Effects of a phytogenic feed additive on weaned dairy heifer calves subjected to a diurnal heat stress bout

The study objective was to evaluate the effects of a phytogenic feed additive (PFA) on dry matter intake (DMI), average daily gain (ADG), inflammation, and oxidative stress markers of heifer calves exposed to a heat stress bout in the summer. A total of18 Holstein and 4 Jersey heifer calves (192 ± 5 kg of body weight at 162 ± 16 d of age) housed in indoor stalls were assigned to 1 of 2 dietary treatments (n = 11; 9 Holstein and 2 Jersey): (1) a basal total mixed ration (CTL), and (2) CTL top-dressed with 0.25 g/d of PFA. Following 7 d of acclimation, baseline measurements were made over 7 d under regular summer conditions [average temperature-humidity index (THI) = 79 from 0900 to 2000 h, and 75 from 2000 to 0900 h]. Calves were then subjected to a 7-d cyclic heat stress bout (HS) by turning on barn heaters and increasing the barn temperature to 33.0°C only during the daytime (the average THI = 85 from 0900 to 2000 h). The study continued for an extra 4-d period after HS ended (post-HS). The HS increased rectal temperature, skin temperature, and respiration rate from the baseline by 1.0°C, 4.0°C, and 49 breaths/min, respectively. The drinking water intake increased by 32% in response to HS, and calves continued to consume more water (44%) than the baseline consumption even after HS ended. The treatment × time interactions were not significant for feed intake, ADG, partial pressure of O2 in the blood, and blood concentrations of inflammation markers such as haptoglobin and lipopolysaccharide binding protein (LBP), and antioxidant markers such as protein carbonyl and thiobarbituric acid (TBARS). The PFA tended to increase daytime DMI (0.24 kg/d) compared with CTL throughout the experiment but did not affect ADG, which decreased from 1.12 kg/d to 0.26 kg/d in response to HS. Both DMI (13%) and ADG (85%) increased during post-HS relative to baseline, indicating compensatory performances that were not affected by the PFA. Serum haptoglobin and plasma LBP concentrations of PFA calves were 44% and 38% lower than that of CTL calves across all time points. The PFA decreased O2 pressure and tended to decrease protein carbonyl concentration in the blood across all time points. The PFA tended to decrease TBARS concentration on the first day of HS and increase and decrease the ratio of reduced to oxidized glutathione in the blood during the baseline and post-HS periods, respectively. Despite the lack of growth improvements, feeding PFA seems to increase O2 levels in the blood and alleviate oxidative stress and inflammation of heifer calve exposed to diurnal heat waves (~7 d) in the summer.

Embedded microcomputer-based force plate system validation when evaluating lameness severity differentiation under an induced synovitis model in lactating dairy cattle

Bovine lameness has relatively large negative economic and welfare implications on the U.S. dairy industry. Due to the ramifications, early lameness detection will aid in assisting dairy producers to mitigate downstream effects through early treatment. The objective of this study was to determine the minimum standing time required among 2-, 3-, 4-, 5-, and 10 min time intervals to obtain an accurate weight distribution estimate for each leg when attempting to detect lameness. An embedded microcomputer-based force plate system was developed to measure vertical forces from individual cow limb weight distribution to detect bovine lameness when utilizing an induced synovitis lameness model. The force plate has four quadrants, with each load cell quadrant measuring the force placed on it from a single limb. The force plate recorded weight (kg) every second from each load cell quadrant, after which, a 60 s moving average for weight distribution was calculated. A sequential study design was employed to evaluate non-lame and induced lameness to ensure time requirements were consistent. Prior to induction, the force plate system was used to measure weight distribution every second for 15 min. After lameness induction, additional 15 min increments were recorded every 24 h for seven days. Lameness was induced by injecting the left hind distal interphalangeal joint in three cows with amphotericin B, 12 h prior to the start of the study. Data were analyzed using a linear mixed effect that included the fixed effects of day relative to lameness induction, time period, foot and injected foot. Cow within replicate was included as a random effect. Cumulative minutes were assessed up to 15 min by comparing the least square rolling 60 s cumulative means expressed as a percentage of each animal's BW percentage placed on each leg for 2-, 3-, 4-, 5-, and 10 min intervals. Results indicate that the minimum time needed for accurate lameness detection in cows was 2 min.

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.

The effects of zinc amino acid complex on biomarkers of gut integrity, inflammation, and metabolism in heat-stressed ruminants

Study objectives were to evaluate the effects of replacing 40 mg/kg of dietary Zn from Zn sulfate (ZS) with Zn amino acid complex (ZA; Zinpro Corporation, Eden Prairie, MN) on inflammation and intestinal integrity in heat-stressed and pair-fed (PF) ruminants. Forty Holstein steers (173.6 ± 4.9 kg) were randomly assigned to 1 of 5 dietary-environmental treatments: (1) thermoneutral (TN) ad libitum with 75 mg/kg of dry matter (DM) ZS (ZSCON); (2) TN pair-fed with 75 mg/kg DM ZS (ZSPF); (3) TN pair-fed with 40 mg/kg DM ZA and 35 mg/kg DM ZS (ZAPF); (4) heat stress (HS) ad libitum with 75 mg/kg DM ZS (ZSHS); and (5) HS ad libitum 40 mg/kg DM ZA and 35 mg/kg DM ZS (ZAHS). Before study initiation, calves were fed their respective diets for 21 d. Following the pre-feeding phase, steers were transferred into environmental chambers and were subjected to 2 successive experimental periods. During period 1 (5 d), all steers were fed their respective diets ad libitum and housed in TN conditions (20.2 ± 1.4°C, 30.4 ± 4.3% relative humidity). During period 2 (6 d), ZSHS and ZAHS steers were exposed to cyclical HS conditions (27.1 ± 1.5°C to 35.0 ± 2.9°C, 19.3 ± 3.5% relative humidity), whereas the ZSCON, ZSPF, and ZAPF steers remained in TN conditions and were fed ad libitum or pair-fed relative to their ZSHS and ZAHS counterparts. Overall, steers exposed to HS had markedly increased rectal temperature (0.83°C), respiration rate (26 breaths per min), and skin temperature (8.00°C) relative to TN treatments. Rectal temperature from ZAHS steers was decreased (0.24°C) on d 4 to 6 of HS relative to ZSHS steers. Regardless of diet, HS decreased DMI (18%) relative to ZSCON steers. Circulating glucose from HS and PF steers decreased (16%) relative to ZSCON steers. Heat stress and nutrient restriction increased circulating nonesterified fatty acids 2- and 3-fold, respectively, compared with ZSCON steers. Serum amyloid A increased ~2-fold in PF relative to ZSCON and HS steers. We detected no treatment effect on blood pH; however, ZAHS steers had increased HCO₃ relative to ZSHS. Relative to ZSHS, ZAHS steers had increased jejunum villi height (25%), a tendency for increased ileum villi height (9%), and decreased duodenal villi width (16%). In summary, ZA supplementation has some beneficial effects on thermal indices, intestinal architecture characteristics, and biomarkers of leaky gut in heat-stressed steers, indicative of an ameliorated heat load, and thus may be a nutritional strategy to minimize negative consequences of HS.

Randomized controlled trial comparison of analgesic drugs for control of pain associated with induced lameness in lactating dairy cattle

Both the economic loss and welfare implications of lameness affect the dairy industry. Currently no analgesic drugs are approved to alleviate lameness-associated pain in lactating dairy cattle in the United States. In this randomized controlled trial, 48 lactating Holsteins were enrolled to evaluate the effect of oral meloxicam and i.v. flunixin meglumine on induced lameness. Cows were allocated to 1 of 4 treatment groups (n = 12 per group): lameness and flunixin meglumine (LAME + FLU); lameness and meloxicam (LAME + MEL); lameness and placebo (LAME + PLBO); or sham induction and placebo (SHAM + PLBO). Six hours before treatment, arthritis-synovitis was induced in the distal interphalangeal joint with 20 mg of amphotericin B, whereas SHAM cows were given an intra-articular injection of an equal volume (4 mL) of isotonic saline. Cows in LAME + FLU received 2.2 mg/kg flunixin meglumine i.v. and whey protein placebo orally; LAME + MEL were administered 1 mg/kg meloxicam orally and 2 mL/45 kg sterile saline placebo i.v.; LAME + PLBO were administered 2 mL/45 kg sterile saline placebo i.v. and whey protein placebo orally; and SHAM + PLBO received 2 mL/45 kg sterile saline placebo i.v. and whey protein placebo orally. The initial treatment of MEL, FLU, or PLBO was identified as time 0 h and followed by a second dose 24 h later with data collection for 120 h. The methods used to assess analgesic efficacy were electronic pressure mat, visual lameness assessment, visual analog score, plasma cortisol concentration, plasma substance P concentration, mechanical nociception threshold, and infrared thermography imaging. Linear mixed effect modeling was the primary method of statistical analysis. Visual lameness scoring indicated a lower proportion of the FLU + LAME group was lame at the T2 h and T8 h time points in comparison to the positive controls, whereas MEL therapy resulted in a lower proportion of lame cows at the T8 h time point. Cortisol area under the effect curve was lower following FLU therapy compared with LAME + PBLO for the 0-2 h (LSM difference = 35.1 ng·h/mL, 95% CI: 6.8, 63.3 ng·h/mL), 2-8 h (LSM difference = 120.6 ng·h/mL, 95% CI: 77.2, 164.0 ng·h/mL), and 0-24 h (LSM difference = 226.0 ng·h/mL, 95% CI: 103.3, 348.8 ng·h/mL) time intervals. Following MEL therapy, cortisol area under the effect curve was lower than LAME + PLBO for both the 2 to 8 h (LSM difference = 93.6 ng·h/mL, 95% CI: 50.2, 137.0 ng·h/mL) and 0 to 24 h time intervals (LSM difference = 187.6 ng·h/mL, 95% CI: 64.9, 310.4 ng·h/mL). Analysis of data from other assessment modalities failed to discern biologically relevant differences between treatment groups. We conclude that meaningful differences were evident for visual lameness assessment and cortisol from MEL and FLU treatment versus the positive control. Further clinical research is needed toward development of a model that will create reproducible events that are more pronounced in severity and duration of lameness which can be validated as a substitute for naturally occurring lameness cases.

Evaluating effects of zinc hydroxychloride on biomarkers of inflammation and intestinal integrity during feed restriction

Objectives were to evaluate effects of supplemental zinc hydroxychloride (HYD; Micronutrients, Indianapolis, IN) on gut permeability, metabolism, and inflammation during feed restriction (FR). Holstein cows (n = 24; 159 ± 8 d in milk; parity 3 ± 0.2) were enrolled in a 2 × 2 factorial design and randomly assigned to 1 of 4 treatments: (1) ad libitum fed (AL) and control diet (ALCON; 75 mg/kg Zn from zinc sulfate; n = 6); (2) ad libitum fed and HYD diet (ALHYD; 75 mg/kg Zn from HYD; n = 6); (3) 40% of ad libitum feed intake and control diet (FRCON; n = 6); or (4) 40% of ad libitum feed intake and HYD diet (FRHYD; n = 6). Prior to study initiation, cows were fed their respective diets for 21 d. The trial consisted of 2 experimental periods (P) during which cows continued to receive their respective dietary treatments. Period 1 (5 d) served as the baseline for P2 (5 d), during which cows were fed ad libitum or restricted to 40% of P1 feed intake. In vivo total-tract permeability was evaluated on d 4 of P1 and on d 2 and 5 of P2, using the paracellular permeability marker chromium (Cr)-EDTA. All cows were euthanized at the end of P2 to assess intestinal architecture. As anticipated, FR cows lost body weight (∼46 kg), entered into calculated negative energy balance (-13.86 Mcal/d), and had decreased milk yield. Circulating glucose, insulin, and glucagon decreased, and nonesterified fatty acids and β-hydroxybutyrate increased in FR relative to AL cows. Relative to AL cows, FR increased lipopolysaccharide-binding protein, serum amyloid A (SAA), and haptoglobin (Hp) concentrations (2-, 4-, and 17-fold, respectively); and peak SAA and Hp concentrations were observed on d 5. Circulating SAA and Hp from FRHYD tended to be decreased (47 and 61%, respectively) on d 5 relative to FRCON. Plasma Cr area under the curve increased (32%) in FR treatments on d 2 and tended to be increased (17%) on d 5 of P2 relative to AL treatments. No effects of diet were observed on Cr appearance. Relative to AL cows, FR increased jejunum villus width and decreased jejunum crypt depth and ileum villus height and crypt depth. Relative to FRCON, ileum villus height tended to increase in FRHYD cows. Feed restriction tended to decrease jejunum and ileum mucosal surface area, but the decrease in the ileum was ameliorated by dietary HYD. In summary, FR induced gut hyperpermeability to Cr-EDTA, and feeding HYD appeared to benefit some key metrics of barrier integrity.

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.

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 log_e-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 (HR_{cult-SDCT/BDCT} = 0.82, 95% CI: 0.58, 1.15; HR_{alg-SDCT/BDCT} = 0.83, 95% CI: 0.63, 1.09) or test-day log_eSCC (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.

Short communication: Determination of the milk pharmacokinetics and depletion of milk residues of flunixin following transdermal administration to lactating Holstein cows

Flunixin is a nonsteroidal anti-inflammatory drug and the most commonly prescribed analgesic in cattle in the United States. Recently, the US Food and Drug Administration (FDA) approved a transdermal formulation of flunixin for control of pyrexia associated with bovine respiratory disease and the control of pain associated with foot rot. The transdermal formulation is not currently approved for use in lactating dairy cattle in the United States, but extra-label use in dairy cattle is permissible under US regulations. The objectives of this study were to determine the pharmacokinetics in milk of dairy cows treated with transdermal flunixin and determine an appropriate withdrawal time for milk. Ten lactating Holstein cows were enrolled into the study in mid lactation. Following treatment, cows were milked 3 times per day through 144 h. Milk samples were collected for drug analysis using ultra-high-pressure liquid chromatography coupled with a triple quadrupole mass spectrometer. The geometric mean maximum concentration for flunixin in milk was 0.010 μg/mL and was 0.061 μg/mL for the active metabolite, 5-hydroxyflunixin. The geometric mean terminal half-life was 20.71 h for flunixin and 22.62 h for 5-hydroxyflunixin. Calculations to approximate a withdrawal time in milk following transdermal flunixin administration were accomplished using a statistical tolerance limit procedure. This analysis indicated that it would be prudent to observe a withdrawal period of 96 h following the last treatment. This is more than twice as long as the labeled withdrawal period of 36 h following use of the injectable formulation. The withdrawal period suggested by this work should be applied carefully, as this study was not conducted under the full quality control practices required by the US FDA for a full drug approval study. Caution should be taken when applying this withdrawal time to diseased animals, animals that are milked with different milking frequencies, and those in different stages of production as these have all been shown to affect drug depletion from milk.

Effects of transdermal flunixin meglumine on experimentally induced lameness in adult dairy cattle

Lameness is a common animal health condition with significant production and welfare implications. The transdermal formulation of flunixin meglumine is the only approved drug for pain control in cattle in the United States. Thirty adult dairy cows were enrolled in a study to determine the effect of transdermal flunixin on cattle with induced lameness. Cows were allocated to 1 of 3 treatment groups, with 10 cows per group: lameness and flunixin (L+F), lameness and placebo (L+P), or sham induction and placebo (S+P). An arthritis-synovitis was induced in the distal interphalangeal joint of the left hind lateral digit, using 20 mg of amphotericin B, 6 h before the application of treatment. Cows enrolled into the sham induction group had 4 mL of isotonic saline injected into the joint. Cows were dosed with transdermal flunixin at 3.33 mg/kg (1 mL/15 kg), or a placebo at 1 mL/15 kg, every 24 h for 3 d. The first treatment of flunixin or placebo was considered the start of the study, identified as time 0 h. Data were collected from all cows for 120 h following the initial treatment application. Outcome measures included plasma cortisol; substance P; visual lameness assessment; mechanical nociception threshold (MNT), presented as difference between left and right feet; infrared thermography (IRT), presented as difference between left and right feet; and gait analysis using a pressure mat. Cortisol concentrations were lower for the L+F group starting at 1.5 h after drug administration. Substance P levels showed no evidence for treatment differences among groups. Differences between the left hind MNT and right hind MNT were detected, with S+P having the lowest difference at -0.04 kilograms-force (kgf; 95% CI: -1.86 to 1.78 kgf), and L+P having the highest at -2.96 kgf (95% CI: 1.55 to 4.36 kgf). The L+F group was intermediate at -2.08 kgf (95% CI: 0.89 to 3.27 kgf). Similarly, when the difference between the maximum temperatures of the coronary band were examined via IRT, the L+P group had the highest difference at 1.64°C (95% CI: 1.02 to 2.26°C), with the L+F and S+P groups measuring 0.57°C (95% CI: 0.06 to 1.08°C) and 0.53°C (95% CI: -0.2 to 1.25°C) respectively. We found no evidence for differences among treatment groups when analyzing force, contact pressure, step impulse, or stride length. Based on differences in MNT, IRT, and cortisol, transdermal flunixin is an effective analgesic agent for induced lameness. Multiple doses of transdermal flunixin may be required to be clinically effective, based on MNT and IRT data. Further investigation of transdermal flunixin and its analgesic effects is warranted in naturally occurring lameness.

Efficacy of vaccination with a Klebsiella pneumoniae siderophore receptor protein vaccine for reduction of Klebsiella mastitis in lactating cattle

Clinical mastitis caused by Klebsiella spp. is an emerging problem in the US dairy industry and results in a high degree of financial losses to dairy workers. This study was conducted as a randomized, blinded, and placebo-controlled efficacy study of a Klebsiella pneumoniae siderophore receptor protein (SRP) vaccine (Kleb-SRP), with a total of 569 cows and heifers enrolled. The study was designed to look at vaccine effect on Klebsiella mastitis; however, the SRP in Klebsiella are highly conserved across coliform bacteria, which means that the vaccine has potential for cross-protection against all coliforms. Cows were paired based on parity, days in milk at enrollment, and somatic cell count. Within pairs, individuals were randomized to receive either Kleb-SRP or a placebo formulation. Following vaccination, the incidence of Klebsiella spp. and total coliform mastitis from natural exposure were compared to determine the efficacy of the vaccine. When analyzing all cows, the reduction of mastitis risk was not significant, though milk production increased 0.31 kg/d and somatic cell counts were reduced by 20.1%. When administered before calving, the vaccine reduced the risk of Klebsiella and total coliform mastitis by 76.9 and 47.5% respectively; however, we observed no significant effect when administered after calving. The vaccine, when administered before calving, also increased milk production by an average of 1.74 kg/d and reduced somatic cell counts by 64.8%. When administered after calving, we noted a slight decrease in daily milk production (0.39 kg) but no significant effect on somatic cell counts. All cows in the study (including vaccinates and placebo) received multiple doses of a commercially available licensed Escherichia coli bacterin. It should be noted that this herd was chosen because of the high number of clinical Klebsiella clinical mastitis cases this herd experienced before the trial and the extreme environmental challenge that was present from bedding with dried manure solids. The data from this study demonstrate efficacy of the Kleb-SRP vaccine against Klebsiella mastitis alone and coliform mastitis in general (including all coliforms) when administered before the initiation of a lactation cycle.

Pharmacokinetics of multiple doses of transdermal flunixin meglumine in adult Holstein dairy cows

A transdermal formulation of the nonsteroidal anti-inflammatory drug, flunixin meglumine, has been approved in the United States and Canada for single-dose administration. Transdermal flunixin meglumine was administered to 10 adult Holstein cows in their second or third lactation at the label dose of 3.33 mg/kg every 24 hr for three total treatments. Plasma flunixin concentrations were determined using high-pressure liquid chromatography with mass spectroscopy (HPLC-MS). Pharmacokinetic analysis was completed on each individual animal with noncompartmental methods using computer software. The time to maximum drug concentration (Tmax) was 2.81 hr, and the maximum drug concentration was 1.08 μg/ml. The mean terminal half-life (T½) was determined to be 5.20 hr. Clearance per fraction absorbed (Cl/F) was calculated to be 0.294 L/hr kg^-1 , and volume of distribution of fraction (Vz/F) absorbed was 2.20 L/kg. The mean accumulation factor was 1.10 after three doses. This indicates changes in dosing may not be required when giving multiple doses of flunixin transdermal. Further work is required to investigate the clinical efficacy of transdermal flunixin after multiple daily doses.

Effects of transdermal flunixin meglumine on pain biomarkers at dehorning in calves

The objective of this study was to evaluate the analgesic properties of transdermal flunixin meglumine when given at the time of dehorning on pain biomarkers. Twenty-four weaned male Holstein calves, 6 to 8 wk of age were enrolled into the study. The calves were randomly assigned to 1 of 3 treatment groups: 1) transdermal flunixin and dehorn (DH-FLU); 2) transdermal flunixin and sham dehorn (SHAM-FLU); and 3) placebo and dehorn (DH-PLBO). Transdermal flunixin at a label dose of 3.33 mg/kg (or placebo at an equivalent volume) was administered as a pour-on along the top-line of the calves in each treatment group concurrently with electrocautery dehorning or sham dehorning. Biomarker parameters collected and analyzed included: infrared thermography (IRT), mechanical nociception threshold (MNT), plasma cortisol, and substance P (SP). There were no differences in maximal temperatures detected for the IRT measurements of the medial canthus of the eye for the DH groups. Mean control point MNT measurements at 48 h were 3.14 kgF, 3.46 kgF, and 1.43 kgF for the DH-FLU, Sham-FLU, and DH-PLBO groups, respectively (P = 0.0001). No other differences of MNT were detected between the dehorned groups for the other test sites and time points. Plasma cortisol reached peak concentration at 20 min postdehorning for the DH-FLU and DH-PLBO groups and 10 min for SHAM-FLU group. Peak plasma cortisol concentrations were 32.0 ng/mL, 12.7 ng/mL, and 28.8 ng/mL for the DH-FLU, SHAM-FLU, and DH-PLBO groups, respectively. Cortisol concentrations were lower for the DH-FLU group at 90 min postdehorning compared to the SHAM-FLU and DH-PLBO groups ( = 0.04). Area under the effect curve (AUEC) were similar for all groups ( = 0.93). No statistical differences in SP concentrations between groups were detected for any of the time points. In conclusion, transdermal flunixin meglumine given at the time of dehorning did not provide substantial analgesia based on the pain biomarkers investigated. Further investigation into its role as part of a multimodal analgesic plan is warranted.

Comparative plasma and interstitial fluid pharmacokinetics of flunixin meglumine and ceftiofur hydrochloride following individual and co-administration in dairy cows

Ceftiofur (CEF) and flunixin meglumine (FLU) are two drugs approved for use in beef and dairy cattle that are frequently used in combination for many diseases. These two drugs are the most commonly used drugs in dairy cattle in their respective drug classes. Two research groups have recently published manuscripts demonstrating altered pharmacokinetics of FLU and CEF in cows affected with naturally occurring mastitis. The objective of this study was to determine whether pharmacokinetics of flunixin meglumine administered intravenously or intramuscularly administered ceftiofur hydrochloride would be altered when co-administered versus individual administration to healthy dairy cattle. Ten cows were utilized in a three-period, three-treatment crossover design, with all cows receiving each treatment one time with a 10-day washout period between treatments. Following treatment, plasma and interstitial fluid samples were collected and stored for later analysis. Additionally, plasma ultrafiltrate was collected using microcentrifugation to determine plasma protein binding of each drug. Drug concentrations in plasma, plasma ultrafiltrate, and interstitial fluid were determined using high-pressure liquid chromatography coupled with mass spectrometry. The results of this trial indicate that drug interactions between FLU and CEF do not occur when the two drugs are administered simultaneously in healthy cattle. Further work is needed to determine whether this relationship is maintained in the presence of severe disease.

A study to examine the relationship between metritis severity and depletion of oxytetracycline in plasma and milk after intrauterine infusion

Metritis is a frequent problem in postpartum dairy cows. Intrauterine therapy with the antimicrobial oxytetracycline (OTC) is often used, although this therapy has not been shown to be superior to systemic therapy. The objectives of this study were to (1) determine the plasma and milk concentrations of OTC following intrauterine infusion in postpartum dairy cows with varying degrees of metritis severity; (2) determine the depletion time of OTC in an attempt to provide veterinarians withdrawal guidelines, should they use this therapy; and (3) correlate metritis severity scores with OTC concentrations in plasma and milk. Our hypothesis was that cows with more severe metritis would have higher OTC concentrations in milk following intrauterine therapy. Thirty-two cows were selected to participate in the study after farm personnel had determined that they had metritis based on evaluation of vaginal discharge between 4 and 14 DIM, in accordance with the farm's treatment protocols. Metritis scores (1-4) were assigned based on a published scheme: 1 represented yellow-to-orange thick discharge or translucent mucus with no fetid smell; 2 represented blood-tinged vaginal mucus, slightly watery, with little or no fetid smell; 3 represented red to red/brown watery discharge with moderate fetid smell; and 4 represented red to red/brown watery discharge containing pieces of placenta and an intense fetid smell. Trial cows received a single treatment of 4g of OTC (approximately 6.7mg/kg) via intrauterine infusion. Blood samples were collected over 96h, and milk samples were collected before intrauterine therapy and 3 times a day for 4 d following infusion. Following treatment, OTC rapidly diffused to plasma and subsequently to milk. Maximum OTC concentrations in plasma and milk occurred within the first 24h following intrauterine infusion, and 25 of the 32 cows had detectable OTC concentrations in milk at 4 d after intrauterine infusion. Cows with clinical metritis (metritis severity scores of 3 or 4) at the initiation of treatment were significantly and positively correlated with higher milk OTC concentrations at the second [time (T)9 h; r=0.43], fourth (T25 h; r=0.42), and fifth milking following treatment (T33 h; r=0.38) compared with cows with normal vaginal discharge. We also observed a positive correlation between initial metritis score and milk maximum concentration (r=0.36) and milk area under the concentration curve (r=0.36). Given that intrauterine administration of OTC is an extra-label therapy, dairy producers should consult with their veterinarian to ensure that milk is being tested at or below the established tolerance for OTC. This will ensure that violative drug residues do not enter the human food supply.

The pharmacokinetics of transdermal flunixin meglumine in Holstein calves

This study describes the pharmacokinetics of topical and intravenous (IV) flunixin meglumine in Holstein calves. Eight male Holsteins calves, aged 6 to 8 weeks, were administered flunixin at a dose of 2.2 mg/kg intravenously. Following a 10-day washout period, calves were dosed with flunixin at 3.33 mg/kg topically (transdermal). Blood samples were collected at predetermined times from 0 to 48 h for the intravenous portions and 0 to 72 h following topical dosing. Plasma drug concentrations were determined using liquid chromatography with mass spectroscopy. Pharmacokinetic analysis was completed using noncompartmental methods. The mean bioavailability of topical flunixin was calculated to be 48%. The mean AUC for flunixin was determined to be 13.9 h × ug/mL for IV administration and 10.1 h × ug/mL for topical administration. The mean half-life for topical flunixin was 6.42 h and 4.99 h for the intravenous route. The C_max following topical application of flunixin was 1.17 μg/mL. The time to maximum concentration was 2.14 h. Mean residence time (MRT) following IV injection was 4.38 h and 8.36 h after topical administration. In conclusion, flunixin when administered as a topical preparation is rapidly absorbed and has longer half-life compared to IV administration.

Elimination kinetics of cephapirin sodium in milk after an 8-day extended therapy program of daily intramammary infusion in healthy lactating Holstein-Friesian cows

The objective of this study was to determine the elimination kinetics of extended therapy with intramammary (IMM) cephapirin in lactating dairy cattle. Eight healthy Holstein-Friesian cows were administered cephapirin (200mg) into all 4 mammary glands every 24 h after milking. Cows were milked 3 times per day and concentrations of cephapirin and desacetyl cephapirin were determined in bucket milk using liquid chromatography-mass spectrometry. Milk concentration-time data after the last of the 8 IMM infusions were fitted using compartment and noncompartmental models. The maximum cephapirin concentration was 128±57 µg/mL (mean ± SD), the elimination rate constant from the central compartment was 0.278±0.046 (h(-1)), clearance was 0.053±0.023 L/h, the half time for elimination was 2.55±0.40 h, and the mean residence time was 2.65±0.79 h. The cephapirin concentration was below the approved tolerance in all cows by 96 h after the last infusion, which is the labeled withholding time for the preparation used. Extended therapy for 8 d provided milk cephapirin concentrations above the minimum inhibitory concentration for common gram-positive mastitis pathogens (0.1 to 1.0 µg/mL) for the duration of therapy and for an additional 16 to 32 h after the end of treatment. Our findings suggest that this IMM cephapirin sodium formulation, which is labeled for 2 doses 12 h apart, could be administered at a 24-h interval for up to 8 d in cows milked 3 times per day, with no significant effect on residue levels by 96 h after the last treatment. Longer withdrawal times would be prudent for cows with low milk production.

The role of thecal androgen production in the regulation of estradiol biosynthesis by dominant bovine follicles during the first follicular wave1,2

The first wave of follicular development following ovulation in cattle is characterized by selection and growth of a large, estrogenic dominant follicle. After the follicle becomes morphologically dominant, concentrations of estradiol in its follicular fluid decrease abruptly. The purpose of this study was to determine whether this decrease in estrogen production is caused by an insufficient supply of androgen from theca interna or decreased aromatization of androgen precursor by granulosa cells. Dominant follicles were collected from Holstein heifers on d 4, 6, or 8 of the first follicular wave (n = 5/d). Amounts of 17alpha-hydroxylase mRNA in theca interna were sevenfold higher (P < 0.01) on d 4 than on d 8. After 3 h in culture, secretion of androstenedione by theca interna collected on d 4 (236 +/- 44 pg/microg of protein) tended to be lower (P = 0.055) compared with d 6 (517 +/- 162 pg/microg protein) and was lower (P < 0.05) compared with d 8 (387 +/- 51 pg/microg of protein). In granulosa cells, amounts of aromatase mRNA decreased (P < 0.05) on d 8 compared with d 6 but not d 4. In vitro secretion of estradiol was higher in granulosa cells collected on d 4 (3.5 +/- 0.8 ng/[10(5) cells x 3 h]) compared with d 6 (1.8 +/- 0.6 ng/[10(5) cells x 3 h]; P < 0.05) and tended to be higher on d 4 than on d 8 (2.2 +/- 0.2 ng/[10(5) cells x 3 h]; P = 0.058). We conclude that the decrease in estradiol production observed during atresia of the dominant follicle is not due to lack of androgen substrate for aromatization or downregulated expression of the aromatase gene, but may be the direct result of decreased activity of the aromatase enzyme within granulosa cells.