Continuous feeding of antimicrobial growth promoters to commercial swine during the growing/finishing phase does not modify faecal community erythromycin resistance or community structure

Aims: To investigate the effect of continuous feeding of antimicrobial growth promoters (tylosin or virginiamycin) on the swine faecal community. Methods and Results: The study consisted of two separate on‐farm feeding trials. Swine were fed rations containing tylosin (44 or 88 mg kg^?1 of feed) or virginiamycin (11 or 22 mg kg^?1 of feed) continuously over the growing/finishing phases. The temporal impact of continuous antimicrobial feeding on the faecal community was assessed and compared to nondosed control animals through anaerobic cultivation, the analysis of community 16S rRNA gene libraries and faecal volatile fatty acid content. Feeding either antimicrobial had no detectable effect on the faecal community. Conclusions: Erythromycin methylase genes encoding resistance to the macrolide–lincosamide–streptogramin B (MLS_B) antimicrobials are present at a high level within the faecal community of intensively raised swine. Continuous antimicrobial feeding over the entire growing/finishing phase had no effect on community erm‐methylase gene copy numbers or faecal community structure. Significance and Impact of the Study: Antimicrobial growth promoters are believed to function by altering gut bacterial communities. However, widespread MLS_B resistance within the faecal community of intensively raised swine likely negates any potential effects that these antimicrobials might have on altering the faecal community. These findings suggest that if AGP‐mediated alterations to gut communities are an important mechanism for growth promotion, it is unlikely that these would be associated with the colonic community.     

Effects of ad libitum and restricted feeding on early production performance and body composition of Yorkshire pigs selected for reduced residual feed intake

Residual feed intake (RFI), defined as the difference between observed and expected feed intake based on growth and backfat, has been used to investigate genetic variation in feed efficiency in cattle, poultry and pigs. However, little is known about the biological basis of differences in RFI in pigs. To this end, the objective of this study was to evaluate the fifth generation of a line of pigs selected for reduced RFI against a randomly selected Control line for performance, carcass and chemical carcass composition and overall efficiency. Here, emphasis was on the early grower phase. A total of 100 barrows, 50 from each line, were paired by age and weight (22.6 ± 3.9 kg) and randomly assigned to one of four feeding treatments in 11 replicates: ad libitum (Ad), 75% of Ad (Ad75), 55% of Ad (Ad55) and weight stasis (WS), which involved weekly adjustments in intake to keep body weight (BW) constant for each pig. Pigs were individually penned (group housing was used for selection) and were on treatment for 6 weeks. Initial BW did not significantly differ between the lines (P > 0.17). Under Ad feeding, the low RFI pigs consumed 8% less feed compared with Control line pigs (P < 0.06), had less carcass fat (P < 0.05), but with no significant difference in growth rate (P > 0.85). Under restricted feeding, low RFI pigs under the Ad75 treatment had a greater rate of gain while consuming the same amount of feed as Control pigs. Despite the greater gain, no significant line differences in carcass composition or carcass traits were observed. For the WS treatment, low RFI pigs had similar BW (P > 0.37) with no significant difference in feed consumption (P > 0.32). Overall, selection for reduced RFI has decreased feed intake, with limited differences in growth rate but reduced carcass fat, as seen under Ad feeding. Collectively, results indicate that the effects of selection for low RFI are evident during the early grower stage, which allows for greater savings to the producer.     

Co-administration of live attenuated Salmonella enterica serovar Typhimurium expressing swine interleukin-18 and interferon-α provides enhanced Th1-biased protective immunity against inactivated vaccine of pseudorabies virus

The co-administration of two or more cytokines may generate additive or synergistic effects for controlling infectious diseases. However, the practical use of cytokine combinations for the modulation of immune responses against inactivated vaccine has not been demonstrated in livestock yet, primarily due to protein stability, production, and costs associated with mass administration. In light of the current situation, we evaluated the immunomodulatory functions of the combined administration of swine interleukin-18 (swIL-18) and interferon-α (swIFN-α) against an inactivated PrV vaccine using attenuated Salmonella enterica serovar Typhimurium as a cytokine delivery system. Co-administration of S. enterica serovar Typhimurium expressing swIL-18 and swIFN-α produced enhanced Th1-biased humoral and cellular immune responses against the inactivated PrV vaccine, when compared to single administration of S. enterica serovar Typhimurium expressing either swIL-18 or swIFN-α. Also, enhanced immune responses in co-administered piglets occurred rapidly after virulent PrV challenge, and piglets that received co-administration of S. enterica serovar Typhimurium expressing swIL-18 and swIFN-α displayed a greater alleviation of clinical severity following the virulent PrV challenge, as determined by clinical scores and cumulative daily weight gain. Furthermore, this enhancement was confirmed by reduced nasal shedding of PrV following viral challenge. Therefore, these results suggest that oral co-administration of S. enterica serovar Typhimurium expressing swIL-18 and swIFN-α provide enhanced Th1-biased immunity against inactivated PrV vaccine to alleviate clinical signs caused by PrV challenge.     

DNA uptake in swine sperm: Effect of plasmid topology and methyl‐beta‐cyclodextrin‐mediated cholesterol depletion

Sperm‐mediated gene transfer (SMGT), the ability of sperm cells to spontaneously incorporate exogenous DNA and to deliver it to oocytes during fertilization, has been proposed as an easy and efficient method for producing transgenic animals. SMGT is still undergoing development and optimization to improve the uptake efficiency of foreign DNA by sperm cells, which is a preliminary, yet critical, step for successful SMGT. Towards this aim, we developed a quantitative, real‐time PCR‐based assay to assess the absolute number of exogenous plasmids internalized into the spermatozoon. Using this technique, we found that the circular form of the DNA is more efficiently taken up than the linearized form. We also found that DNA internalization into the nucleus of porcine sperm cells is better under specific methyl‐β‐cyclodextrin (MCD)‐treated conditions, where the plasma membrane properties were altered without significantly compromising sperm physiology. These results provide the first evidence that membrane cholesterol depletion by MCD might represent a novel strategy for enhancing the ability of sperm to take up heterologous DNA. Mol. Reprod. Dev. 79: 853–860, 2012. © 2012 Wiley Periodicals, Inc.     

摄食行为对小型猪心脏自主神经功能的影响

目的观察摄食行为对小型猪心脏自主神经功能的影响。方法利用大动物无创遥测技术观察清醒活动状态下小型猪摄食前（BI）、摄食过程中（IP）、摄食后（AI）、AI 2 h和AI 4h的心电图（ECG）和自主活动,并用HRV功率谱分析其自主神经功能。结果与摄食前比较,小型猪摄食过程中心率（HR）、自主活动和标准化低频成分（LFnu）明显增加,RR间期（RRI）、总功率（TP）、极低频成分（VLF）、高频成分（HF）明显减少,LF/HF比值明显升高;且随着摄食后恢复时间的延长,小型猪HR、自主活动、LFnu均有所降低,而RRI、TP、VLF、HF均有所升高,LF/HF比值逐渐降低,并在摄食后2 h、4 h时变化显著;相关分析显示摄食行为与TP、VLF、HF、LF和LF/HF密切相关,多元线性逐步回归分析亦显示摄食行为与VLF、LF/HF和TP密切相关,且VLF起主要作用。结论小型猪摄食行为不仅影响心脏活动;而且能引起小型猪心脏自主神经控制能力发生改变,其中VLF在摄食行为过程中占有重要作用。     

Mammalian Visitation to Candidate Feral Swine Attractants

Abstract Few data exist regarding suitable feral swine (Sus scrofa) attractants in the United States. We compared species-specific visitation and contact rates of mammals to 11 candidate feral swine attractants at scent stations using motion-sensing digital photography to identify promising attractants. We found feral swine had greater visitation rates to apple and strawberry stations than to control stations. We recommend managers consider using strawberry attractants for feral swine-specific applications. If, however, a general feral swine attractant is needed, then apple, berry, or caramel attractants may perform well.     

Viability of zoonotic pathogens Escherichia coli and Salmonella in swine manure slurries with and without a urease inhibitor and thymol

Aims: To determine the effects of urine, a urease inhibitor and/or an odour‐reducing antimicrobial compound, on zoonotic pathogens in swine manure slurries. Methods and Results: Swine faeces were collected and blended with different amounts of urine. Marker strains of Salmonella enterica subsp. enterica serovar Typhimurium and Escherichia coli O157:H7 were inoculated into the manure slurries with or without the urease inhibitor, N‐(n‐butyl) thiophosphoric triamide, or the antimicrobial compound thymol. In slurries containing approximately 1 : 1 or 2 : 1 of urine and faeces, the decreases in colony forming units (CFU) of Salm. Typhimurium and E. coli were similar and few counts were observed after 14 days. When the urine content of the slurry was increased to 5 : 1, both strains died off rapidly. When NBPT was added to the slurries, pathogen CFU was not affected in the 1 : 1 slurry. The 2 : 1 and 5 : 1 slurries had higher urea content and NBPT increased CFU of both pathogens. Thymol addition rapidly killed the pathogens and few CFU of Salmonella or E. coli were observed after day 1. Conclusions: These experiments demonstrate that urea hydrolysis in swine manure affects pathogens. Inhibition of urea hydrolysis may promote pathogen viability. Significance and Impact of the Study: Manure amendments that prevent urea hydrolysis may promote pathogen persistence. Additional treatments with antimicrobials may be required to kill pathogens.     

eIF2-dependent and eIF2-independent modes of initiation on the CSFV IRES: a common role of domain II

Specific interactions of the classical swine fever virus internal ribosomal entry site (IRES) with 40S ribosomal subunits and eukaryotic translation initiation factor (eIF)3 enable 43S preinitiation complexes containing eIF3 and eIF2-GTP-Met-tRNA(iMet) to bind directly to the initiation codon, yielding 48S initiation complexes. We report that eIF5B or eIF5B/eIF3 also promote Met-tRNA(iMet) binding to IRES-40S complexes, forming 48S complexes that can assemble elongation-competent ribosomes. Although 48S complexes assembled both by eIF2/eIF3- and eIF5B/eIF3-mediated Met-tRNA(iMet) recruitment were destabilized by eIF1, dissociation of 48S complexes formed with eIF2 could be out-competed by efficient subunit joining. Deletion of IRES domain II, which is responsible for conformational changes induced in 40S subunits by IRES binding, eliminated the sensitivity of 48S complexes assembled by eIF2/eIF3- and eIF5B/eIF3-mediated mechanisms to eIF1-induced destabilization. However, 48S complexes formed by the eIF5B/eIF3-mediated mechanism on the truncated IRES could not undergo efficient subunit joining, as reported previously for analogous complexes assembled with eIF2, indicating that domain II is essential for general conformational changes in 48S complexes, irrespective of how they were assembled, that are required for eIF5-induced hydrolysis of eIF2-bound GTP and/or subunit joining.     

猪支原体肺炎防治研究进展

本文列举了目前临床上用于防治猪支原体肺炎的药物与疫苗的名称和用法用量,并分析了其作用机制及使用效果。抗生素只能抑制支原体生长,无法完全清除,只能解决暂时性问题,且一旦停止用药容易复发,并容易使支原体产生耐药性。国外使用的主要是灭活疫苗,但它无法激发猪体全身免疫系统,需配合优良佐剂使用。国内研制的弱毒疫苗效果很好,但免疫接种方法难度大,不易推广。本文同时综述了目前实验室关于猪支原体肺炎基因工程疫苗的研究进展,并对该病进一步的综合防控措施提出了建议。     

Analysis of ammonia loss mechanisms in microbial fuel cells treating animal wastewater

Ammonia losses during swine wastewater treatment were examined using single- and two-chambered microbial fuel cells (MFCs). Ammonia removal was 60% over 5 days for a single-chamber MFC with the cathode exposed to air (air-cathode), versus 69% over 13 days from the anode chamber in a two-chamber MFC with a ferricyanide catholyte. In both types of systems, ammonia losses were accelerated with electricity generation. For the air-cathode system, our results suggest that nitrogen losses during electricity generation were increased due to ammonia volatilization with conversion of ammonium ion to the more volatile ammonia species as a result of an elevated pH near the cathode (where protons are consumed). This loss mechanism was supported by abiotic tests (applied voltage of 1.1 V). In a two-chamber MFC, nitrogen losses were primarily due to ammonium ion diffusion through the membrane connecting the anode and cathode chambers. This loss was higher with electricity generation as the rate of ammonium transport was increased by charge transfer across the membrane. Ammonia was not found to be used as a substrate for electricity generation, as intermittent ammonia injections did not produce power. The ammonia-oxidizing bacterium Nitrosomonas europaea was found on the cathode electrode of the single-chamber system, supporting evidence of biological nitrification, but anaerobic ammonia-oxidizing bacteria were not detected by molecular analyses. It is concluded that ammonia losses from the anode chamber were driven primarily by physical-chemical factors that are increased with electricity generation, although some losses may occur through biological nitrification and denitrification.