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The most universally accepted measure of reproductive performance is PSY. Excellence is achieved by reducing NPD, increasing liveborn litter size, and reducing preweaning mortality. To reduce NPD, farm management should be directed to improve farrowing rate. Matings that occur in late summer usually are less fertile as the result of the pig's normal seasonal variation. Confinement gestation stalls are the best prevention for the reduced farrowing rate caused by season. Liveborn litter size is the result of a mixture of genetic and management variables. F1 females have the highest heterosis. The management variables of age at first mating, wean-to-service interval, skip mating, lactation length, and parity all influence litter size.

Longevity of sows and boars affects the productivity and economics of the herd. Implement a culling program that is tailored to the specific needs of the producer and the characteristics of the farm. Evaluate the removal policies regularly, estimate the longevity of breeding animals, calculate the nonproductive sow days associated with culling, and determine the major causes of culling and death. Once a longevity problem and its extent have been identified, the underlying problems and predisposing factors can be more easily corrected.

This investigation was conducted to study boar culling patterns in swine breeding herds. Data were obtained from 84 swine breeding herds and included 440 boars that were culled. Each producer was involved for 12 consecutive months, and recorded every boar that was removed from the herd, the date, and the reason for culling. The annual culling rate for the 84 farms averaged 59.4% +/- 6.4 (SEM). The correlation coefficient between boar and sow culling was 0.52 (p <0.0001). Removal was the result of being overweight (47%), reproductive problems (18%), leg problems (12%), death (7%), and other diseases (4%). From the annual culling rate, the average breeding life of boars was estimated at 20 months. From this study, we concluded that the annual culling rate for boars in commercial herds was high and related to several different factors.

The transport of fresh and frozen semen to be used for artificial insemination creates a mode of disease transmission between farms. Normally, semen contains a number of nonpathogenic bacterial contaminants; however, excessive bacterial contamination can result in infertile matings. Contamination with a known pathogen, eg, Brucella suis, could initiate a serious outbreak of disease in a recipient herd. Methods to minimize bacterial contamination of semen include sanitary collecting and processing of semen, isolation of boards from certain pathogens, and the addition of appropriate broad spectrum or combination antibiotics to the semen. Mycoplasmas also have been isolated from semen, although transmission by this route is unlikely. The addition of an appropriate antimycoplasmal antibiotic to semen may be warranted in some situations. Numerous viruses have been detected in semen. Their exclusion from semen is especially critical because of their ability to survive in frozen semen. These viruses include pseudorabies virus, porcine parvovirus, enterovirus, adenovirus, vesicular disease virus, and African swine fever virus. The likelihood of disease transmission is greater with the introduction of a boar into a herd than through the use of fresh or frozen semen. We believe that artificial insemination allows for the introduction of new genetics into a breeding program, with minimal risk of disease transmission.

Antibody responses were compared in guinea-pigs, rabbits and pigs following vaccination with inactivated porcine parvovirus (PPV) vaccines. Mean PPV hemagglutination inhibition (HI) antibody titers of 52, 56 and 36 at 1 week after first vaccination and 896, 640 and 512 at 2 weeks after second vaccination were detected in guinea-pigs, rabbits and pigs, respectively. PPV vaccines prepared with greater concentrations of virus, as determined by hemagglutination (HA) units, and of aluminum hydroxide gel adjuvant, induced higher HI antibody titers in guinea-pigs. Optimal concentrations for inducing consistently high antibody titers consisted of vaccine virus with a HA titer of 256/0.1 ml and gel adjuvant at a final concentration of 50%. A second vaccination at 4 weeks compared to 2 or 3 weeks after first vaccination resulted in higher mean HI titers. These data provide preliminary information on the use of guinea-pigs or rabbits as laboratory animal models for testing the potency of PPV vaccines.

Four hundred and sixty-two pigs from 37 herds were examined at slaughter for the presence and extent of turbinate atrophy and pneumonia. Turbinate atrophy was scored by measuring the mm space between the turbinate bone and the floor of the nasal cavity on both sides of the nasal septum. The total percentage of pneumonic involvement for each lung was evaluated by scoring the percentage of each lobe that was consolidated.There was a low, positive correlation between individual scores of turbinate atrophy and the associated percentage of lung involved with pneumonia (r = + 0.177; p < 0.001). There was a postive correlation between the herd mean turbinate atrophy score and the herd mean percentage pneumonia score (r = + 0.515; p = 0.001).The age at slaughter was known for 95 pigs from four herds and was not significantly correlated with the mm of turbinate atrophy, or the percentage of pneumonia.

The influence of 7 factors on litter size for the combined parities 3 through 7 (age at conception of the first litter, parity-1 litter size, duration of lactation in the preceding parity, weaning-to-conception interval in the preceding parity, farrowing-to-conception interval in the preceding parity, number of matings per conception, and month of conception) was investigated in 11,929 litters from 5 commercial herds. Age at conception of the first litter did not influence litter size in these parities in any herd. In the 4 herds that kept such data, duration of lactation negatively influenced the weaning-to-conception interval, and duration of lactation and weaning-to-conception interval positively influenced the litter size in the next parity. Because the effects of duration of lactation and weaning-to-conception interval could not be investigated separately, their effects on litter size were simultaneously investigated, using the farrowing-to-conception interval for these combined parities. In all herds except one, the increase in live litter size was between 0.02 and 0.09 pig for each day increase in the preceding farrowing-to-conception interval less than 36 days (P less than 0.05). Duration of lactation within this farrowing-to-conception interval similarly influenced litter size. Litter size in litters of any herd was not affected by a preceding farrowing-to-conception interval greater than 35 days. In all herds except one, mean litter size of females with a farrowing-to-conception interval greater than 35 days was 0.26 to 0.96 pig greater (P less than 0.1) than for females with a farrowing-to-conception interval greater than 36 days. In 1 of 3 herds that kept such data, 2 matings per conception resulted in a larger mean live litter size than 1 or 3 matings (P less than 0.05). When these females were grouped on the basis of their conception during one of the 3-month seasonal periods, no influence of season on litter size was found. The effect of parity-1 litter size on litter size of subsequent parities 3 through 7 was significant. The regression coefficient ranged from 0.11 to 0.22 (P less than 0.01) in the farrowing-to-conception interval less than 36 days in all herds. In females with a farrowing-to-conception interval greater than 35 days, this association was significant only in one herd.(ABSTRACT TRUNCATED AT 400 WORDS)

Reproductive failure occurred in a swine herd in which the epizootiology of enteroviruses and the porcine parvovirus were being studied. Three virgin boars that were seropositive for the parvovirus were mated to seronegative, previously unmated gilts. The 11 gilts that farrowed had small litters, with high perinatal mortality. The remaining 12 gilts were marketed because of infertility, and the reproductive tracts were examined. Pathologic findings included early embryonal death attributed to viral infection. After the reproductive failure, all gifts and boars were seropositive for the parvovirus, suggesting that the reproductive failure was associated with a parvovirus infection.

Lungs from 113 pneumonic pigs were examined for Pasteurella multocida. The lungs were smeared directly onto blood agar and homogenized in brain-heart infusion broth and then inoculated intraperitoneally in mice. Pasteurella multocida isolates were typed for serotypes A (by hyaluronidase inhibition of capsule) and D (by acriflavine autoagglutination). Strains were tested for toxin production by intradermal injection of 0.2 ml of filtered 24-hour culture supernatants into guinea pigs. Most lungs (70.8%) yielded isolations. Most isolants (87.5%) were type A and 12.5% were type D. Of the type D strains, 80% were toxigenic. Of the type A isolants, 18.2% were toxigenic.

This investigation was conducted to study culling patterns in swine breeding herds. Data were obtained from 89 Minnesota swine breeding herds and included 5918 sows and 1324 gilts for a total of 7242 culled femaled. Each producer was involved for 12 consecutive months. They were asked to record every female that was removed from the herd, the reason for its culling and its parity. The annual culling rate for the sample averaged 50%, but varied considerably between herds ranging from 15% to 85%. Culled females had produced an average of 3.77 litters. Half of the females culled did not produce more than three litters. Reproductive failure accounted for 32% of all removals. The average parity of the females culled in that category was only 2.37: almost 33% were gilts. Failure to conceive represented 75% of all females culled for reproductive failure. Proportionally, culling as a result of anestrus was higher in gilts. It accounted for 33% of all gilts culled for reproductive failure which was twice as much as for sows. Inadequate performance accounted for 17% of all removals. These sows had produced an average of 5.11 litters. These results indicated that few animals were culled on the basis of first litter performance. Old age comprised 14% of all removals and the average parity at culling for this category was 7.11. Death accounted for 12% and the average parity for these females was 3.40. Locomotor problems and peripartum problems were the cause of 28% and 23% of all deaths, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive tracts were recovered from 209 sow and 32 gilt carcasses at slaughter; animals had been pregnant not less than 27 days. Of 241 litters examined, 28 (11.6%) contained one or more porcine parvovirus (PPV)-infected fetuses, as determined by immunofluorescent microscopy. The frequencies in sow and gilt litters were 12.0% and 9.4%, respectively. The PPV antigen was detected in 219 of 334 (65.6%) dead or mummified fetuses and in 12 of 2,172 (0.5%) live fetuses examined. The 18 litters which contained only dead or mummified fetuses were infected with PPV. As the percentage of litter mummification increased, the likelihood of finding PPV increased. The PPV antibody was detected in ovarian follicular fluids of 94.3% of the sows and 78.1% of the gilts. These findings indicate that PPV is highly associated with fetal mummification and that some pregnant gilts and sows are susceptible to infection.

Seasonal fluctuations in the estrous activity of sows after weaning and of sows and gilts after mating were determined by analysis of breeding records from eight swine herds covering a total of 19 herd-years of data. Of 11,461 sows, 78.4% were in estrus within 7 days after weaning. From July through September, 68.6% of sows returned to estrus within 7 days after weaning, compared with 82.0% during the remaining 9 months of the year. An increase in postweaning anestrus of more than 30 days' duration also occurred during summer months. Seasonal fluctuations in the frequency of postweaning estrus were similar for sows moved from farrowing facilities to environments with or without specialized temperature control features. For sows confined to crates after weaning, the rate of postweaning return to estrus was 10.4% greater than for sows in group-housing systems, but the seasonal pattern in postweaning return to estrus was not altered. Postweaning estrous failure was more obvious in primiparous sows than in multiparous sows, especially during summer and fall. The frequency of delayed return to estrus after infertile mating was 63.7% for matings during the period July through September and 29.7% for the period January through March. It was concluded that postweaning and postservice estrous activities in swine are influenced by season of the year and by parity. Group housing of sows or individual crating of sows, and water sprinkling or evaporative cooling systems in the postweaning breeding area, as used in the herds investigated, appear to be of questionable value in preventing estrous failure during summer and fall months.

Growth cartilages were obtained from humeri, femora, and ulnae of 31 pigs between 1 and 169 days old. On the basis of stain uptake and distribution, distinct layers were identified in articular-epiphyseal cartilage complexes and growth plates. The laminated appearance was dependent on stain uptake by territorial and interterritorial matrices and was more distinct in pigs greater than 15 days old. There was morphologic heterogeneity, which probably represented a functional heterogeneity, among chondrocytes in all layers and zones of both types of growth cartilage. The laminar appearance of growth cartilages and the distribution of different types of cells were similar for all pigs in each age category and for all sites.

Many boar problems result from an insufficient number of boars in relation to the number of sows in the herd, sexually immature boars, inadequately preconditioned or improperly managed boars. The following factors which determine optimum boar efficiency are discussed: (a) sexual development and mating behaviour, (b) selection, (c) preconditioning, (d) mating systems, (e) examination and culling.

To study the effect of 2 parasympathomimetic drugs in reduction of incidence of stillborn pigs, 84 sows and gilts were randomly allotted to 3 treatment groups. Single 1-ml injections of isotonic saline solution, carbachol (2 mg/ml), or neostigmine bromide (5 mg/ml) were subcutaneously administered to pigs of groups A, B, and C, respectively. Injections were given midway through parturition in an attempt to hasten the delivery of the last pigs in the litter, where the corresponding incidence of stillbirth is greatest. The mean time of injection was after the birth of 3.5 pigs. Total stillbirths/litter for carbachol-treated (0.23) and neostigmine-treated (0.21) pies were significantly different (P greater than 0.0001) from those for control pigs (0.88). Before injection, stillbirths/litter for control pigs (0.23) were not significantly different from those for carbachol-treated (0.18) or neostigmine-treated (0.12) pigs. After treatment, stillbirths/litter for carbachol-treated (0.06) and neostigmine-treated (0.09) pigs were both significantly different (P greater than 0.0001) from those for saline solution-treated control pigs (0.65). When injected midway through parturition, carbachol and neostigmine reduced stillbirth rate by reducing stillbirths which occur late in farrowing.

Seasonal fluctuations in the farrowing rates (FR( of sows and gilts were determined by analysis of breeding records from 11 herds, covering a total of 26 herd-years of data. Of 22,997 sow and gilt matings, 72.7% resulted in farrowing. For matings during July, August, and September, 60.8% of females farrowed, compared with 76.9% for matings during the remainder of the year. The FR was higher in multiparous sows than in primiparous sows and was lowest in nulliparous gilts. The FR was 65.5% for gilts bred in confinement and for gilts maintained outside. The seasonal fluctuation in FR was similar for confinement and outside-housed gilts. Water sprinkling or evaporative cooling methods did not prevent seasonal fluctuations in the FR of sows or gilts. For sows confined to crates after breeding, the FR was 13.8% higher than for sows in group-housing systems, but the seasonal fluctuation in FR was not substantially altered. It was concluded that the FR of female swine is markedly influenced by season of the year and by parity. The seasonal fluctuations in FR occurred in group- and individually housed swine and in confinement and outside-bred gilts. Water sprinkling or evaporative cooling systems, as used in the herds investigated, appeared to be of questionable value in preventing infertility during the warm months.

Twelve 8- to 12-month-old crossbred boars were inoculated with a virulent strain (NADL-8) of porcine parvovirus (PPV). Hemicastrations were performed on 6 boars 3, 7, 10, 14, 21, and 28 days after an IM injection of 10(8) median cell culture infectious dose (CCID50) of PPV (n = 3) or injection of 10(7.4) CCID50 given intratesticularly (IT, n = 3). Noninfected cell culture medium (0.25 ml) was injected into each testicle of a 7th boar (IT inoculated control). Virus or viral antigen was detected in testicular and epididymal tissues up to 14 days after inoculation. Direct immunofluorescence indicated that viral antigen was mainly associated with the vasculature of the interstitium. Microscopic lesions were not evident in the testicles and epididymides of IM inoculated boars. Acute-to-chronic testicular degeneration was evident in the IT inoculated boars, as well as in the IT inoculated control boar. Six boars were inoculated IM or orally/nasally with 10(7.9) CCID50 of PPV. Semen was collected twice weekly for 8 weeks after inoculation. Virus was not detected in any ejaculates. Semen also was collected from 4 boars for 5 weeks before inoculation, and preinoculation and post-inoculation semen quality was compared. Pronounced changes in sperm output, ejaculate volume, motility, or morphologic defects were not observed. The reproductive consequences of experimental PPV infection in boars were minimal because reproductive function was unaffected and venereal transmission of PPV was not detected.

Gifts from 2 commercial swine operations (farm A and farm B) that were bred each week were tested for porcine parvovirus antibody. On farm A, 21.9% (weekly, 2% to 35%) of the 657 gilts tested over a 16-week period were seronegative within 1 week of mating. On farm B, 17.7% (weekly, o to 40%) of the 164 gilts tested over a 10 week period were seronegative within 1 week of mating. Eighty-one gilts from farm A which were seronegative at time of mating were retested at the end of the gestation. Of the 81 gilts, 4 1 had developed antibody titers. The litter size decreased by 1.3 live pigs/litter. The percentage of small litters (less than or equal to 6 born alive) in the group that seroconverted was 36.6% compared with 10% in the gilts that remained seronegative throughout gestation.

Two groups of finishing pigs at a test station were studied to test the effect of initial weight, weight change in the 1st week, age, breed, and distance the pig was transported on mortality. Total mortality was 5.3% in 1 group and 6.3% in the other group. Specific causes of death were pneumonia (24.7%), gastric ulceration (14.0%), enteritis (6.4%), trauma (4.3%), gastrointestinal displacement (4.3%), rectal stricture (3.2%), porcine stress syndrome (3.2%), and brain abscess (2.2%). Other categories for cause of death were miscellaneous (6.5%), and undiagnosed (31.2%). More pigs died in the last 6 weeks of the 18-week finishing period than in the 1st 6 weeks (P less than 0.05). Death rates were not significantly different between pigs that lost weight and pigs that maintained or gained weight during the 1st week after arrival at the test station. The mean transportation distance to the test station was not significantly different between pigs that died and pigs that survived. Transportation distance was not correlated with mean daily gain. The death rate was significantly (P less than 0.03) higher for Yorkshire pigs than for crossbred, Poland China, Hampshire, and Duroc pigs, and it was significantly (P less than 0.01) higher for Berkshire, Spot, and Chester White pigs than for Hampshire and Duroc pigs.

The age of onset and morphology of the earliest lesions of dyschondroplasias in pigs have not been established. Bones and growth cartilages from pigs were examined for the presence of lesions using radiological, angiomicrographical and histological techniques. Lesions were in 10 of 11 pigs at 15 days of age and 12 of 21 pigs at one day of age, indicating that the condition was congenital. The simplest and apparently earliest lesion was an area of persistent hypertrophied chondrocytes and matrix which extended from the articular-epiphyseal complex or physis into the epiphysis or metaphysis, respectively. Since the prevalence of lesions was high it was considered that the dyschondroplasia may be part of the usual growth pattern of cartilages in contemporary pigs.

Pneumonia and atrophic rhinitis were studied for the second consecutive year in pigs at the same test station. Pneumonia was found to reduce mean daily gain by 3.3% for every 10% of the pig's lungs that had lesions. Atrophic rhinitis did not affect mean daily gain. There was no association between the development of atrophic rhinitis and the development of pneumonia. Pigs that were vaccinated with a Bordetella bronchiseptica bacterin did not have turbinate atrophy scores or mean daily gains different from those in pigs that were not vaccinated. Yorkshire and Hampshire pigs had higher prevalences and severity of pneumonia and atrophic rhinitis, compared with pigs of other breeds.

The purpose of this study was to compare four different techniques that may be used to assess the prevalence or severity of enzootic pneumonia in a swine herd. These techniques included: 1) assessing the percentage of lung involved and calculating a mean percentage and standard deviation for each herd, 2) counting the number of lungs in the herd sample that have greater than a predetermined amount of pneumonia and calculating the prevalence of the sample thus affected, 3) scoring only the lung from each herd sample that was maximally affected by pneumonia, and 4) allocating lungs to categories depending on the approximate extent of pneumonia. Five hundred and sixty pigs from 41 different swine herds in southern Minnesota were examined at slaughter and lungs were evaluated for the extent of pneumonia that was macroscopically visible.The mean percentage of pneumonia for a herd was positively and highly correlated with the standard deviation of that herd (r = +0.914; p < 0.0001), the prevalence of pigs having >/=5% lung involved with pneumonia in that herd (r = +0.946; p < 0.0001) and with the percentage of lung that was observed to be the maximally affected lung in each corresponding herd (r = +0.940; p < 0.001).The most informative procedure was assessing the percentage of lung involved and calculating a mean for the herd sample. Allocating lungs to categories based on approximate severity of pneumonia was less precise and more difficult to interpret. Assessing the prevalence of affected lungs, or evaluating the maximally affected lung was less time consuming and equally as informative for a herd-based indicator, as scoring the percentage of each lung and calculating a mean.

The influence of age at conception, number of matings per conception, season of conception, and breed of female on parity-1 litter size was investigated in 4,944 females from 5 commercial swine herds located in North America. The influence of age at conception on reproductive performance of females in subsequent parities also was investigated. As the age at conception increased from 180 to 245 days, litter size increased 0.017 and 0.012 pig per day, respectively, (P less than 0.05) in 2 of the 3 herds that recorded such data. Age at conception did not influence litter size when conception occurred after 245 days of age. Longevity (parity achieved before death or culling) of females was not influenced by age at first conception. Gilts that conceived before 220 days of age had significantly shorter weaning-to-conception intervals in one herd and shorter farrowing-to-conception intervals in another herd throughout subsequent parities. In 1 of 3 herds that recorded such data, live and total litter size increased from 9.46 to 10.46 and 10.16 to 11.50, respectively (P less than 0.05), as number of matings increased from 1 to 3 per conception. No significant influence of number of matings per conception was observed in the other 2 herds. The effect of season of conception was variable among herds. In 2 herds, there was no significant effect of season of conception on subsequent litter size.(ABSTRACT TRUNCATED AT 250 WORDS)

Two groups of adult boars were inoculated with a field strain of pseudorabies virus (PRV) by intranasal droplet; one group was given 5 x 10(5) median tissue culture infective doses (TCID50), and the other, 5 x 10(6) TCID50. (A third group was maintained as controls.) Ejaculates were examined twice a week for volume, sperm numbers, sperm morphology, and presence of PRV. Severe clinical disease with fever followed administration of the larger virus dose. Death (one boar), testicular degeneration, and transient elevation in spermatozoa with proximal cytoplasmic droplets were seen in different members of this group. The smaller dose resulted in seroconversion, but did not produce signs of disease. In this group, volume, sperm numbers, and sperm morphology did not decline when compared with base-line values or data of control animals. The virus was not isolated from semen. Effects of PRV infection on semen quality in boars seem to be related to the associated clinical signs of systemic disease.

Rats experimentally inoculated with porcine parvovirus (PPV) shed virus in excreta from 3 to 21 days. Rats inoculated subcutaneously with PPV responded serologically with hemagglutination-inhibition titers (512-1,024). The PPV antigen was readily detected in lung and spleen 2 and 3 days after rats were inoculated and in liver and intestine, 4 days. The rats remained clinically healthy. Rats given PPV orally or in drinking water either with PPV-infected cell culture fluid or swine fetal homogenate failed to respond serologically to PPV, the exception being 2 of 4 rats exposed to swine fetal homogenate over a 5-day span. Pigs exposed to PPV-contaminated rat excreta, either by direct oral dosing or by contaminating the feed, failed to seroconvert. Pigs given (IM) PPV which had been isolated on cell culture from rat excreta did seroconvert. Results of these experiments indicated that rats became infected with PPV, but did so after systemic challenge exposure or prolonged oral exposure to highly infective swine fetal homogenate. Insufficient virus was shed by rats to cause susceptible pigs to seroconvert upon oral feeding--thus indicating that a minimal dose is necessary to ensure oral challenge. In a preliminary experiment, seronegative pigs given different doses of PPV orally showed a gradient level of serologic response and different rates of shedding.

The breeding herd records from 7 confinement herds were analyzed to determine the association of season with the frequency of estrus within 1 week after weaning and the farrowing rate following mating during this estrus. All herds utilized the cooling of sows during lactation and water fogging during the postweaning, breeding and early gestation periods. During July, August and September, the frequency of estrus within 7 days after weaning was lower (P < 0.05) than the frequency of estrus during October, November and December. The farrowing rate for matings during September and October was lower (P < 0.05) than the farrowing rate for sows mated from February through May. These data suggest that reduced postweaning estrous activity and fertility may occur in confinement herds, despite the use of cooling systems used to minimize heat stress of sows during hot weather.