Postweaning mortality in commercial swine production II: review of infectious contributing factors

Development of a pig wean-quality score using machine-learning algorithms to characterize and classify groups with high mortality risk under field conditions

Mortality during the post-weaning phase is a critical indicator of swine production system performance, influenced by a complex interaction of multiple factors of the epidemiological triad. This study leveraged retrospective data from 1723 groups of pigs marketed within a US swine production system to develop a Wean-Quality Score (WQS) using machine learning techniques. The study evaluated three machine learning models, Random Forest, Support Vector Machine, and Gradient Boosting Machine, to classify groups having high or low 60-day mortality, where high mortality groups represented 25 % of the groups among the study population with the highest mortality values (n=431; 60-day mortality=9.98 %), and the remaining 75 % of the groups were of low mortality (n=1292; 60-day mortality=2.75 %). The best-performing model, Random Forest (RF), outperformed the other ML models in terms of accuracy (0.90), sensitivity (0.84), and specificity (0.92) metrics, and was then selected for further analysis, which consisted of creating the WQS and ranking the most important factors for classifying groups as high or low mortality. The most important factors ranked through the RF model to classify groups with high mortality were pre-weaning mortality, weaning age, average parity of litters in sow farms, and PRRS status. Additionally, stocking conditions such as stocking density and time to fill the barn were important predictors of high mortality. The WQS was developed and correlated (r = 0.74) with the actual 60-day mortality of the groups, offering a valuable tool for assessing post-weaning survivability in swine production systems before weaning. This study highlights the potential of machine learning and comprehensive data utilization to improve the assessment and management of weaned pig quality in commercial swine production, which producers can utilize to identify and intervene in groups, according to the WQS.

The Vehicle of Administration and Prandial State May Reduce the Spectrum of Oral Broad-Spectrum Antibiotics (Oxytetracycline, Fosfomycin and Amoxicillin) Administered to Piglets: A Pharmacokinetic/Pharmacodynamic Approach

The objective of this study was to assess the impact of the vehicle of administration and the prandial state of post weaning piglets on the indices of therapeutic efficacy for different broad-spectrum antibiotic/pathogen combinations. Pharmacokinetic data were retrieved from previous studies, in which we orally administered oxytetracycline (OTC), fosfomycin (FOS), or amoxicillin (AMX) according to the following treatments: dissolved in soft water to fasted or non-fasted piglets, dissolved in hard water to fasted or non-fasted piglets, and mixed with feed. Minimum inhibitory concentration (MIC) values for susceptible strains of bacteria causing swine diseases were obtained from the database of European Committee on Antimicrobial Susceptibility Testing (EUCAST) for each antibiotic. Pharmacokinetic/pharmacodynamic (PK/PD) indices of therapeutic efficacy-drug exposure over the dosing interval (fAUC/MIC) for OTC and FOS; time that free drug concentration remains above MIC (%fT>MIC) for AMX-were calculated for each antibiotic/pathogen combination under each treatment. After all OTC and in-feed FOS and AMX treatments, the indices of therapeutic efficacy were below the target value for all the study microorganisms. When FOS or AMX were delivered dissolved in soft or hard water, the indices were above the target value over which therapeutic efficacy would be expected for Escherichia coli treated with FOS and, Glaesserella parasuis, Pasteurella multocida, and Actinobacillus pleuropneumoniae treated with AMX. The prandial state of piglets showed no influence on the indices of therapeutic efficacy. Pharmacokinetic profiles of broad-spectrum antibiotics, specifically the ability to achieve target concentrations, may be largely reduced due to drug interactions with components present in feed or water resulting in a discrepancy with PK/PD principles of prudent and responsible use of antibiotics.

The prevalence of porcine gastric ulcer and Helicobacter suis in Taiwan

Gastric ulcer is a common disease affecting pigs worldwide, with a prevalence reported as high as 93%. The cause of porcine gastric ulcer is multifactorial, with Helicobacter suis (H. suis) being considered as the primary pathogenic factor. To date, prevalence of H. suis resulting in porcine gastric ulcer in Taiwan has not been investigated. In this study, we collected 360 pig stomachs from the slaughterhouses. In addition, stomach tissues from the 88 diseased pigs submitted for necropsy were divided into symptomatic and asymptomatic groups. Gastric lesions were scored, and polymerase chain reaction was used to determine the occurrence of gastric ulcer and the prevalence of H. suis. The positive rate of H. suis in the samples from slaughtered pigs was 49.7%, and both infection of H. suis and the presence of gastric lesions were prone to occur in autumn. The positive rates of H. suis infection in the symptomatic and asymptomatic groups were 59.1% and 31.8%, respectively. Moreover, the proportion of the samples with gastroesophageal ulcer in the symptomatic group was 68.2%, predominantly observed in growing pigs. The incidence of the samples from the slaughterhouses with gastroesophageal erosion to ulceration revealed a significant difference between H. suis -infected and H. suis -uninfected pigs; however, there is no significant difference in the samples of diseased pigs. In conclusion, H. suis infection was associated with gastric ulcer in slaughtered pigs, but it was not the primary cause of gastroesophageal ulcer in diseased pigs with clinical symptoms.

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.

Evaluation of a microencapsulated form of zinc oxide on weanling pig growth performance, fecal zinc excretion, and small intestinal morphology

A total of 300 pigs (DNA 200 × 400; initially 6.0 ± 0.08 kg body weight [BW]) were used in a 42-d study to evaluate a microencapsulated form of zinc oxide. At weaning, pigs were randomly allocated to pens, and pens were randomly assigned to dietary treatments with 5 pigs per pen and 12 pens per treatment. Dietary treatments were 1) negative control (CON; standard nursery diet containing 110 ppm Zn in the form of zinc sulfate from trace mineral premix); 2) control diet with 400 ppm added Zn from ZnO included in phases 1 and 2 (Low-ZnO); 3) control diet with 3,000 ppm added Zn from ZnO included in phase 1 and 2,000 ppm added Zn from ZnO included in phase 2 (High-ZnO); 4) control diet with 400 ppm added Zn from microencapsulated ZnO included in phases 1 and 2 (Low-MZnO; Vetagro S.p.A., Reggio Emilia, Italy); 5) control diet with 3,000 ppm added Zn from microencapsulated ZnO in phase 1 and 2,000 ppm added Zn from microencapsulated ZnO in phase 2 (high-MZnO; Vetagro S.p.A., Reggio Emilia, Italy). On days 10 and 28, fecal samples from 2 pigs per pen were collected for fecal Zn concentrations, and on day 28, 30 pigs (n = 6) were euthanized, and small intestinal tissues were collected to evaluate morphology. For the entire treatment period (days 0 to 28) there was no evidence of differences in average daily gain (ADG), average daily feed intake (ADFI), or G:F (P > 0.05). During the common phase 3 (days 28 to 42) pigs fed the negative control, High-MZnO, or Low-MZnO had improved (P < 0.0001) ADG and ADFI compared to pigs fed High- or Low-ZnO. For the entire experiment (days 0 to 42), pigs fed Low-ZnO or High-ZnO had reduced (P < 0.0001) ADG compared to those fed the negative control. A significant treatment × day interaction (P = 0.04) was observed for fecal Zn concentrations, where the level of Zn excreted in the feces was dependent on the sampling day in pigs fed a low level of ZnO or low level of microencapsulated ZnO. There was no evidence (P > 0.05) that small intestinal morphology differed significantly between treatments. In summary, feeding a microencapsulated form of ZnO did not alter piglet growth performance during the treatment period. Pigs fed a low level of ZnO or microencapsulated ZnO had reduced fecal Zn excretion by the end of the feeding period, but no significant impacts were observed on piglet small intestinal morphology.

Main Causes of Death in Piglets from Different Brazilian Nursery Farms Based on Clinical, Microbiological, and Pathological Aspects

Necropsies can reveal herd problems or comorbidities that can lead to management corrections, improvements in animal performance, and better decision making. Furthermore, the pattern and causes of mortality might differ when different systems are evaluated. The present study was conducted to establish the main causes of death in nursery pigs from different systems in Brazil, as well as the clinical, microbiological, and pathological aspects of these mortalities. Eighteen nurseries were analyzed (a total of 120,243 housed piglets), and 557 necropsies were performed. Streptococcus suis infection was the most prevalent cause of death (21.2%), followed by bacterial polyserositis (16.7%), chronic atrophic enteritis (13.5%), salmonellosis (8.8%), pneumonia (8.6%), and colibacillosis (6.1%). The increase in mortality rate in individual nurseries and, consequently, in the diagnoses was commonly associated with disease outbreaks. Infectious diseases constituted the largest portion of the diagnoses, making a great opportunity for improving production rates in herds. Moreover, the extensive range of observed diagnoses highlights the importance of conducting preliminary diagnostic investigations based on necropsy to determine the causes of death. This approach allows for the direction of complementary tests, which can diagnose agents with greater specificity. As a result, this allows for the implementation of more effective prevention and control strategies.

Susceptibility trends of swine respiratory pathogens from 2019 to 2022 to antimicrobials commonly used in Spain

BACKGROUND

Antimicrobial resistance is one of the most important health challenges in humans and animals. Antibiotic susceptibility determination is used to select the most suitable drug to treat animals according to its success probability following the European legislation in force for these drugs. We have studied the antibiotic susceptibility pattern (ASP) of Actinobacillus pleuropneumoniae (APP) and Pasteurella multocida (PM) isolates, collected during the period 2019-2022 in Spain. ASP was measured by determining minimum inhibitory concentration using standardized laboratory methods and its temporal trend was determined by logistic regression analysis of non-susceptible/susceptible isolates using clinical breakpoints.

RESULTS

It was not observed any significant temporal trends for susceptibility of Actinobacillus pleuropneumoniae to ceftiofur, florfenicol, sulfamethoxazole/trimethoprim, tulathromycin and tildipirosin during the study period (p > 0.05). Contrarily, a significant temporal trend (p < 0.05) was observed for quinolones (enrofloxacin and marbofloxacin), tetracyclines (doxycycline and oxyteracycline), amoxicillin, tiamulin and tilmicosin. On the other hand, it was not observed any significant temporal trends for susceptibility of Pasteurella multocida to quinolones (enrofloxacin and marbofloxacin), amoxicillin, ceftiofur, florfenicol and macrolides (tildipirosin, tulathromycin and tilmicosin) during the study period (p > 0.05). Contrarily, a significant temporal trend (p < 0.05) was observed for tetracyclines (oxyteracycline), tiamulin and sulfamethoxazole/trimethoprim.

CONCLUSIONS

In general terms, pig pathogens (APP and PM) involved in respiratory diseases analysed herein appeared to remain susceptible or tended to increase susceptibility to antimicrobials over the study period (2019-2022), but our data clearly showed a different pattern in the evolution of antimicrobial susceptibility for each combination of drug and microorganism. Our results highlight that the evolution of antimicrobial susceptibility must be studied in a case-by-case situation where generalization for drug families and bacteria is not possible even for bacteria located in the same ecological niche.

Efficacy of water application of a humic substance, butyric acid, vitamins C, D, and E and/or electrolytes on performance and mortality in health-challenged nursery pigs¹

Health challenges continue to be rampant in nursery pigs which has led to increased industry-wide mortality trends. Therefore, the objective of these three studies was to evaluate a water supplement (HV; HydraVantage, Kent Nutrition Group, Muscatine, IA) which is a proprietary blend of a humic substance, butyric acid, and vitamins C, D, and E, as well as an electrolyte blend on nursery pig performance and mortality. Experiment 1 consisted of 196 crossbred weanling pigs (7 pigs per pen with 14 pens per treatment) which were randomly allotted by BW to two treatments consisting of control (water for 33 d) or HV at 15 g/L of stock solution and proportioned through a medicator (1:128) for 11 d followed by water for 22 d. There were no performance differences. However, mortality was reduced (P < 0.01) from 6.12% for the control to 0.00% for HV. In experiment 2, there were 488 weanling pigs (6 to 10 pigs/pen with 14 pens per treatment) which were randomly allotted by BW to four treatments in a 34-d trial. Treatment 1 was control (water), and treatments 2 and 4 were HV at 15 g/L of stock solution for 11 and 34 d, respectively. Treatment 3 utilized HV at 15 g/L stock solution during days 0 to 11 with 7.5 g HV/L stock solution utilized during days 11 to 21 followed by water. No performance differences were observed among the four treatments. Mortality was 10.89%, 4.82%, 5.54%, and 7.26% for treatments 1 to 4, respectively, with treatment 1 having a higher mortality (P < 0.05) compared to treatments 2 to 4. In experiment 3, a 2 × 2 factorial study was conducted (7 pigs per pen with 14 pens per treatment) in which the treatments were: 1) water; 2) HV at 15 g/L stock solution for 34 d; 3) electrolytes at 241 g/L stock solution for 34 d; and 4) HV at 15 g/L of stock solution and electrolytes at 226 g/L of stock for 34 d. Overall pen gain tended to be improved (P = 0.09) with supplemental HV. Moreover, mortality was reduced (P = 0.06) by 36% (16.86% mortality for treatments 1 and 3 vs. 10.73% mortality for treatments 2 and 4). Supplemental electrolytes had no effect on mortality. These data suggest that HV has a positive effect by reducing mortality in nursery pigs undergoing health challenges.

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 Precision Livestock Technology and Human Scoring of Nursery Pigs in a Controlled Immune Challenge Experiment

The objectives were to determine the sensitivity, specificity, and cutoff values of a visual-based precision livestock technology (NUtrack), and determine the sensitivity and specificity of sickness score data collected with the live observation by trained human observers. At weaning, pigs (n = 192; gilts and barrows) were randomly assigned to one of twelve pens (16/pen) and treatments were randomly assigned to pens. Sham-pen pigs all received subcutaneous saline (3 mL). For LPS-pen pigs, all pigs received subcutaneous lipopolysaccharide (LPS; 300 μg/kg BW; E. coli O111:B4; in 3 mL of saline). For the last treatment, eight pigs were randomly assigned to receive LPS, and the other eight were sham (same methods as above; half-and-half pens). Human data from the day of the challenge presented high true positive and low false positive rates (88.5% sensitivity; 85.4% specificity; 0.871 Area Under Curve, AUC), however, these values declined when half-and-half pigs were scored (75% sensitivity; 65.5% specificity; 0.703 AUC). Precision technology measures had excellent AUC, sensitivity, and specificity for the first 72 h after treatment and AUC values were >0.970, regardless of pen treatment. These results indicate that precision technology has a greater potential for identifying pigs during a natural infectious disease event than trained professionals using timepoint sampling.

Antimicrobial Susceptibility Testing of Porcine Bacterial Pathogens: Investigating the Prospect of Testing a Representative Drug for Each Antimicrobial Family

Antimicrobial susceptibility testing is necessary to carry out antimicrobial stewardship but a limited number of drugs belonging to each antimicrobial family has to be tested for technical limitations and economic resources. In this study, we have determined the minimal inhibitory concentration, using microdilution following international standards (CLSI), for 490 Actinobacillus pleuropneumoniae, 285 Pasteurella multocida, 73 Bordetella bronchiseptica, 398 Streptococcus suis and 1571 Escherichia coli strains from clinical cases collected in Spain between 2018 and 2020. The antimicrobial susceptibility pattern was deciphered using a principal component analysis for each bacterium and a matrix correlation (high > 0.8, medium 0.5−0.8 and low < 0.5) was obtained for each pair of antimicrobials. No significant associations were observed between MIC patterns for different antimicrobial families, suggesting that co-selection mechanisms are not generally present in these porcine pathogens. However, a high correlation was observed between the fluroquinolones (marbofloxacin and enrofloxacin) for all mentioned pathogens and for ceftiofur and cefquinome for E. coli and S. suis. Moreover, a significant association was also observed for tetracyclines (doxycycline and oxytetracycline) and B. bronchiseptica and tildipirosin/tulathromycin for P. multocida. These results suggest that generally, a representative drug per antimicrobial class cannot be selected, however, for some drug−bug combinations, MIC values from one representative drug could be extrapolated to the whole antimicrobial family.

Genetic Diversity of Porcine Circovirus 2 in Wild Boar and Domestic Pigs in Ukraine

Porcine circovirus type 2 (PCV2) is responsible for a number of porcine circovirus-associated diseases (PCVAD) that can severely impact domestic pig herds. For a non-enveloped virus with a small genome (1.7 kb ssDNA), PCV2 is remarkably diverse, with eight genotypes (a–h). New genotypes of PCV2 can spread through the migration of wild boar, which are thought to infect domestic pigs and spread further through the domestic pig trade. Despite a large swine population, the diversity of PCV2 genotypes in Ukraine has been under-sampled, with few PCV2 genome sequences reported in the past decade. To gain a deeper understanding of PCV2 genotype diversity in Ukraine, samples of blood serum were collected from wild boars (n = 107) that were hunted in Ukraine during the November–December 2012 hunting season. We found 34/107 (31.8%) prevalence of PCV2 by diagnostic PCR. For domestic pigs, liver samples (n = 16) were collected from a commercial market near Kharkiv in 2019, of which 6 out of 16 (37%) samples were positive for PCV2. We sequenced the genotyping locus ORF2, a gene encoding the PCV2 viral capsid (Cap), for 11 wild boar and six domestic pig samples in Ukraine using an Oxford Nanopore MinION device. Of 17 samples with resolved genotypes, the PCV2 genotype b was the most common in wild boar samples (10 out of 11, 91%), while the domestic pigs were infected with genotypes b and d. We also detected genotype b/d and b/a co-infections in wild boars and domestic pigs, respectively, and for the first time in Ukraine we detected genotype f in a wild boar from Poltava. Building a maximum-likelihood phylogeny, we identified a sublineage of PCV2 genotype b infections in both wild and domestic swine, suggesting a possible epizootic cluster and an ecological interaction between wild boar and domestic pig populations in northeastern Ukraine.

Weaning Age and Its Effect on the Development of the Swine Gut Microbiome and Resistome

Piglets are often weaned between 19 and 22 days of age in North America, although in some swine operations this may occur at 14 days or less. Piglets are abruptly separated from their sow at weaning and are quickly transitioned from sow’s milk to a plant-based diet. The effect of weaning age on the long-term development of the pig gut microbiome is largely unknown. Here, pigs were weaned at either 14, 21, or 28 days of age, and fecal samples were collected 20 times from day 4 (neonatal) through marketing at day 140. The fecal microbiome was characterized using 16S rRNA gene and shotgun metagenomic sequencing. The fecal microbiome of all piglets shifted significantly 3 to 7 days postweaning, with an increase in microbial diversity. Several Prevotella spp. increased in relative abundance immediately after weaning, as did butyrate-producing species such as Butyricicoccus porcorum, Faecalibacterium prausnitzii, and Megasphaera elsdenii. Within 7 days of weaning, the gut microbiome of pigs weaned at 21 and 28 days of age resembled that of pigs weaned at 14 days. Resistance genes to most antimicrobial classes decreased in relative abundance postweaning, with the exception of those conferring resistance to tetracyclines and macrolides-lincosamides-streptogramin B. The relative abundance of microbial carbohydrate-active enzymes (CAZymes) changed significantly in the postweaning period, with an enrichment of CAZymes involved in degradation of plant-derived polysaccharides. These results demonstrate that the pig gut microbiome tends change in a predictable manner postweaning and that weaning age has only a temporary effect on this microbiome.

IMPORTANCE Piglets are abruptly separated from their sow at weaning and are quickly transitioned from sow’s milk to a plant-based diet. This is the most important period in commercial swine production, yet the effect of weaning age on the long-term development of the pig gut microbiome is largely unknown. Metagenomic sequencing allows for a higher-resolution assessment of the pig gut microbiome and enables characterization of the resistome. Here, we used metagenomic sequencing to identify bacterial species that were enriched postweaning and therefore may provide targets for future manipulation studies. In addition, functional profiling of the microbiome indicated that many carbohydrate and metabolic enzymes decrease in relative abundance after weaning. This study also highlights the challenges faced in reducing antimicrobial resistance in pigs, as genes conferring tetracycline and macrolide resistance remained relatively stable from 7 days of age through to market weight at 140 days despite no exposure to antimicrobials.

Simultaneous Infection With Porcine Reproductive and Respiratory Syndrome and Influenza Viruses Abrogates Clinical Protection Induced by Live Attenuated Porcine Reproductive and Respiratory Syndrome Vaccination

The porcine respiratory disease complex (PRDC) is responsible for significant economic losses in the pig industry worldwide. Porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza virus are major viral contributors to PRDC. Vaccines are cost-effective measures for controlling PRRS, however, their efficacy in the context of co-infections has been poorly investigated. In this study, we aimed to determine the effect of PRRSV-2 and swine influenza H3N2 virus co-infection on the efficacy of PRRSV modified live virus (MLV) vaccination, which is widely used in the field. Following simultaneous challenge with contemporary PRRSV-2 and H3N2 field isolates, we found that the protective effect of PRRS MLV vaccination on clinical disease and pathology was abrogated, although viral load was unaffected and antibody responses were enhanced. In contrast, co-infection in non-immunized animals reduced PRRSV-2 viremia and H3N2 virus load in the upper respiratory tract and potentiated T cell responses against both PRRSV-2 and H3N2 in the lung. Further analysis suggested that an upregulation of inhibitory cytokines gene expression in the lungs of vaccinated pigs may have influenced responses to H3N2 and PRRSV-2. These findings provide important insights into the effect of viral co-infections on PRRS vaccine efficacy that may help identify more effective vaccination strategies against PRDC in the field.

Resistant starch: Implications of dietary inclusion on gut health and growth in pigs: a review

Starch from cereal grains, pulse grains, and tubers is a major energy substrate in swine rations constituting up to 55% of the diet. In pigs, starch digestion is initiated by salivary and then pancreatic α-amylase, and has as final step the digestion of disaccharides by the brush-border enzymes in the small intestine that produce monosaccharides (glucose) for absorption. Resistant starch (RS) is the proportion of starch that escapes the enzymatic digestion and absorption in the small intestine. The undigested starch reaches the distal small intestine and hindgut for microbial fermentation, which produces short-chain fatty acids (SCFA) for absorption. SCFA in turn, influence microbial ecology and gut health of pigs. These fermentative metabolites exert their benefits on gut health through promoting growth and proliferation of enterocytes, maintenance of intestinal integrity and thus immunity, and modulation of the microbial community in part by suppressing the growth of pathogenic bacteria while selectively enhancing beneficial microbes. Thus, RS has the potential to confer prebiotic effects and may contribute to the improvement of intestinal health in pigs during the post-weaning period. Despite these benefits to the well-being of pigs, RS has a contradictory effect due to lower energetic efficiency of fermented vs. digested starch absorption products. The varying amount and type of RS interact differently with the digestion process along the gastrointestinal tract affecting its energy efficiency and host physiological responses including feed intake, energy metabolism, and feed efficiency. Results of research indicate that the use of RS as prebiotic may improve gut health and thereby, reduce the incidence of post-weaning diarrhea (PWD) and associated mortality. This review summarizes our current knowledge on the effects of RS on microbial ecology, gut health and growth performance in pigs.

Risk Factors for Antimicrobial Use on Irish Pig Farms

Simple Summary

Antimicrobial resistance (AMR) is a major threat to public health. There are concerns that antimicrobial use (AMU) in agriculture has a role in the development of AMR. Pigs are one of the main consumers of veterinary antimicrobials and a better understanding of the drivers for AMU in this sector will help in efforts to reduce use. The aim of this study was to investigate the associations between antimicrobial use, farm characteristics, biosecurity, the presence of respiratory disease on the farm and health management practices on Irish pig farms. Farms that manufactured their feed on-site had lower total AMU than farms that purchased their feed from a feed mill. Higher levels of lung abscesses and pericarditis (inflammation of the lining around the heart), both indicators of respiratory disease, were associated with increased AMU. Higher levels of pericarditis were also associated with increased use of critically important antimicrobials. Farms vaccinating against swine influenza also had higher AMU. Farms that administered prophylactic antimicrobial treatments to piglets had higher use of individual treatments and critically important antimicrobials. The results from this study show that prophylaxis and respiratory disease are the main drivers of AMU on Irish pig farms. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.

Abstract

The threat to public health posed by antimicrobial resistance in livestock production means that the pig sector is a particular focus for efforts to reduce antimicrobial use (AMU). This study sought to investigate the risk factors for AMU in Irish pig production. Antimicrobial use data were collected from 52 farrow-to-finish farms. The risk factors investigated were farm characteristics and performance, biosecurity practices, prevalence of pluck lesions at slaughter and serological status for four common respiratory pathogens and vaccination and prophylactic AMU practices. Linear regression models were used for quantitative AMU analysis and risk factors for specific AMU practices were investigated using logistic regression. Farms that milled their own feed had lower total AMU (p < 0.001), whereas higher finisher mortality (p = 0.043) and vaccinating for swine influenza (p < 0.001) increased AMU. Farms with higher prevalence of pericarditis (p = 0.037) and lung abscesses (p = 0.046) used more group treatments. Farms with higher prevalence of liver milk spot lesions (p = 0.018) and farms practising prophylactic AMU in piglets (p = 0.03) had higher numbers of individual treatments. Farms practising prophylactic AMU in piglets (p = 0.002) or sows (p = 0.062) had higher use of cephalosporins and fluoroquinolones. This study identified prophylactic use and respiratory disease as the main drivers for AMU in Irish pig production. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.

Statistical Modeling for the Prediction of Infectious Disease Dissemination With Special Reference to COVID-19 Spread

In this review, we have discussed the different statistical modeling and prediction techniques for various infectious diseases including the recent pandemic of COVID-19. The distribution fitting, time series modeling along with predictive monitoring approaches, and epidemiological modeling are illustrated. When the epidemiology data is sufficient to fit with the required sample size, the normal distribution in general or other theoretical distributions are fitted and the best-fitted distribution is chosen for the prediction of the spread of the disease. The infectious diseases develop over time and we have data on the single variable that is the number of infections that happened, therefore, time series models are fitted and the prediction is done based on the best-fitted model. Monitoring approaches may also be applied to time series models which could estimate the parameters more precisely. In epidemiological modeling, more biological parameters are incorporated in the models and the forecasting of the disease spread is carried out. We came up with, how to improve the existing modeling methods, the use of fuzzy variables, and detection of fraud in the available data. Ultimately, we have reviewed the results of recent statistical modeling efforts to predict the course of COVID-19 spread.

Using Nutritional Strategies to Shape the Gastro-Intestinal Tracts of Suckling and Weaned Piglets

This is a comprehensive review on the use of nutritional strategies to shape the functioning of the gastro-intestinal tract in suckling and weaned piglets. The progressive development of a piglet's gut and the associated microbiota and immune system offers a unique window of opportunity for supporting gut health through dietary modulation. This is particularly relevant for large litters, for which sow colostrum and milk are insufficient. The authors have therefore proposed the use of supplemental milk and creep feed with a dual purpose. In addition to providing nutrients to piglets, supplemental milk can also serve as a gut modulator in early life by incorporating functional ingredients with potential long-term benefits. To prepare piglets for weaning, it is important to stimulate the intake of solid feed before weaning, in addition to stimulating the number of piglets eating. The use of functional ingredients in creep feed and a transition diet around the time of weaning helps to habituate piglets to solid feed in general, while also preparing the gut for the digestion and fermentation of specific ingredients. In the first days after weaning (i.e., the acute phase), it is important to maintain high levels of feed intake and focus on nutritional strategies that support good gastric (barrier) function and that avoid overloading the impaired digestion and fermentation capacity of the piglets. In the subsequent maturation phase, the ratio of lysine to energy can be increased gradually in order to stimulate piglet growth. This is because the digestive and fermentation capacity of the piglets is more mature at this stage, thus allowing the inclusion of more fermentable fibres. Taken together, the nutritional strategies addressed in this review provide a structured approach to preparing piglets for success during weaning and the period that follows. The implementation of this approach and the insights to be developed through future research can help to achieve some of the most important goals in pig production: reducing piglet mortality, morbidity and antimicrobial use.

Indications and patterns of antimicrobial use in pig farms in the southern Kyushu, Japan: large amounts of tetracyclines used to treat respiratory disease in post-weaning and fattening pigs

In Japan, reducing the use of antimicrobials in pig production is a significant issue. However, there are no published reports concerning porcine disease treatment, as related to the age of the pigs and the indications (e.g., organ system) in Japan. In this study, we analyzed the prescription records of 17 farrow-to-finish farms from 2014 to 2018 in southern Kyushu, Japan. The farms’ antimicrobial usage was calculated as the active ingredient per population correction unit (PCU) or the number of treated pigs per PCU using the defined daily dose. All data were analyzed according to the indications and production stages (sows, suckling pigs, post-weaning pigs, and fattening pigs). In terms of active ingredients/PCU, tetracyclines were the most commonly used (43.2–59.3%), and the largest amounts of antimicrobials administered through feeds were for treating the respiratory organs of fattening pigs. In terms of the number of treated pigs/PCU, tetracyclines were most frequently used (16.3–31.1%), and a high frequency of antimicrobials administered through feeds was used for the treatment of respiratory organs in post-weaning pigs. In this study, it was confirmed that tetracyclines were used frequently as a herd treatment for respiratory diseases in post-weaning and fattening pigs in southern Kyushu, Japan. The findings suggest that it is necessary to improve the treatment and prevention of respiratory diseases in post-weaning and fattening pigs in order to reduce the frequencies of antimicrobial treatments.

Postweaning mortality in commercial swine production II: review of infectious contributing factors

Postweaning mortality is extremely complex with a multitude of noninfectious and infectious contributing factors. In the current review, our objective is to describe the current state of knowledge regarding infectious causes of postweaning mortality, focusing on estimates of frequency and magnitude of effect where available. While infectious mortality is often categorized by physiologic body system affected, we believe the complex multifactorial nature is better understood by an alternative stratification dependent on intervention type. This category method subjectively combines disease pathogenesis knowledge, epidemiology, and economic consequences. These intervention categories included depopulation of affected cohorts of animals, elimination protocols using knowledge of immunity and epidemiology, or less aggressive interventions. The most aggressive approach to control infectious etiologies is through herd depopulation and repopulation. Historically, these protocols were successful for Actinobacillus pleuropneumoniae and swine dysentery among others. Additionally, this aggressive measure likely would be used to minimize disease spread if either a foreign animal disease was introduced or pseudorabies virus was reintroduced into domestic swine populations. Elimination practices have been successful for Mycoplasma hyopneumoniae, porcine reproductive and respiratory syndrome virus, coronaviruses, including transmissible gastroenteritis virus, porcine epidemic diarrhea virus, and porcine deltacoronavirus, swine influenza virus, nondysentery Brachyspira spp., and others. Porcine circovirus type 2 can have a significant impact on morbidity and mortality; however, it is often adequately controlled through immunization. Many other infectious etiologies present in swine production have not elicited these aggressive control measures. This may be because less aggressive control measures, such as vaccination, management, and therapeutics, are effective, their impact on mortality or productivity is not great enough to warrant, or there is inadequate understanding to employ control procedures efficaciously and efficiently. Since there are many infectious agents and noninfectious contributors, emphasis should continue to be placed on those infectious agents with the greatest impact to minimize postweaning mortality.