The potential risk of infectious disease dissemination via artificial insemination in swine

Screening for atypical porcine pestivirus in Swedish boar semen used for artificial insemination and a characterisation of the seminal RNA microbiome including the virome

BACKGROUND

This study aimed to characterise the RNA microbiome, including the virome of extended semen from Swedish breeding boars, with particular focus on Atypical porcine pestivirus (APPV). This neurotropic virus, associated with congenital tremor type A-II in piglets, was recently demonstrated to induce the disease through insemination with semen from infected boars.

RESULTS

From 124 Artificial Insemination (AI) doses from Swedish breeding boars, APPV was detected in one dose in addition to a sparse seminal RNA virome, characterised by retroviruses, phages, and some fecal-associated contaminants. The detected seminal microbiome was large and characterized by Gram-negative bacteria from the phylum Proteobacteria, mainly consisting of apathogenic or opportunistic bacteria. The proportion of bacteria with a pathogenic potential was low, and no antimicrobial resistance genes (ARGs) were detected in the datasets.

CONCLUSION

Overall, the results indicate a good health status among Swedish breeding boars. The detection of APPV in semen raises the question of whether routine screening for APPV in breeding boars should be instigated.

Mice as an Animal Model for Japanese Encephalitis Virus Research: Mouse Susceptibility, Infection Route, and Viral Pathogenesis

Japanese encephalitis virus (JEV), a zoonotic flavivirus, is principally transmitted by hematophagous mosquitoes, continually between susceptible animals and incidentally from those animals to humans. For almost a century since its discovery, JEV was geographically confined to the Asia-Pacific region with recurrent sizable outbreaks involving wildlife, livestock, and people. However, over the past decade, it has been detected for the first time in Europe (Italy) and Africa (Angola) but has yet to cause any recognizable outbreaks in humans. JEV infection leads to a broad spectrum of clinical outcomes, ranging from asymptomatic conditions to self-limiting febrile illnesses to life-threatening neurological complications, particularly Japanese encephalitis (JE). No clinically proven antiviral drugs are available to treat the development and progression of JE. There are, however, several live and killed vaccines that have been commercialized to prevent the infection and transmission of JEV, yet this virus remains the main cause of acute encephalitis syndrome with high morbidity and mortality among children in the endemic regions. Therefore, significant research efforts have been directed toward understanding the neuropathogenesis of JE to facilitate the development of effective treatments for the disease. Thus far, multiple laboratory animal models have been established for the study of JEV infection. In this review, we focus on mice, the most extensively used animal model for JEV research, and summarize the major findings on mouse susceptibility, infection route, and viral pathogenesis reported in the past and present, and discuss some unanswered key questions for future studies.

Antimicrobially Active Semen Extenders Allow the Reduction of Antibiotic Use in Pig Insemination

Antibiotic use in semen extenders for livestock may contribute to the development and spreading of multi-drug resistance. Antimicrobial control in semen doses for artificial insemination of pigs is indispensable due to the relatively high storage temperature (17 °C). The objectives of this study were first, to examine whether the antimicrobial capacity differs between antibiotic-free extenders and second, to determine whether an antimicrobial active extender provides the possibility to reduce antibiotics. Antibiotic-free semen extenders Beltsville Thawing Solution (BTS) and Androstar Premium were inoculated at 10³ to 10⁴ CFU/mL with four pure bacterial strains isolated from boar ejaculates or a mixture thereof, and then stored for 144 h at 17 °C. Bacterial counts after aerobic culture decreased in BTS up to one log level and decreased in Androstar Premium by 2 to 3.5 log levels (p < 0.05). In semen samples from nine boars stored in the inoculated Androstar Premium extender containing half of the standard concentration of gentamicin, bacteria counts were below 10¹ CFU/mL. Likewise, half of the standard dose of apramycin and ampicillin was fully antimicrobially active and sperm quality was maintained. In conclusion, semen extenders with intrinsic antimicrobial activity allow a reduction in antibiotic use in pig insemination.

Relevance of Leptospira in boar and for the development of alternative antimicrobial concepts in boar semen preservation

Leptospirosis is a zoonotic disease of importance to public health and in livestock productions. It causes significant economic losses in pig breeding farms worldwide. However, actual transmission cycles and disease epidemiology in the pig population remain largely unknown. Despite the fact that the potential risk of venereal transmission of pathogenic Leptospira serovars in pigs has been a topic of discussion since the 1970s, reliable data are still lacking compared to other livestock species. Consequently, antibiotics are added to semen extenders to reduce bacterial contamination including pathogens like Leptospira. In view of the global threat of antimicrobial resistances, the routine use of antibiotics in porcine semen extenders is now under debate. Information about the prevalence of Leptospira infections in boar used for artificial insemination is needed for the development of novel antimicrobial concepts in pig insemination.

This short report provides a summary of the state of knowledge, together with negative results from real-time PCR analyses for the detection of pathogenic Leptospira DNA in boar semen. Molecular analyses were performed on 96 raw and extended samples obtained from normospermic ejaculates of 58 boar housed in six different studs in Germany. In the absence of reliable data, it is important to raise the awareness for a subject that can represent a challenge for pig productions in keeping reproductive health and food safety at high levels. The present molecular results indicate that Leptospira might not be a common threat in boar semen. Conclusive evidence would require results from a systematic serological surveillance of boar, combined with seasonal molecular analyses of semen to identify potential carriers, and assess actual seroprevalences, associated Leptospira serovars and transmission events.

Sperm function in vitro and fertility after antibiotic-free, hypothermic storage of liquid preserved boar semen

The role of antibiotics (AB) in semen extenders as a potential contribution to the global antimicrobial resistance threat is emerging. Here, we establish an AB-free hypothermic preservation strategy for boar semen and investigate its impact on sperm function, microbial load and fertility after artificial insemination (AI). Spermatozoa (12 boars) preserved in AB-free AndroStar Premium extender at 5 °C maintained high motility, membrane integrity, and a low DNA-fragmentation index throughout 72 h storage and results did not significantly differ from controls stored at 17 °C in extender containing AB (p = 0.072). Likewise, kinetic response of spermatoza to the capacitation stimulus bicarbonate during 180 min incubation in Tyrode's medium did not differ from 17 °C-controls. In a competitive sperm oviduct binding assay, binding indices did not differ between semen stored for 72 h AB-free at 5 °C and 17 °C-controls (n = 6 boars). Bacterial load < 103 CFU/ml after 72 h was measured in 88.9% of samples stored at 5 °C AB-free compared to 97.2% in 17 °C-controls (n = 36 semen pools, 23 boars). Fertility traits of 817 females did not differ significantly between the two semen groups (p > 0.05). In conclusion, a hypothermic semen preservation strategy is presented which offers antibiotic-free storage of boar semen doses.

Application of preserved boar semen for artificial insemination: Past, present and future challenges

Artificial insemination (AI) is now used for breeding more than 90% of the sows in most of the world's primary pork producing countries. Despite the advancement of methods to cryopreserve boar semen, frozen semen has not been routinely used on farms because of limited efficiency. Liquid semen on the other hand, with 1.5-3 billion sperm per dose preserved up to seven days in long-term extenders, is in common use and is largely responsible for the widespread use of AI. Breeding organizations have defined individual thresholds for useable semen at 60-80% for motility and bacterial load of 0-1000 CFU/mL. Improvement in preservation techniques for liquid semen and better education of producers has been responsible for the higher efficiency of pig breeding, as measured by conception rate and increased litter size, with a minimum number of sperm. The introduction of deep intrauterine AI and advances in breeding management have also been contributing factors. The present article reviews the worldwide application of preserved boar semen from past to present and delineates future challenges. Pathways to increase breeding efficiency are outlined. The reconciliation of AI with sustainable breeding strategies is increasingly important. In this sense, guidelines for the prudent use of antibiotics in semen extenders are proposed. More efficient and sustainable pig AI awaits the introduction of sex-sorted sperm into AI practice. Another critical milestone that needs to be achieved is the replacement of conventional antibiotics in extenders.

Lycium barbarum and Laminaria japonica polysaccharides improve Cashmere goat sperm quality and fertility rate after cryopreservation

Cashmere goat is known for the highest cashmere yield and best fiber quality. Here, the effects of Lycium barbarum polysaccharide (LBP) and Laminaria japonica polysaccharide (LJP) on goat sperm quality were investigated. Results showed that the sperm motility, mitochondrial activity, and membrane and acrosome integrity were significantly higher with 4.0 mg/mL LBP and 1.0 mg/mL LJP supplementations than in the control (P < 0.05), respectively. Higher SOD, CAT, and GSH-Px levels were observed in 4.0 mg/mL LBP and 1.0 mg/mL LJP groups than control group (P < 0.05). Sperm characteristics with 2.0 + 1.0 mg/mL LBP + LJP supplementation significantly improved compared to that with other treatments (P < 0.05). Compared to the control treatment, the non-return rate (NRR) were higher in the LBP + LJP (2.0 + 1.0 mg/mL) group (P < 0.05). These results suggest that LBP and LJP enhance cryo-protective effects on goat spermatozoa, and that 2.0 + 1.0 mg/mL LBP + LJP addition to the extender during cryopreservation is beneficial to the Cashmere goat breeding industry.

Detection and characterization of Lactobacillus spp. in the porcine seminal plasma and their influence on boar semen quality

The presence of pathogenic bacteria in ejaculates has been a topic in boar semen preservation over the last decades. Since little information is available on commensal bacteria in boar semen, the aim of the present study was to identify commensal lactobacilli in fresh cryopreserved boar semen and to examine their influence on boar semen quality. Therefore, 111 boar ejaculates were investigated for the presence of Lactobacillus species. Thirty samples (27%) contained viable Lactobacillus species (e.g. L. amylovorus, L. animalis, L. reuteri and Weisella minor). L. animalis and L. buchneri DSM 32407 (isolated from the bovine uterus) qualified for further examinations based on their growth rate in six antibiotic-free boar semen extenders. After a 120 min short-term incubation with an antibiotic-free BTS-extender, progressive motility was diminished (P = 0.001) upon addition of 105 and 106 colony forming units (CFU/mL) L. animalis. The supplementation with L. buchneri DSM 32407 had no significant (P > 0.05) influence on sperm quality during short-term co-incubation. After 168 h long-term co-incubation, motility analysis revealed a negative (P = 0.026) impact of 105 CFU/mL L. buchneri DSM 32407. A concentration- and storage-dependent effect is particularly obvious (P < 0.001) using 106 CFU/mL L. buchneri DSM 32407. Most notably, the thermo-resistance (TRT) for 106 CFU/mL L. buchneri DSM 32407 (P = 0.001) was inferior to BTS with and without gentamicin after 72 and 168 h of semen co-incubation. The supplementation of 105 CFU/mL L. buchneri DSM 32407 impaired progressive motility to a lesser extent. The percentage of mitochondrially active spermatozoa after 96 h (P = 0.009) and membrane-intact spermatozoa after 168 h (P < 0.001) was lower when 106 CFU/mL L. buchneri DSM 32407 were suspended compared with all other groups. Finally, the addition of L. buchneri DSM 32407 to BTS-extended boar semen had no competitive effect on the total amount of bacteria 48 h after co-incubation. In summary, the present study demonstrated that there are Lactobacillus species present in the porcine seminal plasma, which can be cultivated using standard procedures. However, long-term co-incubation of lactic acid bacteria with spermatozoa had a negative influence on spermatozoa.

Sexual transmission of Zika virus and other flaviviruses: A living systematic review

BACKGROUND

Health authorities in the United States and Europe reported an increasing number of travel-associated episodes of sexual transmission of Zika virus (ZIKV) following the 2015-2017 ZIKV outbreak. This, and other scientific evidence, suggests that ZIKV is sexually transmissible in addition to having its primary mosquito-borne route. The objective of this systematic review and evidence synthesis was to clarify the epidemiology of sexually transmitted ZIKV.

METHODS AND FINDINGS

We performed a living (i.e., continually updated) systematic review of evidence published up to 15 April 2018 about sexual transmission of ZIKV and other arthropod-borne flaviviruses in humans and other animals. We defined 7 key elements of ZIKV sexual transmission for which we extracted data: (1) rectal and vaginal susceptibility to infection, (2) incubation period following sexual transmission, (3) serial interval between the onset of symptoms in a primary and secondary infected individuals, (4) duration of infectiousness, (5) reproduction number, (6) probability of transmission per sex act, and (7) transmission rate. We identified 1,227 unique publications and included 128, of which 77 presented data on humans and 51 presented data on animals. Laboratory experiments confirm that rectal and vaginal mucosae are susceptible to infection with ZIKV and that the testis serves as a reservoir for the virus in animal models. Sexual transmission was reported in 36 human couples: 34/36 of these involved male-to-female sexual transmission. The median serial symptom onset interval in 15 couples was 12 days (interquartile range: 10-14.5); the maximum was 44 days. We found evidence from 2 prospective cohorts that ZIKV RNA is present in human semen with a median duration of 34 days (95% CI: 28-41 days) and 35 days (no CI given) (low certainty of evidence, according to GRADE). Aggregated data about detection of ZIKV RNA from 37 case reports and case series indicate a median duration of detection of ZIKV of 40 days (95% CI: 30-49 days) and maximum duration of 370 days in semen. In human vaginal fluid, median duration was 14 days (95% CI: 7-20 days) and maximum duration was 37 days (very low certainty). Infectious virus in human semen was detected for a median duration of 12 days (95% CI: 1-21 days) and maximum of 69 days. Modelling studies indicate that the reproduction number is below 1 (very low certainty). Evidence was lacking to estimate the incubation period or the transmission rate. Evidence on sexual transmission of other flaviviruses was scarce. The certainty of the evidence is limited because of uncontrolled residual bias.

CONCLUSIONS

The living systematic review and sexual transmission framework allowed us to assess evidence about the risk of sexual transmission of ZIKV. ZIKV is more likely transmitted from men to women than from women to men. For other flaviviruses, evidence of sexual transmissibility is still absent. Taking into account all available data about the duration of detection of ZIKV in culture and from the serial interval, our findings suggest that the infectious period for sexual transmission of ZIKV is shorter than estimates from the earliest post-outbreak studies, which were based on reverse transcription PCR alone.

Review of transmission routes of 24 infectious diseases preventable by biosecurity measures and comparison of the implementation of these measures in pig herds in six European countries

This study aimed to review the transmission routes of important infectious pig diseases and to translate these into biosecurity measures preventing or reducing the transmission between and within pig herds. Furthermore, it aimed to identify the level of implementation of these measures in different European countries and discuss the observed variations to identify potentials for improvement. First, a literature review was performed to show which direct and indirect transmission routes of 24 infectious pig diseases can be prevented through different biosecurity measures. Second, a quantitative analysis was performed using the Biocheck.UGent™, a risk-based scoring system to evaluate biosecurity in pig herds, to obtain an insight into the implementation of these biosecurity measures. The database contained farm-specific biosecurity data from 574 pig farms in Belgium, Denmark, France, Germany, the Netherlands and Sweden, entered between January 2014 and January 2016. Third, a qualitative analysis based on a review of literature and other relevant information resources was performed for every subcategory of internal and external biosecurity in the Biocheck.UGent™ questionnaire. The quantitative analysis indicated that at the level of internal, external and overall biosecurity, Denmark had a significantly distinct profile with higher external biosecurity scores and less variation than the rest of the countries. This is likely due to a widely used specific pathogen-free (SPF) system with extensive focus on biosecurity since 1971 in Denmark. However, the observed pattern may also be attributed to differences in data collection methods. The qualitative analysis identified differences in applied policies, legislation, disease status, pig farm density, farming culture and habits between countries that can be used for shaping country-specific biosecurity advice to attain improved prevention and control of important pig diseases in European pig farms.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): porcine reproductive and respiratory syndrome (PRRS)

Porcine reproductive and respiratory syndrome (PRRS) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of PRRS to be listed, Article 9 for the categorisation of PRRS according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to PRRS. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, PRRS can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The animal species to be listed for PRRS according to Article 8(3) criteria are domestic pigs and wild boar.

Can Microfiltered Seminal Plasma Preserve the Morphofunctional Characteristics of Porcine Spermatozoa in the Absence of Antibiotics? A Preliminary Study

Artificial insemination is extensively performed in pig farms in Europe, the United States and Canada. Antibiotics are typically added to the inseminating dose to limit bacterial growth during liquid phase storage at 16°C, as bacterial contamination is unavoidable. The World Organization for Animal Health (OIE) and the Food and Agriculture Organization (FAO) take action to control and reduce antibiotic use in animals as more bacteria are becoming resistant to antimicrobials. To avoid the use of antibiotics, we prepared inseminating doses using microfiltered seminal plasma (SP). Microfiltration is a common technology used to reduce bacterial contamination but may retain seminal substances, influencing sperm quality during storage. Therefore, the aim of this study was to evaluate the morphofunctional parameters of spermatozoa during storage at 16°C in doses prepared with or without microfiltered SP, with or without the addition of antibiotics, in a Latin square design. Artificial insemination doses with microfiltered SP and without antibiotic addition preserved spermatozoa viability, mitochondrial membrane potential, acrosome integrity and objective motility, with absolute values equal or even better than those observed in conventional doses. In conclusion, although the results could be considered preliminary due to the small sample size, this study suggests that microfiltration of SP can be a simple method, feasible on farms, to replace antibiotic use in extended doses stored in the liquid phase at 16°C for up to 7 days.

Extended semen for artificial insemination in swine as a potential transmission mechanism for infectious Chlamydia suis

Although typically unnoticed, Chlamydia infections in swine have been shown to be both widespread and may impact production characteristics and reproductive performance in swine. Serum titers suggest Chlamydia infection within boar studs is common, and infected boars are known to shed chlamydia in their ejaculates. Although the transmission of viruses in chilled extended semen (ES) is well established, the inclusion of antibiotics in commercially available extender is generally believed to limit or preclude the transmission of infectious bacteria. The objective of this study was to evaluate the potential of ES used in artificial insemination to support transmission of the obligate intracellular bacteria Chlamydia suis (C suis) under standard industry conditions. First, the effect of C suis on sperm quality during storage was assessed by flow cytometry. Only concentrations above 5 × 10(5) viable C suis/mL caused significant spermicidal effects which only became evident after 7 days of storage at 17 °C. No significant effect on acrosome reaction was observed using any chlamydial concentration. Next, an in vitro infection model of swine testicular fibroblast cells was established and used to evaluate the effect of chilled storage on C suis viability under variable conditions. Storage in Androhep ES reduced viability by 34.4% at a multiplicity of infection of 1.25, an effect which increased to 53.3% when the multiplicity of infection decreased to 0.1. Interestingly, storage in semen extender alone (SE) or ES with additional antibiotics had no effect on bacterial viability. To rule out a secondary effect on extender resulting from metabolically active sperm, C suis was stored in fresh and expended SE and again no significant effect on bacterial viability was observed. Fluorescent microscopy of C suis in ES shows an association between bacteria and the remaining gel fraction after storage suggesting that the apparent reduction of bacterial viability in the presence of semen is due to adherence to gel fraction. Taken together, the results of this study suggest that C suis remains viable and infectious during chilled storage and is globally unaffected by antibiotics in extender. Thus, ES used in artificial insemination may act as a viable transmission mechanism for C suis in swine.

Network, cluster and risk factor analyses for porcine reproductive and respiratory syndrome using data from swine sites participating in a disease control program

The objectives of this study were to describe networks of Ontario swine sites and their service providers (including trucking, feed, semen, gilt and boar companies); to categorize swine sites into clusters based on site-level centrality measures, and to investigate risk factors for porcine reproductive and respiratory syndrome (PRRS) using information gathered from the above-mentioned analyses. All 816 sites included in the current study were enrolled in the PRRS area regional control and elimination projects in Ontario. Demographics, biosecurity and network data were collected using a standardized questionnaire and PRRS status was determined on the basis of available diagnostic tests and assessment by site veterinarians. Two-mode networks were transformed into one-mode dichotomized networks. Cluster and risk factor analyses were conducted separately for breeding and growing pig sites. In addition to the clusters obtained from cluster analyses, other explanatory variables of interest included: production type, type of animal flow, use of a shower facility, and number of neighboring swine sites within 3km. Unadjusted univariable analyses were followed by two types of adjusted models (adjusted for production systems): a generalizing estimation equation model (GEE) and a generalized linear mixed model (GLMM). Results showed that the gilt network was the most fragmented network, followed by the boar and truck networks. Considering all networks simultaneously, approximately 94% of all swine sites were indirectly connected. Unadjusted risk factor analyses showed significant associations between almost all predictors of interest and PRRS positivity, but these disappeared once production system was taken into consideration. Finally, the vast majority of the variation on PRRS status was explained by production system according to GLMM, which shows the highly correlated nature of the data, and raises the point that interventions at this level could potentially have high impact in PRRS status change and/or maintenance.

Liquid storage of boar semen: Current and future perspectives on the use of cationic antimicrobial peptides to replace antibiotics in semen extenders

Antibiotics are of great importance in boar semen extenders to ensure long shelf life of spermatozoa and to reduce transmission of pathogens into the female tract. However, the use of antibiotics carries a risk of developing resistant bacterial strains in artificial insemination laboratories and their spread via artificial insemination. Development of multiresistant bacteria is a major concern if mixtures of antibiotics are used in semen extenders. Minimal contamination prevention techniques and surveillance of critical hygiene control points proved to be efficient in reducing bacterial load and preventing development of antibiotic resistance. Nevertheless, novel antimicrobial concepts are necessary for efficient bacterial control in extended boar semen with a minimum risk of evoking antibiotic resistance. Enhanced efforts have been made in recent years in the design and use of antimicrobial peptides (AMPs) as alternatives to conventional antibiotics. The male genital tract harbors a series of endogenic substances with antimicrobial activity and additional functions relevant to the fertilization process. However, exogenic AMPs often exert dose- and time-dependent toxic effects on mammalian spermatozoa. Therefore, it is important that potential newly designed AMPs have only minor impacts on eukaryotic cells. Recently, synthetic magainin derivatives and cyclic hexapeptides were tested for their application in boar semen preservation. Bacterial selectivity, proteolytic stability, thermodynamic resistance, and potential synergistic interaction with conventional antibiotics propel predominantly cyclic hexapeptides into highly promising, leading candidates for further development in semen preservation. The time scale for the development of resistant pathogens cannot be predicted at this moment.

Artificial insemination in pigs today

Use of artificial insemination (AI) for breeding pigs has been instrumental for facilitating global improvements in fertility, genetics, labor, and herd health. The establishment of AI centers for management of boars and production of semen has allowed for selection of boars for fertility and sperm production using in vitro and in vivo measures. Today, boars can be managed for production of 20 to 40 traditional AI doses containing 2.5 to 3.0 billion motile sperm in 75 to 100 mL of extender or 40 to 60 doses with 1.5 to 2.0 billion sperm in similar or reduced volumes for use in cervical or intrauterine AI. Regardless of the sperm dose, in liquid form, extenders are designed to sustain sperm fertility for 3 to 7 days. On farm, AI is the predominant form for commercial sow breeding and relies on manual detection of estrus with sows receiving two cervical or two intrauterine inseminations of the traditional or low sperm doses on each day detected in standing estrus. New approaches for increasing rates of genetic improvement through use of AI are aimed at methods to continue to lower the number of sperm in an AI dose and reducing the number of inseminations through use of a single, fixed-time AI after ovulation induction. Both approaches allow greater selection pressure for economically important swine traits in the sires and help extend the genetic advantages through AI on to more production farms.

Cationic synthetic peptides: assessment of their antimicrobial potency in liquid preserved boar semen

Various semen extender formulas are in use to maintain sperm longevity and quality whilst acting against bacterial contamination in liquid sperm preservation. Aminoglycosides are commonly supplemented to aid in the control of bacteria. As bacterial resistance is increasing worldwide, antimicrobial peptides (AMPs) received lively interest as alternatives to overcome multi-drug resistant bacteria. We investigated, whether synthetic cationic AMPs might be a suitable alternative for conventional antibiotics in liquid boar sperm preservation. The antibacterial activity of two cyclic AMPs (c-WWW, c-WFW) and a helical magainin II amide analog (MK5E) was studied in vitro against two Gram-positive and eleven Gram-negative bacteria. Isolates included ATCC reference strains, multi-resistant E. coli and bacteria cultured from boar semen. Using broth microdilution, minimum inhibitory concentrations were determined for all AMPs. All AMPs revealed activity towards the majority of bacteria but not against Proteus spp. (all AMPs) and Staphylococcus aureus ATCC 29213 (MK5E). We could also demonstrate that c-WWW and c-WFW were effective against bacterial growth in liquid preserved boar semen in situ, especially when combined with a small amount of gentamicin. Our results suggest that albeit not offering a complete alternative to traditional antibiotics, the use of AMPs offers a promising solution to decrease the use of conventional antibiotics and thereby limit the selection of multi-resistant strains.

Effects of Enterobacter cloacae on boar sperm quality during liquid storage at 17°C

Contamination of fresh and extended boar sperm often occurs in farms and artificial insemination (AI) centres during semen collection, processing and storage. The presence of bacteria produces detrimental effects on boar sperm quality, which may cause economic losses in reproductive centres. The present study has evaluated for the first time how the presence of Enterobacter cloacae affects the preservation of boar spermatozoa in liquid storage at 15-17 °C for an 11-day period. With this purpose, extended semen samples from seven healthy post-pubertal boars were artificially contaminated with different sperm:bacterium ratios (2:1; 1:1; 1:5 and 1:10) of E. cloacae. The 1:0 ratio (non-inoculated) served as a negative control. The most infective ratios (i.e. 1:5 and 1:10) significantly damaged sperm motility and membrane integrity, increased sperm agglutination, and decreased the osmotic resistance of spermatozoa. In contrast, the negative impact that the lowest bacterial concentration (2:1) had on boar sperm quality was clearly lower. In addition, other parameters such as pH were also more affected at the highest infective ratios (i.e. 1:5 and 1:10), despite no damage being observed on sperm morphology. In conclusion, the present work shows that damage inflicted by the presence of E. cloacae in boar sperm during liquid storage at 15-17 °C compromises the longevity and fertilising ability of seminal doses when bacterial concentration is higher than a 1:1 ratio. Further research is warranted to address by which mechanism E. cloacae impairs boar sperm quality.

Impact of swine reproductive technologies on pig and global food production

Reproductive technologies have dramatically changed the way pigs are raised for pork production in developed and developing countries. This has involved such areas as pigs produced/sow, more consistent pig flow to market, pig growth rate and feed efficiency, carcass yield and quality, labor efficiency, and pig health. Some reproductive technologies are in widespread use for commercial pork operations [Riesenbeck, Reprod Domest Anim 46:1-3, 2011] while others are in limited use in specific segments of the industry [Knox, Reprod Domest Anim 46:4-6, 2011]. Significant changes in the efficiency of pork production have occurred as a direct result of the use of reproductive technologies that were intended to improve the transfer of genes important for food production [Gerrits et al., Theriogenology 63:283-299, 2005]. While some technologies focused on the efficiency of gene transfer, others addressed fertility and labor issues. Among livestock species, pig reproductive efficiency appears to have achieved exceptionally high rates of performance (PigCHAMP 2011) [Benchmark 2011, Ames, IA, 12-16]. From the maternal side, this includes pigs born per litter, farrowing rate, as well as litters per sow per year. On the male side, boar fertility, sperm production, and sows served per sire have improved as well [Knox et al., Theriogenology, 70:1202-1208, 2008]. These shifts in the efficiency of swine fertility have resulted in the modern pig as one of the most efficient livestock species for global food production. These reproductive changes have predominantly occurred in developed countries, but data suggests transfer and adoption of these in developing countries as well (FAO STAT 2009; FAS 2006) [World pig meat production: food and agriculture organization of the United Nations, 2009; FAS, 2006) Worldwide Pork Production, 2006]. Technological advancements in swine reproduction have had profound effects on industry structure, production, efficiency, quality, and profitability. In all cases, the adoption of these technologies has aided in the creation of a sustainable supply of safe and affordable pork for consumers around the world [den Hartog, Adv Pork Prod 15:17-24, 2004].

How do different concentrations of Clostridium perfringens affect the quality of extended boar spermatozoa?

Bacteriospermia in boar fresh and extended semen is a frequent finding that produces alterations on sperm quality and, consequently, causes economic losses in artificial insemination (AI) centres. The present study sought to evaluate the effect of different infective concentrations of Clostridium perfringens on boar sperm quality, assessed as sperm motility (CASA), morphology and viability, through 11 days of storage at 15°C (experiment 1), and after 96h of incubation at 37°C (experiment 2). With this purpose, different seminal doses were artificially inoculated with different infective concentrations of C. perfringens, ranging from 10(2) to 10(8)cfumL(-1). The negative controls were non-inoculated doses. Sperm quality was checked after 0, 1, 2, 3, 4, 7, 8, 9, 10 and 11 days of storage at 15°C in experiment 1, and after 0, 24, 48, 72 and 96h at 37°C in the second experiment. Moreover, the presence/absence of bacteria was detected by PCR analyses during both experiments at different time points. In both experiments, sperm morphology of inoculated samples did not differ from the negative control. Conversely, detrimental effects on sperm viability and motility were observed after 24h of incubation/storage at the highest infective concentrations in both experiments. The deleterious effects observed because of the presence of C. perfringens in semen emphasise the relevance of detecting bacteria in extended doses destined to AI. So, this study suggests that the evaluation of bacterial contamination in semen is a procedure that should be routinely applied while assessing sperm quality in AI centres to avoid the use of doses with low sperm quality and the possible spread of bacterial contaminants.