Changes in prepartum behaviors such as total daily rumination (TDR), total daily activity (TDA) and dry matter intake (DMI) have the potential to be used as early indicators for cows at risk for subclinical hypocalcemia (SCH) or hypomagnesemia (HYM) after calving. Our objective was to investigate associations between average daily rate of change in total daily rumination (ΔTDR), total daily activity (ΔTDA) and dry matter intake (ΔDMI) from −3 days prepartum to calving with SCH and HYM at D0 or D3 relative to calving. Prepartum TDR, TDA and DMI were measured in 64 Holstein dairy cows. Blood samples were taken at D0 and D3 post-calving for the measurement of total plasma Ca and Mg concentration. Linear regression models were used to analyze the association between ΔTDR, ΔTDA and ΔDMI and SCH and HYM at D0 and D3 relative to calving. Potential confounding variables were offered to the models and backwards selection was used to determine which covariates to retain. No significant differences in prepartum ΔTDR, ΔTDA or ΔDMI were found between cows with or without SCH and HYM at D0 and D3. Our results suggest that the change in TDR, TDA and DMI in the last 3 days prepartum are not effective predictors for cows that will have SCH or HYM in the first 3 days postpartum.

To determine the effects of grain type (rolled-corn vs. rolled-barley) and dried corn distillers’ grains with solubles (DDGS) oil concentration (low = 4.5% vs. moderate = 7.9%) on ruminal pH, ammonia (NH₃) and volatile fatty acid (VFA) concentrations, in vitro enteric methane (CH₄) and carbon dioxide (CO₂) production, and digestive enzyme activity, eight ruminally cannulated Holstein steers (715 ± 61.4 kg) were used in a 4 × 8 Latin rectangle with a 2 × 2 factorial arrangement of treatments. Diets were offered for ad libitum intake. Experimental periods were 24 d with 7 d of diet adaptation, 7 d of sample collection, and a 10 d transition between periods. No differences were observed for ruminal NH₃, total VFA concentration, pH, or in vitro concentration of CH₄ or CO₂ after 24 h of incubation among treatments. The lag time for in vitro gas production and degradation was greater (P = 0.03) from steers fed diets containing rolled-corn than rolled-barley. There were grain type × DDGS interactions (P ≤ 0.02) observed for α-amylase and trypsin activity (U L⁻¹ ruminal fluid). Maltase activity (U L⁻¹ ruminal fluid) was greater (P ≤ 0.01) in steers fed diets containing rolled-corn than rolled-barley and in steers fed diets containing low- compared with moderate-oil DDGS. These results indicate that, although ruminal enzyme activity was influenced, feeding different grain types (rolled-corn vs. rolled-barley) or DDGS with differing oil concentration (moderate vs. low) did not negatively influence ruminal fermentation or in vitro CH₄ production.

We investigated whether delaying oral calcium (Ca) bolus administration to the second day postpartum (DEL) was noninferior to bolus administration within 24 h of calving (CON) in its effects on plasma Ca concentrations during the first five days in milk (DIM). We also investigated the effects of DEL vs. CON strategies on magnesium (Mg) concentrations and daily rumination time (RT). Twenty-three multiparous (parity ≥ 3) dairy cows were randomly assigned to the CON (n = 11) or DEL (n = 12) treatment. Blood Ca and Mg were measured at 1–5 DIM and RT was monitored from −7 d to 7 d relative to calving. The noninferiority margin was a difference in Ca concentration of 0.15 mmol/L. Blood Ca and Mg concentrations and RT were analyzed by multivariable linear mixed models accounting for repeated measures. Blood Ca concentrations were 0.07 mmol/L (95% confidence interval: −0.30–0.17) less in DEL cows than CON cows, thus non-inferiority results were inconclusive. The Ca concentration increased across the first 5 DIM but did not differ between treatments while Mg concentrations decreased in both treatments (p < 0.001). There was no treatment difference in RT (CON: 436 ± 21, DEL: 485 ± 19 min/d). While noninferiority results were inconclusive, similar blood Ca dynamics between CON and DEL treatment strategies indicates that delayed Ca administration is a potential management option for commercial dairy farms; however, additional studies using large sample sizes are warranted to confirm these findings.

Summary: Blood samples were collected from 166 cows into sodium fluoride tubes. One aliquot was used to compare glucose concentrations between repeated freeze-thaw cycles (1-4), and 3 were used for comparison of storage time (2, 3, 4, or 16 weeks) at -20°C. Two assay systems and reactions were used for quantification of the glucose concentration in the aliquots. It was observed that freeze-thaw cycles and storage time had minimal effects on glucose concentration measured when using the peroxidase and glucose oxidase enzyme (PGO). Concentrations measured over time for storage and freeze-thaw cycles using the hexokinase assay system (HK) were more variable and lower compared with PGO.

Research has shown that selective dry cow therapy (SDCT) can be implemented in well-managed dairy farms without negatively affecting postpartum udder health and performance. This raises the question of whether dry cow therapy (DCT) is necessary in well-managed farms. Our primary objective was to assess the effect of withholding DCT from cows at the end of their first lactation on postpartum quarter-level IMI prevalence. Our secondary objectives were to evaluate the effect of DCT omission on postpartum quarter-level IMI prevalence in subgroups of quarters, stratified by quarter-level SCC and California Mastitis Test (CMT) results at dry-off, and to use those findings to predict the effect of SCC- and CMT-guided SDCT programs on antibiotic use and udder health. This randomized controlled trial enrolled 446 cows in a single herd, which were assigned at dry-off to receive either intramammary antibiotics and an internal teat sealant (ATB+ITS) or only an internal teat sealant (ITS-only). Quarter-level milk samples were collected at dry-off to determine SCC and CMT results. During the first 2 wk after calving, quarter-level milk samples were collected and submitted for milk culture. Logistic regression was used to investigate the effect of DCT omission on postpartum IMI prevalence overall and in subgroups stratified by SCC (50, 100, 150, 200, 400 × 1,000 cells/mL) or CMT results (no reaction, trace, positive, or more) at dry-off. Estimated marginal means were used to predict the effect of SCC- and CMT-guided SDCT on antibiotic use and postcalving IMI prevalence. Withholding DCT from all quarters at dry-off in first-lactation cows increased the early postpartum prevalence of gram-positive pathogens during the second lactation (relative risk [RR]: 1.29; 95% CI: 0.99, 1.65), particularly NAS and mammaliicocci (RR [95% CI]: 1.95 [1.05, 3.57]), whereas the prevalence of Staphylococcus aureus or Streptococcus spp. and Streptococcus-like organisms remained low in both groups. Quarter-level SCC at dry-off was demonstrated to be useful for guiding DCT decisions. Quarters with high SCC at dry-off in the ITS-only group had a higher risk of postpartum gram-positive IMI compared with ATB+ITS quarters, with RR ranging from 1.36 to 2.29. In contrast, among quarters with SCC equal or below the investigated cutoffs, the risk of postpartum IMI was similar between ITS-only and ATB+ITS groups, with RR ranging from 0.96 to 1.18, even at cutoffs as high as 400,000 cells/mL. Estimated marginal means from statistical models in this study found that limiting antibiotic treatments to quarters with SCC >400,000 cells/mL could reduce antibiotic treatment at dry-off by 85.1% without significantly affecting gram-positive IMI postpartum prevalence (RR [95% CI]: 1.07 (0.78, 1.47), when compared with blanket DCT. However, CMT-based SDCT appeared less effective, as both CMT-positive and CMT-negative quarters showed a numerical increase in postpartum gram-positive IMI prevalence when DCT was withheld (RR between 1.24 to 1.28 and 1.28 to 1.86, respectively). In conclusion, omitting DCT at the end of the first lactation may increase gram-positive IMI and is therefore not recommended. However, quarter-level SCC-guided SDCT appears to be a viable strategy to reduce antibiotic use without substantially affecting postpartum IMI prevalence.

Summary: Blood samples were collected from 20 cows into 3 tubes with different anticoagulants, including sodium fluoride (NaF), dipotassium ethylenediaminotetraacetate (K₂-EDTA), and lithium heparin (Li-Hep) tubes. Two different enzymatic reactions, peroxidase and glucose oxidase (PGO) and hexokinase (HK), were used for quantification of glucose concentration in the plasma samples collected with the different anticoagulants. Across both methods, samples collected in NaF yielded lower glucose concentrations compared with K₂-EDTA and Li-Hep. Additionally, the samples quantified with HK yielded lower glucose concentrations than the same samples quantified with PGO.