Sows intramammarily inoculated with Escherichia coli influence of time of infection, hormone concentrations and leucocyte numbers on development of disease.

The aim of this study was to identify factors that influence the development of disease in sows inoculated with Escherichia coli in the mammary gland. Ten cross-bred primiparous sows were intramammarily inoculated with living E. coli bacteria at different time points before parturition: seven sows within 48 h before parturition and three sows approximately 96 h before parturition. Before and after inoculation, blood samples and mammary gland biopsy specimens were collected and clinical observations were made. All seven sows inoculated close to parturition developed a rectal temperature of >39.5 degrees C during the first 48 h post-partum and two of them also showed other signs of clinical disease. In the sows inoculated 4 days before parturition, the rectal temperature never exceeded 39.5 degrees C during the first 48 h post-partum and none of them showed any other sign of clinical discase. There was a tendency (P < 0.1) that histological signs of mastitis were more frequent in the sows inoculated close to parturition. There were no overall differences between the two groups of sows in plasma concentrations of cortisol, oestradiol-17beta and 15-ketodihydro-PGF2alpha before inoculation. Before inoculation, the number of neutrophils in the blood was overall higher (P < 0.05) in the group of sows that were inoculated close to parturition. In comparison, the number of lymphocytes before inoculation had a tendency (P < 0.1) to be lower in that group. The data suggest that the time of infection of the mammary gland relative to parturition and the number of circulating neutrophils at the time of infection influence the development of chinical coliform mastitis in the sow.

Experimental infections with Actinobacillus pleuropneumoniae in pigs--I. Comparison of five different parenteral antibiotic treatments.

SPF pigs aged 10 weeks were infected intranasally with Actinobacillus pleuropneumoniae serotype 2. After the onset of clinical symptoms of respiratory disease, which occurred 20 h post-infection, parenteral treatment with ceftiofur, danofloxacin, enrofloxacin, penicillin or tiamulin was initiated (n = 8 per group). Untreated groups, of which one was infected, served as controls. The uninfected control group did not show any signs of disease, while the infected control group was severely affected by the infection and also expressed a decreased weight gain following the challenge. Based on clinical signs, the magnitude of pathological lesions in the respiratory tract found at necropsy performed 17 days post-infection and the number of reisolates of A. pleuropneumoniae made at necropsy, treatments with the quinolones (danofloxacin and enrofloxacin) and the cephalosporine (ceftiofur) were superior to those with penicillin and tiamulin. The latter groups also developed antibodies to A. pleuropneumoniae to a larger extent. Some of the pigs treated with ceftiofur and danofloxacin developed antibodies to A. pleuropneumoniae, and the microbe was reisolated from approximately 50% of these animals. In contrast, pigs treated with enrofloxacin did not develop antibodies to A. pleuropneumoniae, and the challenge strain was not found at necropsy. The performance with respect to daily weight gain and feed conversion corresponded well with the clinical signs developed and the findings made at necropsy. The decreased growth recorded during the acute phase of the disease was, to a large extent, caused by a reduced feed intake.

Experimental infections with Actinobacillus pleuropneumoniae in pigs--II. Comparison of antibiotics for oral strategic treatment.

The present study was aimed at scrutinizing the efficacy of oral antimicrobial treatments at experimental challenge using a strain of Actinobacillus pleuropneumoniae serotype 2 known to cause severe disease. SPF pigs aged 10 weeks were infected intranasally and the antimicrobial treatments were initiated 5 h prior to that exposure. Several antimicrobial drugs, as well as the length of the treatment period, were elucidated. The outcome of the challenge was monitored by registration of clinical symptoms, weight gains and the development of serum antibodies to A. pleuropneumoniae. At necropsy, the magnitude of pathological lesions in the respiratory tract and the rate of reisolation of the infective strain were recorded. Animals that became diseased displayed a decreased growth rate caused, to a large extent, by a reduced feed intake. The performance with respect to daily weight gain and feed conversion corresponded well with the clinical signs developed and serologic reactions, as well as with the findings made at necropsy. The results obtained among pigs treated with enrofloxacin, but also with florfenicol or chlortetracycline, were superior to those of pigs treated with penicillin, tiamulin or tilmicosin. A positive effect was obtained using a strategic in-feed medication against infection with A. pleuropneumoniae. Provided that the drug used is effective against the target microbe, initiating treatment prior to infection appeared to be more important than the length of the treatment. It should, however, be remembered that A. pleuropneumoniae was reisolated from all but one medicated group following an experimental challenge given after initiating the medication. Consequently medical treatment as described did not eradicate the microbe.

A long-term study on the health status and performance of sows on different feed allowances during late pregnancy. II. The total cell content and its percentage of polymorphonuclear leucocytes in pathogen-free colostrum and milk collected from clinically healthy sows.

The main objective of this study was to determine the total cell content, TCC, and the percentage of polymorphonuclear leucocytes, PMNLs, in colostrum and milk collected from sows during the first 22 days of lactation. The pH-values during the same sampling period were also determined. It should be emphasized that all the values obtained emanate from bacteriologically negative colostrum and milk. The potential influence of different levels of late gestation feeding regimes was also evaluated. The TCC-values obtained from milk samples during the first 3 weeks of lactation and exceeding the designated threshold of 10 x 10(6) cells/ml varied between 4% and 21%. Within the TCC-limitation of 10-19.99 x 10(6) cells/ml neither the preceding nor the succeeding cell counts exceeded the threshold in 26.8%. TCC-values above 19.99 x 10(6) cells/ml were preceded and succeeded by cell counts below the threshold in 58.8% and 58.8%, respectively. The TCC-levels below the threshold of 10 x 10(6) cells/ml, expressed as geometric least square means, increased significantly from day 1 to day 3 (1.23 x 10(6) cells/ml versus 1.86 x 10(6) cells/ml) and decreased thereafter gradually to day 22 (1.38 x 10(6) cells/ml). When all values were included, the TCC-values increased in a similar pattern from day 1 to day 3 (1.38 x 10(6) cells/ml versus 3.18 x 10(6) cells/ml). The value on day 22 of lactation was still on a significantly elevated level compared with that of day 1 (2.10 x 10(6) cells/ml versus 1.38 x 10(6) cells/ml). The 2 different feeding regimes were not found to influence the TCC-values during the first 22 days of lactation. In the whole material the PMNL-values, expressed as percentages of the TCC, declined from approximately 60% on day 1 of lactation to between 40% and 50% for the remaining sampling period. This decline was comparable with the one seen in the cell class below the threshold of 10 x 10(6) cells/ml. In the 2 cell classes above 9.99 x 10(6) cells/ml, 78.0% and 88.8% of PMNLs on day 1 declined to about 40% on day 22. This might indicate an inflammatory response on day 1 but without any detectable bacteriological growth. The increase in lactation number, if lactation 1 was compared with the following lactations, revealed a significant rise (p < 0.05) in TCC-level and percentage level of PMNLs. A stepwise and significant increase in pH-level occurred between days 1, 3 and 8 (6.18, 6.56, 7.03) followed by a significant decrease to day 22 (6.91) when pH-values from milk of all cell classes were included.

A long-term study on the health status and performance of sows on different feed allowances during late pregnancy. III. Escherichia coli and other bacteria, total cell content, polymorphonuclear leucocytes and pH in colostrum and milk during the first 3 weeks of lactation.

The objectives of this study were to (1) estimate the clinical status of the mammary glands and (2) compare it with the bacteriological findings, the total cell content (TCC) and its percentage of polymorphonuclear leucocytes (PMNLs) and pH in colostrum and milk secretion of sows on 2 different feeding regimes, high versus low, during late pregnancy. The milk samples were collected from both agalactia post partum (APP) sows and clinically healthy sows. Sows with a rectal temperature exceeding 39.5 degrees C within 48 h after parturition were considered to be diseased in APP and treated medically. The sows were sampled on days 1, 3, 8 and 22 of lactation during 6 consecutive lactations. Irrespective of feeding regimes, 49 out of 77 lactations among the APP sows and 15 out of 96 lactations among the clinically healthy sows revealed E. coli in pure cultures with a concomitant TCC exceeding 10 x 10(6) cell/ml already on the first day of lactation. The healthy sows with E. coli infection were denominated as being subclinically infected sows. The intensity in growth of E. coli successively declined, and the bacteria were finally eliminated between days 3 and 8 of lactation. The TCC were 82 x 10(6) cells/ml and 157 x 10(6) cells/ml in the clinically and subclinically E. coli infected glands, respectively, on the first day of sampling. The TCC declined gradually in both groups of sows, but was still higher than in bacteriologically negative milk on day 22 of lactation. The percentages of PMNLs were 66% and 79% in clinically and subclinically infected glands, respectively, on day 1 of lactation, thereafter decreasing to approximately 50% on day 22 of lactation in both groups of sows. In APP sows, swelling, reddening and/or soreness were registered in 38 out of 87 mammary glands with E. coli mastitis on the first sampling occasion. The TCC in bacteriologically negative colostrum and milk collected from APP sows on day 1 of lactation was significantly higher, 2.27 x 10(6) cells/ml, when compared with the TCC in bacteriologically negative milk secretion from the clinically healthy or subclinically infected sows, 1.38 x 10(6) cells/ml versus 1.51 x 10(6) cells/ml, respectively. The PMNLs were higher on day 1 in clinically healthy sows, 59.6%, than in subclinically infected and APP sows (43.5% and 48.3% respectively). The pH in secretion from clinically or subclinically E. coli infected glands (6.57 versus 6.46) were higher than in bacteriologically negative colostrum samples (6.29) from clinically diseased sows on the first day of sampling. On day 22 of lactation, pH-values had stabilized on a level of approximately 7.00 in all milk samples from earlier bacteriologically positive or negative mammary glands. The 2 feeding regimes, low versus high, were not found to influence TCC, PMNLs or pH except for TCC in bacteriologically negative samples of APP sows (2.69 versus 3.62). The lactation number influenced the PMNLs in both groups of sows with E. coli infected mammary glands, and both the TCC and PMNLs in bacteriologically negative colostrum and milk.