A meta-analysis comparing the effect of PCV2 vaccines on average daily weight gain and mortality rate in pigs from weaning to slaughter

The aim of this investigation was, through a meta-analysis, to review the published literature concerning the effect of PCV2 vaccination on the average daily weight gain (ADG) and on the mortality rate in pigs from weaning to slaughter. The review was restricted to studies investigating the effect of vaccines against PCV2 published from 2006 to 2008, identified using computerised literature databases. Only studies that met the following criteria were included: commercial vaccines were used, pigs or pens were assigned randomly to vaccination versus control groups in herds naturally infected with PCV2, and vaccinated and non-vaccinated pigs were housed together. Furthermore, it was a requirement that sample size, age at vaccination, and production period were stated. The levels of ADG and mortality rate had to be comparable to those seen in modern intensive swine production. In total, 107 studies were identified; 70 were excluded because they did not fulfil the inclusion criteria and 13 were identical to results published elsewhere. A significant effect of PCV2 vaccination on ADG was found for pigs in all production phases. The largest increase in ADG was found for finishing pigs (41.5g) and nursery-finishing pigs (33.6g) with only 10.6g increase in the nursery pigs. Mortality rate was significantly reduced for finishing pigs (4.4%) and nursery-finishing pigs (5.4%), but not for nursery pigs (0.25%). Herds negative for PRRS had a significantly larger increase in ADG compared to herds positive for PRRS. The PRRS status had no effect on mortality rate.     

A field evaluation of two vaccines against Mycoplasma hyopneumoniae infection in pigs

Background

A field trial was carried out with two Mycoplasma hyopneumoniae vaccines in order to investigate the benefit of vaccination under field conditions in modern Danish pig production facilities with pigs being positive for M. hyopneumoniae. The M. hyopneumoniae infection of the herd was confirmed through blood samples that were positive for antibodies against M. hyopneumoniae combined with gross lesions of the lungs related to M. hyopneumoniae at slaughter and detection of M. hyopneumoniae by polymerace chain reaction in these lesions.

Results

A total of 2,256 pigs from two herds were randomly divided into three groups. Group 1 received 2 mL ThoroVAX^®VET, Group 2 received 1 mL Ingelvac^®MycoFLEX, and Group 3 was a non-vaccinated control group. The vaccination was performed by a person who was not involved in the rest of the trial and vaccination status thereby blinded to the evaluators.The prevalence of lung lesions related to M. hyopneumoniae were significantly lower for pigs vaccinated with ThoroVAX^®VET but not for pigs vaccinated with Ingelvac^®MycoFLEX^®, when compared to non-vaccinated pigs. There was no significant effect of vaccination on growth rate, antibiotic consumption or mortality.

Conclusion

This trial demonstrated that vaccination with Thoro^®VAX VET was effective in reducing the prevalence of lung lesion in pig units infected with M. hyopneumoniae.     

猪支原体肺炎疫苗研究进展

猪肺炎支原体是引起猪支原体肺炎的病原,该病呈世界性流行,死亡率虽然不高,但由于长期性和消耗性的流行,使饲料转化率降低,并引起猪的多种并发病,是造成养猪业经济损失最重要的疾病之一.目前疫苗免疫是预防猪支原体肺炎和减少经济损失最有效的手段之一,猪支原体肺炎疫苗主要有灭活疫苗和减毒活疫苗.这些疫苗已得到广泛的应用,并在临床上...     

Evaluation of antibody formation, daily weight gain and meat quality after vaccination of piglets against Mycoplasma hyopneumoniae

A Mycoplasma hyopneumoniae vaccine (Respisure, Pfizer AH) was tested for its effects on antibody formation, daily weight gain (DWG) in different growing periods, lung lesions and quality of meat (chemical composition, physicochemical properties and fatty acid composition). Two groups of conventional piglets were used for the investigation. One group of 11 females and 11 males was vaccinated intramuscularly at the age of 1 and 3 weeks. The other group of 22 piglets was left nonvaccinated as control. The results showed that antibodies against M. hyopneumoniae in the vaccinated group had been formed 14 days after the second vaccination and remained present till the end of the study at 147 days of age. In the nonvaccinated group, seroconversion started at 49 days of age and by the end of the study 10 out of 22 pigs had become seropositive. Vaccinated pigs achieved significantly higher daily weight gain (+30 g) and finishing body weight (+6.04 kg) than the nonvaccinated animals. In addition, the vaccinated pigs showed lesions involving 3.27% of the lung surface in average, while in the nonvaccinated pigs 9.04% of the lung surface was affected. Investigation of meat quality showed that the longissimus dorsi muscle of vaccinated pigs contained significantly lower percentage of fat (-0.63%) and its tryptophan/hydroxyproline ratio was significantly lower (-23.57) in comparison with the control animals. In addition, some other parameters also showed a favourable tendency, e.g. lean meat percentage was 0.91% higher, the protein content of the longissimus dorsi muscle was 0.35% higher, its water-binding capacity was also higher by 0.78%, its monounsaturated fatty acid concentration was 2.97% lower, while its polyunsaturated fatty acid content was 1.65% higher in the vaccinated pigs than in the nonvaccinated animals.     

Control of Mycoplasma hyopneumoniae infections in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. The organism adheres to and damages the ciliated epithelium of the respiratory tract. Affected pigs show chronic coughing, are more susceptible to other respiratory infections and have a reduced performance. Control of the disease can be accomplished in a number of ways. First, management practices and housing conditions in the herd should be optimized. These include all-in/all-out production, limiting factors that may destabilize herd immunity, maintaining optimal stocking densities, prevention of other respiratory diseases, and optimal housing and climatic conditions. Strategic medication with antimicrobials active against M. hyopneumoniae and, preferably, also against major secondary bacteria may be useful during periods when the pigs are at risk for respiratory disease. Finally, commercial bacterins are widely used to control M. hyopneumoniae infections. The main effects of vaccination include less clinical symptoms, lung lesions and medication use, and improved performance. However, bacterins provide only partial protection and do not prevent colonization of the organism. Different vaccination strategies (timing of vaccination, vaccination of sows, vaccination combined with antimicrobial medication) can be used, depending on the type of herd, the production system and management practices, the infection pattern and the preferences of the pig producer. Research on new vaccines is actively occurring, including aerosol and feed-based vaccines as well as subunit and DNA vaccines. Eradication of the infection at herd level based on age-segregation and medication is possible, but there is a permanent risk for re-infections.     

“猪地方性肺炎及其防治控制”专栏四：猪肺炎支原体的防治措施

猪肺支原体是猪地方性肺炎的主要病原体,其普遍存在于世界各地,会给养猪业造成巨大的经济损失。此病原体感染猪后通常黏附于猪呼吸道纤毛上皮,并会造成纤毛上皮的损伤。猪感染后主要表现为慢性咳嗽症状、容易发生其他呼吸道感染和生产性能下降。该病的控制可通过多种措施实现,首先应该完善管理措施,改善畜舍饲养环境,这包括实行全出/全进的饲养方式、减少会破坏群体免疫水平的因素、维持最佳的饲养密度、防止其他呼吸道疾病的感染,以及提供最佳的畜舍及环境条件。其次,当猪群处于呼吸道疾病感染的威胁之下时,战略性使用能够有效地预防猪肺炎支原体和最好还能预防大多数继发感染细菌的药物对预防本病非常有效。最后,商用疫苗已被广泛地用来控制猪肺炎支原体感染,接种疫苗的优点在于其能够减少临床症状、减轻肺脏损伤、减少药物的使用和提高猪群的生产性能。但是,疫苗仅能提供部分保护作用,并且不能防止病原体在猪体内的定殖。因此,应根据猪群的种类、猪场的生产系统和管理体制、感染的类型及猪农的喜好选择不同的免疫策略（免疫时机、母猪免疫、免疫接种再结合抗菌素治疗）。新疫苗正在紧锣密鼓的研究之中,如气雾苗、通过饲料接种的疫苗以及亚单位苗和DNA疫苗。按年龄进行隔离饲养和药物治疗在猪群水平上根除猪肺炎支原体感染是可能的,但该病复发的威胁将永久存在。     

猪肺炎支原体的防治措施

猪肺支原体是猪地方性肺炎的主要病原体,其普遍存在于世界各地,会给养猪业造成巨大的经济损失.此病原体感染猪后通常黏附于猪呼吸道纤毛上皮,并会造成纤毛上皮的损伤.猪感染后主要表现为慢性咳嗽症状、容易发生其他呼吸道感染和生产性能下降.该病的控制可通过多种措施实现.首先应该完善管理措施.改善畜舍饲养环境,这包括实行全出/全进的饲养方式、减少会破坏群体免疫水平的因素、维持最佳的饲养密度、防止其他呼吸道疾病的感染,以及提供最佳的畜舍及环境条件.其次,当猪群处于呼吸道疾病感染的威胁之下时,战略性使用能够有效地预防猪肺炎支原体和最好还能预防大多数继发感染细菌的药物对预防本病非常有效.最后,商用疫苗已被广泛地用来控制猪肺炎支原体感染,接种疲苗的优点在于其能够减少临床症状、减轻肺脏损伤、减少药物的使用和提高猪群的生产性能.但是,疫苗仅能提供部分保护作用,并且不能防止病原体在猪体内的定殖.因此,应根据猪群的种类、猪场的生产系统和管理体制、感染的类型及猪农的喜好选择不同的免疫策略(免疫时机、母猪免疫、免疫接种再结合抗菌素治疗).新疫苗正在紧锣密鼓的研究之中.如气雾苗、通过饲料接种的疫苗以及亚单位苗和DNA疫苗.按年龄进行隔离饲养和药物治疗在猪群水平上根除猪肺炎支原体感染是可能的,但该病复发的威胁将永久存在.     

The effect of daily energy intake on growth rate and composition of weight gain in pigs

An experiment with 29 crossbred female growing pigs (Dutch Landrace × Dutch Yorkshire) was carried out to measure the effect of daily energy intake on growth rate, N retention (according to the balance method) and composition of the weight gain. The weight gain composition was analysed by slaughtering pigs at regular intervals between 25 and 110 kg live weight. Two levels of daily energy intake, at an adequate protein intake, were used, and pigs on both treatments were slaughtered at the same age.Differences in daily energy intake affected growth rate and composition of the weight gain. Restriction of the daily energy intake by 20% caused a 15% lower live weight gain and a 12% lower N retention. Carcass muscle growth was 8% lower and fatty tissue growth was lower by 28%. Growth of bone was unaffected. Chemical analysis of different parts of the body revealed that reducing the daily energy intake by 20% caused an 8% lower protein deposition and a 28% lower fat deposition in the total body. However, there were differences between different anatomical parts of the body.Efficiency of pig meat production is discussed in relation to the effects of energy supply on weight gain composition.     

Field efficacy of a combined use of Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae vaccines in growing pigs

The effectiveness of simultaneous administration of commercial Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae vaccines was tested in an indoor commercial piggery which had experienced continuing respiratory-disease problems confirmed as due to both of these pathogens. Piglets were randomly assigned in equal numbers to vaccination and control groups, and each vaccine was administered at a separate site to assigned piglets at two and four weeks of age. Live weight of vaccinates immediately prior to slaughter was 2.49 kg higher (p = 0.04) than for controls at equal mean slaughter age of 132 days. Average daily gain (ADG) from 16 weeks to slaughter of vaccinates was also significantly higher (33 g/day) than in controls (p = 0.05). Daily gain was not significantly different in younger age groups. Active enzootic pneumonia lesions were more likely in control than in vaccinated pigs. There were no significant differences between vaccination groups with regard to severity of pleurisy or presence of pleuropneumonia lesions at slaughter. Log-linear modelling was used to test the statistical association between vaccination, enzootic pneumonia lesions, pleurisy lesions and pleuropneumonia lesions. It showed a reduction in the severity of enzootic pneumonia lesions for vaccinated pigs, and the presence of pleuropneumonia lesions increased the likelihood of pleurisy lesions. No other association was significant, and no evidence of synergy between the vaccines in influencing lesion severity for pleuropneumonia was detected (within the limitations set by the trial design).     

Systemic and local immune response in pigs intradermally and intramuscularly injected with inactivated Mycoplasma hyopneumoniae vaccines

The systemic and respiratory local immune response induced by the intradermal administration of a commercial inactivated Mycoplasma hyopneumoniae whole-cell vaccine (Porcilis^® MHYO ID ONCE – MSD AH) in comparison with two commercial vaccines administered via the intramuscular route and a negative control (adjuvant only) was investigated. Forty conventional M. hyopneumoniae-free pigs were randomly assigned to four groups (ten animals each): Group A = intradermal administration of the test vaccine by using the needle-less IDAL^® vaccinator at a dose of 0.2 ml; Group B = intramuscular administration of a commercially available vaccine (vaccine B); Group C = intramuscular administration of the adjuvant only (2 ml of X-solve adjuvant); Group D = intramuscular administration of a commercially available vaccine (vaccine D). Pigs were vaccinated at 28 days of age. Blood and bronchoalveolar lavage (BAL) fluid samples were collected at vaccination (blood only), 4 and 8 weeks post-vaccination. Serum and BAL fluid were tested for the presence of antibodies by ELISA test. Peripheral blood monomorphonuclear cells (PBMC) were isolated to quantify the number of IFN-γ secreting cells by ELISpot. Moreover, cytokine gene expression from the BAL fluid was performed. Total antibodies against M. hyopneumoniae and specific IgG were detected in serum of intradermally and intramuscularly (vaccine B only) vaccinated pigs at 4 and 8 weeks post-vaccination. M. hyopneumoniae specific IgA were detected in BAL fluid from vaccinated animals (Groups A and B) but not from controls and animals vaccinated with the bacterin D (p < 0.05). Significantly higher gene expression of IL-10 was observed in the BAL fluid at week 8 post-vaccination in the intradermally vaccinated pigs (p < 0.05). The results support that the intradermal administration of an adjuvanted bacterin induces both systemic and mucosal immune responses. Moreover, the intramuscularly administered commercial vaccines each had a different ability to stimulate the immune response both systemically and locally.     

Exploratory field study on Mycoplasma hyopneumoniae infection in suckling pigs

The present study focused on Mycoplasma hyopneumoniae (M. hyopneumoniae) detection by nPCR in nasal swabs of 507 suckling pigs. These animals came from 69 sows (from 1 to 8 parity number) of a farrow-to-finish herd with Enzootic Pneumonia (EP) problems at finishing stages. At 1 and 3 weeks of age (still in the farrowing units), nasal swabs and blood samples were taken from all piglets. Moreover, from these 507 animals, 37 randomly selected pigs were necropsied at 3 weeks of age. From those necropsied pigs, M. hyopneumoniae presence was tested in bronchial and tonsillar swabs. At 1 week post-farrowing, blood samples from sows were collected and used to detect M. hyopneumoniae antibodies. From the 69 analysed sows, 19 (27.5%) were seropositive. Global percentage of pigs with M. hyopneumoniae detection in nasal swabs at 1 and 3 weeks of age was 1.5% (8 out of 507) and 3.8% (19 out of 507), respectively. From these nPCR positive pigs, 89% (24 out of 27) were seronegative and 11% were seropositive. From necropsied animals, the pathogen DNA was detected in two pigs at bronchus level and in another pig at tonsil. In this study, sow parity was not statistically related with sow seropositivity and piglet colonization. These results confirm that M. hyopneumoniae infection may be detected not only in nasal cavities of naturally infected suckling piglets but also at their low respiratory tract airways. Our results suggest that M. hyopneumoniae detection in lower and upper respiratory tract could be an indicator that respiratory problems associated to EP may start relatively early in the production system. In consequence, sow-to-piglet and/or piglet-to piglet transmission in farrowing barns should not be underestimated.     

Seroepidemiology of Mycoplasma hyopneumoniae in pigs from farrow-to-finish farms

A prospective study was carried out on three intensive farrow-to-finish farms. The aims were to estimate the incidence of Mycoplasma hyopneumoniae infection, to determine when pigs become infected and the pattern of transmission of infection and to verify the relationship between seroconversion and clinical signs. One batch of pigs per farm was followed from farrowing-to-slaughter. Blood samples were taken at 10, 27, 70, 94, 125 and 147 days of age, from 44, 48 and 44 pigs per farm. Colostrum and blood samples were also taken from the sows. Animals were checked clinically once a week and coughing rates were recorded. Antibodies against M. hyopneumoniae were detected by a blocking ELISA. At 27, 70 and 94 days of age most pigs on the three farms were seronegative, suggesting that no circulation of M. hyopneumoniae occurred during the growing period. Thereafter, a high proportion of pigs seroconverted, indicating that infection occurred soon after the transfer of the animals to the finishing houses. Differences were detected between farms in the incidence of seroconversion. Seropositive pigs were widely distributed among the finishing pens, suggesting that in addition to direct contact, other methods of transmission, such as indirect or airborne transmission, may have been important. Coughing started at around the same time as seroconversion. The results showed that the critical period for the transmission of M. hyopneumoniae is around the beginning of the finishing period, when pigs have low concentrations of antibodies against the agent.     

Interaction between single-dose Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus vaccines on dually infected pigs

The objective of this study was to determine the effects of Mycoplasma hyopneumoniae and/or porcine reproductive and respiratory syndrome virus (PRRSV) vaccination on dually infected pigs. In total, 72 pigs were randomly divided into nine groups (eight pigs per group), as follows: five vaccinated and challenged groups, three non-vaccinated and challenged groups, and a negative control group. Single-dose vaccination against M. hyopneumoniae alone decreased the levels of PRRSV viremia and PRRSV-induced pulmonary lesions, whereas single-dose vaccination against PRRSV alone did not decrease nasal shedding of M. hyopneumoniae and mycoplasma-induced pulmonary lesions in the dually infected pigs. The M. hyopneumoniae challenge impaired the protective cell-mediated immunity induced by the PRRSV vaccine, whereas the PRRSV challenge did not impair the protective cell-mediated immunity induced by the M. hyopneumoniae vaccine. The present study provides swine practitioners and producers with efficient vaccination regimes; vaccination against M. hyopneumoniae is the first step in protecting pigs against co-infection with M. hyopneumoniae and PRRSV.     

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.     

环丙沙星在支原体肺炎猪体内的药动学

18头健康杜洛克×长白×大白杂交猪,分3组,每组6头,通过气管内接种含有猪肺炎支原体的病肺悬液复制疾病模型后,以5.0mg/kg静注、肌注及内服给药进行环丙沙星药物动力学研究.高效液相色谱法测定血浆中药物浓度.MCPKP药物动力学程序处理药时数据.结果显示感染猪静注给药的药时数据适合二室开放模型,t1/2α为0.59 h,t1/2β为3.52 h,Vd(area)为3.21 L/kg,ClB为0.645 L/(ks·h).感染猪肌注和内服给药后的药时数据则适合一级吸收一室模型,t1/2ka分别为0.09、0.31 h;tmax分别为0.46、1.41 h;Cmax分别为1.67、0.35 mg/L;F分别为97.30%、34.66%.上述结果表明,支原体性肺炎对环丙沙星静注给药在猪体内的分布有一定影响,但对其消除过程的影响不大;与健康猪比较,感染猪肌注给药的峰浓度、药时曲线下面积及生物利用度均显著提高,而内服给药的峰浓度、药时曲线下面积及生物利用度均显著降低.     

Dynamics and persistence of Mycoplasma hyopneumoniae infection in pigs

The purpose of this study was to describe the dynamics (shedding and transmission) of Mycoplasma hyopneumoniae infection within a population of swine and to determine the duration of the infection (persistence) through the identification of the agent in bronchial samples. Sixty-three 2-month-old pigs were used in this study. The pigs (n = 28) were experimentally infected by the intratracheal route with M. hyopneumoniae and considered as seeder pigs. The remaining pigs (n = 32) were not inoculated and randomly allocated to 2 different groups: direct contact exposure pigs (n = 12) and indirect contact exposure pigs (n = 20). Blood samples and nasal swabs were collected throughout the study on days 0, 28, 35, 42, 49, 63, 91, and 119 postinfection. To assess the duration of M. hyopneumoniae infection, 9 seeder and 6 contact exposure pigs were slaughtered at days 155 (group 1), 170 (group 2), and 185 (group 3) postinfection. Direct contact pigs showed evidence of infection on day 28 by polymerase chain reaction (PCR) and on day 35 by serology. The indirect contact exposure pigs presented a very delayed and slow seroconversion pattern; they did not present evidence of transmission until 42 d after the infection of seeder pigs. Identification of M. hyopneumoniae in bronchial swabs was confirmed by nested-PCR from days 155 to 185 postinfection. At the last slaughter date, 77.7% and 100% of the seeders and contact exposure pigs, respectively, tested positive. The results of this study reconfirmed direct infection of M. hyopneumoniae and suggest that indirect transmission can occur in a population. Finally, duration of the infection in this study was longer than previously described.     

No overall relationship between average daily weight gain and the serological response to Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae in eight chronically infected Danish swine herds

The association between the average daily weight gain (from approximately 4 to 20 weeks of age) and the serological responses to respiratory infections was examined in a longitudinal study including 825 pigs from eight chronically infected herds. Pigs were bled every 4th week (starting from approximately 4 weeks of age), and sera were analyzed for antibodies to Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae serotypes 2, 5-7 and 12.Mixed analysis of covariance analyzed the relationship between the average daily weight gain and a categorical variable defining seroconversion as none, early or late as compared to the median time (estimated across herds) of seroconversion for the particular pathogen. The variables "gender", "weight at an approximate age of 4 weeks" and "time" (defining the exact length of the follow-up period), were included as explanatory variables, and "litter" and "herd" were included as explanatory random variables. The individual pig was the unit of concern.The variable defining time at seroconversion was not significantly associated with the average daily weight gain, when evaluating models across all eight herds. The apparent lack of effect could be because most pigs included in the study were subclinically infected, or because a temporary negative influence of the infections is hidden due to an increased growth in the period following infection.In conclusion, at least in these eight herds, seroresponses to M. hyopneumoniae and A. pleuropneumoniae could not be used to predict the effect of the pathogens on the daily weight gain.     

Protective effects of an oral microencapsulated Mycoplasma hyopneumoniae vaccine against experimental infection in pigs.

Oral microencapsulated Mycoplasma hyopneumoniae vaccines were tested for their ability to prevent mycoplasmal pneumonia in pigs. Eighteen four-week-old specific pathogen free pigs were divided into six groups of three. Each pig of groups 1 to 4 was inoculated intramuscularly with formalin-inactivated M hyopneumoniae in adjuvant and boosted orally 14 days later with four different microencapsulated vaccine microspheres. Group 5 was used as a positive control. All 15 pigs of groups 1 to 5 were challenged at 28 days after the first vaccination by an intratracheal inoculation of pneumonic lung suspension. The three pigs of group 6 were used as a negative control. All four vaccinated groups showed some protection when challenged, but the protection was more solid in pigs boosted with vaccine D (group 4) which contained less porcine serum in the microsphere. The study indicates that oral vaccination with M hyopneumoniae could play a role in prevention and eradication of mycoplasmal pneumonia in the pig.     

Mycoplasma hyopneumoniae colonization of pigs sired by different boars

Differences in Mycoplasma hyopneumoniae colonization were evaluated in experimentally inoculated pigs sired by 3 different boars of the same genetic line. Forty-six pigs were used, including a treatment group and positive and negative control groups. The pigs were intratracheally inoculated with an M. hyopneumoniae suspension or with Friis media as a placebo. To evaluate differences in the magnitude of colonization during a 35-day period, nasal and tracheal swabs were collected weekly and tested by nested polymerase chain reaction (N-PCR). Temperature, weight and circulating antibodies were measured for 35 days. At 11 and 35 d postinoculation the pigs were necropsied and macroscopic and microscopic lesions were determined. A section of bronchus was tested by the indirect immunofluorescence test (IFAT), scanning electron microscopy (SEM) and N-PCR. The N-PCR results from the nasal and tracheal swabs showed that the pigs sired by one boar (B3) had a distinctive colonization pattern, different from that of the pigs from the other 2 boars and from the positive controls. SEM studies demonstrated that at 35 d postinoculation a higher proportion of B3 pigs had lower numbers of mycoplasmas attached to the cilia compared with B1 and B2 offspring. No significant differences were observed in temperature and weight gain among groups by ANOVA; however, with use of a 2 × 2 table, temperature differences were observed between pigs sired by boars B1 and B2 at 4 d postinoculation. No pigs seroconverted, showed gross or microscopic lesions, or had positive IFAT results. These results provide evidence of differences in patterns of colonization between pigs sired by different boars, suggesting a possible genetic effect.