Using dairy herd improvement records and clinical mastitis history to identify subclinical mastitis infections at dry-off

In this study, we studied infection dynamics across the dry period using test-day somatic cell count (SCC) data from 739 Holstein cows from 33 randomly selected commercial dairy herds in Flanders, all of which applied blanket dry-cow therapy at dry-off. First, we determined infection dynamics, combining the last testday SCC before dry-off and the first test-day SCC after calving. Next, we determined the effect of dry period infection dynamics, adjusting for the level of the second test-day SCC after calving, on the evolution of testday SCC and milk yield (MY) and on clinical mastitis and culling hazard in the subsequent lactation. Using an SCC threshold of 200,000 cells/mL, 12.6% of the cows considered healthy before dry-off acquired a new intramammary infection (IMI) across the dry period, whereas 66.9% of the cows considered infected before dry-off cured from IMI. Infection dynamics across the dry period significantly affect a cow's SCC, clinical mastitis risk, and culling hazard in the subsequent lactation. Cows with a new IMI, a cured IMI, or a chronic IMI across the dry period had higher test-day SCC than healthy cows, and their test-day SCC evolved differently over time. This was not the case for test-day milk yield, for which no association with infection dynamics was detected. Furthermore, cows with a second test-day SCC <200,000 cells/mL had a lower test-day SCC in the remainder of the lactation than cows with a second test-day SCC ≥200,000 cells/mL, but this association was modified by infection dynamics across the dry period. The lowest test-day SCC in the remainder of the lactation was observed for cows that remained healthy across the dry period combined with a low (<200,000 cells/mL) second test-day SCC. Cows that cured from an IMI present at dry-off and cows with a chronic IMI across the dry period were more likely to develop clinical mastitis (hazard ratio = 2.22 and 2.89; 95% confidence interval = 1.45-3.43 and 1.60-5.20, respectively), and chronic IMI cows were more likely to be culled (hazard ratio = 3.68; 95% confidence interval = 1.64-8.20) in the subsequent lactation compared with healthy cows. This was not true for cows that became infected across the dry period. This study underlines the importance of good udder health management during lactation to prevent IMI at dry-off rather than curing infected cows during the dry period to ensure optimal udder health in the subsequent lactation.

Section: Discussionmentioning

confidence: 92%

Infection dynamics across the dry period using Dairy Herd Improvement somatic cell count data and its effect on cow performance in the subsequent lactation

Lipkens

Piepers

Verbeke³

et al. 2019

“…Selecting cows for DCT with Petrifilm did not affect the risk of IMI at calving or the risk of a first case of CM in the first 120 d of lactation compared with BDCT (Cameron et al, 2014). The most feasible selection method, however, is based on monthly SCC, which has a reported sensitivity of 70% and specificity of 63% to identify quarters with IMI at drying off (Torres et al, 2008). In that study, the SCC cutoff level used was <200,000 cells/mL and no history of CM.…”

Section: Discussionmentioning

confidence: 90%

“…Decisionmaking can be based on bacteriological culture (Robinson et al, 1988;Browning et al, 1990), SCC, and CM history (Rindsig et al, 1978;Torres et al, 2008;Rajala-Schultz et al, 2011), the California Mastitis Test (Rindsig et al, 1978;Bhutto et al, 2012), and N-acetylβ-d-glucosaminidase (Hassan et al, 1999), with different accuracies in identification of infected cows. When used in herds with low bulk milk SCC (<250,000 cells/ mL) to diagnose IMI in cows with a low SCC (<200,000 cells/mL) before drying off, a Petrifilm-based (3M, Minneapolis, MN) on-farm culture system for SDCT performed well, with a sensitivity of 85% and specificity of 73% (Cameron et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…To correctly select cows for curative use of antimicrobials in DCT, IMI at drying off need to be identified. This identification can be based on different criteria, such as SCC, bacteriological culture, and CM history (Torres et al, 2008;Rajala-Schultz et al, 2011). Herdlevel parameters, such as bulk milk SCC can also be taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Effect of different scenarios for selective dry-cow therapy on udder health, antimicrobial usage, and economics

Scherpenzeel

Uijl

Schaik

et al. 2016

The goal of dry-cow therapy (DCT) is to reduce the prevalence of intramammary infections (IMI) by eliminating existing IMI at drying off and preventing new IMI from occurring during the dry period. Due to public health concerns, however, preventive use of antimicrobials has become questionable. In this study, we evaluated the effects of 8 scenarios for selecting animals for DCT, taking into account variation in parity and cow-level somatic cell count (SCC) at drying off. The aim of this study was to evaluate udder health, antimicrobial usage, and economics at the herd level when using different scenarios for selecting cows for DCT. To enable calculation and comparison of the effects of different scenarios to select cows for DCT in an "average" herd, we created an example herd, with a virtual herd size of 100 dairy cows to be calving during a year. Udder health, antimicrobial usage, and economics were evaluated during the dry period and the first 100 d in lactation, the period during which the greatest effect of DCT is expected. This leads to an estimated 13,551 cow-days at risk during a year in a 100-cow dairy herd. In addition to a blanket DCT (BDCT) scenario, we developed 7 scenarios to select cows for DCT based on SCC. The scenarios covered a range of possible approaches to select low-SCC cows for DCT, all based on cow-level SCC thresholds on the last milk recording before drying off. The incidence rate of clinical mastitis in the example herd varied from 11.6 to 14.5 cases of clinical mastitis per 10,000 cow-days at risk in the different scenarios, and the prevalence of subclinical mastitis varied from 38.8% in scenario 1 (BDCT) to 48.3% in scenario 8. Total antimicrobial usage for DCT and clinical mastitis treatment varied over the scenarios from 1.27 (scenario 8) to 3.15 animal daily dosages (BDCT), leading to a maximum reduction in antimicrobial usage of 60% for scenario 8 compared with BDCT. The total costs for each of the scenarios showed little variation, varying from €4,893 for scenario 5 to €5,383 for scenario 8. The effect of selective DCT compared with BDCT on udder health, antimicrobial usage, and economics is influenced by the SCC criteria used to select cows for DCT. Scenario 2 resulted in the lowest increases in clinical and subclinical mastitis compared with BDCT. The greatest reduction in antimicrobial usage was achieved under scenario 8. From an economic perspective, lowest costs were achieved with scenario 5. Drying off dairy cows with antimicrobials has an effect on udder health, antimicrobial usage, and economics.

“…The majority of studies evaluating SDCT and ITS have focused on the risk of IMI and clinical mastitis in the subsequent lactation, whereas published reports examining the effects on milk yield and SCC are sparse. A consistent theme in SDCT research is that the success of such a program depends on the ability to determine a cow's IMI status at the end of lactation so that the appropriate treatment can be applied (Huxley et al, 2002;Robert et al, 2008;Torres et al, 2008). A Petrifilm (3M Canada, London, Ontario)-based on-farm culture system has recently been validated for use in a SDCT program.…”

Section: Petrifilm-based Sdct Plus Itsmentioning

confidence: 99%

Evaluation of selective dry cow treatment following on-farm culture: Milk yield and somatic cell count in the subsequent lactation

Cameron

Keefe

Roy

et al. 2015

Compared with blanket dry cow therapy (DCT), the selective antimicrobial treatment of cows based upon on-farm culture results has the potential to reduce the amount of antimicrobials used in dairy production. The objective of the current study was to determine the effect of a Petrifilm (3M Canada, London, Ontario) on-farm culture-based selective DCT program on milk yield and somatic cell count (SCC) in the following lactation. A total of 729 low-SCC (<200,000 cells/mL) cows from 16 commercial dairy herds with a low bulk tank SCC (<250,000 cells/mL) were randomly assigned to receive either blanket DCT or Petrifilm-based selective DCT. Cows belonging to the blanket DCT group were infused with a commercial DCT product and an internal teat sealant (ITS) at drying off. Using composite milk samples collected on the day before drying off, cows in the selective DCT group were treated at drying off based on the results obtained by the Petrifilm on-farm culture system with DCT and ITS (Petrifilm culture positive) or ITS alone (Petrifilm culture negative). Milk test-day records for the following lactation were obtained from Dairy Herd Improvement for all cows enrolled in the trial. Repeated measures linear mixed models were used to assess the effect of study group (blanket or selective DCT) on test-day milk production and natural logarithm of SCC over the first 180 d of the subsequent lactation. According to the final multivariable models, when low-SCC cows were selectively treated with DCT at drying off based on results obtained using the Petrifilm on-farm culture system, no effect on milk production (least squares means for blanket DCT = 39.3 kg vs. selective DCT = 39.0 kg) or natural logarithm of SCC (least squares means for blanket DCT = 3.95 vs. selective DCT = 3.97) was observed in the subsequent lactation when compared with cows receiving blanket DCT. The results of this study indicate that selective DCT based on results obtained by the Petrifilm on-farm culture system enabled a reduction in the use of DCT without negatively affecting milk production and milk quality.