Browsing by Organization "Helsingfors universitet, veterinärmedicinska fakulteten, institutionen för klinisk produktionsdjursmedicin"

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  • Orro, Toomas (Helsingin yliopisto, 2008)
    The early protection mechanism of the host against infection, trauma or other tissue damage comprises a set of reactions known as the acute phase response (APR). During APR, circulating concentrations of acute phase proteins (APPs) change. These proteins can serve as indicators of host response during various inflammatory conditions. In this thesis, APR in reindeer was investigated for the first time. Systemic concentrations of APPs during the neonatal period were studied in reindeer and cattle. APPs were also investigated during spontaneous bovine respiratory disease (BRD) in dairy calves. Escherichia coli endotoxin challenge in adult reindeer increased concentrations of serum amyloid A (SAA) in all animals. Haptoglobin (Hp) showed a less pronounced increase. SAA and Hp were concluded to be acute phase reactants in reindeer. In reindeer calves SAA concentrations increased during the first 2 weeks of life and decreased afterwards. Serum Hp concentrations increased throughout the first month after birth. In dairy calves SAA and lipopolysaccharide binding protein (LBP) concentrations changed similarly during first month of age as in reindeer calves. However, Hp concentrations generally remained low after birth. SAA rise in calves were not derived from colostrum as mammary specific SAA isoforms were not found from calves serum samples. Results of these two studies indicated that newborn reindeer and dairy calves have an inflammatory response during the first weeks of life and the age of young animals should by considered when interpreting APP concentrations. Very similar SAA changes in the two ruminant species also suggest that this inflammatory response may have role in the adaptation process of newborns to extrauterine life. The effect of different bovine respiratory pathogens on concentrations of APPs (SAA, LBP, Hp, alpha1-acid glycoprotein and fibrinogen) was studied in calves. Isolation of Pasteurella multocida was associated with increased concentrations of all APPs tested. In another study, concentrations of APPs were investigated in dairy calves during an outbreak of BRD. Initial cause for BRD outbreak was bovine respiratory syncytial virus (BRSV) infection. Concentrations of SAA and LBP increased in parallel with clinical symptoms at week 1 and peaked at week 3 of outbreak. Some calves had high Hp concentrations at week 3. Higher SAA, LBP and Hp concentrations at a later stage of BRD (week 3) were associated with lower BRSV-specific IgG1 production, suggesting that these calves had enhanced inflammatory response to secondary bacterial infection. In conclusion, APPs proved to be useful in exploring host response in bovine respiratory infections.
  • Taponen, Suvi (Helsingin yliopisto, 2008)
    Bovine mastitis caused by coagulase-negative staphylococci Mastitis is the most common disease affecting dairy cows, and staphylococci are the most common cause of mastitis. According to Finnish studies, staphylococci are isolated from 36% of clinical and 60% of subclinical mastitis cases. In mastitis diagnostics, staphylococci are divided into coagulase-positive and coagulase-negative based on their ability to coagulate plasma. Majority of staphylococcal mastitis is caused by coagulase-negative staphylococci (CNS). In mastitis diagnostics they are not identified at species level but are treated as a uniform group. Usually they cause subclinical or mildly clinical mastitis, and are considered as harmless bacteria of the normal skin flora. CNS mastitis is most common on the first lactation. It is assumed to cure spontaneously and antimicrobial treatment is not recommended. Although usually subclinical or mildly clinical, CNS mastitis causes increase of milk leucocytes and may decrease the milk quality. CNS mastitis seems to be especially a problem in well managed dairy herds with good udder health. In contrast to the usual assumption that CNS mastitis cures spontaneously, it may persist in the udder throughout the entire lactation. In addition, the CNS species are not necessarily a uniform group but differences between the species in virulence and clinical characteristics may exist. In this dissertation, different aspects of bovine mastitis caused by CNS were studied. The response of CNS mastitis to antimicrobial treatment was investigated, as well as the persistence of CNS intramammary infection when left without antimicrobial treatment. The prevalence of different CNS species in mastitis and on cows skin, and possible differences in clinical characteristics and persistence between CNS species were studied. Species identification was performed based on bacterial phenotype and genotype. Identification using different methods was compared. Majority of CNS mastitis was caused by S. chromogenes or S. simulans. Many other CNS species were isolated from mastitis sporadically. Molecular genetic identification methods based on bacterial genotype proved more reliable than biochemical methods based on bacterial phenotype. In some cases the identification results of genotypic and phenotypic methods disagreed. About half of CNS mastitis detected during lactation persisted without antimicrobial treatment, commonly until the end of lactation. Mastitis caused by penicillin-susceptible CNS cured well, about 90% cured. Of mastitis caused by penicillin-resistant CNS, 60 to 70% cured, although the causing bacteria were susceptible to the antimicrobial used. Most often CNS mastitis was subclinical or mildly clinical. Statistically significant differences in clinical characteristics or persistence between the two most common CNS species were not detected.
  • Rikula, Ulla Kaisa (Helsingin yliopisto, 2008)
    Canine distemper (CD) is one of the longest-known infectious diseases of dogs and many other carnivores. Control of CD among dogs relies heavily on vaccination, while in fur farms and zoos biosecurity measures in some cases offer the only available means for CD control. Modified live CD virus vaccines have been successfully used to control CD among farmed mink, and since no licensed vaccines for other species kept for fur exist, they have also been used for foxes and raccoon dogs in CD emergency situations. CD vaccines for dogs and mink were studied in experimental settings for their ability to induce virus-neutralising (VN) antibodies in target species. Mink vaccines were also assessed in silver foxes, blue foxes and raccoon dogs. Purpose-bred beagle dogs were vaccinated twice with one of three CD vaccines: Candur® SHP, Canlan®-3 or Dohyvac® DA2P, and the levels of VN antibodies were determined at the time of vaccination and one month after the second vaccination. Fur animals were vaccinated once with Distemink®, Distem®-R-TC or vaccine 3 and the levels of VN antibodies were determined at vaccination and 2-4 times 1-4 months afterwards. Significant differences among vaccine groups were found both in the proportion of animals with measurable levels of VN antibodies and in the mean titres of antibodies. The levels of VN antibodies were also determined from a large field sample (n = 4 627) of vaccinated dogs. In addition to the three CD vaccines in the seroconversion study above, additional two vaccines, Duramune®-4 and Nobivac® DHP, had been used in the field. Each dog with a known vaccination history, date of birth, sex and breed was sampled once. Based on the overall geometric mean titre of the dogs vaccinated with a single vaccine brand, vaccines were divided into high-take (Candur®, Nobivac® and Duramune®) and low-take (Dohyvac® and Canlan®) groups. The vaccine groups differed significantly among dogs less than two years of age both in the proportion of dogs with detectable VN antibodies and in the mean titres. Both the number of vaccinations and age were associated with the titre and vaccine usage. To control for possible confounding factors, the comparison of titres among vaccine usage groups was adjusted by classifying them according to the number of vaccinations (one to four) and the age group (less than one, one to two, or over two years old). The same division into low- and high-take vaccines was observed, irrespective of the number of vaccinations the dogs had received. The observations of this seroprevalence study regarding Candur®, Canlan® and Dohyvac® were consistent with the results of the seroconversion study. CD was reintroduced into Finland in 1990 after 16 years of absence. The disease remained at a low endemic level in 1990-1994, reached epidemic proportions in 1994-1995 and disappeared during 1995. The epidemic also involved vaccinated dogs. Among the virologically-confirmed cases the proportion of Dohyvac®-vaccinated dogs was higher than expected from the market shares on the assumption that all the vaccines had an equal take. As a result of this observation, Dohyvac® was withdrawn from and Nobivac® and Duramune® introduced to the market during 1995. A drastic redistribution of the market shares between the low-take and high-take vaccines took place, and this coincided with the decline and dying out of the outbreak. The observed occurrence pattern of CD from 1990-1996 was largely attributed to the changes in the level of HI, although the possible contribution of other factors, such as developments in the dog demographics, was also recognized. It was concluded that an HI above 75% is needed to keep CD in check, i.e., only sporadic cases of CD, at most, can occur. With the currently used vaccines an HI of 80% corresponds to a vaccine coverage of some 94%. It was concluded that the development of vaccine-induced immunity is a multifactorial process depending on the properties of the vaccine, on the individual variation, age, species and other factors influencing the immunocompetence of the host. On the individual level the prevention of clinical signs is sufficient, but on the population level, halting the circulation of the virus is crucial for the definitive control of CD. The ultimate test and criterion for a vaccine is its contribution to herd immunity.
  • Hälli, Outi (Helsingin yliopisto, 2008)
    Seasonal infertility is well-defined phenomenon in modern swine production. The outcomes mostly affected are age at puberty in gilts, weaning-to-oestrus interval (WOI) and farrowing rate in sows. The European wild boar, the ancestor of our domestic pig, is a distinct short-day seasonal breeder. Photoperiod is thought to be the most important regulating factor in seasonal breeders. In addition to photoperiod, many environmental and management factors are known to adjust the manifestation of seasonal infertility. The aim of this work was to obtain information about the effect of photoperiod on reproductive endocrinology and on reproductive performance. In addition, the effect of re-modelling the piggery breeding unit on farrowing rate was studied. In the first clinical trial (I), two light regimes were tested in experimental conditions. One group of ovariectomized gilts (16 domestic pigs and 4 European wild boars) was kept under short daylight conditions (8-h light, 16-h dark) and the other group under long daylight conditions (16-h light, 8-h dark). After the treatment period, LH secretion patterns were determined by repeated blood sampling. In contrast to our expectations, LH pulse frequency remained unchanged in both light regimes. However, in the domestic pig, mean and basal LH concentrations were higher in the long-day group than in the short-day group. To investigate the two light regimes under more practical conditions, two trials (II, III) were conducted in commercial piggeries. The outcomes were farrowing rate and WOI. In trial II, the long-day group was kept under a constant 16-h light, 8-h dark regime. The short daylight regime consisted of a light phase of 8-h and a dark phase of 16-h in farrowing and breeding units. The length of the short-day treatment was 6 weeks before breeding. In the gestation unit, the short-day animals were also kept under a 16L:8D regime. The results of this trial revealed that the farrowing rate was 90% in both groups, and the two treatment groups also shared the same median WOI, i.e. 5 days. In trial III, the long daylight regime consisted again of a constant long-day treatment. However, the photophase was 14L:10D. The short-day treatment was extended to 8 weeks and took place exclusively in the farrowing unit. The light regime was 10L:14D. The short-day group was also kept under a 14L:10D regime in the breeding and gestation units. Despite these modifications, the results were the same as in the previous trial. The farrowing rate was 90% and median WOI five days in both groups. The last part (IV) of this thesis was an observational retrospective cohort study with a historical control. A cohort of farms with individual cages in their breeding unit was chosen. These farms either remodelled their breeding cages or switched to different group housing systems in the breeding unit. The farrowing rate before and one year after the remodelling was then compared. The remodelling itself was shown to affect reproductive performance on these farms. In conclusion, the reproductive performance of sows is difficult to control by a single environmental (photoperiod) or management (housing strategy) factor.
  • Oravainen, Jonna (Helsingin yliopisto, 2008)
    More than half of the sows in Finland are culled every year. The most common reason for culling is fertility problems, followed by lameness. The main infectious reproductive diseases to consider here are porcine parvovirus (PPV) and vulvar discharge syndrome (VDS). The objectives of this study were to investigate PPV, VDS and lameness among loosely housed sows by determining their prevalence and effect on fertility. In addition, the response of gilts to PPV vaccination was followed with haemagglutinin inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) tests and examined with regard to reproductive success. Bacterial growth, antimicrobial susceptibility and cytological and vaginoscopic findings were evaluated in VDS animals, and the potential usefulness of two acute-phase proteins, haptoglobin (Hp) and C-reactive protein (CRP), in VDS and in lameness diagnostics was assessed. To examine the herd prevalence of high PPV titres, a minimum of 11 blood samples on each of 21 randomly chosen farms were drawn. High PPV titres was found to be common; on 17 farms (81%) at least one animal had a high titre (>1:512), and 44% of all animals sampled had a high titre. The factors found to have a significant effect on HI titres were herd size and parity of two or higher. Thirty-nine gilts from four herds endemically infected with PPV were injected twice with a commercial PPV vaccine. The antibody response was studied, revealing a consistent increase in humoral immunity. PPV antibodies were analysed both with HI and ELISA, and the agreement between them was moderate. A potential association between high antibody titres and reproductive failure was also investigated, but no association was observed. The effect of VDS on sow and gilt fertility was evaluated on 26 farms. Fewer VDS animals (47.4%) than non-VDS animals (68.3%) farrowed at the first chance after the examination. Factors associated with farrowing were VDS, reproductive status, availability of roughage and confinement to individual stalls. None of the variables tested was associated with VDS. There was an absence of a systemic acute-phase response, as indicated by low concentrations of Hp and CRP. A total of 21 sow herds were randomly chosen to determine the prevalence of VDS. The median VDS prevalence was low, 0% (range 0-4.5%). Nine of the 655 animals (1.4%) examined displayed signs of VDS. Detection of vulvar discharge was associated with vaginoscopic examination findings and with bacteriology. Seven of the 16 bacterial isolates (44%) were considered to be resistant or to have intermediate susceptibility to at least one of the antimicrobial agents tested. Lameness was a frequent finding in the 21 herds studied: 8.8% of the animals were lame. Lame animals had higher Hp and CRP concentrations than sound-footed controls. Animals housed on slatted floors had 2-fold odds of being lame and 3.7-fold odds of being severely lame as compared with animals housed on solid floors. Higher parity and use of roughage increased the odds of farrowing; however, lameness did not increase the risk for not farrowing.
  • Munsterhjelm, Camilla (Helsingin yliopisto, 2009)
    Commercial pig production presents the animals with a multitude of potentially stressful challenges. Distress is a threat to animal welfare and may impair productivity. This research aimed to investigate productivity of pigs in relation to some common practices of pig production known to be stressful, to estimate the amount of stress or the level of welfare of the animals, and to establish relationships between stress or animal welfare measures and productivity. To address these issues, four studies were carried out. Studies I and II investigated effects of moderate enrichment on behaviour, basal cortisol secretion, health and daily gain in growing pigs (0-21 weeks of age). Effects of both current and early environmental enrichment were investigated. Small groups with siblings were accommodated in pens either barren or enriched with a moderate amount of chopped straw and wood shavings. Six enrichment regimes were used involving a stable environment or changes in enrichment status at 5 and/or 9 weeks of age. Enriched as compared to barren housing increased average daily gain and decreased post-weaning diarrhoea in the nursery. Current housing, as well as the early environment (0-4 or 0-9 weeks of age), affected stress physiology as measured by behaviour and basal cortisol secretion. Barren housing or experience thereof caused signs suggestive of chronic stress. Stress indicators were not associated with productivity. These results support the use of enrichment for pigs in early life, especially if bedding is scarce later in life. Study III compared the fertility of sows housed either individually or in groups on deep litter from weaning to four weeks of pregnancy. Stall housing decreased the odds for early disruption of pregnancy and increased the odds for pregnancy at day 28 post-service. The causes remained undisclosed, but social stress during short periods of time around oestrus and early pregnancy was proposed. Behavioural indicators showed clear signs of stress in stalls, but behaviour was not associated with fertility. The level or type of stress in stalls may have been insufficient to affect reproduction. These results emphasize the need for a better understanding of factors impairing fertility in sow groups. In Study IV the welfare status of pigs on commercial farms was assessed using an environment-based index comprising several subscales. Welfare scores were regressed on fertility measures. Good-quality floors and stockmanship were the most influential predictors of good fertility, providing some evidence of an association between higher levels of animal welfare (i.e. low levels of distress) and good reproductive performance.
  • Alm-Packalén, Karoliina (Helsingin yliopisto, 2009)
    The economic importance of a high breeding efficiency in sows and dairy cows emphasizes the benefit of accurate prediction of fertility of boar and bull semen. The artificial insemination (AI) studs need an objective and rapid, but inexpensive, method to evaluate ejaculates. We developed a new quick and easy fluorescence method for frozen-thawed bull semen that uses an automatized fluorometer and the fluorophore stain propidium iodide that stains only cells with damaged membranes. The fluorescence of the semen sample and the totally killed subsample were measured simultaneously and viability was calculated. For fertility evaluation, the non-return rates (NR%) obtained from 92,120 inseminations with the analyzed batches were recorded. The correlation between the total number of viable spermatozoa in the insemination dose and field fertility was low but significant, suggesting that plasma membrane integrity evaluation can serve as a cost-effective quality control method for frozen-thawed semen at bull AI stations. In the second study we describe a sudden, though long-lasting, drop in bull semen quality at an AI station. During five consecutive months, the number of rejected ejaculates and discarded frozen semen batches due to poor motility increased, and the number of all forms of abnormal spermatozoa increased. However, for the accepted ejaculates, a 60-day NR% was normal. The previous summer had been rainy, and the hay used in the AI station was visibly moldy. Immunoassay and gas chromatography-mass spectrometry detected Fusarium mycotoxins HT-2 and T-2, but no zearalenone in the hay. Occurrence of mycotoxins such as T-2 and HT-2 in the moldy hay coincided with, and may have been responsible for, the impaired semen quality in AI-bulls. In the third study we describe the deteriorating effects of Bovine Respiratory Syncytial Virus (BRSV) epizootics on sperm quality in young AI bulls. The disease caused by BRSV is often mild in animals older than 6 months and is therefore neglected. However, it seems to be able to cause testicular fibrosis and disturbances in sperm morphology, thus requiring attention at AI stations with valuable breeding animals. In the remaining two studies we concentrated on boars and studied the effect of altering insemination dose, sperm morphology and insemination technique (traditional vs. intrauterine insemination). The insemination dose for boars should exceed 3 x 109 spermatozoa under commercial circumstances to avoid decrease in prolificacy at farms. Morphological examination of spermatozoa requires some experience, but it is quite an easy and inexpensive method to screen-out overtly poor-quality ejaculates. Therefore, we suggest routine morphological examination of all young boars entering the AI station and regularly thereafter. The intrauterine insemination was easy and fast to perform in sows, but it did not result in marked increase in NR% or litter size when inseminating with 3 x 109 spermatozoa / dose. This thesis focuses on different aspects affecting male reproduction. In the research projects we studied the deleterious effects of trichothecenes in feed and BRSV infection on sperm quality, developed a new method for sperm viability determination as well as studied the importance of semen quality and insemination dose for reproductive success.
  • Haveri, Maarit (Helsingfors universitet, 2008)
    Staphylococcus aureus, one of the most common causes of bovine intramammary infections and mastitis in modern dairies, is easily transmissible and respond poorly to treatment. Some S. aureus strains are better adapted to infect the mammary gland, whereas others are less important as a cause of mastitis. Identification of these strains can be possible using the tools of molecular microbiology. The aims of this thesis were to determine prevalence of bovine S. aureus intramammary infection in Finnish dairy herds, to study antimicrobial resistance of bovine S. aureus with focus on methicillin and penicillin resistance, to investigate whether differences in clinical significance exist between S. aureus strains and to establish if certain strain types or determinants for virulence can be specifically linked with mastitis. Finally, reservoirs and transmission of S. aureus in two herds with different management regimes were studied by collecting S. aureus from cases of mastitis and from extramammary sites (teat skin, teat canals and skin lesions, milking liners, hands and nostrils of the milking personnel). The results from a nationwide survey indicated that S. aureus remains a significant mastitis pathogen in Finland as both the prevalence of quarters (3.4%) and the prevalence of cows infected by S. aureus (10.2%) has remained nearly stable. The proportion of S. aureus representing a mastitis-causing agent decreased from the previous survey of 1995, but the total number of quarters that were positive for bacterial growth significantly increased. S. aureus was isolated from two-third of the herds. According to field data collected from 1993 to 1997 among the 22 S. aureus pulsotypes identified, five pulsotypes dominated as the cause of S. aureus mastitis and 17 pulsotypes were sporadic. In the two herds of study IV, S. aureus was isolated from 85% of the cows from intramammary infections, udder skin, wounds, milking equipment, and from hands and nostrils of the milking personnel. One or two strains dominated in these herds. The diversity of strains was higher in the herd, which purchased cattle as compared with the closed herd. Compared with the previous surveys, the proportion of penicillin resistant, β-lactamase producing S. aureus remained almost stabile but was still high, approximately 50%. Penicillin resistant S. aureus were isolated in almost one-half of the survey herds. sed and sej permanently co-existed with the penicillin-resistance gene blaZ, suggesting the presence of a penicillinase plasmid in these strains. Methicillin-resistant isolates was not detected. The clinical signs, acute local response and persistence differed significantly between the predominant strains. S. aureus strains that had the putative penicillinase plamid were overrepresented in persistent mastitis and these persisted significantly more often compared with the strains containing blaZ only. This suggests that among penicillin-resistant blaZ positive strains, a subgroup of strains containing sed and sej may be more likely linked with chronic mastitis than the other subgroups. Information on the ecology, epidemiology and characteristics of S. aureus presented in this thesis may be useful for planning control strategies in herds with problems of S. aureus mastitis. Diagnosis to strain level and determination of certain virulence determinants would be necessary to target measures against infections caused by specific strains. This would require molecular techniques feasible also for field use.
  • Hovinen, Mari (Helsingin yliopisto, 2009)
    Automatic milking (AM) is increasing in modern dairy farming. It is replacing conventional milking (CM), managed by a milker in a milking parlour or in tie stalls. In the research reported in this thesis, the udder health of dairy cows changing from CM to AM was examined and found to deteriorate slightly more than that of cows changing from tie stall to free stall barns with conventional milking during the first year after the change. Deterioration was indicated by a slight increase in the somatic cell count (log SCC) of the milk and in the proportion of new high SCC cows. In both groups of cows, log SCC already increased before the change, and an adaptation period of 2 to 3 months was recorded after the change from CM to AM. Udder health appeared to stabilise close to the original values towards the end of the study period in both groups, but no improvement was noted in log SCC in the herds changing from CM to AM. Additional aims of the work were to investigate different methods of automatic mastitis detection and teat cleaning to identify possible risk factors for mastitis in AM. On average, more than 80% of teat cleanings in 9 herds using 2 different AM systems were technically successful. Factors associated with the result were the herd, teat cleaning method, days in milk, behaviour of the cow, teat colour, udder and teat structure, and teat position. Excessive udder hair or technical failure of the AMS disturbed teat cleaning. Nearly 80% of originally dirty teats became totally or almost clean during the cleaning process. Factors associated with the effectiveness of teat cleaning were teat cleanliness before cleaning, the herd, teat cleaning method and teat end condition. The same farms were used to evaluate the efficiency and precision of mastitis detection methods in AM. The sensitivity of detecting quarters with subclinical mastitis (threshold value of 200 000 cells/ml milk) was only < 20% based on electrical conductivity (EC). However, 75% of the quarters with clinical mastitis were detected by the AM system. By manipulating the alert criteria based on EC, 60 to 70% true positive alerts could be achieved. Deviations in milk yield caused numerous false positive alerts, but > 60% of alerts based on deviations in milk colour were true positives. A new non-invasive method for detecting clinical mastitis using a thermal camera was assessed in 6 cows with experimental endotoxin-induced mastitis. The first systemic and local signs were seen within 2 hours post-challenge. However, the thermal camera only detected a temperature change of >1 °C on the udder skin of all cows after four hours post-challenge, in parallel with the rise in rectal temperature, milk SCC and milk EC. Nevertheless, a thermal camera mounted in a milking or feeding parlour in AM could be useful for detecting temperature changes associated with clinical mastitis and other febrile diseases, between milkings or in dry cows. The results of this thesis suggest that udder health slightly deteriorates during the first year after the introduction of AM. The studied risk factors can partly be controlled by management actions taken by the farmer, but further technical development of AM is still necessary. “Automatic” does not indicate that the role of the herdsman is in any way diminished.