Replacing cows on a dairy is a major cost of operation. There is a need for the industry to adopt a more standardized approach to reporting the rate at which cows exit from the dairy, and to reporting the reasons why cows are replaced and their destination as they exit the dairy. Herd turnover rate is recommended as the preferred term for characterizing the cows exiting a dairy, in preference to herd replacement rate, culling rate, or percent exiting, all of which have served as synonyms. Herd turnover rate should be calculated as the number of cows that exit in a defined period divided by the animal time at risk for the population being characterized. The terms voluntary and involuntary culling suffer from problems of definition and their use should be discouraged. Destination should be recorded for all cows that exit the dairy and opportunities to record one or more reasons for exiting should be provided by management systems. Comparing reported reasons between dairies requires considerable caution because of differences in case definitions and recording methods. Relying upon culling records to monitor disease has been and will always be an ineffective management strategy. Dairies are encouraged to record and monitor disease events and reproductive performance and use this information as the basis for management efforts aimed at reducing the need to replace cows.

The objectives of this study were to determine the effect of infusion with an internal teat seal at dry off, when used as an adjunct to long-acting antibiotic infusion at dry off, on the risk for acquiring a new intramammary infection (IMI) during the dry period, prevalence of IMI and linear score (LS) after calving, and risk for experiencing a clinical mastitis event between dry off and 60 DIM. A total of 437 cows from 2 dairy herds, with no clinical mastitis and 4 functional quarters, were enrolled at dry off. Prior to the final milking, all quarters were sampled for bacteriological culture and SCC analysis. After milking, all 4 quarters were infused with a commercially available long-acting dry cow antibiotic. Two contralateral quarters were then infused with an internal teat seal (Orbeseal, Pfizer Animal Health, New York). Following calving the teat seal was stripped out at first milking. Duplicate milk samples were collected between 1 to 3 DIM and again between 6 to 8 DIM for culture and SCC analysis. Quarters treated with Orbeseal had significantly lower prevalence of IMI at 1 to 3 DIM (tx = 22.8%, control = 29.1%), had significantly fewer quarters that acquired a new IMI between dry off and 1 to 3 DIM (tx = 20.2%, control = 25.4%), and had significantly fewer quarters affected by a clinical mastitis event between dry off and 60 DIM (tx = 5.9%, control = 8.0%). Multivariable analysis showed a significant effect of treatment, with treated quarters being 30% less likely to develop a new IMI between dry off and 1 to 3 DIM, 31% less likely to have an IMI present at 1 to 3 DIM, 33% less likely to experience a clinical mastitis event between dry off and 60 DIM, and having significantly lower linear score measures at 1 to 3 DIM and 6 to 8 DIM, compared with control quarters.

The objectives of this study were to identify control points for bacterial contamination of bovine colostrum during the harvesting and feeding processes, and to describe the effects of refrigeration and use of potassium sorbate preservative on bacteria counts in stored fresh colostrum. For objective 1, first-milking colostrum samples were collected aseptically directly from the mammary glands of 39 cows, from the milking bucket, and from the esophageal feeder tube. For objective 2, 15-mL aliquots of colostrum were collected from the milking bucket and allocated to 1 of 4 treatment groups: 1) refrigeration, 2) ambient temperature, 3) refrigeration with potassium sorbate preservative, and 4) ambient temperature with potassium sorbate preservative. Subsamples from each treatment group were collected after 24, 48, and 96 h of storage. All samples underwent bacteriological culture for total plate count and coliform count. Bacteria counts were generally low or zero in colostrum collected directly from the gland [mean (SD) log10 cfu/mL(udder) = 1.44 (1.45)]. However, significant bacterial contamination occurred during the harvest process [mean (SD) log10 cfu/mL(bucket) = 4.99 (1.95)]. No additional bacterial contamination occurred between the bucket and the esophageal feeder tube. Storing colostrum at warm ambient temperatures resulted in the most rapid increase in bacteria counts, followed by intermediate rates of growth in nonpreserved refrigerated samples or preserved samples stored at ambient temperature. The most effective treatment studied was the use of potassium sorbate preservative in refrigerated samples, for which total plate count and total coliform counts dropped significantly and then remained constant during the 96-h storage period.

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.

The objective was to evaluate the performance of 3 cowside diagnostic tests for detection of subclinical ketosis, defined as a serum beta-hydroxybutyrate (BHBA) concentration >or=1400 micromol/L. On 16 d over a 5-mo period, samples of serum, milk, and urine were collected on a large dairy facility from cows of all parities between 2 and 15 DIM. The sample proportion of subclinical ketosis was 7.6% (n = 859 samples from 545 cows). The KetoCheck powder (Great States Animal Health, St. Joseph, MO) detecting acetoacetate in milk samples was very specific (99%) but poorly sensitive (41%). Respective sensitivities and specificities of the Ketostix strip detecting acetoacetate in urine samples (Bayer Corporation, Elkhart, IN) were 78 and 96% with a cut-off point of "small", or 49 and 99% with a cut-off of "moderate." The KetoTest strip (Sanwa Kagaku Kenkyusho Co. Ltd., Nagoya, Japan) using milk samples had a sensitivity and specificity of 73 and 96% with a cut-off of 100 micromol of BHBA/L or 27 and 99% with a cut-off of 200 micromol of BHBA/L. On average, use of the Ketostix at the "small" cut-off point or the KetoTest at 100 micromol/L would result in no more than 3 or 4 false positives per 100 cows screened, with prevalence levels ranging from 5 to 30%, whereas the number of false negatives would range from one false negative at 5% prevalence to 7 or 8 false negatives at 30% prevalence. Either the Ketostix or KetoTest strips would provide acceptable results for screening individual cows on commercial dairies to detect subclinical ketosis. Over this prevalence range, the KetoCheck powder test would have limited application as a screening test. Despite only one false positive per 100 animals screened, false negatives resulting from screening with the KetoCheck test would be too frequent, ranging from 3 false negatives at 5% prevalence to 18 at 30% prevalence in a population of 100 tested cows. Finally, given their relative imprecision, use of any of these individual cowside tests to estimate herd prevalence must be done cautiously, especially when only a small number of animals are sampled.