Comparison effect of lasalocid, diclazuril, probiotic and symbiotic on histomorpholical changes of small intestine induced by E. tenella

This study aimed to investigate the comparison of effect of anticoccidal drugs including lasalocid and diclazuril with probiotic and synbiotic on the growth performance and intestinal morphology in broiler chicken. One hundred eighty chickens (Ross 308, 1 day old) were randomly divided into 6 equal groups (n=30) including the negative control (basal diet), the positive control (basal diet+oral inoculation of 3×104 sporulated oocytes of E. tenella, and four treatment groups. At days of 28 and 49 of age, 9 chickens were blindly chosen from each group were scarified by decapitation and their various segments of small intestine including ileum, jejunum, and duodenum were evaluated histomorphologically. We found that the economic losses resulted from coccidial infection in the poultry industry are caused by the decreased performance of broiler chicken induced by morphological changes in the any three segments specially jejunum. The anticoccidial drugs, synbiotic and probiotic can partially prevent morphological changes in any three segments of small intestine in broiler chicken with coccidiosis. Since morphological changes in the jejunum begin earlier than in other parts and surface area of jejunal villi is important for nutrition absorbance as well as growth performance, lasolacid was found to a be more efficient treatment in this regard.

Lasalocid immediately and completely prevents the myocardial damage caused by coronary ischemia reperfusion in rat heart

Lasalocid, a specific mobile membrane ionophore for calcium, dopamine and norepinephrine was assayed in its capacity to reduce or maintain unaltered the cardiovascular function in conditions of imminent myocardial injury. In experiments of coronary blockade and reperfusion carried out in rat heart, it was found that when administered from 5 to 30 minutes prior to the induction of coronary blockade, at a concentration of 2 mg/kg of body weight, the ionophore immediately, simultaneously, and completely interrupts the blood pressure decay, cardiac frequency increase, electrical ventricular tachycardia and fibrillation, as well as the fall of mitochondrial oxidative phosphorylation and decay of mitochondrial oxygen uptake provoked by the induced myocardial injury. It appears that the molecular mode of action of the lasalocid is associated with its unique ability to transport both calcium and the catecholamines, dopamine and norepinephrine, across mitochondrial and bimolecular lipid membranes, as well as through synaptic cell membrane terminals from rat heart, myocardial fibers of the heart and heart chromaffin membrane vesicles. It is suggested that for the potential medical use of lasalocid to detain incoming ischemic myocardial damage, there exists a need to develop a personal electronic device able to simultaneously monitor, detect, and inform on the very early and simultaneous signs of cardiac alterations of electrical, mechano-chemical, metabolic and hydraulic nature, all which precede heart failure and to administer the lasalocid.

Effects of dried distiller's grains and lasalocid inclusion on feedlot lamb growth, carcass traits, nutrient digestibility, ruminal fluid volatile fatty acid concentrations, and ruminal hydrogen sulfide concentration

Our hypothesis was that increasing the inclusion level of dried distiller's grains with solubles (DDGS) to feedlot lambs would increase growth and the inclusion of lasalocid (LAS; Bovatec, Alpharma, LLC, Bridgewater, NJ) would increase ADG and G:F, while not affecting digestibility, ruminal VFA concentration, and ruminal pH. Furthermore, we hypothesized that rations containing LAS and higher levels of DDGS would cause increased ruminal hydrogen sulfide gas (HS) concentrations. Two hundred forty crossbred (Suffolk × Rambouillet) lambs (31.9 ± 5.87 kg BW; approximately 90 d of age) were allocated to 6 treatments in a completely randomized design with a 3 × 2 factorial arrangement of treatments. Lambs were placed into 24 feedlot pens (4 pens/treatment; 10 lambs/pen) for a 111 d finishing study. Main effects included concentration of DDGS (0, 15, or 30% DM basis) and inclusion of LAS (0 or 22.05 g/metric ton LAS) resulting in treatments of: 1) 0% DDGS without LAS (0DDGS-NL), 2) 0% DDGS with LAS (0DDGS-L), 3) 15% DDGS without LAS (15DDGS-NL), 4) 15% DDGS with LAS (15DDGS-L), 5) 30% DDGS without LAS (30DDGS-NL), and 6) 30% DDGS with LAS (30DDGS-L). Two-day weights were taken at the beginning and end of the experiment. Two-hundred-eighteen lambs (64.8 ± 7.99 kg BW) were slaughtered on d 112 at a commercial abattoir and carcass data collected. The inclusion of LAS increased ( ≤ 0.02) final BW, ADG, G:F, and HCW. As DDGS in the ration increased to 30%, DMI decreased linearly ( = 0.03) while G:F increased linearly ( = 0.03). A second study was conducted utilizing the same treatments to evaluate N and S balance, ruminal VFA and H2S concentration, and ruminal pH in 24 crossbred wethers (Suffolk × Rambouillet; 41.2 ± 12.23 kg BW). Daily urinary sulfur excretion and ruminal H2S concentration were linearly increased ( < 0.001) as DDGS increased in the ration. Total ruminal VFA concentration linearly decreased ( = 0.002) as DDGS increased in the ration. The inclusion of LAS increased ( = 0.02) ruminal pH. The results confirm our hypothesis that LAS increased overall growth and increasing DDGS increased ruminal HS concentration but did not influence growth. We reject the hypothesis that the combined effects of LAS and DDGS would have no effect on rumen pH and VFA concentrations.

Lasalocid induces cytotoxic apoptosis and cytoprotective autophagy through reactive oxygen species in human prostate cancer PC-3 cells

Lasalocid is an antibiotic from the group of carboxylic ionophores, produced by Streptomyces lasaliensis. But there was limited information of lasalocid on human prostate cancer cells. In the present studies, to better understand its effect in human prostate cancer cells, apoptosis and autophagy associated with possible signal pathways in vitro was examined. Our study showed that lasalocid mediated cell cycle arrest in G₀/G₁ phase by reducing G₁ phase dependent proteins, indicating entering into apoptotic cell death pathway. Lasalocid-induced apoptosis was involved with reactive oxygen species (ROS) production, and mitochondrial hyperpolarization. In addition, lasalocid induced autophagy through microtubule-associated protein 1 light chain 3 (LC-3)-II conversion, acidic vesicular organelles formation and GFP-LC-3 punctuate, which was inhibited by 3-methyladenine (3-MA), a widely used pharmacological inhibitor of autophagy. Furthermore, the autophagic phenomena were mediated by production of ROS, confirming that inhibition of ROS with N-acetyl-l-cysteine, a ROS inhibitor, attenuated lasalocid-triggered autophagy. Inhibition of autophagy with 3-MA enhanced the lasalocid-induced apoptosis through enhanced ROS generation. Taken together, lasalocid should be useful in the search for new potential chemotherapeutic agents for understanding the molecular mechanisms of anticancer in prostate cancer cells.

A meta-analysis of lasalocid effects on rumen measures, beef and dairy performance, and carcass traits in cattle

The effects of lasalocid on rumen measures, beef and dairy performance, and carcass traits were evaluated using meta-analysis. Meta-regression was used to investigate sources of heterogeneity. Ten studies (20 comparisons) were used in the meta-analysis on rumen measures. Lasalocid increased total VFA and ammonia concentrations by 6.46 and 1.44 m, respectively. Lasalocid increased propionate and decreased acetate and butyrate molar percentage (M%) by 4.62, 3.18, and 0.83%, respectively. Valerate M% and pH were not affected. Meta-regression found butyrate M% linearly increased with duration of lasalocid supplementation (DUR; = 0.017). When >200 mg/d was fed, propionate and valerate M% were higher and acetate M% was lower ( = 0.042, = 0.017, and = 0.005, respectively). Beef performance was assessed using 31 studies (67 comparisons). Lasalocid increased ADG by 40 g/d, improved feed-to-gain ratio (F:G) by 410 g/kg, and improved feed efficiency (FE; combined measure of G:F and the inverse of F:G). Lasalocid did not affect DMI, but heterogeneity in DMI was influenced by DUR ( = 0.004) and the linear effect of entry BW ( = 0.011). The combination of ≤100 vs. >100 d DUR and entry BW ≤275 vs. >275 kg showed that cattle ≤275 kg at entry fed lasalocid for >100 d had the lowest DMI. Heterogeneity of ADG was influenced by the linear effect of entry BW ( = 0.028) but not DUR. Combining entry BW ≤275 vs. >275 kg and DUR showed that cattle entering at >275 kg fed ≤100 d had the highest ADG. The FE ( = 0.025) and F:G ( = 0.015) linearly improved with dose, and entry BW >275 kg improved F:G ( = 0.038). Fourteen studies (25 comparisons) were used to assess carcass traits. Lasalocid increased HCW by 4.73 kg but not dressing percentage, mean fat cover, or marbling score. Heterogeneity of carcass traits was low and not affected by DUR or dose. Seven studies (11 comparisons) were used to assess dairy performance but the study power was relatively low and the evidence base is limited. Lasalocid decreased DMI in total mixed ration-fed cows by 0.89 kg/d but had no effect on milk yield, milk components, or component yields. Dose linearly decreased DMI ( = 0.049). The DUR did not affect heterogeneity of dairy measures. This work showed that lasalocid improved ADG, HCW, FE, and F:G for beef production. These findings may reflect improved energy efficiency from increased propionate M% and decreased acetate and butyrate M%. Large dairy studies are required for further evaluation of effects of lasalocid on dairy performance.

Modification of plant cell wall structure accompanied by enhancement of saccharification efficiency using a chemical, lasalocid sodium

The cell wall is one major determinant of plant cell morphology, and is an attractive bioresource. Here, we report a novel strategy to modify plant cell wall property by small molecules. Lasalocid sodium (LS) was isolated by chemical screening to identify molecules that affect the cell morphology of tobacco BY-2 cells. LS treatment led to an increase in cell wall thickness, whilst the quantity and sugar composition of the cell wall remained unchanged in BY-2 cells. The chemical also disordered the cellular arrangement of hypocotyls of Arabidopsis plants, resulting in a decrease in hypocotyl length. LS treatment enhanced enzymatic saccharification efficiency in both BY-2 cells and Arabidopsis plants. Microarray analysis on Arabidopsis showed that exposure to LS upregulated type III peroxidase genes, of which some are involved in lignin biogenesis, and jasmonic acid response genes, and phloroglucinol staining supported the activation of lignification by the LS treatment. As jasmonic acid-mediated lignification is a typical reaction to cell wall damage, it is possible that LS induces cell wall loosening, which can trigger cell wall damage response. Thus, LS is a unique chemical for modification of cell wall and morphology through changes in cell wall architecture.

Active transport of biogenic amines in chromaffin granule membrane vesicles

Chromaffin granule membrane vesicles accumulate large amounts of catecholamines against their concentration gradients. This process is ATP-dependent, reserpine, FCCP and nigericin sensitive. Carrier-mediated, reserpine-sensitive accumulation has also been demonstrated in the absence of ATP when a pH gradient (delta pH) is artificially generated across the membrane. Crude preparation of 5-hydroxytryptamine storage vesicles from rat brain or from pig platelets showed similar requirement of a transmembrane pH gradient for accumulation of the amine. The catecholamine transporter from chromaffin granules has been solubilized by the use of detergents in the presence of phospholipids. Removal of the detergent either by Sephadex filtration or by dialysis results in the formation of proteoliposomes which catalyze delta pH-dependent, reserpine-sensitive catecholamine accumulation. Under proper conditions, the solubilized H+-translocating ATPase has been incorporated into the same proteoliposomes with the catecholamine transporter, and ATP-dependent transport has been measured. The reconstituted protein shows specificity and affinity towards catecholamines similar to the native one.

Pediococcus acidilactici isolated from the rumen of lambs with rumen acidosis, 16S rRNA identification and sensibility to monensin and lasalocid

A lactic-acid producing bacterium was isolated from the rumen of lambs with rumen acidosis. The cells were gram-positive, nonmotile, nonsporing, catalase negative spherical, 1.5-2.0 μm in diameter, and occur in pairs and tetrads. Analysis of 16S ribosomal RNA indicated that the rumen bacterium was a strain of Pediococcus acidilactici with 99% of nucleotide homology. This bacterium was sensible to monensin and lasalocid at the unique dose tested of 300 ppm. The concentration of lactic acid and DM degradation decreased (P<0.05) when monensin or lasalocid were added to the culture media after 24, 48 and 72 h of incubation. In contrast, total VFA concentration and pH were higher (P<0.05) in the culture media added with the ionophores. Up to now S. bovis is considered the main ruminal bacterium related with rumen acidosis, but the importance of P. acidilactici should be also reconsidered in experimental studies focused on the control rumen acidosis.

Mucosal mast cell proteases are involved in colonic permeability alterations and subsequent bacterial translocation in endotoxemic rats

LPS-induced endotoxemia is associated with gut immune stimulation, mucosal inflammation, colonic paracellular permeability (CPP) alteration, and it promotes bacterial translocation (BT). Gut permeability increase linked to LPS promotes mucosal barrier dysfunction resulting to BT. However, the mechanisms involved in these alterations remain unknown. We aimed to evaluate the role of colonic mucosal mast cells and luminal serine protease activity (PA) in the alterations of CPP and BT induced by LPS. Rats receiving doxantrazole, a mast cell stabilizer, combined or not with LPS from Escherichia coli and CPP as well as BT were evaluated after each treatment. Mucosal mast cell activation was assessed by histological methods and by rat mast cell protease 2 level measurement in colonic content. Colonic luminal PA and mucosal inflammation (myeloperoxidase activity) were biochemically determined. In addition, the ability of luminal contents to act on CPP was evaluated in vitro in Ussing chambers. Peripheral administration of LPS promoted mast cell degranulation and increased CPP, BT, mucosal myeloperoxidase activity as well as rat mast cell protease 2 levels, and PA in colonic content. LPS-induced CPP increase and BT were prevented by doxantrazole. In vitro, exposure of the apical side of colonic tissues with supernatants from colonic contents of LPS-treated rats increased CPP. This effect was blocked by the serine protease inhibitor soybean trypsin inhibitor. Our data bring evidence of a key role of mucosal mast cells in LPS-induced increase of CPP and BT through the release of serine proteases into the colonic lumen.

Efficacy of ionophores in cattle diets for mitigation of enteric methane

Use of ionophores in cattle diets has been proposed as a strategy for mitigation of enteric CH4 emissions. Short- and long-term effects of feeding a single ionophore (monensin) or rotation of 2 ionophores (monensin and lasalocid) on enteric CH4 emissions were evaluated in 36 Angus yearling steers (328 +/- 24.9 kg of BW) over a 16-wk period. Steers were randomly assigned to 6 dietary treatments of 6 steers each. The 6 diets were low-concentrate without ionophore supplementation, low-concentrate with monensin supplementation, low-concentrate with a 2-wk rotation of monensin and lasalocid supplementation, high-concentrate without ionophore supplementation, high-concentrate with monensin supplementation, and high-concentrate with a 2-wk rotation of monensin and lasalocid supplementation. Daily enteric CH4 emissions, as measured using the SF(6) tracer gas technique, ranged from 54.7 to 369.3 L/steer daily. Supplementing ionophores decreased (P < 0.05) enteric CH4 emissions, expressed as liters per kilogram of DMI or percentage of GE intake, by 30% for the first 2 wk and by 27% for the first 4 wk, for cattle receiving the high-concentrate and low-concentrate diets, respectively. Cattle fed a rotation of ionophores did not (P > 0.05) exhibit a greater decrease and did not (P > 0.05) have a longer period of depressed enteric CH4 emissions compared with cattle receiving monensin only. Ionophore supplementation did not (P > 0.05) alter total ruminal fluid VFA concentration; however, the acetate:propionate ratio and ammonia-N concentration in ruminal fluid were decreased (P < 0.001) from the time that ionophores were introduced to the time they were removed from the diets. Both monensin and the rotation of monensin and lasalocid decreased (P < 0.001) total ciliate protozoal populations by 82.5% in the first 2 wk and by 76.8% in the first 4 wk during which they were supplemented in the high-concentrate and low-concentrate diets, respectively. Original ciliate protozoal populations were restored by the fourth and sixth week of supplementation when cattle were fed the high- or low-concentrate diets, respectively. No significant change was observed thereafter. These data suggest that the effects of ionophores on enteric CH(4) production are related to ciliate protozoal populations and that ciliate protozoal populations can adapt to the ionophores present in either low- or high-concentrate diets. Rotation of monensin and lasalocid did not (P > 0.05) prevent ciliate protozoal adaptation to ionophores.

Effects of Weaning and Ionophore Supplementation on Selected Blood Metabolites and Growth in Dairy Calves

Dairy calf weaning results in blood ketone concentrations in excess of mature rates of use and can result in excretion of ketones in urine representing a loss of energy. Lasalocid is frequently supplemented as an anticoccidial agent in calf starters; however, in mature ruminants it is known to alter molar ratios of ruminal volatile fatty acids (VFA). Effects of weaning transition and postweaning ionophore supplementation on body weight, dry matter (DM) intake, average daily gain (ADG), and blood concentrations of glucose, acetoacetate, beta-hydroxybutyrate (BHBA), lactate, pyruvate, nonesterified fatty acids (NEFA), VFA, insulin, and glucagon were examined using Jersey bull calves (n = 24) over 16 wk. Calves were blocked into groups of 2 according to birth date and weight and randomly assigned to receive either a commercial pelleted starter (control), or the same diet containing lasalocid (TRT; 83 mg/kg of DM). Calves were fed milk replacer from d 3 to 34 (d 3 to 20 = 454 g/d at 12% solids; d 21 to 34 = 568 g/d at 15% solids), from d 35 to 48 calves received both replacer (d 35 to 41 = 454 g/d; d 42 to 38 = 227 g/d) and free access to control or TRT starter, and from d 49 to 112 received ad libitum control or TRT. Body weight and jugular blood metabolite concentrations were measured and recorded weekly. Postweaning DM intake, average daily gain, and feed:gain did not differ between control and TRT calves. Glucose and NEFA concentrations did not differ between control and TRT, but declined with age. Insulin and glucagon concentrations did not differ between control and TRT, but glucagon concentrations increased with weaning. Total VFA significantly increased following introduction of solid feed at d 35 in both groups with an apparent 1-wk lag in TRT VFA increases compared with control. Jugular acetate and butyrate concentrations were greater in control calves than TRT calves during wk 7. Propionate concentrations did not differ between control and TRT at any time following weaning. Blood BHBA concentrations were greater in control than TRT during wk 8 and 9. Thus, consumption of starter supplemented with lasalocid delayed peak acetate and butyrate and lowered peak BHBA concentrations. However, supplementation at concentrations currently recommended for control of coccidiosis did not appear to be sufficient to enhance growth or efficiency during the wk 7 to 16 postweaning interval for this sample size.

Ionophore taste preferences of dairy heifers1

Two taste preference studies were conducted using six Holstein heifers in each experiment to determine preferences for no ionophore, lasalocid, or monensin in the diet. In Exp. 1, individually penned (approx. 5 mo old; 220 +/- 14 kg BW) heifers were fed a basal total mixed ration containing 46% corn silage, 46% grass haylage, and 8% soybean meal (DM basis). There were five treatments (mg/kg BW(-1)*d(-1)): 0 ionophore (control), 1 lasalocid (1L), 2 lasalocid (2L), 1 monensin (1M), or 2 monensin (2M). Ionophores were provided as part of the mineral mix that had been added to the control diet and through an ionophore-grain by-product mix to make the 2L and 2M treatments. All five diets were offered for 7 d, with the first 2 d for adaptation and the last 5 d for measurement of feed intake. The most preferred diet was then removed and the study continued with the four remaining diets. The most preferred diets were again eliminated sequentially, so that only two diets remained on d 13 and 14. Each feeding segment ranking of treatment preferences was determined based on the weight of feed refused at the end of each feeding segment. In Exp. 2, six 6-wk-old heifers (75 +/- 5 kg of BW) were individually fed either 0, 1L, or 1M in a study similar to Exp. 1, except that the most preferred diet was removed after 4 d, with the first day for adaptation and the last 3 d for measurement of feed intake. In Exp. 1, orthogonal contrasts indicated that heifers preferred the 1L and 2L diets over the 1M and 2M diets. Preferences between diet concentrations of ionophores (1 and 2 mg/kg of BW; Exp. 1) and the control and ionophore treatments did not differ, nor was there an interaction between ionophores and their concentration. Dairy heifers previously fed lasalocid prefer lasalocid over monensin when given a choice; however, heifers without previous exposure to an ionophore did not indicate a preference (Exp. 2).

Inhibition of Resistance Plasmid Transfer in Escherichia coli by Ionophores, Chlortetracycline, Bacitracin, and Ionophore/Antimicrobial Combinations

Medicinal feed additives bacitracin, chlortetracycline (CTC), laidlomycin, lasalocid, and salinomycin inhibited the transfer of multiresistance-conferring plasmid pBR325 (Tet(r) Amp(r) Cp(r), 6.0 kb) into selected gram-negative strains with the use of an in vitro model. High concentrations of ampicillin-sensitive competence-pretreated Escherichia coli HB 101 cells were exposed to 10% (v/v) of 1:10 dimethyl sulfoxide/agent : water containing test mixtures for 0.5 hr prior to plasmid addition and transforming conditions. Transformation was inhibited for all antimicrobials and showed a positive association wich higher concentration. Additional testing of ionophore compounds separately and in combination with bacitracin, chlortetracycline, lincomycin, roxarsone, tylosin, and virginiamycin at representative feed concentrations demonstrated 80.6% to >99.9% inhibition (P < 0.001) of resistance transfer. Bacitracin alone inhibited transformation within the range of 50-500 ppm. No increase in resistance transfer was observed when poultry-derived and reference gram-negative isolates having low or no transformation efficiency were additionally tested. The results suggest that these compounds, at relevant concentrations used in animal feed, may interfere with cell envelope-associated DNA uptake channels or other transformation competence mechanisms. Through these mechanisms, ionophores and cell membrane-interactive feed agents such as CTC and bacitracin may act to inhibit resistance transfer mechanisms within poultry and livestock.

Isolation and selection of ionophore-tolerant Eimeria precocious lines: E. tenella, E. maxima and E. acervulina

Eimeria parasites were isolated from Nanhai Guangdong province (southern China) and studied in chickens in wire cages to evaluate their drug resistance against commonly used ionophores: monensin (100 mg/kg of feed), lasolacid (90 mg/kg), salinomycin (60 mg/kg), maduramicin (5 mg/kg) and semduramicin (25 mg/kg). Chinese Yellow Broiler Chickens were infected with 40,000 crude sporulated Eimeria oocysts at 15 days of age and prophylactic medication commenced a day prior to infection. Drug resistance was assessed for each ionophore drug by calculating the anticoccidial index (ACI) and percentage optimum anticoccidial activity (POAA) based on relative weight gain, rate of oocyst production and lesion values. Results revealed that Nanhai Eimeria oocysts comprising of E. tenella, E. maxima and E. acervulina, were resistant to monensin, sensitive to both salinomycin and lasolacid and partially sensitive to maduramicin and semduramicin. By selection for early development of oocysts during passage through chickens, the prepatent time of E. tenella, E. maxima and E. acervulina were reduced by 49, 36 and 22 h, respectively. The precocious lines are less pathogenic than the parent strains from which they were selected and conferred a satisfactory protection for chickens against coccidiosis. These ionophore-tolerant precocious lines could have wider applications in the development of anticoccidial vaccines for sustainable control of coccidiosis.

An Alternative to Antibiotic-Based Drugs in Feed for Enhancing Performance of Broilers Grown on Eimeria Spp.-Infected Litter

Three trials were conducted to evaluate the effects of lasalocid, an anticoccidial feed additive (90.7 kg/ton); bacitracin, a growth-promoter (50 g/ton); and yeast culture residue (YCR) (1 kg/ton) on the performance of broiler chicks reared to 42 d of age on recycled litter. Recycled litter consisted of pine wood shavings containing droppings from chicks infected with 3 select strains of coccidia (Eimeria tenella, Eimeria maxima, and Eimeria acervulina). Response variables (BW, intestinal tract and litter coliform counts, cecal and liver relative weights, and litter moisture content) were recorded biweekly. Mean BW of chicks fed the diet supplemented with YCR was higher than that of the controls (P < 0.05) and comparable to that of the lasalocid-treated birds in all 3 trials. Mean BW of chicks in all treatment groups decreased uniformly as the litter aged and moisture content increased. The mean intestinal coliform population from YCR-treated chicks was lower (P < 0.05) than those of the control and lasalocid populations. The coliform count was consistently lower than that in chicks on a bacitracin-supplemented diet. Coliform counts from the control and lasalocid-treated birds did not differ. The litter coliform counts increased with increased use of the litter. Cecal and liver relative weights calculated from the chicks in trial 3 showed that only the liver was significantly affected by treatments. YCR appeared to be a viable alternative to bacitracin and lasalocid medication in enhancing growth of broiler chicks reared on recycled litter.

Effect of Lasalocid on Growth, Blood Gases, and Nutrient Utilization in Dairy Goats Fed a High Forage, Low Protein Diet

This study investigated the effect of lasalocid on weight gain, blood gases, nutrient digestibility, and nitrogen utilization in growing dairy goats. In a growth experiment, 24 crossbred dairy does were assigned to diets without or with lasalocid (approximately 30 mg per head per day) for 12 wk. Goats were group fed bermudagrass hay for free choice plus concentrate at a fixed level (approximately 0.264 kg DM per head per d). Goats grew faster when fed lasalocid than those fed the control diet. Jugular blood partial pressure of O2 was lower when goats were supplemented with lasalocid. In contrast, goats fed lasalocid tended to have a higher partial pressure of CO2 than control goats. Percent O2 saturation tended to increase, and concentrations of total CO2 tended to decrease in goats fed lasalocid. Serum glucose and urea N did not differ between treatments. In a metabolism experiment, 8 castrated male goats were fed hay and concentrate identical to those of the growth experiment to determine whole tract nutrient digestibility and N utilization. Lasalocid did not affect feed intake or nutrient digestion coefficients. Daily urinary N output was reduced by lasalocid supplementation. In spite of this, N retention was not significantly affected. With use of ionophore, the proportion of urinary N relative to digested N tended to decrease, and the retained N as a proportion of digested N tended to increase.

Effects of lasalocid on circulating concentrations of leptin and insulin-like growth factor-I and reproductive performance of postpartum Brahman cows

Objectives were to determine effects of lasalocid on reproductive performance and serum concentrations of leptin and IGF-I, and to correlate concentrations of leptin and IGF-I with reproductive performance of beef cows. Forty-one purebred, multiparous Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments by BW, BCS, and predicted calving date. Treatment began 21 d before expected calving. Cows were each fed 1.4 kg daily of an 11:1 corn:soybean meal supplement, with the L group receiving 200 mg of lasalocid/cow daily. Cows and calves were weighed, and cow BCS was assessed at calving and at 28-d intervals thereafter. Blood samples were collected weekly precalving, at parturition, and twice weekly thereafter. Sterile marker bulls were maintained with cows for estrous detection. Six days after estrus, ovaries were evaluated for corpus luteum formation, and blood samples from d 6, 7, and 8 after estrus were collected. Serum samples were assayed for progesterone (P4), IGF-I, and leptin concentration. Progesterone concentrations > 1 ng/mL were considered indicative of a functional corpus luteum. Treatment ended after completion of a normal estrous cycle, and cows removed from treatment were placed with a fertile bull equipped with a chinball marker. There were no treatment differences in calving date, calf sex, cow BW, BCS, calf BW, calf ADG, or in serum concentrations of P4, IGF-I, or leptin. Prepartum cow ADG was increased (P < 0.01) in L cows and tended (P < 0.011) to be increased from calving to d 56 after calving in L cows. Postpartum interval (PPI) was not affected by treatment; however, a greater percentage (P < 0.05) of L cows conceived by 90 d after calving (43% L vs. 15% C). First-service conception rate tended (P < 0.08) to be greater in L vs. C cows (68 vs. 40%), but pregnancy rate was not different (P < 0.12; 86% for L vs. 65% for C). There were no treatment differences (P > 0.18) for serum IGF-I concentrations. At calving, leptin was positively correlated with IGF-I (P < 0.04; r = 0.32), BCS (P < 0.06; r = 0.29), and cow BW (P < 0.02; r = 0.36), and was negatively correlated with PPI (P < 0.06; r = -0.29). These results provide evidence that feeding an ionophore before calving and during the postpartum period may increase the number of cows that rebreed to maintain a yearly calving interval. Cows with higher concentrations of leptin postpartum may exhibit shorter PPI.

Effect of dietary supplementation with oregano essential oil on performance of broilers after experimental infection with Eimeria tenella

A study was carried out to examine the effect of dietary supplementation of oregano essential oil on performance of broiler chickens experimentally infected with Eimeria tenella at 14 days of age. A total of 120 day-old Cobb-500 chicks separated into 4 equal groups with three replicates each, were used in this study. Two groups, one infected with 5 x 10(4) sporulated oocysts of E. tenella and the other not, were given a basal diet and served as controls. The other two groups also infected with E. tenella were administered diets supplemented with oregano essential oil at a level of 300 mg/kg, or with the anticoccidial lasalocid at 75 mg/kg. Following this infection, survival rate, bloody diarrhoea and oocysts excretion as well as lesion score were determined. Throughout the experimental period of 42 days, body weight gain and feed intake were recorded weekly, and feed conversion ratios were calculated. Two weeks after the infection with E. tenella supplementation with dietary oregano oil resulted in body weight gains and feed conversion ratios not differing from the non-infected group, but higher than those of the infected control group and lower than those of the lasalocid group. These parameters correspond with the extent of bloody diarrhoea, survival rate, lesion score and oocyst numbers and indicated that oregano essential oil exerted an anticoccidial effect against E. tenella, which was, however, lower than that exhibited by lasalocid.

Effects of the antibiotic ionophores monensin, lasalocid, laidlomycin propionate and bambermycin on Salmonella and E. coli O157:H7 in vitro

AIMS

To examine the effects of ionophores on Salmonella and Escherichia coli O157:H7 in pure and mixed ruminal fluid cultures.

METHODS AND RESULTS

Four Salmonella serotypes (Dublin, Derby, Typhimurium, and Enteriditis) and two strains of E. coli O157:H7 (ATCC 43895 and FDIU 6058) were cultured in the presence of varying concentrations of ionophores (monensin, lasalocid, laidlomycin propionate, and bambermycin) in pure and mixed ruminal fluid cultures. Bacterial growth rates in pure culture were not affected (P > 0.10) by ionophores at concentrations up to 10 times the approximate rumen ionophore concentration under normal feeding regimens. Likewise, ionophores had no effect (P > 0.10) on Salmonella or E. coli CFU plated from 24-h ruminal fluid incubations. Ionophore treatment decreased (P < 0.01) the acetate : propionate ratio in ruminal fluid cultures as expected.

CONCLUSIONS

Ionophores had no effect on the foodborne pathogens Salmonella and E. coli O157:H7 in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results suggest that ionophore feeding would have little or no effect on Salmonella or E. coli populations in the ruminant.

[Effects of veterinary drugs on beta-hexosaminidase release from rat basophilic leukemia cells (RBL-2H3)]

Little is known about the effects of residual veterinary drugs on the allergic reaction, except for the antigenicity of antibiotics and synthetic antimicrobials. Therefore, 59 kinds of veterinary drugs were investigated for their effects on the IgE receptor-mediated beta-hexosaminidase release from RBL-2H3 cells as an index of immediate allergic reaction. We found that the antibiotics chlorotetracycline, doxycycline, monensin, the synthetic antimicrobial pyrimethamine and the steroid hormone testosterone inhibited beta-hexosaminidase release. Most of the veterinary drugs showed no action, though the ionophores lasalocid, salinomycin and the steroid hormone hexestrol promoted beta-hexosaminidase release from injured cells. Based on the residual levels of these drugs and the frequencies of detection in actual food samples, it seems unlikely that these drugs have any immediate allergic effect in practice.

Interaction of fluoroquinolones and certain ionophores in broilers: effect on blood levels and hepatic cytochrome p450 monooxygenase activity

The concomitant administration to broilers of ionophore coccidiostats and certain chemotherapeutic agents may cause deleterious interactions, with toxicosis and death as possible sequelae. In this study, co-administration of the ionophore monensin was not shown to alter blood levels of enrofloxacin or norfloxacin. In addition, exposure to lasalocid was not shown to change blood levels of enrofloxacin. However, norfloxacin + lasalocid co-administration induced aminopyrine N-demethylase (AD) activity by day 5 after the last administration of norfloxacin, and induced a rise of norfloxacin levels in the blood. This rise of blood norfloxacin levels after co-administration of norfloxacin + lasalocid implies that lower levels of norfloxacin could be administered in birds also receiving lasalocid.

Secretion of the trefoil factor TFF3 from the isolated vascularly perfused rat colon

The trefoil factor TFF3 is a peptide predominantly produced by mucus-secreting cells in the small and large intestines. It has been implicated in intestinal protection and repair. The mechanisms that govern TFF3 secretion are poorly understood. The aim of this study was, therefore, to evaluate the influence of neurotransmitters, hormonal peptides and mediators of inflammation on the release of TFF3. For this purpose, an isolated vascularly perfused rat colon preparation was used. After a bolus administration of 1 ml isotonic saline into the lumen, TFF3 secretion was induced by a 30-min intra-arterial infusion of the compounds to be tested. TFF3 was evaluated in the luminal effluent using a newly developed radioimmunoassay. TFF3 was barely detected in crude luminal samples. In contrast, dithiothreitol (DTT) treatment of the effluent revealed TFF3 immunoreactivity, which amounted to about 0.3 pmol min(-1) cm(-1) in the basal state. Gel chromatography of DTT-treated luminal samples revealed a single peak that co-eluted with the monomeric form of TFF3. TFF3 was not detected in the portal effluent. Bethanechol (10(-6)-10(-4) M), vasoactive intestinal peptide (VIP, 10(-8)-10(-7) M) or bombesin (10(-8)-10(-7) M) induced a dose-dependent release of TFF3. In contrast, substance P evoked a modest release of TFF3, whereas calcitonin gene-related peptide (CGRP), somatostatin, neurotensin or peptide YY (PYY) did not modify TFF3 secretion. The degranulator compound bromolasalocid, 16,16-dimethyl PGE2 (dmPGE2) or interleukin-1-beta (IL-1-beta) also evoked a marked release of TFF3. In conclusion, TFF3 in the colonic effluent is present in a complex. This association presumably involves a disulfide bond. Additionally, the present results suggest a role for enteric nervous system and resident immune cells in mediation of colonic TFF3 secretion.

Nutritionally directed compensatory growth enhances heifer development and lactation potential

The objectives of this study were 1) to examine the interactive influence of a compensatory nutrition regimen and lasalocid supplementation on dairy heifer growth performance and 2) to document the extent to which compensatory growth sustains lactation potential over the first two lactation cycles. Twelve Holstein heifers, weighing an average of 160 kg (about 6 mo of age) were randomly assigned to treatments arranged in a 2 x 2 factorial design. Treatment variables were two dietary regimens (control and stair-step compensatory nutrition) and two levels of lasalocid (0 and 200 mg/d). The control heifers were fed a diet containing 12% crude protein (CP) and 2.35 Mcal of metabolizable energy (ME) per kilogram of dry matter. The stair-step compensatory nutrition heifers were subjected to a phased nutrition regimen and reared according to an alternating 3-2-4-3-4-2-mo schedule. The first stair-step (prepubertal phase) consisted of energy restriction [17% CP and 2.35 Mcal/kg of ME] for 3 mo followed by realimentation (12% CP and 3.05 Mcal/kg of ME) for 2 mo. The second step (puberty and breeding) consisted of energy restriction for 4 mo followed by realimentation for 3 mo. The third step (gestation period) was energy restriction for 4 mo concluding with realimentation for 2 mo. Dry matter intake of heifers during the restriction phase was limited to 70% of the control intake. Heifers were given ad libitum access to a high energy density diet during realimentation to allow compensatory development. Stair-step heifers supplemented with lasalocid had the highest efficiency of growth (body weight gain/dry matter intake), suggesting synergistic metabolism of lasalocid with compensatory growth action. Compensatory growth induced during the last trimester enhanced metabolic status by increasing circulating insulin and decreasing triglyceride levels. Heifers on the stair-step regimen had a significant increase in milk yield during the first (21%) and second (15%) lactation cycles. These results support our thesis that compensatory growth induced during an allometric growth phase improves mammary development and energy and protein metabolic status of dairy heifers.

Systemic lipopolysaccharide influences rectal sensitivity in rats: role of mast cells, cytokines, and vagus nerve

Intraperitoneal lipopolysaccharide (LPS) produces somatic hyperalgesia, releases interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha), and activates vagal afferents. The aim of this study was to evaluate the effect of peripheral LPS on rectal sensitivity and to specify the mechanisms involved. Abdominal muscle contractions were recorded in conscious rats equipped with intramuscular electrodes. Rectal distension (RD) was performed at various times after LPS or experimental treatments. In controls, RD significantly increased the number of abdominal contractions from a threshold volume of distension of 0.8 ml. At the lowest volume (0.4 ml), this number was increased after administration of LPS (3, 9, and 12 h later), recombinant human IL-1beta (from 3 to 9 h), recombinant bovine TNF-alpha (from 6 to 9 h), and BrX-537A (from 6 to 12 h), a mast cell degranulator. The effect of LPS was reduced by doxantrazole, Lys-D-Pro-Thr, and soluble recombinant TNF receptor. Vagotomy selectively amplified the response to LPS. We conclude that, in vivo, intraperitoneal LPS lowers visceral pain threshold (allodynia) through a mechanism involving mast cell degranulation and IL-1beta and TNF-alpha release and that the vagus nerve may exert a tonic protective role against LPS-induced rectal allodynia.

Anticryptosporidial activity of ranalexin, lasalocid and azithromycin alone and in combination in cell lines

The in vitro anticryptosporidial activities of ranalexin, lasalocid and azithromycin alone and in combination were investigated against four clinical isolates of Cryptosporidium parvum. Susceptibility was tested by inoculating the isolates on to cell monolayers and determining the parasite count after 48 h incubation at 37 degrees C. The culture medium was supplemented with Dulbecco's modified Eagle's medium containing serial dilutions of the above-mentioned compounds. Ranalexin showed moderate anticryptosporidial activity: at a concentration of 64 mg/L it reduced parasite counts by 33.8%. Azithromycin at a concentration of 8 mg/L gave inhibition comparable to that observed with the highest concentration of ranalexin. Lasalocid showed the highest activity, with a 70.3% reduction in parasite counts at 2 mg/L. The combination of ranalexin 64 mg/L and lasalocid 2 mg/L completely suppressed parasite growth without harming the monolayer.

Effects of lasalocid on performance of lactating dairy cows

Sixty lactating dairy cows (30 multiparous and 30 primiparous) were used in a completely randomized block design to determine the effect of lasalocid supplementation on dairy cow performance. Starting wk 2 prepartum and lasting through wk 17 of lactation, cows received one of three experimental diets. The experimental total mixed rations were control (CD), control + 10 mg/kg of lasalocid (CD + 10) and control + 20 mg/kg of lasalocid (CD + 20). The alfalfa-based control diet (40:60; forage:concentrate) was formulated to contain 18% crude protein, 35% nonstructural carbohydrates, 31% neutral detergent fiber, and 6.6% ether extract. Lasalocid supplementation linearly decreased dry matter intake (DMI) without affecting milk production or milk composition. Mean milk production and percentages of fat and protein were 30.0, 30.8, and 28.6; 3.56, 3.51, and 3.63; 3.06, 3.05, and 3.09; respectively for treatments CD, CD + 10, and CD + 20. Lasalocid supplementation decreased milk urea N (MUN) when compared to control cows, and increasing supplementation caused a significant linear decrease in MUN. For the primiparous cows, lasalocid supplementation decreased DMI and MUN while increasing body condition score and feed efficiency. Results from this study indicate that lactating dairy cows and, in particular, primiparous cows may benefit from lasalocid supplementation in terms of more efficient utilization of nutrients for milk production, reduced MUN levels, reduced body condition loss, and higher margin over feed cost.

Energy source and ionophore supplementation effects on lamb growth, carcass characteristics, visceral organ mass, diet digestibility, and nitrogen metabolism

In Exp. 1, 72 Targhee lambs (initial BW 22.1+/-.3 kg) were used to determine the effects of energy source (alfalfa pasture vs limit-fed, all-concentrate) and ionophore addition on performance, visceral organ mass, and carcass characteristics. There were no differences (P > . 10) in ADG or gain/ feed due to ionophore supplementation. Lambs that grazed alfalfa had greater (P < .05) liver, omasum, abomasum, small intestine, cecum, and large intestine weights than did lambs fed the concentrate diet. Lambs fed the concentrate diet had greater (P < .01) hot carcass weights, larger (P < .01) loin eye areas, and greater (P < .001) dressing percentages than lambs that grazed alfalfa. In Exp. 2, lambs offered the concentrate diet had greater (P < .001) DM and OM digestibilities than lambs offered alfalfa (89.5 and 91.1 vs 72.4 and 74.2%, respectively). Apparent and true N digestibilities were greater (P < .001) for the concentrate diet than for alfalfa (90.9 and 101.7 vs 77.7 and 91.9%, respectively). Likewise, grams of N retained per day were twice as great (P < .001) with the concentrate diet than with alfalfa (14.9 vs 6.0 g/ d). The greater visceral organ mass and resulting increases in energy and protein requirements in lambs that grazed alfalfa were probably responsible for the lesser hot carcass weight and dressing percentage compared with lambs fed 100% concentrate.

Effects of neurotransmitters, gut hormones, and inflammatory mediators on mucus discharge in rat colon

The effect of potential mediators of mucus secretion was investigated in the isolated vascularly perfused rat colon by using a sandwich enzyme-linked immunosorbent assay for rat colonic mucin and by histochemical analysis. Bethanechol (100-200 microM), bombesin (100 nM), and vasoactive intestinal peptide (VIP, 100 nM) provoked a dramatic mucin discharge (maximal response at 900, 900, and 600% of control loops, respectively). VIP-stimulated mucin secretion was abolished by tetrodotoxin, whereas atropine was without effect. In contrast, both tetrodotoxin and atropine significantly decreased mucin release induced by bombesin. Isoproterenol or calcitonin gene-related peptide was without effect. Serotonin (1-5 microM) and peptide YY (10 nM) evoked mucin discharge, whereas glucagon-like peptide-1 did not release mucin. Finally, bromolasalocid (20 microM), interleukin-1beta (0.25 nM), sodium nitroprusside (1 mM), and dimethyl-PGE2 (2.5 microM) induced mucus discharge. The results demonstrated a good correlation between the immunological method and histological analysis. In conclusion, these findings suggest a role for the enteric nervous system, the enteroendocrine cells, and resident immune cells in mediation of colonic mucus release.

Prolonged hormone secretion from neuroendocrine cells of Aplysia is independent of extracellular calcium

The role of Ca2+ from extracellular and intracellular sources in stimulating neurosecretion was investigated in four experiments using neuroendocrine bag cells of the marine mollusk Aplysia. (i) Bag cells were treated with either an extracellular calcium chelator (BAPTA) or Co(2+)-substitution within 30 s after onset of an electrical afterdischarge to prevent influx of Ca2+ from extracellular fluid. These treatments shortened the duration of the afterdischarge, but did not significantly affect the overall pattern or total amount of egg laying hormone (ELH) secretion, suggesting that extracellular Ca2+ is not required for maintenance of ELH release. (ii) Substitution of Ba2+ for Ca2+ has previously been shown to support bag cell afterdischarges that trigger transient elevations in intracellular Ca2+. We showed that this treatment also stimulates ELH secretion, suggesting that Ca2+ release from intracellular stores can stimulate ELH secretion. (iii) To raise intracellular Ca2+ levels in the absence of an afterdischarge, the calcium ionophore X537A was used to transport Ca2+ across plasma and organelle membranes. When this treatment was combined with extracellular calcium chelators so that the only source of Ca2+ was from intracellular compartments, ELH secretion was stimulated. Taken together, these findings are consistent with the hypothesis that release of Ca2+ from intracellular stores is sufficient to stimulate ELH secretion.

Eating barley too frequently or in excess decreases lambs' preference for barley but sodium bicarbonate and lasalocid attenuate the response

We conducted experiments to determine whether preference for barley was affected when lambs ate various amounts of barley and whether lambs ate more barley when it contained lasalocid and sodium bicarbonate (NaHCO3), both of which attenuate acidosis. In Exp. 1, lambs were assigned to two treatments (six lambs/treatment). For 2 d, lambs in two treatments were offered either 400 or 1,200 g of rolled barley from 0600 to 0700 as a preload meal. A preference ratio [PR = barley ingested/(total amount of alfalfa + barley ingested)] was calculated based on lambs' intake when offered a choice of 200 g each of rolled barley and alfalfa pellets hourly from 0700 to 1100. After the preload meal, lambs in Treatment 1 (400 g preload) showed equal preference for barley (.52) and alfalfa (.48) for 4 h on d 1 (P > .05); their preference for barley was less after the meal of barley on d 1 (.52) than on d 2 (.72), but their preference for barley declined between h 3 (.81) and 4 (.55) of d 2 (P = .11). Lambs in Treatment 2 (1,200 g preload) showed a low preference for barley on d 1 (.29) and 2 (.19) (P < .001). In Exp. 2, lambs were assigned to four treatments (six lambs/treatment): 1) rolled barley + NaHCO3 (2%) + lasalocid (33 ppm); 2) rolled barley + NaHCO3 (2%); 3) rolled barley + lasalocid (33 ppm); or 4) rolled barley. Intake of barley by lambs offered NaHCO3 + lasalocid (Treatment 1) was greater (P = .07) than that by lambs offered NaHCO3 (Treatment 2), whereas intake by lambs offered lasalocid (Treatment 3) was similar (P > .05) to that by controls. We conclude that eating barley too frequently or in excess caused a decrease in lambs' preference for barley and that NaHCO3 and lasalocid attenuated the aversion.

Observations on the mechanism of eggshell formation in the liver fluke, Fasciola hepatica

A mechanism for eggshell production in Schistosoma mansoni has been proposed (Wells & Cordingley, 1991), and suggests that the release of eggshell protein globules from the vitelline cells occurs under alkaline conditions within the ootype followed by their subsequent fusion to form the eggshell. Fusion and tanning of these components produces eggshell which autofluoresces. The present study was carried out to determine whether a similar process operates in Fasciola hepatica. A number of drug treatments were used to disrupt key steps in the maturation of vitelline cells. Treatment with the calcium ionophore lasalocid (1 x 10(-5) M) led to the premature release of eggshell globules from the vitelline cells but not their fusion. Incubation in monensin (1 x 10(-6)M), a sodium ionophore and ammonium chloride (NH4Cl) (5 x 10(-2) M), a weak base, resulted in the premature fusion of eggshell protein globules within the vitelline cells and premature tanning of the eggshell protein material. The copper-containing enzyme, phenol oxidase, is thought to be involved in the tanning process during the production of eggs. Diethyldithiocarbamate, (DDC, 1 x 10(-3) M) is a phenol oxidase inhibitor and treatment with this compound, in combination treatments with monensin and NH4Cl, prevented fusion of the vitelline cell globules and tanning of the shell protein material. The results of the study suggest that the mechanism for eggshell formation in F. hepatica is similar to that proposed for S. mansoni and may be common to other trematodes as well.

Mast cell degranulation induces delayed rectal allodynia in rats: role of histamine and 5-HT

Visceral hypersensitivity is a common feature of functional bowel disorders, where an increased number of mast cells have often been described. Thus, we investigated the effect of an experimental mast cell degranulation induced by BrX-537A on somatic (tail heating) and visceral (rectal distension) sensitivity in rats and the involvement of histamine and/or serotonin on this last response. After BrX-537A administration, the latency of tail withdrawal reflex was shortened within the 2- to 8-hr period. Moreover, BrX-537A reduced the distension volume threshold from 0.8 ml to 0.4 ml inducing allodynia, from 6 to 12 hr after its administration. This effect was suppressed by doxantrazole (mast cell stabilizing agent) and WAY 100635 (5-HT1A receptor antagonist), and reproduced by 5-HTP (5-HT precursor) and 8-OH-DPAT (5-HT1A receptor agonist). However, neither granisetron (5-HT3 receptor antagonist) nor H1, H2, or H3 histamine receptor antagonists modified the BrX-537A-induced allodynia. Consequently, mast cell degranulation initiates a delayed somatic and visceral allodynia, with the participation of serotonin, through 5-HT1A receptor activation, on the visceral response.

Inhibition of membrane lipid peroxidation by a radical scavenging mechanism: a novel function for hydroxyl-containing ionophores

In the present study we show that K+/H+ hydroxyl-containing ionophores lasalocid-A (LAS) and nigericin (NIG) in the nanomolar concentration range, inhibit Fe2+-citrate and 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP)-induced lipid peroxidation in intact rat liver mitochondria and in egg phosphatidylcholine (PC) liposomes containing negatively charged lipids--dicetyl phosphate (DCP) or cardiolipin (CL)--and KCl as the osmotic support. In addition, monensin (MON), a hydroxyl-containing ionophore with higher affinity for Na+ than for K+, promotes a similar effect when NaCl is the osmotic support. The protective effect of the ionophores is not observed when the osmolyte is sucrose. Lipid peroxidation was evidenced by mitochondrial swelling, antimycin A-insensitive O2 consumption, formation of thiobarbituric acid-reactive substances (TBARS), conjugated dienes, and electron paramagnetic resonance (EPR) spectra of an incorporated lipid spin probe. A time-dependent decay of spin label EPR signal is observed as a consequence of lipid peroxidation induced by both inductor systems in liposomes. Nitroxide destruction is inhibited by butylated hydroxytoluene, a known antioxidant, and by the hydroxyl-containing ionophores. In contrast, valinomycin (VAL), which does not possess alcoholic groups, does not display this protective effect. Effective order parameters (Seff), determined from the spectra of an incorporated spin label are larger in the presence of salt and display a small increase upon addition of the ionophores, as a result of the increase of counter ion concentration at the negatively charged bilayer surface. This condition leads to increased formation of the ion-ionophore complex, the membrane binding (uncharged) species. The membrane-incorporated complex is the active species in the lipid peroxidation inhibiting process. Studies in aqueous solution (in the absence of membranes) showed that NIG and LAS, but not VAL, decrease the Fe2+-citrate-induced production of radicals derived from piperazine-based buffers, demonstrating their property as radical scavengers. Both Fe2+-citrate and ABAP promote a much more pronounced decrease of LAS fluorescence in PC/CL liposomes than in dimyristoyl phosphatidylcholine (DMPC, saturated phospholipid)-DCP liposomes, indicating that the ionophore also scavenges lipid peroxyl radicals. A slow decrease of fluorescence is observed in the latter system, for all lipid compositions in sucrose medium, and in the absence of membranes, indicating that the primary radicals stemming from both inductors also attack the ionophore. Altogether, the data lead to the conclusion that the membrane-incorporated cation complexes of NIG, LAS and MON inhibit lipid peroxidation by blocking initiation and propagation reactions in the lipid phase via a free radical scavenging mechanism, very likely due to the presence of alcoholic hydroxyl groups in all three molecules and to the attack of the aromatic moiety of LAS.

In-vitro activities of paromomycin and lasalocid evaluated in combination against Cryptosporidium parvum

Using a chemiluminescence immunoassay, paromomycin and lasalocid were shown to inhibit Cryptosporidium parvum growth in Madin-Darby canine kidney cells in a concentration-dependent manner. The median effective concentrations (EC50s) for paromomycin and lasalocid were 1184 mg/L and 0.4 mg/L, respectively. Neither drug was cytotoxic to host cells at concentrations up to five times their EC50s. Drug combination studies were conducted and the resulting data were analysed by the median-effect principle and combination index method. Statistically significant synergy was observed when combinations of paromomycin and lasalocid were used at ratios of 5000:1 and 2500:1. A possible mechanism for synergy is discussed.

Residual activity of anticoccidial drugs in chickens after withdrawal of medicated feeds

Seven anticoccidial drugs commonly used in poultry (diclazuri), monensin, salinomycin, halofuginone, nicarbazin, robenidine, amprolium, and lasalocid) were tested for residual activity after withdrawal. In each test, the products were given at the recommended level to cages of 10 broiler chickens. Oral inoculation with coccidia was given after withdrawal of medication. Birds pretreated with 1 ppm of diclazuril and inoculated with Eimeria tenella after drug withdrawal had normal weight gain and very low lesion scores. Residual activity depleted gradually over several days, as shown by higher lesion scores when medication was withdrawn for up to 3 days before inoculation. Similar results were observed when young birds were inoculated with a mixture of E. tenella, E. maxima and E. acervulina, and also when birds were given diclazuril to market weight (6 weeks of age) and inoculated with a mixture of six species of Eiméria (The above species plus E. brunetti, E. mitis, and E. necatrix) after withdrawal of medication for 2 days. In contrast, there was no evidence of residual anticoccidial activity with nicarbazin, halofuginone, lasalocid, amprolium, salinomycin or monensin. Overall, the residual activity was unique to diclazuril.

Final-week performance of straight-run broilers as affected by early coccidiostat withdrawal followed by increased dietary salt

Three experiments were conducted to evaluate elevated dietary NaCl levels as a means of offsetting industry-observed reductions of growth, feed intake, and feed efficiency associated with early (35-d) coccidiostat withdrawal. In the first experiment, monensin (100 ppm) was withdrawn and dietary salt levels of 0.33, 0.48, 0.63, 0.78, or 0.93% provided from 35 to 42 d of age. Experiments 2 and 3 involved lasalocid (110 ppm) withdrawal and slat amounts of 0.33, 0.53, 0.73, or 0.93%. In all studies, a positive control of 0.33% salt and the coccidiostat was also given. Monensin withdrawal reduced body weight gain, which was not overcome by slat addition. Feed efficiency during the 1-wk period was improved to the level of the group receiving continued medication by salt amounts of 0.78% or above. In contrast to industry field observations, removal of lasalocid did not reduce body weight gain, feed intake, or water consumption, and elevation of salt levels resulted in no consistent improvements of weight gain, feed intake, or feed conversion. Water intake increased proportionally as salt concentration increased. Elevated salt levels do not appear to be a reliable means of offsetting reduced performance related to early coccidiostat withdrawal, nor were such performance problems demonstrable for lasalocid in these trials.

Use of potassium depletion to assess adaptation of ruminal bacteria to ionophores

When mixed ruminal bacteria from cattle fed timothy hay were suspended in a medium containing a low concentration of potassium, monensin and lasalocid catalyzed a rapid depletion of potassium from cells. The ionophore-mediated potassium depletion was concentration dependent, and it was possible to describe the relationship with saturation constants. Mixed ruminal bacteria never lost more than 50% of their potassium (Kmax = 46%), and the concentrations of monensin and lasalocid needed to cause half-maximal potassium depletion (Kd) were 178 and 141 nM, respectively. When cattle were fed 350 mg of monensin per day, the ratio of ruminal acetate to propionate decreased from 4.2 to 2.9, and the Kd of monensin was eightfold greater than the value for mixed ruminal bacteria from control animals. Monensin supplementation also caused a twofold increase in the Kd of lasalocid. Lasalocid supplementation (350 mg per day) had no effect on the ruminal acetate-to-propionate ratio, but it caused a twofold increase in the Kd values of monensin and lasalocid. Increases in Kd occurred almost immediately after ionophore was added to the ration, and the Kd values returned to their prefeeding values within 14 days of withdrawal. Ionophore supplementation had no effect on the Kmax values, and approximately 50% of the population was always highly ionophore resistant. Because the Kd values of even adapted ruminal bacteria were low (< 1.5 microM), it appears that a large proportion of the ruminal ionophore is bound nonselectively to feed particles or ionophore-resistant bacteria.

Lasalocid effects on ruminal degradation of protein and postruminal supply of amino acids in Holstein steers

Five ruminally and duodenally cannulated Holstein steers (305 kg) were used in a switchback experiment with three periods to evaluate two experimental treatments: a basal diet with or without 45 ppm of lasalocid. The basal diet contained approximately 43% rolled corn, 45% alfalfa hay, and 10% soybean meal (DM basis). Lasalocid did not affect feed intake or ruminal digestion of OM and NDF. Ruminal digestion of ADF tended to increase with supplemental lasalocid. Total tract digestion of OM, NDF, ADF, and N and intestinal flow of amino acids were not affected by lasalocid. Also, the ratio of microbial to nonmicrobial N fractions at the duodenum remained unchanged. Ruminal pH and concentrations of NH3, VFA, peptides, and amino acids were not affected by lasalocid. Ruminal protease activity decreased with supplemental lasalocid, but this decrease was not reflected in other variables, such as ruminal concentrations of peptides and amino acids. Ruminal deaminase activity remained unchanged. Thus, we concluded that dietary lasalocid did not alter ruminal protein degradation or postruminal flow of amino acids.

Influence of calcium concentration on the antimicrobial activity of lasalocid against Selenomonas ruminantium

The present study was designed to examine the interaction between the effects of lasalocid and Ca2+ on the growth and structure of Selenomonas ruminantium HD-4. Lasalocid, at a dose of 10 microM, inhibited cell growth almost completely after 12 hr incubation in the presence of relatively high extracellular concentrations of Ca2+ (from 5 to 50 mM), but only slightly reduced cell growth in the presence of 0.2 mM Ca2+. With Ca2+ alone, cell growth was also inhibited at 12 hr as a function of the concentration of Ca2+ over the range 5 to 50 mM. In cultures at mid-exponential phase, growth was markedly inhibited by the simultaneous addition of 10 microM lasalocid and 15 mM Ca2+, but only moderately inhibited by lasalocid in the absence of Ca2+. However, there was no significant effect on bacterial growth at the mid-exponential phase when Ca2+ alone was added to the incubation medium. In thin sections of cells treated with lasalocid in the presence of 15 mM Ca2+, abnormal cells were found with cytoplasmic voids and with an outer membrane detached from the inner membrane layer, this change in the outer membrane was also found in cells treated with lasalocid alone. There was no visible abnormality in the outer membrane in thin sections of Ca2(+)-treated cells, while most of these cells showed only a slight contraction of cytoplasmic material or a loss of cytoplasmic contents. These results indicate the presence of a synergistic effect between the actions of lasalocid and Ca2+ on cell growth, presumably due to induced cytoplasmic alterations.

Lasalocid and particle size of corn grain for dairy cows in early lactation. 2. Effect on ruminal measurements and feeding behavior

The effects particle size of corn grain and the ionophore lasalocid on ruminal fermentation and feeding behavior of early lactation cows were examined. Eight multiparous and 4 primiparous cows in early lactation were fed diets (44% forage) with cracked or ground dried shelled corn grain and with or without lasalocid (360 mg/d per cow). The experiment was a replicated (n = 3) 4 x 4 Latin square design with 21-d periods and a 2 x 2 factorial arrangement of treatments. Ground corn decreased ruminal turnover time of starch, did not affect ruminal lactate concentrations, increased propionate, decreased the ratio of acetate to propionate, and decreased branched-chain fatty acids. The range of ruminal pH within a day increased with ground corn, but mean pH was unaffected by treatment. Lasalocid increased lactate concentrations and did not affect the ratio of acetate to propionate. Lasalocid increased total time spent ruminating, and ground corn decreased ruminal contractions. Lasalocid tended to increase water intake, and ground corn increased water intake. Interactions of lasalocid and particle size of the corn grain were observed for ruminal turnover time of starch and NDF, and ruminal pool size of acetate and total VFA.

Lasalocid and particle size of corn grain for dairy cows in early lactation. 1. Effect on performance, serum metabolites, and nutrient digestibility

The effects were examined of corn grain particle size and the ionophore lasalocid on performance, blood parameters, and nutrient digestibility of early lactation cows. Smaller corn particle size was expected to result in faster rate of digestion and ruminal fermentation of starch. Eight multiparous and 4 primiparous cows in early lactation were fed diets (44% forage) with cracked or ground, dried shelled corn grain and with or without lasalocid (360.mg/d per cow). The experiment was a replicated (n = 3) 4 x 4 Latin square design with 21-d periods and a 2 x 2 factorial arrangement of treatments. Lasalocid tended to improve DMI. Lasalocid and ground corn decreased body condition loss and milk fat and increased milk protein. Ground corn tended to increase milk yield but had no effect on 4% FCM, lactose, and BW. For all cows, milk yield, 4% FCM, lactose, and BW were unaffected by lasalocid; however, subsequent analysis of individual squares revealed that milk yield of primiparous cows increased with lasalocid. Ground corn increased total tract starch digestibility and decreased NDF digestibility. Interactions between lasalocid and particle size of corn grain were observed only for change in serum insulin concentration before and after meals.

Flow cytometric analysis of the response of Eimeria tenella (Coccidia) sporozoites to coccidiocidal effects of ionophores

Fluorescein diacetate (FDA) and propidium iodide (PI) were used as indicators of membrane integrity after Eimeria tenella sporozoites were treated with polyether ionophores. Flow cytometry was used to quantitate the structural and functional effects based on red or green fluorescence and shape index of the sporozoites. Two field isolates (FS119 and FS139) were essentially resistant to polyether ionophores administered under practical conditions, whereas a laboratory strain was considered sensitive. The shape of sporozoites changed after treatment with ionophores, and this could be detected by flow cytometry. Green-fluorescing cells declined in number as the membranes were compromised by ionophore treatment. Red-fluorescing cells increased as the compromised membranes allowed entry of PI to bind with the nucleic acids. These effects were generally slower to develop in ionophore-tolerant field isolates compared with the sensitive laboratory strain. The effect of lasalocid on FDA and PI uptake, change in shape of the sporozoites, and lysis of sporozoites was more rapid than that of monensin or salinomycin. The 2 field isolates responded at different rates to salinomycin and monensin. Flow cytometry was a sensitive and accurate instrument for analysis of the effects of ionophores on sensitive and resistant lines of coccidia.

Potentiation of ionophorous anticoccidials with dihydroquinolines: compatibility of lasalocid and semduramicin with duokvin

Three battery tests were conducted to reveal whether or not there is an interaction between the new dihydroquinoline antioxidant, duokvin and lasalocid or the new anticoccidial, semduramicin, similar to that observed with some other ionophorous anticoccidials. In terms of body weight gain, no significant difference due to toxic interaction between duokvin and any dose of lasalocid or semduramicin was detected in chickens experimentally infected with oocysts of Eimeria tenella and E. mitis. Anticoccidial efficacy at reduced doses of both lasalocid and semduramicin in combination with duokvin showed numerical improvement; however, this again proved to be insignificant. The lack of incompatibility of this antioxidant with lasalocid or semduramicin allows their simultaneous administration on the one hand, but it fails to enable a substantial reduction of the chemoprophylactic concentration of anticoccidials in the broiler ration on the other.

Influence of lasalocid, cationomycin and feeding frequency on the postprandial kinetics of some plasma parameters in the rumen vein, portal vein and mesenteric artery of sheep

Two adult sheep, A and B, received successively during three experimental periods a forage-based pelleted feed, then the same diet supplemented with 33 mg/kg of lasalocid (L) or cationomycin (C). The feed was given in either eight (sheep A) or two (sheep B) daily meals. After four weeks of adaptation, 11 blood samples were taken through catheters in the rumen vein (RVA) and the mesenteric artery (MAA) in sheep A and in the rumen vein (RVB) and portal vein (PVB) in sheep B over a 5-hour period after the morning meal. Because of a blockage in the catheter it was not possible to measure the effect of C in MAA. Food intake had no immediate effect on the plasma levels measured: the distribution of eight daily meals stabilized plasma levels and made it easier to determine the effect of the ionophores. This effect varied according to the sampling site, the animal and the antibiotic, sometimes contradictorily. All the plasma parameters monitored in RVA were significantly modified by either one of the ionophores. A decrease in plasma albumin concentration (P < 0.05) was observed with L in MAA and with C in RVA and MAA. Aceto-acetate concentration decreased (P < 0.05) with L in MAA but increased with L and C in RVB. A decrease in glycaemia and uraemia (P < 0.05) was observed with L in MAA, RVA and RVB and with C in RVA. Total amino acid concentration decreased (P < 0.05) with C in RVA or increased (P < 0.05) with L in PVB and RVB. These variations in results may be due to different mechanisms of action of L and C on digestion, particularly in the rumen. While the changes undergone by the ketone bodies in the blood suggested a decrease in hepatic ketogenesis with L, there was no evidence that the ionophores had a direct postprandial effect.

Antimicrobial activity of lasalocid against Selenomonas ruminantium--effect of changes in pH induced by changing glucose concentration

A significant decrease in pH occurred in the culture medium when cells of Selenomonas ruminantium HD-4 were incubated in the presence of relatively high concentrations of glucose (0.4 and 1.0%). Forty microM lasalocid reduced cell growth to 35.5 and 35.7% of control growth, respectively, for 0.05 and 0.4% glucose, while growth was completely inhibited by 40 microM lasalocid in the presence of 1.0% glucose. In the presence of 80 microM lasalocid, cells were unable to grow within 24 hr at any glucose concentration. In the case of treatment with 10 microM lasalocid, growth was inhibited when pH decreased below 6.0 in the presence of 0.4 and 1.0% glucose. With 0.05% glucose, pH never reduced to below 6.4 within 24 hr and there was no significant effect of lasalocid on either growth or pH. When cultures were treated with 10 microM lasalocid at the mid-exponential phase, growth was moderately inhibited and abnormal cells which had outer membrane detached from the inner membrane layer resulting in cell lysis were found in thin sections. These results indicate that the presence of large amounts of glucose decreases pH in culture medium and that the decrease in pH to below about 6.0 causes the increased effect of lasalocid on the growth of S. ruminantium. These results suggest that the antimicrobial activity of lasalocid is potentiated by a decrease in extracellular pH.

The effect of salinomycin and lasalocid on laboratory cultures of Enterococcus faecium and Staphylococcus gallinarum strains

The growth of Enterococcus faecium strains CCM 4231 and EF 26, and Staphylococcus gallinarum SG 31 was inhibited by salinomycin and lasalocid at concentrations of 25 and 50 mg/L. Staphylococcus gallinarum was more sensitive to the additives used than were enterococci. Maximum inhibition (90%) was measured after the growth with the SG 31 strain in the presence of both ionophores. Growth of organisms was more inhibited by salinomycin at 25 mg/L (67.5%) than at 50 mg/L (63%). The inhibitory effect in enterococcal strains reached after the addition of salinomycin and lasalocid (on average) 63 and 58%, respectively. The CCM 4231 strain was more inhibited by salinomycin as well as by lasalocid than was the EF 26 strain.

The tryptophan fluorescence change upon conformational transition of the phosphoenzyme intermediate in sarcoplasmic reticulum Ca(2+)-ATPase is revealed in the absence of K+ and the presence of lasalocid

ATP-induced changes in the tryptophan fluorescence of the Ca(2+)-ATPase were determined with sarcoplasmic reticulum vesicles at pH 7.0 and 0 degrees C by steady-state measurements in the presence of Ca2+ and the absence of K+ with and without added lasalocid (a carboxylic ionophore, 50 microM), which was previously shown to cause a predominant accumulation of the ADP-insensitive form of the phosphoenzyme intermediate (EP) (Kawashima, T., Hara, H., and Kanazawa, T. (1990) J. Biol. Chem. 265, 10993-10999). When ATP was added in the absence of lasalocid, the fluorescence decreased by 1.7%. The addition of lasalocid quenched 71% of the fluorescence but did not reduce the ATP-induced fluorescence drop. The fluorescence drop and the EP formation were also determined in the presence of lasalocid by stopped-flow spectrometry and continuous-flow rapid quenching. The observed fluorescence drop was biphasic. The first phase coincided with the formation of EP, which was largely ADP-sensitive in this early stage of the reaction. The second phase was much slower than the first phase and coincided with the accumulation of ADP-insensitive EP. When the transition of EP from the ADP-sensitive form to the ADP-insensitive form was blocked by N-ethylmaleimide treatment, the second phase disappeared, and the fluorescence drop entirely coincided with the formation of ADP-sensitive EP. These findings demonstrate that the first phase of the fluorescence drop is attributed to the formation of ADP-sensitive EP, the second phase being attributed to the transition of EP from the ADP-sensitive form to the ADP-insensitive form. The present results reveal the conditions that definitely discriminate these two phases.

Augmentation and suppression of the excitatory and inhibitory neuromuscular transmission induced by the ionophores, X-537A and A23187, in the red muscle of carp, Cyprinus carpio

The effects of the ionophores, X-537A and A23187, on excitatory junction potentials (ejp), inhibitory junction potentials (ijp), diphasic junction potentials (diphasic jp) composed of ejp and ijp, and miniature excitatory junction potentials (mejp) were examined in the red muscles of carp, Cyprinus carpio. When 25 microM X-537A and 5 microM A23187 were applied, the amplitude of ejp and ijp increased transiently, then decreased gradually, and finally disappeared. The duration of ejp and ijp was little affected by the ionophores. The ionophores induced a transient increase in the frequency of mejp, which then decreased gradually after the maximum increase was attained, and finally fell below the control level. The ionophores had little effect on the resting membrane potential, membrane resistance of the muscle fiber, and amplitude of the compound action potential recorded from nerve bundles innervating this muscle. The ionophores caused ACh-evoked potentials to decrease gradually and finally disappear. These results suggest that the increase in the amplitude of ejp and ijp and in the frequency of mejp might be mainly due to the augmentation of ACh release from nerve terminals caused by an elevation of the intracellular Ca2+ concentration. On the other hand, the decrease and the abolition in the amplitude of ejp and ijp and in the frequency of mejp might be mainly due to the desensitization of the postsynaptic membrane.

Effects of lasalocid and cationomycin on the evolution of certain parameters in the blood plasma of sheep

Six adult sheep were fed at maintenance level, successively over three experimental periods, 1100 g of a roughage-rich diet without supplement or containing 33 mg kg-1 of lasalocid or cationomycin. The feed was administered in eight equal meals daily, every three hours. Blood samples were taken in each animal from the jugular vein at 10.00 hours, 16.00 and 22.00 hours, one hour after the animals were fed. The ionophores did not affect the plasma concentrations of glucose, free fatty acids, total amino acids, insulin, acetate, Ca or Mg. They decreased beta-hydroxy butyrate content (P < 0.05) and increased that of albumin (P < 0.05). Lasalocid alone significantly decreased uremia, but the significant threshold was only reached at 16.00 hours (P < 0.01). With this exception, the two ionophores had similar effects. Samples taken in peripheral blood appear to be too far from nutrient absorption sites to give a clear indication of the effects of these molecules on the products absorbed or metabolised in the digestive tract.