercial pig production is a complex process that requires successful producers to understand and resolve factors associated with perturbations in production. One important perturbation is inventory loss due to mortality. In this study, data on 60 lots of approximately 2000 weaned pigs (n = 115,213) from one commercial production system were collected through the wean-to-finish (WTF) cycle with the objective of establishing patterns of mortality, estimating differences in profit/loss among patterns of mortality, and identifying production practices associated with mortality patterns. Information provided by the production system included the number of pigs in each lot at the time of placement (beginning inventory), weaning weight, barn dimensions, number of dead pigs (NDP) daily, capacity placed (proportion pigs actually placed versus what had been planned to be placed) and average weight sold. Analysis of NDP revealed three mortality patterns (clusters I, II, III) composed of 6, 40, and 14 lots, respectively, that differed in the temporal onset and/or level of mortality. Average daily gain (ADG) and feed conversion ratio (FCR) were calculated by growth phase for each cluster. An economic model showed profit differences among clusters due to poor biological performance by clusters I and III in the late finishing phase. Cluster II (n = 40) had fewer dead pigs and the highest profit compared to clusters I (n = 6) and III (n = 14). Area per pig (stocking density) was the only factor associated with the differences in mortality patterns. Routine monitoring and the analysis of mortality patterns for associations with production and management factors can help swine producers improve biological performance and improve profit.

Dexamethasone treatment did not exacerbate Seneca Valley virus infection in nursery-age pigs.

BACKGROUND: Senecavirus A, commonly known as Seneca Valley virus (SVV), is a picornavirus that has been infrequently associated with porcine idiopathic vesicular disease (PIVD). In late 2014 there were multiple PIVD outbreaks in several states in Brazil and samples from those cases tested positive for SVV. Beginning in July of 2015, multiple cases of PIVD were reported in the United States in which a genetically similar SVV was also detected. These events suggested SVV could induce vesicular disease, which was recently demonstrated with contemporary US isolates that produced mild disease in pigs. It was hypothesized that stressful conditions may exacerbate the expression of clinical disease and the following experiment was performed. Two groups of 9-week-old pigs were given an intranasal SVV challenge with one group receiving an immunosuppressive dose of dexamethasone prior to challenge. After challenge animals were observed for the development of clinical signs and serum and swabs were collected to study viral shedding and antibody production. In addition, pigs were euthanized 2, 4, 6, 8, and 12 days post inoculation (dpi) to demonstrate tissue distribution of virus during acute infection. RESULTS: Vesicular disease was experimentally induced in both groups with the duration and magnitude of clinical signs similar between groups. During acute infection [0-14 days post infection (dpi)], SVV was detected by PCR in serum, nasal swabs, rectal swabs, various tissues, and in swabs from ruptured vesicles. From 15 to 30 dpi, virus was less consistently detected in nasal and rectal swabs, and absent from most serum samples. Virus neutralizing antibody was detected by 5 dpi and lasted until the end of the study. CONCLUSION: Treatment with an immunosuppressive dose of dexamethasone did not drastically alter the clinical disease course of SVV in experimentally infected nursery aged swine. A greater understanding of SVV pathogenesis and factors that could exacerbate disease can help the swine industry with control and prevention strategies directed against this virus.

The effect of chemical clarification of oral fluids on porcine epidemic diarrhea virus antibody responses.

Routine testing of breeding herd oral fluid (OF) samples for porcine epidemic diarrhea virus (PEDV) IgG and/or IgA is used to track levels of PEDV immunity over time. However, OFs contain particles of feed, feces, and inorganic material that detract from the quality of the sample. We clarified swine OF samples using lyophilized chitosan-based formulas (A-C) tested by PEDV IgG and IgA ELISAs. To evaluate both the immediate and residual effects of treatment on antibody detection, samples were tested immediately post-treatment, then stored at 4°C and retested at 2, 4, and 6 days post-treatment (DPT). Formulations were shown to effectively clarify samples. Statistical analysis comparing treated to untreated OF samples at 0 DPT found that neither chitosan nor Tween 20 affected the OF ELISA IgA and IgG sample-to-positive (S/P) ratio results ( p > 0.05). Furthermore, pairwise comparisons of 0 DPT to 2, 4, and 6 DPT results detected no significant differences ( p > 0.05) in IgA and IgG S/P ratios (i.e., treated OF samples were stable over time). Therefore, chitosan efficiently clarified OF specimens without affecting the results of the PEDV IgG and IgA antibody ELISAs.

Vesicular Disease in 9-Week-Old Pigs Experimentally Infected with Senecavirus A.

Senecavirus A has been infrequently associated with vesicular disease in swine since 1988. However, clinical disease has not been reproduced after experimental infection with this virus. We report vesicular disease in 9-week-old pigs after Sencavirus A infection by the intranasal route under experimental conditions.

Full-Length Genome Sequences of Senecavirus A from Recent Idiopathic Vesicular Disease Outbreaks in U.S. Swine.

Since July 2015, vesicular lesions affecting growing pigs and sows accompanied with neonatal mortality have been reported in multiple U.S. states. Senecavirus A has been consistently detected from these cases. The complete genome sequences of 3 recent U.S. Senecavirus A isolates were determined to further characterize this virus.