A randomized controlled trial to study the effects of an automated premilking stimulation system on milking performance, teat tissue condition, and udder health in Holstein dairy cows.

The objectives were to examine the effect of an automated premilking stimulation (APS) by means of a high pulsation frequency (300 cycles/min) without a reduction of the vacuum in the pulsation chamber or claw piece on (1) milking performance, (2) teat tissue condition, and (3) udder health in dairy cows. In a randomized controlled field study, Holstein cows (n = 427) from 1 commercial dairy farm with a milking schedule of 3 times per day were assigned to treatment and control groups over a 90-d period. Treatments consisted of a maximum of 80 s (APS80) or 99 s (APS99) of mechanical stimulation at a pulsation rate of 300 pulses per minute and a ratio of 25:75 (no reduction of the pulsation chamber or milking vacuum). Cows in the control group (CON) received traditional premilking stimulation by means of manual forestripping for 8 s. Milking characteristics were documented with on-farm milk meters. Short- and long-term changes in teat tissue condition induced by machine milking were assessed visually on a weekly basis. Composite milk samples were analyzed once per month to determine somatic cell count. Generalized linear mixed models were used to study the effect of the treatment on the outcome variables. We observed no meaningful differences in milk yield or milking unit-on time. Least squares means and their 95% confidence intervals (95% CI) for cows in the APS80, APS99, and CON groups were 13.5 (13.1-14.0), 13.2 (12.8-13.7), and 13.2 (12.8-13.7) kg for milk yield and 222 (213-231), 219 (210-228), and 223 (214-232) s for milking unit-on time, respectively. The effect of treatment on bimodality was modified by milk yield such that the odds of bimodality increased in the treatment groups with increasing milk yield. Compared with cows in the CON group, the odds ratios (95% CI) of bimodality were 1.08 (0.62-1.89) in the APS80 group and 0.89 (0.55-1.42) in the APS99 group at a milk yield of 11 kg and 2.0 (1.24-3.22) in the APS80 group and 2.08 (1.29-3.35) in the APS99 group at a milk yield of 16 kg. We observed differences in short- and long-term changes in teat tissue condition between the treatment and control groups. Compared with cows in the CON group, the odds (95% CI) of short-term changes were 1.87 (1.35-2.58) for the APS80 group and 1.49 (1.08-2.07) for the APS99 group, and the odds of long-term changes were 1.52 (1.24-1.85) for cows in the APS80 group and 1.59 (1.31-1.94) for cows in the APS99 group. The least squares means (95% CI) for somatic cell counts (log10-transformed) were 4.74 (4.68-4.81) for the APS80 group, 4.77 (4.71-4.83) for the APS99 group, and 4.79 (4.73-4.86) for the CON group. We conclude that the APS system tested here had no negative effects on milk yield or milking unit-on time. However, differences in bimodality and teat tissue condition suggest that the APS system did not provide sufficient stimulation to facilitate a gentle milk harvest and adversely affects teat tissue condition.

Multivariable time series classification for clinical mastitis detection and prediction in automated milking systems.

In this study, we developed a machine learning framework to detect clinical mastitis (CM) at the current milking (i.e., the same milking) and predict CM at the next milking (i.e., one milking before CM occurrence) at the quarter level. Time series quarter-level milking data were extracted from an automated milking system (AMS). For both CM detection and prediction, the best classification performance was obtained from the decision tree-based ensemble models. Moreover, applying models on a data set containing data from the current milking and past 9 milkings before the current milking showed the best accuracy for detecting CM; modeling with a data set containing data from the current milking and past 7 milkings before the current milking yielded the best results for predicting CM. The models combined with oversampling methods resulted in specificity of 95 and 93% for CM detection and prediction, respectively, with the same sensitivity (82%) for both scenarios; when lowering specificity to 80 to 83%, undersampling techniques facilitated models to increase sensitivity to 95%. We propose a feasible machine learning framework to identify CM in a timely manner using imbalanced data from an AMS, which could provide useful information for farmers to manage the negative effects of CM.

A randomized controlled trial assessing the effect of intermittent and abrupt cessation of milking to end lactation on the well-being and intramammary infection risk of dairy cows.

The objectives were to compare the effects of an intermittent milking schedule with a thrice daily milking schedule during the final week of lactation on the well-being, udder health, milk production, and risk of culling of dairy cows. We hypothesized that cows subjected to an intermittent milking schedule would experience less udder engorgement and pain, lower concentrations of fecal glucocorticoid metabolites (11,17-dioxoandrostanes; 11,17-DOA concentration) after dry-off, lower risk of an intramammary infection during the dry period, higher milk production and lower somatic cell count in the subsequent lactation, and lower culling risk compared with herd mates milked 3 times daily and dried off by abrupt cessation. In a randomized controlled field study, Holstein cows (n = 398) with a thrice daily milking schedule were assigned to treatment and control groups. The treatment consisted of an intermittent milking schedule for 7 d before dry-off (gradual cessation of milking, GRAD). Gradual-cessation cows were milked once daily until the day of dry-off, whereas cows in the control group (abrupt cessation of milking, APT) were milked 3 times daily until the day of dry-off. Udder firmness and pain responses of the udder 3 d after dry-off, as well as the percentage change in fecal 11,17-DOA concentration (3 d after dry-off compared with the dry-off day), were used to assess the well-being of the animals. Compared with cows in the GRAD group, the odds [95% confidence interval (CI)] of udder firmness were 1.55 (0.99-2.42) for cows in the APT group, and the odds of a pain response were 1.48 (0.89-2.44) for cows in the APT group. The least squares means (95% CI) of the percentage change in 11,17-DOA concentration were 129.3% (111.1-150.4) for the APT group and 113.6% (97.5-132.4) for the GRAD group. Quarter-level culture results from the periods before dry-off and after calving were compared, to assess the likelihoods of microbiological cure and new infection. Cows in the APT group had lower odds of a new intramammary infection in the dry period [odds ratio, 95% CI: 0.63 (0.37-1.05)], whereas we observed no meaningful differences in the microbiological cure likelihood among groups. The least squares means (95% CI) for somatic cell counts (log10-transformed) were 4.9 (4.8-5.0) in the APT group and 4.9 (4.8-5.0) in the GRAD group. The odds (95% CI) of clinical mastitis in the first 30 d postcalving were 1.32 (0.53-3.30) in the APT group compared with the GRAD group. We observed no meaningful differences in milk production at the first test date postcalving or the culling risk among groups. We conclude that the gradual-cessation protocol tested herein failed to significantly improve animal well-being, udder health, milk production, and survival in the tested study cohort. However, the observed differences in udder firmness, as well as the numerical differences in udder pain and the percentage change in fecal 11,17-DOA concentrations suggest that this line of research may be useful. Future research is needed to develop drying-off strategies that are appropriate for lowering milk production at the end of the lactation and improve animal well-being without compromising udder health.

Transition cow nutrition and management strategies of dairy herds in the northeastern United States: Part III-Associations of management and dietary factors with analytes, health, milk yield, and reproduction.

The objective was to evaluate relationships between putative periparturient management and dietary factors at the pen and herd levels with metabolic- and inflammation-related analytes, health disorders, milk yield, and reproductive performance. Multiparous and primiparous cows from 72 farms in the northeastern United States were enrolled in a prospective cohort study. Farms were visited 3 times during the prepartum and postpartum periods: during the far-off dry, close-up dry, and fresh periods. Pen measurements were taken at each visit for the pens where cows sampled were housed, and particle size was determined for the total mixed ration for the pen. A survey was used to acquire data on herd-level management variables. Blood samples were collected from the same 11 to 24 cows per farm during the close-up and fresh period visits. Whole blood was analyzed for postpartum ß-hydroxybutyrate (BHB) concentrations, and plasma was analyzed for prepartum and postpartum nonesterified fatty acids (NEFA) and postpartum haptoglobin (Hp) concentrations. Health event, milk yield, and reproductive records were acquired through the records management software program used on the farm. For the pen-level analysis, primiparous and multiparous cows were analyzed separately. For the pen- and herd-level analysis, a simple linear regression was conducted on all possible explanatory variables. Variables were included in the full multivariable general linear model if P < 0.20, and a manual backward stepwise elimination process ensued until all variables had P < 0.10. Our results indicate that pen- and herd-level management factors are associated with blood biomarkers, health, milk yield, and reproductive performance. For the prepartum period, our results support increasing the proportion of particles on the 19-mm sieve of the Penn State Particle Separator, optimizing bunk space, and not overfeeding metabolizable energy (ME), to decrease the prevalence of elevated postpartum NEFA, BHB, and Hp concentrations, decrease disorder incidence, maximize milk yield, and improve pregnancy risk to first service. For the fresh period, our results generally support optimizing bunk space, avoiding commingling, increasing feeding frequency, avoiding high physically effective undigested neutral detergent fiber (NDF) after 240 h of in vitro fermentation and high total fermentable carbohydrate diets while optimizing the inclusion of forage NDF, and ensuring adequate diet ME and metabolizable protein to reduce the prevalence of elevated postpartum NEFA, BHB, and Hp concentrations, minimize disorder incidence, maximize milk yield, and improve pregnancy risk to first service. At the herd level, our results generally support not vaccinating in the calving pen, minimizing the number of prepartum and postpartum pen moves, and avoiding long stays in the calving pen after parturition to reduce the prevalence of elevated biomarker concentrations, decrease disorder incidence, increase milk yield, and improve reproductive performance.

Associations of a liver health index with health, milk yield, and reproductive performance in dairy herds in the northeastern United States.

The objective was to evaluate a liver health index (LHI) by evaluating its association with negative health events, milk yield, and risk of pregnancy within 150 d in milk (DIM). In a retrospective cohort study, an LHI was calculated based on plasma albumin, cholesterol, and bilirubin concentrations for 265 primiparous and 611 multiparous cows 3 to 12 DIM enrolled across 72 farms in the northeastern United States. Mixed effects linear regression models were used to evaluate if (1) metritis (MET), (2) displaced abomasum (DA), (3) clinical ketosis (CK), (4) one or more of the 3 disorders (MET, DA, or CK), (5) 2 or more of the 3 disorders (MET, DA, or CK), or (6) culling within 30 DIM was associated with LHI. Mixed effects linear regression models were used to evaluate if LHI was associated with 305-d mature equivalent milk at the fourth test day (ME305; mean ± standard deviation: 114 ± 13 DIM) and a Cox proportional hazards model was used to evaluate if LHI was associated with pregnancy within 150 DIM. Cows that were diagnosed with MET, DA, CK, one or more of the disorders, 2 or more of the disorders, or were culled within 30 DIM had a lower LHI than cows that were not diagnosed with a disorder or culled. A 1-unit increase in LHI was associated with a 154 ± 38 kg increase in ME305 and a 8% increased risk of pregnancy within 150 DIM [hazard ratio (95% confidence interval): 1.08 (1.03 to 1.14)] for multiparous cows; however, we did not identify a relationship between LHI and ME305 or pregnancy within 150 DIM for primiparous cows. These results suggest that the LHI is associated with health, milk yield, and pregnancy within 150 DIM for multiparous cows and health for primiparous cows; therefore, the LHI can be used as a tool to evaluate transition cow success.

Transition cow nutrition and management strategies of dairy herds in the northeastern United States: Part I-Herd description and performance characteristics.

Our objective was to describe management and herd characteristics of the transition period on freestall dairy herds in the northeastern United States using an on-farm survey and prospective cohort design. Enrolled herds (n = 72) had a median of 900 milking cows (range: 345-2,900) and a rolling herd average of 12,674 kg (standard deviation ± 1,220 kg), and 87.2% (n = 82/94) of fresh pens were milked at least 3×/d. The prevalence of herds with ≥15% of sampled cows with elevated concentrations of nonesterified fatty acids prepartum (≥0.27 mmol/L, 2-14 d before parturition) and postpartum [primiparous: ≥0.60 mmol/L, multiparous: ≥0.70 mmol/L, 3-14 d in milk (DIM)], ß-hydroxybutyrate postpartum (≥1.2 mmol/L, 3-14 DIM), and haptoglobin postpartum (≥1 g/L, 0-12 DIM) was 51%, 51%, 51%, and 57%, respectively. In most herds, cows were moved to a calving pen when showing signs of labor (73.6%; n = 53/72) instead of 0 to 3 d before expected calving (26.4%, n = 19/72). Cows remained in the calving or maternity pen for a median (range) time of 2 (0-24) h after parturition before moving to the next pen. Primiparous cows remained in the first pen moved to after parturition for a longer period than multiparous cows [median (range) days: 12 (1.5-25) vs. 6 (1.5-22)]. Approximately 20% of herds had routine vaccinations administered in the maternity or calving pen, first pen after parturition, or both. Almost all herds (n = 69/72) performed fresh cow health checks; however, only 53% (n = 38/72) locked up all fresh cows daily. More herds housed primiparous and multiparous cows in separate pens during the far-off dry (65.3%; n = 47/72) and high-lactation (81.9%; n = 59/72) periods compared with the close-up dry (31.9%; n = 23/72) and fresh periods (27.8%; n = 20/72). At least half of the pens observed during the far-off dry, close-up dry, and fresh periods had a stocking density <100%. Approximately one-third of pens observed during the far-off dry period had feed pushed up ≤4×/d compared with approximately 15 to 20% of pens observed during the close-up dry, fresh, and high-lactation periods. More than half of the total mixed ration samples acquired from the far-off and close-up dry period visits had greater than the recommended proportion of particles in the 19-mm screen of the Penn State Particle Separator. The results of this observational study illustrated the range of management practices used in freestall herds in this region and lay the groundwork for future hypothesis-driven studies using this sampled population.

Transition cow nutrition and management strategies of dairy herds in the northeastern United States: Part II-Associations of metabolic- and inflammation-related analytes with health, milk yield, and reproduction.

The objectives were as follows: (1) establish cow-level thresholds for prepartum nonesterified fatty acids (NEFA) and postpartum NEFA, ß-hydroxybutyrate (BHB), and haptoglobin (Hp) concentrations associated with negative health events; (2) evaluate cow-level associations between biomarkers and 305-d mature equivalent milk at the fourth test day (ME305) and reproductive performance; and (3) identify herd-alarm levels (proportion of cows sampled above the critical threshold) for biomarkers that are associated with herd-level changes in disorder incidence (displaced abomasum and clinical ketosis), reproductive performance, and ME305. In a prospective cohort study, 1,473 cows from 72 farms were enrolled from the northeastern United States. Blood samples were collected from the same 11 to 24 cows per herd during the late-prepartum and early-postpartum periods. Whole blood was analyzed for postpartum BHB concentrations; plasma was analyzed for prepartum and postpartum NEFA and postpartum Hp concentrations. Critical thresholds for the biomarkers associated with health events for all cows were established using a receiver operating characteristic curve analysis. Poisson, linear mixed effects, and Cox proportional hazards models investigated the association of the biomarkers with health and performance. The prepartum NEFA and Hp threshold associated with culling was ≥0.17 mmol/L and 0.45 g/L, respectively. The postpartum NEFA and BHB thresholds associated with diagnosis of metritis, displaced abomasum, or clinical ketosis were ≥0.46 mmol/L and ≥0.9 mmol/L, respectively. Multiparous cows with prepartum NEFA concentration ≥0.17 mmol/L produced 479 kg less ME305. Multiparous and primiparous cows with postpartum NEFA concentration ≥0.46 mmol/L produced 280 kg less and 446 kg more ME305, respectively. Cows with BHB concentration ≥0.9 and ≥1.1 mmol/L produced 552 kg more ME305 and had a 20% decreased risk of pregnancy within 150 d in milk, respectively; however, multiparous cows with BHB concentration ≥1.5 mmol/L produced 376 kg less ME305. Cows with Hp concentration ≥0.45 g/L produced 492 kg less ME305 and had 28% decreased risk of pregnancy within 150 DIM. Cows with Hp concentration ≥0.45 g/L had 19% decreased pregnancy risk to first service (PRFS). Herds above the herd-alarm levels for prepartum NEFA had a 6.0-percentage unit increase in disorder incidence and a 6.0-percentage unit decrease in 21-d pregnancy rate (PR) for multiparous cows, a 3.9-percentage unit increase in PR and a 5.8-percentage unit increase in the probability of pregnancy for primiparous cows. Herds above the herd-alarm levels for postpartum NEFA had a 5.8- and 4.2-percentage unit increase in disorder incidence for multiparous and primiparous cows, respectively, a 789 kg decrease in ME305 for multiparous cows, and a 6.8- and 6.3-percentage unit decrease and increase in PR and PRFS for multiparous cows, respectively. Herds above the herd-alarm levels for BHB had an 8.5-percentage unit increase in disorder incidence, a 332 and 229 kg increase in ME305 for primiparous and multiparous cows, respectively, and a 3.2-, 5.2-, and 7.0-percentage unit decrease in PR, probability of pregnancy, and PRFS, respectively. Herds above the herd-alarm levels for postpartum Hp had a 5.3-percentage unit increase in disorder incidence. At the cow level and herd level, elevated biomarker concentrations were associated with an increased disorder risk and varied performance responses.

Effect of passive antibodies derived from rotavirus-like particles on neonatal calf diarrhea caused by rotavirus in an oral challenge model.

Our objective was to evaluate the efficacy of bovine rotavirus antigen-specific passive antibody for reducing the duration of diarrhea induced by oral challenge with bovine rotavirus in a neonatal calf model. The bovine rotavirus-specific passive antibodies were produced before the study by hyperimmunization of pregnant cows during the dry period with an adjuvanted vaccine containing recombinantly-expressed rotavirus virus-like particles. Eighty-three calves were cleanly collected at birth and randomly assigned to 1 of 3 groups as follows: (1) control group that was colostrum deprived and fed milk replacer for first feeding, (2) group that was colostrum deprived and fed milk replacer mixed with antirotavirus antibodies for first feeding, or (3) group that was fed colostrum replacer mixed with antirotavirus antibodies and a product approved by the US Department of Agriculture containing antibodies against Escherichia coli K99 and bovine coronavirus for first feeding. One of the 3 treatments was administered within 6 h of birth to each calf, followed by oral challenge with bovine rotavirus 3 h later. Calves were observed through 7 d of age and scored according to a standardized scale for clinical signs of diarrhea, change in appetite, depression, and dehydration. Twice daily, measurements of rectal temperature and collection of feces were performed. Fecal samples were assessed for infectious agents commonly associated with diarrhea, and bovine rotavirus shedding was quantified. There were 24 of 28 (86%) calves in the control group that received no antibodies that had signs of severe diarrhea, whereas 57% of the calves that received antirotavirus in milk replacer experienced severe diarrhea, and 7% of calves that received colostrum replacer mixed with antigen-specific bovine rotavirus antibodies showed signs of severe diarrhea. Calves that received colostrum replacer mixed with antigen-specific bovine rotavirus antibodies had a mean duration of 0.9 d of diarrhea compared with 2.7 d in the control group. Calves in the group that was colostrum deprived and fed milk replacer with antirotavirus antibodies had a mean duration of diarrhea of 1.7 d. Rotavirus peak fecal shedding was 3.5 d in the group with milk replacer only, 5.5 d in the milk replacer with antibody group, and 6.5 d in calves in the colostrum replacer group. When bovine rotavirus antigen-specific antibody was fed in milk replacer to colostrum-deprived calves or in conjunction with colostrum replacer that also contained supplemental antibodies against Escherichia coli K99 and bovine coronavirus, those calves were observed to have reduced the onset, duration, and severity of diarrhea when compared with milk replacer placebo.

Evaluation of 4 predictive algorithms for intramammary infection status in late-lactation cows.

The objective of this observational study was to compare 4 cow-level algorithms to predict cow-level intramammary infection (IMI) status (culture and MALDI-TOF) in late-lactation US dairy cows using standard measures of test performance. Secondary objectives were to estimate the likely effect of each algorithm, if used to guide selective dry cow therapy (SDCT), on dry cow antibiotic use in US dairy herds, and to investigate the importance of including clinical mastitis criteria in algorithm-guided SDCT. Cows (n = 1,594) from 56 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each farm visit, aseptic quarter-milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status, which was considered the reference test in this study. Clinical mastitis records and Dairy Herd Improvement Association test-day somatic cell count data were extracted from herd records and used to perform cow-level risk assessments (low vs. high risk) using 4 algorithms that have been proposed for SDCT in New Zealand, the Netherlands, United Kingdom, and the United States. Agreement between aerobic culture (reference test; IMI vs. no-IMI) and algorithm status (high vs. low risk) was described using Cohen's kappa, test sensitivity, specificity, negative predictive value, and positive predictive value. The proportion of cows classified as high risk among the 4 algorithms ranged from 0.31 to 0.63, indicating that these approaches to SDCT could reduce antibiotic use at dry-off by 37 to 69% in the average US herd. All algorithms had poor agreement with IMI status, with kappa values ranging from 0.05 to 0.13. Sensitivity varied by pathogen, with higher values observed when detecting IMI caused by Streptococcus uberis, Streptococcus dysgalactiae, Staphylococcus aureus, and Lactococcus lactis. Negative predictive values were high for major pathogens among all algorithms (≥0.87), which may explain why algorithm-guided SDCT programs have been successfully implemented in field trials, despite poor agreement with overall IMI status. Removal of clinical mastitis criteria for each algorithm had little effect on the algorithm classification of cows, indicating that algorithms based on SCC alone may have similar performance to those based on SCC and clinical mastitis criteria. We recommend that producers implementing algorithm-guided SDCT use algorithm criteria that matches their relative aspirations for reducing antibiotic use (high specificity, positive predictive value) or minimizing untreated IMI at dry-off (high sensitivity, negative predictive value).

Hepatic effects of rumen-protected branched-chain amino acids with or without propylene glycol supplementation in dairy cows during early lactation.

Essential amino acids (EAA) are critical for multiple physiological processes. Branched-chain amino acid (BCAA) supplementation provides energy substrates, promotes protein synthesis, and stimulates insulin secretion in rodents and humans. Most dairy cows face a protein and energy deficit during the first weeks postpartum and utilize body reserves to counteract this shortage. The objective was to evaluate the effect of rumen-protected BCAA (RP-BCAA; 375 g of 27% l-leucine, 85 g of 48% l-isoleucine, and 91 g of 67% l-valine) with or without oral propylene glycol (PG) administration on markers of liver health status, concentrations of nonesterified fatty acids (NEFA) and ß-hydroxybutyrate (BHB) in plasma, and liver triglycerides (TG) during the early postpartum period in dairy cows. Multiparous Holstein cows were enrolled in blocks of 3 and randomly assigned to either the control group or 1 of the 2 treatments from calving until 35 d postpartum. The control group (n = 16) received 200 g of dry molasses per cow/d; the RP-BCAA group (n = 14) received RP-BCAA mixed with 200 g of dry molasses per cow/d; the RP-BCAA plus PG (RP-BCAAPG) group (n = 16) received RP-BCAA mixed with 200 g of dry molasses per cow/d, plus 300 mL of PG, once daily from calving until 7 d in milk (DIM). The RP-BCAA and RP-BCAAGP groups, on average (± standard deviation), were predicted to receive a greater supply of metabolizable protein in the form of l-Leu 27.4 ± 3.5 g/d, l-Ile 15.2 ± 1.8 g/d, and l-Val 24.2 ± 2.4 g/d compared with the control cows. Liver biopsies were collected at d 9 ± 4 prepartum and at 5 ± 1 and 21 ± 1 DIM. Blood was sampled 3 times per week from calving until 21 DIM. Milk yield, dry matter intake, NEFA, BHB, EAA blood concentration, serum chemistry, insulin, glucagon, and liver TG and protein abundance of total and phosphorylated branched-chain ketoacid dehydrogenase E1α (p-BCKDH-E1α) were analyzed using repeated measures ANOVA. Cows in the RP-BCAA and RP-BCAAPG groups had lower liver TG and lower activities of aspartate aminotransferase and glutamate dehydrogenase during the first 21 DIM, compared with control. All cows, regardless of treatment, showed an upregulation of p-BCKDH-E1α at d 5 postpartum, compared with levels at 21 d postpartum. Insulin, Met, and Glu blood concentration were greater in RP-BCAA and RP-BCAAPG compared with control during the first 35 DIM. Therefore, the use of RP-BCAA in combination with PG might be a feasible option to reduce hepatic lipidosis in dairy cows during early lactation.

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.

Short communication: Comparative performance of 3 on-farm culture systems for detection of mastitis pathogens interpreted by trained and untrained observers.

On-farm culture (OFC) systems facilitate pathogen-based mastitis management and can facilitate antimicrobial stewardship on dairy farms. Interpretation of the results, however, may present a challenge for those with limited microbiology experience. Here, we compared results of 3 OFC systems interpreted by trained and untrained observers against results of a standard laboratory reference method (aerobic culture and mass spectrometry). Milk samples (280 quarter and 60 composite) were selected from submissions for routine diagnostic testing to Quality Milk Production Services (Cornell University, Ithaca, NY) between August 2017 and January 2018. Samples were cultured simultaneously using the standard laboratory reference method and 3 commercially available OFC systems that varied in detail of pathogen identification (provided in parentheses) as follows: (1) Minnesota Easy Culture System II Bi-plate (University of Minnesota Laboratory for Udder Health, St. Paul; gram-positive, gram-negative), (2) Minnesota Easy Culture System II Tri-plate (gram-positive, gram-negative, some genus level), and (3) FERA Diagnostics and Biologicals AccuMast plate (Ithaca, NY; genus level, some species level). After 18 to 24 h of incubation, OFC plates were interpreted by 1 trained observer (>10 yr of experience in milk microbiology) and 6 untrained observers with no previous milk microbiology training, using only the manufacturers' instructions for guidance. Strength of agreement (κ) between observer groups and the reference method was determined for the available outcomes of each system. Interpreted by the trained observer, agreement was moderate for identifying gram-positive organisms (Bi-plate, κ = 0.56) and substantial for Streptococcus spp. (Tri-plate, κ = 0.64, AccuMast κ = 0.61). Interpretation by untrained observers resulted in fair agreement (κ = 0.29-0.37) for these organisms. Moderate agreement (κ = 0.43-0.59) was found across all 3 OFC for the identification of gram-negative organisms (Bi-plate), non-aureus staphylococci (Tri-plate and AccuMast), Lactococcus spp., and Enterococcus spp. (AccuMast) when interpreted by the trained observer, and fair to moderate agreement was found (κ = 0.31-0.53) among untrained observers. Across all 3 OFC, agreement was almost perfect (κ = 0.80-0.89) for Staphylococcus aureus for the trained observer, and moderate to substantial (κ = 0.56-0.61) for untrained observers. We concluded that all 3 OFC appeared suitable to support pathogen-based mastitis management when operated by trained observers. Training beyond the instruction manual is a prerequisite to make OFC systems useful for pathogen-based mastitis management.

Mycoplasma species isolated from bovine milk collected from US dairy herds between 2016 and 2019.

Determining the species of mycoplasma isolated from culture-positive milk samples is important for understanding the clinical significance of their detection. Between August 2016 and December 2019, 214,518 milk samples from 2,757 dairy herds were submitted to Quality Milk Production Services (QMPS) at Cornell University for mycoplasma culture. From these samples, 3,728 collected from 204 herds were culture positive. Based on the request of herd managers, owners, or veterinarians, 889 isolates from 98 herds were subjected to molecular identification by PCR and amplicon sequencing. The largest proportion of the identified isolates were from New York State (78.1%), while the others came from the eastern United States (17.8%), Texas (2.0%), and New Mexico (2.1%). As expected, Mycoplasma spp. were the most common (855 isolates, 96.2%) and Acholeplasma spp. accounted for the remainder (34 isolates, 3.8%). Mycoplasma bovis was the most prevalent Mycoplasma species (75.1%), followed by M. bovigenitalium (6.5%), M. canadense (5.9%), M. alkalescens (5%), M. arginini (1.7%), M. californicum (0.1%), and M. primatum (0.1%). A portion of the isolates were confirmed as Mycoplasma spp. other than M. bovis but were not identified at the species level (16 isolates, 1.8%) because further information was not requested by the manager, owner, or veterinarian. Mycoplasma bovis was the only species identified in 59 of the 98 herds. However, more than 1 Mycoplasma sp. was identified in 29 herds, suggesting that herd infection with 2 or more mycoplasmas is not uncommon. Moreover, a Mycoplasma sp. other than M. bovis was the only species identified in 8 herds. From the subset of 889 mycoplasma culture-positive isolates from 98 herds, we determined that over a third of the herds had either more than 1 Mycoplasma sp. or a Mycoplasma sp. other than M. bovis detected in their milk samples. In conclusion, we observed that M. bovis is the most common pathogenic Mycoplasma species found in mastitic milk, but other Mycoplasma species are not uncommon. Our results suggest that it is critical to test milk samples for mycoplasmas using diagnostic tests able to identify both the genus and the species.

The effect of 2 different premilking stimulation regimens, with and without manual forestripping, on teat tissue condition and milking performance in Holstein dairy cows milked 3 times daily.

The objectives were to study the effect of 2 different premilking stimulation regimens, with and without manual forestripping, on teat tissue condition and milking characteristics in dairy cows. In a randomized controlled crossover study, 130 Holstein cows milked 3 times daily were assigned to treatment and control groups. Premilking udder preparation for the treatment group consisted of: (1) predipping with 1% iodine, (2) sequential forestripping of 3 streams of milk per quarter, (3) wiping of teats, and (4) attachment of the milking unit. Premilking udder preparation for the control group was identical except that the forestripping step was omitted. The mean tactile stimulation durations were 16 s and 7 s for the treatment and control group, respectively. The time spent from first tactile stimulus (either forestripping or wiping of teats) to milking unit attachment was kept consistent at 90 s for both groups. The study lasted for 14 d with 2 periods, each consisting of a 2-d adjustment time followed by 5 d of data collection. Machine milking-induced short-term changes to the teat tissue were assessed by palpation and visually. The following milking characteristics were assessed with electronic on-farm milk meters: milk yield (MY), milking unit-on time (MUOT), 2-min MY (2MIN), and time spent in low milk flow rate (LMF). Generalized linear mixed models were used to describe the effect of treatment on the outcome variables. The odds of machine milking-induced short-term changes to the teat tissue were lower for cows that received forestripping compared with cows that were not forestripped (odds ratio = 0.31; 95% confidence interval = 0.22-0.42). Least squares means (95% confidence interval) for cows that were forestripped and animals that were not forestripped, respectively, were 12.7 (12.2-13.2) and 12.7 (12.2-13.2) kg for MY and 6.1 (5.8-6.4) and 5.6 (5.3-5.9) kg for 2MIN. There was an interaction between treatment and MY for LMF. Time spent in LMF for cows that were forestripped and received no forestripping, respectively, were 18 (17-20) and 24 (23-26) s for a MY level of 10 kg; and 13 (12-14) and 15 (14-16) s for a MY level of 15 kg. The effect of treatment on MUOT was modified by parity. Milking unit-on times for animals in first, second and third or greater lactation, respectively, were 230 (219-243), 249 (236-262), and 260 (249-272) s for cows that were forestripped, and 245 (232-258), 252 (239-266), and 268 (257-281) s for cows that received no forestripping. In this study, cows that were forestripped had shorter MUOT, higher 2MIN, lower LMF, and lower odds of exhibiting changes to the teat tissue after machine milking. We conclude that wiping of teats during premilking udder preparation alone and omitting forestripping of teats without compensating for the loss in stimulation time may not provide sufficient tactile stimulation to elicit the cows' maximum physiological milk-ejection capacity. This can aggravate the adverse effects of vacuum-induced forces on teat tissue during machine milking, diminish animal well-being, and possibly affect udder health.

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.

Blood perfusion of teat tissue in dairy cows: Changes associated with pre-milking stimulation and machine milking.

Mechanical forces during machine milking of dairy cows evoke circulatory impairment of the teat tissue that may affect the teats' defense mechanisms against mastitis pathogens. Ample research describes dimensional changes of different teat traits after machine milking, whereas reports that describe changes in blood circulation of dairy cows' teats are limited. Therefore, the objectives of this study were to (1) describe changes in teat blood circulation that occur after pre-milking teat stimulation and machine milking and (2) study the effect of 2 different milking liners on machine milking-induced changes in teat blood flow. In a randomized trial, Holstein dairy cows were stratified by parity, stage of lactation, and average daily milk yield during the previous week, and allocated to 1 of 2 treatment groups. Treatment consisted of 1 milking observation with either a round or multisided concave milking liner. Teat scans were taken of the left front and the right hind teats using power Doppler ultrasonography. Imaging occurred before pre-milking udder preparation (T1), after completion of pre-milking udder preparation but before milking-unit attachment (T2), and immediately after unit detachment (T3). Perfusion intensity measurements from teat scans were performed with a commercially available software program. Data from 109 cows were analyzed. A general linear mixed model showed differences in perfusion intensity between time points. Least squares means (95% confidence intervals) for T1, T2, and T3, respectively, were 0.035% (0.026-0.047), 0.124% (0.093-0.164), and 0.095% (0.073-0.124). Conversely, no statistically significant differences between treatment groups were observed. We conclude that teat blood circulation is subjected to several influences, including inherent circulatory regulation mechanisms, as well as extrinsic factors such as machine milking. Future research is warranted to decipher the magnitude of their influence and to further our understanding of how these changes relate to the susceptibility to intramammary infection and milking performance.

Randomized equivalence study comparing the efficacy of 2 commercial internal teat sealants in dairy cows.

The use of an internal teat sealant (ITS) at dry-off has been repeatedly shown to improve udder health in the subsequent lactation. However, almost all ITS research conducted in North America has evaluated one product (Orbeseal, Zoetis, Parsippany, NJ). The objective of this study was to evaluate a new ITS product (Lockout, Boehringer-Ingelheim Animal Health, Duluth, GA), by comparing it directly to Orbeseal in a multi-site, randomized, positively controlled equivalence trial for health indicators during the dry period [quarter-level new intramammary infection (IMI) risk, IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM] and during the first 100 DIM [clinical mastitis and culling or death risk and test-day milk somatic cell count (SCC) and milk yield]. At dry-off, cows were randomly allocated to be treated with Orbeseal or Lockout after blanket administration of a cloxacillin dry cow therapy product. Cows were then followed from dry-off until 100 DIM. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods, allowing for the measurement of IMI dynamics during the dry period (i.e., IMI cures and new IMI). The effect of ITS 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). Marginal standardization was used to derive risk difference estimates. An equivalence hypothesis test was conducted to compare ITS groups for dry period new IMI risk (margin of equivalence was ±5% units). The effect of ITS group on clinical mastitis and culling or death was determined using Cox proportional hazards regression. The effect of ITS group on test-day SCC and milk yield was determined using linear mixed models. Final models indicated that measures of quarter-level IMI dynamics were similar between ITS groups (i.e., risk difference estimates and 95% confidence intervals all close to zero). Furthermore, Lockout was found to be equivalent to Orbeseal for dry period new IMI risk using an equivalence hypothesis test. Hazard ratio estimates for clinical mastitis and culling or death were close to 1 and differences in SCC and milk yield between ITS groups were close to 0, indicating negligible effects of ITS group on test-day SCC and milk yield. In most cases, these effect estimates were relatively precise (i.e., narrow 95% confidence intervals). We conclude that producers using blanket dry cow therapy could consider including Orbeseal or Lockout treatment in their programs.

Randomized controlled trial investigating the effect of 2 selective dry-cow therapy protocols on udder health and performance in the subsequent lactation.

The objective of this study was to compare culture- and algorithm-guided selective dry-cow therapy (SDCT) programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure clinical trial for the following cow-level outcomes: clinical mastitis, removal from the herd, and Dairy Herd Improvement Association (DHIA) test-day milk yield and SCC measures during the first 120 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 only treating quarters from which aseptically collected milk samples tested positive on a rapid culture system 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 met at least one of the following criteria: (1) any DHIA test with a somatic cell count >200,000 cells/mL during the current lactation, and (2) ≥2 clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Clinical mastitis and removal from the herd events (i.e., culling or death) and DHIA test-day data from dry-off to 120 DIM were extracted from herd records. Hazard ratios (HR) for the effect of treatment group on clinical mastitis and removal from the herd during 1 to 120 DIM were determined using Cox proportional hazards regression. The effects of treatment group on test-day loge-transformed SCC and milk yield were determined using linear mixed models. Final models indicated that either SDCT program was unlikely to increase clinical mastitis risk (HRcult-SDCT/BDCT = 0.82, 95% CI: 0.58, 1.15; HRalg-SDCT/BDCT = 0.83, 95% CI: 0.63, 1.09) or test-day logeSCC (cult-SDCT minus BDCT = 0.05, 95% CI: -0.09, 0.18; alg-SDCT minus BDCT = 0.07, 95% CI: -0.07, 0.21). Risk of removal from the herd and test-day milk yield were similar between treatment groups. Findings from this study indicate that culture- or algorithm-guided SDCT can be used at dry-off without negatively affecting cow health and performance in early lactation.

A randomized trial to study the effect of automatic cluster remover settings on milking performance, teat condition, and udder health.

The objectives were to study the effect of 2 different automatic cluster remover settings on (1) milking characteristics, (2) milk component yields, (3) teat tissue condition, and (4) udder health. In a randomized controlled field trial, Holstein cows (n = 689) from 1 commercial dairy farm with a thrice-daily milking schedule were allocated to 2 treatment groups. Treatment consisted of a cluster remover take-off milk flow threshold of 1.2 (ACR1.2) or 0.8 kg/min (ACR0.8) for 57 d. Milking characteristics (milk yield; and milking unit-on time, MUOT) were obtained with electronic on-farm milk meters. Composite milk samples were collected and analyzed for fat, protein, lactose, and somatic cell count. Machine-milking-induced short- and long-term changes to the teat tissue condition were assessed visually. General linear mixed models demonstrated differences in MUOT, whereas no meaningful differences in milk yield were detected. Milk yield (least squares means, 95% confidence interval) was 11.3 (10.9-11.8) and 11.3 (10.8-11.8) kg in groups ACR1.2 and ACR0.8, respectively. The effect of treatment on MUOT was modified by parity. Milking unit-on time in first-, second-, and ≥third-lactation cows, respectively, was 260.7 (252.0-269.4), 257.8 (247.4-268.1), and 260.2 (252.6-267.9) s in group ACR1.2; and 273.7 (264.9-282.5), 279.1 (269.4-288.8), and 295.7 (287.9-303.6) s in group ACR0.8. We detected no meaningful differences in milk component yields or linear somatic cell score. Least squares means in groups ACR1.2 and ACR0.8, respectively, were milk fat yield, 0.42 (0.40-0.44) and 0.42 (0.40-0.44) kg; milk protein yield, 0.36 (0.35-0.37) and 0.37 (0.36-0.37) kg; milk lactose yield, 0.61 (0.60-0.63) and 0.63 (0.61-0.64) kg, and linear somatic cell score, 1.9 (1.8-2.0) and 1.9 (1.8-2.0). A generalized linear mixed model revealed an effect of treatment on machine-milking-induced short-term changes. The odds of short-term changes to the teat tissue were lower for cows in group ACR1.2 [odds ratio (95% confidence interval) = 0.78 (0.63-0.96)]. No meaningful differences were detected in machine-milking-induced long-term changes between treatment groups. Increasing cluster remover take-off milk flow threshold from 0.8 to 1.2 kg/min decreased individual milking duration and alleviated machine-milking-induced short-term changes to the teat tissue without adversely affecting milking performance or somatic cell count. Future studies are warranted to investigate the effect on milk production and udder health over a whole lactation period.

Distribution of Lactococcus spp. in New York State dairy farms and the association of somatic cell count resolution and bacteriological cure in clinical mastitis samples.

We investigated the distribution of pathogenic non-agalactiae gram-positive, catalase-negative cocci (GPCN) in a convenience sample of New York State dairy farms. Our primary objective with the clinical mastitis (CM) GPCN samples was to evaluate somatic cell count (SCC) resolution and bacteriological cure of Streptococcus dysgalactiae or Streptococcus uberis versus Lactococcus lactis or Lactococcus garvieae in cows that received an approved intramammary treatment. In phase I, we assessed the distribution of the GPCN and SCC resolution. In phase II, we evaluated the SCC resolution and bacteriological cure in CM samples from the 4 farms with the highest prevalence of L. lactis or L. garvieae in phase I. In phase I, 8,868 CM and subclinical mastitis (SCM) milk samples were received from 143 farms. The GPCN samples identified by culture were confirmed with MALDI-TOF. From the 473 MALDI-TOF-confirmed GPCN samples, 155 were S. dysgalactiae (33%); 150, S. uberis (32%); 112, L. lactis (24%); 16, L. garvieae (3%); and 40, other GPCN (8%). From these, 277 were CM samples and 127 were eligible for the evaluation of SCC resolution, which was defined as SCC ≤200,000 cells/mL in a composite sample 15 to 60 d post-diagnosis. The odds of SCC resolution in CM samples was evaluated with multivariable logistic regression, and the odds were 6.1 [95% confidence interval (CI):2.7-13.9] times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. In phase II, a total of 1,662 CM and SCM samples were evaluated with microbiological methods as in phase I, of which 211 samples were confirmed by MALDI-TOF: 39% were S. dysgalactiae (n = 61) and S. uberis (n = 21); 55%, L. lactis (n = 114) and L. garvieae (n = 2); and 6%, other GPCN (n = 13). In total, 168 CM samples were eligible for analysis and 118 were included in the final SCC resolution model. Similar statistical methods as in phase I were performed, and the odds of SCC resolution were 2.4 (95% CI: 1.1-5.5) times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. Bacteriological cure was defined as having a different or negative culture on a quarter sample taken 14 to 28 d after initial diagnosis. The odds of bacteriological cure (n = 121) were 8.0 (95% CI: 2.5-25.6) times higher for S. dysgalactiae or S. uberis compared with L. lactis or L. garvieae. Differences in SCC resolution and bacteriological cure between these groups may dictate a different management approach.