Reproductive productivity measurements in Japanese swine breeding herds

To set productivity standards and targets, and investigate inter-relationships between key measurements in swine breeding herds, farm productivity measurements were analyzed on 87 Japanese commercial farms in 14 prefectures. The 87 herds were ranked on the basis of number of pigs weaned per mated female per year (PWMFY), and 23 herds in the upper 25th percentile of this ranking were designated as high-performing farms. Productivity measurements on the high-performing farms were compared with values for the remaining farms. The high-performing farms had shorter farrowing intervals, greater litters per mated female per year (LMFY), greater pigs weaned per sow (PWS), and greater mean parity of culled sows than the remaining farms (P<0.01). No difference in lactation duration was found between the two groups (P>0.10). For both farm groups, correlations of key reproductive measurements were determined. Lactation duration was not correlated with LMFY, PWS and PWMFY on the high-performing farms, while short lactation duration was correlated with greater LMFY and PWMFY on the remaining farms (P<0.01). In contrast to lactation duration, farrowing interval was correlated with PWS on the high-performing farms, but not on the remaining farms. Mean parity of culled sows were correlated to PWS and pigs born alive per sow on the high performing farms, but not with any measurements on the remaining farms. These results suggest that high-performing farms have used different herd management from the remaining farms.     

Sow line differences in heat stress tolerance expressed in reproductive performance traits

The objectives of this study were 1) to investigate if there were differences in the relation between temperature and reproductive performance traits in 2 different sow lines, a Yorkshire line producing mainly in temperate climates and a Large White line producing mainly in warm climates, and 2) to determine the upper critical temperature (UCT) for the reproductive performance of these 2 lines. Sows are exposed to heat stress when temperature exceeds the UCT of the thermo-neutral zone. Data included 32,631 observations on reproductive performance from 11,935 sows on 20 farms in Spain, collected from 2003 to 2005. Sows belonged to 2 different purebred sow lines, named D (Yorkshire sow line, producing mainly in temperate climates) and I (Large White sow line, producing mainly in warm climates). Only first insemination records per parity were used and were combined with the maximum outside temperature at day of insemination. Upper critical temperatures were studied for 3 reproduction traits: farrowing rate (0 or 1), litter size (range from 1 to 25), and total number of piglets born per first insemination (combination of farrowing rate and litter size, range from 0 to 25). Data were corrected for fixed effects, which included parity, service sire, and an interaction between farm and year. Corrected data were used as observations in the models to study the effect of outside temperature on reproductive performance. Two models were compared for goodness of fit: a linear regression model and a plateau-linear model with the plateau representing the thermo-neutral zone and a linear decrease above that zone. Farrowing rate of I-line sows was not affected by temperature. For litter size and total number born per first insemination of I-line sows no UCT could be estimated. These traits were linearly affected by temperature. For all 3 reproduction traits of the D-line the best model was the plateau-linear model; the UCT for the D-line sows was estimated to be 19.2 degrees C for farrowing rate, 21.7 degrees C for litter size, and 19.6 degrees C for total number born per first insemination. The decrease in reproductive performance of I-line sows with increasing outside temperature was less than in D-line sows. From this study it can be concluded that there are differences in heat stress tolerance between sow lines as measured by the differences in reproductive performance. These differences are an indication of genetic differences in heat stress tolerance in sow lines.     

某猪场母猪繁殖性能预测和logistic回归分析

为了衡量猪场生产效率，研究根据某公司7个分场繁殖母猪2016—2019年的生产记录，运用时间序列分析预测母猪繁殖性能的未来短期趋势，发现母猪未来一段时间的生产性能不会出现较大变动，与实际值较吻合，说明时间序列对母猪繁殖性能方面的预测，有较强的实用价值；再通过建立logistic回归模型，进行模型分析以寻找影响母猪繁殖性能的关键因素，进一步确定胎次是影响母猪繁殖性能重要因素。并且该模型还可用于其他生产指标的因素分析，可以为提高母猪群繁殖性能提供科学依据。     

Management factors associated with farrowing rate in commercial sow herds in Ontario

The objectives of this study were to determine associations between low farrowing rate and various management factors in sow herds. In 30 sow herds, a management survey, breeding observations, semen evaluation, and semen storage temperature monitoring were completed. Herds with an average farrowing rate of < 85% were classified as low farrowing rate herds while those with an average farrowing rate of ≥ 85% were classified as good farrowing rate herds. Low farrowing rate herds were more likely than good farrowing rate herds to move boars into gilt pens for estrus detection, breed a high proportion of sows by artificial insemination (AI) only, start heat detection 3 d post-weaning, wipe the vulva prior to breeding, and use “hands-free” AI devices.     

Influence of farm application of oregano on performances of sows

This study was performed in a large commercial herd in eastern Europe to test the effect of oregano feed supplementation. Sows were studied in a unit where alternate farrowing groups were given diets containing 1000 ppm oregano in the prefarrowing and lactation diet. Oregano-treated groups showed a lower (P = 0.003) annual sow mortality rate, a lower (P = 0.03) sow culling rate during lactation, an increased (P = 0.01) subsequent farrowing rate, and more (P = 0.05) live-born piglets per litter compared with the nontreated sows. The conclusion was that dietary oregano supplementation improved the reproductive performance of sows in this herd.     

Welfare Index and Reproductive Performance in the Sow

To study the relationship between on-farm welfare and reproductive performance in the sow, the TGI 35L Animal Needs Index was modified for use in Finnish pig production. The modified index had a maximal total score of 100. It was comprised of six categories: 'locomotion' (maximal score 21 for dry sows and 11 for lactating sows), 'social interaction' (12/8), 'floor quality' (16/9), 'stable climate' (16/21), 'feeding' (16/23) and 'health and stockmanship' (19/29). Index scorings were performed separately in farrowing, breeding and gestation units on 28 representative Finnish sow farms. One-year production parameters were collected. Multiple linear regression was used for statistical analysis. Total ANI-points varied between 36.5-68.0 for lactating and 39.5-86.0 for dry sows. Litter size increased with increasing scores for 'feeding' in the dry sow unit. Controlling for breed, high scores for 'health and stockmanship' and 'floor quality' shortened the reproductive cycle, probably because of good leg health. The number of weaned piglets per sow per year (PSY) increased with increasing scores for dry sow 'health and stockmanship', 'floor quality' and an interaction of 'feeding' in the farrowing and mating units. PSY increased with decreasing scores for farrowing pen 'climate'. High-quality floors and stockmanship appear to correlate positively with reproductive performance in the sow. Effects of a welfare-promoting feeding strategy on reproduction are contradictory.     

Salmonella in sows: a longitudinal study in farrow-to-finish pig herds

Besides finishing pigs, sows are also believed to be important in the epidemiology of Salmonella. The study objective was to investigate the prevalence of Salmonella excretion in sows during an entire reproductive cycle. In 3 farrow-to-finish herds, groups of 34, 40 and 32 sows, respectively, were sampled serially. Faecal samples, environmental swabs and feed samples were taken and submitted to a qualitative Salmonella isolation. All isolates were characterised using RAPD and a representative number of isolates was serotyped. The prevalence of Salmonella excretion was < 10% during gestation, around farrowing and during lactation, but a significant increase in the number of Salmonella excreting sows was found in herds A (p < 0.01) and C (p = 0.02) after weaning. S. Infantis was the most prevalent serotype in herd A, S. Derby in herds B and C. Except for the S. Infantis group in herd A, all isolates within each group of the RAPD analysis belonged to the same serotype. Three sows in herd A and 1 sow in herd C shed different serotypes at different time points. The present results indicate that sows can maintain Salmonella infections in farrow-to-finish herds and that culled sows, leaving the herd after weaning, may constitute a substantial risk for contamination of their carcasses with Salmonella.     

Low reproductive performance and high sow mortality in a pig breeding herd: a case study

Sow performance is a key component of the productivity of commercial pig farms. Reproductive failure in the sow is common in pig production. For every 100 sows served, 89 should farrow. In absence of specific diseases such as porcine parvovirus, pseudo-rabies, swine fever, leptospirosis and brucellosis, management failures are the most important causes of loss. A syndrome associated with reproductive inefficiency, and post-service vaginal discharge and high sow mortality in a commercial pig farm is described. Pregnancy failures exceeded 20% and sow mortality exceeded 12% for two consecutive years. The abnormal post-service vaginal discharge rate was 1.7% during the period of investigation.An investigation involving an analysis of farm records, a review of breeding management practices, clinical examinations, laboratory analysis and examination of urogenital organs was conducted.The main contributing factors found were a sub-optimal gilt breeding management, an inadequate culling policy in combination with a sub-optimal culling rate and the presence of cystitis in more than 1% of the urogenital organs examined. The high sow mortality rate was related to an aged breeding herd.A control programme was recommended based on management changes involving oestrus detection, movement of gilts post-service, hygiene in the service area, boar exposure post-service and urinary acidification. This programme failed to increase the farrowing rate due to incomplete implementation of the recommendations made. The farrowing rate increased to 86.5% subsequent to a farm manager change in January 2005, which resulted in complete implementation of the control programme.     

Uterine Insemination with a Standard AI Dose in a Sow Pool System

The effect of uterine AI with a standard dose of spermatozoa on fertility of the sow was studied in a field trial. The trial involved a sow pool system with 440 sows using AI as the primary method of breeding. Sows were twice a day checked for oestrus symptoms by back pressure test in front of a boar on days 3–6 after weaning. When in standing heat, sows were randomly allocated into either a uterine insemination group (UTER, n = 157) or standard AI group (CONT, n = 169) and bred accordingly using 3 billion spermatozoa in 80 ml of extender. In both treatment groups, insemination was repeated once if the sow was still receptive 24 h later. Using pregnancy (farrowed or not) and live‐born litter size as the outcome variables, a logistic and linear regression approach, respectively, was taken to study the effect of the following factors: treatment (UTER vs CONT), AI operator, breed, satellite herd preceding weaning, parity, weaning‐to‐oestrus interval and length of lactation. Overall, live‐born litter size was 11.3 ± 2.9, repeat breeding rate 4.2% and farrowing rate 91.2%. In the UTER group, 93.6% of inseminated sows farrowed, whereas farrowing rate for the CONT group was 88.8% (p = 0.13). Intrauterine insemination with a standard AI dose did not result in a significant improvement in the live‐born litter size (11.5 ± 2.8 for the UTER and 11.1 ± 3.0 for the CONT sows, respectively, p = 0.13). However, the preceding satellite herd had a highly significant effect on the live‐born litter size (12.4 ± 2.6; 11.1 ± 2.9; 10.8 ± 2.9 and 10.9 ± 2.9 for the four satellite herds, p < 0.01). We conclude that uterine insemination did not have a significant effect on live‐born litter size and farrowing rate and we also conclude that satellite herd appears to have a major effect on fertility in a sow pool system.     

Effect of dietary fibre on reproductive performance of sows during the first two parities

The aim of this study was to investigate the effect of dietary fibre on reproductive performance during the first two parities. Gilts were randomly allocated to receive three fibrous diets from days 1-90 of gestation, including low fibre [low fiber (LF), 10.8% neutral detergent fiber (NDF), n=132], middle fibre [middle fiber (MF), 15.8% NDF, n=132] and high fibre diet (HF, 20.8% NDF, n=135), until completion of the second parity. Response criteria included backfat measurements, litter size and pig weight at parturition and day 22 of lactation, weaning-oestrus-interval, oestrus rate, sow farrowing and culling rate, uniformity of newborns and relative organ weights. The results showed sows fed LF diet in parity 1 gained more backfat (p<0.05) during gestation but lost more (p<0.05) during lactation than sows fed HF diet. Furthermore, sows fed LF diet farrowed more pigs (+0.7-1.1 pigs, p<0.05) and pigs born alive (+1.0 pigs, p<0.05) relative to sows fed HF diet. Likewise, sows fed LF and MF diets had greater litter weights at parturition (both p=0.06) and day 22 after lactation (both p<0.05). In parity 2, yet, it was MF diet to increase both total pigs born and pigs born alive (+0.9-1.1 pigs, p<0.05) and litter weight (p=0.05) relative to other diets. After 22 d of lactation, intriguingly, sows fed HF diet had most pigs alive (p<0.01-0.07) and heavier litter weight (p=0.07 or 0.2). Feeding HF diet also increased internal organs weight of newborns (p<0.05). Collectively, feeding LF and MF diets had beneficial effects on litter weight at parturition and day 22 of lactation in parity 1, and feeding MF diet until parity 2 was able to improve litter size and weight at parturition, but this positive effect disappeared after 22 days of lactation, instead feeding HF diet showed the optimal litter performance.     

Reproductive performance and estimates of labor requirements associated with combinations of artificial insemination and natural service in swine.

A study was conducted to examine effects of mating systems composed of natural service (NS) and AI in swine on farrowing rate, litter size, and labor requirements. Sows and gilts were bred once per day via one of the following treatments (d 1/d 2): NS/NS, NS/AI, AI/AI, and NS/none. Gilts bred with NS/AI, AI/AI, and NS/NS had higher (P less than .05) farrowing rates than gilts bred with NS/none matings. Similarly, farrowing rates were higher (P less than .05) in NS/AI than in NS/NS gilts. Numbers of pigs born alive were greater (P less than .05) in NS/NS, NS/AI, and AI/AI than in NS/none gilts. In sows, a treatment x time interaction (P less than .01) was present for farrowing rate. In the AI/AI treatment, farrowing rate increased (P less than .01) from 70.0% (wk 1 through 3) to 88.5% (wk 4 through 10). Farrowing rates were 87.3, 93.2, and 76.0% in the NS/NS, NS/AI, and NS/none groups, respectively, and did not change (P = .72) over time. Sows bred via NS/NS and NS/AI had larger litters (P less than .05) than NS/none sows. In the present study, if four or more sows and gilts were bred, then AI required less (P less than .05) time per animal than NS. Furthermore, gilts required more (P less than .05) time for breeding than sows. Results from this study demonstrate that gilts and sows responded differently to combinations of NS and AI in terms of reproductive performance. In addition, differences in labor requirements per sow or gilt between NS and AI matings were dependent on parity and daily breeding demands.     

A seroepidemiological survey of Leptospira bratislava infections in Danish sow herds

A total of 796 sows and gilts from 30 Danish sow herds were examined three times at intervals of 6 weeks for serum antibodies to Leptospira bratislava by the microscopic agglutination technique (MAT) test. The prevalence of seroreactors with positive titer values, 1:100, at the three successive tests were 2.7%, 2.5% and 2.9%; 4.5% of the animals were positive in at least one of the three tests, and 2.2% showed a greater than two-fold rise in titer between two consecutive samplings. Of the 30 herds, 21 (70%) had ever-positive within-herd prevalences in sows and gilts of 4–13%. The risk of a herd having one or more positive sow was positively associated with a herd size of > 141 sows, and distinct regional differences in the prevalence of positive herds were observed. The reproductive performance of the 21 herds with seroreactions was poorer than the performance of the nine herds without positive reactions concerning the variables: ‘days from weaning to last service’ (2.7 days more, P = 0.07), ‘percentage of sows returning to heat’ (4.0 percentage units more, P = 0.03), ‘services per farrowing’ (0.04 more, P = 0.04), ‘farrowing percentage’ (4.3 percentage units lower, P = 0.06), and ‘stillborn pigs per farrowing’ (0.16 more, P = 0.02). No association between the MAT serological status of the herd and the incidence of medical treatments of sows and gilts could be found. A high prevalence and low cumulative incidence of seroreactors was demonstrated in first-parity gilts, followed by a low prevalence and cumulative incidence from parity 2 to 3, and a high prevalence and cumulative incidence at the fifth parity.     

Management and environmental factors associated with annual sow culling rate: A path analysis

The relationships between management and environmental factors and annual sow culling rate were investigated in 152 Minnesota swine breeding herds. Data were obtained through a postal survey. A general path model was hypothesized to describe relationships among variables. Multiple least-squares and logistic regressions were used to test the statistical significance of pathways. The associations between the indepen variables and the annual culling rate (ACR) were decomposed into direct, indirect, and common cause associations.

The mean ACR of the 152 farms was 39% ± 2% rm(SE). Using path-analysis techniques, only the type of flooring during gestation, the size of the herd and the lactation length had a direct relationship with ACR. The type of housing during gestation and farrowing were related indirectly to the ACR. Their association was mediated by the type of flooring during gestation and the weaning age. Herds housing their sows in total confinement during gestation were most likely to keep them on partially or totally slatted floors which were associated with a higher ACR. Sows kept in crates during the farrowing period were more likely to have a short lactation length which was associated with a higher ACR.

Most associations between the use of preventive veterinary services and the ACR were due to association with other variables. Herds using veterinary preventive medicine were most likely to have a short lactation length, a large number of females, and sows housed in total confinement during gestation and in crates during the farrowing period. All of the aforementioned variables were associated with a high ACR.

The relationships of other management and environmental factors with the ACR were due to common cause associations. These factors included having the sows individually identified, using a more comprehensive recording system, mainly a hand-mating system, testing regularly for pregnancy and housing sows in total confinement during the breeding period. The strongest associations with the ACR were the type of flooring during gestation and the size of the herd.     

Seroprevalence and risk factors associated with seropositivity in sows from 67 herds in north-west Germany infected with Mycoplasma hyopneumoniae

Risk factors for the spread of Mycoplasma hyopneumoniae in sows have not been studied although vertical transmission from sows to their offspring is considered a significant risk factor in the development of enzootic pneumonia in growers and finishers. Seropositivity for M. hyopneumoniae in sows, as assessed by commercial ELISA, is a possible indicator of infection pressure among sows. The objective of this study was to estimate seroprevalence and associated risk factors of a sow being seropositive for M. hyopneumoniae. A cross-sectional study was carried out in 2578 sows from 67 herds in north-west Germany. Data concerning general herd characteristics, acclimatisation practices, indoor and outside contacts, as well as data describing the immediate local environment were collected during a herd visit via questionnaire. Blood samples were seropositive in 65% of the 2578 sows, and all herds had ≥14% seropositive sows. Data analysis was performed in two steps. First, univariate analysis of predictor variables for the risk of a sow being seropositive for M. hyopneumoniae was performed using chi-square test. Secondly, all variables associated with the risk of a sow being seropositive (P ≤ 0.25) were included in a multivariate model using a generalised linear model. The risk of a sow being seropositive for M. hyopneumoniae was increased in herds with two- or three-site production (OR 1.50), when piglets were not vaccinated against M. hyopneumoniae (OR 1.81), in herds with a 2-week farrowing intervals (OR 1.84) and in herds without all-in/all-out management of the farrowing units (OR 1.37). The lack of an acclimatisation period for replacement boars was also associated with the risk of a sow being seropositive (OR 2.10). The results indicate that M. hyopneumoniae seropositivity is common in sows in north-west Germany and is influenced by various management factors. It is recommended that evaluation of sow herd management should be included in any strategic health plan to control M. hyopneumoniae infection.     

REVIEWS: Compilation of the Scientific Literature Comparing Housing Systems for Gestating Sows and Gilts Using Measures of Physiology,Behavior, Performance,and Health

The objective of this review was two-fold. First, a series of meta-analyses (analyses of treatment effects across studies) were performed on available data from scientific literature to determine whether sow behavior, performance, or physiology differed for sows in group pens or individual stalls. Second, research publications in areas of performance and health, physiology, and behavior of pregnant gilts and sows in studies that directly compared gestation sow housing systems were summarized. Common systems were stalls, tethers, and various types of group housing systems. Results of meta-analyses showed that the average levels of productivity, oral-nasal-facial behaviors (ONF), and blood cortisol were statistically similar for sows in group pens and stalls. For the review, in some studies, circulating cortisol concentrations were greater among gestating females kept in tethers compared with other systems; however, overall cortisol was not altered by housing system. Immune parameters were largely not influenced by housing system. Housing system did not alter heart rate. Gestation housing system may influence sow behavior including stereotypic ONF, postural locomotory, feeding behaviors, or social behaviors. Overall, total ONF behaviors were comparable between gestation sow housing systems. However, tethered and stalled sows exhibited more stereotypic ONF compared with sows in group or outdoor systems. Compared with group housing, individually confining sows during gestation resulted in postural and movement restrictions. Stall size and design can impact postural adjustments and inter-stall aggression of individually housed sows. Inconsistent performance and health results were found among sow housing studies. Sows in stalls consistently had equal or greater reproductive performance compared with sows in other systems. Farrowing rate for sows in individual stalls was equal to or superior to sows in other systems. Farrowing rate was clearly superior among sows in stalls compared with group systems, where dynamic social groups were employed. However, tethered sows may have reduced litter size and increased piglet birth weight. Sows in group housing systems, particularly electronic sow feeder (ESF) systems, had injury scores greater than sows in either stalls or tethers. Gestation housing system (individual vs group) may impact sow welfare in the farrowing area (using stalls or pens). In conclusion, although individual studies found significant housing system effects, subjected to the overall evidence from adequately designed studies meta-analyses revealed that gestation stalls (non-tethered) or well-managed pens generally (but not in all cases) produced similar states of welfare for pregnant gilts or sows in terms of physiology, behavior, performance, and health.     

Salmonella seroprevalence at the population and herd level in pigs in The Netherlands

The aim of this study was to provide baseline data on the population and herd Salmonella seroprevalence in sows and finishers. For the population estimates in 1996 and 1999 and the herd prevalences for sows and gilts, blood samples from swine vesicular disease (SVD) and pseudorabies monitoring programmes were used and tested in an indirect Salmonella enzyme-linked immunosorbent assay (ELISA). The herd prevalence for finishers was determined using blood samples collected at two slaughterhouses.The population prevalence for finishers in 1996 and 1999 was 23.7 and 24.5%, respectively, and for sows 40.5 and 60.4%, respectively. The prevalence in free range (FR) finishers was significantly higher (44.6%) than in intensively housed finishers in 1999, identifying a hazard group for possible extra pork and pork product contamination. Of 406 finishing herds, 9% were completely seronegative for Salmonella (cut-off OD%>10). Of these 406 finishing herds, 69.7% had Salmonella-status I (low prevalence), 21.7% status II (moderate prevalence) and 8.6% status III (high prevalence) (cut-off OD%>40). In 46 multiplying sow herds, 20 breeding sow herds and 20 matching replacement gilt herds, the average herd prevalences were 54, 44.4 and 19.3%, respectively. Two gilt herds were completely seronegative. The prevalence in the gilt herds was never higher than in the matching breeding sow herds. Agreement on methodology and calibration of ELISA tests would make these results comparable between countries and is a prerequisite for a co-ordinated and integrated program to reduce Salmonella in pork in the European Union.     

Clinical signs and their association with herd demographics and porcine reproductive and respiratory syndrome (PRRS) control strategies in PRRS PCR-positive swine herds in Ontario

The purposes of this study were to describe the clinical signs observed in PRRS positive herds during a porcine reproductive and respiratory syndrome (PRRS) outbreak in Ontario and to determine associations between these clinical signs and herd demographics and PRRS control strategies. All PRRS polymerase chain reaction-(PCR)-positive submissions to a diagnostic laboratory between September 1, 2004 and August 31, 2007 were identified (n = 1864). After meeting eligibility requirements and agreeing to voluntary study participation, producers from 455 of these submissions were surveyed for information on clinical signs observed in their herds, herd demographics, and PRRS control strategies used in their herds at the time that the PCR-positive samples were taken. Larger herd size was associated with an increased risk of reporting abortion, weakborn piglets, off-feed sows, and sow mortality in sow herds, and with an increased risk of reporting mortality in finishing herds. When disease control strategies were examined, use of a commercial PRRS vaccine in sows and gilts was associated with a decreased risk of reporting weakborn pigs and high pre-weaning mortality, while the use of serum inoculation in breeding animals was associated with an increased risk of reporting off-feed sows and sow mortality. Providing biofeedback of stillborn/mummified piglets, placenta or feces to gilts was associated with an increased risk of reporting respiratory disease and mortality in finishing pigs while all-in/all-out flow in farrowing rooms was associated with an increased risk of reporting sow mortality and weakborn piglets.     

A field evaluation of Nobi-Vac atrophic rhinitis vaccine

A field trial was carried out with Nobi-Vac AR vaccine in 11 swine breeding herds. One herd suffered from severe B. bronchiseptica (BB+) rhinitis in piglets, while no clinical Atrophic Rhinitis (AR) was observed. Ten herds were described as AR problem herds, because clinical AR was observed for at least 1 year in spite of the fact that medication of sows and piglets was carried out and adequate housing and management systems were available in most herds. BB+ was isolated in 9 of these 10 farms and the AR pathogenic P. multocida (PM+) in all these farms. The trial started when piglets were born of sows which had been vaccinated 3 times. All piglets between 7 and 10 weeks old were examined clinically for AR. Nasal swabs from 20 pigs on each farm were screened bacteriologically for BB+ and PM+ every other month. A severe reoccurrence of AR was found in 2 of the 10 AR problem farms. In these 2 herds the 'all in-all out' system was not applied in farrowing and weaning houses. In the 8 other AR problem herds the percentage of pigs with AR decreased significantly below the average level of 1% per year. The percentage of pigs infected with BB+ and PM+ also decreased significantly. PM+ was significantly related to the percentage of clinical AR piglets. Seasonal effects contributed to a minor extent to the percentage of AR piglets. After 2.5 years of this trial PM+ could not be isolated during the last 12 months in six of the remaining AR problems herds. The conclusion is that Nobi-Vac AR vaccination of the sow gave protection against clinical AR in piglets on those farms (80%) which provided adequate housing and management systems.