The objectives were to evaluate the effects of elevated pre- and postpartum nonesterified fatty acids (NEFA) and beta-hydroxybutyrate (BHBA) concentrations during the transition period on reproductive performance and milk production in dairy cattle. In a prospective cohort study of 91 freestall, total mixed ration-fed herds in the northeastern United States, blood samples were collected from approximately 15 prepartum and 15 different postpartum transition animals in each herd. All samples were stratified based on pre- or postpartum status at the time of sample collection, and 2,259 and 2,290 animals were used to evaluate reproductive and milk production performance, respectively. Reproductive performance was assessed by time to conception within 70 d post-voluntary waiting period (VWP) and milk production was assessed using mature-equivalent 305-d (ME305) milk yield estimated at 120 d in milk. While controlling for body condition score (BCS), calving season, median ME305 milk production, and parity, NEFA and BHBA concentrations were evaluated with time to event analysis to investigate reproductive performance. These same predictor variables were used to determine the effects of elevated NEFA and BHBA concentrations on ME305 milk yield with herd as a random effect. Heifers and cows were grouped in the final analyses if the results between groups were similar. In all animals sampled prepartum, the risk of pregnancy within 70 d post-VWP was reduced by 19% when NEFA concentrations were >or=0.27 mEq/L. In all animals sampled postpartum, those with NEFA concentrations >or=0.72 mEq/L had a 16% decrease in risk of pregnancy and those with BHBA concentrations >or=10mg/dL had a 13% decrease in risk. In cows and heifers, ME305 milk yield was decreased by 683 kg when prepartum NEFA concentrations were >or=0.33 mEq/L. In heifers sampled postpartum, ME305 milk yield was increased by 488 kg when NEFA concentrations were >or=0.57 mEq/L and increased by 403 kg when BHBA concentrations were >or=9 mg/dL. In cows sampled postpartum, ME305 milk yield was decreased by 647 kg when NEFA concentrations were >or=0.72 mEq/L and decreased by 393 kg when BHBA concentrations were >or=10mg/dL. With the exception of milk production in heifers, this study indicates that increased concentrations of serum NEFA and BHBA had a detrimental effect on reproductive performance and milk production.

BackgroundThoracic ultrasonography (US) and bronchoalveolar lavage fluid (BALF) analysis are antemortem methods used to identify the lung lesions associated with bovine respiratory disease (BRD). Accuracy of US and the cell distributions in BALF have not been characterized in calves with subclinical disease.ObjectivesTo evaluate the accuracy of US and BALF and describe BALF characteristics in calves with subclinical lung lesions.AnimalsTwenty‐five Holstein calves, 1–12 weeks old.MethodsIn this prospective study, calves with low respiratory scores underwent US, BALF and postmortem examination (normal US, n = 5; comet‐tails, n = 5; consolidation, n = 15). Bronchoalveolar lavage fluid was collected and analyzed for total and differential cell counts. Lung lesions were assessed by gross and histopathologic examination. Data were analyzed using nonparametric methods and relative risk analysis. The accuracy of US and BALF were estimated relative to postmortem examination.ResultsThe sensitivity and specificity of US for detecting lung lesions was 94% (95% CI, 69–100%) and 100% (95% CI, 64–100%), respectively. A cut‐point of ≥4% BALF neutrophils was associated with the highest BALF sensitivity and specificity, 81% (95% CI, 56–94%) and 75% (95% CI, 36–95%). The presence of consolidation on US increased the risk of having a BALF neutrophil proportion ≥4% (RR, 3.9; 95% CI, 1.13–13.45; P = .003).Conclusions and Clinical ImportanceUltrasonography accurately detects lung lesions in calves with subclinical disease. Clinicians should use a cut‐point of ≥4% BALF neutrophils to diagnose subclinical respiratory disease.

An algorithm using only computer-based records to guide selective dry-cow therapy was evaluated at a New York State dairy farm via a randomized field trial. DairyComp 305 (Valley Ag Software, Tulare, CA) and Dairy Herd Improvement Association test-day data were used to identify cows as low risk (cows that might not benefit from dry-cow antibiotics) or high risk (cows that will likely benefit). Low-risk cows were those that had all of the following: somatic cell count (SCC) ≤200,000 cells/mL at last test, an average SCC ≤200,000 cells/mL over the last 3 tests, no signs of clinical mastitis at dry-off, and no more than 1 clinical mastitis event in the current lactation. Low-risk cows were randomly assigned to receive intramammary antibiotics and external teat sealant (ABXTS) or external teat sealant only (TS) at dry-off. Using pre-dry-off and postcalving quarter-level culture results, low-risk quarters were assessed for microbiological cure risk and new infection risk. Groups were also assessed for differences in first-test milk yield and linear scores, individual milk weights for the first 30 d, and culling and mastitis events before 30 d in milk. A total of 304 cows and 1,040 quarters in the ABXTS group and 307 cows and 1,058 quarters in the TS group were enrolled. Among cows to be dried, the proportion of cows that met low-risk criteria was 64% (n = 611/953). Of cultures eligible for bacteriological cure analysis (n = 171), 93% of ABXTS cured, whereas 88% of TS cured. Of the non-cures, 95% were contributed by the minor pathogens coagulase-negative staphylococci (n = 19/20). These organisms also accounted for 57.5% of new infections (n = 77/134). We found no statistical differences between treatment groups for new infection risk (TS = 7.3% quarters experiencing new infections; ABXTS = 5.5%), milk production (ABXTS = 40.5 kg; TS = 41.2 kg), linear scores (ABXTS = 2.5; TS = 2.7), culling events (ABXTS, n = 18; TS, n = 15), or clinical mastitis events (ABXTS, n = 9; TS, n = 5). Results suggest that the algorithm used decreased dry-cow antibiotic use by approximately 60% without adversely affecting production or health outcomes.