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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.