Osteochondrosis / Osteoarthrosis and Claw Disorders in Sows,Associated with Leg Weakness

The objective of this study was to investigate the associations between different leg weakness symptoms and osteochondrosis/osteoarthrosis and claw disorders in sows together with the influence of age on these findings. One hundred and seventeen sows in one herd were followed from 6 months of age until culling and judged for leg weakness once in every gestation using a scale from 1 (normal) to 4 (severe changes). At slaughter changes in joints, growth plates and claws were scored on a scale from 1 (normal) to 5 (very severe changes). Osteoarthrotic changes were strongly associated with osteochondral changes in humeral and femoral condyles. The clinical signs of osteochondrosis and osteoarthrosis were found to be: buck-kneed forelegs, turn out of fore and hind legs, upright pasterns on hind legs, stiff locomotion, lameness and tendency to slip. The clinical signs of claw lesions were found to be: buck-kneed forelegs, upright pasterns, steep hock joints, turn out of hind legs, standing under position on hind legs, stiff movements, swaying hindquarters, goose-stepping hind legs, tendency to slip and lameness. Overgrown claws were strongly associated with leg weakness indicating the need for claw trimming in sow populations.     

Genetic trends of conformation traits and genetic correlations to osteochondrosis in boars

The objective of our study was to investigate the heritabilities and genetic correlations between traits from a linear exterior assessment system and osteochondrosis (OC) measured by computed tomography (CT), and in addition, to study the genetic trend in a population where the conformation traits have been included in the breeding goal. The data material consisted of phenotypes from a total of 4571 Norsvin Landrace test boars. At the end of the test period, all boars were subjected to a detailed exterior assessment system. Within 10 days of the assessment, the boars were CT scanned for measuring OC. The total score of osteochondrosis (OCT), used in this study, is the sum of phenotypes from the assessment on the medial and lateral condyles at the distal end of both the humerus and the femur of the right and the left leg of the boar based on images from CT. The exterior assessment traits included in the study were; ‘front leg knee’ (FKNE), ‘front leg pasterns’ (FPAS), ‘front leg stance’ (FSTA), ‘front leg twisted pasterns’ (FFLK), ‘hind leg stance’, ‘hind leg pasterns’ (HPAS), ‘hind leg standing under’ (HSTU), ‘hind leg small inner toe’, ‘dipped back’, ‘arched back’ (ARCH) and ‘waddling hindquarters’ (WADL). The estimation of (co)variance components and breeding values were performed using bivariate animal genetic models. Breeding values for HSTU, HPAS, FPAS, WADL and OCT traits were additional outputs from the same bivariate analyses. The lowest heritability was found for FFLK (h²_FFLK=0.05), whereas FPAS was estimated to have the highest heritability (h²_FPAS=0.36), and OCT demonstrating a heritability of 0.29. Significant genetic correlations were found between several traits; the strongest correlation was between FSTA and FFLK (0.94), which was followed by the correlation between FPAS and FKNE (0.69). The traits ARCH and FSTA had significant genetic correlations to OCT, whereas all other genetic correlations between OCT and the conformation traits were low and not significantly different from 0. Our study shows positive genetic trends for the conformation traits included in the breeding goal. In general, low genetic correlations between conformation traits and OC were observed in our study.     

Culling intervals and culling risks in four stages of the reproductive life of first service and reserviced female pigs in commercial herds

The objectives of this study were to measure culling intervals and culling risks in the four stages of the reproductive life of female pigs and to compare culling intervals between the number of services and between herd groups, based on herd productivity. We also compared survival patterns of females pigs between these herd groups. Our data set included lifetime records of 52,792 females born between 2001 and 2004 in 101 commercial herds. Two herd groups were selected on the basis of the upper 25th percentile of pigs weaned per mated female per 5 yr between 2002 and 2006, namely the high-performing herds, and ordinary herds. Culled females were also allocated into four groups based on the stages of their reproductive life when culled: unmated gilts, mated gilts, unmated sows, and mated sows. Culling intervals in unmated gilts and mated gilts were defined as the number of days from birth to culling and from first mating to culling, respectively. Culling intervals in unmated sows and mated sows were the number of days from weaning to culling. The number of services was categorized into two groups: first service and reservice groups. Multilevel linear mixed-effects models and survival analysis were performed. Culling intervals (±SEM) in unmated gilts, mated gilts, unmated sows, and mated sows were 302.9 ± 1.16, 98.4 ± 0.92, 14.3 ± 0.12, and 89.6 ± 0.42 d, respectively. Culling risks in the four groups were 5.6%, 7.1%, 58.0%, and 29.3%, respectively. In unmated gilts, mated gilts, and mated sows, the culling intervals in the high-performing herds were 43.0, 18.9, and 16.0 d shorter than those in ordinary herds, respectively (P < 0.05), but no difference was found between the herd groups for the culling interval of unmated sows. For mated sows in the reservice group, culling intervals of high-performing herds were ≥13.7 d shorter than those of the ordinary herds (P < 0.05), but for mated sows in the first service group, there was no difference in the culling interval between the herd groups. The culling hazard from 8 wk postweaning for mated sows in high-performing herds increased more rapidly than that in ordinary herds. In conclusion, to reduce culling intervals and improve herd productivity, we recommend implementing a strict culling policy for mated gilts and mated sows, especially reserviced females.     

Competing risk analyses of longevity in Duroc sows with a special emphasis on leg conformation

A competing risk approach was used to evaluate the influence of several factors on culling risk for 587 Duroc sows. Three different analyses were performed according to whether sow failure was due to death during productive life (DE) or to one of two causes for voluntary culling: low productivity (LP) and low fertility (LF). Sow survival was analyzed by the Cox model. Year at first farrowing (batch effect) significantly affected sow survival in all three analyses (P < 0.05 for DE and P < 0.001 for LP and LF) whereas farm of origin accounted for relevant variation in the LP and LF analyses. LP culling increased with backfat thickness of more than 19 mm at the end of the growth period (P < 0.05), bad teat condition (P < 0.05) and reduced piglets born alive (P < 0.001). For the LF competing risk analysis, culling increased with age at first farrowing (P < 0.1). Special emphasis was placed on the influence of leg and teat conformation on sow survivability, although they did not affect sow failure due to DE (P > 0.1). The overall leg-conformation score significantly influenced sow longevity in LP (P < 0.001) and LF competing risk analyses (P < 0.001), showing a higher hazard ratio (HR) for poorly conformed sows (1.013 and 4.366, respectively) than for well-conformed sows (0.342 and 0.246, respectively). Survival decreased with the presence of abnormal hoof growth in LP and LF analyses (HR = 3.372 and 6.002, respectively; P < 0.001) and bumps or injuries to legs (HR = 4.172 and 5.839, respectively; P < 0.01). Plantigradism reduced sow survival in the LP analysis (P < 0.05), while sickle-hooked leg (P < 0.05) impaired sow survival in the fertility-specific analysis. Estimates of heritability for longevity related to LP culling ranged from 0.008 to 0.024 depending on the estimation procedure, whereas heritability values increased to between 0.017 and 0.083 in LF analysis. These analyses highlighted substantial discrepancies in the sources of variation and genetic background of sow longevity depending on the cause of failure. The estimated heritabilities suggested that direct genetic improvement for sow longevity seemed feasible, although only a small genetic progress was expected.     

Position-dependent sensitivity and density of taste receptors on the locust leg underlies behavioural effectiveness of chemosensory stimulation

Chemical stimulation of contact chemoreceptors located on the legs of locusts evokes withdrawal movements of the leg. The likelihood of withdrawal depends on the site of stimulation, in addition to the identity and concentration of the chemical stimulus. A significantly higher percentage of locusts exhibit leg avoidance movements in response to stimulation of distal parts of the leg with any given chemical stimulus compared to proximal sites. Moreover, the percentage of locusts exhibiting avoidance movements is correlated with the density and sensitivity of chemoreceptors on different sites of an individual leg. The effectiveness of chemical stimulation also differs between the fore and hind legs, with NaCl evoking a higher probability of leg withdrawal movements on the foreleg. Moreover, sucrose was less effective than NaCl at evoking withdrawal movements of the foreleg, particularly at low concentrations. The gradients in behavioural responses can be partially attributed to differences in the responsiveness and density of the contact chemoreceptors. These results may reflect the different specialization of individual legs, with the forelegs particularly involved in food selection.     

Compliant leg behaviour explains basic dynamics of walking and running

The basic mechanics of human locomotion are associated with vaulting over stiff legs in walking and rebounding on compliant legs in running. However, while rebounding legs well explain the stance dynamics of running, stiff legs cannot reproduce that of walking. With a simple bipedal spring-mass model, we show that not stiff but compliant legs are essential to obtain the basic walking mechanics; incorporating the double support as an essential part of the walking motion, the model reproduces the characteristic stance dynamics that result in the observed small vertical oscillation of the body and the observed out-of-phase changes in forward kinetic and gravitational potential energies. Exploring the parameter space of this model, we further show that it not only combines the basic dynamics of walking and running in one mechanical system, but also reveals these gaits to be just two out of the many solutions to legged locomotion offered by compliant leg behaviour and accessed by energy or speed.     

Impact of Mated Female Nonproductive Days in Breeding Herd after Porcine Epidemic Diarrhea Virus Outbreak

Porcine epidemic diarrhea virus (PEDV) is an important pathogen that has a significant economic impact on the swine industry by imposing a high rate of mortality in suckling piglets. However, limited information on the productivity values of gilts and sows infected with PEDV is available. Here, we evaluate the productivity index in gilts and sows during the 1-year period before (19 January 2013 to 18 January 2014) and after (19 January 2014 to 18 January 2015) a PEDV outbreak from a 2000-sow breeding herd in Taiwan. The farrowing rate (FR), return rate (RR), total pigs born per litter (TB), pigs born alive per litter (BA), weaning pigs per litter (WPL), pre-weaning mortality, percentage of sows mated by 7 days after weaning, weaning to first service interval (WFSI), mated female nonproductive days (NPDs), replacement rate of sows and sow culling rate were compared using productive records. The FR (-9.6%), RR (+9.8%), TB (-1.6), BA (-1.1), WPL (-1.1), sows mated by 7 days after weaning (-6.9%), WFSI (+0.8 days), NPDs (+6.9 days) and sow culling rate (+7.2%) were significantly different between the 1-year pre-PEDV outbreak period and the post-PEDV outbreak period. Impacts of the PEDV infection on the reproductive performance were more severe in pregnant gilts than in sows. In conclusion, these findings indicate that the outbreak of PEDV caused an increase in the rate of NPDs in breeding herds.     

Semiaquatic Heteroptera locomotion: coral treaders (Hermatobates weddi, Hermatobatidae), sea skaters (Halovelia septentrionalis, Veliidae), and water striders (Metrocoris histrio, Gerridae). Usual and unusual gaits

Using high-speed video recordings, we carried out an analysis of the locomotion gaits of the following aquatic Heteroptera: coral treaders Hermatobates weddi (Hermatobatidae), sea striders Halovelia septentrionalis (Veliidae), and water striders Metrocoris histrio (Gerridae), in the Island of Amami Oshima, Kagoshima Prefecture, Japan. Most insects use an alternating double tripod gait for walking, whereas species of Gerridae and some Veliidae use a synchronous rowing gait. We found that H. weddi used a peculiar locomotion gait, a modification of the double tripod gait. In this special gait, two alternating dipods (mid and hind legs) are used, while the forelegs remained inactive. Contralateral mid and hind stroked simultaneously. The mid leg recovered immediately after the stroke; however, the hind leg was delayed and remained extended after the stroke. Next, the following bipod stroked, and when that mid leg finished the stroke, both ipsilateral mid and hind (the one which did not recover after the stroke) legs recovered together. Turning is also unique in H. weddi because the body axis rotation and the course turning (deflection) were clearly separated in two phases. We compared the kinematics of H. weddi pattern with the synchronous rowing pattern found in H. septentrionalis and M. histrio and discussed some biomechanical consequences. We also analyzed phylogenetic implications of this gait, and we posit that the modified double dipod gait is a uniquely derived character of the family Hermatobatidae. The synchronous rowing gait would be an autapomorphy for the clade Gerridae + Veliidae. The modified thorax, with the meso and metacoxae horizontally directed, would be a synapomorphy for the superfamily Gerroidea (Hermatobatidae, Gerridae, and Veliidae). Handling editor: Koen Martens     

An Observational Study of the Effects of Therapeutic Hoof Blocks on the Locomotion,Behavior, and Production of Healthy Dairy Cattle

Therapeutic hoof blocks have been recommended for treatment of sole ulcers in dairy cattle; however, they are underutilized in the industry. Twenty Holstein cows were randomly assigned to receive a wooden hoof block applied to the left hind leg (n = 5), to the right hind leg (n = 5), or no hoof blocks (n = 10). Accelerometers were affixed to both hind legs of 10 blocked cows and 5 control cows. Cows were observed for locomotion scores, and milk production was recorded. Mixed models were constructed to determine effects of block application on behavior, milk production, and locomotion. Activity was altered by day, with cows being most active on Day ? 1. The mean number of daily lying bouts and lying bout duration did not differ by treatment. Locomotion scores were higher for blocked cows on Days 1, 2, and 3 compared with baseline; however, milk production did not differ between treatments. In conclusion, although block application affected the appearance of locomotion, it did not appear to adversely affect the behavior or milk production of sound dairy cows.     

Does homozygosity contribute to the asymmetry of common white leg markings in the Arabian horse?

Common white and facial markings have a multifactorial mode of inheritance inEquus caballus and result from the absence of melanocytes in the unpigmented areas. Directional asymmetry and fluctuating asymmetry apparently account for the total asymmetry of common white leg markings. Using computerized records obtained from the Arabian Horse Registry of America, Inc., and the International Arabian Horse Association, studies were carried out to determine if homozygosity increases the total asymmetry in common white leg markings by presumably promoting fluctuating asymmetry. The results were as follows: (1) Arabian horses that are symmetrical and asymmetrical for common white leg markings have similar distributions of inbreeding coefficients; (2) Arabian and half-Arabian horses have similar concordance values, in general, for specific white markings in both their forelegs and hind legs. It is concluded that homozygosity does not contribute to the total asymmetry of common white leg markings in the Arabian horse.     

The effects of zearalenone on reproduction in swine. II. The effect on puberty attainment and postweaning rebreeding performance

Eighty-five prepuberal, crossbred gilts received, ad libitum, a diet containing 0 or 10 ppm purified zearalenone for 30 d beginning at 145 to 193 d of age. At the end of this period all gilts were placed on the control diet and exposed daily to a mature boar for 60 d. Within 3 to 5 d of zearalenone ingestion, gilts showed marked vulval swelling and reddening, which continued for the 30-d feeding period. Thereafter symptoms slowly subsided. Zearalenone treated gilts showed first estrus significantly later than controls (P < 0.05), but the proportion of gilts showing estrus within 60 d of boar exposure was similar (P > 0.05). The length of the first estrous cycle was not affected by the ingestion of zearalenone before puberty (P > 0.05). In a second study, 65 multiparous, crossbred sows were full-fed twice daily a ration containing 0 or 10 ppm of purified zearalenone beginning 14 d before weaning. Postweaning, all sows were fed the control diet, were checked for estrus daily, and inseminated at the first postweaning estrus. Neither sows nor gilts from their litters exhibited signs of hyperestrogenism during treatment. Weaning to estrus interval was significantly extended in zearalenone treated sows (P < 0.05), but all other variables of fertility assessed were similar. These data suggest that zearalenone ingestion before puberty delays the stimulation of puberty associated with boar exposure, but does not affect subsequent cyclicity if zearalenone is removed from the ration. Similarly, zearalenone ingestion during lactation delays the return to estrus after weaning, but does not affect subsequent fertility when removed from the ration at weaning.     

Ovarian activity and uterus organometry in delayed puberty gilts

About 30% of the total number of gilts selected for reproduction at the large breeding farm units in Vojvodina (Republic of Serbia) are culled due to prolonged pre-insemination anoestrus (estrus not detected until 8 mo of age). The aim of this study was to provide the answer to the following question: do the culling gilts reach cyclic ovarian activity at all? One hundred seventy five culled gilts in which external estrus manifestations were not detected by 8 mo of age were sacrificed and their reproductive organs were examined for determination of sexual maturity (ovaries exhibiting pre-ovulatory follicles 8 to 11 mm in diameter, corpora hemorrhagica, corpora lutea and corpora albicantia). Uterine weights and horn length were also determined. Functional ovaries were observed in 107 (61.1%) examined gilts, with 62 animals having one and 45 having two puberty ovarian cycles (57.9% and 42.1%, respectively). Pathomorphological changes which could result in prolonged pre-insemination anoestrus were not observed on the reproductive organs of sexually mature gilts. Our results indicate that most of the culling gilts have reached cyclic ovarian activity. The main reason for culling due to the absence of external estrus manifestations in sexually mature gilts could be inadequate estrus detection technology.     

Pushing versus pulling: division of labour between tarsal attachment pads in cockroaches

Adhesive organs on the legs of arthropods and vertebrates are strongly direction dependent, making contact only when pulled towards the body but detaching when pushed away from it. Here we show that the two types of attachment pads found in cockroaches (Nauphoeta cinerea), tarsal euplantulae and pretarsal arolium, serve fundamentally different functions. Video recordings of vertical climbing revealed that euplantulae are almost exclusively engaged with the substrate when legs are pushing, whereas arolia make contact when pulling. Thus, upward-climbing cockroaches used front leg arolia and hind leg euplantulae, whereas hind leg arolia and front leg euplantulae were engaged during downward climbing. Single-leg friction force measurements showed that the arolium and euplantulae have an opposite direction dependence. Euplantulae achieved maximum friction when pushed distally, whereas arolium forces were maximal during proximal pulls. This direction dependence was not explained by the variation of shear stress but by different contact areas during pushing or pulling. The changes in contact area result from the arrangement of the flexible tarsal chain, tending to detach the arolium when pushing and to peel off euplantulae when in tension. Our results suggest that the euplantulae in cockroaches are not adhesive organs but 'friction pads', mainly providing the necessary traction during locomotion.     

A retrospective study on the preserving capacity of a commercial boar semen extender

The objective of this study was to evaluate the preserving capacity of a commercial, long-term boar semen extender beyond 4 days in terms of farrowing failure and total born per litter in sows and gilts. Data from 21 farms were subjected to logistic and linear regression analyses to assess the effect of parity (2-5, > 5 and gilts), wean-to-service interval (/= 6 days) and number of AI (1, 2, or 3) on the association between semen age (/=10 days) and fertility. As the semen age increased, the likelihood of farrowing failure increased and total born per litter decreased in sows and gilts. The effect of semen ageing on farrowing failure was more pronounced in sows than in gilts as in the latter it became significant only after 8 days. The effect of semen ageing on total born per litter was similar in both sows and gilts. A lower parity and wean-to-service interval were associated with a reduction in farrowing failure and increase in total born per litter in sows. Increasing the number of inseminations up to two was beneficial in reducing farrowing failure in sows and gilts. A third insemination increased the likelihood of farrowing failure in sows. The number of total born per litter in sows increased with number of inseminations and the effect was not significant in gilts.     

Time of the preovulatory LH surge in the gilt and sow relative to the onset of behavioral estrus

Two experiments were conducted to study the time of occurrence of the preovulatory LH surge in pigs. Sampling every ten minutes in six cycling gilts before and after onset of standing estrus revealed the preovulatory surge began from 8 hr before to 12 hr after the lordosis reflex was elicited. Three of six gilts initiated the preovulatory LH release coincident with the onset of estrus. Data from 28 postpartum sows, with samples drawn every six hours commencing with the onset of estrus, indicated maximum LH levels were present at the first observance of estrus. Six of the 28 sows had an LH peak 18-24 hr after the onset of estrus.     

Processing of tactile information in neuronal networks controlling leg movements of the Locust

The successful, coordinated, posture and locomotion of any animal requires a precise and continuous adjustment of limb movements by sensory feedback from extero- and proprioceptors associated with the legs. We here review the recent advances in our understanding of how specific local adjustments of the hind legs of the desert locust, Schistocerca gregaria, are made in response to tactile signals from two different classes of exteroceptor on a leg. The aim is to understand particular features of the organization of neuronal networks and how different types of constituent interneurones contribute to the processing of sensory signals. This information can then be used to define the design principles that govern the organization of sensory-motor networks.     

Intersegmental transfer of sensory signals in the stick insect leg muscle control system

Intersegmental coordination during locomotion in legged animals arises from mechanical couplings and the exchange of neuronal information between legs. Here, the information flow from a single leg sense organ of the stick insect Cuniculina impigra onto motoneurons and interneurons of other legs was investigated. The femoral chordotonal organ (fCO) of the right middle leg, which measures posture and movement of the femur-tibia joint, was stimulated, and the responses of the tibial motoneuron pools of the other legs were recorded. In resting animals, fCO signals did not affect motoneuronal activity in neighboring legs. When the locomotor system was activated and antagonistic motoneurons were bursting in alternation, fCO stimuli facilitated transitions from flexor to extensor activity and vice versa in the contralateral leg. Following pharmacological treatment with picrotoxin, a blocker of GABA-ergic inhibition, the tibial motoneurons of all legs showed specific responses to signals from the middle leg fCO. For the contralateral middle leg we show that fCO signals encoding velocity and position of the tibia were processed by those identified local premotor nonspiking interneurons known to contribute to posture and movement control during standing and voluntary leg movements. Interneurons received both excitatory and inhibitory inputs, so that the response of some interneurons supported the motoneuronal output, while others opposed it. Our results demonstrate that sensory information from the fCO specifically affects the motoneuronal activity of other legs and that the layer of premotor nonspiking interneurons is a site of interaction between local proprioceptive sensory signals and proprioceptive signals from other legs.     

Characteristics of the maintenance of the vertical posture during standing with an asymmetrical load on the legs

Movements of the common center of pressure (CP) and the CPs of the right and left legs separately were studied during the maintenance of the vertical posture by subjects standing with symmetrical load on their legs or with the shift of the load to the right or left leg. It was shown that standing with a symmetrical load on the legs was accompanied by the movement of the CP of an individual leg along the straight line with small deviations aside, whereas movement of the common CP represented the curve with frequent changes in direction and filling up some space. The shift of the load to one leg resulted in the movement of the CP of the loaded leg that was similar to that observed during a symmetrical load on the legs. The movement of the CP of the unloaded leg was chaotic. The shift of the load to one leg decreased the correlation between the movements of the CPs of the left and right legs compared to standing with a symmetrical load on the legs. The velocity of movement of the CP of the leg loaded increased in the sagittal direction but remained stable in the frontal direction. The velocity of movement of the CP of the unloaded leg remained stable in the sagittal direction but increased in the frontal direction. We suppose that during standing with an asymmetrical load on the legs the role of the single in the maintenance of the vertical posture depend on the load on the leg.     

Analysis of behavioral selection after sensory deprivation of legs in the cricket Gryllus bimaculatus

An air puff stimulus evoked the swimming of an intact cricket, Gryllus bimaculatus, placed on a water surface. When only the forelegs were intact, swimming was initiated frequently, but flying was never initiated. On the other hand, flying was initiated when only the middle legs or hindlegs were intact. Therefore, the sensory inputs from the forelegs are important in the initiation of swimming and for the inhibition of flying when on the water surface. After bilateral ablation of the middle legs and hindlegs, the bilateral segments of the remaining forelegs were sequentially ablated from the distal area to the proximal area of the legs. After bilateral ablation of all tarsomeres, the relative occurrence of swimming decreased and that of flying increased. After the following ablation of the bilateral tibiae, most insects responded to an air puff stimulus by flying. Experiments performed after coating the leg surface with enamel resulted in almost the same behavioral change as that observed in the ablation experiments. These results suggest that the sensory receptors responsible for the initiation of swimming and the inhibition of flying are mainly located on the surface of the tibia and the tarsus of the forelegs. The behavioral change between swimming and walking was also studied using methylcellulose solutions of various viscosities. On the methylcellulose solution, the relative occurrence of walking in the crickets increased with an increase in the viscosity of the solution.     

Experience of Vaccination against Porcine Parvovirus in Pig-Breeding Herds: Serological Status and Reproductive Performance

Blood samples from 77 gilts were examined for HI-antibody titers to PPV, all gilts belonged to the same herd and PPV-induced reproductive failure had previously occurred in the herd. Thirty-three gilts were vaccinated twice 5 and 2 weeks before mating while 44 gilts served as non-vaccinated controls. Only 3 % of the vaccinated gilts were seronegative at the time of mating compared to 14 % of the non-vaccinated gilts and 32 % of the non-vaccinated gilts had a serum titer lower than 1:64. The second part of the study comprised 4 herds with 50–70 sows in each herd. All of the herds had previously had reproductive problems caused by PPV infection. During the last 2 years, all gilts in these herds were vaccinated against PPV at 6.5 months of age with a revaccination 3–4 weeks later. There was a marked variation in serum titer levels among the 4 herds. In two herds the titers were overall rather low. In the third herd all had high PPV-titers at both sampling occasions and in the fourth herd the titers varied among animals but were rather consistent within animals at the two sampling occasions. In the herd with high titer, a PPV-outbreak was confirmed during January-March 1984. During that period all sows, vaccinated as gilts, farrowed normal litters. The results indicate that even in PPV-infected herds a large number of gilts are seronegative at the time of breeding and vaccination of gilts is therefore recommended. Furthermore it does not seem necessary to revaccinate sows, vaccinated as gilts, in herds where PPV is still present.