α-Tocopherol and ß-carotene concentrations in feed, colostrum, cow and calf serum in Swedish dairy herds with high or low calf mortality.

BACKGROUND: A study of herd-level risk factors for calf mortality in large Swedish dairy herds showed low serum concentrations of α-tocopherol and ß-carotene in 1-7 day old calves to be more common in high mortality herds. Therefore, we aimed to investigate if calf mortality risk at herd level is associated with concentrations of α-tocopherol and/or ß-carotene at individual level in feed, colostrum, cow and calf serum, while controlling for herd level covariates. Inclusion criteria were affiliation to the Swedish official milk recording scheme, herd size of ≥ 120 milking cows/year, calf mortality risk (day 1-90) of at least 6% (high mortality; HM) or less than 1% (low mortality; LM) and located within one of two regions in southern Sweden. This cross-sectional study was performed in 2010 in 19 (nHM = 9; nLM = 10) dairy herds. Questionnaires were used to collect information about feed and routines for colostrum feeding. Feed (n = 57), colostrum (n = 162), cow serum (n = 189) and calf serum samples (n = 187) were collected and analysed for α-tocopherol and ß-carotene. Other analyses e.g. total serum protein, fat content, and total solids in colostrum were also performed. Linear regression models with vitamin concentrations in feed, colostrum, cow and calf serum as outcome were performed. RESULTS: Calves in HM herds had lower concentrations of α-tocopherol in serum than calves in LM herds, but the effect depended on total protein status in serum of the calf (P = 0.036). Calves from herds that fed transition milk for 3 days or more had higher α-tocopherol concentrations in serum than calves from herds feeding transition milk up to 2 days (P = 0.013). Fat percentage in colostrum was positively associated with α-tocopherol (P < 0.001) and ß-carotene concentrations in colostrum (P < 0.001). A diet containing ≥ 20% (in kg dry matter) maize silage of the total ration was negatively associated with ß-carotene concentration in cow serum (P = 0.001). CONCLUSIONS: High calf mortality risks were associated with lower concentrations of α-tocopherol in calf serum for calves with failure of passive transfer. Feeding transition milk longer was associated with higher concentrations of α-tocopherol in calf serum. In HM herds, evaluation of the calves' α-tocopherol status is recommended.

Streptococcus agalactiae Serotype IV in Humans and Cattle, Northern Europe1.

Streptococcus agalactiae is an emerging pathogen of nonpregnant human adults worldwide and a reemerging pathogen of dairy cattle in parts of Europe. To learn more about interspecies transmission of this bacterium, we compared contemporaneously collected isolates from humans and cattle in Finland and Sweden. Multilocus sequence typing identified 5 sequence types (STs) (ST1, 8, 12, 23, and 196) shared across the 2 host species, suggesting possible interspecies transmission. More than 54% of the isolates belonged to those STs. Molecular serotyping and pilus island typing of those isolates did not differentiate between populations isolated from different host species. Isolates from humans and cattle differed in lactose fermentation, which is encoded on the accessory genome and represents an adaptation to the bovine mammary gland. Serotype IV-ST196 isolates were obtained from multiple dairy herds in both countries. Cattle may constitute a previously unknown reservoir of this strain.

Vaccination against Staphylococcus aureus mastitis in two Swedish dairy herds.

BACKGROUND: Staphylococcus aureus is a common udder pathogen in dairy cows, and may cause severe mastitis problems in some herds. In herds where normal control measures are not successful, vaccination might be an additional tool to use if sufficiently efficient. The aim of the present study was to evaluate the efficacy of a commercially available vaccine (Startvac(®), Hipra, Spain) in two commercial Swedish dairy herds where the control programs for S. aureus mastitis had been unsuccessful. Within each herd cows were randomly assigned to vaccine or control groups, and effects on udder health and milk production during 120 days after calving, and survival during the following lactation were evaluated. RESULTS: A field study was performed in two high producing Swedish herds having approximately 600 (herd A) and 200 (herd B) cows. During 12 months, cows with odd numbers were vaccinated three times around calving according to label protocol, while cows with even numbers constituted the not vaccinated control group. Quarter milk samples for bacteriological culturing were collected from all cases of clinical and subclinical mastitis. The outcome was evaluated during 120 days after calving using data on SCC and daily milk yield at monthly milk recordings, and incidence of mastitis due to S. aureus, coagulase-negative staphylococci, streptococci and coliforms. Cow survival throughout lactation was also studied. In herd A, 239 and 240 cows were included in the vaccinated and control groups, respectively. Corresponding numbers for herd B was 126 and 151 cows. Significant differences between vaccinated and control groups were not found in any of the parameters investigated. CONCLUSIONS: Vaccination with a commercial polyvalent vaccine did not have any beneficial effects on udder health, milk production or survival in two commercial dairy herds with mastitis problems due to S. aureus.

Risk assessment as a tool for improving external biosecurity at farm level.

BACKGROUND: Biosecurity routines at herd level may reduce the probability of introduction of disease into the herd, but some measures may be regarded as expensive and cumbersome for the farmers. Custom-made measures based on individual farm characteristics may aid in improving the actual application of on-farm biosecurity. The aim of the study was to provide a tool for calculating the effects of different biosecurity measures and strategies on the individual farm level. A simple model was developed to assess the risk of disease introduction and the need for biosecurity measures in individual farms. To illustrate the general applicability of the tool, it was applied to theoretical examples of Swedish cattle and pig farms and diseases endemic in those animal species in the EU, in two scenarios with different between-farm contact patterns. RESULTS: The model illustrated that the most important factors affecting the risk, and the effect of biosecurity measures such as quarantine routines and protective clothing, were the frequency of between-farm contacts and prevalence of the disease. The risk of introduction as well as the effect of biosecurity measures differed between farm types and disease transmission routes. Adapting contact patterns to mitigate a specific disease risk was as important as biosecurity measures for some farm types, but the largest effect was seen when combining biosecurity measures with more planned contact patterns. CONCLUSIONS: The risk assessment model proved useful for illustrating the risk of introduction of endemic diseases and the mitigating effect of different biosecurity measures on farm level. Model outputs could be used to justify prioritisation of measures or adapting contact patterns. The theoretic exercise of adjusting model inputs and comparing outputs may help veterinary advisors to understand farm-specific risks and motivate farmers to improve biosecurity in their individual farm, as it can be tailored to each farmer's needs and preferences.

Risk factors for quinolone-resistant Escherichia coli in feces from preweaned dairy calves and postpartum dairy cows.

Quinolone resistance may emerge in gut bacteria (e.g., in Escherichia coli) of animals. Such bacteria could cause infections in the animal itself or be transmitted to humans via the food chain. Quinolone resistance is also observed in fecal E. coli of healthy dairy cattle, but the prevalence varies between farms, not solely as a result of varying degree of fluoroquinolone exposure. The objective of this study was to identify risk factors for the fecal shedding of quinolone-resistant E. coli (QREC) from dairy calves and postpartum cows. Rectal swabs from 15 preweaned calves and 5 postpartum cows per farm were collected on 23 Swedish dairy farms to determine the prevalence of QREC. Risk factors for the shedding of QREC were investigated using multivariable statistical models. Quinolone-resistant E. coli were found on all but one farm. Factors associated with QREC shedding by calves were being younger than 18 d, being fed milk from cows treated with antimicrobials, recent use of fluoroquinolones in the herd, carriage of QREC by postpartum cows, and using the calving area never or rarely as a sick pen compared with often. Factors associated with QREC shedding by cows were calving in group pens or freestalls compared with single pens or tiestalls, purchasing cattle, sharing animal transports with other farmers, and poor farm hygiene. Proper biosecurity and improved hygiene, as well as minimizing fluoroquinolone exposure and waste milk feeding, may be important factors to reduce the burden of QREC on dairy farms.

Risk factors for antimicrobial resistance in fecal Escherichia coli from preweaned dairy calves.

The primary objective of this study was to investigate calf and farm factors associated with antimicrobial-resistant Escherichia coli in the feces of preweaned dairy calves in Sweden. In particular, we investigated the effects of feeding calves colostrum and milk from cows treated with antimicrobials. The secondary objective was to describe the prevalence of resistant E. coli in feces of preweaned dairy calves in Sweden. Fecal samples from 3 calves, aged 7 to 28d, from 243 farms were analyzed for the within-sample prevalence of E. coli resistant to nalidixic acid, streptomycin, and cefotaxime using selective agars supplemented with antimicrobials. In addition, resistance to 12 antimicrobials was tested in one randomly selected E. coli isolate per calf. Information was collected from the farmers via questionnaires regarding the use of colostrum and milk from cows treated with antimicrobials as calf feed and other uses of antimicrobials in the herd. Multivariable zero-inflated negative binomial and logistic regression models were used to assess the effect of various risk factors for shedding of resistant E. coli. Escherichia coli resistant to streptomycin, nalidixic acid, or cefotaxime were isolated from 90, 49, and 11% of the calves, respectively. Resistance to at least one antimicrobial was found in a random isolate of E. coli from 48% of the calves. Feeding colostrum from cows treated with antimicrobials at drying off did not affect the prevalence of resistant E. coli. In contrast, feeding milk from cows treated with antimicrobials during lactation resulted in significantly more nalidixic acid- and streptomycin-resistant E. coli than when such milk was discarded; no significant effect was seen for other resistance traits. Furthermore, an interaction was found between feeding milk from cows treated with antimicrobials and use of fluoroquinolones in cows. In general, the prevalence of resistance was lower for older calves and calves on small farms. Other factors that were associated with the shedding of resistant E. coli were administration of oral dihydrostreptomycin to calves, administration of systemic tetracycline and ceftiofur to cows and calves, housing of the calves, predominant breed of the herd, and geographic location of the farm. The presence of resistant E. coli in calves was clearly due to multiple factors, but minimizing the feeding of milk from cows treated with antimicrobials during lactation should lower the prevalence of resistant E. coli in the gastrointestinal tract of the calves.

Prevalence of bacterial genotypes and outcome of bovine clinical mastitis due to Streptococcus dysgalactiae and Streptococcus uberis.

BACKGROUND: Streptococcus dysgalactiae and Streptococcus uberis are common causes of clinical mastitis (CM) in dairy cows. In the present study genotype variation of S. dysgalactiae and S. uberis was investigated, as well as the influence of bacterial species, or genotype within species, on the outcome of veterinary-treated CM (VTCM). Isolates of S. dysgalactiae (n = 132) and S. uberis (n = 97) were genotyped using pulsed-field gel electrophoresis. Identical banding patterns were called pulsotypes. Outcome measurements used were cow composite SCC, milk yield, additional registered VTCMs and culling rate during a four-month follow-up period. RESULTS: In total, 71 S. dysgalactiae pulsotypes were identified. Nineteen of the pulsotypes were isolated from more than one herd; the remaining pulsotypes were only found once each in the material. All S. uberis isolates were of different pulsotypes. During the follow-up period, the SCC of S. dysgalactiae-cows was significantly lower than the SCC of S. uberis-cows (P <0.05). Median SCC of S. dysgalactiae-cows was 71 500 cells/ml and of S. uberis-cows 108 000 cells/ml. No other differences in outcome parameters could be identified between species or genotypes. CONCLUSIONS: Identical S. dysgalactiae genotypes were isolated from more than one herd, suggesting some spread of this pathogen between Swedish dairy herds. The genetic variation among S. uberis isolates was substantial, and we found no evidence of spread of this pathogen between herds. The milk SCC was lower during the follow-up period if S. dysgalactiae rather than S. uberis was isolated from the case, indicating differences in treatment response between bacterial species.

Associations between bacterial genotype and outcome of bovine clinical Staphylococcus aureus mastitis.

BACKGROUND: Staphylococcus aureus is an important cause of clinical mastitis in dairy cows worldwide. The cure rate after antimicrobial treatment of clinical S. aureus mastitis is very variable due to both cow and bacterial factors. Studies have shown that bacterial genotype might affect short-term bacteriological and clinical cure, but the long-term outcome has been less studied. The objectives of this study were to investigate associations between bacterial genotype and long-term outcome of veterinary-treated clinical mastitis (VTCM) caused by S. aureus during a follow-up period of 120 days and to study genotype variation among Swedish S. aureus isolates. S. aureus isolates from cases of VTCM were genotyped by pulsed-field gel electrophoresis. Long-term outcome measurements used were somatic cell count (SCC), additional diagnoses of VTCM, milk yield and culling. Isolates were classified into clusters (>80% similarity) and pulsotypes (100% similarity). Clusters and pulsotypes were grouped according to occurrence. Multivariable mixed-effect linear regression models including cow and bacterial factors with possible influence on SCC or milk yield were used to calculate differences in SCC or milk yield between groups. Additional outcome measures were calculated using a test of proportions. RESULTS: The isolates (n = 185) were divided into 18 clusters and 29 pulsotypes. Two pulsotypes were classified as common, and were found in 64% of the cases of VTCM. Remaining isolates were classified as less common or rare pulsotypes. The distribution was similar at cluster level. Outcome was calculated from follow-up data on 111 cows. Significantly lower SCC during the follow-up period was found in cows infected with common clusters compared to in cows infected with less common/rare clusters. The proportion of cows with SCC <200 000 cells/ml during the whole follow-up period was significantly higher in the group common clusters than in the group less common/rare clusters. Bacterial genotype did not influence the other outcome parameters. CONCLUSIONS: In Sweden, two S. aureus pulsotypes, identified in about 64% of clinical S. aureus cases, were widespread. Cows infected with the common genotypes had significantly lower SCC during 120 days after treatment compared to cows infected with less common or rare genotypes.

Farming practices in Sweden related to feeding milk and colostrum from cows treated with antimicrobials to dairy calves.

BACKGROUND: Milk produced by cows in receipt of antimicrobial therapy may contain antimicrobial residues. Such antimicrobial-containing waste milk must be withdrawn from human consumption and is therefore sometimes used as calf feed. Unfortunately, this approach might promote selection of antimicrobial resistant bacteria in the calves' intestinal microbiota. The objectives of this study were therefore to obtain an overview of waste milk feeding practices on Swedish dairy farms and to investigate if these practices were associated with certain farm characteristics. A representative group of 457 Swedish dairy farmers participated in a web-based survey with questions about the use of colostrum and milk from cows treated with antimicrobials at dry off or during lactation, respectively, as calf feed. RESULTS: Colostrum (milk from the first milking after calving) and transition milk (milk from the second milking to the fourth day after calving) from cows treated with antimicrobials at dry off was fed to calves on 89% and 85% of the farms in the study, respectively. When antimicrobial therapy was given to cows during lactation, 56% of the farms fed milk that was produced during the course of treatment to calves, whereas milk that was produced during the subsequent withdrawal period was fed to calves on 79% of the farms. Surveyed farmers were less prone to feed such milk if the antimicrobial therapy was due to mastitis than other infections. In Sweden, a majority of antimicrobial treatments during lactation are systemic administration of benzylpenicillin and thus, the bulk of waste milk in Sweden is likely to contain residues of this drug. Feeding waste milk to calves was more common on non-organic farms, and on farms located in Southern Sweden, and was less common on farms with cows housed in cold free stalls barns. CONCLUSIONS: Waste milk that may contain antimicrobial residues is, at least occasionally, used as feed for calves on a majority of surveyed Swedish dairy farms. Future work should focus on the effect of waste milk feeding on the occurrence of antimicrobial resistant bacteria in the calves' intestinal microbiota.

Risk factors for calf mortality in large Swedish dairy herds.

The aim of this study was to identify possible risk factors for 1-90 day calf mortality in large Swedish dairy herds. Sixty herds with a herd size of ≥160 cows were visited once between December 2005 and March 2006. Thirty herds were known to have low mortality (LM) and 30 were known high mortality herds (HM). Upon the visit, data about housing and management was collected from interviews with personnel responsible for the calves. The herd status regarding the calves' passive transfer (total protein), levels of α-tocopherol, ß-carotene and retinol, and excretion of faecal pathogens (Cryptosporidium spp., Escherichia coli F5, rota and corona virus) was evaluated based on targeted sampling of high risk calf groups; in each herd, blood and faecal samples were collected from calves 1-7 and 1-14 days old, respectively. Similarly, the herd status regarding clinical respiratory disease in calves and history of respiratory virus exposure was evaluated based on lung auscultations and blood samplings of calves 60-90 days old. The median calf mortality risk (in calves 1-90 days of age) among HM herds was 9% (Range: 6-24%) and among LM herds 1% (Range: 0-2%). LM and HM herds were compared using five logistic regression models, covering potential risk factors within different areas: "Disease susceptibility", "Factors affecting the gastrointestinal tract", "Factors related to transmission of infectious disease", "Hygiene" and "Labour management". The percentage of calves, 1-7 days old, with inadequate serum concentrations of α-tocopherol and ß-carotene were significantly higher in HM herds compared to LM herds and also associated with higher odds of being a HM herd (OR=1.02; p=0.023 and OR=1.05; p=0.0028, respectively). The variable "Average number of faecal pathogens in the sampled target group" was significantly associated with higher odds of being a HM herd (OR=4.65; p=0.015), with a higher average in HM herds. The percentage of calves with diarrhoea treated with antibiotics was significantly higher in HM herds and was associated with higher odds of being a HM herd (OR=1.08; p=0.021). The median age at death of calves in the age interval 1-90 days that died during a one-year period was significantly lower among HM herds (13 days) than in LM herds (24 days) (p=0.0013) The results indicate that gastrointestinal disorders may be an important cause of calf mortality in large Swedish dairy herds. Furthermore, our study provides additional indications that fat soluble vitamins might play an important role for calf health.

Genotypic variation among Staphylococcus aureus isolates from cases of clinical mastitis in Swedish dairy cows.

The main aim of this study was to examine genotypic diversity of 82 Staphylococcus aureus isolates from cases of acute clinical mastitis in cattle using pulsed-field gel electrophoresis, and to investigate pulsotype differences between geographical regions of Sweden. The work also investigated haemolysis type (alpha, alphabeta), beta-lactamase production, and the association between S. aureus pulsotypes and breed, parity and presence of teat lesions. All isolates came from different farms. In total, 25 pulsotypes were found, but most only once or twice. The most common pulsotype accounted for 26% of the isolates and was found in all regions. The distribution of pulsotypes in the southern region of the country differed from the northern and middle regions. Alphabeta- or alpha-haemolysis was found in 66% and 34% of the isolates, respectively, and beta-lactamase production was found in 9% of the isolates. Variation in haemolysis type or beta-lactamase production was found within some pulsotypes. The results indicate that some pulsotypes have spread widely between herds within the country.

Haptoglobin and serum amyloid A in bulk tank milk in relation to raw milk quality.

The aim of the present study was to evaluate relationships between the presence of the two major bovine acute phase proteins haptoglobin (Hp) and serum amyloid A (SAA) and raw milk quality parameters in bulk tank milk samples. Hp and SAA have been suggested as specific markers of mastitis but recently also as markers for raw milk quality. Since mastitis has detrimental effects on milk quality, it is important to investigate whether the presence of Hp or SAA indicates such changes in the composition and properties of the milk. Bulk tank milk samples (n=91) were analysed for Hp, SAA, total protein, casein, whey protein, proteolysis, fat, lactose, somatic cell count and coagulating properties. Samples with detectable levels of Hp had lower casein content, casein number and lactose content, but higher proteolysis than samples without Hp. Samples with detectable levels of SAA had lower casein number and lactose content, but higher whey protein content than samples without SAA. The presence of acute phase proteins in bulk tank milk is suggested as an indicator for unfavourable changes in the milk composition, e.g. protein quality, due to udder health disturbances, with economical implications for the dairy industry.

Antimicrobial susceptibility of udder pathogens from cases of acute clinical mastitis in dairy cows.

To investigate occurrence of acquired antimicrobial resistance in udder pathogens MICs in Staphylococcus aureus (n=211), coagulase-negative staphylococci (CNS) (n=56), Streptococcus uberis (n=113), Streptococcus dysgalactiae (n=152), Streptococcus agalactiae (n=6), Escherichia coli (n=163), and Klebsiella spp. (n=42) were determined using microdilution. Isolates were from a nation wide survey employing strict inclusion criteria. Presence of acquired resistance was evaluated by species-specific epidemiological cut-off values issued by EUCAST. Penicillin or methicillin resistance in staphylococci were however evaluated by beta-lactamase production or presence of the mecA gene, respectively. Staphylococci were mostly susceptible to antimicrobials tested but 7.1% of S. aureus and 12.5% of CNS were resistant to penicillin by beta-lactamase production. Methicillin resistance was not found in S. aureus. All Streptococcus dysgalactiae and S. agalactiae were susceptible to penicillin. Bimodal MIC distributions for tetracycline in S dysgalactiae and S. uberis indicate acquired resistance in some isolates. Among E. coli 12.3% of isolates were resistant to one or more antimicrobials. Resistance to streptomycin (11.0%), sulphametoxazole (8.6%), ampicillin (7.4%), or tetracycline (4.9%) were the most common traits. Klebsiella spp. were resistant to ampicillin and some isolates also to tetracycline (7.1%) or sulphonamide (9.5%). The study shows that in Sweden bacteria associated with acute clinical mastitis for the most part are susceptible to antimicrobials used in therapy but resistance to penicillin in S. aureus is not uncommon. Penicillin is recommended for treatment of mastitis caused by gram-positive pathogens and regular monitoring of beta-lactamase production in S. aureus is therefore recommended in herds with udder health problems.

Therapeutic effects of systemic or intramammary antimicrobial treatment of bovine subclinical mastitis during lactation.

The short- and long-term treatment efficacy of administrating penicillin for bovine subclinical mastitis during lactation when using intramuscular (IM; 9.5 mg [15,000 IU]/kg bodyweight of benzyl penicillin potassium) injections twice daily for 5 days, or intramammary (IMM; 0.3g [300,000 IU] penethamate hydroiodide) administration once daily for 5 days was compared with a control group receiving no treatment. One hundred and twenty-six cows met the inclusion criteria, which were lack of clinical symptoms, no recent treatment with antimicrobials, and findings of penicillin-sensitive Staphylococcus aureus, Streptococcus dysgalactiae, or Streptococcus uberis in combination with an inflammatory reaction. At follow-up 42-58 days after treatment, the proportion of cows negative for the original infection was significantly higher in IM and IMM groups compared to controls, but the difference between antimicrobial treatment groups was not significant. The udder quarter milk somatic cell count (SCC) was significantly lower at follow-up in IM and IMM groups than in controls, but milk production did not differ between treatments. The culling rate during the 10-month period following treatment was significantly higher in the group treated with IMM penicillin than in the other two groups, but the risk of new mastitis treatments within 10 months did not differ between the three groups. The cure rate was significantly affected by lactation number (lower in older cows), breed (lower in the Swedish Holstein breed), pathogen (lower for S. aureus), and pre-treatment SCC (higher for above average SCC). In conclusion, beneficial long-term effects of antimicrobial treatment during lactation of subclinical mastitis caused by S. aureus, Str. dysgalactiae or Str. uberis were not found in the present study.

Haptoglobin comprises about 10% of granule protein extracted from bovine granulocytes isolated from healthy cattle.

Haptoglobin (Hp) is a plasma protein with haemoglobin binding capacity important in maintaining the iron homeostasis and in disease processes influenced by iron metabolism. In cattle Hp is one of the major acute phase proteins, and increases rapidly during infectious disease. At acute clinical mastitis in dairy cows the Hp concentration increases markedly both in blood and milk. Hepatocytes are considered to be the main origin of Hp, but expression of Hp mRNA has also been found in the mammary gland and leukocytes in healthy cattle. In the present study we show that bovine granulocytes, isolated from peripheral blood of healthy cattle, contain abundant amounts of Hp within the granules. As shown by two-dimensional gel electrophoresis (2-DE) in combination with matrix assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-ToF-MS) bovine granulocyte Hp consists of two sets of peptides ca. 20 kDa (alpha-chains) and ca. 40 kDa (beta-chains) with multiple iso-forms.