A randomized controlled trial to evaluate propylene glycol alone or in combination with dextrose as a treatment for hyperketonemia in dairy cows.

Our objective was to investigate the effect of i.v. dextrose as an adjunct therapy to oral propylene glycol on the resolution of hyperketonemia (HYK; blood ß-hydroxybutyrate ≥1.2 mmol/L), disease incidence, and early lactation milk yield. Cows (n = 1,249) between 3 and 16 d in milk (DIM) from 4 New York dairy farms were screened once weekly for HYK for 2 wk. Those with HYK and no previous history of retained placenta, metritis, or HYK were randomly assigned to 1 of 3 treatment groups: 300 mL of oral 100% propylene glycol for 3 d (PG3); 300 mL of oral 100% propylene glycol for 3 d plus 500 mL i.v. 50% dextrose on d 1 (PG3D1); or 300 mL of oral 100% propylene glycol for 3 d plus 500 mL i.v. 50% dextrose on all 3 d (PG3D3). Cows with a blood ß-hydroxybutyrate <1.2 mmol/L at initial screening were re-screened the following week and randomly assigned to the above treatment groups if blood ß-hydroxybutyrate was ≥1.2 mmol/L. Cows were assessed for post-treatment HYK resolution 1 and 2 wk after initial HYK diagnosis. We collected farm-diagnosed occurrence of adverse events (sold, died, metritis, displaced abomasum, or ketosis) during the first 60 DIM and milk yield data from the first 10 wk of lactation from herd management software. We used mixed-effects multivariable Poisson regression models to assess the risk of post-treatment HYK resolution at 1 and 2 wk following initial HYK diagnosis and adverse event occurrence among treated cows. We used repeated-measures ANOVA to assess differences in average daily milk yield between treatments. The overall HYK incidence was 30.1% (n = 373). Sixty-four percent of cows (n = 237) were assigned to a treatment group in the first week (3 to 9 DIM), and 36% (n = 136) assigned the second week (10 to 16 DIM). The incidence of 1 or more adverse events during the first 60 DIM was 9.4% (n = 35). We found no effect of treatment on risk of post-treatment HYK resolution at wk 1 (PG3 56.9%, PG3D1 45.0%, PG3D3 50.0%) or wk 2 (PG3 60.0%, PG3D1 52.1%, PG3D3 59.5%) following initial diagnosis, or for risk of adverse event occurrence (PG3 7.4%, PG3D1 8.0%, PG3D3 12.6%). Average daily milk yield (mean ± SE) was similar between treatment groups (PG3: 42.7 ± 0.6 kg/d, PG3D1: 42.4 ± 0.6 kg/d, PG3D3: 42.6 ± 0.6 kg/d). The addition of dextrose for 1 or 3 d provided no improvement in resolution of ketosis assessed once weekly, reduction in adverse events during the first 60 d of lactation, or a difference in average daily milk yield during the first 10 wk of lactation.

The microbiome of Escherichia coli and culture-negative nonsevere clinical mastitis: Characterization and associations with linear score and milk production.

Culture-negative and Escherichia coli cases are uncommonly treated in pathogen-based protocols for nonsevere mastitis. High-throughput 16S rRNA sequencing might reveal the presence of other pathogens and can provide information on microbial diversity. The objective was to explore the milk microbiome at the time of the mastitis event (enrollment) and its association with survival in the herd, milk production, and postevent linear score (LS) for cows with clinical mastitis characterized as negative or E. coli by culture. Fifty E. coli-positive and 35 culture-negative samples from cases were enrolled. No cases were treated with antimicrobials. All E. coli-positive quarters were characterized as transient; microbiological culture of samples taken 15 d postmastitis were negative for this organism. However, a difference in α-diversity (Shannon index) was present between enrollment and follow-up samples (3.8 vs. 5.1). When α-diversity was explored for enrollment E. coli samples, no relationship was observed between the Shannon indices of these samples and postmastitis LS. Alpha-diversity of the enrollment samples was lower for E. coli-positive cows that subsequently had greater losses in milk production. This difference was explained by a greater relative abundance of the family Enterobacteriaceae (67.8 vs. 38.4%) for cows that dropped in production. Analysis of composition of the microbiome identified one phylum, Proteobacteria, that differed between E. coli-positive cows that dropped in production and those that did not. Evaluation of ß -diversity found no statistical relationship between postmastitis LS and the microbiome. When evaluating α- and ß-diversities and composition of the microbiomes for culture-negative quarters, no associations were found for milk production changes and postmastitis LS. Three cows did not remain in the herd, limiting the ability to analyze survival. The findings suggest that a contributing factor to negative outcomes in E. coli-positive cows is relative abundance of this pathogen, and that no single or collective group of bacterial families is associated with milk production changes or postmastitis LS in culture-negative quarters. Although additional studies should be performed, the absence of associations between outcomes explored and microbial profiles in this study suggests that we are not missing opportunities by not treating nonsevere E. coli or culture-negative mastitis cases.

Clinical outcome comparison of immediate blanket treatment versus a delayed pathogen-based treatment protocol for clinical mastitis in a New York dairy herd.

The purpose was to compare immediate intramammary antimicrobial treatment of all cases of clinical mastitis with a selective treatment protocol based on 24-h culture results. The study was conducted at a 3,500-cow commercial farm in New York. Using a randomized design, mild to moderate clinical mastitis cases were assigned to either the blanket therapy or pathogen-based therapy group. Cows in the blanket therapy group received immediate on-label intramammary treatment with ceftiofur hydrochloride for 5 d. Upon receipt of 24 h culture results, cows in the pathogen-based group followed a protocol automatically assigned via Dairy Comp 305 (Valley Agricultural Software, Tulare, CA): Staphylococcus spp., Streptococcus spp., or Enterococcus spp. were administered on-label intramammary treatment with cephapirin sodium for 1 d. Others, including cows with no-growth or gram-negative results, received no treatment. A total of 725 cases of clinical mastitis were observed; 114 cows were not enrolled due to severity. An additional 122 cases did not meet inclusion criteria. Distribution of treatments for the 489 qualifying events was equal between groups (pathogen-based, n = 246; blanket, n = 243). The proportions of cases assigned to the blanket and pathogen-based groups that received intramammary therapy were 100 and 32%, respectively. No significant differences existed between blanket therapy and pathogen-based therapy in days to clinical cure; means were 4.8 and 4.5 d, respectively. The difference in post-event milk production between groups was not statistically significant (blanket therapy = 34.7 kg; pathogen-based = 35.4 kg). No differences were observed in test-day linear scores between groups; least squares means of linear scores was 4.3 for pathogen-based cows and 4.2 for blanket therapy cows. Odds of survival 30 d postenrollment was similar between groups (odds ratio of pathogen-based = 1.6; 95% confidence interval: 0.7-3.7) as was odds of survival to 60 d (odds ratio = 1.4; 95% confidence interval: 0.7-2.6). The one significant difference found for the effect of treatment was in hospital days; pathogen-based cows experienced, on average, 3 fewer days than blanket therapy cows. A majority (68.5%) of moderate and mild clinical cases would not have been treated if all cows on this trial were enrolled in a pathogen-based protocol. The use of a strategic treatment protocol based on 24-h postmastitis pathogen results has potential to efficiently reduce antimicrobial use.

Randomized noninferiority trial comparing 2 commercial intramammary antibiotics for the treatment of nonsevere clinical mastitis in dairy cows.

The purpose was to evaluate 2 intramammary treatments for mild-to-moderate cases of clinical mastitis in a noninferiority comparison. Noninferiority trials are intended to show whether a given treatment, hetacillin potassium, has at least comparable efficacy as the reference treatment, ceftiofur hydrochloride. Treatments can be deemed inferior to the reference treatment by an amount less than the margin of noninferiority, or inconclusive if the confidence interval crosses the margin of noninferiority. Cows with clinical mastitis from 6 farms were considered for enrollment. Using a randomized design, cows with mild or moderate mastitis in 1 quarter were assigned to on-label treatment with either ceftiofur or hetacillin. A total of 596 cows met the criteria needed for continued enrollment. Treatment distribution resulted in 309 cows in the ceftiofur group and 287 cows in the hetacillin group. Mixed regression analysis was performed for the following outcomes: bacteriological cure, pathogen cure, clinical cure, postevent milk production and linear score, and survival to d 30 and 60. Cox proportional hazards analysis was used to describe treatment effect on survival and mastitis risks. Bacteriological cure, defined as absence of causative organism in samples retrieved at d 14 and 21 postmastitis, was similar between groups. No significant statistical differences were found in cure risk, and noninferiority of hetacillin relative to ceftiofur for bacteriological cure was conclusive (hetacillin=67%, ceftiofur=72%). Absence of a pathogen on both follow-up samples designated a cow as a pathogen cure. Pathogen cure was similar between treatment groups and noninferiority of hetacillin relative to ceftiofur was shown (hetacillin=35%, ceftiofur=32%). Clinical cure (hetacillin=68%, ceftiofur=64%), postevent milk production (hetacillin=37.0kg, ceftiofur=38.2kg), and linear scores (hetacillin=3.4, ceftiofur=3.1) were also not statistically different between treatment groups. Noninferiority of hetacillin relative to ceftiofur was shown for survival to d 30 and survival to d 60, whereas hetacillin was more likely to have a clinical cure than ceftiofur by d 4. No differences were seen between groups when Cox proportional hazards were performed, neither for exit from the herd in the 60 d following the event nor in the risk for a subsequent mastitis event. These findings can be used to develop farm-specific protocols for clinical mastitis treatment.

Association between subclinical hypocalcemia in the first 3 days of lactation and reproductive performance of dairy cows.

The objective of this study was to determine the effects of subclinical hypocalcemia on reproductive performance in dairy cows. In a prospective cohort study, 97 cows on 2 dairy farms with automatic milking systems were monitored for subclinical hypocalcemia. Animals were enrolled 7 ± 3 days prior to estimated calving date and three parity groups were defined based on the lactation that the animals were going to start: lactation = 1, lactation = 2, and lactation ≥3. Serum calcium concentration (Ca) was measured in all animals in the first 3 DIM and subclinical hypocalcemia (SCH) was defined as Ca ≤ 8.6 mg/dL; animals that presented a low Ca level during all 3 days were classified as chronic SCH (cSCH). Return to cyclicity during the voluntary waiting period was analyzed based on weekly progesterone concentrations measured in serum. Information on reproductive outcomes (i.e., number of breedings, pregnancy status, days open, etc.), were collected from on-farm software after all study cows had completed their study period. Chronic SCH was present in all parity groups with higher incidence in multiparous animals (20% of parity = 1, 32% of parity = 2; and 46% of parity ≥ 3 animals). The cSCH animals took longer to show active ovaries when compared to eucalcemic and SCH animals. In a multivariable Cox's Proportional Hazard model animals with normal Ca were 1.8 times more likely to return to cyclicity by the end of the voluntary waiting period when compared to cSCH animals. Animals with cSCH also had 0.27 odds of being pregnant at first service compared to eucalcemic cows when analyzed by multivariable logistic regression. Subclinical hypocalcemia had a negative effect on return of ovarian function during the voluntary waiting period and decreased the odds of pregnancy at first service. Those cows with cSCH had an even more pronounced impaired reproductive function than those with one subclinical measurement.

The association of subclinical hypocalcemia, negative energy balance and disease with bodyweight change during the first 30 days post-partum in dairy cows milked with automatic milking systems.

In a prospective cohort study, the daily bodyweight (BW) and milk production of 92 cows were recorded using automatic milking systems. The objectives were to characterize calcium serum concentration variability on days 1-3 post-partum and to evaluate the association between subclinical hypocalcemia (SHPC) and change in BW over the first 30 days in milk (DIM) in Holstein dairy cows, while controlling for concurrent disease and negative energy balance (NEB). SHPC was defined as total serum calcium concentration between 6 and 8 mg/dL, NEB was defined as non-esterified fatty acids (NEFA) > 0.7 mEq/L or ß-hydroxybutyrate (BHB) ≥ 1.2 mmol/L. The peak incidence of SHPC was at 1 DIM for all groups (11%, 42% and 60% for parities 1, 2, and ≥3, respectively). All parity groups lost weight (21, 33, and 34 kg) during the first 30 DIM. Parity 1 animals with disease compared with those without disease lost the most weight (2.6 kg/day BW loss vs. <1.9 kg/day, respectively). Normocalcemic parity 2 animals with either NEB or disease lost the most weight (>5 kg/day) compared with those in the SHPC group (≤4.5 kg/day). In parity ≥ 3 animals, SHPC was an important factor for BW loss; SHPC animals lost the most weight (>3.7 kg/day) vs. normocalcemic cows (≤3.3 kg/day) regardless of NEB or disease status. Even though all animals lost weight during early lactation the effect of disease, NEB, and SHPC on BW loss was different in each parity group.