Dose Of Monensin Research Articles

Comparison of solubility profiles for pioneer and generic monensin premixes in biorelevant simulated intestinal fluid based on shake flask extractions.

In the United States, a generic Type A medicated article product can gain the FDA approval by demonstrating bioequivalence (BE) to the pioneer product by successfully conducting a blood level, pharmacodynamic, or clinical BE study. A biowaiver can be granted based on several criteria, assuming the dissolution of the test and reference products represents the only factor influencing the relative bioavailability of both products. Monensin is practically insoluble in H2O per the USP definition. Previously published data from a comparison study of monensin dissolution profiles from the pioneer product and four generic products using biorelevant media showed that generic monensin products demonstrated different dissolution profiles to the pioneer product in these USP biorelevant rumen media. This follow-up study compared the solubility profiles in simulated intestinal fluid (cFaSSIF, pH 7.5) for the pioneer product and four generic products. The generic monensin products demonstrated different invitro dissolution profiles to the pioneer product in biorelevant media. The differences demonstrated in solubility and dissolution profiles are of concern regarding the potential efficacy of generic monensin in cattle. There are also additional concerns for the potential development of Eimeria resistance in cattle receiving a sub-therapeutic dose of monensin from a less soluble generic product.

An updated meta-analysis of the anti-methanogenic effects of monensin in beef cattle.

Meta-analyses were performed to quantitatively summarize the effects of monensin on in vivo methane (CH4) production in beef cattle, and differentiate these outcomes according to dietary management, dose of monensin, and length of monensin supplementation. Data from 11 manuscripts describing 20 individual studies were used, and CH4 was converted to g/d when required. Studies were classified according to dose of monensin (mg/kg of diet dry matter), length of monensin supplementation prior to the last CH4 measurement, feeding management (ad libitum vs. limited-fed), and diet profile (high-forage or high-concentrate diets). Variance among studies were assessed using a χ² test of heterogeneity and calculated using I² statistics. The inclusion of monensin decreased (P < 0.01) CH4 production by 17.5g/d when all studies were analyzed together. A moderate (P < 0.01) heterogeneity (I² = 55%) was detected for CH4 production estimates between studies; thus, meta-analyses were performed within classes. The reduction in CH4 differed (P < 0.01) according to dose of monensin, as it decreased (P < 0.01) by 25.6g/d when the high recommended dose range was used (32 to 44mg/kg), and tended to decrease (P ≤ 0.07) by 9.7 and 13.5g/d when the moderate (≤31mg/kg) and above recommended (≥45mg/kg) doses were used, respectively. The reduction in CH4 also differed (P < 0.01) according to the length of monensin supplementation. Monensin decreased (P ≤ 0.05) CH4 production by 24.3g/d when supplemented for <15 d, by 15.4g/d when supplemented from 23 to 33 d, by 24.3g/d when supplemented from 52 to 79 d, and tended to decrease (P = 0.06) CH4 production by 3.21g/d when supplemented from 94 to 161 d. The reduction in CH4 did not differ (P = 0.37) according to diet profile, despite a 30% difference in reduction when monensin was added to high-forage (20.89g/d) compared with high-concentrate diets (14.6g/d). The reduction in CH4 tended to differ according to feeding management (P = 0.08), decreasing by 22.9g/d (P < 0.01) when monensin was added to diets offered ad libitum, and by 11.5g/d (P = 0.05) in limit-fed diets. Collectively, this study provides novel insights and further corroborates monensin as CH4 mitigation strategy in beef cattle operations. The most effective responses were observed during the first 79 d of monensin supplementation, and when monensin was included between 32 to 44mg/kg of diet, was added to high-forage diets, and added to diets fed ad libitum.

Effect of monensin on milk production efficiency and milk composition in lactating dairy cows fed modern diets

Since the US Food and Drug Administration's approval of monensin in 2004, significant nutritional advances have been made to increase feed efficiency and milk fat production. Recent evidence suggests monensin's adverse effect on milk fat percentage may be absent when diets are formulated to address known diet-induced milk fat depression risk factors. Thus, study objectives were to evaluate effects of monensin level on dry matter intake (DMI), milk production and composition, and efficiency of high-producing cows fed diets formulated to optimize milk fat. Ninety-six lactating Holstein cows (36 primiparous, 60 multiparous; 106 ± 17 d in milk [DIM]) were balanced by parity, DIM, and milk production and were randomly assigned to 1 of 12 pens with 8 cows per pen. All cows received 11 g/t monensin for 5 wk after which pens received 1 of 4 dietary treatments (n = 3) formulated to provide 0 (CON), 11 (R11), 14.5 (R14.5), or 18 (R18) g/t monensin for 9 wk. The basal diet was 54% forage, 27% NDF, 29% starch, and 2.3% rumen unsaturated fatty acid load. Pen was the experimental unit and data were analyzed using the Fit Model Procedure of JMP. Effects of treatment, time, and treatment × time interaction were included as fixed effects and pen as a random effect. Least squares means were determined and linear and quadratic contrasts were tested. Dry matter intake tended to decrease linearly with increasing monensin dose. Milk yield, fat percentage, and protein percentage and yield were unaffected by treatment while fat yield was quadratically increased. Milk de novo and mixed fatty acid (FA) yields (g/d) increased quadratically with monensin whereas preformed FA linearly decreased during the experimental period. Energy-corrected milk (ECM) was quadratically increased by monensin. Milk urea nitrogen concentrations increased linearly with increasing monensin dose. Monensin linearly increased feed efficiency (ECM/DMI, 3.5% fat-corrected milk/DMI, and solids-corrected milk/DMI). Body weight gain did not differ between treatments. Estimated dietary energy tended to increase linearly with increasing monensin level. These data suggest monensin improves component-corrected milk production efficiency, estimated dietary energy, and does not negatively affect milk fat percentage or FA profile.

Effect of the combined use of monensin with virginiamycin or bacitracin on beef cattle performance, liver gluconeogenesis, lipid metabolism and intramuscular fat content

The objective was to evaluate the combined use of monensin with virginiamycin or zinc bacitracin on performance, serum D-lactate, feeding behavior, carcass traits, and the expression of gluconeogenic and lipogenic genes over time in feedlot young bulls. Nellore × Angus (F1) young bulls (n = 72; BW 368 ± 16.3 kg) were used in a completely randomized design. Animals were stratified by BW and allotted into 18 pens with 4 animals each. Pens (6 pens per treatment) were randomly assigned to the following treatments: monensin (MON), monensin + zinc bacitracin (MONZB) and monensin + virginiamycin (MONVM). The doses of monensin, zinc bacitracin and virginiamycin were 18.9, 6.62 and 18.9 mg/kg DM of the diet, respectively. The diet consisted of 85% corn-based concentrate and 15% corn silage. The finishing phase was 109 days with the first 27 days for diet adaptation and the remaining 82 days for the finishing diet. Treatment additives did not affect body weight (BW), overall average daily gain (ADG), dry matter intake (DMI) or gain:feed (P ≥ 0.13). Animals fed MONVM had lesser (P = 0.03) intramuscular fat than those fed MON and MONZB. Serum D-lactate concentration was greater (P = 0.05) in MONVM animals than in MON and MONZB animals. In the liver, MONVM animals upregulated (P < 0.03) Pyruvate carboxylase (PC) and Lactate dehydrogenase A (LDHA) expression compared with MON and MONZB. The expression of Peroxisome proliferator-activated receptor gamma (PPARG) in LT tended to be decreased (P = 0.07) in MONVM animals than in MONZB. Animals fed MONVM downregulated (P = 0.03) Acetyl-CoA carboxylase alpha (ACACA) expression compared with those fed MON. In conclusion, these additives affect growth performance in different times during feedlot phase. The combined use of monensin and virginiamycin reduce lipogenesis and increase lipid oxidation, triggering lesser IMF deposition compared to monensin alone or combined with bacitracin.

Effects of monensin supplementation on lactation performance of dairy cows: a systematic review and dose–response meta‑analysis

The aim of this study was to conduct a comprehensive review with meta-analysis to determine the effects of the dose–response relationship between monensin supplementation and dairy cow performance and milk composition. Results from 566 full-text articles and 48 articles with 52 studies were meta-analyzed for pooled estimates. Monensin supplementation up to 23 ppm increased milk production, with the optimal dose being 12.6 ppm. Monensin supplementation at doses ranging from 16 to 96 ppm increased milk production in the prepartum phase (− 28 to 0 day relative to calving). From 60 to 150 DIM, monensin supplementation up to 21 ppm had a significant positive effect on this outcome, while supplementation in the 37 to 96 ppm range caused a decrease in this variable. At 0 to 60 and > 150 DIM, monensin supplementation had no effect on milk yield. At dosages of 22 to 96 ppm, 12 to 36 ppm, and below 58 ppm and 35 ppm, respectively, monensin supplementation resulted in significant decreases in dry matter intake (DMI), milk protein percentage, milk fat percentage, and milk fat yield. Overall, based on the results of this meta-analysis and considering all variables, the recommended optimal dose of monensin could be about 16 ppm.

Low doses of monensin for lambs fed diets containing high level of ground flint corn

Two experiments were proposed to evaluate the addition of monensin for lambs fed diets containing a high level of mature ground flint corn. The experimental diets were as follows: no inclusion of monensin (M0) and inclusion of 8 (M8), 16 (M16) and 24 mg kg–1 of monensin (M24). In experiment 1, eight cannulated wethers were divided into a double 4 × 4 Latin square experimental design to evaluate nutrient digestibility, plasma parameters and rumen fermentation. The experiment lasted 112 days, divided into four periods of 28 days each. In experiment 2, ninety-two lambs were used in a randomized block design to evaluate the performance over 56 days. In experiment 1, doses of monensin had no effect on nutrient intake (p ≥ 0.07) and digestibility (p ≥ 0.09). There was a quadratic effect for acetate molar proportion (p = 0.01), acetate to propionate ratio (p = 0.04) and rumen pH (p < 0.01). However, there was no effect on the molar proportion of propionate and butyrate. The monensin decreased linearly the total SCFA concentration (p < 0.01). The inclusion of monensin increased glucose (p < 0.01) and decreased lactate concentration in plasma (p = 0.05). In experiment 2, monensin decreased dry matter intake (p = 0.04). However, there was a quadratic effect for average daily gain (p = 0.03) and feed efficiency (p < 0.01), with the greatest values observed for the M8 diet. Thus, the inclusion of 8 mg kg–1 of dry matter diet (DM) improves ruminal fermentation and plasma parameters, resulting in greater growth performance in lambs.

Comparison of Two Commercially Available Immunoassays for the Measurement of Bovine Cardiac Troponin I in Cattle With Induced Myocardial Injury

Background: Multiple cardiac troponin I (cTnI) immunoassays are commercially available. Overall, assays have not been standardized, and inter-assay differences in the detection of the analyte cardiac troponin I can be clinically relevant.Objective: To compare the diagnostic accuracy of the commercially available Abbott i-STAT®1 cTnI immunoassay (i-STAT) and the previously validated ADVIA Centaur TnI-Ultra immunoassay (Centaur) in cattle.Hypothesis: There will be significant differences in bovine serum cTnI results measured by the Centaur and i-STAT methods.Animals: Ten dairy cows with experimentally induced myocardial injury due to monensin administration. Thirty apparently healthy dairy cows with no history of monensin exposure served as controls.Methods: Blood was collected at various time points after administration of a single dose of monensin (20 to 50 mg/kg) via orogastric tube. A total of 112 blood samples were collected. Cardiac TnI concentration was analyzed with the two methods and the association between methods analyzed via linear regression. Bland-Altman analysis to evaluate agreement between methods was performed on samples divided into groups (cTnI < 1.0 ng/mL and cTnI ≥ 1.0 ng/mL).Results: Analyzer results were linearly correlated with each other (R2 = 0.931). Samples with cTnI concentrations <1.0 ng/mL had a bias of −0.13 ± 0.20 ng/mL and samples with cTnI concentrations >1.0 ng/mL had a bias of −9.81 ± 13.26 ng/mL.Conclusions and clinical importance: The results of this study reveal that cTnI concentrations determined with the i-STAT are systematically lower compared to the concentrations determined by the Centaur.

Effects of monensin dose from a self-fed mineral supplement on performance of growing beef steers on forage-based diets

ABSTRACT Objective The objective of this research was to determine the effect of differential monensin (Rumensin, Elanco Animal Health, Greenfield, IN) intake in a free-choice loose mineral on performance of grazing beef steers. Material and Methods Treatments consisted of offering ad libitum access to minerals (AMPT-A, ADM Animal Nutrition, Quincy, IL) supplying 0 (0M), 882 (800M), or 1,764 (1600M) g of monensin/t with targeted daily monensin intakes of 0, 100, or 200 mg of monensin per steer. Steer calves (n = 605, BW = 278 ± 27 kg) were fed hay with a hand-fed supplement (block 1); grazed wheat (Triticum aestivum) pasture (blocks 2, 3, and 6); or bermudagrass (Cynodon dactylon) pasture (blocks 4 and 5). There were no treatment × diet interactions (P ≥ 0.97); therefore, data were pooled across blocks for statistical analysis. Results and Discussion Steers offered 800M and 1600M had greater (P ≤ 0.02) final BW, ADG, and total BW gain compared with 0M steers fed mineral without monensin. Mineral intake decreased linearly (P Implications and Applications Monensin supplementation improved growth performance compared with an unmedicated control within the doses observed in this experiment and regardless of basal forage quality. Intake of a self-fed monensin-containing mineral can be decreased by at least 50% without affecting performance response to monensin of steers on forage-based diets.

Acute, subacute and chronic sequelae of horses accidentally exposed to monensin-contaminated feed.

Monensin is highly toxic to horses and inadvertent ingestion can result in cardiac injury and death. To describe sequelae of monensin ingestion and to determine clinical predictors of outcome. Observational clinical study. Physical examination, electrocardiogram and echocardiography were performed on 76 horses accidentally exposed to monensin-contaminated feed. Four horses were examined within 14days of exposure (acute period), 29 horses were examined between 15 and 45dayspost-exposure (subacute period) and 70 horses were examined 4-10months after exposure (chronic period). Follow-up information was obtained for 56 horses by telephone interviews approximately 16months after exposure. Cardiac abnormalities were detected in 4/4, 19/29 and 31/70 horses during the acute, subacute and chronic periods, respectively. Sixteen months post-exposure, 34 of the 64 horses (53%) for which the outcome was known had returned to their previous use, 13 (20%) were reported to be exercise intolerant, three (5%) were retired and 14 (22%) were dead (two deaths, 12 euthanasia). Thinning of the myocardium observed at any point in time was associated with a negative outcome. Heterogeneity of the myocardium observed in the acute/subacute period was associated with a negative outcome while subjective contractile intraventricular dyssynchrony, cardiac chamber dilation, decreased fractional shortening and multiple premature ventricular complexes observed in the chronic period were associated with a negative outcome. Some horses with significant changes associated with a negative outcome in the chronic phase still returned to their previous work. No control group and only 27 horses were examined more than once. Clinical outcome of horses exposed to sublethal doses of monensin is highly variable. The presence of heterogeneity and thinning of the myocardium shortly after intoxication were associated with a negative outcome.

An energy and monensin supplement reduces methane emission intensity of stocker cattle grazing winter wheat

ABSTRACT Objective The objective of this study was to determine the effect of an energy supplement with monensin on CH4 emissions and performance of stocker calves grazing winter wheat. Materials and Methods Eight steers and 8 heifers were grazed in a 9-ha winter wheat pasture, and CH4 emissions were recorded. Animals were randomly assigned within sex to receive from 0 to 1.07 kg of a supplement (as fed, primarily ground corn, wheat middlings, and 34 mg/kg monensin) per day. Animals were supplemented 3 d per week in individual stalls and orts were weighed. Forage intake was estimated with TiO2 as an external marker. As several independent variables were available, dependent variables of interest were subjected to backward stepwise regression with baseline CH4, total supplement intake, forage intake, initial BW, sex, and monensin dose in the model. Results and Discussion Animal performance increased, but at a decreasing rate, with increased total supplement intake and forage intake (P Implications and Applications Taken together, these results suggest that supplementation with energy and monensin likely reduces methane emission intensity, and provide equations useful for future modeling efforts.

LEMON GRASS ESSENTIAL OIL (CYMBOPOGUM FLEXUOSUS) IN HIGH-CONCENTRATE DIETS FOR LAMBS

The objective of this study was to evaluate the effect of the inclusion of two doses of monensin and lemon grass essential oil ( Cymbopogum flexuosus ) on nutrient intake and digestibility, ruminal fermentation and ingestive behavior of lambs fed a high-concentrate diet. Four ruminally cannulated ram lambs (44.7 ± 3.72 kg of BW and approximately 5 mo. old) in a 4 x 4 Latin square experimental design were used. The control diet (CONT) contained 15% of oat hay, 85% of concentrate and no additives. In the remaining diets it was included 12.5 (12.5MON) or 25.0 (25MON) mg/kg of monensin (as-fed basis) or 1 mL/kg of DM of lemon grass essential oil (EO). The treatments had no effect on the nutrient intake and digestibility. The lambs that received the EO treatment showed a higher ruminal pH in comparison to those that received the control diet. However, they did not differ from treatments with monensin. A quadratic response was observed for ruminal pH, with the highest value observed in the animals fed the diet 12.5MON. The lambs fed EO had a higher ruminal concentration of acetate than the diet with monensin. There was a quadratic response of monensin on ruminal concentration of acetate, with the lowest value observed for 12.5MON. The acetate:propionate ratio was lower in lambs fed 12.5MON compared to the control. EO decreased the ruminal concentration of butyrate; however, its concentration was higher in lambs fed monensin than EO diets. A lower concentration of total short chain fatty acids (SCFA) was observed in lambs fed 12.5MON. The alanine aminotransferase (ALT) blood concentration was higher in the lambs fed EO compared to the control. EO increased rumen concentration of blood glucose compared to the treatments containing monensin and decreased the number of eggs per gram of feces (EGF). In addition, there was a quadratic response of monensin on the EGF, with a higher value in the lambs fed 12.5MON. In conclusion, half of the daily dose of monensin was more effective at increasing ruminal pH than the full dose, with no negative reflection on nutrient intake and digestibility, as well as on the ingestive behavior and parasitic load of the animals. Thus, 12.5MON may be indicated for lambs feed high concentrate diet. EO proved to be a good natural source to replace ionophores in diets for lambs.

Different doses of sodium monensin on feedlot performance, carcass characteristics and digestibility of Nellore cattle

The objective of this study was to determine the effects of different doses of sodium monensin on feedlot performance, carcass characteristics and nutrient digestibility of Nellore cattle. The experiment was designed as a completely randomized block, replicated 12 times, in which 60 20-months old yearling Nellore bulls (402.52 ± 33.02 kg) were fed in individual pens for 84 days according to the different doses of monensin expressed in ppm (dry matter basis): 0, 9, 18, 27 and 36. As doses of monensin increased, final body weight, average daily gain, gain-to-feed ratio, and dressing percentage were affected cubically (P &lt; 0.03), where animals fed 9 ppm of monensin presented greater average daily gain and better gain-to-feed ratio. Likewise, as dose of monensin increased, dry matter intake, hot carcass weight, and neutral detergent fiber and fecal starch digestibility in finishing period decreased linearly (P &lt; 0.05). In addition, neutral detergent fiber digestibility in adaptation period in creased linearly (P = 0.01) as doses of monensin increased. Thus, based on the results of this study, if monens in is going to be included in finishing diets for feedlot Nellore cattle, the dose of 9 ppm should be considered as the most feasible option.

Short communication: Field study to investigate the associations between herd-level risk factors for milk fat depression and bulk tank milk fat percent in dairy herds feeding monensin

Fat is the most variable milk component, and maintaining milk fat continues to be a challenge on commercial dairy farms. Our objectives were to establish associations between herd-level risk factors for milk fat depression and bulk tank milk fat content in commercial dairy herds feeding monensin. Seventy-nine Holstein commercial dairy herds in the northeast and Upper Midwest United States were enrolled in an observational study. Data were collected on herd characteristics, total mixed ration (TMR) samples, all component silage samples, and bulk tank milk samples. The unconditional univariable association of each explanatory variable and bulk tank milk fat percentage was evaluated using simple linear regression and multivariable regression models. Milk fat content of trans-10 C18:1 had an exponentially negative relationship to herd milk fat percentage. In general, milk fat content of fatty acids synthesized de novo in the mammary gland were positively related to herd milk fat, and the content of several trans-C18:1 fatty acids, which would be products of alternate pathways of ruminal biohydrogenation, were negatively related to herd milk fat. Variables related to TMR composition did not have univariable relationships with herd milk fat percentage. Herds that had >49.8% of the TMR particles on the middle screen of the Penn State particle separator had higher milk fat percentage than those with ≤49.8%, and herds with >54.0% of TMR particles in the bottom pan had lower milk fat percentage than herds with ≤54.0%. Dietary content of monounsaturated fatty acids (C16:1 and C18:1) had negative relationships with herd milk fat percentage; however, no single diet component accounted for more than 11% of the variation in herd-level milk fat percentage. Univariable monensin dose was not associated with herd milk fat percentage. The relative lack of significant univariate relationships with herd-level milk fat suggests many factors contribute to milk fat content, and herds experiencing low milk fat will need to examine many potential risk factors when working to troubleshoot this challenge.

The effects of monensin in diets fed to finishing beef steers and heifers on growth performance and fecal shedding of Escherichia coli O157:H7.

Two experiments were conducted to study the effects of monensin dose on growth performance and O157:H7 shedding in finishing beef cattle. In Exp. 1, 198 heifers (298 ± 1.1 kg BW) were allocated to 1 of 2 treatments consisting of 1) 200 mg/heifer daily of monensin and 2) 400 mg/heifer daily of monensin and fed for 151 d. In Exp. 2, 199 steers (430 ± 1.9 kg BW) were stratified by BW and allocated to 1 of 2 treatments consisting of 1) 0 mg/steer daily of monensin and 2) 400 mg/steer daily of monensin and fed for 128 d. For both experiments, there were 4 pen replicates per treatment. For Exp. 1 and Exp. 2, the model included the fixed effect of treatment for growth performance measures and the fixed effects of treatment, time, and treatment × time interaction, respectively, for O157:H7 shedding. In Exp. 1, final BW was 1.9% greater for heifers fed 400 mg/d monensin than for heifers fed 200 mg/d monensin ( = 0.05). Furthermore, ADG was 4.9% greater ( = 0.05) and G:F was 3.1% greater ( = 0.04) when the heifers were fed 400 mg/d monensin vs. 200 mg/d monensin. Pen prevalence for O157:H7 ( = 0.96) and the percentage of animals in the pen shedding O157:H7 at enumerable levels ( = 0.82) did not differ between heifers fed 200 mg/d monensin and heifers fed 400 mg/d monensin over the 4 sampling periods. For Exp. 2, steers fed the supplement containing monensin had a 1.9% greater final BW ( = 0.04) and a 5.2% greater ADG ( = 0.02) than steers fed a control supplement without monensin. No differences in DMI or G:F were noted across the treatments ( ≥ 0.14). O157:H7 percentage of enumerable cattle within the pen was greater for the steers fed monensin than the control steers not fed monensin than the control steers not fed monensin ( = 0.02) over the 4 sampling periods. However, the percentage of animals in the pen shedding O157:H7 (prevalence positive) did not differ between treatments ( = 0.18), nor did the average fecal counts ( = 0.45). In conclusion, feeding a higher dose (400 mg/d) of monensin improved final BW and ADG compared with a low dose of monensin or a no-monensin control in steers and heifers across multiple years. The percentage of animals shedding O157:H7 at enumerable levels was greater for steers fed the monensin supplement than for steers fed the control supplement, yet the presence of monensin, irrespective of the dose, did not affect the percentage of animals in the pen shedding O157:H7.

0210 Effects of spices on in vitro enteric methane production

This experiment was conducted to study the effects of spices (Rosmarinus officinalis, RO and Allium cepa, OP) on in vitro rumen fermentation, methane production and digestibility of corn silage-based ration. A corn silage-based total mixed ration (TMR; 0.5 g/sample) for dairy cows was treated with each of the spices at doses of 0 (Control), 5 (Low), 10 (Med) and 15% (High) of the TMR or with monensin (1.2 mg/g of TMR). Each mixture was incubated in triplicate in 50 mL of a rumen fluid-buffer inoculum (ratio 1:2) in a 120-mL gas-tight culture bottle at 39°C for 24 h in each of two runs. In vitro DM digestibility (DMD), fermentation parameters, gas and methane production were measured. Data were analyzed using the GLIMMIX procedure of SAS. The high dose of RO decreased DMD and acetate-propionate ratio relative to the Control, whereas, all doses of OP increased DMD and decreased acetate-propionate ratio relative to Control and monensin treatments. Gas volume (mL/g DM) and methane (mL/g DMD) were reduced (P < 0.05) by the High dose of RO and monensin, but not by Low and Med doses, relative to the control. Compared with monensin, adding OP at Low, Med and High doses reduced (P < 0.05; mL/g DMD) the gas volume (158 vs. 140, 136 vs. 110) and methane production (13.48 vs. 9.98, 9.46, and 10.38), respectively. Ruminal pH was increased by monensin and reduced by the High dose of OP. In conclusion, the High rate of Rosmarinus officinalis reduced methane production but decreased TMR digestibility whereas, all doses of of Allium cepa reduced methane production and increased TMR digestibility compared with the control and monensin treatments.

The effect of monensin concentration on dry matter intake, ruminal fermentation, short-chain fatty acid absorption, total tract digestibility, and total gastrointestinal barrier function in beef heifers.

In a 4 × 4 Latin square design (24-d periods), 4 ruminally cannulated Hereford × Angus/Simmental heifers were used to evaluate the effect of increasing levels of monensin concentration on DMI, ruminal fermentation, short-chain fatty acid (SCFA) absorption across the reticulorumen, and total tract barrier function. Heifers were fed a barley-based finishing diet (76% rolled barley grain, 12% barley silage, 8% mineral and vitamin supplement, and 4% canola meal) containing 0, 22, 33 or 48 mg/kg monensin. Urinary recovery of Cr-EDTA was used as an indicator of total tract barrier function (d 18 to 20). Days 20 to 23 were used to evaluate ruminal fermentation and total tract digestibility measurements, and SCFA absorption was measured using the temporarily isolated and washed reticulorumen technique on d 24. Data were analyzed using PROC MIXED of SAS with linear and quadratic contrasts to evaluate the effect of increasing monensin dose. Increasing monensin linearly decreased DMI (10.0, 9.9, 9.3, and 9.1 kg/d for diets containing 0, 22, 33 or 48 mg/kg monensin, respectively; = 0.01) but did not affect the variation in DMI among days. Urinary Cr-EDTA recovery was not ( ≥ 0. 61) affected by increasing dose of monensin, nor was ruminal pH (mean, minimum, maximum, duration less than 5.5, and area under curve; ≥ 0.21). The acetate-to-propionate ratio linearly decreased (1.9, 1.8, 1.4, and 1.3 for diets containing 0, 22, 33 or 48 mg/kg monensin, respectively; = 0.03) with increasing monensin. There was no response ( ≥ 0. 17) for the rate of SCFA absorption with monensin concentration. Total tract ethanol soluble carbohydrate digestibility linearly increased (77.2, 84.7, 88.0, and 94.0% for diets containing 0, 22, 33 or 48 mg/kg monensin, respectively; = 0.003) whereas starch digestibility quadratically responded (93.8, 93.9, 88.0, and 94.0% for diets containing 0, 22, 33 or 48 mg/kg monensin, respectively; < 0.001), where 33 mg/kg inclusion of monensin had a minimal value. The results from this study indicate that in addition to the known effects of monensin to reduce DMI and the acetate:propionate ratio, monensin inclusion does not affect ruminal pH, SCFA absorption, or total tract barrier function.

Serum, milk, and tissue monensin concentrations in cattle with adequate and potentially toxic dietary levels of monensin: pharmacokinetics and diagnostic interpretation.

Used in both beef cattle and dairy cows, monensin can provide many health benefits but can, when unintended overexposures occur, result in adverse effects. Information on serum and tissue concentrations following overexposure and/or overt toxicosis which may aid in diagnostics and clinical outcome is lacking. The aim of this study was to determine concentrations of monensin in biological specimens following oral exposure for 10days to an approved dose (1mg/kg) and a higher dose (5mg/kg) of monensin given daily on a body weight basis to 10 dairy cows. No deaths were reported; cows receiving 5mg/kg showed early signs of toxicosis including depression, decreased feed intake, and diarrhea after 4days of exposure. Histopathological findings were minimal in most cows. Pharmacokinetic modeling of the detected serum concentrations for the 1 and 5mg/kg dose groups determined the Cmax , Tmax, and t1/2λ to be 0.87 and 1.68ng/mL, 2.0 and 1.0h, and 1.76 and 2.32days, respectively. Mixed regression models showed that the dose level and days since last dose were significantly associated with monensin concentrations in all four tissues, and with cardiac troponin levels. The high dose resulted in a significant elevation of monensin in tissues at approximately 4.7 times compared to the monensin concentrations in the tissues of animals from the low-dose group. The cTnI concentrations in the high-dose group were 2.1 times that of cTnI in the low-dose group. Thus, the ability to diagnose monensin overexposure and/or toxicosis will improve from knowledge of biological monensin concentrations from this study.

Effects of different doses of sodium monensin on feeding behaviour, dry matter intake variation and selective consumption of feedlot Nellore cattle

The experiment was designed to determine the effects of different doses of sodium monensin (MON) on feeding behaviour, dry matter intake (DMI) variation and selective consumption of feedlot Nellore cattle. The experiment was a randomised complete block design, replicated 12 times, in which 60 20-month-old yearling Nellore bulls (402.52 ± 33.0 kg) were fed the following different doses of MON (expressed in mg per kg, on a DM basis) in individual pens for 84 days: 0, 9, 18, 27 and 36. The adaptation program consisted of ad libitum feeding of two adaptation diets over a period of 14 days with concentrate level increasing from 68% to 84% of diet DM. Orthogonal contrasts were used to assess linear, quadratic, cubic and quartic relationships between doses of MON and the dependent variable. As the dose of MON increased, the time spent ruminating (P &lt; 0.01), feeding efficiency of DM (P &lt; 0.05) and feeding efficiency of neutral detergent fibre (NDF; P &lt; 0.05) were affected linearly during the period of adaptation. For the finishing period, as the dose of MON increased, time spent eating and ruminating, and feeding efficiency of DM were affected quadratically (P &lt; 0.05), in which animals fed 9 ppm of MON presented better feeding efficiency of DM. Thus, as animals fed 9 ppm of MON presented better feeding efficiency of DM and NDF during the adaptation and finishing periods, it should be the dose of choice for feedlot Nellore cattle.

Biofilm formation of Clostridium perfringens and its exposure to low-dose antimicrobials.

Clostridium perfringens is an opportunistic pathogen that can cause food poisoning in humans and various enterotoxemia in animal species. Very little is known on the biofilm of C. perfringens and its exposure to subminimal inhibitory concentrations of antimicrobials. This study was undertaken to address these issues. Most of the C. perfringens human and animal isolates tested in this study were able to form biofilm (230/277). Porcine clinical isolates formed significantly more biofilm than the porcine commensal isolates. A subgroup of clinical and commensal C. perfringens isolates was randomly selected for further characterization. Biofilm was found to protect C. perfringens bacterial cells from exposure to high concentrations of tested antimicrobials. Exposure to low doses of some of these antimicrobials tended to lead to a diminution of the biofilm formed. However, a few isolates showed an increase in biofilm formation when exposed to low doses of tylosin, bacitracin, virginiamycin, and monensin. Six isolates were randomly selected for biofilm analysis using scanning laser confocal microscopy. Of those, four produced more biofilm in presence of low doses of bacitracin whereas biofilms formed without bacitracin were thinner and less elevated. An increase in the area occupied by bacteria in the biofilm following exposure to low doses of bacitracin was also observed in the majority of isolates. Morphology examination revealed flat biofilms with the exception of one isolate that demonstrated a mushroom-like biofilm. Matrix composition analysis showed the presence of proteins, beta-1,4 linked polysaccharides and extracellular DNA, but no poly-beta-1,6-N-acetyl-D-glucosamine. This study brings new information on the biofilm produced by C. perfringens and its exposure to low doses of antimicrobials.

Effects of different doses of sodium monensin on rumen papillae and tissue histology of feedlot Nellore cattle

The experiment was designed to determine the effects of different doses of sodium monensin (MON) on rumen papillae and tissue histology of feedlot Nellore cattle. The experiment was designed as a completely randomised block, replicated 12 times, in which 60 20-month-old yearling Nellore bulls (402.52 ± 33.0 kg) were fed in individual pens for 84 days according to the following doses of MON expressed in ppm (on a dry-matter basis): 0, 9, 18, 27 and 36. The adaptation program consisted of ad libitum feeding of two adaptation diets over a period of 14 days, with concentrate level increasing from 68% to 84% of diet dry matter. Orthogonal contrasts were used to assess linear, quadratic, cubic and quartic relationships between doses of MON and the dependent variable. No significant (P &gt; 0.10) MON effect was observed for number of papillae, mean papillae area, papillae area as a percentage of absorptive surface and rumenitis incidence. However, as the dose of MON increased, the absorptive surface area, papillae surface area and mitotic index were affected (P &lt; 0.05) cubically, in which animals fed 9 and 36 ppm presented larger absorptive surface area and greater number of cells in mitosis. Thus, based on the results, feeding of MON affected rumen papillae and tissue histology of feedlot Nellore cattle. The doses of 9 or 36 ppm of MON should be considered as the most feasible options, because they promote better development of rumen epithelium.