Dairy farmer's income, working time, and antimicrobial use under different dry cow therapy protocols.

Mastitis is one of the most common diseases of dairy cattle. It has a high impact on farm economy, farmers' working time, and antimicrobial usage (AMU). Selective dry cow therapy (SDCT) is an effective means of reducing AMU without negatively affecting udder health. The objective of our study was to evaluate the impact of SDCT implementation on farmer's income, working time, and AMU, using a bioeconomic model. A stochastic dairy simulation model (DairyHealthSim) based on a weekly model was used to simulate herd dynamics, reproduction, milk production, culling decisions, health outcomes, and the management of health events. A specific module was developed for the simulation of quarter-level intramammary infection (IMI) acquisition and elimination during the lactation and dry-off periods, and 25 different farm settings were defined to represent herds with various udder health situations. We then defined 20 scenarios of SDCT by combining both the use of different thresholds of somatic cell count and milk bacteriology for treatment allocation and the use of internal teat sealant (ITS). All SDCT protocols had a low impact on farmer's income, and we identified some protocols with a positive farm gross margin (up to 15.83 CA$/dried- cow). We also found that adding an ITS to all cows led to greater economic gain. The application of SDCT had a low impact on farmers' working time, except when milk bacteriology was used for decision-making. Antimicrobial treatment to all cows above 200,000 cells/mL at last control, with the use of ITS on all cows, seems a good choice in most dairy farms. These findings could be used to convince farmers to adopt this strategy at dry-off.

Evaluation of potassium monopersulfate footbath solution for controlling digital dermatitis in lactating dairy cattle. A randomized clinical trial.

Our objective was to assess potassium monopersulfate as a disinfectant used in footbath to control digital dermatitis (DD) in dairy cows. We hypothesized that a potassium monopersulfate solution would control DD. A 180-day randomized negative controlled trial was conducted in a 265-Holstein free-stall facility. Throughout the trial, foot bathing was performed bi-weekly using a split (left vs. right feet) footbath: one tub filled with 1% potassium monopersulfate (treatment), the other with tap water (control). Digital dermatitis lesions were scored during trimming chute examinations of the unwashed hind heels every 90 days using the modified M-scoring system. Digital dermatitis lesions were re-categorized into four variables: 1) inactive; 2) active; 3) any; 4) inactive or absence of DD lesions. Three longitudinal outcomes were characterized: risks of 1) developing a DD lesion; 2) reactivating an inactive DD lesion; 3) development of an inactive or the absence of the DD lesion. A generalized linear model was used to compare the variables and longitudinal outcomes between treated and control groups. Prevalence of active DD lesions increased from 12.5% to 39.9% between days 0 and 90. This significant increase in prevalence justified the discontinuation of the study on day 90 for ethical reasons. There was no statistical difference between treated and control groups for the first outcome (RR: 1.0; 95% CI: 0.62, 1.7), the second outcome (RR: 1.0; 95% CI: 0.62,-1.7); or the third outcome (RR: 0.88; 95% CI: 0.37, 2.1). A 1% potassium monopersulfate footbath solution appears ineffective to control DD in this study.

Health indicators in surplus calves at the time of arrival at auction markets: Associations with distance from farms of origin in Québec, Canada.

This study evaluated the associations between estimated distance from farms' locations to auction markets, and health indicators of surplus dairy calves sold during summer 2019 and winter 2020 in Québec, Canada. A total of 3,610 animals from 1,331 different farms were used in this cross-sectional cohort study. Geographic coordinates (latitude and longitude) were obtained for each farm and the 2 participating livestock auction markets. Calves' abnormal physical signs (APS) were noted upon arrival at the auction market as they were examined by trained research staff. The haversine distance between the farm and the auction market was evaluated using geographic coordinates and categorized. Generalized linear mixed models were used for statistical analyses. The main APS observed were ocular discharge (34.9%), abnormal hide cleanliness (21.2%), swollen navel (17.2%), dehydration score 1 (at least one of the 2 following clinical signs: persistent skin tent or sunken eye, 12.9%), and dehydration score 2 (both clinical signs mentioned above, 6.5%). Calves from farms located at greater distances from the auction markets (≥110 km) had a higher risk ratio [RR = 1.08; 95% confidence internal (CI) = 1.03, 1.13] for dehydration than those from lesser distances (0-25 km). During the summertime, a RR of 1.18 (95% CI = 1.15, 1.22) was observed for dehydration compared with wintertime. A 2-way interaction between estimated distance and season showed a higher prevalence of ocular discharge for calves from farms at distances greater than or equal to 110 km during the summer (RR = 1.11; 95% CI: 1.04, 1.20) than for calves from farms located at lesser distances (0-25 km). These results demonstrate that calves from farms located at greater distances from the auction markets had more APS, mainly during the summer. A better understanding of the transport conditions and interaction with management at the farm of origin is determinant to mitigate the impact of the journey on surplus calf health.

Development of a Nomogram to Estimate the 60-Day Probability of Death or Culling Due to Severe Clinical Mastitis in Dairy Cows at First Veterinary Clinical Evaluation.

Severe clinical mastitis is a frequent disease of dairy cattle. An effective mean of predicting survival despite treatment would be helpful for making euthanasia decisions in poor prognosis cases. The objective was to develop a nomogram for prediction of death or culling in the 60 days following a severe mastitis episode in dairy cows at first veterinary visit in farm settings. A total of 224 dairy cows presenting severe clinical mastitis and examined for the first time by a veterinarian were included in a prospective study. Clinical and laboratory (complete blood cell count, L-lactate, cardiac troponin I, milk culture) variables were recorded. Animals were followed for 60 days. A nomogram was built with an adaptive elastic-net Cox proportional hazards model. Performances and relevance were evaluated by area under the receiver operating characteristic curve (AUC), Harrell's concordance index (C-index), calibration curve, decision curve analysis (DCA) and misclassification cost term (MCT). The nomogram included: lactation number, recumbency, depression intensity, capillary refilling time, ruminal motility rate, dehydration level, lactates concentration, hematocrit, band neutrophils count, monocyte count, and milk bacteriology. The AUC and C-index showed a good calibration and ability to discriminate. The DCA suggested that the nomogram was clinically relevant. Euthanizing animals having less than 25% probability of survival is economically optimal. It could be used for early euthanasia decisions in animals that would not survive despite treatment. To facilitate the use of this nomogram by veterinarians, a web-based app was developed.

Use of ATP luminometry to assess the cleanliness of equipment used to collect and feed colostrum on dairy farms.

The objective of this observational cross-sectional study was to describe the cleanliness of various equipment used for colostrum harvest and calf feeding procedures on dairy farms in Québec, Canada. The study was performed on 42 commercial dairy herds also enrolled in another study aiming to determine the transfer of passive immunity over a 14-mo period. Information on colostrum quality (using Brix value) and cleanliness (total aerobic and total coliform count) were recorded as well as various practices focused on colostrum-feeding equipment and preweaning period using a standard questionnaire. During the study period, colostrum and milk-feeding equipment cleanliness was assessed using direct surface swabbing with Hygiena Ultrasnap swabs. A total of 155 swab samples were obtained from 6 pieces of equipment. Adenosine triphosphate collected from the swabbed surface reacts with the luciferase solution present in the swab by bioluminescence, which is proportional to the quantity of ATP present and quantified as relative light units (RLU). The description of feed equipment cleanliness (defined as the maximal RLU found for a specific herd, dichotomized as <1,000 RLU vs. ≥1,000 RLU) was compared with the herds' descriptive characteristics, focusing on the first 2 components of a multiple correspondence analysis. The median (range) RLU for buckets used for colostrum harvest, bucket or bottle used for feeding, tube feeders, milking colostrum line, and internal surface of the nipples were 41 RLU (3-1,625 RLU), 78 RLU (<1-3,765 RLU), 29 RLU (<1-2,177 RLU), 83 RLU (<1-9,968 RLU), and 1,101 RLU (2-9,546 RLU), respectively. The first 2 components of multiple correspondence analysis explained 24.7% of data variances and were related to the farms' hygiene and health (13.0%) and feeding practices (11.7% of data variance). The maximal dichotomized luminometry value (<1,000 RLU or ≥1,000 RLU) was associated with hygiene and health dimension. This study gave promising results concerning the potential application of ATP luminometry for calf rearing practices assessment.

Validation of On-Farm Bacteriological Systems for Endometritis Diagnosis in Postpartum Dairy Cows.

The objective of this study was to validate the accuracy of the results of on-farm bacteriological culture media (Tri-plate and Petrifilm) from endometrial samples compared with the ones from the diagnostic laboratory. A cross-sectional observational study was set up within two dairy herd clients of the Université de Montréal. A total of 189 cows in the postpartum period were systematically enrolled to collect two uterine samples from cytobrushes during the same examination. The first cytobrush was used to inoculate the Tri-plate medium directly and then was sent to the reference laboratory for aerobic bacterial culture. The second cytobrush was used to make a microscopic smear for cytological analysis (proportion of polymorphonuclear cells) and subsequently diluted in 1 mL of saline to inoculate the Petrifilm medium. From these data, statistical analyses were computed to optimize the summation of sensitivity and specificity of the two systems compared with the results of the reference laboratory. For the Tri-plate and Petrifilm media, the cutoffs of ˃90 and ˃100 colonies gave the maximum sum of sensitivity and specificity, respectively. In conclusion, Tri-plate media was best at reproducing the results obtained by laboratory analysis using a threshold of >90 colonies.

The effect of pegbovigrastim on early-lactation disease, production, and reproduction in dairy cows.

The objective of this randomized, double-blind, controlled trial was to evaluate the effect of pegbovigrastim (pegylated recombinant bovine granulocyte colony-stimulating factor) on early-lactation disease, milk yield, and reproduction on commercial dairy farms. A total of 1,607 Holstein cows from 6 farms in Ontario and Québec, Canada, were randomly assigned to receive two 2.7-mL subcutaneous injections of either 15 mg of pegbovigrastim (n = 798; Imrestor, Elanco) or sterile physiological saline (placebo; n = 809). The first injection was administered by investigators 1 wk before expected calving, and the second by farm personnel within 24 h after calving, according to the product label. Producers inspected cows daily and using standardized disease definitions, recorded cases of retained placenta, metritis, displaced abomasum, and clinical mastitis until 63 d in milk. Progesterone concentration was measured in serum at wk 3, 5, 7, and 9 postpartum. Cows were examined for purulent vaginal discharge using the Metricheck (Simcro) device and endometritis using the cytobrush method at wk 5 postpartum. Milk production and reproduction data were obtained from farm management software and the national milk recording database. Disease and culling outcomes were assessed with logistic regression, milk production with linear regression, and time-to-event outcomes with proportional hazards regression. All analyses considered parity and pre-treatment body condition score and their interaction with treatment, and accounted for clustering of cows within farm. In a subset of 246 cows, the effect of treatment on metabolic markers (serum concentrations of glucose, ß-hydroxybutyrate, nonesterified fatty acids, cholesterol, haptoglobin, albumin, and calcium) was assessed in wk 1 and 2 postpartum. Pegbovigrastim had no significant effects on the incidence of retained placenta, metritis, displaced abomasum, clinical or subclinical mastitis, purulent vaginal discharge, or endometritis. Treatment reduced the serum concentration of glucose, slightly reduced the concentration of albumin, and slightly increased concentrations of ß-hydroxybutyrate and nonesterified fatty acids, with no effect on the other markers. There were no differences between treatments in culling risk, time to first insemination, pregnancy at first insemination, or time to pregnancy. Milk yield over the first 3 test days of lactation was 1.0 kg per day lower in the pegbovigrastim group, although a mechanism for that effect could not be explained through analysis of our data.

Scoping review on clinical definition of bovine respiratory disease complex and related clinical signs in dairy cows.

Bovine respiratory disease complex (BRD) is a worldwide multifactorial infectious disease. Antimicrobials are commonly used for treating BRD because bacteria are often involved. The clinical diagnosis of BRD is a challenge, especially in adult dairy cows, where information on this syndrome is scant. Having a definition based on consistent and reliable clinical signs would improve the accuracy of BRD diagnosis and could help to develop an optimal treatment approach by an early detection. The aim of this scoping review was to review clinical signs that could be recognized by producers in dairy cattle suffering from naturally occurring infectious respiratory disease, as reported in the literature. A review of the literature was performed for articles published between January 1, 1990 and January 1, 2020. The search of literature in English, French, and Italian languages included 2 different databases (Pubmed, https://pubmed.ncbi.nlm.nih.gov/; CAB abstract, https://www.cabi.org/publishing-products/cab-abstracts/). Clinical signs were categorized as follows: (1) "general manifestations of disease," which included behavioral changes or fever; (2) "alterations in respiratory function," which included clinical signs specifically associated with the respiratory tract examination; and (3) "clinical signs of other body systems," which included clinical signs related to other systems such as diarrhea or subcutaneous emphysema. The focus of the review was on clinical signs that could be monitored by animal handlers and producers. A total of 1,067 titles were screened, and 23 studies were finally included. The most common general clinical signs were increased body temperature (reported in 83% of studies, n = 19), change in feed intake (26%, n = 6), altered mentation (22%, n = 5), and decreased milk production (17%, n = 4). The alterations in respiratory function noted were nasal discharge (74%, n = 17), cough (65%, n = 15), altered respiratory dynamic or dyspnea (61%, n = 14), increased respiratory rate (43%, n = 10), and ocular discharge or lacrimation (30%, n = 7). The clinical signs associated with infectious respiratory disease reported in the 23 studies generally lacked a clear description of what constitutes a deviation from normality (0-50% of studies clearly reported what was considered normal versus abnormal depending on the clinical signs). This limitation prevented any comparison between studies that apparently reported the same "clinical sign," but possibly referred to a different assessment and definition of what was considered normal versus abnormal. Therefore, the definition of clinical signs in a repeatable way with validated interobserver agreement to determine the optimal combination for the diagnosis of BRD in dairy cows is needed. This could lead to a more judicious use of antimicrobials for respiratory disease in adult dairy cows.

Prevalence of shedding and antibody to Coxiella burnetii in post-partum dairy cows and its association with reproductive tract diseases and performance: A pilot study.

The bacterium Coxiella burnetii has been associated with reproduction disorders in dairy cattle. A cross-sectional study was conducted in Québec, Canada, to estimate the prevalence of C. burnetii in dairy cows from C. burnetii RT-PCR-positive and/or ELISA-positive herds. As a secondary objective, the associations between C. burnetii-positivity and three reproductive outcomes (purulent vaginal discharge, cytological endometritis, and success at first service) were assessed. A total of 202 post-parturient dairy cows from nine herds were sampled at 35 ± 7 days in milk. Vaginal mucus and composite milk were collected from each cow and screened for the presence of C. burnetii by real-time PCR (RT-PCR) and ELISA, respectively. Purulent vaginal discharge and cytological endometritis were evaluated using a Metricheck device and a modified cytobrush, respectively. The first insemination postpartum was done following an ovulation synchronization protocol around 70 days in milk, and success at first service was recorded. Multilevel logistic regressions adjusted for parity were used to model purulent vaginal discharge, cytological endometritis and success at first service according to C. burnetii cow status. All 202 RT-PCR-assayed vaginal samples were C. burnetii-negative. A positive result for anti-C. burnetii antibodies detection in composite milk was obtained in 25/202 samples and a doubtful result in 4/202 samples. After adjustment for sampling weights, the 202 ELISA-assayed composite milk samples gave an estimated overall prevalence of C. burnetii positive cows of 12.9 % (CI = 6.1-19.6 %) and of doubtful cows of 1.4 % (CI = 0.0-3.3 %). The proportion of ELISA-positive cows was lower in first parity (0%) compared to second (17.1 %) or third parity cows (20.0 %). The associations between ELISA positivity and reproductive outcomes were not statistically significant, perhaps due to the limited sample size, but could be used as pilot estimate for large-scale studies investigating the impact of C. burnetii infection on reproduction disorders in dairy cattle.

Gap between producers and veterinarians regarding biosecurity on Quebec dairy farms.

As part of the ProAction on-farm program to implement national biosecurity requirements on dairy farms, Canadian veterinarians are called upon to complete biosecurity risk assessments. The objective of the present study was consequently to understand veterinarians' perceptions of biosecurity, and to compare perceptions among producer-veterinarian pairs. Questionnaires were administered to 106 producers from Quebec and their veterinarians (n = 82), and the answers of the producer-veterinarian pairs were compared. While most veterinarians reported it was easy to discuss biosecurity with their clients, most veterinarians and producers did not report discussing biosecurity. Moreover, when producers or veterinarians reported discussing biosecurity topics, there was no agreement amongst pairs. Veterinarians also misjudged how their clients perceived the importance and usefulness of biosecurity. Finally, veterinarians reported they had the knowledge and opportunity to assess and discuss biosecurity on dairy farms but lacked skills for evaluating farms and communicating their knowledge.

Différences entre les producteurs et les vétérinaires en matière de biosécurité dans les fermes laitières du Québec. Dans le cadre du programme à la ferme ProAction visant à mettre en oeuvre les exigences nationales de biosécurité dans les fermes laitières, les vétérinaires canadiens sont appelés à effectuer l'évaluation des risques reliés à la biosécurité. L'objectif de cette étude était, par conséquent, de comprendre la perception qu'ont les vétérinaires de la biosécurité et de comparer cette perception entre les paires producteurs-vétérinaires. Des questionnaires ont été administrés à 106 producteurs québécois et à leurs vétérinaires (n = 82). Les réponses des paires producteurs-vétérinaires ont été comparées. Alors que la plupart des vétérinaires ont déclaré qu'il était facile de discuter de biosécurité avec leurs clients, la plupart des vétérinaires et des producteurs n'ont pas déclaré en avoir discuté dans l'année précédant l'étude. De plus, lorsque les producteurs ou les vétérinaires ont rapporté avoir discuté de sujets liés à la biosécurité, il n'y avait pas d'accord entre les paires. Les vétérinaires ont également mal évalué la façon dont leurs clients percevaient l'importance et l'utilité des mesures de biosécurité. Enfin, les vétérinaires ont indiqué qu'ils avaient les connaissances et la possibilité d'évaluer et de discuter de la biosécurité dans les exploitations laitières, mais manquaient de compétences pour évaluer les exploitations et communiquer leurs connaissances.(Traduit par Dr José Denis-Robichaud).

Bayesian assessment of diagnostic accuracy of a commercial borescope and of trimming chute exams for diagnosing digital dermatitis in dairy cows.

Digital dermatitis (DD) is a worldwide infectious disease of cattle that causes lameness, discomfort, and economic losses. The reference standard test to diagnose DD is visual observation in a trimming chute, which cannot be practically performed daily on dairy farms. Moreover, some lesion misclassification may occur using this standard diagnostic method. The possibility of misclassification makes the use of a trimming chute debatable as a perfect reference standard test. The objective of this study was, therefore, to assess the diagnostic accuracy of a commercial borescope and trimming chute exam. The accuracy (sensitivity and specificity) of the tests and DD prevalence were investigated using Bayesian latent class analyses. Our hypothesis was that a commercial borescope can be routinely used to diagnose DD in a milking parlor without previous feet cleaning. A cross-sectional study was performed in a freestall facility. The lesions were scored (M0, M1, M2, M3, M4, M4.1) in the milking parlor with a borescope, followed by an examination in the trimming chute 48 to 72 h after the borescope exam. A total of 870 hind feet were scored during 2 sessions of trimming chute exams and borescope exams in the milking parlor. The data were analyzed in 2 ways. First, data were dichotomized into DD lesions (M1, M2, M3, M4, M4.1) and absence of DD lesions (M0). Second, data were dichotomized into active DD lesions (M1, M2, M4.1) and inactive lesions (M0, M3, M4). A Bayesian latent class model allowing for conditional dependence between tests was used to estimate tests' accuracy, likelihood ratio, and DD prevalence. When the data were dichotomized into DD lesions (M1-M4.1) versus absence of DD (M0) lesions, the sensitivity and specificity of the borescope was 55% [95% credible interval (CrI) 40-71%] and 81% (95% CrI 75-88%). The sensitivity of trimming chute exams was 79% (95% CrI 68-88%), and specificity was 80% (95% CrI 71-89%). When the data were dichotomized into active lesions (M1, M2, M4.1) versus inactive lesions or absence of lesions (M3, M4, M0), the sensitivity and specificity of the borescope were, respectively, 32% (95% CrI 13-58%) and 91% (95% CrI 88-95%). The sensitivity and specificity of trimming chute exams were 91% (95% CrI 81-97%) and 81% (95% CrI 75-89%), respectively. In conclusion, it is possible to use the borescope in the milking parlor without cleaning the feet to monitor prevalence of DD lesions. However, an isolated borescope examination, especially for diagnosing active DD lesions, has low sensitivity for use as a surveillance method. For such use, the sensitivity could be improved by repeating the borescope exam on a regular basis.

Accuracy of leukocyte esterase test, endometrial cytology and vaginal discharge score for diagnosing postpartum reproductive tract health status in dairy cows at the moment of sampling, using a latent class model fit within a Bayesian framework.

The objectives of this retrospective study were: 1) to determine the sensitivity (Se) and specificity (Sp) of leukocyte esterase test (LE), endometrial cytology (CYTO) and vaginal discharge score (VDS) for diagnosis of reproductive tract diseases in dairy cows at the moment of sampling; 2) to assess the impact of different thresholds on test accuracy and misclassification costs; and 3) to quantify herd prevalence of reproductive tract diseases in dairy farms from Québec, Canada. Data from 2092 cows (39 herds) enrolled in two randomized control trials were included. Cows were examined at 35 (± 7) days in milk using LE, CYTO, and VDS to determine their reproductive tract health status. A latent class model assuming conditional dependence of CYTO and LE was fit within a Bayesian framework. Non-informative priors were used for the Se and Sp of LE, CYTO, and VDS, while prior information for disease prevalence was obtained from expert opinions (mode = 20%, 5th percentile = 10%). Posterior inferences (median and 95% Bayesian credible intervals; BCI) were obtained using the WinBUGS statistical freeware. An initial model was built using thresholds of ≥ 1 (small amount of leukocytes), of ≥ 6%, and of ≥ 3 (mucopurulent discharge) for the LE, CYTO, and VDS, respectively. Then, the impact on tests accuracy and misclassification costs of using different thresholds was explored. Optimal thresholds balancing the need for good antimicrobial stewardship and animal health considerations were proposed. The optimal thresholds obtained in the final model were: LE ≥ 2 (moderate amount of leukocytes), CYTO ≥ 6%, and VDS ≥ 2 (mucus with flecks of pus). In the final model, median (95% BCI) Se for LE, CYTO and VDS were 42.6% (38.8-47.0), 45.9% (41.9-50.7), and 64.2% (59.1-70.3), respectively. Median Sp was 90.9% (88.0-93.6) for LE, 92.2% (89.2-94.9) for CYTO and 96.6% (91.3-99.8) for VDS. Median within-herd prevalence of reproductive tract disease was estimated at 47.9% (39.0-56.7). At a threshold ≥ 2 (mucus with flecks of pus), VDS had the highest Se and Sp among the tests evaluated. The LE is an interesting diagnostic alternative for detecting reproductive tract disease in dairy cows. At a threshold ≥ 2 (moderate amount of leukocytes), LE Se and Sp were comparable to those of CYTO. This is the first study reporting the accuracy of LE, CYTO, and VDS for diagnosing reproductive tract diseases in dairy cows at the moment of sampling.

Reproductive management practices on dairy farms: The Canadian National Dairy Study 2015.

The objectives of this cross-sectional study were to characterize reproductive management practices on Canadian dairy farms and describe differences based on regional and demographic factors. A questionnaire was offered to all licensed Canadian dairy producers and included 189 questions regarding producer and farm background information, herd dynamics, biosecurity, disease prevalence, calf health, animal welfare, milking practices, reproduction, and internet use. Twenty-four questions were related to estrus detection, hormonal protocols for reproduction, insemination, and pregnancy diagnosis. A total of 1,373 producers responded to the survey, representing a response rate of 12.5%. Estrus detection practices in lactating cows were associated with herd size, barn type, region, organic production, breeding method, and age of respondent. The most commonly used estrus-detection method in cows was visual (51.0% of farms for first insemination; 45.5% for subsequent inseminations). Estrus detection for nulliparous heifers was associated with herd size, barn type, region, and breeding method, with visual detection also the most common method for heifers (71.3% of farms). Eighty percent of farms used strictly artificial insemination, 2.8% used natural service only, and 16.8% used a combination of artificial insemination and natural service. Breeding method was associated with herd size, barn type, region, and education level of the respondent. Pregnancy diagnosis method was associated with herd size, barn type, region, and organic production. Ultrasound was the most commonly used method of pregnancy diagnosis (used by 52.2% of farms). Sixty-nine percent of farms rechecked cows for pregnancy, and rectal palpation was the most commonly used method (employed by 48.7%). Reproductive management practices vary considerably among Canadian dairy farms and decisions are associated with farm-level factors, including region, herd size, and barn type, as well as producer-level factors, such as age, managerial role, and education level.

Algometer Precision for Quantifying Mechanical Nociceptive Threshold When Applied to the Udder of Lactating Dairy Cows.

Objectives of this study were to: (1) quantify the reliability of an algometer for measuring mechanical nociceptive thresholds when applied to the udder of dairy cows; and (2) evaluate whether covariates, such as cow characteristics or time of the day, would influence algometer measurements. This prospective study was performed in a university herd of 37 lactating cows during five consecutive days, involving two raters. Two types of measurement were obtained: one qualitative binary measure (i.e., reaction vs. no reaction) and one quantitative measure presented in kilograms (i.e., mechanical nociceptive threshold, MNT) for the cows that reacted. Kappa statistics were used to investigate test-retest and inter-rater reliability for the qualitative measure, while concordance correlation coefficient (CCC) and limits of agreement plot were used for the quantitative measure. Whether algometer measurements were influenced by several covariates (i.e., time of the day, level of milk production, days in milk, and parity) was then evaluated using logistic or linear regression models, depending on the outcome. The algometer was moderately reliable; there was moderate test-retest reliability (Kappa = 0.53; CCC = 0.58) and inter-rater reliability (Kappa = 0.42; CCC = 0.54). The MNT varied substantially as a function of time of the day and parity. This is the first study reporting reliability of a pressure algometer for quantifying MNT and investigating covariates possibly affecting this measurement when applied to the udder of dairy cows. It is concluded that the use of an algometer for quantifying MNT on the udder is only moderately repeatable and is influenced by extraneous covariates. Its usage in research setting to quantify changes in sensitivity at the udder level should, therefore, be considered very cautiously or it should be further developed.

Canadian National Dairy Study: Heifer calf management.

In the past decade, substantial changes have occurred in the way dairy heifer calves are managed. The objectives of this study, part of phase I of the 2015 Canadian National Dairy Study, were to examine heifer calf health and adoption of rearing practices, and to explore factors associated with different rearing strategies on Canadian dairy farms. The questionnaire was open to all licensed dairy producers in Canada and had a 12% response rate (n = 1,373). Fifty-one percent of respondents reported never allowing heifer calves to nurse their dam, and 17% always removed calves within 30 min of birth. Sixty-seven percent reported always feeding heifer calves 4 L of colostrum within 12 h of birth; 17% always fed colostrum between 2100 and 0400 h; 5% pasteurized all colostrum fed on farm. Seventy-seven percent of respondents reported calving and stillbirth information for 2014; the mean reported stillbirth rate was 4.9% (SD = 3.3). Forty percent housed calves in individual pens, 34% in group pens, 21% in individual hutches, 2% reported tethering calves, and 1% used group hutches. Of those who housed calves in groups, 59% reported a maximum group size of 3 to 10 calves, 31% reported a pair (2) of calves per pen or hutch, and 10% reported a group >10 calves. The maximum amount of milk offered to calves per day during the preweaned period was a mean of 8 L (SD = 3). Fifty percent of respondents reported mortality data for 2014; mean preweaning mortality was 6.4% (SD = 8.3), and postweaning mortality was 2.4% (SD = 4.4). Over 95% of producers reported disbudding practices; 86% used cautery, 11% used surgical amputation, and 9% used caustic paste. Twenty-eight percent reported disbudding at less than 3 wk of age, 60% at 3 to 8 wk, and 22% at 8 to 16 wk; 5% of respondents reported dehorning at more than 16 wk of age. Sixty-six percent of cautery users reported use of local anesthetic, 33% used sedation, and 25% used a nonsteroidal anti-inflammatory drug (NSAID). Multivariable regression models showed that the use of local anesthetic when disbudding calves was associated with social media activity (odds ratio = 2.3) and high-speed internet access (odds ratio = 2.0), whereas sedation was associated with geographic region, and NSAID use was associated with disbudding at more than 3 wk of age. Exploring heifer rearing management practices, including adoption of best practices, may help focus future education and extension efforts. Poor reporting of mortality data may reflect a lack of recordkeeping on farm.

Marginal structural Cox model to estimate the causal effect of clinical mastitis on Québec dairy cow culling risk.

Health disorders, such as milk fever, displaced abomasum, or retained placenta, as well as poor reproductive performance, are known risk factors for culling in dairy cows. Clinical mastitis (CM) is one of the most influential culling risk factors. However the culling decision could be based either on the disease status or on the current milk yield, milk production being a significant confounder when modelling dairy cow culling risk. But milk yield (and somatic cell count) are time-varying confounders, which are also affected by prior CM and therefore lie on the causal pathway between the exposure of interest, CM, and the outcome, culling. Including these time-varying confounders could result in biased estimates. A marginal structural model (MSM) is a statistical technique allowing estimation of the causal effect of a time-varying exposure in the presence of time-varying covariates without conditioning on these covariates. The objective of this paper is to estimate the causal effect on culling of CM occurring between calving and 120 days in milk, using MSM to control for such time-varying confounders affected by previous exposure. A retrospective longitudinal study was conducted on data from dairy herds in the Province of Québec, Canada, by extracting health information events from the dairy herd health management software used by most Québec dairy producers and their veterinarians. The data were extracted for all lactations starting between January 1st and December 31st, 2010. A total of 3952 heifers and 8724 cows from 261 herds met the inclusion criteria and were used in the analysis. The estimated CM causal hazard ratios were 1.96 [1.57-2.44] and 1.47 [1.28-1.69] for heifers and cows, respectively, and as long as causal assumptions hold. Our findings confirm that CM was a risk factor for culling, but with a reduced effect compared to previous studies, which did not properly control for the presence of time-dependent confounders such as milk yield and somatic cell count. Cows experienced a lower risk for CM, with milk production having more influence on culling risk in cows than heifers.

Culling from the herd's perspective-Exploring herd-level management factors and culling rates in Québec dairy herds.

The relationship between cows' health, reproductive performance or disorders and their longevity is well demonstrated in the literature. However these associations at the cow level might not hold true at the herd level, and herd-level variables can modify cow-level outcomes independently of the cows' characteristics. The interaction between cow-level and herd-level variables is a relevant issue for understanding the culling of dairy cows. However it requires the appropriate group-level variables to assess any contextual effect. Based on 10 years of health and production data, the objectives of this paper are:(a) to quantify the culling rates of dairy herds in Québec; (b) to determine the profiles of the herds based on herd-level factors, such as demographics, reproduction, production and health indicators, and whether these profiles can be related to herd culling rates for use as potential contextual variables in multilevel modelling of culling risk. A retrospective longitudinal study was conducted on data from dairy herds in Québec, Canada, by extracting health information events from the dairy herd health management software used by most Québec producers and their veterinarians. Data were extracted for all lactations taking place between January 1st, 2001 and December 31st, 2010. A total of 432,733 lactations from 156,409 cows out of 763 herds were available for analysis. Thirty cow-level variables were aggregated for each herd and years of follow-up, and their relationship was investigated by Multiple Factor Analysis (MFA). The overall annual culling rate was 32%, with a 95% confidence interval (CI) of [31.6%,32.5%]. The dairy sale rate by 60 days in milk (DIM) was 3.2% [2.8%,3.6%]. The annual culling rate within 60 DIM was 8.2% [7.9%,8.4%]. The explained variance for each axis from the MFA was very low: 14.8% for the first axis and 13.1% for the second. From the MFA results, we conclude there is no relationship between the groups of herd-level indicators, demonstrating the heterogeneity among herds for their demographics, reproduction and production performance, and health status. However, based on Principal Component Analysis (PCA), the profiles of herds could be determined according to specific, single, herd-level indicators independently. The relationships between culling rates and specific herd-level variables within factors were limited to livestock sales, proportion of first lactation cows, herd size, proportion of calvings occurring in the fall, longer calving intervals and reduced 21-day pregnancy rates, increased days to first service, average age at first calving, and reduced milk fever incidence. The indicators found could be considered as contextual variables in multilevel model-building strategies to investigate cow culling risk.

Culling from the actors' perspectives-Decision-making criteria for culling in Québec dairy herds enrolled in a veterinary preventive medicine program.

The series of events leading to the decision to cull a cow is complex, involving both individual-level and herd-level factors. While the decision is guided by financial returns, it is also influenced by social and psychological factors. Research studies on the motivational and behavioural aspects of farmers' decision utility are sparse, and nonexistent regarding culling expectations and its decision process. Our goal was to identify shared criteria on culling decisions held by dairy producers and farm advisers, with the help of the Q-methodology. Forty-one dairy producers and 42 advisers (17 veterinarians, 13 feed mill advisers, and 12 dairy herd improvement (DHI) advisers) undertook a Q-sort with 40 statements that represented a range of views about cow and herd health, production performance, management issues, and material factors that might impact their culling decision-making process. The sorts were analysed by-person using factor analysis and oblimin rotation. A single view on culling could be identified among dairy producers that can be extended to dairy farm advisers, who showed two variations of the same well-structured, uni-dimensional decision-making process. Udder health, milk production performance, and milk quota management were the key criteria for the culling decision. Farm management parameters (debts, amortization, employees, milking parlour capacity, herd size) did not play any role in the decision process. Three key differences were, however, identified between producers and the two types of advisers. One group of advisers followed the recommendations from mathematical models, where pregnancy is a major determinant of a cow's value. They assessed the cow in a more abstract way than did the other participants, still taking into account udder health and milk production, but adding economic considerations, like the availability of financial incentives and an evaluation of the post-partum health of the cow. Dairy producers were also more concerned about producing healthy and safe milk, which might reflect a different value given to dairy farming than by advisers. Very different degrees of importance were given to animal welfare by the three groups, which could represent different views on the attributed relationships between dairy farmers and their animals. Our findings suggest that dairy producers and their advisers hold a general common view regarding culling decision-making. However there are significant differences between producers and advisers, and among advisers. Understanding and managing these differences is important for assisting the change management processes required to increase farm profitability, and call for further investigation.

Contextual herd factors associated with cow culling risk in Québec dairy herds: A multilevel analysis.

Several health disorders, such as milk fever, displaced abomasum, and mastitis, as well as impaired reproductive performance, are known risk factors for the removal of affected cows from a dairy herd. While cow-level risk factors are well documented in the literature, herd-level associations have been less frequently investigated. The objective of this study was to investigate the effect of cow- and herd-level determinants on variations in culling risk in Québec dairy herds: whether herd influences a cow's culling risk. For this, we assessed the influence of herd membership on cow culling risk according to displaced abomasum, milk fever, and retained placenta. A retrospective longitudinal study was conducted on data from dairy herds in the Province of Québec, Canada, by extracting health information events from the dairy herd health management software used by most Québec dairy producers and their veterinarians. Data were extracted for all lactations starting between January 1st and December 31st, 2010. Using multilevel logistic regression, we analysed a total of 10,529 cows from 201 herds that met the inclusion criteria. Milk fever and displaced abomasum were demonstrated to increase the cow culling risk. A minor general herd effect was found for the culling risk (i.e. an intra-class correlation of 1.0% and median odds ratio [MOR] of 1.20). The proportion of first lactation cows was responsible for this significant, but weak herd effect on individual cow culling risk, after taking into account the cow-level factors. On the other hand, the herd's average milk production was a protective factor. The planning and management of forthcoming replacement animals has to be taken into consideration when assessing cow culling risks and herd culling rates.