40 NEBRASKA CATTLEMAN November 2025 bones that might otherwise be obvious earlier in the year. If not monitored and corrected, this can result in a late-gestation cow in the winter with a BCS less than 5 (on a scale of 1 to 10). This can make it difficult for her to maintain herself during the cold winter, putting her in a nutrient deficient for colostrum development for the subsequent calf and even jeopardize rebreeding the next spring. RAIN DURING HAYING IS A MIXED BLESSING Any producer who has been short on hay tonnage going into the winter due to drought knows what a blessing a wet year can be for hay production. Conversely, any producer who has tried to put hay down and get it cured and baled between rainstorms in a wet year knows how frustrating that can be. Much like forage in the pasture, a rainy year can yield more hay, but its quality may be lower than anticipated. Poorer quality hay may result not only from rapid growth and stem development, but also from rain delays in curing and baling. The resulting winter hay supply may not meet the nutrient demands of the cow that, because of delayed weaning while grazing poor-quality standing forage, may now need to gain condition rather than just maintain. NAVIGATING THE PITFALLS Lighter Calves Leaving calves on the cow longer may help the calf, but at the expense of the cow whose longevity is paramount to the operation’s success. Producers may want to consider weaning calves as normal and, if not selling immediately, providing hay or grazing with a supplement that targets the desired gain. Monitoring Body Condition Late summer is a good time to evaluate and assign BCS to lactating cows. Are they holding condition well? Do the plans for weaning need to be altered to WINTER PITFALLS OF SUMMER RAIN CONTINUED FROM PAGE 38 KEY POINTS • An increase in forage quantity often comes at the cost of forage quality. Lighter calf gains are often the result of forages growing rapidly and maturing quickly. While lengthening the nursing period may improve calf performance, it comes at a cost to the cow. • Assessing cow body condition and making a proactive plan for weaning or supplementation is helpful for staying out of a reactive situation. • A good year of rain is always a blessing. Proactively navigating the pitfalls associated with good rainfall can also be a blessing. • Sending hay samples to a commercial laboratory for quality assessment helps producers know which hay to feed at which stage of production, how much supplement to purchase and when to feed it. CONTINUED ON PAGE 42 RESFLOR GOLD®(florfenicol and flunixin meglumine) Intervet /Merck Animal Health PRODUCT INFORMATION Antimicrobial/Non-Steroidal Anti-Inflammatory Drug Approved by FDA under NADA # 141-299 300 mg/16.5 mg/mL Sterile For subcutaneous use in beef and non-lactating dairy cattle only. Not for use in female dairy cattle 20 months of age or older or in calves to be processed for veal. CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian. DESCRIPTION: RESFLOR GOLD® is indicated for treatment of bovine respiratory disease (BRD) associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis, and control of BRDassociated pyrexia in beef and non-lactating dairy cattle. INDICATION: RESFLOR GOLD® is indicated for treatment of bovine respiratory disease (BRD) associated with Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, and Mycoplasma bovis, and control of BRDassociated pyrexia in beef and non-lactating dairy cattle. DOSAGE AND ADMINISTRATION: RESFLOR GOLD® should be administered once by subcutaneous injection at a dose rate of 40 mg florfenicol/kg body weight and 2.2 mg flunixin/kg body weight (6 mL/100 lb). Do not administer more than 10 mL at each site. The injection should be given only in the neck. Injection sites other than the neck have not been evaluated. For the 500 mL vial, do not puncture the stopper more than 20 times *Do not administer more than 10 mL at each site. CONTRAINDICATIONS: Do not use in animals that have shown hypersensitivity to florfenicol or flunixin. WARNINGS: NOT FOR HUMAN USE. KEEP OUT OF REACH OF CHILDREN. This product contains material that can be irritating to skin and eyes. Avoid direct contact with skin, eyes, and clothing. In case of accidental eye exposure, flush with water for 15 minutes. In case of accidental skin exposure, wash with soap and water. Remove contaminated clothing. Consult a physician if irritation persists. Accidental injection of this product may cause local irritation. Consult a physician immediately. The Safety Data Sheet (SDS) contains more detailed occupational safety information. For customer service, adverse effects reporting, and/or a copy of the SDS, call 1-800-211-3573. For additional information about adverse drug experience reporting for animal drugs, contact FDA at 1-888-FDAVETS, or http://www.fda.gov/reportanimalae. PRECAUTIONS: As a class, cyclo-oxygenase inhibitory NSAIDs may be associated with gastrointestinal, renal, and hepatic toxicity. Sensitivity to drug-associated adverse events varies with the individual patient. Patients at greatest risk for adverse events are those that are dehydrated, on diuretic therapy, or those with existing renal, cardiovascular, and/or hepatic dysfunction. Concurrent administration of potentially nephrotoxic drugs should be carefully monitored. NSAIDs may inhibit the prostaglandins that maintain normal homeostatic function. Such antiprostaglandin effects may result in clinically significant disease in patients with underlying or pre-existing disease that have not been previously diagnosed. Since many NSAIDs possess the potential to produce gastrointestinal ulceration, concomitant use of RESFLOR GOLD® with other anti-inflammatory drugs, such as NSAIDs or corticosteroids, should be avoided or closely monitored. Flunixin is a cyclo-oxygenase inhibitory NSAID, and as with others in this class, adverse effects may occur with its use. The most frequently reported adverse effects have been gastrointestinal signs. Events involving suspected renal, hematologic, neurologic, dermatologic, and hepatic effects have also been reported for other drugs in this class. Not for use in animals intended for breeding purposes. The effects of florfenicol on bovine reproductive performance, pregnancy, and lactation have not been determined. Toxicity studies in dogs, rats, and mice have associated the use of florfenicol with testicular degeneration and atrophy. NSAIDs are known to have potential effects on both parturition and the estrous cycle. There may be a delay in the onset of estrus if flunixin is administered during the prostaglandin phase of the estrous cycle. The effects of flunixin on imminent parturition have not been evaluated in a controlled study. NSAIDs are known to have the potential to delay parturition through a tocolytic effect. RESFLOR GOLD®, when administered as directed, may induce a transient reaction at the site of injection and underlying tissues that may result in trim loss of edible tissue at slaughter. RESIDUE WARNINGS: Animals intended for human consumption must not be slaughtered within 38 days of treatment. This product is not approved for use in female dairy cattle 20 months of age or older, including dry dairy cows. Use in these cattle may cause drug residues in milk and/or in calves born to these cows. A withdrawal period has not been established in pre-ruminating calves. Do not use in calves to be processed for veal. ADVERSE REACTIONS: Transient inappetence, diarrhea, decreased water consumption, and injection site swelling have been associated with the use of florfenicol in cattle. In addition, anaphylaxis and collapse have been reported post-approval with the use of another formulation of florfenicol in cattle. In cattle, rare instances of anaphylacticlike reactions, some of which have been fatal, have been reported, primarily following intravenous use of flunixin meglumine. CLINICAL PHARMACOLOGY: The pharmacokinetics (PK) of florfenicol (Table 1) and flunixin (Table 2) after subcutaneous injection of RESFLOR GOLD® is described below: Table 1. Mean (n=28) pharmacokinetic parameters for florfenicol in cattle after a single subcutaneous administration of RESFLOR GOLD (florfenicol dose of 40 mg/kg BW). Mean Florfenicol PK parameters in Cattle PK Parameter AUC0-t1 (ng*hr/mL) AUC0-inf2 (ng*hr/mL) Cmax3 (ng/mL) Tmax4 (hr) T½5 (hr) MRT0-inf6 (hr) Mean 242527 247577 11151 6.25 28.5 27.3 SD7 42741 41391 4194 3.87 9.91 11.6 Table 2. Mean (n=28) pharmacokinetic parameters for flunixin in cattle after a single subcutaneous administration of RESFLOR GOLD® (flunixin dose of 2.2 mg/kg BW). Mean Flunixin PK parameters in Cattle PK Parameter AUC0-t1 (ng*hr/mL) AUC0-inf2 (ng*hr/mL) Cmax3 (ng/mL) Tmax4 (hr) T½5 (hr) MRT0-inf6 (hr) Mean 13370 14448** 1913 1.14 9.5** 11.4 SD7 4964 5116 791 0.97 3.27 4.41 MICROBIOLOGY: Florfenicol is a synthetic, broad-spectrum antibiotic active against many Gram-negative and Grampositive bacteria isolated from domestic animals. It acts by binding to the 50S ribosomal subunit and inhibiting bacterial protein synthesis. Florfenicol is generally considered a bacteriostatic drug, but exhibits bactericidal activity against certain bacterial species. In vitro studies demonstrate that florfenicol is active against the BRD pathogens M. haemolytica, P. multocida, and H. somni, and M. bovis that florfenicol exhibits bactericidal activity against strains of M. haemolytica and H. somni. The minimum inhibitory concentrations (MICs) of florfenicol were determined for non-mycoplasmal BRD isolates obtained from calves enrolled in BRD field studies in the U.S. in 2006 using methods recommended by the Clinical and Laboratory Standards Institute (M31-A2). MICs for M. bovis isolates were determined by an accepted method using Hayflick Broth with Alamar Blue (HBAN) medium under appropriate control. Isolates were obtained from pretreatment nasal swabs from all calves enrolled at all four sites, post-treatment nasal swabs from treatment failures in the RESFLOR GOLD® and saline control treatment groups at three sites, and lung tissue from one calf that died in the saline control treatment group. The results are shown in below Table 3. Table 3. Florfenicol MIC values* of indicated pathogens isolated from cattle with naturally-occurring BRD. Indicated pathogens Year of isolation Number of isolates MIC50** (μg/mL) MIC90** (μg/mL) MIC range (μg/mL) Mannheimia haemolytica 2006 183 1.0 1.0 0.5 to 32 Pasteurella multocida 2006 139 0.5 0.5 ≤0.125 to 16 Histophilus somni 2006 84 ≤0.125 ≤0.125 ≤0.125 to 0.25 Mycoplasma bovis 2006 60 1.0 1.0 0.5 to 1.0 * The correlation between in vitro susceptibility data and clinical effectiveness is unknown. ** The lowest MIC to encompass 50% and 90% of the most susceptible isolates, respectively. EFFECTIVENESS: In a multi-site field study, calves with naturally-occurring BRD were treated with RESFLOR GOLD®, Nuflor Gold (NADA 141-265), or saline. A treatment success was defined as a calf with normal respiration to mild respiratory distress, normal attitude to mildly depressed, and a rectal temperature < 104.0°F on Day 11. The treatment success rate for BRD for the RESFLOR GOLD® treatment group (68.4%) was statistically significantly greater (p = 0.0255) compared to the saline control treatment group (42.9%). RESFLOR GOLD was non-inferior to Nuflor Gold for the treatment of BRD, with a one-sided 95% lower confidence bound for the difference between the two treatments equal to -13.2%. In the same study, the change in rectal temperature from pre-treatment to six hours post- treatment was evaluated to determine the effectiveness of RESFLOR GOLD® for the control of BRD-associated pyrexia. The proportion of calves whose rectal temperatures decreased by ≥2.0 °F from pretreatment to six hours post-treatment was statistically significantly greater (p = 0.0019) in the RESFLOR GOLD® treatment group compared to the saline control treatment group. The mean decrease in rectal temperature from pre-treatment to six hours post- treatment was statistically significantly greater in the RESFLOR GOLD® treatment group compared to the Nuflor Gold and saline control treatment groups (p = 0.0031 and 0.0002, respectively). The effectiveness of RESFLOR GOLD® for the treatment of BRD associated with Mycoplasma bovis was demonstrated by examining the M. bovis data from cattle enrolled in the BRD treatment study described above. There were numerically more treatment successes (6 of 8 calves, 75%) than treatment failures (2 of 8 calves, 25%) in RESFLOR GOLD®-treated calves that cultured positive for M. bovis pre-treatment. ANIMAL SAFETY: A target animal safety study was conducted to evaluate the effects of RESFLOR GOLD® when administered to cattle subcutaneously at 1X, 3X, or 5X the labeled dose for three consecutive days (3X the labeled duration). Decreased feed and water consumption, and decreased body weights (secondary to decreased feed consumption) were observed in the 1X, 3X, and 5X groups. Injection site swellings were noted in the 1X, 3X, and 5X groups. A separate injection site study was conducted in cattle. The study demonstrated that RESFLOR GOLD®, when administered according to the label directions, may induce a transient local reaction in the subcutaneous and underlying muscle tissue. STORAGE INFORMATION: Do not store above 30°C (86°F). Use within 28 days of first use. HOW SUPPLIED: RESFLOR GOLD® is available in 100, 250, and 500 mL sterile, multiple-dose, glass vials. Formulated in Germany. Intervet Inc. (d/b/a Merck Animal Health), 2 Giralda Farms, Madison, NJ 07940 Copyright © 2022 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved Rev. 11/22 100mL Multiple-Dose Vial 397356 R2; 250mL Multiple-Dose Vial 385832 R2; 500mL Multiple-Dose Vial 398670 R2 CPN: 1047298.4 RESFLOR GOLD® Dosage Guide* Animal Weight (lbs) DOSAGE (mL) Recommended Injection Location 100 6.0 200 12.0 300 18.0 400 24.0 500 30.0 600 36.0 700 42.0 800 48.0 900 54.0 1000 60.0 1 AUC0-t = Area under the plasma-concentration-time curve (AUC) from time zero to the last quantifiable concentrations 2 AUC0-inf = AUC from time zero to infinity 3Cmax = Maximum plasma concentration 4Tmax = Time at which Cmax was observed 5T½ = Terminal elimination half-life 6 MRT0-inf = Mean residence time from time zero to infinity 7 SD = Standard deviation ** n=27 17444_MRKA_2025_AIF_ResflorGold_OneThird_2-32x9-856.indd 1 2025-10-01 9:41 AM
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