National survey for Salmonella in pigs, cattle and sheep at slaughter in Great Britain (1999-2000)

AIMS: The objective of these surveys was to estimate the prevalence of faecal carriage of Salmonella in healthy pigs, cattle and sheep at slaughter, and of pig carcase contamination with Salmonella. These data can be used as a baseline against which future change in Salmonella prevalence in these species at slaughter can be monitored. METHODS AND RESULTS: In this first randomized National Survey for faecal carriage of Salmonella in slaughter pigs, cattle and sheep in Great Britain, 2509 pigs, 891 cattle and 973 sheep were sampled in 34 pig abattoirs and 117 red meat abattoirs in England, Scotland and Wales. Carriage of Salmonella in 25 g caecal contents was identified in 578 (23.0% pigs) but in only 134 (5.3%) of carcase swabs. The predominant Salmonella serovars found in both types of sample were S. Typhimurium (11.1% caeca, 2.1% carcases) and S. Derby (6.3% caeca, 1.6% carcases). The main definitive phage types (DT) of S. Typhimurium found were DT104 (21.9% of caecal S. Typhimurium isolates), DT193 (18.7%), untypable strains (17.6%), DT208 (13.3%) and U302 (13.3%). Three isolates of S. Enteritidis (PTs 13A and 4) and one enrofloxacin-resistant S. Choleraesuis were also isolated. A positive 'meat-juice ELISA' was obtained from 15.2% of pigs at 40% optical density (O.D.) cut-off level and 35.7% at 10% cut-off. There was poor correlation between positive ELISA results or carcase contamination and the caecal carriage of Salmonella. The ratio of carcase contamination to caecal carriage rates was highest in abattoirs from the midland region of England and in smaller abattoirs. In cattle and sheep 1 g samples of rectal faeces were tested. Two isolates (i.e. 0.2%) were recovered from cattle, one each of S. Typhimurium, DT193 and DT12. One sheep sample (0.1%) contained a Salmonella, S. Typhimurium DT41. In a small subsidiary validation exercise using 25 g of rectal faeces from 174 cattle samples, three (1.7%) isolates of Salmonella (S. Typhimurium DT104, S. Agama, S. Derby) were found. CONCLUSIONS: The carriage rate of Salmonella in prime slaughter cattle and sheep in Great Britain was very low compared with pigs. This suggests that future control measures should be focused on reduction of Salmonella infection on pig farms and minimizing contamination of carcases at slaughter. SIGNIFICANCE AND IMPACT OF THE STUDY: This work has set baseline figures for Salmonella carriage in these species slaughtered for human consumption in Great Britain. These figures were collected in a representative way, which enables them to be used for monitoring trends and setting control targets.     

Establishing a campylobacter-free pig population through a top-down approach

Fattening pigs are often infected with campylobacter. To eliminate campylobacter from the pig population, a top-down approach, involving the breeding and reproduction farms, seems appropriate. In order to investigate the effectiveness of a top-down approach, sows' faeces from the following farms were analysed for the presence of campylobacter: one specific pathogen free (SPF) farm, three top-breeding farms with no connection with SPF breeding, and a breeding farm repopulated with SPF sows after a period of vacancy (farm 5). The faeces samples from the SPF farm were free from campylobacter. The three top-breeding farms provided faeces samples which were 98% positive for campylobacter. However, only 22% of the faeces samples from farm 5 were positive for campylobacter. In a period of 20 months, the percentage of sows infected with campylobacter on farm 5 did not significantly increase. Genetic typing with ERIC-PCR and RFLP of campylobacter isolates from one of the top-breeding farms and from farm 5 showed a high diversity of campylobacter types. The results suggest that a campylobacter-free pig population can be established in breeding farms by combining a top-down approach (campylobacter-free top-breeding farms) with a strict regime of hygiene management.     

Longitudinal study of the persistence of antimicrobial-resistant campylobacter strains in distinct Swine production systems on farms, at slaughter, and in the environment

The objectives of this study were to compare and characterize the prevalence of antimicrobial-resistant (AR) Campylobacter in conventional and antimicrobial-free (ABF) production systems on farms, at slaughter, and in the environment. Fecal and environmental samples were collected from ABF farms (pigs, 1,239; environment, 797) and conventional farms (pigs, 1,650; environment, 1,325). At slaughter, we collected samples from carcasses, including postevisceration swabs, postchill swabs, and mesenteric lymph nodes from ABF systems (postevisceration swabs, 182; postchill swabs, 199; mesenteric lymph nodes, 184) and conventional systems (postevisceration swabs, 272; postchill swabs, 271; mesenteric lymph nodes, 255) at separate processing facilities. We also sampled the processing plant environment, including truck and lairage floor swab samples (ABF, 115; conventional, 90). Overall, a total of 2,908 Campylobacter isolates, including Campylobacter coli (farm, 2,557, 99.8%; slaughter, 341, 98.3%) and Campylobacter jejuni (farm, 4, 0.2%; slaughter, 6, 1.7%), were isolated in the study. There was no significant difference in the prevalence of Campylobacter between ABF and conventionally raised pigs (farrowing, P = 0.20; nursery, P = 0.06; finishing, P = 0.24) and the environment (P = 0.37). At slaughter, Campylobacter was isolated from all of the stages, including postchill. The highest frequencies of resistance were exhibited against tetracycline (ABF, 48.2%; conventional, 88.3%). Ciprofloxacin-resistant C. coli isolates were observed in conventionally raised (17.1%) and ABF (1.2%) pigs (P = 0.11). Antimicrobial use data from conventional farms indicated significant associations between oxytetracycline use and tetracycline resistance in the nursery pigs (P = 0.01), between tiamulin exposure and azithromycin and erythromycin resistance in nursery (P < 0.01) and finishing (P < 0.01) pigs, and between enrofloxacin exposure and ciprofloxacin and nalidixic acid resistance in farrowing (P < 0.01) and nursery (P < 0.01) pigs. Identical antimicrobial resistance profiles were observed in the pigs and their environments on farms and at slaughter. In summary, our results highlight the persistence and dissemination of AR Campylobacter from farm to slaughter in ABF and conventionally raised pigs and their environments.     

Phenotypic and genotypic characterization of Salmonella spp. Isolated from pigs and their farm environment in Korea

This study's objective was to determine the prevalence of Salmonella spp. in pigs and their farm environments in Korea, and to investigate the relationship between the strains based on their phenotypic and genotypic characteristics. A total of 36 Salmonella spp. were isolated in this study: 18 isolates from 492 pigs (3.7%) and 18 isolates from 418 (4.3%) farmhouse environmental samples from 16 different pig farms. Of the Salmonella strains isolated from the numerous environmental samples, the highest prevalence was observed in slurry or manure, followed by partitions, farmer's hands, floors, water/ nipples, ventilation sources, and feed, respectively. All the Salmonella isolates originating from different farms were genetically distinct. In three farms, however, identical phage types and pulse-field gel electrophoresis patterns were observed among Salmonella isolates from pig feces and environmental samples. This study suggests that environments contaminated with Salmonella could pose an infection risk to pigs on pig farms.     

Persistence of a Salmonella enterica serotype typhimurium clone in Danish pig production units and farmhouse environment studied by pulsed field gel electrophoresis (PFGE)

The clonal relationship among Salmonella enterica serotype Typhimurium isolates from selected pig production units in Denmark was investigated by the pulsed field gel electrophoresis (PFGE) typing method to determine environmental survival and spread of Salmonella in different herds. Thirty-four Typhimurium isolated during 1996-1998 from porcine faeces and environmental samples from three pig farms designated 1, 3 and 5 were characterised by PFGE using two restriction enzymes. Farm 5 supplied piglets to farm 1 and the herds were located close to each other. Results of PFGE analysis showed both intra- and inter-relationships, i.e. identical PFGE patterns among the faecal and environmental isolates from farm 1 and farm 5. All the isolates from farm 3 irrespective of the source showed identical PFGE patterns, but were different from samples from farms 1 and 5. This study indicates spread between farms and survival of a farm-specific clone. Furthermore, identical PFGE patterns of isolates from piglet supplier and finisher herds indicate that the farrow-to-grower herd of farm 5 was sub-clinically infected prior to delivery to farm 1 and thereby caused the transmission of Salmonella.     

Field Trials with a New Genetically Engineered Vaccine for Protection Against Progressive Atrophic Rhinitis in Pigs

Field trials were carried out testing a new genetically engineered vaccine against Progressive Atrophic Rhinitis. The vaccine contained a non-toxic recombinant derivative of the P. multocida toxin. The experimental vaccine was compared with a commercial vaccine in 4 farms and in 1 farm 2 different dose regimens were applied. A total of 825 sows were included. The primary efficacy variable was a comparison of post mortem evaluation of the degree of conchae atrophy in the 4585 pigs. The pigs were slaughtered at normal slaughter weight. The secondary efficacy variables were serological response and age at slaughter. In all farms the experimental vaccine provided significantly better protection of the progeny than the control vaccine. The serological response in sows was significantly higher in all farms than the response to the control vaccine. The serological response did not differ between farms.     

Longitudinal Study of Distributions of Similar Antimicrobial-Resistant Salmonella Serovars in Pigs and Their Environment in Two Distinct Swine Production Systems

The aim of this longitudinal study was to determine and compare the prevalences and genotypic profiles of antimicrobial-resistant (AR) Salmonella isolates from pigs reared in antimicrobial-free (ABF) and conventional production systems at farm, at slaughter, and in their environment. We collected 2,889 pig fecal and 2,122 environmental (feed, water, soil, lagoon, truck, and floor swabs) samples from 10 conventional and eight ABF longitudinal cohorts at different stages of production (farrowing, nursery, finishing) and slaughter (postevisceration, postchill, and mesenteric lymph nodes [MLN]). In addition, we collected 1,363 carcass swabs and 205 lairage and truck samples at slaughter. A total of 1,090 Salmonella isolates were recovered from the samples; these were isolated with a significantly higher prevalence in conventionally reared pigs (4.0%; n = 66) and their environment (11.7%; n = 156) than in ABF pigs (0.2%; n = 2) and their environment (0.6%; n = 5) (P < 0.001). Salmonella was isolated from all stages at slaughter, including the postchill step, in the two production systems. Salmonella prevalence was significantly higher in MLN extracted from conventional carcasses than those extracted from ABF carcasses (P < 0.001). We identified a total of 24 different serotypes, with Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Anatum, Salmonella enterica serovar Infantis, and Salmonella enterica serovar Derby being predominant. The highest frequencies of antimicrobial resistance (AR) were exhibited to tetracycline (71%), sulfisoxazole (42%), and streptomycin (17%). Multidrug resistance (resistance to ≥3 antimicrobials; MDR) was detected in 27% (n = 254) of the Salmonella isolates from the conventional system. Our study reports a low prevalence of Salmonella in both production systems in pigs on farms, while a higher prevalence was detected among the carcasses at slaughter. The dynamics of Salmonella prevalence in pigs and carcasses were reciprocated in the farm and slaughter environment, clearly indicating an exchange of this pathogen between the pigs and their surroundings. Furthermore, the phenotypic and genotypic fingerprint profile results underscore the potential role played by environmental factors in dissemination of AR Salmonella to pigs.     

Salmonella enterica in swine production: assessing the association between amplified fragment length polymorphism and epidemiological units of concern

The aims of this study were to determine the ability of amplified fragment length polymorphism (AFLP) to differentiate Salmonella isolates from different units of swine production and to demonstrate the relatedness of Salmonella between farms and abattoirs by AFLP. Twenty-four farms in the midwestern United States were visited four times from 2006 to 2009. At each farm or abattoir visit, 30 fecal samples or 30 mesenteric lymph nodes were collected, respectively. A total of 220 Salmonella isolates were obtained, serotyped, and genotyped by multilocus sequence typing (MLST) and AFLP. These 220 isolates clustered into 21 serotypes, 18 MLST types, and 14 predominant AFLP clusters based on a genetic similarity threshold level of 60%. To assess genetic differentiation between farms, harvest cohorts, and pigs, analysis of molecular variance was conducted using AFLP data. The results showed 65.62% of overall genetic variation was attributed to variance among pigs, 27.21% to farms, and 7.17% to harvest cohorts. Variance components at the farm (P = 0.003) and pig (P = 0.001) levels were significant, but not at the harvest cohort level (P = 0.079). A second analysis, a permutation test using AFLP data, indicated that on-farm and at-abattoir Salmonella from pigs of the same farms were more related than from different farms. Therefore, among the three subtyping methods, serotyping, MLST, and AFLP, AFLP was the method that was able to differentiate among Salmonella isolates from different farms and link contamination at the abattoir to the farm of origin.     

Effect of rearing system and mixing at loading on transport and lairage behaviour and meat quality: comparison of outdoor and conventionally raised pigs

The effect of raising pigs outdoors or conventionally in a barren environment was investigated with respect to behaviour during a 3 to 4 h journey and a 2 h lairage, blood chemistry at slaughter and meat quality characteristics. Pigs were either kept in farm pen groups or were mixed at loading and kept in the groups, so formed, until slaughter. Non-mixed outdoor pigs settled more quickly during transport and lay down to a greater extent at the end of the journey and lairage period compared with conventionally raised pigs. Mixing led to fewer pigs sitting and lying during transport for conventionally raised pigs, where nearly 80% were still standing at the end of the journey. Mixing had no effect on pig posture in the lairage. Outdoor pigs were less aggressive than conventionally raised pigs especially during lairage and had a lower frequency of unacceptable skin damage in the rear and shoulder area. Aggressive interactions were almost exclusively confined to mixed groups and occurred mainly between pigs from different farm pens, i.e. between unfamiliar animals. Mixing at loading led therefore to higher levels of unacceptable skin damage. Cortisol concentrations in slaughter blood were not affected by rearing system or mixing, but mixed, conventionally raised pigs had higher plasma creatine kinase (CK) activities than non-mixed ones (1132 v. 761 U/l, respectively, P < 0.05). Outdoor pigs had similar CK activities, irrespective of mixing (682 and 771 U/l for mixed and non-mixed, respectively). Muscle pH early post mortem was highest in outdoor pigs and muscle temperature lower, but no pig showed pH values below 6.0. Ultimate pH values were both higher (Semimembranosus (S)) and lower (Semispinalis capitis (SC)) than in conventionally raised pigs, and outdoor pigs tended to have a lower frequency of higher than normal pH values. Internal reflectance (MQM) values in Biceps femoris (BF) were highest in outdoor pigs but the incidence of pale, soft and exudative (PSE) meat was low, varying between 0% and 1% for experimental groups. In general, the effects of rearing system and mixing on meat quality measurements taken early post mortem or the day after slaughter were slight, but the trends seen support the CK results, and show that conventionally raised pigs may have found mixing pre-slaughter to be more physically stressful than outdoor pigs did.     

Application of variable number of tandem repeat analysis to track Salmonella enterica ssp. enterica serovar Typhimurium infection of pigs reared on three British farms through the production cycle to the abattoir

Aims: This study investigated the diversity and persistence of Salmonella strains through the pork finishing cycle, from the farm into the abattoir. Methods and Results: Isolates from four batches of finishers, from farm to abattoir, were used. Salmonella Typhimurium isolates were subjected to molecular typing using pulsed‐field gel electrophoresis and variable number of tandem repeat analysis. The results demonstrated that infection was transferred from the farm to the abattoir. Within the abattoir, infection from individual pigs contaminated the exterior of the carcass and pigs exposed to Salmonella in the lairage were infected. Conclusions: Salmonella can be introduced at various points in the pig production and slaughter process. Carcass contamination may arise from infection on farm and exposure in the lairage and abattoir environment. Pigs could be contaminated by previous batches of pigs while in lairage or during the dressing process. Salmonella infection on farms is dynamic with multiple serovars present from different sources. Significance and Impact of the Study: Molecular typing methods facilitated the tracing of Salm. Typhimurium through the production cycle and differentiated some farm‐acquired from abattoir‐acquired strains. The findings emphasize the importance of integrated control strategies along the pork food chain.     

Natural transmission of Salmonella choleraesuis in swine.

This experiment was designed to study the natural transmission of Salmonella choleraesuis in swine. Forty pigs were divided into three groups. Group 1 (n = 12) was challenged with 10(8) CFU of S. choleraesuis per ml by intranasal inoculation. One day postinoculation (p.i.), group 2 (n = 24) was commingled with group 1. Group 3 (n = 4) served as uninoculated controls. Serum samples were collected weekly. Blastogenesis assays and necropsies were performed at 1, 2, 4, 6, 9, and 12 weeks p.i., and 16 tissue samples per pig were collected and cultured. Environmental (pooled feces from the pen floor) levels of S. choleraesuis were 2.61 log10 CFU/g of feces at 24 h p.i. (immediately prior to commingling). Severe clinical signs were observed in groups 1 and 2. The results indicated that at least 16% of group 2 pigs were shedding S. choleraesuis within 24 h of commingling. At 1 week p.i., 32 of 32 group 1 and 39 of 62 group 2 tissue samples were positive for S. choleraesuis. Only 3 of 12 group 2 pigs were positive at 6, 9, and 12 weeks (1 pig for each week), indicating that only a small proportion of infected swine become long-term carriers. At 12 weeks p.i., only the colon and colonic lymph node samples of one pig from group 2 were positive. Humoral, mucosal, and cellular immune responses were similar between groups 1 and 2. These data demonstrate that a few pigs shedding low levels of Salmonella organisms before slaughter can result in rapid transmission and subsequent shedding by many swine.     

Carriage and Fecal Counts of Cefotaxime M-Producing Escherichia coli in Pigs: a Longitudinal Study

Current knowledge on extended-spectrum beta-lactamases (ESBLs) in animals is based largely on cross-sectional studies and qualitative data. The aim of this longitudinal study was to elucidate carriage proportions and fecal counts of ESBL-producing Escherichia coli in pigs during the production cycle. At each of three ESBL-positive single-sited farrow-to-finisher pig farms (farms A, B, and C) included in the study, individual fecal samples were taken from 17 to 20 sows 1 week before farrowing and from 2 piglets of each sow''s litter four times from birth to slaughter (as piglets, weaners, and finishers). Cefotaxime (CTX)-resistant coliforms in feces were counted on MacConkey agar containing 2 μg/ml CTX and characterized for the presence of ESBL-encoding genes by PCR and sequencing. CTX-M-positive pigs were detected in all age groups at farms A (bla_CTX-M-9 group, compatible with bla_CTX-M-14/17) and B (bla_CTX-M-1 group, compatible with bla_CTX-M-1/61), whereas only three weaners were positive at farm C (bla_CTX-M-1 group, compatible with bla_CTX-M-1/61). A significant decrease in carriage was detected during the production cycle, with on average 50% carriage immediately after birth, 58% just before weaning, 29% during weaning, and 12% during finishing. The observed reduction in numbers of CTX-M-positive pigs was accompanied by a significant reduction in mean fecal counts of CTX-resistant coliforms from ∼10⁷ CFU/g in piglets to ∼10³ CFU/g in finishers (P < 0.001). These findings provide novel information about the epidemiology of ESBLs at the farm level and have important implications for assessments of risks of meat contamination during slaughter.     

Salmonella on pig carcasses: positive pigs and cross contamination in the slaughterhouse

AIMS: The purpose of this study was to investigate the prevalence of Salmonella in pigs at the moment of slaughter and in the slaughterhouse environment. METHODS AND RESULTS: In total, five different commercial slaughterhouses were sampled during eight slaughterhouse visits. Carcass swabs, colon content and mesenteric lymph nodes were taken to reflect the animal status and from the slaughterhouse environmental samples were taken. Salmonella was isolated from 37% of the carcass samples as a mean value. High variations were noticed between different slaughterhouses (between 0 and 70%) and sampling days in the same abattoir (between 3 and 52%). A correlation was found between the carcass contamination and the status of the delivered animals (P=0.01675). Cross contamination was estimated to account for 29% of the positive carcasses. The slaughterhouse environment was highly contaminated; before starting the slaughtering activities 25% of the samples were positive on average. The most prevalent serotypes isolated at the slaughterhouse environment and from the colon content were S. Typhimurium, S. Livingstone and S. Derby. On carcasses S. Typhimurium was predominately isolated (71%). The biggest variability of serotypes was found in the mesenteric lymph nodes. Serologically 56.3% of the pigs were found positive for Salmonella using a cut-off level of the optical density percentage higher than 10 (O.D.% > or = 10). While on individual pig level the correlation between the bacteriological and serological data was poor, because of recent Salmonella infections, a better correlation was found at the herd level on the moment of slaughtering. CONCLUSION: A high degree of carcass contamination is noticed after slaughtering. This contamination resulted from the delivery of Salmonella-positive pigs and cross-contamination from the slaughterhouse environment. SIGNIFICANCE AND IMPACT OF THE STUDY: In pigs, Salmonella carriage is high, but it is obvious that slaughterhouse hygiene is a determinative factor for managing carcass contamination.     

Streptococcus R (Streptococcus suis type II) infection in pigs in Japan

Since the first outbreak of an epizootic disease on a pig farm in Shimane Prefecture in 1979, similar diseases have occurred continually on other 8 pig farms in the same prefecture until 1982. Main clinical symptoms of the disease were recumbency, convulsion, anorexia and paddling. The diseased pigs ranged mostly from 35 to 67 days of age. Monthly fatality on one pig farm for 1 year was 0.2 to 3.6%. Morbidities in affected litters were mostly at a level of 20 to 30% on 7 pig farms. The diseases were diagnosed as streptococcal meningitis and septicemia with each one of endocarditis and pneumonitis by pathological and bacteriological studies on 20 affected pigs. Distribution of piglets from a breeding farm to pig farms was considered as one of the causes of prevalence in the prefecture. Representative 20 strains of the isolates from diseased animals on 9 pig farms were identified as Streptococcus R (Streptococcus suis type II) by biological and serological examinations. For the latter examination, anti-Streptococcus R, S and T sera were prepared. It was also indicated that the disease had occurred in 8 prefectures in addition to Shimane, because positive results had been obtained from 41 strains submitted from those prefectures for serological diagnosis. The minimal inhibitory concentration was examined in 18 drugs to 19 isolates. It was the lowest in ampicillin and thiopeptin of all the drugs.     

Olfactory evaluation of boar taint: effect of factors measured at slaughter and link with boar taint compounds

There is a commitment by the European pig sector to ban surgical castration of male piglets in the European Union in 2018. One alternative to castration is to raise entire male pigs, with an increased risk of boar taint. A field study was performed to: (1) evaluate inter- and intra-farm variation in boar taint prevalence, (2) investigate factors measured at slaughter influencing boar taint and (3) evaluate the relationship between sensorial scoring by a trained panel and the concentration of boar taint components. From 34 farms, neck fat samples were collected from all entire male pigs in at least two slaughter batches per farm (78 batches; 9167 animals). In addition to olfactory boar taint analysis, data were also collected on fresh skin lesions (score 0 to 3) at the slaughter line, slaughter weight, lean meat percentage, duration of transport, time spent in lairage, total delivery duration, day length, shortening of days and outdoor mean temperature. Using the hot iron method, neck fat samples were scored (eight-point scale) for boar taint. Average boar taint prevalence (score ≥3) was 5.6±2.5% and the mean difference between the maximum and minimum prevalence per farm was 4.3±3.2%. Androstenone (AND), skatole (SKA) and indole concentrations were measured for a subset (n=254) of the samples. According to binomial univariate mixed models, entire male pigs with a higher skin lesion score had higher odds of having boar taint (P=0.031), as did fatter entire male pigs (P<0.001). In the binomial multivariate mixed model lean meat percentage (P<0.001) and outdoor mean temperature (P=0.005) remained as only significant factors. Based on our results, we can conclude that these statistically significant at least partially influence the prevalence of boar taint. According to the binomial univariate mixed models SKA concentration in liquid fat seems a better predictor for boar taint than AND. There were no significant synergetic effects between boar taint compounds.     

The effect of sex and slaughter weight on performance,carcass quality and gross margin,assessed on three commercial pig farms

Economic margins on pig farms are small, and changing slaughter weights may increase farm profitability. However, one can question if the optimal slaughter weight is the same for each sex. On three farms, crossbred pigs (n = 1128) were used to determine the effect of sex and slaughter weight on performance, carcass quality and gross margin per pig place per year. On each farm, an equal number of entire males (EMs), barrows (BAs), immunocastrates (IC) and gilts (GIs) were housed separately in group pens. Pens were randomly divided into three categories of different slaughter weights: 105, 117 and 130 kg BW. In BA, the high average daily feed intake (ADFI) and the lower capacity to gain muscle led to a higher feed conversion ratio (FCR) and lower lean meat percentage in comparison to EM and IC. In all sexes, ADFI and FCR increased with an increasing slaughter weight but the effect of slaughter weight on carcass quality varied between sexes. In BA and GI, slaughter weight had no effect on carcass quality, but in EM and IC, carcass quality improved at higher slaughter weights. Gross margin per pig place per year was calculated as gross margin per pig × barn turnover per year, taking into account fixed costs per round, feed costs and output price per pig. The slaughter weight that gained the highest gross margin per year differed between sexes. Slaughtering BA and GI at 130 kg BW, compared to 105 or 117 kg BW, decreased the gross margin per pig place per year due to the lower margin per pig and barn turnover at higher weights. In IC and EM, no difference in gross margin per pig place per year could be demonstrated between slaughtering at 105, 117 or 130 kg BW. In IC, the increasing gross margin per pig with increasing slaughter weights counteracted with the lower barn turnover. In EM, gross margin per pig did not differ between slaughter weights, but the effect of barn turnover was too small to demonstrate significant differences between slaughter weights on gross margin per pig place per year. In conclusion, slaughter weight has an impact on profitability in BA and GI: they should not be slaughtered at 130 kg BW but at lower weights, but no effect could be demonstrated in EM and IC.     

Local identification of porcine haptoglobin in salivary gland and diaphragmatic muscle tissues

In order to clarify the origin of the haptoglobin (Hp) quantified in saliva and meat juice samples, the extrahepatic localization of Hp in salivary gland and in diaphragmatic muscle, as part of the systemic acute phase response in pigs, was studied by immunohistochemistry. For this purpose a specific monoclonal antibody (mAb) produced by immunising mice with purified porcine Hp was used. Reactivity of the mAb was assessed by direct ELISA and by western blot, which showed the ability and specificity of the mAb to identify porcine haptoglobin as a purified antigen or in porcine serum in a native or denatured but non-reduced state. Five healthy and five diseased pigs were sampled at slaughter for serum and tissue procurement. Hepatic immunohistochemical analysis was used as control of the acute phase reaction status. In the liver, cell immunostaining revealed a perinuclear, cytoplasmic localization of Hp within hepatocytes, following mainly a periacinar pattern. Extrahepatic immunohistochemical analysis revealed positive cells in the glandular acini and duct epithelial cells of the salivary gland and intrasarcoplasmic immunolabelling of random diaphragmatic myofibers. A possible role of both salivary gland and diaphragmatic muscle on local Hp production could be postulated based on the present immunohistochemical study, which supports the concept that other cells besides hepatocytes may have the potential to produce Hp in the pig.     

Social stress increases fecal shedding of Salmonella typhimurium by early weaned piglets

"Segregated early weaning" (SEW) of pigs reduces exposure to pathogenic bacteria, but upon arrival at grower facilities pigs may be co-mingled regardless of farm of origin. The present study was designed to examine the effect of mixing (social) stress on populations of Salmonella enterica Typhimurium in SEW pigs. Piglets (7 days old; n = 28 in each of 2 replicates) were separated into 2 treatments (control and mixed groups) of 2 pens per treatment (7 piglets/pen). One (n = 1) "seeder" pig/pen was inoculated with 10(9) CFU of S. Typhimurium. Each seeder was placed with non-inoculated "contact" piglets (n = 6). A"contact" piglet was swapped each day between the "mixed" pens for 5 days; pigs in control pens were not exchanged. On day 5, the incidence of fecal Salmonella shedding was higher in the mixed contact pigs (P < 0.05). Rectal Salmonella and cecal coliform populations in mixed pigs were significantly (P < 0.05) greater than in control pigs but cecal Salmonella populations were not different. Mixed pigs were more susceptible to tissue invasiveness (i.e., Salmonella-positive tonsils and lymph nodes) than control pigs. These results indicate that social stress of weaned pigs may increase susceptibility to and/or fecal shedding of Salmonella. Food-borne Salmonella infections in the United States are estimated to cost the economy dollar 2.4 billion annually (ERS/USDA, 2001). Approximately 6-9% of human salmonellosis is associated with the consumption of pork products (Frenzen et al., 1999). Salmonella is relatively common on swine farms and has been isolated from all stages of the pork production chain (Davies et al., 1999; Fedorka-Cray et al., 1997b; Rostagno et al., 2003). Salmonella is a threat to the pork industry not only from a food-safety perspective as a public health concern, but some Salmonella serotypes can cause clinical illnesses in swine, negatively impacting production efficiency and profitability (Schwartz, 1991).