Effect of prepartum energy balance on neutrophil function following pegbovigrastim treatment in periparturient cows

Treatment with granulocyte colony-stimulating factor (G-CSF) increases polymorphonuclear cell (neutrophil) count and enhances neutrophil function in the periparturient cow. Prepartum undernutrition was hypothesized to reduce the effect of a commercially available recombinant bovine G-CSF product (pegbovigrastim) on neutrophil count and function. Hence this study was undertaken to test the effect of undernutrition for approximately 1 mo before calving on the innate immune response to pegbovigrastim. Cows (n = 99) on pasture were blocked by expected calving date and body condition score and randomly assigned in a 2 × 2 factorial design. The first factor was that cows were fed to exceed energy requirements prepartum (full feeding) or restricted to approximately 85% of prepartum energy requirements (restricted feeding). The second factor was that at approximately 7 d before expected calving date, half the cows in each feed group were injected with pegbovigrastim and the remaining half were injected with saline. Treatments were repeated on the day of calving. Blood samples were collected pre- and postcalving for complete blood count, biochemistry, and in vitro assessment of neutrophil function including phagocytosis, myeloperoxidase release, and oxidative burst. Prepartum energy restriction resulted in lower body weight, a higher proportion of cows with elevated concentrations (i.e., >0.4 mmol/L) of fatty acids, and higher average β-hydroxybutyrate concentrations before calving relative to fully fed cows. Treatment with pegbovigrastim increased the total white cell, neutrophil, lymphocyte, and monocyte counts. Pegbovigrastim treatment resulted in increased release of myeloperoxidase by neutrophils. Prepartum feeding group did not have an effect, and no feeding group × treatment interaction was observed for any of the white cell counts or functional tests. We concluded that pegbovigrastim treatment results in significant increases in neutrophil count and enhances neutrophil function as indicated by increased myeloperoxidase release. The response to pegbovigrastim was not affected by restricted prepartum energy intake.

Invited review: A systematic literature review and meta-analysis of mortality and culling in dairy cattle

Dairy industries and individual farmers are concerned about mortality and culling of dairy animals. This is because the timing and fates of animals that exit dairy farms have important animal welfare and economic consequences that reflect the conditions under which they are farmed and the efficiency of their production systems. Reports from a few countries have indicated increased incidence of mortality, and occasionally culling, of dairy animals in recent decades, and these changes have been associated with intensification of production systems. Dairy industries and farmers need benchmarks for culling and mortality against which they can compare themselves, as well as improved understanding of the extent of any change and of any associated factors. We reasoned that a systematic literature review and meta-analysis of scientific articles published between 1989 and 2014 would allow us to determine whether these reports were universal, to quantify any change over time, and to investigate whether production systems or study factors were associated with culling and mortality. From 3,275 articles retrieved from databases and manual searching of cited articles, 118 articles were appraised independently by 2 assessors, and 51 articles representing 54 studies were determined to be eligible for review and meta-analysis. We estimated that both the annual incidence risk (IR) and incidence density of mortality of cows had increased significantly from 0.02 per cow and 2.32 per 100 cow-years, to 0.04 per cow and 3.75 per 100 cow-years, an increase per decade of 0.02 per cow and 1.42 per 100 cow-years, respectively. We also estimated that the annual IR of culling attributed to low production had declined significantly from 0.07 to 0.05 and that the IR of perinatal, but not neonatal, mortality had increased significantly from 0.04 to 0.06 per decade. We found no evidence of change in overall annual IR of culling of cows over time or any association between study design factors and the IR or incidence density of culling or mortality. These findings provide benchmarks for describing culling and mortality, and should encourage farmers and researchers in countries with modern dairy industries to discover and implement management strategies to reduce the animal welfare and economic costs associated with these changes.

The impact of complications and errors on surgeons

Do surgeons need support – and, if so, what kind?

Accuracy of fetal age estimates using transrectal ultrasonography for predicting calving dates in dairy cows in seasonally calving herds in New Zealand

AIM

To describe the accuracy of transrectal ultrasonography for predicting calving dates in dairy cows under typical New Zealand conditions and to assess potential risk factors for differences between predicted and actual calving dates.

METHODS

Data were collected from 116 seasonally calving herds over 2 years in a retrospective single cohort study. Transrectal ultrasonography was undertaken by experienced veterinarians (n=12) to determine if cows were pregnant, and if so to estimate fetal age. Predicted calving date was calculated by adding 282 days to the estimated conception date. Accuracy was assessed using differences between predicted and actual calving dates for each animal. Potential risk factors for animals calving >10 days before or after their predicted calving date were assessed using multinomial logistic regression models.

RESULTS

The study population comprised 83,104 cows over the 2 years of the study; 75,037 (90.3%) cows calved within 10 days of their predicted calving date, 3,683 (4.4%) calved >10 days earlier, and 4,384 (5.3%) >10 days later, than predicted. Risk factors for calving >10 days before or after the predicted calving date included having >1 artificial insemination (AI) before pregnancy diagnosis (p=0.03), where the cow's most recent AI was <21 days before the end of the herd's AI period (p<0.01), and where the diagnosis was made at the second or third herd-visit (p<0.01). The probability of calving being >10 days later than predicted also increased when the fetus was ≥13 weeks old at pregnancy diagnosis (p<0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

In this study, >90% of cows diagnosed pregnant by veterinarians using transrectal ultrasonography calved within 10 days of the predicted calving date. In herds where herd reproductive performance is high, it would be expected that more cows would conceive to their first AI, and potentially fewer cows would have AI close to the end of the herd's AI period, which would increase diagnostic accuracy. Where herd managers rely on accurate predicted calving dates they should be informed about realistic expected accuracy. For greatest accuracy, a complete AI history should be made available to the person performing the pregnancy diagnoses and cows at most risk of having inaccurate predicted calving dates should be identified.

Pathophysiology of humeral fractures in a sample of dairy heifers

AIMS

To investigate the pathophysiology of humeral fractures in first-lactation dairy heifers in the North Island of New Zealand.

METHODS

Ten 2-year-old dairy heifers with humeral fractures were subject to euthanasia and the fractured and non-fractured contralateral humeri were collected. Humeri were also collected from 10 unaffected 2-year-old dairy heifers sent for slaughter. Humeri from heifers with and without fractures were examined using computed tomography (CT), and four slices of the diaphysis and lower metaphysis (D1-4) were analysed using the Bone J plug-in for Image J. The humeri were sectioned sagittally and 5 mm bone slabs were processed for histopathology.

RESULTS

There were no differences in bone length between the humeri from heifers with or without fractures (p=0.31). Median cortical bone mineral density at D1 was increased in humeri from affected compared with unaffected heifers (810 vs. 783 mg/cm(3); p=0.03), cortical area at D1 was reduced (816 vs. 1,037 mm(2); p=0.04), the median stress strain index, a calculated theoretical measure of bone strength, at D1 was decreased (7,288 vs. 9,072 mm(3); p<0.01), and the median ratio of overall bone volume (BV) to total volume (TV) was decreased (0.32 vs. 0.38; p<0.01). The median periosteal circumference at D1 was also reduced in humeri from affected compared with unaffected heifers (151 vs. 173 mm; p<0.01). Using a binary logistic regression model, BV/TV was the only variable associated with humeral fractures (p=0.03).In nine of 10 fractured humeri the fracture appeared to have started just distal to the head of the humerus and spiralled distally down the diaphysis to end just above the humeral condyles. Histopathological findings included a reduction in the number, and thickness, of trabeculae in the metaphysis; metaphyseal growth arrest lines, and osteoclastic resorption in fractured humeri. Concentrations of copper in serum from four of five animals with fractures were within, and one was below, normal reference ranges, while concentration of copper in the livers of three heifers with fractures were below adequate ranges.

CONCLUSIONS

The CT and histological findings were consistent with a diagnosis of osteoporosis. We propose that humeral fractures in dairy heifers are associated with osteoporosis, possibly as a result of insufficient deposition of bone during growth because of protein-calorie malnutrition. Increased osteoclastic resorption of bone associated with calcium mobilisation for lactation, and periods of copper deficiency may contribute to bone weakening.

Body condition score and plane of nutrition prepartum affect adipose tissue transcriptome regulators of metabolism and inflammation in grazing dairy cows during the transition period

Recent studies demonstrating a higher incidence of metabolic disorders after calving have challenged the management practice of increasing dietary energy density during the last ~3 wk prepartum. Despite our knowledge at the whole-animal level, the tissue-level mechanisms that are altered in response to feeding management prepartum remain unclear. Our hypothesis was that prepartum body condition score (BCS), in combination with feeding management, plays a central role in the peripartum changes associated with energy balance and inflammatory state. Twenty-eight mid-lactation grazing dairy cows of mixed age and breed were randomly allocated to 1 of 4 treatment groups in a 2 × 2 factorial arrangement: 2 prepartum BCS categories (4.0 and 5.0, based on a 10-point scale; BCS4, BCS5) obtained via differential feeding management during late-lactation, and 2 levels of energy intake during the 3 wk preceding calving (75 and 125% of estimated requirements). Subcutaneous adipose tissue was harvested via biopsy at -1, 1, and 4 wk relative to parturition. Quantitative polymerase chain reaction was used to measure mRNA and microRNA (miRNA) expression of targets related to fatty acid metabolism (lipogenesis, lipolysis), adipokine synthesis, and inflammation. Both prepartum BCS and feeding management had a significant effect on mRNA and miRNA expression throughout the peripartum period. Overfed BCS5 cows had the greatest prepartum expression of fatty acid synthase (FASN) and an overall greater expression of leptin (LEP); BCS5 was also associated with greater overall adiponectin (ADIPOQ) and peroxisome proliferator-activated receptor gamma (PPARG), whereas overfeeding upregulated expression of proadipogenic miRNA. Higher postpartum expression of chemokine ligand 5 (CCL5) and the cytokines interleukin 6 (IL6) and tumor necrosis factor (TNF) was detected in overfed BCS5 cows. Feed-restricted BCS4 cows had the highest overall interleukin 1 (IL1B) expression. Prepartum feed restriction resulted in greater chemokine ligand 2 (CCL2) expression. Overall, changes in mRNA expression were consistent with the expression pattern of inflammation-related miRNA. These data shed light on molecular mechanisms underlying the effect of prepartum BCS and feeding management on metabolic and inflammatory status of adipose tissue during the peripartum period. Data support the use of a controlled feed restriction prepartum in optimally conditioned cows, as well as the use of a higher level of dietary energy in under-conditioned cows.

Efficacy of controlled-release capsules containing monensin for the prevention of subclinical ketosis in pasture-fed dairy cows

AIMS

To determine the effectiveness of intra-rumenal controlled release capsules (CRC) containing 32 g of monensin administered pre-calving to reduce the cumulative incidence of subclinical ketosis (SCK) in mainly pasture-fed dairy cows.

METHODS

Cows (n=837) due to calve in the first 6 weeks of the spring calving period were enrolled from four commercial herds in the Waikato region of New Zealand in a blinded, randomised, negative-controlled field trial. Three weeks before the start of the calving period cows were randomly allocated to receive either no treatment (control) or a single CRC containing monensin and then blood sampled on two occasions, 7 days apart within 12 days following calving for measurement of concentrations of beta hydroxybutyrate (BHBA) in blood. Cows were diagnosed with SCK if the concentration of BHBA in blood in either of these samples was ≥1.2 mmol/L.

RESULTS

Fewer treated cows were diagnosed with SCK within 12 days post-calving than control cows (144/340 (42.4%) vs. 192/336 (57.1%); p<0.001). There was no interaction between treatment group and age, breed or herd of origin. From the final multivariable model it was estimated that treatment with CRC containing monensin reduced the absolute cumulative incidence of SCK by 17.9 (95% CI=9.2-25.8)% compared to no treatment.

CONCLUSIONS

Treatment with a CRC containing monensin>10 days prior to calving reduced the cumulative incidence of SCK of pasture-based dairy cows in commercial dairy herds within 12 days post-calving.

CLINICAL RELEVANCE

Administration pre-calving of an intra-rumenal bolus containing monensin can be considered as one of a range of management options for the control of SCK in early lactation.

Detection of bovine herpesvirus type 4 antibodies and bovine lymphotropic herpesvirus in New Zealand dairy cows

AIM

To detect the presence of bovine herpesvirus (BoHV) type 4 in New Zealand dairy cows with clinical metritis.

METHODS

Serum samples taken from 92 dairy cows with clinical metritis, each from a different farm, were tested for the presence of antibodies against BoHV-4 using a commercially available, indirect ELISA. Peripheral blood mononuclear cells (PBMC) were collected from 10 BoHV-4 seropositive cows, and PBMC were examined by a pan-herpesvirus nested PCR to detect herpesvirus. PCR products were sequenced directly and a proportion of the PCR products were cloned and sequenced to identify the virus present.

RESULTS

Antibodies to BoHV-4 were detected in 23/92 (25%) serum samples. The pan-herpesvirus PCR was positive in 8/10 PBMC samples. Cloning and sequencing identified that all of the eight PCR-positive PBMC contained bovine lymphotropic herpesvirus (BLHV); no BoHV-4 DNA was detected.

CONCLUSIONS

This study reports the finding of the presence of apparent antibodies to BoHV-4, and BLHV DNA in New Zealand dairy cows affected by metritis.

CLINICAL RELEVANCE

Bovine herpesvirus type 4 and BLHV are reported to have the potential to cause reproduction failure in cows. This is the first report of apparent BoHV-4 antibodies, and BLHV in New Zealand. The importance and epidemiology of these viruses in cattle in New Zealand requires further investigation.

Small molecule specific run acceptance, specific assay operation, and chromatographic run quality assessment: recommendation for best practices and harmonization from the global bioanalysis consortium harmonization teams

Consensus practices and regulatory guidance for liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) assays of small molecules are more aligned globally than for any of the other bioanalytical techniques addressed by the Global Bioanalysis Consortium. The three Global Bioanalysis Consortium Harmonization Teams provide recommendations and best practices for areas not yet addressed fully by guidances and consensus for small molecule bioanalysis. Recommendations from all three teams are combined in this report for chromatographic run quality, validation, and sample analysis run acceptance.

Invited review: Systematic review of diagnostic tests for reproductive-tract infection and inflammation in dairy cows

The objective of this study was to conduct a systematic and critical appraisal of the quality of previous publications and describe diagnostic methods, diagnostic criteria and definitions, repeatability, and agreement among methods for diagnosis of vaginitis, cervicitis, endometritis, salpingitis, and oophoritis in dairy cows. Publications (n=1,600) that included the words "dairy," "cows," and at least one disease of interest were located with online search engines. In total, 51 papers were selected for comprehensive review by pairs of the authors. Only 61% (n=31) of the 51 reviewed papers provided a definition or citation for the disease or diagnostic methods studied, and only 49% (n=25) of the papers provided the data or a citation to support the test cut point used for diagnosing disease. Furthermore, a large proportion of the papers did not provide sufficient detail to allow critical assessment of the quality of design or reporting. Of 11 described diagnostic methods, only one complete methodology, i.e., vaginoscopy, was assessed for both within- and between-operator repeatability (κ=0.55-0.60 and 0.44, respectively). In the absence of a gold standard, comparisons between different tests have been undertaken. Agreement between the various diagnostic methods is at a low level. These discrepancies may indicate that these diagnostic methods assess different aspects of reproductive health and underline the importance of tying diagnostic criteria to objective measures of reproductive performance. Those studies that used a reproductive outcome to select cut points and tests have the greatest clinical utility. This approach has demonstrated, for example, that presence of (muco)purulent discharge in the vagina and an increased proportion of leukocytes in cytological preparations following uterine lavage or cytobrush sampling are associated with poorer reproductive outcomes. The lack of validated, consistent definitions and outcome variables makes comparisons of the different tests difficult. The quality of design and reporting in future publications could be improved by using checklists as a guideline. Further high-quality research based on published standards to improve study design and reporting should improve cow-side diagnostic tests. Specifically, more data on intra- and interobserver agreement are needed to evaluate test variability. Also, more studies are necessary to determine optimal cut points and time postpartum of examination.

Reproductive performance of seasonal-calving, pasture-based dairy herds in four regions of New Zealand

AIMS

The primary objective of this study was to describe the reproductive performance of a selection of New Zealand dairy herds in 2009/10 and 2010/11. A secondary objective was to explore associations between a number of biophysical and socio-demographic herd-level variables and herd-level reproductive outcomes.

METHODS

Seasonal-calving, pasture-based herds from the Waikato (n=16), Taranaki (n=16), North Canterbury (n=17) and South Canterbury (n=14) regions of New Zealand were enrolled as part of a larger study. Submission, conception and pregnancy risks ("in-calf risks") were calculated for 2009/10 and 2010/11 based on cow-level records and from the results of strategically timed pregnancy diagnoses. Additional herd-level information was collected during interviews with the herd key decision maker (KDM). Associations between independent variables and reproductive performance were examined using univariable and multivariable generalised linear models.

RESULTS

Mean 6-week in-calf risk of the herds over both study years was 67 (min 46, max 86)%, mean 3-week submission risk was 81 (min 44, max 95)% and mean probability of pregnancy at first insemination was 48 (min 25, max 71)%. On univariable analyses, the herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of each of submission risk, probability of pregnancy at first insemination and 6-week in-calf risk (all p<0.01), while other predictor variables considered were non-significant. From multivariable modelling, herds using extensive production systems had better reproductive performance than more intensively managed systems. Higher 3-week submission risks were achieved in herds where the KDM were farm managers rather than owner operators, and where the predominant breed was Jersey rather than Friesian.

CONCLUSIONS

The New Zealand dairy industry has set a target for a mean 6-week in-calf risk of 78%, with minimal hormonal intervention, by 2016. Achieving this target appears unlikely unless there are substantial increases in both submission risks and pregnancy at first inseminations. The mean 6-week in-calf risk of New Zealand dairy herd does not appear to have changed in the last decade. However the large differences between herds indicate that better reproductive performance is currently possible in many herds. The herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of current 6-week in-calf risk, suggesting that rate of improvement in reproductive performance would be slow within current management systems unless substantial changes are introduced.

Antimicrobial resistance in Staphylococcus aureus, Streptococcus uberis and Streptococcus dysgalactiae from dairy cows with mastitis

AIMS

To determine the minimal inhibitory concentrations (MIC) of antimicrobials for common mastitis pathogens from dairy cows in New Zealand; and to assess the effect of source of the isolates, i.e. commercial veterinary laboratories or collected as part of research studies; the clinical status of the cow, i.e. subclinical or clinical mastitis; cow age and herd on the distribution of the MIC.

METHODS

Minimal inhibitory concentrations for Staphylococcus aureus (n=364), Streptococcus dysgalactiae (n=65) and Streptococcus uberis (n=102) isolated from milk samples from dairy cows were determined for a variety of antimicrobials using broth microdilution. Isolates of S. aureus were sourced from research studies from both subclinically (n=161) and clinically (n=104) affected cows, as well as from commercial veterinary laboratories (n=101); while all the streptococcal isolates were from commercial laboratories. Resistance was defined using the cut-points provided by the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

The distribution of MIC varied among the bacterial species for every antimicrobial tested (p<0.001). Of the S. aureus isolates, 28, 2 and 0.5% were resistant to penicillin, ampicillin and trimethoprim/sulfamethoxazole, respectively. For S. dysgalactiae and S. uberis isolates, 17 and 13% were resistant to trimethoprim/sulfamethoxazole, respectively. One isolate (1%) of S. uberis was resistant to penicillin. The distribution of MIC of S. aureus varied with clinical status, between herds, and with age of cow (p<0.05). The distribution of MIC for S. aureus for penicillin, amoxicillin/clavulanic acid, cloxacillin and ampicillin were lower from clinical than subclinical cases, and those for amoxicillin/clavulanic acid and oxytetracycline from isolates from veterinary laboratories were lower than for those from research studies.

CONCLUSIONS

Resistance to some beta-lactam antimicrobials and trimethoprim/sulfamethoxazole were found in isolates from cases of bovine mastitis. The distribution of MIC for isolates of S. aureus varied with clinical status of the cow, the age of the cow, the herd and with the source of isolate.

CLINICAL SIGNIFICANCE

Resistance to penicillin was found in a quarter of S. aureus isolates, but in virtually no Streptococcus isolates; therefore microbial identification and sensitivity testing would be beneficial when assessing treatment options. The source of the isolates affected the estimated MIC, suggesting that selection of isolates for monitoring of resistance requires care and that use of routine submissions to commercial laboratories to assess antimicrobial resistance patterns may result in biased estimates of prevalence of resistance.

Invited review: Mastitis in dairy heifers: nature of the disease, potential impact, prevention, and control

Heifer mastitis is a disease that potentially threatens production and udder health in the first and subsequent lactations. In general, coagulase-negative staphylococci (CNS) are the predominant cause of intramammary infection and subclinical mastitis in heifers around parturition, whereas Staphylococcus aureus and environmental pathogens cause a minority of the cases. Clinical heifer mastitis is typically caused by the major pathogens. The variation in proportions of causative pathogens between studies, herds, and countries is considerable. The magnitude of the effect of heifer mastitis on an individual animal is influenced by the form of mastitis (clinical versus subclinical), the virulence of the causative pathogen(s) (major versus minor pathogens), the time of onset of infection relative to calving, cure or persistence of the infection when milk production has started, and the host's immunity. Intramammary infection in early lactation caused by CNS does not generally have a negative effect on subsequent productivity. At the herd level, the impact will depend on the prevalence and incidence of the disease, the nature of the problem (clinical, subclinical, nonfunctional quarters), the causative pathogens involved (major versus minor pathogens), the ability of the animals to cope with the disease, and the response of the dairy manager to control the disease through management changes. Specific recommendations to prevent and control mastitis in late gestation in periparturient heifers are not part of the current National Mastitis Council mastitis and prevention program. Control and prevention is currently based on avoidance of inter-sucking among young stock, fly control, optimal nutrition, and implementation of hygiene control and comfort measures, especially around calving. More risk factors for subclinical and clinical heifer mastitis have been identified (e.g., season, location of herd, stage of pregnancy) although they do not lend themselves to the development of specific intervention strategies designed to prevent the disease. Pathogen-specific risk factors and associated control measures need to be identified due to the pathogen-related variation in epidemiology and effect on future performance. Prepartum intramammary treatment with antibiotics has been proposed as a simple and effective way of controlling heifer mastitis but positive long-lasting effects on somatic cell count and milk yield do not always occur, ruling out universal recommendation of this practice. Moreover, use of antibiotics in this manner is off-label and results in an increased risk of antibiotic residues in milk. Prepartum treatment can be implemented only as a short-term measure to assist in the control of a significant heifer mastitis problem under supervision of the herd veterinarian. When CNS are the major cause of intramammary infection in heifers, productivity is not affected, making prepartum treatment redundant and even unwanted. In conclusion, heifer mastitis can affect the profitability of dairy farming because of a potential long-term negative effect on udder health and milk production and an associated culling risk, specifically when major pathogens are involved. Prevention and control is not easy but is possible through changes in young stock and heifer management. However, the pathogenesis and epidemiology of the disease remain largely unknown and more pathogen-specific risk factors should be identified to optimize current prevention programs.