Udder health outcomes in Irish herds participating in cellcheck dry cow consults

The CellCheck Dry Cow Consult (DCC) was developed by the CellCheck Technical Working Group to enable farmers to engage with their nominated vet to develop farm-specific selective dry cow therapy (SDCT) plans, where appropriate. This study evaluated the effect of the DCC on farmer decision-making around dry cow therapy, and the udder health impact of implementing SDCT, in study herds over the 2019 and 2020 dry periods. The DCC was a 3-h consult, delivered and funded as part of the Targeted Advisory Service on Animal Health (TASAH). Herds that completed a DCC were invited to register for a Dry Cow Review the following year. The combined data set for analysis across both years comprised of 439 herds and 25,357 cows. Available herd size ranged from 25 to 800. The median SCC of cows dried off with teat sealant only was 47,000 cells/ml before drying off in 2019 and 48,000 cells/ml at first milk recording in 2020, and 43,000 cells/ml before drying off in 2020 and 39,000 cells/ml at first milking recording in 2021. Following both the 2019 and 2020 dry periods, cows tended to converge toward a similar median SCC early in the following lactation, irrespective of prior dry cow treatment strategy. The uptake of SDCT was greater in Review herds, with 21% of cows receiving teat sealant only in 2020, compared with 16.3% of cows in herds participating in a Consult for the first time in 2020. At an individual cow level, in both years dry period new infection rate (NIR) was approximately 2.7% higher for cows treated with teat sealant only, than for those treated with both dry cow antibiotic tubes and teat sealant, and 1.2% higher than cows treated with antibiotic only. Regardless of treatment, there was a significant association between increasing parity and the risk of a dry period new infection. Increasing herd size had a statistically significant effect on the risk of dry period new infection rates. At a herd level, there was no statistically significant increase in NIR when SDCT was used compared with herds where blanket dry cow therapy was used. While not without risk, SDCT can be successfully implemented in Irish herds; however, constant attention to hygiene and management is essential. Though there are challenges to face, facilitating continued farmer education and engagement with professional guidance will be important.

[Veterinary Herd Health Management and Selective Dry Cow Treatment in Germany - Results of a survey among farm veterinarians]

OBJECTIVE

The aim of the survey was to evaluate the development and implementation of Veterinary Herd Health Management (VHHM), as well as Selective Dry Cow Treatment (SDCT), in German veterinary practices and dairy farms. Furthermore, this survey set out to compare and contrast veterinary practitioners that utilize VHHM in relation to SDCT with those that do not.

MATERIAL AND METHODS

The survey (n=600) was distributed to veterinary livestock practitioners at 7 advanced training courses. Participation was voluntary and anonymous. Data analysis was carried out by means of descriptive statistics as well as by linear and logistic regression.

RESULTS

The response rate amounted to 39.3% (n=236). 54.2% (n=128) of the veterinarians reported that they conduct VHHM. Procedures for SDCT were used on farms overseen by 75% (n=177) of the vets. Different decision criteria applied at herd (81.6%, n=142) and at individual cow level (97.7%, n=172) respectively. A performance review of SDCT was carried out more frequently on farms of veterinarians that practice VHHM (66%, n=66) than those that do not (41%, n=28). An increase in the number of farms conducting VHHM was associated with an increase in the proportion of farms using SDCT. An increase of the probability of good udder health was associated with SDCT farms that also apply VHHM (OR: 1.025; p<0.05). The provision of consultation for problems arising during the dry period (OR: 3.639; p<0.05), the frequency of veterinarians addressing SDCT with farmers (OR: 1,595; p<0,05) and vice versa (OR: 1,538; p<0.05), as well as frequency of consultation for drying off management (OR: 1,608; p<0.05) had an positive impact on the likelihood of SDCT being implemented on a farm and whether this process was ultimately successful.

CONCLUSIONS

According to available data, both VHHM and SDCT are established parts of veterinary practice in bovine care. In practice, SDCT is partially conducted within the framework of a controlled procedure including a performance review. The implementation of VHHM has an effect on the number of farms performing SDCT as well as on udder health where VHHM and SDCT are combined on a farm. The range and frequency of consultation by veterinarians have a significant influence on a reduction of use of antibiotics by implementation of SDCT.

Selective dry-cow therapy can be implemented successfully in cows of all milk production levels

Antibiotic stewardship on dairy farms can be heightened through the implementation of selective dry-cow therapy (SDCT). However, some producers are concerned that this practice may be related to poor udder health outcomes in cows with high milk production at the time of dry-off. The objective of this study was to evaluate if the effect of culture-guided SDCT (Cult-SDCT) and algorithm-guided SDCT (Alg-SDCT) on dry-period intramammary infection (IMI) dynamics and postcalving udder health and performance [when compared with blanket dry-cow therapy (BDCT)] varied according to milk production level before dry-off. Data were compiled from clinical trials conducted in the United States and Canada that compared Cult-SDCT and Alg-SDCT to a positive control, i.e., BDCT. In those trials, cows were enrolled 1-2 d before dry-off, randomized to their dry-cow therapy strategy and followed until 120 d in milk of the subsequent lactation. The number of cows and quarters in the final data set were 1,485 and 5,097, respectively. Measured outcomes included quarter-level antibiotic use at dry-off, quarter-level IMI prevalence after calving, quarter-level dry-period IMI cure risk, quarter-level dry-period new IMI risk, cow-level clinical mastitis and removal from the herd during 1-120 d in milk, and somatic cell count and milk yield during 1-120 DIM. The primary objective of analysis was to investigate if the effect of Cult-SDCT and Alg-SDCT on these outcomes, when compared with BDCT, varied according to milk production level before dry-off. To do this, each cow was classified as having low, mid or high production, based on her milk yield tertile group at the most recent herd test before enrollment (low: <23.7 kg/d, mid: 23.7 to 30.4 kg/d, and high >30.4 kg/d). Multivariable generalized estimating equations were used to estimate risk differences and differences in means, and Cox regression was used to estimate hazard ratios. For Cult-SDCT, the proportion of quarters treated with dry-cow antibiotics within each milk production level were 40.7% (low), 41.7% (mid) and 47.2% (high). For Alg-SDCT, the proportions were 60.6% (low), 38.7% (mid), and 35.1% (high). Measures of udder health were not markedly different when comparing Cult-SDCT to BDCT and Alg-SDCT to BDCT. This was consistently observed in low, mid and high producing cows. In conclusion, the findings from this study indicate that Cult-SDCT and Alg-SDCT can be successfully implemented in cows of all milk production levels.

Effects of Selective Dry Cow Treatment on Intramammary Infection Risk after Calving, Cure Risk during the Dry Period, and Antibiotic Use at Drying-Off: A Systematic Review and Meta-Analysis of Current Literature (2000-2021)

The objectives of this paper were (i) to perform a systematic review of the literature over the last 21 yr and (ii) to evaluate the efficacy of selective dry cow treatment (SDCT) vs. blanket dry cow treatment (BDCT) in dairy cows regarding the risk of intramammary infection (IMI) after calving, new IMI risk after calving, cure risk during the dry period, and a reduction in antibiotic use at drying-off by meta-analysis. The systematic search was carried out using the databases PubMed, CAB Direct, and ScienceDirect. A meta-analytical assessment was performed for each outcome of interest using random-effects models, and the relative risk (RR) for IMI and cure or the pooled proportion for antibiotic use was calculated. The final number of included studies was n = 3 for IMI risk after calving and n = 5 for new IMI risk after calving, cure risk during the dry period, and antibiotic use. The RR levels for IMI (RR, 95% confidence interval [CI]: 1.02, 0.94-1.11; p = 0.592), new IMI (RR, 95% CI: 1.06, 0.94-1.20; p = 0.994), and cure (RR, 95% CI: 1.00, 0.97-1.02; p = 0.661) did not differ significantly between SDCT and BDCT. Substantial heterogeneity was observed between the trials regarding the pooled proportion of antibiotic use within the SDCT groups (I² = 97.7%; p < 0.001). This meta-analysis provides evidence that SDCT seems to be an adequate alternative to BDCT regarding udder health with a simultaneous reduction in antibiotic use. Limitations might arise because of the small number of studies included.

Comparison of Bovine Mammary Involution and Intramammary Infections Following Intramammary Treatment with Casein Hydrolysate and Other Conventional Treatments at Dry-Off

Simple Summary

Alternatives to antibiotic therapy for mastitis in dairy cattle are of interest to the dairy industry and society. Reduced use of antibiotics while maintaining or improving animal welfare is desirable. We studied the intramammary infusion of casein hydrolysate, alone or combined with standard dry cow treatment, at the beginning of the dry period before cows have their next calf. The effects on mammary involution and milk quality suggested that infusion of casein hydrolysate alone or combined with internal teat sealant may be an alternative to antibiotic dry cow therapy.

Abstract

Alternatives to routine antibiotic treatment of dairy cattle during the dry period before their next calving are of interest. This was a preliminary study of whether intramammary infusion of casein hydrolysate, administered alone or combined with standard dry treatment, accelerated the rate of mammary involution early in the dry period. Four treatments were studied in a split udder design. One udder half was assigned a treatment, and the contralateral half was administered dry cow treatment + internal teat sealant as a control. Treatments were casein hydrolysate, casein hydrolysate + dry cow treatment, casein hydrolysate + teat sealant and casein hydrolysate + dry cow treatment + teat sealant. Cows (n = 16) were blocked by a number of intramammary infections per udder half (0 or 1+) and randomized to treatments. Milk production was not different between control or treated udder halves post-calving. A generalized linear mixed model tested for differences between the treatment groups in the concentration of mammary involution indicators in milk: somatic cell count, bovine lactoferrin and bovine serum albumin. At 7 days, dry udder halves treated with casein hydrolysate had higher milk concentrations of lactoferrin than those treated with casein hydrolysate + dry cow treatment, casein hydrolysate + teat sealant and control. At 10 days dry, bovine serum albumin was higher in udder halves treated with casein hydrolysate than in those treated with casein hydrolysate + dry cow treatment, casein hydrolysate + dry cow treatment + teat sealant and control. Post-calving, casein hydrolysate-treated udder halves produced 51% of total milk, unchanged from before dry-off. There were seven total intramammary infections entering the dry period, all caused by coagulase-negative staphylococci. Cure rates (3/7, 43%) were not different among all treatments and control, partly because of the small sample size. Intramammary infusion of casein hydrolysate at the end of lactation may be an alternative or possible adjunct to antibiotic dry cow therapy.

Comparing Blanket vs. Selective Dry Cow Treatment Approaches for Elimination and Prevention of Intramammary Infections During the Dry Period: A Systematic Review and Meta-Analysis

A systematic review and a series of meta-analyses were conducted to investigate the efficacy of selective dry cow antimicrobial treatment (SDCT) (in which only infected quarters/cows were treated with an antimicrobial) compared with blanket dry cow treatment (BDCT) (all quarters/all cows received an antimicrobial, regardless of their infection status). A full detailed protocol was published before initiating this review. Studies reporting on the (1) proportion of untreated quarters or cows when using SDCT, (2) intramammary infection (IMI) incidence risk over the dry period, (3) IMI elimination risk, (4) post-calving IMI prevalence, (5) early lactation clinical mastitis incidence, or (6) subsequent lactation milk yield and somatic cell counts were considered eligible. Thirteen articles representing 12 controlled trials, whether randomized or not, were available for analyses. SDCT reduced the use of antimicrobials at dry off by 66% (95% CI: 49-80). There was no difference in the elimination of existing IMI at dry off, between SDCT and BDCT. Meta-regression showed that the risk of IMI incidence during the dry period, IMI risk at calving, early lactation clinical mastitis risk, and early lactation milk yield and somatic cell counts did not differ between SDCT and BDCT as long as an internal teat sealant (65% bismuth subnitrate) was administered to untreated healthy quarters/cows at dry off. For trials not using internal teat sealants, SDCT resulted in higher risk than BDCT of acquiring a new IMI during the dry period and of harboring an IMI at calving. Lines of evidence strongly support that SDCT would reduce the use of antimicrobials at dry off, without any detrimental effect on udder health or milk production during the 1st months of the subsequent lactation, if, and only if, internal teat sealants are used for healthy, untreated quarters/cows.

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.

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.