Randomized clinical trial evaluating the effects of administering acidogenic boluses at dry-off on udder health, milk yield, and herd removal

Acidogenic boluses can mitigate potential negative effects of high milk yield at dry-off on udder health. This randomized controlled trial aimed to investigate the effect of administering acidogenic boluses at dry-off on dry period IMI dynamics and on milk production parameters, somatic cell count linear score (LSCC), clinical mastitis (CM), and herd removal in the next lactation. A total of 901 cows from 3 dairy farms were randomly allocated to a control (CON, n = 458; no administration of acidogenic boluses at dry-off) or treatment group (TRT, n = 443; administration of 2 acidogenic boluses at dry-off). Quarter milk samples were collected at dry-off and after calving and submitted for bacteriological milk culture. The effects of treatment on the presence of quarter-level postpartum IMI, cure of existing IMI, and acquisition of new IMI, and on the prevalence of cow-level high LSCC (LSCC ≥4) in the first 30 d in milk (DIM) were analyzed using mixed effects logistic regression. Mixed linear regression was used to analyze cow-level milk production parameters (i.e., milk yield, fat corrected milk, fat and protein yield, and LSCC) in the first 90 DIM and until 300 DIM. For CM and herd removal, Cox proportional hazard regression models were used. In addition to treatment group, lactation group at dry-off, presence of high LSCC in the last test-day, average milk yield in the week before dry-off, presence of CM in the lactation of enrollment, and biologically relevant interactions were offered in all models. There was no evidence of a difference in IMI dynamics or in milk, fat corrected milk, protein or fat yields in the subsequent lactation between groups. The TRT group had a lower LSCC in the first 2 mo postpartum compared with the CON group (2.58 ± 0.3 vs. 2.92 ± 0.3 and 2.42 ± 0.3 vs. 2.81 ± 0.3, for first and second month postpartum). The prevalence of high LSCC in the first 30 DIM was 9.1% lower in the TRT compared with the CON group (16.3% vs. 25.5%; risk difference: -9.2; 95% CI: -15.8, -2.5). Cows in the TRT group exhibited reduced hazards of CM in the subsequent lactation compared with cows in the CON group (HR: 0.75; 95% CI: 0.63, 0.89) as well as a reduced hazard of herd removal (HR: 0.82, 95% CI: 0.77, 0.88). The administration of acidogenic boluses as a component of dry-off management is a promising approach to maintain good udder health and reduce the hazard of CM and herd removal during the subsequent lactation.

Invited review: Selective treatment of clinical mastitis in dairy cattle

Treatment of clinical mastitis (CM) and use of antimicrobials for dry cow therapy are responsible for the majority of animal-defined daily doses of antimicrobial use (AMU) on dairy farms. However, advancements made in the last decade have enabled excluding nonsevere CM cases from antimicrobial treatment that have a high probability of cure without antimicrobials (no bacterial causes or gram-negative, excluding Klebsiella spp.) and cases with a low bacteriological cure rate (chronic cases). These advancements include availability of rapid diagnostic tests and improved udder health management practices, which reduced the incidence and infection pressure of contagious CM pathogens. This review informed an evidence-based protocol for selective CM treatment decisions based on a combination of rapid diagnostic test results, review of somatic cell count and CM records, and elucidated consequences in terms of udder health, AMU, and farm economics. Relatively fast identification of the causative agent is the most important factor in selective CM treatment protocols. Many reported studies did not indicate detrimental udder health consequences (e.g., reduced clinical or bacteriological cures, increased somatic cell count, increased culling rate, or increased recurrence of CM later in lactation) after initiating selective CM treatment protocols using on-farm testing. The magnitude of AMU reduction following a selective CM treatment protocol implementation depended on the causal pathogen distribution and protocol characteristics. Uptake of selective treatment of nonsevere CM cases differs across regions and is dependent on management systems and adoption of udder health programs. No economic losses or animal welfare issues are expected when adopting a selective versus blanket CM treatment protocol. Therefore, selective CM treatment of nonsevere cases can be a practical tool to aid AMU reduction on dairy farms.

Effect of Holstein genotype on ex-vivo interleukin-1β response to lipopolysaccharide (LPS), lipoteichoic acid (LTA) and heat-killed Gram-negative and Gram-positive bacteria

Effects of Holstein genotype on interleukin-1β response were assessed by ex-vivo stimulation of whole blood with lipopolysaccharide (LPS), lipoteichoic acid (LTA), or sonicated, heat-killed Gram-negative or Gram-positive bacteria. Holstein genotypes were unselected Holsteins (UH, n = 14) not subjected to selection pressures since the mid-1960s and contemporary Holsteins (CH, n = 13). Milk yield of UH and CH cows differ by more than 4500 kg/lactation. Whole blood was mixed with 0.01 µg LPS, 10 µg LTA or 2.5 × 10⁶ CFU of sonicated, heat-killed E. coli, K. pneumoniae, S. marcescens, S. aureus, S. dysgalactiae, or S. uberis per mL of blood and incubated (4 h, 37 °C). Plasma IL-1β was quantified by ELISA and log₁₀-transformed concentrations analyzed with a multivariate linear mixed effects model. Responses to bacteria were greater than responses to LPS or LTA. Responses to LPS, LTA and the Gram-negative stimulants were greater in UH than in CH cows while responses to the Gram-positive bacteria did not differ between Holstein genotypes. In both genotypes, strong correlations were detected among IL-1β responses to the Gram-negative stimulants and to LTA. There were strong correlations among IL-1β responses to the Gram-positive bacteria in CH cows but only between S. aureus and S. dysgalactiae in UH cows. The IL-1β response to S. uberis was highly correlated with responses to all of the Gram-negative stimulants in CH cows but only with E. coli in the UH cows. The reduced immune response could make contemporary cows more susceptible to infection by Gram-negative bacteria. Results confirm selection practices since the mid-1960s have altered immune response in the Holstein, at least to Gram-negative bacteria, and validate the need for additional studies to further evaluate the impacts of these selection practices on immune function in contemporary Holsteins.

Selective treatment of nonsevere clinical mastitis does not adversely affect cure, somatic cell count, milk yield, recurrence, or culling: A systematic review and meta-analysis

Treatment of clinical mastitis (CM) contributes to antimicrobial use on dairy farms. Selective treatment of CM based on bacterial diagnosis can reduce antimicrobial use, as not all cases of CM will benefit from antimicrobial treatment, e.g., mild and moderate gram-negative infections. However, impacts of selective CM treatment on udder health and culling are not fully understood. A systematic search identified 13 studies that compared selective versus blanket CM treatment protocols. Reported outcomes were synthesized with random-effects models and presented as risk ratios or mean differences. Selective CM treatment protocol was not inferior to blanket CM treatment protocol for the outcome bacteriological cure. Noninferiority margins could not be established for the outcomes clinical cure, new intramammary infection, somatic cell count, milk yield, recurrence, or culling. However, no differences were detected between selective and blanket CM treatment protocols using traditional analyses, apart from a not clinically relevant increase in interval from treatment to clinical cure (0.4 d) in the selective group and higher proportion of clinical cure at 14 d in the selective group. The latter occurred in studies co-administering nonsteroidal anti-inflammatories only in the selective group. Bias could not be ruled out in most studies due to suboptimal randomization, although this would likely only affect subjective outcomes such as clinical cure. Hence, findings were supported by a high or moderate certainty of evidence for all outcome measures except clinical cure. In conclusion, this review supported the assertion that a selective CM treatment protocol can be adopted without adversely influencing bacteriological and clinical cure, somatic cell count, milk yield, and incidence of recurrence or culling.

Improving farm-level antimicrobial stewardship benchmarks by reporting antimicrobial use within the context of both the magnitude of disease pressure and the outcome of therapy

This manuscript explores a method of benchmarking antimicrobial use within the context of farm level therapeutic incidence (a proxy for disease incidence), and the outcome of that therapy. This is reported both within the same farm over time (2016–2019), as well as evaluated across participating farms. Reporting antimicrobial use in this format addresses multiple primary questions necessary for evaluating on farm antimicrobial stewardship: How much disease is recorded? How much antimicrobial use is recorded? How often are antimicrobials included in therapy for each disease? What is the outcome of therapy? The three primary metrics reported are: therapeutic events per 100 cow years (TE/100CY), antimicrobial regimens per 100 cow years (REG/100CY), and the percent therapeutic success (% Success). Success was defined as: the cow remained in the herd and had no further TE recorded within 30 days of the end of the TE being evaluated. These measures identify opportunities for change on an individual farm, such as improvement in disease prevention, or a change in choices about when to include an antimicrobial in the treatment protocol. Therapeutic outcomes provide additional context, in some instances demonstrating differences in recording practices and case definitions, while in other cases serving to safeguard animal welfare as efforts are made to decrease antimicrobial use in the future. Although developed for farm level reporting, the metrics may also be more broadly summarized to meet future reporting requirements for marketing chain or national level antimicrobial use reports. The process outlined here serves as a prototype to be considered when developing antimicrobial use reporting systems where farm level antimicrobial stewardship is the primary objective.

Effect of Holstein genotype on ex-vivo cytokine response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) during the periparturient period

Effects of Holstein genotype on innate immune response were assessed with ex-vivo lipopolysaccharide (LPS) and lipoteichoic acid (LTA) stimulation of whole blood from unselected (UH, n = 10) and contemporary (CH, n = 11) Holsteins that differ in production by more than 4,500 kg/lactation. Blood was collected at -14, 7, 28, and 49 days in milk (DIM), mixed with a pathogen-associated molecular pattern (PAMP) molecule (0.01 or 1.0 µg LPS or 10 or 100 µg LTA per mL blood) and incubated (4 h, 37 °C). Plasma cytokines were quantified by ELISA, log₁₀-transformed and analyzed by repeated measures with DIM as the repeated effect. Cytokine responses increased with PAMP dose and decreased as DIM increased. There was a genotype by LPS dose interaction for IL-1β as response to the low dose was greater in UH but did not differ between genotypes for the high dose. The IL-1β response was greater while the IL-6 response to LTA tended to be greater in UH than in CH cows. The more negative energy balance of CH cows did not impact genotype difference in cytokine responses. Results indicate selection since the mid-1960s has decreased ex-vivo, whole blood cytokine response of CH cows to LPS and to LTA.

The microbiome of common bedding materials before and after use on commercial dairy farms

Background

Bovine mastitis is one of the most economically important diseases affecting dairy cows. The choice of bedding material has been identified as an important risk factor contributing to the development of mastitis. However, few reports examine both the culturable and nonculturable microbial composition of commonly used bedding materials, i.e., the microbiome. Given the prevalence of nonculturable microbes in most environments, this information could be an important step to understanding whether and how the bedding microbiome acts as a risk factor for mastitis. Therefore, our objective was to characterize the microbiome composition and diversity of bedding material microbiomes, before and after use.

Methods

We collected 88 bedding samples from 44 dairy farms in the U.S. Unused (from storage pile) and used (out of stalls) bedding materials were collected from four bedding types: new sand (NSA), recycled manure solids (RMS), organic non-manure (ON) and recycled sand (RSA). Samples were analyzed using 16S rRNA sequencing of the V3–V4 region.

Results

The overall composition as well as the counts of several microbial taxa differed between bedding types, with Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes dominating across all types. Used bedding contained a significantly different microbial composition than unused bedding, but the magnitude of this difference varied by bedding type, with RMS bedding exhibiting the smallest difference. In addition, positive correlations were observed between 16S rRNA sequence counts of potential mastitis pathogens (bacterial genera) and corresponding bedding bacterial culture data.

Conclusion

Our results strengthen the role of bedding as a potential source of mastitis pathogens. The consistent shift in the microbiome of all bedding types that occurred during use by dairy cows deserves further investigation to understand whether this shift promotes pathogen colonization and/or persistence, or whether it can differentially impact udder health outcomes. Future studies of bedding and udder health may be strengthened by including a microbiome component to the study design.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-022-00171-2.

Evaluation of 4 predictive algorithms for intramammary infection status in late-lactation cows

The objective of this observational study was to compare 4 cow-level algorithms to predict cow-level intramammary infection (IMI) status (culture and MALDI-TOF) in late-lactation US dairy cows using standard measures of test performance. Secondary objectives were to estimate the likely effect of each algorithm, if used to guide selective dry cow therapy (SDCT), on dry cow antibiotic use in US dairy herds, and to investigate the importance of including clinical mastitis criteria in algorithm-guided SDCT. Cows (n = 1,594) from 56 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each farm visit, aseptic quarter-milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status, which was considered the reference test in this study. Clinical mastitis records and Dairy Herd Improvement Association test-day somatic cell count data were extracted from herd records and used to perform cow-level risk assessments (low vs. high risk) using 4 algorithms that have been proposed for SDCT in New Zealand, the Netherlands, United Kingdom, and the United States. Agreement between aerobic culture (reference test; IMI vs. no-IMI) and algorithm status (high vs. low risk) was described using Cohen's kappa, test sensitivity, specificity, negative predictive value, and positive predictive value. The proportion of cows classified as high risk among the 4 algorithms ranged from 0.31 to 0.63, indicating that these approaches to SDCT could reduce antibiotic use at dry-off by 37 to 69% in the average US herd. All algorithms had poor agreement with IMI status, with kappa values ranging from 0.05 to 0.13. Sensitivity varied by pathogen, with higher values observed when detecting IMI caused by Streptococcus uberis, Streptococcus dysgalactiae, Staphylococcus aureus, and Lactococcus lactis. Negative predictive values were high for major pathogens among all algorithms (≥0.87), which may explain why algorithm-guided SDCT programs have been successfully implemented in field trials, despite poor agreement with overall IMI status. Removal of clinical mastitis criteria for each algorithm had little effect on the algorithm classification of cows, indicating that algorithms based on SCC alone may have similar performance to those based on SCC and clinical mastitis criteria. We recommend that producers implementing algorithm-guided SDCT use algorithm criteria that matches their relative aspirations for reducing antibiotic use (high specificity, positive predictive value) or minimizing untreated IMI at dry-off (high sensitivity, negative predictive value).

Prevalence, antibiotic resistance, virulence and genetic diversity of Staphylococcus aureus isolated from bulk tank milk samples of U.S. dairy herds

Background

Colonization of dairy cows by Staphylococcus aureus (S. aureus), especially those which are multi-drug resistant and toxin producing, is a concern for animal health and well-being as well as public health. The objective of this study was to investigate the prevalence, antibiotic resistance, gene content and virulence determinants of S. aureus in bulk tank milk samples (BTM) from U.S. dairy herds.

Results

BTM samples were collected, once in winter and once in summer, from 189 U.S. dairy herds. Of 365 BTM samples cultured, the sample and herd prevalence of S. aureus in BTM was 46.6% (170 of 365 samples) and 62.4% (118 of 189 herds), respectively. Among a subset of 138 S. aureus isolates that were stored for further analysis, 124 were genome sequenced after being confirmed as S. aureus using phenotypic tests. The most commonly identified antimicrobial resistance-associated gene was norA (99.2%) and mecA gene responsible for methicillin resistance (MRSA) was identified in one isolate (0.8%). The most frequently detected putative virulence genes were aur (100%), hlgB (100%), hlgA, hlgC, hlb (99.2%), lukE (95.9%) and lukD (94.3%). In the 53 staphylococcal enterotoxin positive isolates, sen (37.9%), sem (35.5%), sei (35.5%) and seg (33.1%) were the most frequently detected enterotoxin genes. Among the 14 sequence types (ST) and 18 spa types identified, the most common was ST2187 (20.9%) and t529 (28.2%), respectively. The most predominant clone was CC97 (47.6%) followed by CC unknown (36.3%). The single MRSA isolate belonged to ST72-CC8, spa type t126 and was negative for the tst gene but harbored all the other virulence genes investigated.

Conclusion

Our findings indicated a high prevalence of S. aureus in BTM of U.S. dairy herds, with isolates showing little evidence of resistance to antibiotics commonly used to treat mastitis. However, isolates often carried genes for the various enterotoxins. This study identified predominant genetic clones. Despite lower prevalence, the presence of MRSA and multi-drug resistant strains in BTM poses a significant risk to animal and public health if their number were to increase in dairy environment. Therefore, it is necessary to continuously monitor the use of antibiotics in dairy cows.

Antimicrobial use quantification in adult dairy cows - Part 3 - Use measured by standardized regimens and grams on 29 dairies in the United States

This study describes antimicrobial use in terms of standardized regimens per cow year (REG/CY) and grams per cow year (GMS/CY) for 29 dairies in the United States during the years 2016 and 2017. To explore potential priorities for antimicrobial stewardship programs, these measures were stratified by both disease syndrome and antimicrobial class. Potential confounders of use measurements are discussed and challenges for measure interpretation are identified. When measured as REG/CY, the results indicate that mastitis is the disease syndrome with the greatest contribution to overall antimicrobial use. However, when GMS/CY is measured, metritis, lameness and unknown disease syndromes are also significant contributors. When use is stratified by antimicrobial class, measures of REG/CY indicate the greatest magnitude of use is the cephalosporin class. However, when measures of GMS/CY are stratified by drug class, use within the penicillin class contributes more than any other single class. These differences highlight the need for a more complete understanding of the relationship between antimicrobial use measures and their relationship to antimicrobial resistance selection pressure.

Antimicrobial use quantification in adult dairy cows - Part 2 - Developing a foundation for pharmacoepidemiology by comparing measurement methods

As stewardship programmes seek to influence therapeutic choices and reduce resistance selection pressure, it is essential to understand the multiple factors which may influence any given antimicrobial use measure. This article compares 9 measures of antimicrobial use pertaining to adult cows in US dairy systems based on treatment records standardized to a single standardized regimen (SReg) format. There are 3 fundamental parameters underlying the nine measures: amount of active substance (AMOUNT), number of SRegs (ANIMALS) and treatment time (TIME). Additionally, three use categories were considered in the analysis: control of mastitis (Dry Cow), treatment of detected mastitis (Clinical Mastitis) and treatment of other diseases (Other Treatment). The assumptions necessary for calculation of each of the nine measures are identified. The influence of measure choice on farm rank was explored at the farm level both within and across fundamental parameters. Across all use categories, when measures of TIME and ANIMALS were compared, correlations between measures were greater than 0.91. However, when measures of AMOUNT were compared to either measures of TIME or ANIMALS, the correlation between measures was more variable across use categories (R = 0.31-0.91). These comparisons demonstrate that the selection of antimicrobial use metric can affect which dairies are considered the highest users of antimicrobials. Measurement selection also influences which use category has the greatest potential for use reduction. This indicates that measure selection can influence which use category is prioritized as a target for reduction of antimicrobial use. Utilization of this information may allow those developing dairy antimicrobial stewardship programmes to better understand the potential effects of measurement selection on driving changes in antimicrobial use.

Antimicrobial use quantification in adult dairy cows - Part 1 - Standardized regimens as a method for describing antimicrobial use

This study describes a process to acquire and convert farm treatment records into a standardized regimen format. Multiple sources of on-farm data were utilized to convert the original treatment records to standardized regimens, enabling the generation of objective, granular descriptions of antimicrobial use. These standard regimen descriptions allow antimicrobial use data to be qualitatively stratified by active substance, disease syndrome treated, use category, and route of administration. Quantitative distributions are available for the grams of active substance per administration, the grams of active substance per regimen, the number of administrations, number of days of therapy and the time frame between the first and last administration. Granular quantification by this method informs future research, surveillance and policy.

Partial budget analysis of culture- and algorithm-guided selective dry cow therapy

The objectives of this study were to (1) use partial budget analysis to estimate the cash impact for herds that switch from blanket dry cow therapy (BDCT) to culture- or algorithm-guided selective dry cow therapy (SDCT) and (2) conduct a sensitivity analysis to investigate effects in situations where SDCT increased clinical and subclinical mastitis risk during the subsequent lactation. A partial budget model was created using Monte Carlo simulation with @Risk software. Expenditures associated with dry-off procedures and health outcomes (clinical and subclinical mastitis) during the first 30 d in milk were used to model herd-level effects, expressed in units of US dollars per cow dry-off. Values for each economic component were derived from findings from a recent multisite clinical trial, peer-reviewed journal articles, USDA databases, and our experiences in facilitating the implementation of SDCT on farms. Fixed values were used for variables expected to have minimal variation within the US dairy herd population (e.g., cost of rapid culture plates) and sampling distributions were used for variables that were hypothesized to vary enough to effect the herd net cash impact of one or more DCT approach(es). For Objective 1, herd-level udder health was assumed to be unaffected by the implementation of SDCT. For culture-guided SDCT, producers could expect to save an average of +$2.14 (-$2.31 to $7.23 for 5th and 95th percentiles) per cow dry-off as compared with BDCT, with 75.5% of iterations being ≥$0.00. For algorithm-guided SDCT, the mean net cash impact was +$7.85 ($3.39-12.90) per cow dry-off, with 100% of iterations being ≥$0.00. The major contributors to variance in cash impact for both SDCT approaches were percent of quarters treated at dry-off and the cost of dry cow antibiotics. For Objective 2, we repeated the partial budget model with the 30-d clinical and subclinical mastitis incidence increasing by 1, 2, and 5% (i.e., risk difference = 0.01, 0.02, and 0.05) in both SDCT groups compared with BDCT. For algorithm-guided SDCT, average net cash impacts were ≥$0.00 per cow dry-off (i.e., cost effective) when mastitis incidence increased slightly. However, as clinical mastitis incidence increased, economic returns for SDCT diminished. These findings indicate that when SDCT is implemented appropriately (i.e., no to little negative effect on health), it might be a cost-effective practice for US herds under a range of economic conditions.

Postcalving udder health and productivity in cows approaching dry-off with intramammary infections caused by non-aureus Staphylococcus, Aerococcus, Enterococcus, Lactococcus, and Streptococcus species

The objective of this prospective cohort study was to explore associations between intramammary infection (IMI) in late-lactation cows and postcalving udder health and productivity. Cows (n = 2,763) from 74 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each visit, aseptic quarter milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status at enrollment. Cows were followed from enrollment until 120 d in milk (DIM) in the subsequent lactation. Herd records were used to establish whether subjects experienced clinical mastitis or removal from the herd, and DHIA test-day data were used to record subclinical mastitis events (somatic cell count >200,000 cells/mL) and milk yield (kg/d) during the follow-up period. Cox regression and generalized estimating equations were used to evaluate the associations between IMI and the outcome of interest. The presence of late-lactation IMI caused by major pathogens was positively associated with postcalving clinical mastitis [hazard ratio = 1.5, 95% confidence interval (CI): 1.2, 2.0] and subclinical mastitis (risk ratio = 1.5, 95% CI: 1.3, 1.9). Species within the non-aureus Staphylococcus (NAS) group varied in their associations with postcalving udder health, with some species being associated with increases in clinical and subclinical mastitis in the subsequent lactation. Late-lactation IMI caused by Streptococcus and Streptococcus (Strep)-like organisms, other than Aerococcus spp. (i.e., Enterococcus, Lactococcus, and Streptococcus spp.) were associated with increases in postcalving clinical and subclinical mastitis. Test-day milk yield from 1 to 120 DIM was lower (-0.9 kg, 95% CI: -1.6, -0.3) in late-lactation cows with any IMI compared with cows without IMI. No associations were detected between IMI in late lactation and risk for postcalving removal from the herd within the first 120 DIM. Effect estimates reported in this study may be less than the underlying quarter-level effect size for IMI at dry-off and postcalving clinical and subclinical mastitis, because of the use of late-lactation IMI as a proxy for IMI at dry-off and the use of cow-level exposure and outcome measurements. Furthermore, the large number of models run in this study (n = 94) increases the chance of identifying chance associations. Therefore, confirmatory studies should be conducted. We conclude that IMI in late lactation may increase risk of clinical and subclinical mastitis in the subsequent lactation. The relationship between IMI and postcalving health and productivity is likely to vary among pathogens, with Staphylococcus aureus, Streptococcus spp., Enterococcus spp., and Lactococcus spp. being the most important pathogens identified in the current study.

Evaluation of the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) system in the detection of mastitis pathogens from bovine milk samples

MALDI-TOF is a chemistry analytical tool that has recently been deployed in the identification of microorganisms isolated from nosocomial environments. Its use in diagnostics has been extremely advantageous in terms of cost effectiveness, sample preparation easiness, turn-around time and result analysis accessibility. In the dairy industry, where mastitis causes great financial losses, a rapid diagnostic method such as MALDI-TOF could assist in the control and prevention program of mastitis, in addition to the sanitation and safety level of the dairy farms and processing facility. However, the diagnostic strengths and limitations of this test method require further understanding. In the present study, we prospectively compared MALDI-TOF MS to conventional 16S rDNA sequencing method for the identification of pathogens recovered from milk associated with clinical and subclinical bovine mastitis cases. Initially, 810 bacterial isolates were collected from raw milk samples over a period of three months. However, only the isolates (481) having both 16S rDNA sequencing and MALDI-TOF identification were included in the final phase of the study. Among the 481 milk isolates, a total of 26 genera (12 g-postive and 14 g-negative), including 71 different species, were taxonomically charecterized by 16S rDNA at the species level. Comparatively, MALDI-TOF identified 17 genera (9 g-positive and 8 g-negative) and 33 differernt species. Overall, 445 (93%) were putatively identified to the genus level by MALDI-TOF MS and 355 (74%) were identified to the species level, but no reliable identification was obtained for 16 (3.3%), and 20 (4.2%) discordant results were identified. Future studies may help to overcome the limitations of the MALDI database and additional sample preparation steps might help to reduce the number of discordances in identification. In conclusion, our results show that MALDI-TOF MS is a fast and reliable technique which has the potential to replace conventional identification methods for common mastitis pathogens, routinely isolated from raw milk. Thus it's adoption will strengthen the capacity, quality, and possibly the scope of diagnostic services to support the dairy industry.

The effect of individual versus pair housing of dairy heifer calves during the preweaning period on measures of health, performance, and behavior up to 16 weeks of age

Pair housing of dairy heifer calves during the preweaning period helps meet the natural social needs of the calf and has been shown to improve growth and starter intake during the preweaning period as compared with individual housing. However, there is little evidence to suggest that pair-housed calves maintain their social and growth advantages past the weaning phase. The objective of this study was to investigate the effect of pair housing on measures of calf performance, health, and behavior up to 16 wk of age. Healthy Holstein and crossbred heifer calves were enrolled in the study after colostrum feeding, with the first calf randomly assigned to 1 of 2 housing treatments: pair (PR; 2 hutches with common outdoor space) or individual (INDV; 1 hutch plus outdoor space). All calves were bucket fed 4 L of milk replacer twice daily and weaned at 50 d of age. Weaned calves (6/group) remained with their treatment group until exit from the study at 16 wk. A venous blood sample was collected from each calf between 24 h and 7 d of age to test for serum total protein (g/dL). Body weights (kg) were obtained at birth, weaning, and 16 wk. Each enrolled calf was scored for health each week and calf health treatments were also collected. A hair sample was collected from the left shoulder at birth and 16 wk to assess hair cortisol (pg/mL). At enrollment, each calf was fitted with a triaxial accelerometer on the left hind leg for continuous recording of standing and lying time (min/24 h) for 16 wk. Latency to find feed, water, and lie down (min) at entrance to the weaned pen were recorded by continuous video observation. Open field testing with a novel object was performed at 5, 10, and 16 wk. Behaviors analyzed by video observation included latency to approach the object (s), vocalizations (n), and time spent immobile, walking, or running (s/10 min). Linear mixed models were used to determine the effect of treatment (INDV or PR) on calf growth, activity, and behavioral outcomes, which accounted for time, breed, the interaction of time and treatment, the random pen, and variability in testing day and repeated measurements within calf when appropriate. Twenty-four Holstein and crossbred calves (PR: n = 12, 6 pairs; INDV: n = 12) were enrolled from November 2 to December 23, 2018. The PR calves were 7.1 kg heavier at weaning and gained 0.15 kg/d more during the preweaning period as compared with INDV calves. In the 24 h after movement to the postweaning pen, PR calves lay down for longer periods of time (14.3 vs. 11.0 ± 0.4 h/d), and PR calves urinated more during novel object testing at 5 wk of age. Our study demonstrated benefits, such as better growth and increased lying time, of pair housing calves during the preweaning period.

Randomized equivalence study comparing the efficacy of 2 commercial internal teat sealants in dairy cows

The use of an internal teat sealant (ITS) at dry-off has been repeatedly shown to improve udder health in the subsequent lactation. However, almost all ITS research conducted in North America has evaluated one product (Orbeseal, Zoetis, Parsippany, NJ). The objective of this study was to evaluate a new ITS product (Lockout, Boehringer-Ingelheim Animal Health, Duluth, GA), by comparing it directly to Orbeseal in a multi-site, randomized, positively controlled equivalence trial for health indicators during the dry period [quarter-level new intramammary infection (IMI) risk, IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM] and during the first 100 DIM [clinical mastitis and culling or death risk and test-day milk somatic cell count (SCC) and milk yield]. At dry-off, cows were randomly allocated to be treated with Orbeseal or Lockout after blanket administration of a cloxacillin dry cow therapy product. Cows were then followed from dry-off until 100 DIM. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods, allowing for the measurement of IMI dynamics during the dry period (i.e., IMI cures and new IMI). The effect of ITS group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic). Marginal standardization was used to derive risk difference estimates. An equivalence hypothesis test was conducted to compare ITS groups for dry period new IMI risk (margin of equivalence was ±5% units). The effect of ITS group on clinical mastitis and culling or death was determined using Cox proportional hazards regression. The effect of ITS group on test-day SCC and milk yield was determined using linear mixed models. Final models indicated that measures of quarter-level IMI dynamics were similar between ITS groups (i.e., risk difference estimates and 95% confidence intervals all close to zero). Furthermore, Lockout was found to be equivalent to Orbeseal for dry period new IMI risk using an equivalence hypothesis test. Hazard ratio estimates for clinical mastitis and culling or death were close to 1 and differences in SCC and milk yield between ITS groups were close to 0, indicating negligible effects of ITS group on test-day SCC and milk yield. In most cases, these effect estimates were relatively precise (i.e., narrow 95% confidence intervals). We conclude that producers using blanket dry cow therapy could consider including Orbeseal or Lockout treatment in their programs.

Randomized controlled non-inferiority trial investigating the effect of 2 selective dry-cow therapy protocols on antibiotic use at dry-off and dry period intramammary infection dynamics

Selective dry-cow therapy (SDCT) could be used to reduce antibiotic use on commercial dairy farms in the United States but is not yet widely adopted, possibly due to concerns about the potential for negative effects on cow health. The objective of this study was to compare culture- and algorithm-guided SDCT programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure, non-inferiority trial for the following quarter-level outcomes: antibiotic use at dry-off, dry period intramammary infection (IMI) cure risk, dry period new IMI risk, and IMI risk at 1 to 13 d in milk (DIM). Two days before planned dry-off, cows in each of 7 herds were randomly allocated to BDCT, culture-guided SDCT (cult-SDCT), or algorithm-guided SDCT (alg-SDCT). At dry-off, BDCT cows received an intramammary antibiotic (500 mg of ceftiofur hydrochloride) in all 4 quarters. Antibiotic treatments were selectively allocated to quarters of cult-SDCT cows by treating only quarters from which aseptically collected milk samples tested positive on the Minnesota Easy 4Cast plate (University of Minnesota, St. Paul, MN) after 30 to 40 h of incubation. For alg-SDCT cows, antibiotic treatments were selectively allocated at the cow level, with all quarters receiving antibiotic treatment if the cow had either a Dairy Herd Improvement Association test somatic cell count >200,000 cells/mL during the current lactation or 2 or more clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods. The effect of treatment group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic), with marginal standardization to derive risk difference (RD) estimates. Quarter-level antibiotic use at dry-off for each group was BDCT (100%), cult-SDCT (45%), and alg-SDCT (45%). The crude dry period IMI cure risk for all quarters was 87.5% (818/935), the crude dry period new IMI risk was 20.1% (764/3,794), and the prevalence of IMI at 1 to 13 DIM was 23% (961/4,173). Non-inferiority analysis indicated that culture- and algorithm-guided SDCT approaches performed at least as well as BDCT for dry period IMI cure risk. In addition, the final models indicated that the risks for each of the 3 IMI measures were similar between all 3 treatment groups (i.e., RD estimates and 95% confidence intervals all close to 0). These findings indicate that under the conditions of this trial, culture- and algorithm-guided SDCT can substantially reduce antibiotic use at dry-off without negatively affecting IMI dynamics.

Randomized controlled trial investigating the effect of 2 selective dry-cow therapy protocols on udder health and performance in the subsequent lactation

The objective of this study was to compare culture- and algorithm-guided selective dry-cow therapy (SDCT) programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure clinical trial for the following cow-level outcomes: clinical mastitis, removal from the herd, and Dairy Herd Improvement Association (DHIA) test-day milk yield and SCC measures during the first 120 d in milk (DIM). Two days before planned dry-off, cows in each of 7 herds were randomly allocated to BDCT, culture-guided SDCT (cult-SDCT), or algorithm-guided SDCT (alg-SDCT). At dry-off, BDCT cows received an intramammary antibiotic (500 mg of ceftiofur hydrochloride) in all 4 quarters. Antibiotic treatments were selectively allocated to quarters of cult-SDCT cows by only treating quarters from which aseptically collected milk samples tested positive on a rapid culture system after 30 to 40 h of incubation. For alg-SDCT cows, antibiotic treatments were selectively allocated at the cow level, with all quarters receiving antibiotic treatment if the cow met at least one of the following criteria: (1) any DHIA test with a somatic cell count >200,000 cells/mL during the current lactation, and (2) ≥2 clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Clinical mastitis and removal from the herd events (i.e., culling or death) and DHIA test-day data from dry-off to 120 DIM were extracted from herd records. Hazard ratios (HR) for the effect of treatment group on clinical mastitis and removal from the herd during 1 to 120 DIM were determined using Cox proportional hazards regression. The effects of treatment group on test-day log_e-transformed SCC and milk yield were determined using linear mixed models. Final models indicated that either SDCT program was unlikely to increase clinical mastitis risk (HR_{cult-SDCT/BDCT} = 0.82, 95% CI: 0.58, 1.15; HR_{alg-SDCT/BDCT} = 0.83, 95% CI: 0.63, 1.09) or test-day log_eSCC (cult-SDCT minus BDCT = 0.05, 95% CI: -0.09, 0.18; alg-SDCT minus BDCT = 0.07, 95% CI: -0.07, 0.21). Risk of removal from the herd and test-day milk yield were similar between treatment groups. Findings from this study indicate that culture- or algorithm-guided SDCT can be used at dry-off without negatively affecting cow health and performance in early lactation.

Colostrum Management for Dairy Calves

Colostrum management is the single most important management factor in determining calf health and survival. Additional benefits of good colostrum management include improved rate of gain and future productivity. Successful colostrum management requires producers to provide calves with a sufficient volume of clean, high-quality colostrum within the first few hours of life. This article reviews the process of colostrogenesis and colostrum composition, and discusses key components in developing a successful colostrum management program. In addition, the article discusses approaches for monitoring and proposes new goals for passive immunity in dairy herds.

Cross-sectional study of the relationship between cloth udder towel management, towel bacteria counts, and intramammary infection in late-lactation dairy cows

Because cloth udder towels (CUT) may function as a fomite for mastitis-causing pathogens, most udder health laboratories offer towel culture services as a tool to monitor towel hygiene. However, no studies have investigated if an association exists between bacteria levels in CUT and udder health outcomes. The objectives of this cross-sectional study were to (1) describe associations between herd-level measures of towel bacteria count (ToBC) and quarter-level intramammary infection (IMI) status in late-lactation cows, (2) establish pathogen-specific target levels of bacteria in CUT to aid the interpretation of towel culture reports, and (3) identify laundering-related risk factors for high ToBC. The study was conducted in 67 herds from 10 dairy states in the United States that used CUT. These 67 herds were originally recruited as part of a larger (80 herd) cross-sectional study of bedding management. Each herd was visited once during December 2017 to April 2018 and quarter-milk samples (n = 4,656) were collected from late-gestation (>180 d pregnant) cows (n = 1,313). Two recently laundered CUT were collected and a questionnaire was used to collect information about pre-milking teat preparation and CUT management practices. Quarter-level IMI status was determined using standard bacteriologic methods. In addition, colony-forming units of all bacteria (total bacteria), Staphylococcus spp., Streptococcus spp. or Streptococcus-like organisms (SSLO), coliforms, noncoliform gram-negatives, and Bacillus spp. were determined for each pair of CUT (log₁₀ cfu/cm²). The association between ToBC and IMI was determined using multivariable logistic regression with mixed effects. After dichotomizing ToBC into high and low categories, associations between towel management practices and ToBC category were determined using unconditional logistic regression. The quarter-level prevalence of IMI was 19.6%, which was predominantly caused by non-aureus Staphylococcus spp. (NAS; 10.2%) and SSLO (5.1%). The predominant bacteria in CUT were Bacillus spp. (median = 3.13 log₁₀ cfu/cm²). Total bacteria count was not associated with odds of IMI (odds ratio = 1.06), likely due to the predominance of Bacillus spp. in CUT and low number of IMI caused by Bacillus spp. In contrast, counts of Staphylococcus spp. and SSLO were positively associated with odds of IMI caused by NAS (odds ratio = 1.33) and SSLO (odds ratio = 1.45), respectively. Of 12 CUT management practices evaluated, only the failure to use a dryer was identified as a clear predictor of risk for a high ToBC (risk ratio of high coliform count = 8.17). Our study findings suggest that CUT may act as a fomite for NAS and SSLO. We recommend that herds aim to keep counts of Staphylococcus spp. and SSLO in CUT below 32 cfu/cm² (or 5 cfu/in²), and that laundered towels be completely dried in a hot air dryer.

Cross-sectional study of the relationships among bedding materials, bedding bacteria counts, and intramammary infection in late-lactation dairy cows

Objectives of this study were to (1) describe the intramammary infection (IMI) prevalence and pathogen profiles in quarters of cows approaching dry-off in US dairy herds, (2) compare IMI prevalence in quarters of cows exposed to different bedding material types, and (3) identify associations between bedding bacteria count and IMI in cows approaching dry-off. Eighty herds using 1 of 4 common bedding materials (manure solids, organic non-manure, new sand, and recycled sand) were recruited in a multi-site cross-sectional study. Each herd was visited twice for sampling. At each visit, aseptic quarter-milk samples were collected from 20 cows approaching dry-off (>180 d pregnant). Samples of unused and used bedding were also collected. Aerobic culture was used to determine the IMI status of 10,448 quarters and to enumerate counts (log₁₀ cfu/mL) of all bacteria, Staphylococcus spp., Streptococcus spp. and Streptococcus-like organisms (SSLO), coliforms, Klebsiella spp., noncoliform gram-negatives, Bacillus spp., and Prototheca spp. in unused (n = 148) and used (n = 150) bedding. The association between bedding bacteria count and IMI was determined using multivariable logistic regression with mixed effects. Quarter-level prevalence of IMI was 21.1%, which was primarily caused by non-aureus Staphylococcus spp. (11.4%) and SSLO (5.6%). Only modest differences in IMI prevalence were observed between the 4 common bedding material types. Counts of all bacteria in unused bedding was positively associated with odds of IMI caused by any pathogen [ALL-IMI; odds ratio (OR) = 1.08]. A positive association was also observed for counts of SSLO in unused bedding and SSLO-IMI (OR = 1.09). These patterns of association were generally consistent across the 4 common bedding materials. In contrast, the association between counts of all bacteria in used bedding and ALL-IMI varied by bedding type, with positive associations observed in quarters exposed to manure solids (OR = 2.29) and organic non-manure (OR = 1.51) and a negative association in quarters exposed to new sand (OR = 0.47). Findings from this study suggest that quarter-level IMI prevalence in late-lactation cows is low in US dairy herds. Furthermore, bedding material type may not be an important risk factor for IMI in late lactation. Higher levels of bacteria in bedding may increase IMI prevalence at dry-off in general, but this relationship is likely to vary according to bedding material type.

Relationships among bedding materials, bedding bacteria counts, udder hygiene, milk quality, and udder health in US dairy herds

Bedding is an important source of teat end exposure to environmental mastitis pathogens. To better control environmental mastitis, we need an improved understanding of the relationships among bedding selection and management, bedding bacteria counts (BBC), and udder health (UH). The objectives of this cross-sectional observational study were (1) to describe BBC, bedding characteristics, udder hygiene scores, bulk tank milk (BTM) quality, and UH in US dairy herds using 1 of 4 bedding materials; (2) describe the relationship between BBC and herd measures of UH; and (3) identify benchmarks for monitoring bedding hygiene. Local dairy veterinarians and university researchers enrolled and sampled 168 herds from 17 states. Herds were on a Dairy Herd Improvement Association (DHIA) testing program and used 1 of 4 bedding types for lactating cows: new sand, reclaimed sand, manure solids (MNS), or organic non-manure materials. Each herd was sampled twice (winter and summer) in 2016. Samples and data collected included unused and used bedding, BTM samples, udder hygiene scores, DHIA test data, and descriptions of facilities and herd management practices. Bedding was cultured to determine the total bacteria count and counts of Bacillus spp., coliforms, Klebsiella spp., non-coliform gram-negative organisms, streptococci or streptococci-like organisms (SSLO), and Staphylococcus spp. Bedding dry matter, organic matter, and pH were also measured. Bulk tank milk samples were cultured to determine counts of coliforms, NAS, SSLO, Staphylococcus aureus, and Mycoplasma spp. Udder health measures included DHIA test-day average linear score (LS); the proportion of cows with an intramammary infection (IMI), where infection was defined as LS ≥4.0; the proportion of cows with a new IMI, where new IMI was defined as LS changing from <4.0 to ≥4.0 in the last 2 tests; the proportion of cows with a chronic infection, where chronic was defined as LS ≥4.0 on the last 2 tests; and the cumulative incidence of clinical mastitis in the 30-d period preceding sample collection. Although much variation existed within and among bedding types, mixed linear regression showed the use of MNS bedding to be generally associated with higher BBC, dirtier udders, increased coliform and SSLO counts in BTM, and poorer UH measures compared with organic non-manure materials, reclaimed sand, or new sand bedding materials. While controlling for important farm traits and management practices, mixed linear regression showed that increased counts of coliforms, Klebsiella spp., SSLO, and Staphylococcus spp. in both unused and used bedding were associated with poorer values for 1 or more herd-level measures of UH. Achievable benchmarks identified for counts of coliforms (unused: ≤500 cfu/cm³; used: ≤10,000 cfu/cm³), Klebsiella spp. (0 cfu/cm³ for unused and used), Staphylococcus spp. (0 cfu/cm³ for unused and used), and SSLO (unused: 0 cfu/cm³; used: ≤500,000 cfu/cm³) can be used to monitor bedding hygiene in most bedding materials, with minor variations suggested for SSLO in unused MNS (≤1,000 cfu/cm³).

Bedding and bedding management practices are associated with mesophilic and thermophilic spore levels in bulk tank raw milk

Mesophilic and thermophilic spore-forming bacteria represent a challenge to the dairy industry, as these bacteria are capable of surviving adverse conditions associated with processing and sanitation and eventually spoil dairy products. The dairy farm environment, including soil, manure, silage, and bedding, has been implicated as a source for spores in raw milk. High levels of spores have previously been isolated from bedding, and different bedding materials have been associated with spore levels in bulk tank (BT) raw milk; however, the effect of different bedding types, bedding management practices, and bedding spore levels on the variance of spore levels in BT raw milk has not been investigated. To this end, farm and bedding management surveys were administered and unused bedding, used bedding, and BT raw milk samples were collected from dairy farms (1 or 2 times per farm) across the United States over 1 yr; the final data set included 182 dairy farms in 18 states. Bedding suspensions and BT raw milk were spore pasteurized (80°C for 12 min), and mesophilic and thermophilic spores were enumerated. Piecewise structural equation modeling analysis was used to determine direct and indirect pathways of association among farm and bedding practices, levels of spores in unused and used bedding, and levels of spores in BT raw milk. Separate models were constructed for mesophilic and thermophilic spore levels. The analyses showed that bedding material had a direct influence on levels of spores in unused and used bedding as well as an indirect association with spore levels in BT raw milk through used bedding spore levels. Specific bedding and farm management practices as well as cow hygiene in the housing area were associated with mesophilic and thermophilic spore levels in unused bedding, used bedding, and BT raw milk. Notably, levels of spores in used bedding were positively related to those in unused bedding, and used bedding spore levels were positively related to those in BT raw milk. The results of this study increase the understanding of the levels and ecology of mesophilic and thermophilic spores in raw milk, emphasize the possible role of bedding as a source of spores on-farm, and present opportunities for dairy producers to reduce spore levels in BT raw milk.

Proposed dairy calf birth certificate data and death loss categorization scheme

The majority of dairy heifer calves in the United States are destined to be dairy replacements. However, many dairy heifer and bull calves die before 6 mo of age. Of these calves, about 6% (more than 500,000 calves) die at birth or shortly after (i.e., currently termed "stillbirth"). An additional 6% of dairy heifers die during the preweaning period. Death loss in dairy calves is primarily due to stillbirths, failure to adapt to extrauterine life, and infectious disease processes. The reasons for preweaning heifer calf deaths caused by infectious diseases are generally categorized based on easily recognizable clinical signs such as digestive disease/scours or respiratory disease. Most causes of calf death can be mitigated by appropriate preventive care or well-tailored treatments, meaning that the typical death loss percentage could be decreased with better management. Producers could gather information on the circumstances near birth and at death if they had appropriate guidance on what details to record and monitor. This paper provides recommendations on data to collect at the time of birth (i.e., calf birth certificate data). The recording of these critical pieces of information is valuable in evaluating trends over time in morbidity and mortality events in dairy calves. Ideally, necropsy examination would substantially improve the identification of cause of death, but even without necropsy, attribution of cause of death can be improved by more carefully defining death loss categories in on-farm record systems. We propose a death loss categorization scheme that more clearly delineates causes of death. Recommendations are provided for additional data to be collected at the time of death. Recording and analyzing birth certificate and death loss data will allow producers and veterinarians to better evaluate associations between calf risk factors and death, with the goal of reducing dairy calf mortality.

Evaluation of applying statistical process control techniques to daily average feeding behaviors to detect disease in automatically fed group-housed preweaned dairy calves

Group housing and computerized feeding of preweaned dairy calves are gaining in popularity among dairy producers, yet disease detection remains a challenge for this management system. The aim of this study was to investigate the application of statistical process control charting techniques to daily average feeding behavior to predict and detect illness and to describe the diagnostic test characteristics of using this technique to find a sick calf compared with detection by calf personnel. This prospective cross-sectional study was conducted on 10 farms in Minnesota (n = 4) and Virginia (n = 6) utilizing group housing and computerized feeding from February until October 2014. Calves were enrolled upon entrance to the group pen. Calf personnel recorded morbidity and mortality events. Farms were visited either every week (MN) or every other week (VA) to collect calf enrollment data, computer-derived feeding behavior data, and calf personnel-recorded calf morbidity and mortality. Standardized self-starting cumulative sum (CUSUM) charts were generated for each calf for each daily average feeding behavior, including drinking speed (mL/min), milk consumption (L/d), and visits to the feeder without a milk meal (no.). A testing subset of 352 calves (176 treated, 176 healthy) was first used to find CUSUM chart parameters that provided the highest diagnostic test sensitivity and best signal timing, which were then applied to all calves (n = 1,052). Generalized estimating equations were used to estimate the diagnostic test characteristics of a single negative mean CUSUM chart signal to detect a sick calf for a single feeding behavior. Combinations of feeding behavior signals were also explored. Single signals and combinations of signals that included drinking speed provided the most sensitive and timely signal, finding a sick calf up to an average (±SE) of 3.1 ± 8.8 d before calf personnel. However, there was no clear advantage to using CUSUM charting over calf observation for any one feeding behavior or combination of feeding behaviors when predictive values were considered. The results of this study suggest that, for the feeding behaviors monitored, the use of CUSUM control charts does not provide sufficient sensitivity or predictive values to detect a sick calf in a timely manner compared with calf personnel. This approach to examining daily average feeding behaviors cannot take the place of careful daily observation.

Randomized noninferiority study evaluating the efficacy of a postmilking teat disinfectant for the prevention of naturally occurring intramammary infections

The objective of this study was to complete a positive-control, natural exposure, noninferiority design field study to test the efficacy of a novel glycolic acid-based postmilking teat disinfectant as compared with a previously proven iodine-based postmilking teat disinfectant (positive control). The primary outcome of interest was the effect of treatment on incidence of new intramammary infections. Secondary outcomes included the effect of treatment on prevalence of infection, somatic cell count, and teat condition. After blocking by parity, approximately 300 early- to mid-lactation cows on a large Wisconsin dairy farm were randomly assigned to 1 of 2 groups. For a 12-wk period between May and August 2014, the 2 groups were dipped after each milking with either the experimental (EX) or positive control (PC) product. Individual quarters were sampled to establish bacteriological infection status at the beginning of the study, and every 2 wk thereafter, by use of a 2-stage process evaluating somatic cell count (SCC), and then culturing milk samples only when SCC exceeded a parity-specific threshold. Teat condition scoring was completed at the beginning of the study and on wk 4, 8, and 12. Mixed logistic regression was used to evaluate the effect of treatment on dichotomous outcome measures including the odds of acquiring a new infection during a given 2-wk sampling interval (incidence), the odds for presence of infection at sampling (prevalence), and odds for a normal teat skin condition score. Mixed linear regression was used to evaluate the effect of treatment on somatic cell count. For the noninferiority analysis, the upper bound of the 95% confidence interval for the difference in new infection rate between the 2 treatments (EX - PC), had to be to the left of the critical value d (0.035) to conclude that EX was noninferior relative to PC with respect to risk for new infections. Results showed that the incidence of new infections was not different for quarters dipped with EX (3.2%) as compared with PC (4.2%). Similarly, the prevalence of infection tended to be lower for quarters dipped with EX (3.92%) as compared with PC (5.03%). No overall difference was found between treatments when evaluating somatic cell count measures and teat condition scores. Because the upper bound of the 95% confidence interval of the new IMI rate difference was smaller than the predefined noninferiority limit, it was concluded that the experimental product was not inferior compared with the positive control. As such, the glycolic acid-based teat disinfectant evaluated in this study can be considered an effective postmilking teat disinfectant, as well as safe, in so far as the product was not irritating to teat skin and did not negatively affect skin condition measures, as compared with the positive control group.

Systematic early obstetrical assistance at calving: I. Effects on dairy calf stillbirth, vigor, and passive immunity transfer

A critical time for dairy cattle is the perinatal period. Good calving management is critical to reduce periparturient losses and ensure the health of the offspring. Generally, it has been recommended that cows be allowed to calve unassisted when possible, but very few studies have been published that support or refute this general guideline. To investigate the effect of early assistance, a clinical trial enrolled 257 Holstein cows that were observed through the second stage of calving and assigned randomly to 1 of 2 calving interventions: not assisted (NA) or early assistance (EA) during the second stage of parturition. Early assistance was given 15min after the first sight of both front hooves of the calf and done using only human force. After calving, the animals were classified into 4 actual calving intervention groups: too quick to be assisted (TQ), NA, EA, and late assistance (LA; for cows in the NA group that did not calve unassisted within the 1h maximum time frame allowed). Giving early assistance to cows during calving as a routine management practice (assigned intervention) did not negatively influence calves' stillbirth risk, vigor at birth, or transfer of passive immunity. Calves in the LA intervention group had significantly greater odds of stillbirth than calves in the NA and EA groups, respectively. Calves in the LA group also had significantly worse vigor at birth than calves in the TQ, NA, or EA groups. Early assistance given at calving to cows that did not present signs of calving difficulties did not adversely affect calves' likelihood of being stillborn, vigor at birth, or transfer of passive immunity.

Technical note: Preliminary evaluation of an automated indwelling rumen temperature bolus measurement system to detect pyrexia in preweaned dairy calves

Indwelling rumen temperature bolus (RTB) systems have the potential to offer a convenient and timely method of detecting pyrexia, indicative of active infectious disease. The aim of this pilot study was to evaluate the utility of using RTB systems in preweaned dairy calves. First, an in vitro study was performed to evaluate the accuracy of the RTB in its immediate environment. Thirteen RTB were immersed in a hot water bath (WB). Variably collected RTB temperatures were then matched to WB temperatures, which varied from 36 to 41°C, with 1h spent at each temperature. Second, an in vivo study was performed to evaluate the ability of the RTB to predict a rectal thermometer (RT) temperature. Ten healthy heifer calves less than 1wk of age were administered an RTB. Rectal thermometer and matched RTB temperatures were taken hourly, over a 6-h period, 1 day per week during wk 1, 3, 5, 7, and 9 of age. During each 6-h observation period, calves were offered both water and milk feedings and temperatures recorded every 15min for 1h thereafter. For both studies, the relationship between RTB and one of WB (in vitro) or RT temperature (in vivo) was described by calculating a concordance correlation coefficient (CCC) and by use of a multivariable linear regression model with repeated measures. For the in vivo study, the model also controlled for week and breed. Diagnostic test characteristics were calculated for the ability of individual RTB measures to detect pyrexia (RT ≥39.5°C). For the in vitro study, the association between the RTB and a known temperature was strong (CCC=0.95), but the RTB measures underestimated the temperature of the water bath by 0.43±0.08°C. For the in vivo study, the association between RT and the RTB temperature measurement in a calf was weaker (CCC=0.29); the average RTB temperature was 0.33±0.06°C lower than the RT temperature. The sensitivity (29%) and positive predictive value (17%) of using individual RTB measures to detect a fever was low. The results of this pilot study suggest that an individual RTB measurement may not be a good diagnostic test to detect pyrexia in calves.

Supplementing fresh bovine colostrum with gut-active carbohydrates reduces passive transfer of immunoglobulin G in Holstein dairy calves

High concentrations of coliform bacteria in maternal colostrum (MC) have been associated with reduced IgG absorption in calves. Mannan-oligosaccharide, a gut-active carbohydrate (GAC) derived from yeast cell wall, has been shown to adsorb pathogens expressing type-1-fimbriae, reducing their ability to colonize the gastrointestinal tract. The objective of this study was to investigate if addition of a GAC to colostrum would result in increased IgG absorption in newborn calves. Newborn Holstein heifer and bull calves were enrolled in summer 2012 at a commercial transition cow facility in western Wisconsin. Each day, 7.6-L pools of fresh, first milking MC were created, split into 3.8-L aliquots, and refrigerated until feeding. Eligible newborn calves were removed from the dam 30 to 60min after birth, weighed, and randomly assigned to be fed either 3.8 L of the MC pool (control) or 3.8 L of the MC pool with 30 g of GAC mixed in immediately before feeding. Duplicate 10-mL samples of colostrum were collected and frozen at -20°C before feeding (and before addition of GAC) for bacterial culture and IgG determination. A 10-mL venous blood sample was collected from calves before feeding colostrum and 24 h after colostrum feeding, for laboratory determination of serum IgG using radial immunodiffusion analysis. Colostrum and calf characteristics, including colostrum IgG concentration (g/L), colostrum bacteria counts (log10, cfu/mL), calf dystocia scores (1 to 4), birth weights (kg), and age at first feeding (min) were not different between the group fed GAC (n=47) and the control group (n=48). Mixed linear regression analysis showed that calves fed colostrum supplemented with 30 g of GAC had lower mean (standard error) apparent efficiency of absorption of IgG and lower serum IgG concentrations at 24 h [23.9% (1.0); IgG=24.0 (1.1) g/L] than did control calves [30.4% (1.0); IgG=30.8 (1.0) g/L]. Given the negative effect observed in this study, it is not recommended that fresh colostrum be supplemented with 30 g of GAC.

Effect of feeding heat-treated colostrum on risk for infection with Mycobacterium avium ssp. paratuberculosis, milk production, and longevity in Holstein dairy cows

In summer 2007, a randomized controlled field trial was initiated on 6 large Midwest commercial dairy farms to investigate the effect of feeding heat-treated (HT) colostrum on transmission of Mycobacterium avium ssp. paratuberculosis (MAP) and on future milk production and longevity within the herd. On each farm, colostrum was collected daily from fresh cows, pooled, divided into 2 aliquots, and then 1 aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60min. A sample from each batch of colostrum was collected for PCR testing (MAP-positive vs. MAP-negative). Newborn heifer calves were removed from the dam within 30 to 60min of birth and systematically assigned to be fed 3.8 L of either fresh (FR; n=434) or heat-treated (HT; n=490) colostrum within 2h of birth. After reaching adulthood (>2 yr old), study animals were tested once annually for 3 yr (2010, 2011, 2012) for infection with MAP using serum ELISA and fecal culture. Lactation records describing milk production data and death or culling events were collected during the 3-yr testing period. Multivariable model logistic and linear regression was used to investigate the effect of feeding HT colostrum on risk for testing positive to MAP during the 3-yr testing period (positive/negative; logistic regression) and on first and second lactation milk yield (kg/cow; linear regression), respectively. Cox proportional hazards regression was used to investigate the effect of feeding HT colostrum on risk and time to removal from the herd. Fifteen percent of all study animals were fed PCR-positive colostrum. By the end of the 3-yr testing period, no difference was noted in the proportion of animals testing positive for MAP, with either serum ELISA or fecal culture, when comparing the HT group (10.5%) versus the FR group (8.1%). There was no effect of treatment on first- (HT=11.797kg; FR=11,671kg) or second-lactation (HT=11,013kg; FR=11,235kg) milk production. The proportion of cows leaving the herd by study conclusion was not different for animals originally fed HT (68.0%) versus FR (71.7%) colostrum. Although a previous study showed that feeding HT colostrum (60°C for 60min) produces short-term benefits, including improved passive transfer of IgG and reduced morbidity in the preweaning period, the current study found no benefit of feeding HT colostrum on long-term outcomes including risk for transmission of Mycobacterium avium ssp. paratuberculosis, milk production in the first and second lactation, and longevity within the herd.

Brix refractometry in serum as a measure of failure of passive transfer compared to measured immunoglobulin G and total protein by refractometry in serum from dairy calves

A series of trials were conducted to evaluate Brix refractometry (Brix %) for the assessment of failure of passive transfer (FPT) in dairy calves compared to: (1) serum IgG (reference standard) when measured by radial immunodiffusion (RID) or a turbidometric immunoassay (TIA), and (2) serum total protein refractometry (STP). For the serum samples tested with TIA, STP, and Brix % (n = 310; Holstein calves), the median concentrations were 21.3 g/L IgG, 58 g/L STP, and 9.2%, respectively. For the serum samples tested with RID, STP and Brix % (n = 112; Jersey calves), the mean concentrations were 38 g/L IgG, 68 g/L STP, and 10.2%, respectively. For samples tested with only Brix % and STP (n = 265; Holstein calves), median STP and Brix % were 50 g/L STP and 8.5%, respectively. Correlations between Brix % and RID, and between Brix % and TIA were equal (r = 0.79, respectively). Brix % and STP were positively correlated (r = 0.99). Brix % estimated serum IgG concentrations determined by TIA and RID (r(2) = 0.63, 0.62, respectively). When FPT was defined as serum IgG < 10 g/L, Brix % ≤ 8.5% showed optimal sensitivity (100%) and specificity (89.2%) to predict FPT. At the same IgG cut-point, an STP value of ≤ 52 g/L showed a similar sensitivity (100%) and specificity (80.4%) to predict FPT. Brix refractometry predicted successful transfer of passive immunity in dairy calves, but further evaluation as a diagnostic tool for the diagnosis of FPT is warranted.

Effect of delayed exposure of cattle to Mycobacterium avium subsp paratuberculosis on the development of subclinical and clinical Johne's disease

OBJECTIVE

To evaluate the effect of delayed exposure of dairy cattle to Mycobacterium avium subsp paratuberculosis (MAP) on the incidence of those cows testing positive for MAP and developing clinical Johne's disease (CJD).

ANIMALS

79 cows not exposed to MAP as calves (unexposed cohort) and 260 cows exposed to MAP as calves (exposed cohort).

PROCEDURES

Cows in the unexposed cohort were born into 5 MAP-uninfected herds and introduced at various ages into 5 MAP-infected herds where the exposed cohort cows were born and raised. Beginning when each cow was 24 months old, fecal and serum samples were collected annually from 2003 through 2006. Feces were cultured for MAP, and an ELISA was used to analyze serum samples for antibodies against MAP. Date and reason for culling were obtained from herd records. Incidence of positive culture and ELISA results and CJD was compared between unexposed and exposed cohort cows with Cox regression.

RESULTS

Compared with exposed cohort cows, the hazard ratios for unexposed cohort cows having positive culture results, having positive ELISA results, and developing CJD were 0.12, 0.03, and 0.001, respectively, and those ratios increased by 2%, 6%, and 17%, respectively, for each month spent in an MAP-infected herd.

CONCLUSIONS AND CLINICAL RELEVANCE

Delayed exposure of cows to MAP resulted in lower incidences of positive culture and ELISA results and CJD in those cows, compared with incidences of cows exposed to MAP since birth. The hazard of testing positive for MAP or developing CJD increased with time, regardless of cohort.

Factors associated with morbidity, mortality, and growth of dairy heifer calves up to 3 months of age

Calfhood disease is an important problem on many dairy operations that can have substantial effects on heifer survival and productivity, and has economic and welfare impacts. Neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) are the most common causes of morbidity and mortality in young dairy cattle. The objective of this observational study was to investigate factors associated with the risks of morbidity and mortality, and with growth, in commercial dairy heifers calves. A total of 2874 heifer calves from 19 commercial dairy farms in Minnesota and Ontario were enrolled at 1-7 days of age and followed for approximately 3 months. Using cut-points of serum total protein of 5.2 and 5.7 g/dl, the incidences of failure of transfer of passive immunity (FTPI) were 11 and 32%, respectively. A cut-point of 5.7 g/dl was the most predictive of BRD before 5 weeks of age (sensitivity=40%, specificity=69%). The positive predictive value was poor (PPV=18%), but the negative predictive value was good (NPV=87%). A cut-point of 5.2g/dl was most predictive of death before 5 weeks of age (sensitivity=27%, specificity=89%, PPV=5%, NPV=98%). Serum total protein during the first week of life was a poor predictor of NCD. Over 23% of calves were treated for diarrhea. Risk factors were weight at enrollment, other diseases before 2 weeks of age, and an interaction between season of birth and herd-level incidence of NCD. Almost 22% of calves were treated at least once for BRD. Factors associated with an increased risk of BRD included herd-level incidence of BRD, season of birth, navel dipping, other diseases before 2 weeks of age, failure of transfer of passive immunity, and manual control of temperature in pre-weaning housing. Administration of supplemental antibody products at birth was associated with a reduced incidence of BRD. Overall mortality was 3.5%. Risk of mortality was increased by treatment for BRD and other diseases. The mean average weight gain was 0.95 kg/day (range: 0.11-1.62 kg/day; SD=0.2). Twinning status, FTP, treatment for NCD or other diseases, and month of birth influenced body weight. This study illustrated relationships among various diseases, mortality, and growth. Furthermore, it demonstrated the importance of colostrum for protection against BRD and improved growth performance, while bringing into question the optimal method of determining failure of transfer of passive immunity.

Heat-treated colostrum and reduced morbidity in preweaned dairy calves: results of a randomized trial and examination of mechanisms of effectiveness

A randomized controlled clinical trial was conducted using 1,071 newborn calves from 6 commercial dairy farms in Minnesota and Wisconsin, with the primary objective being to describe the effects of feeding heat-treated colostrum on serum immunoglobulin G concentration and health in the preweaning period. A secondary objective was to complete a path analysis to identify intermediate factors that may explain how feeding heat-treated colostrum reduced the risk for illness. On each farm, colostrum was collected each day, pooled, and divided into 2 aliquots; then, one aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60 min. Samples of fresh and heat-treated colostrum were collected for standard microbial culture (total plate count and total coliform count, cfu/mL) and for measurement of immunoglobulin G concentrations (mg/mL). Newborn calves were removed from the dam, generally within 30 to 60 min of birth, and systematically assigned to be fed 3.8L of either fresh (FR, n=518) or heat-treated colostrum (HT, n=553) within 2h of birth. Venous blood samples were collected from calves between 1 and 7d of age for measurement of serum IgG concentrations (mg/mL). All treatment and mortality events were recorded by farm staff between birth and weaning. Regression models found that serum IgG concentrations were significantly higher in calves fed HT colostrum (18.0 ± 1.5 mg/mL) compared with calves fed FR colostrum (15.4 ± 1.5 mg/ml). Survival analysis using Cox proportional hazards regression indicated a significant increase in risk for a treatment event (any cause) in calves fed FR colostrum (36.5%, hazard ratio=1.25) compared with calves fed HT colostrum (30.9%). In addition, we observed a significant increase in risk for treatment for scours in calves fed FR colostrum (20.7%, hazard ratio=1.32) compared with calves fed HT colostrum (16.5%). Path analysis suggested that calves fed HT colostrum were at lower risk for illness because the heat-treatment process caused a significant reduction in colostrum total coliform count, which was associated with a reduced risk for illness as a function of improved serum IgG concentrations.

Short communication: improving passive transfer of immunoglobulins in calves. III. Effect of artificial mothering

The objective of this study was to investigate the effect of artificial mothering, simulated by verbal and physical stimulation of the newborn, on passive transfer of IgG in the dairy calf. Newborn heifer calves born without dystocia were removed from the dam before suckling and randomly assigned to 1 of 2 treatment groups: no tactile or verbal stimulation other than that required for feeding (group 1; n=20), or artificial mothering, consisting of 15 min of vigorous physical and verbal stimulation conducted within 1 to 2h of birth at the time of colostrum feeding and repeated 1 to 2h later (group 2; n=21). All calves were fed 2.25 L (150 g of IgG) of a commercially available colostrum replacement using an esophageal tube feeder. Blood samples collected at 24h of age showed that serum IgG levels and the apparent efficiency of absorption of the IgG were similar in both groups of calves. Artificial mothering by physical and verbal stimulation had no significant effect on IgG passive transfer in dairy heifers born without dystocia.

Effect of a plasma-derived colostrum replacement feeding program on adult performance and longevity in Holstein cows

OBJECTIVE

To evaluate longevity, milk production, and breeding performance in adult Holstein cows fed either a plasma-derived commercial colostrum replacer (CR) or raw bovine maternal colostrum (MC) at birth.

DESIGN

Randomized controlled clinical trial.

ANIMALS

497 heifer calves born in 12 commercial dairies located in Minnesota and Wisconsin.

PROCEDURES

All calves were separated from their dams within 30 to 60 minutes after birth and systematically assigned to be fed either MC (control group [n = 261 calves]) or CR (treatment group [236]). Calves were observed from birth up to adulthood (approx 54 months old), during which time death and culling events plus milk yield and breeding performance data were collected. Time to death, time to culling, time to death or culling combined, time to first calving, and time to conception intervals were evaluated by use of proportional hazards survival analysis models. Number of times inseminated per conception and lifetime milk yield (up to 54 months old) were evaluated by use of general linear models.

RESULTS

Cows fed CR as calves at the time of birth were no different than cows fed MC as calves with respect to overall risk of death, culling, or death or culling combined (from birth to 54 months of follow-up and from first calving to 54 months old); lifetime milk yield; and breeding performance.

CONCLUSIONS AND CLINICAL RELEVANCE

No difference was detected in overall risk of death or culling, milk production, or reproductive performance between cows fed CR and those fed MC as calves at birth.

Experimental validation of a nested polymerase chain reaction targeting the genetic element ISMAP02 for detection of Mycobacterium avium subspecies paratuberculosis in bovine colostrum

Colostrum samples experimentally inoculated with Mycobacterium avium subsp. paratuberculosis (MAP; strain K-10) at increasing concentrations between 1 x 10(1) and 1 x 10(9) cells/ml were tested for recovery of MAP DNA using a nested ISMAP02 target polymerase chain reaction initially developed for detecting MAP DNA in fecal samples. The following detection rates were achieved for sample replicates inoculated with unsonicated MAP pure stock: 100% between 1 x 10(7) and 1 x 10(9) cells/ml, 75% between 1 x 10(3) and 1 x 10(6) cells/ml, and 50% between 1 x 10(1)and 1 x 10(2) cells/ml replicates. Detection rates achieved for the colostrum sample replicates inoculated with sonicated MAP cell suspension were 75% for 1 x 10(9) cells/ml, 100% between 1 x 10(7) and 1 x 10(8) cells/ml, 75% for 1 x 10(6) cells/ml, 0 for 1 x 10(4) cells/ml, and 25% between 1 x 10(1) and 1 x 10(3) cells/ml. When negative control colostrum samples were tested, 16 of 18 (89%) samples were correctly detected as negative for MAP DNA using the current assay. In conclusion, the MAP DNA detection rates of the present assay improved with increasing concentrations of MAP in the colostrum sample replicates, although MAP DNA was also detected in 2 of 18 (11%) negative control samples, suggesting an undefined technical problem with the assay or, perhaps, sample contamination during preparation. Overall, the present findings suggest a potential role of the proposed polymerase chain reaction assay to detect MAP in colostrum. However, adoption of this test for use in routine screening of field colostrum for MAP awaits findings from an ongoing field validation study.

The effect of injectable butaphosphan and cyanocobalamin on postpartum serum beta-hydroxybutyrate, calcium, and phosphorus concentrations in dairy cattle

The objective of this study was to determine the effect of an injection of 10% butaphosphan and cyanocobalamin (Catosal, Bayer, Shawnee Mission, KS) on the day of calving and 1 d later on the prevalence of subclinical ketosis in dairy cattle in the early postpartum period. Cows from 4 herds (n=1,122) were randomized to receive either 25mL of 10% butaphosphan and cyanocobalamin or 25mL of sterile water subcutaneously on both days. Each milliliter of Catosal contained 0.05mg of cyanocobalamin and 100mg of butaphosphan, which provided 17.3mg of P in the form of [1-(butylamino)-1-methylethyl]-phosphonic acid. Serum was sampled for beta-hydroxybutyrate (BHBA) concentration at calving (pretreatment) and again between 3 and 10 d in milk. A subset of samples from mature cows was also evaluated for serum Ca and P concentrations. When cows from all age groups were included in the analysis, there was no difference between the median serum BHBA concentrations of cows in the 2 treatment groups, and no difference in the proportion of hyperketonemic cows (serum BHBA >or=1,200micromol/L) during the first week postpartum. When the analysis was restricted to mature cows (lactation >or=3), both the median BHBA concentration and the proportion of hyperketonemic cows were significantly lower in the treatment group than in the placebo group. Serum Ca and P concentrations did not differ between treatment groups. Our results suggest that injection of butaphosphan and cyanocobalamin on the day of calving and 1 d later may decrease the prevalence of subclinical ketosis during the week after calving in mature dairy cows, but not in first- and second-lactation animals.

Evaluation of diffusion of triamcinolone acetonide from the distal interphalangeal joint into the navicular bursa in horses

OBJECTIVE

To determine whether triamcinolone acetonide diffuses from the distal interphalangeal joint (DIPJ) to the navicular bursa, diffusion is direct or systemic, and addition of sodium hyaluronan has an effect on diffusion in horses.

ANIMALS

11 adult horses without forelimb lameness.

PROCEDURES

1 randomly chosen forelimb DIPJ of each horse received an injection of 10 mg of triamcinolone acetonide plus 20 mg of sodium hyaluronan (group 1), and the contralateral forelimb DIPJ received an injection of 10 mg of triamcinolone acetonide plus 2 mL of lactated Ringer's solution (group 2). Synovial fluid samples were taken from both forelimb navicular bursae and 1 hind limb navicular bursa (systemic control group) at 6 hours. Triamcinolone acetonide concentrations in synovial fluid were quantified by use of high-performance liquid chromatography plus tandem mass spectrometry. Data were logarithmically transformed, and contrast analysis was performed on the 3 groups.

RESULTS

Triamcinolone acetonide was detected in navicular bursal samples in all groups. Groups 1 and 2 had significantly greater concentrations of triamcinolone acetonide than the systemic control group. There was no significant difference between groups 1 and 2.

CONCLUSIONS AND CLINICAL RELEVANCE

Triamcinolone acetonide diffused directly from the DIPJ into the navicular bursa in clinically normal horses, and diffusion was not affected by addition of hyaluronan. Injection into the DIPJ with triamcinolone acetonide or a triamcinolone acetonide-hyaluronan combination can potentially be used for treatment of navicular syndrome, but further studies are needed to determine whether triamcinolone acetonide diffuses similarly in horses with navicular syndrome.

Clinical trial on type of calving pen and the risk of disease in Holstein calves during the first 90 d of life

The objective of this study was to evaluate the efficacy of single cow calving pens that are cleaned between calvings vs. multiple cow calving pens for the prevention of calf diarrhea (scours), respiratory disease (pneumonia) and morbidity attributable to any cause.

Every other pregnant cow or heifer was moved to either the single cow calving pen (treatment) or the multiple cow calving pen (control) within 48–72 h prior to actual calving. The calves born in the single cow calving pens were assigned to the treatment group while the calves born in the multiple calving pens were assigned to the control group. Fecal materials, placental remains, and any other conspicuous dirt were removed from the single cow calving pens between each calving prior to the introduction of the next pregnant cow. The calves were then separated from their dams within 2 h of birth. Multiple cow calving pens were managed as usual at the producers’ discretion. Upon birth, the calf managers monitored each enrolled calf for signs of diarrhea, pneumonia plus other morbidity up to 90 d of age. The effects of single cow calving pens (vs. multiple cow calving pens) that are cleaned between calvings on the risk of neonatal calf diseases were evaluated using multivariable logistic regression models. Risk of diarrhea (OR = 0.93, P = 0.75), pneumonia (OR = 1.23, P = 0.64), and morbidity due to any cause (OR = 0.93, P = 0.74) were not significantly different between calves born in single cow vs. multiple cow calving pens.

The current study found that, given the management situation evaluated, calves born in single cow calving pens were no different than calves born in multiple cow calving pens with respect to calf diseases risk. Long-term follow-up of the calves enrolled in the present study is ongoing to determine the efficacy of single cow calving pen use for the possible prevention of transmission of Mycobacterium avium subsp. paratuberculosis in Holstein calves.

The association between Mycobacterium avium subsp. paratuberculosis fecal shedding or clinical Johne's disease and lactation performance on two Minnesota, USA dairy farms

Lactation performance of cows infected with Mycobacterium avium subsp. paratuberculosis (Map) was previously studied using only serum ELISA as a diagnostic method. This study evaluated on two dairy farms in Minnesota, USA the lactation performance (measures of health, production, reproduction, and survival) of cows shedding Map in feces before calving and of cows culled with clinical signs consistent with Johne's disease (JD) during the subsequent lactation. Fecal samples were collected from 1052 cows within 21 day before calving and tested for Map with bacterial culture. Producers' observed signs of clinical disease (milk fever, retained placenta, metritis, ketosis, displaced abomasum, lameness, mastitis, pneumonia, and JD) and production and reproduction data were recorded for each cow. The association between fecal shedding or clinical JD and lactation performance was evaluated. Logistic regression was used to evaluate the association with any clinical and subclinical diseases as the outcome. General linear model was used to evaluate the association with milk production, and survival analysis techniques were used to evaluate the association with days in the study before culling and days from calving to conception. In 84 cows (8% of 1052 cows) fecal samples were positive for Map (46% light, 26% moderate, and 28% heavy shedders). In multivariable analysis, light, moderate, and heavy fecal shedding cows produced on average 537, 1403, and 1534 kg, respectively, less milk per lactation and 1.4, 5.2, and 7.5 kg, respectively, less milk per day than fecal negative cows. Fecal culture positive cows were less likely to be bred and conceive. In the multivariable analysis the 56 cows culled with presumed JD produced approximately 1500 kg/lactation or 5 kg/day less than all other cows. The negative economic impact implied by decreased lactation performance in cows shedding Map or with clinical JD may motivate producers to implement programs to control Map infection and subsequent JD.

Characterization of Minnesota dairy herds participating in a Johne's disease control program and evaluation of the program risk assessment tool

The objectives of this study were to: (1) characterize Minnesota dairy herds participating in a Johne's disease control program (JDCP) based on herd size, milk production, and clinical Johne's disease (JD) history, (2) evaluate if change in farm management practices, expressed in risk assessment (RA) total score, is associated with the change between the first and most recent ELISA test herd seroprevalence or change in clinical JD culling rate, and (3) identify farm factors associated with ELISA seroprevalence. A total of 1234 RA, performed between January 2000 and February 2004, were available for analysis from 714 dairy herds. ELISA test results from herd sampling between 2000 and 2004 were obtained from the Minnesota board of animal health (MBAH) database, and were available for 474 herds. Both the first and the most recent ELISA test results for herds with more than one RA were available for 262 herds. Mean herd size and mean annual milk production per cow was higher in JDCP dairy herds (161 milking cows) than either all Minnesota dairy herds or Minnesota dairy herd improvement association (DHIA) herds. For herds with more than one RA available, the most recent RA total score was significantly lower (mean 11% less) than the first. The change in RA total score (and any RA subtotal scores) between the first and most recent RA was not associated with the change between the first and the most recent ELISA within-herd seroprevalence or the change in JD culling rate between the first and most recent RA. The most recent ELISA test results were positively associated with postweaned heifer score and JD culling rate. The RA score was not found to be an effective tool for the prediction of ELISA seroprevalence.