Herd factors associated with the seroprevalences of four major respiratory pathogens in slaughter pigs from farrow-to-finish pig herds

The objective of this study was to investigate sero-epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H1N1 and H3N2 viruses and Aujeszky disease virus (ADV) in fattening pigs from 150 randomly selected farrow-to-finish pig herds. Different herd factors were examined as potential risk indicators for the percentage of pigs with antibodies against the 4 pathogens. The median within-herd seroprevalences of the pathogens were: Mh 76%, H1N1 100%, H3N2 40% and ADV 53%. There was a positive association between the seroprevalences of both influenza viruses, and a negative association between the seroprevalences of ADV and H1N1. The percentage of pigs seropositive for Mh increased with the purchase of gilts and with the season (slaughter date in March-April). The within-herd seroprevalences of both influenza viruses were higher in the case of a higher density of pig herds in the municipality. A higher number of fattening pigs per pen additionally increased the risk of being seropositive for H3N2. The percentage of pigs with anti-gE-antibodies against the wild type ADV increased with higher airspace stocking density in the finishing unit, increasing herd size, increasing number of pig herds in the municipality and slaughter date in March-April. Increased seroprevalences for these 4 respiratory pathogens were mostly associated with pig density in the herd and its vicinity, the winter period, and with the purchase of gilts. Purchase of gilts, number of fattening pigs per pen and airspace stocking density are risk factors that can be managed directly by farmers striving to attain a high respiratory health status of pigs.     

Risk indicators for the seroprevalence of Mycoplasma hyopneumoniae, porcine influenza viruses and Aujeszky's disease virus in slaughter pigs from fattening pig herds.

Epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H1N1 and H3N2 viruses, and Aujeszky's disease virus (ADV) were investigated in slaughter pigs from 50 fattening pig herds. Herd factors as potential risk indicators for respiratory disease were obtained by means of a questionnaire. At slaughter, blood samples were collected from each herd, and the proportion of seropositive pigs per herd was assessed for each of these pathogens. The median herd-level seroprevalence of the agents were: Mh 88%, H1N1 100%, H3N2 60% and ADV 90%. The percentage of herds in which all investigated fattening pigs were seronegative for these agents was: Mh 0%, H1N1 0%, H3N2 12% and ADV 18%. The percentage of herds in which all investigated fattening pigs were seropositive for these agents was: Mh 8%, H1N1 71%, H3N2 22% and ADV 40%. A positive association was found between influenza H1N1 and H3N2 viruses, and a negative association between influenza H3N2 virus and ADV. There were no risk indicators for the seroprevalence of Mh. Three risk indicators were associated with the seroprevalence of influenza H1N1 virus: a fully slatted floor, an increasing number of pigs in the municipality and dry feeding. Three risk indicators were found for the seroprevalence of influenza H3N2 virus: purchase of pigs from > or = two herds, an increasing number of pigs in the municipality and natural ventilation. The seroprevalence of ADV was influenced by two risk indicators: an increasing number of pig herds in the municipality and an increasing number of pigs per pen.     

Comparative growth performance of pigs immunised with a gonadotrophin releasing factor vaccine with surgically castrated pigs and entire boars raised under conventionally managed conditions

The objective of this study was to determine the effect of using a gonadotrophin releasing factor (GnRF) vaccine on growth performance of male pigs. Vaccinated pigs were compared with surgically castrated pigs and entire males under conventionally managed farm conditions. Male pigs were randomly assigned to three treatment groups: pigs surgically castrated during the first week of life (group "C", n=274), pigs immunised twice during the fattening period with a GnRF vaccine, the first when 13-14 weeks of age and the second when 20-21 weeks of age (group "V" n=280) and entire males (group "E", n=56). Average daily weight gain (ADG) was measured during the study. Additionally, feed conversion ratio (FCR) as defined by feed intake/weight gain and feed consumption was assessed during the fattening period. No difference in the ADG during the fattening period could be determined between "C" and "V". From the start of the study until slaughter at study day 160/173 the ADG in group "E" was lower (625 g/day; P) than in group "C" (681 g/day; P < 0.001) and group "V" (675 g/day; P < 0.01). The FCR during the fattening period until study day 160, three days before the first batch of pigs were slaughtered at 24-25 weeks of age, was higher in group"C" (2.72 kg feed intake/kg weight gain) compared with group "V" (2.44 kg feed intake/kg weight gain; P < 0.001) and group "E" (2.44 kg feed intake/kg weight gain; P <0.01). Pigs in group "V" performed similarly to those in group "E" until the second vaccination (day 135) after which time they showed a substantial increase in feed intake and ADG, while retaining an FCR advantage over group C.     

A comparative study of the preventive use of tilmicosin phosphate (Pulmotil premix) and Mycoplasma hyopneumoniae vaccination in a pig herd with chronic respiratory disease

This study was conducted to compare the effects of a preventive in-feed medication programme using tilmicosin (Pulmotil 200 premix, Elanco Animal Health) at 200 p.p.m. with those of Mycoplasma hyopneumoniae (Mh) vaccination programme (Stellamune Mycoplasma, Pfizer Animal Health). A pig herd with chronic respiratory disease in which infection with Mh played an important role was selected, and a total of 204 piglets were randomly allocated to either the medication (P) or the vaccination (V) group. Pigs in the P group received medicated feed for 3 weeks after weaning (days 34-55), and for 2 weeks late in the nursery period (days 77-98). The piglets in the V group were vaccinated twice intramuscularly, at 4 and 22 days of age. The two groups were compared on the basis of average daily gain (ADG), feed conversion rate (FCR), additional curative medication days (CMD), overall mortality (major variables), a coughing index, pneumonia lesions, and serology against Mh, influenza H1N1 and influenza H3N2 viruses, Actinobacillus pleuropneumoniae (App) and porcine reproductive and respirator, syndrome virus (PRRSV) (minor variables). No significant differences (P > 0.05) were observed for ADG (555 g/day in P group; 567 g/day in V group), FCR (2.64 in P group; 2.41 in V group) and mortality rate (11% in P group; 7% in V group). The average number of additional curative medication days (CMD) per pig was significantly higher (P < 0.01) in the P group (1.5) than in the V group (0.58). At slaughter age, the serological results and the prevalence of macroscopic lung lesions were comparable in the two groups (P > 0.05). With the exception of CMD, the preventive use of tilmicosin at this swine farm was found to confer similar beneficial effects to Mh vaccination.     

Infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae in fattening pigs. Influence of piglet production systems and influence on production parameters

Two hundred and sixty-four feeder pigs from an age-segregated herd (A-pigs) and 264 feeder pigs from a continuous production system (C-pigs) were transferred into identical but separate rooms in a fattening herd employing all-in all-out production. On arrival, none of the A-pigs and 39% of the C-pigs were seropositive to Mycoplasma hyopneumoniae (M. hyo). At slaughter 30% of the A-pigs and 99% of the C-pigs were seropositive to M. hyo. Pigs with acute swine enzootic pneumonia (SEP) at slaughter and pigs that seroconverted to M. hyo late in the rearing period showed a lower growth rate compared with pigs with chronic SEP or pigs that seroconverted to M. hyo early or not at all. No A-pigs and 12% of the C-pigs were seropositive to Actinobacillus pleuropneumoniae 2 (A. pp 2) at arrival to the fattening herd. At slaughter, 10% of the A-pigs and 13% of the C-pigs were seropositive to A. pp 2. On arrival, the prevalence of pigs seropositive to A. pp 3 was lower among A-pigs than C-pigs. During the fattening period the situation was reversed. The prevalence of pleuritis at slaughter was low (2.7-4.2%) and there were no associations between pleuritis at slaughter and developments of antibodies to A. pp 2 or 3. However, pigs with pleuritis developed antibodies to M. hyo to a greater extent than pigs without pleuritis. Pigs with pleuropneumonia at slaughter and pigs that seroconverted to A. pp 2 or 3 had, during certain periods of the rearing, higher growth rates compared with pigs without pleuropneumonia or pigs that did not seroconvert to A. pp 2 or 3.     

Risk Indicators for the Seroprevalence of Mycoplasma hyopneumoniae,Porcine Influenza Viruses and Aujeszky's Disease Virus in Slaughter Pigs from Fattening Pig Herds

Epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H_***2N₁ and H₃N₂ viruses, and Aujeszky's disease virus (ADV) were investigated in slaughter pigs from 50 fattening pig herds. Herd factors as potential risk indicators for respiratory disease were obtained by means of a questionnaire. At slaughter, blood samples were collected from each herd, and the proportion of seropositive pigs per herd was assessed for each of these pathogens. The median herd-level seroprevalence of the agents were: Mh 88%, H_***3N₁ 100%, H₃N₂ 60% and ADV 90%. The percentage of herds in which all investigated fattening pigs were seronegative for these agents was: Mh 0%, H_***N₁ 0%, H₃N₂ 12% and ADV 18%. The percentage of herds in which all investigated fattening pigs were seropositive for these agents was: Mh 8%, H₁N₁ 71%, H₃N₂ 22% and ADV 40%. A positive association was found between influenza H₁N₁ and H₃N₂ viruses, and a negative association between influenza H₃N₂ virus and ADV. There were no risk indicators for the seroprevalence of Mh. Three risk indicators were associated with the seroprevalence of influenza H₁N₁ virus: a fully slatted floor, an increasing number of pigs in the municipality and dry feeding. Three risk indicators were found for the seroprevalence of influenza H₃N₂ virus: purchase of pigs from ≥two herds, an increasing number of pigs in the municipality and natural ventilation. The seroprevalence of ADV was influenced by two risk indicators: an increasing number of pig herds in the municipality and an increasing number of pigs per pen.     

A Comparative Study of the Preventive Use of Tilmicosin Phosphate (Pulmotil premix®) and Mycoplasma hyopneumoniae Vaccination in a Pig Herd with Chronic Respiratory Disease

This study was conducted to compare the effects of a preventive in‐feed medication programme using tilmicosin (Pulmotil^® 200 premix, Elanco Animal Health) at 200 p.p.m. with those of a Mycoplasma hyopneumoniae (Mh) vaccination programme (Stellamune^TM Mycoplasma, Pfizer Animal Health). A pig herd with chronic respiratory disease in which infection with Mh played an important role was selected, and a total of 204 piglets were randomly allocated to either the medication (P) or the vaccination (V) group. Pigs in the P group received medicated feed for 3 weeks after weaning (days 34–55), and for 2 weeks late in the nursery period (days 77–98). The piglets in the V group were vaccinated twice intramuscularly, at 4 and 22 days of age. The two groups were compared on the basis of average daily gain (ADG), feed conversion rate (FCR), additional curative medication days (CMD), overall mortality (major variables), a coughing index, pneumonia lesions, and serology against Mh, influenza H1N1 and influenza H3N2 viruses, Actinobacillus pleuropneumoniae (App) and porcine reproductive and respiratory syndrome virus (PRRSV) (minor variables). No significant differences (P > 0.05) were observed for ADG (555 g/day in P group; 567 g/day in V group), FCR (2.64 in P group; 2.41 in V group) and mortality rate (11% in P group; 7% in V group). The average number of additional curative medication days (CMD) per pig was significantly higher (P < 0.01) in the P group (1.5) than in the V group (0.58). At slaughter age, the serological results and the prevalence of macroscopic lung lesions were comparable in the two groups (P > 0.05). With the exception of CMD, the preventive use of tilmicosin at this swine farm was found to confer similar beneficial effects to Mh vaccination.     

Patterns of Mycoplasma hyopneumoniae Infections in Belgian Farrow‐to‐Finish Pig Herds with Diverging Disease‐Course

Patterns of Mycoplasma hyopneumoniae (Mh) infections were investigated in five clinically infected herds and in five herds subclinically infected with Mh. In the clinically infected herds, housing and management conditions were good whereas these conditions were poor in the subclinically infected herds. In each herd, serum antibodies against Mh were detected in pigs of different ages and nasal swabs were taken for Mh detection using nested PCR (nPCR). The percentage of seropositive pigs in the clinically infected herds increased from 8% in pigs of 9 weeks to 52% in pigs of 18 weeks and seroconversion was most shown between 12 and 15 weeks. In the subclinically infected herds, the percentages increased from 2 to 24% and most of the pigs became seropositive between 15 and 18 weeks. The percentage of nPCR positive pigs at 6 weeks was 16 and 0% in the clinically and subclinically infected herds, respectively. The results demonstrate that the seroprevalences were higher in the clinically infected herds and that most of the pigs became infected with Mh at a younger age. It can be concluded that additional factors different from housing and management, like differences among Mh strains, may determine the infection pattern of Mh and the clinical course of the infection.     

Patterns of Mycoplasma hyopneumoniae infections in Belgian farrow-to-finish pig herds with diverging disease-course

Patterns of Mycoplasma hyopneumoniae (Mh) infections were investigated in five clinically infected herds and in five herds subclinically infected with Mh. In the clinically infected herds, housing and management conditions were good whereas these conditions were poor in the subclinically infected herds. In each herd, serum antibodies against Mh were detected in pigs of different ages and nasal swabs were taken for Mh detection using nested PCR (nPCR). The percentage of seropositive pigs in the clinically infected herds increased from 8% in pigs of 9 weeks to 52% in pigs of 18 weeks and seroconversion was most shown between 12 and 15 weeks. In the subclinically infected herds, the percentages increased from 2 to 24% and most of the pigs became seropositive between 15 and 18 weeks. The percentage of nPCR positive pigs at 6 weeks was 16 and 0% in the clinically and subclinically infected herds, respectively. The results demonstrate that the seroprevalences were higher in the clinically infected herds and that most of the pigs became infected with Mh at a younger age. It can be concluded that additional factors different from housing and management, like differences among Mh strains, may determine the infection pattern of Mh and the clinical course of the infection.     

Seroprevalence of Actinobacillus pleuropneumoniae serovars 2, 3 and 9 in slaughter pigs from Belgian fattening farms

Fifty randomly selected fattening pig herds were studied to investigate the epidemiological characteristics of infections with Actinobacillus pleuropneumoniae serovars 2, 3 and 9, and to identify risk factors for their within-herd seroprevalences. Information about 13 farm characteristics was obtained by means of a questionnaire and used to assess potential risk factors for the percentage of slaughter pigs with antibodies against each of the three serovars. The presence of antibodies was measured with an indirect ELISA. The median within-herd seroprevalence for serovar 2 was 58 per cent (range 0 to 100 per cent), for serovar 3, 53 per cent (range 10 to 95 per cent), and for serovar 9, 35 per cent (range 5 to 100 per cent). All but one farm tested positive for A pleuropneumoniae serovar 2, and all the farms were positive for A pleuropneumoniae serovars 3 and 9. There was a positive association (P < 0.05) between each pair of serovars. The within-herd seroprevalence of serovar 2 was significantly associated with the density of pig herds in the municipality (odds ratio [OR] = 1.60; P < 0.05) and with the absence of preventive medication at the start of the fattening period (OR = 2.77; P < 0.10). No significant risk factors were found for serovar 3. The percentage of pigs positive for serovar 9 was significantly associated with a slaughter date in June (OR = 2.30; P < 0.10) and with herds in which the finishing houses were not divided into separate compartments (OR = 2.99; P < 0.05).     

Growth performance and whole-body composition of pigs experimentally infected with Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae (Mh) is the primary infectious pathogen responsible for enzootic pneumonia in pigs. Although Mh is thought to impair growth performance, whole-body composition, and fat and protein accretion in pigs with pneumonia have not been reported and the mechanism through which Mh reduces growth is unknown. The objectives of this study were to evaluate the effects of Mh on growth performance, whole-body composition, and protein and fat accretion in nursery pigs and to determine whether Mh infection increases the expression of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha). Sixty-four 2-wk-old Mh-free pigs were used (two trials) in a randomized complete block design. In each trial, two pigs were housed in each of 16 disease-containment chambers. At 4 wk of age, pigs were inoculated intratracheally with 3 mL of Mh broth (P5722-3, 10(7) cfu/mL) or sterile Friis culture medium. Clinical signs of disease and feed intake were monitored daily and body weight was determined weekly for 4 wk. Whole-body composition was determined from pigs killed 0, 14, and 28 d after inoculation, and the comparative slaughter technique was used to estimate protein and fat accretion. At death, gross lung lesions were quantified, and lung tissue was collected to verify the presence or absence of Mh, and to determine cytokine mRNA levels. Control pigs displayed no overt signs of infection and were Mh-negative and free of pulmonary lesions. Pigs inoculated with Mh showed pneumonic coughing (P < 0.005), were Mh-positive, and had pulmonary lesions that affected 4.5% (P < 0.01) and 14.1% (P < 0.001) of total lung surface area at 14 and 28 d, respectively, after inoculation. Ribonuclease protection assays revealed increased IL-1beta (P < 0.04) and TNF-alpha (P < 0.06) mRNA in lung tissue collected from a lesion site compared with tissue collected 10 cm from a lesion site or from control pigs. Interestingly, Mh did not depress weight gain or feed efficiency during any week of the 28-d study (P > 0.10). Moreover, Mh did not affect whole-body fat or protein accretion (P > 0.10). Thus, in spite of inducing disease and expression of inflammatory cytokines, Mh alone did not affect growth performance and whole-body composition of nursery pigs during the 4-wk experiment. The ability of pigs to contend with Mh may have resulted from the absence of other pathogens that generally co-exist with Mh under commercial conditions.     

Varying effects of infections with Mycoplasma hyopneumoniae on the weight gain recorded in three different multisource fattening pig herds

Pigs in three specialized fattening herds were studied with respect to the effect of infection with Mycoplasma hyopneumoniae on weight gain. Individual pigs were weighed four times at 4-week intervals during the fattening period and their daily weight gain over the rearing period was calculated. A blood sample was collected on each weighing occasion and analysed for the presence of antibodies to M. hyopneumoniae. The lungs of the principals were inspected at slaughter and the extent of pneumonic lesions was registered by a specially developed technique that has been proven to warrant a high degree of repeatability. No serum antibodies to M. hyopneumoniae were detected in one of the herds, and no pneumonic lesions were recorded at slaughter in that herd. In the other two herds, the prevalence of pigs with serum antibodies to M. hyopneumoniae increased from 6 to 54% and from 31 to 81%, respectively, during the fattening period. The prevalence of pneumonic lesions at slaughter in these herds was higher the later the pigs seroconverted. On the other hand, the extension of the lung lesions tended to be higher among pigs that seroconverted early during the rearing period. Infections with M. hyopneumoniae acquired early during the rearing, presumably strengthened by secondary infections and environmental errors, was found to decrease the daily weight gain of the pigs. However, even non-complicated M. hyopneumoniae infections acquired late in the fattening period were associated with reduced daily weight gain. That growth reduction was estimated to be at least 60 g (about 6%) after adjusting for herd, pen, initial weight and sex.     

Association between lean meat percentage and average daily weight gain in Danish slaughter pigs

Danish pigs that are within optimal weight limits and have a high lean meat percentage (LMP) obtain the best prices at slaughter. Another reason to consider the variation in LMP is the assumed association between LMP and average daily weight gain (ADG) at the individual level. The aim of this study was to test whether high ADG was associated with low LMP and vice versa. A cohort of 99 pigs from a conventional Danish herd was followed from 30kg to slaughter. The data included days in the herd, start- and end-weights, calculated ADG and LMP, reported from the abattoir. The study also included existing data from 13,057 boars from a Danish boar test station. The results of the study demonstrated a significant negative association between LMP and ADG: Pearson's correlation coefficient (r)=-0.42 (95% CI: -0.57; -0.24) (p<0.0001) for the cohort and r=-0.42 (95% CI: -0.48; -0.36) (p<0.0001) for the boars.     

Evaluation of Mycoplasma hyopneumoniae inactivated vaccine in pigs under field conditions

An inactivated vaccine prepared from broth culture supernatant of Mycoplasma hyopneumoniae with an aluminum adjuvant was evaluated in three herds (herd A: specific pathogen-free herd, herd B: high health status herd with no clinical signs of respiratory infection, herd C: low health status herd with serious epidemiological and economical problems). A total of 212 pigs from the three herds were divided into two groups. One group was injected twice with the vaccine at 4-week intervals and the other was a control group. No adverse reactions were noted following the vaccinations either systematically or locally in any of the vaccinated pigs from any of the herds. In herd A, the vaccination provided antibody response within 4 weeks after the second vaccination and antibody responses continued for more than 12 weeks. In herds B and C, the number of pigs with lung lesions, mean percentage of lung lesions, and the numbers of M. hyopneumoniae recovered from pigs at slaughter in the vaccinated group were significantly (P < 0.05) reduced compared to the control group. Furthermore, vaccination resulted in improved average daily weight gain (ADG), improved feed conversion ratio (FCR), and improved days to market weight in herd C, whereas no difference in growth performance was shown in herd B. It is suggested that the inactivated vaccine prepared from broth culture supernatant of M. hyopneumoniae is effective in reducing clinical signs and lung lesions. Also, vaccination resulted in improved growth performance in herds where clinical signs and economic losses were significant.     

A field study on the effect of the dietary use of a clinoptilolite-rich tuff, alone or in combination with certain antimicrobials, on the health status and performance of weaned, growing and finishing pigs

This study was conducted to assess the effect of dietary use of a clinoptilolite-rich tuff (Cp) on health status and performance of weaned, growing and finishing pigs and its compatibility during simultaneous oral administration of antimicrobials (AM) such as enrofloxacin (E) or salinomycin (S). Weaners (720) were assigned in 2 experimental groups and 4 subgroups based on the inclusion or not of Cp and AM in their feed (subgroups: NC, ES, Cp, Cp+ES) in order to evaluate their health status, under PWDS prevailing herd conditions. A second part of the trial aimed to the evaluation of piglet performance under conditions with minimized PWDS herd risks. For this purpose, a second set of 264 weaners were assigned in 2 groups and 4 subgroups, in a respective manner. All piglets remained on-trial until slaughtering age; Cp was incorporated in their feed at a rate of 2% from the day of weaning until slaughtering. The health status evaluation consisted in monitoring piglets for adverse effects related to Cp consumption, average daily diarrhoea scoring during weaning and mortality rate calculations throughout. Performance evaluation included individual weighing at the end of weaning, growing and fattening periods and feed consumption assessments. Average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ration (FCR) on a pen basis were further calculated. Cp ingestion was well tolerated by the piglets. Simultaneous administration of Cp and AM in feed, resulted in less severe forms of PWDS, which had a shorter clinical course (P<0.05). Mortality decreased (P<0.05) during the weaning period due to AM administration. Concerning mean pig body weight at the end of each production phase, both Cp and AM had favorable effects (P<0.05). ADG estimated for the whole observation period was improved (P<0.05) by Cp-use along with AM. FCR improvements (P<0.05) were noticed during the different stages of growth due to AM or Cp administration, while Cp/AM interaction was noticed only at weaning (P<0.05).     

Biosecurity in 116 Danish fattening swineherds: descriptive results and factor analysis

Biosecurity measures are important for the herd's protection against diseases and also to provide nationwide protection against the introduction of exotic diseases. In this paper, we describe the farmers’ choices and routines regarding biosecurity in Danish fattening herds.

Overall, 116 Danish swine fattening herds in three areas of different pig density were interviewed.

Of these herds, 78% purchased weaners from one sow herd only, whereas 10% purchased from >5 sow herds during 1 year. Large herds (>500 finishers) purchased weaners more often than smaller herds (≤500 finishers). Only two swine producers purchased weaners from a market. Almost all herds (95%) received weaners from one sow herd at one time, and only one herd received from >5 sow herds in one batch. Twenty-one percent did not use an effective barrier between the loading area and the stables when delivering pigs for slaughter. Entry rooms (in which clothing and boots are changed) were common at the farm, and the numbers of visitors were generally low (<10 visitors a year).

Factor analysis was performed to find underlying structures of the biosecurity measures in the herd; four factors were chosen (eigenvalue > 3.10). A site scoring high on factor 1 was a large SPF herd, which received weaners from a single source, had biosecurity requirements for the transport vehicles, and had a high level of biosecurity for visitors. A site scoring high on factor 2 was a multi-site farm, which had personnel working on more than one of the sites, only received weaners from one sow herd, had delivering herds placed close to the participating site, and transported animals themselves. A site scoring high on factor 3 was a site which hired commercial transport for slaughter, was situated far from the abattoir and had a high level of biosecurity when loading pigs. A production site scoring high on factor 4 was a large site, which used all-in/all-out management, washed and disinfected between each group, and purchased many weaners.     

Looking for new approaches for the use of serology in the context of control programmes against pig salmonellosis

Most swine Salmonella national control programmes in Europe have been based on the categorization of herds according to risk levels based on serological results. However, none of the non‐Scandinavian countries have reported of any significant success on Salmonella infection reduction in fattening pigs or the number of human cases attributable to pigs or pork. The limited accuracy of the tests used, the small number of animals sampled and the likely lack of herd representativeness of the samples used could be major factors affecting the suitability of these programmes. Focusing on minimizing Salmonella shedding at slaughter appears more important to prevent human infections than focusing on detection of seropositive pigs/herds at this stage. This study assessed whether performing on‐farm serology may help to predict shedding at slaughter. Between 2010 and 2016, pigs from six cohorts from a Salmonella‐positive herd were bled at 30, 60 and 90 days on fattening and before slaughter, and faecal samples collected at slaughter. Serology on days 60, 90 and before slaughter predicted somewhat shedding at slaughter with no significant differences among them. Pigs with higher OD% values at these point times would have higher risk of shedding when arriving to slaughter. The probability of shedding for a pig sampled on day 90 and showing an OD% value of 10 was 43%, and the risk increased up to 65% if the OD% was 40. Concluding, on‐farm serology may help to determine to some extent the risk of Salmonella shedding at slaughter from seropositive fattening units, which would allow for prompt on‐farm and slaughter interventions to reduce the likelihood of slaughter contamination with Salmonella.     

育肥猪肠道疾病的特点与危害

育肥猪肠道疾病问题是当前规模化猪场最常见的问题之一,其病因复杂导致防控难度增加,常见发病原因分为病原性因素与非病原性因素两种。病原性因素如病毒、细菌、寄生虫等;非病原性因素如生产管理、饲料营养、应激等外部环境引起。在我国当前的养殖环境下,病原性因素引起的猪肠道疾病占据大多数,常见的导致育肥猪腹泻的疾病的病原微生物如细胞内劳森菌(引起猪回肠炎)、猪密螺旋体痢疾、大肠杆菌、沙门氏菌、寄生虫及部分病毒性疾病等的感染在我国的猪场广泛存在,这些病原微生物会导致育肥猪群发生急性或慢性消耗性腹泻,使育肥猪发生成活率降低、饲料报酬下降、生长速度减缓、僵猪和残次猪比例升高等情况,给生长育肥猪的正常生长和出栏造成了很大的危害。文章通过对育肥猪肠道疾病的发病原因、发病特点与危害以及防控等方面进行了简要的阐述,以供参考。     

Actinobacillus (Haemophilus) pleuropneumoniae infections in swine: serological investigations and vaccination trials in combination with environmental improvements

The present investigation comprised six integrated herds (100-150 sows each) and one specialized fattening herd. Serologic tests by ELISA were performed on blood samples from piglets and growing pigs during various rearing phases in order to determine the presence of Actinobacillus infection and to estimate the age of the animals at onset of the disease. Using this information, herd-specific vaccination programs were designed against Actinobacillus pleuropneumoniae serotype 2. The weaned piglets in the integrated herds were vaccinated twice before being moved to the fattening unit. In the specialized fattening herd, the pigs were vaccinated on arrival at the growing unit and just before transfer to the finishing unit. The frequencies of chronic pleuritis at slaughter demonstrated that a vaccination program adapted to the herd-specific problem, in combination with environmental improvements, reduces the prevalence of chronic pleuritis. On the other hand, only a moderate reduction of the prevalence of chronic pleuritis occurred as a result of vaccination if no environmental improvements were made. In two of the herds during the vaccination period, the number of feeding days and food consumption decreased, while growth per day increased. There was also an apparent correlation between higher serum titres and a decreased prevalence of pleuritis at slaughter in three of the herds.     

Non-infectious factors associated with macroscopic and microscopic lung lesions in slaughter pigs from farrow-to-finish herds

A cross-sectional epidemiological study was conducted in 150 randomly selected farrow-to-finish herds to investigate which non-infectious factors might act as risk indicators for the prevalence and severity of macroscopic and microscopic lung lesions in slaughter pigs. Data were collected during herd visits through inspections of the pigs and through interviews with the farmers. Macroscopic lung lesions of pneumonia and pleuritis were recorded at slaughter from 25 pigs per herd, and microscopic lung lesions of lymphohistiocytic infiltration were recorded from 10 pigs per herd. The median herd level prevalences were 24 per cent for pneumonia, 16 per cent for pleuritis and 60 per cent for lymphohistiocytic infiltration. Pneumonia lesions were negatively associated with pleuritis lesions and positively associated with lymphohistiocytic infiltration. Pleuritis lesions were negatively associated with lymphohistiocytic infiltration. The prevalence and the severity of pneumonia lesions were increased by a high frequency of purchasing gilts and by a slaughter date in January to February. The presence of a growing unit also increased the severity of pneumonia. The prevalence and the severity of pleuritis lesions were higher when there were more pig herds in the municipality, and when there were poor biosecurity measures, and their prevalence was increased by a slaughter date in January to February, and their severity by a slaughter date in March to April. An increase in the airspace stocking density in the finishing unit also increased the prevalence of pleuritis. The prevalence and the severity of lymphohistiocytic infiltration in the lung tissue were higher in herds purchasing gilts. Pigs raised in pens with slatted floors were also at higher risk of more severe lesions of lymphohistiocytic infiltration.