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PubMedDate not supplied

Development of an ELISA for lasalocid and depletion kinetics of lasalocid residues in poultry.

Polyclonal antibodies against the coccidiostat, lasalocid, were raised in sheep. The antisera were applied in an enzyme-linked immunosorbent assay (ELISA) for lasalocid, which was validated for chicken serum, liver and muscle. Bridge homology in the ELISA was overcome by absorbing unspecific antisera onto a conjugate between salinomycin and chicken serum albumin, which was immobilized onto Biosilon beads. The described assay is highly specific for lasalocid, and is capable of detecting lasalocid at concentrations of less than 0.15 ng/g, depending on the tissue. Residual concentrations of lasalocid in broilers fed medicated feed containing 90 mg/kg lasalocid were measured during a 7 day withdrawal period. The half-life of lasalocid was 11, 36 and 41 h in serum, liver and muscle, respectively. Lasalocid concentrations in liver were approximately 10 ng/g 7 days withdrawal of the medicated feed.

Animals↗
PubMed2001

Effects of dietary rice bran, lasalocid, and sex of calf on postpartum reproduction in Brahman cows.

To determine the effects of dietary lasalocid and increased dietary fat on reproduction, multiparous Brahman cows (n = 68), body condition score (BCS) of 6.2 +/- 0.7 and BW of 500.9 +/- 42.6 kg, were randomly assigned within sex of calf to receive one of four rations. All treatment groups grazed Coastal bermudagrass overseeded with rye-ryegrass and were given ad libitum access to hay and water. The control (n = 17) group received 4.17 kg x d(-1) x cow(-1) of 4:1 corn:soybean meal. The rice bran (n = 17) group received 4.35 kg x d(-1) x cow(-1) of 3:1:1 corn:soybean meal:rice bran (5.2% dietary fat). The lasalocid (n = 17) group received the Control diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). The rice bran-lasalocid (n = 17) group received the rice bran diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). Diets were fed once daily from d 1 after parturition through the detection of first estrus. Weight and BCS of cows and BW of calves were recorded at 14-d intervals from d 1 after parturition through detection of first estrus and at weaning. Cows were bled on d 1, 3, 5, 7, and 14 and at weekly intervals until estrus and on d 7 and d 10 after estrus. Ovarian follicular populations were monitored by transrectal ultrasonography weekly from d 14 after parturition through detection of first estrus. Plasma 13-14-dihydro-15-ketoprostaglandin-F2alpha (PGFM) and progesterone (P4) concentrations were quantified using RIA. Concentrations of PGFM from d 1 to 7 and P4 concentrations on d 7 and 10 after estrus were not influenced (P > 0.10) by diet or sex of calf. Changes in BW and BCS were not affected (P > 0.10) by diet. The number of medium-sized follicles tended to be greater (P < 0.06) in Controls than in cows on lasalocid or rice bran + lasalocid treatments on d 21. Cumulative return to estrus with a functional corpus luteum by d 60 postpartum was greater (P < 0.02) in the rice bran (70.6%) and lasalocid groups (76.5%) than in Controls (52.9%) or the group given rice bran + lasalocid (25.0%). Normal first estrous cycles were less likely (P < 0.07) to be exhibited in cows given rice bran + lasalocid than in other groups. Intervals from calving to corpus luteum formation, functional corpus luteum, and first P4 > or = 1 ng/mL were longer (P < 0.02) in cows given rice bran + lasalocid than in other cows. Combining increased dietary fat (5.2%) with lasalocid lengthened the time to reproductively important events.

Animal Feed↗
PubMed1981

Comparison of two forms and two levels of lasalocid with monensin on feedlot cattle performance.

One growth and two finishing trials were conducted with beef steers to compare lasalocid sodium and monensin sodium. Pure lasalocid, mycelia-cake lasalocid and monensin, each added individually to commercial protein supplement blocks at 880 mg/kg, depressed (P greater than .05) block intake so that approximately 100 mg of each additive were consumed daily by each animal. Daily gain, feed intake and feed efficiency for steers receiving blocks containing additives did not differ from the corresponding measures for steers receiving control blocks. No differences were observed in diet dry matter digestibility, as determined with acid-insoluble ash as an internal marker. Both forms of lasalocid and monensin reduced (P greater than .05) the incidence and concentration of coccidia oocysts. By day 40, only one steer on each of the additive treatments was shedding oocysts (4.2% of additive-supplemented animals), compared with 41.5% of the control steers. During trial 2, steers fed pure lasalocid gained faster and more efficiently (P greater than .05) than those fed the mycelia-cake lasalocid, monensin or control diets. The improvement in feed efficiency over the control value was 10.0, 3.4 and 4.0% with pure lasalocid, mycelia-cake lasalocid and monensin, respectively (P greater than .05). Steers fed mycelia-cake lasalocid had higher (P greater than .05) dressing percentages than those fed pure lasalocid or monensin. Dressing percentage was the only carcass measurement affected. In trial 3, lasalocid at 30 and 45 g/ton and monensin at 30 g/ton improved (P greater than .05) feed efficiency by 7.5, 11.0 and 8.2%, respectively. No significant differences in incidence or concentration of oocysts were observed between treatment groups in trial 3, probably because steers were in slatted floor pens.

Animal Feed↗
PubMed1987

Lasalocid and dietary sodium and potassium effects on mineral metabolism, ruminal volatile fatty acids and performance of finishing steers.

Thirty Angus steers averaging 357 kg were used to: 1) determine the effect of feeding lasalocid (33 mg/kg diet) on mineral metabolism and 2) determine the effects of varying dietary sodium (Na) and potassium (K) on finishing steers fed lasalocid. Treatments consisted of: 1) control (.25% Na, .5% K); 2) lasalocid (.05% Na, .5% K); 3) lasalocid (.25% Na, .5% K); 4) lasalocid (.05% Na, 1.4% K) and 5) lasalocid (.25% Na, 1.4% K). Ruminal fluid and blood samples were collected on d 28 and 90 of the 102-d study. Gain and feed conversion tended to be higher for steers fed lasalocid with the exception of the .05% Na, 1.4% K treatment. Control steers had lower (P less than .05) erythrocyte K concentrations, reduced (P less than .05) soluble concentrations of magnesium and copper in ruminal fluid and decreased plasma concentrations of zinc (P less than .05) and phosphorus (P less than .10) at 90 d compared with steers fed lasalocid and similar concentrations of Na (.25%) and K (.5%). Increasing dietary Na from .05 to .25% in the presence of lasalocid increased (P less than (P less than .05) molar proportion of ruminal acetate at 28 and 90 d reduced (P less than .05) propionate at 90 d. Increasing K from .5 to 1.4% decreased (P less than .01) soluble Na and increased (P less than .01) soluble K concentrations in ruminal fluid. Steers fed lasalocid (.25% Na, .5% K) had lower concentrations of K (P less than .10) and zinc (P less than .10) in liver than control steers. Sodium and K level also affected tissue concentrations of certain minerals. Results suggest that dietary Na and K influence mineral metabolism and that dietary Na affects ruminal molar proportion of acetate in cattle fed lasalocid.

Animals↗
PubMed1988

Effect of lasalocid on feedlot performance and energy partitioning in cattle.

Two experiments were conducted to quantify the effects of lasalocid on the performance and energy partitioning of cattle fed a 90% concentrate, barley-based diet. Experiment 1 utilized 100 Hereford heifers (initial weight 308 kg) fed diets containing no added ionophore, lasalocid added at 24, 36 or 54 mg/kg dry matter (DM), or monensin added at 33 mg/kg DM. In the 98-d trial, lasalocid-fed heifers gained an average of 1.35 kg daily, whereas control heifers gained 1.24 kg (P = .12). Heifers fed lasalocid (36 or 54 mg/kg DM), monensin, and the control diet required 6.2, 6.5 and 6.9 kg DM/kg gain, respectively (P greater than .1). Ionophores had no influence on carcass quality. In Exp. 2, four steers (616 kg) were fed the control or lasalocid diet (36 mg/kg DM) at daily feeding levels of 21, 44, 67 and 89 g DM/kg body weight.75; fecal, urinary, methane and heat losses were measured by total collection and indirect calorimetry methods. The proportion of digestible energy lost as methane averaged 7.5% for steers fed the control diet and 7.1% for the steers fed lasalocid (P less than .1). Lasalocid improved (P less than .05) the metabolizable energy (ME) density of the diet by 8, 8 and 5% at the 21, 44 and 67 g DM feeding levels. There was no difference (P greater than .1) between diets in ME density at the 89 g DM feeding level. The net energy for maintenance (NEm) value of the diet was increased (P less than .05) by 10 to 21% with lasalocid, whereas the net energy for gain (NEg) value was not affected. Average heat productions of the steers were increased (P less than .05) by 7% with lasalocid. The ME requirement for maintenance was estimated at 84 and 81 kcal/kg body weight.75 from linear regressions of energy retention and ME intake above maintenance for the control and lasalocid diets, respectively. Corresponding estimates using a semilog-linear method were 90 and 92. No differences (P greater than .1) in blood concentrations of insulin, glucagon or growth hormone were observed with the ionophore treatment. It was concluded that the main method by which lasalocid improved feed conversion was by increasing the ME density of the diet.

Animals↗
PubMed1996

The incidence and cause of lasalocid residues in eggs in Northern Ireland.

Lasalocid is a coccidiostat licensed for use in poultry, but not for use in egg-laying birds. Lasalocid residues were determined in an egg sample from each of 161 egg producers in Northern Ireland using liquid chromatography-electrospray ionization mass spectrometry, following reports from the Veterinary Medicines Directorate concerning the incidence of lasalocid residues in the United Kingdom. Approximately 66% of the eggs contained lasalocid residues at concentrations in excess of 0.3 ng/g. There was no apparent difference in the incidence of lasalocid residues between free range and battery eggs. Carry-over of lasalocid from medicated to unmedicated batches of both premix and feed, during milling processes, was identified as a possible cause of contamination. Subsequently, egg-laying birds were fed meal containing a range of lasalocid concentrations, similar to those found as a result of unintentional contamination at a feed mill (0.1-5.0 mg/kg). The concentrations of lasalocid, measured in their eggs, were similar to that found in the survey. Lasalocid persisted in eggs for 10 days after withdrawal of medicated feed and replacement with lasalocid-free feed.

Animal Feed↗
PubMed1990

[The effect of lasalocid on apparent digestibility, characteristics of rumen fermentation and fattening and slaughter output of bulls].

Four digestion experiments with 5 wethers each (Feeding: artificially dried grass; 0, 15, 30 or 60 mg lasalocid per animal and day), two short time experiments (Exp. 1: 3 rumen fistulated sheep; feeding; artificially dried grass; 0, 15, 30 or 60 mg lasalocid per animal and day; exp. 2: 20 bulls; feeding; 2 kg concentrates per animal and day; wheat straw ad libitum; 0, 150 or 300 mg lasalocid per animal and day) and one individual feeding experiment (24 bulls per group; duration: 279 days, feeding: 2 kg concentrates per animal and day, corn silage and whole barley-grass silage ad libitum; 0 or 100/200 mg lasalocid per animal and day) were carried out in order to investigate the influence of the ionophore lasalocid on digestibility, figures of rumen fermentation as well as fattening and slaughtering results of bulls. Higher doses of lasalocid (30 and 60 mg per animal and day) decreased significantly digestibility of organic matter (1.8 and 2.8 units) and crude fibre (5.8 and 7.2 units). Relative acetate (22 to 120 mmoles per mol) and butyrate concentration (23 to 58 mmoles per mol) were decreased and molar propionate concentration of rumen liquid (25 to 154 mmoles per mol) was increased depending on level of lasalocid supplementation. Lasalocid did not significantly influence the dry matter intake; daily weight gain and slaughtering results were increased (4.4 and 6.1%), energy efficiency was improved (3.8%). Effects of lasalocid are similar to that of monensin. A dose of 20 to 30 mg lasalocid per kg dry matter is recommended.

Animals↗
PubMed1988

Performance and ruminal changes of early-weaned calves fed lasalocid.

Twenty-two neonatal calves were assigned to a control or lasalocid-fed group and weaned at 3 wk of age. They were fed a prestarter diet from 3 d of age until they consumed 227 g/d and then a mixture of 227 g prestarter daily and starter diet in ad libitum amounts. The lasalocid-fed group received lasalocid in milk at 1 mg/kg body weight daily from 4 to 7 d and at .5 mg/kg body weight daily in milk and medicated prestarter diet (88 mg lasalocid/kg) during the 2nd wk. After 2 wk, lasalocid-fed calves were given medicated prestarter and starter (44 mg lasalocid/kg) diets. Four calves in each group were ruminally cannulated at 3 to 5 d of age, and ruminal contents were obtained at weekly intervals to monitor microbial activity. Rectal fecal samples were collected from all calves and examined for coccidial oocysts. Lasalocid-fed calves had a greater weekly feed intake and weight gain than control calves after 6 wk of age. Total ruminal volatile fatty acid concentrations were higher, but the acetate:propionate ratio was lower in lasalocid-fed calves than in control calves. Total viable anaerobic and amylolytic bacterial counts were higher in lasalocid-fed calves than in control calves. No significant treatment effect was found for ruminal NH3-N concentration or ruminal lasalocid-resistant, lactobacilli, lactate-utilizing, cellulolytic or methanogenic bacterial numbers. No evidence of coccidiosis was detected in either group. In general, lasalocid-fed calves had greater feed intake, weight gain and ruminal microbial activity than the calves fed no lasalocid in the diet.

Animals↗
PubMedDate not supplied

Selective neurotoxicity induced by the ionophore lasalocid in rat dissociated cerebral cultures, involvement of the NMDA receptor/channel.

An in vitro model of dissociated cerebral cultures, prepared from prenatal 15-16-days rat fetuses, was used to further characterize the neurotoxic effects caused by the antibiotic ionophore lasalocid-X-537A. The damage caused by lasalocid (1-2 microM, 2-4 hr) included swelling of perikarya, followed by cytolysis of most neurons present in the cultures. The neuronal damage was dose-dependent, noticeable at concentrations above 0.5 microM, and was more pronounced in established cultures (14 days in vitro-DIV) than in younger ones (7 DIV). Unlike neurons, no damage was observed in glia and other non-neuronal cells present in the cultures by exposure to 2 microM lasalocid. Moreover, the drug was not toxic for cultures of rat astrocytes and C6 glioma cells. Another calcium ionophore A-23187 (calcimycin, 1 microM), destroyed both neuronal and non-neuronal cells within 1 hr. Ca2+ influx was increased by 140% in cultures exposed to lasalocid (1.5 microM). The lasalocid neurotoxic effects were neither inhibited by 10 microM nimodipine (a calcium channel antagonist) nor by 10 microM 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX)(a non-N-methyl-D-aspartic acid (NMDA) receptor antagonist), but were exclusively blocked by 10 microM MK-801 (a non-competitive NMDA receptor/channel antagonist). The neurotoxicity induced by lasalocid was further confirmed by measurements of lactate dehydrogenase (LDH) released into the media. Lasalocid (1.5 microM) induced the release of both LDH and arachidonic acid (AA) (by 8 and 4 fold of control values, respectively), and this was blocked by MK-801 but not by CNQX. These results are in according with the observations that activation of calcium influx through the NMDA receptor leads to activation of phospholipase A2 (PLA2) and release of AA. In contrast, MK-801 did not block the release of either LDH or AA mediated by the calcium ionophore A-23187 (1 microM) in these cultures. [3H]-MK-801 binding to washed rat cortical membranes, a measure of direct interaction with the NMDA receptor/channel complex, was not affected by lasalocid either alone or in the presence of glutamate and glycine. [3H]-D-aspartate release, a measure of excitatory amino acid (EAA) secretion mediated by NMDA receptor activation, was increased by lasalocid and could be blocked by MK-801. These observations suggest that lasalocid induces selective neurotoxicity, which involves the NMDA receptor/channel complex, possibly indirectly, resulted in elevated intracellular Ca2+ levels and the subsequent glutamate or aspartate release.

Animals↗
PubMed1991

Alterations in mitochondrial Ca2+ flux by the antibiotic X-537A (lasalocid-A).

A previous communication (Pereira da Silva, L., Bernardes, C.F. and Vercesi, A.E. (1984) Biochem. Biophys. Res. Commun. 124, 80-86) presented evidence that lasalocid-A, at concentrations far below those required to act as a Ca2+ ionophore, significantly inhibits Ca2+ efflux from liver mitochondria. In the present work we have studied the mechanism of this inhibition in liver and heart mitochondria. It was observed that lasalocid-A (25-250 nM), like nigericin, promotes the electroneutral exchange of K+ for H+ across the inner mitochondrial membrane and as a consequence can cause significant alterations in delta pH and delta psi. An indirect effect of these changes that might lead to inhibition of mitochondrial Ca2+ release was ruled out by experiments showing that the three observed patterns of lasalocid-A effect depend on the size of the mitochondrial Ca2+ load. At low Ca2+ loads (5-70 nmol Ca2+/mg protein), under experimental conditions in which Ca2+ release is supposed to be mediated by a Ca2+/2H+ antiporter, the kinetic data indicate that lasalocid-A inhibits the efflux of the cation by a competitive mechanism. The Ca2+/2Na+ antiporter, the dominant pathway for Ca2+ efflux from heart mitochondria, is not affected by lasalocid-A. At intermediate Ca2+ loads (70-110 nmol Ca2+/mg protein), lasalocid-A slightly stimulates Ca2+ release. This effect appears to be due to an increase in membrane permeability caused by the displacement of a pool of membrane bound Mg2+ possibly involved in the maintenance of membrane structure. Finally, at high Ca2+ loads (110-140 nmol Ca2+/mg protein) lasalocid-A enhances Ca2+ retention by liver mitochondria even in the presence of Ca2(+)-releasing agents such as phosphate and oxidants of the mitochondrial pyridine nucleotides. The maintenance of a high membrane potential under these conditions may indicate that lasalocid-A is a potent inhibitor of the Ca2(+)-induced membrane permeabilization. Nigericin, whose chemical structure resembles that of lasalocid-A, caused similar results.

Acetates↗
PubMed1994

Binding of radiolabeled monensin and lasalocid to ruminal microorganisms and feed.

Gram-negative, ionophore-resistant ruminal bacteria and Gram-positive, ionophore-sensitive species bound similar amounts of [14C]lasalocid, but neither group bound large amounts of [14C]monensin. Membrane vesicles also bound more lasalocid than monensin (P < .05). The binding was first-order at low cell or vesicle concentrations and saturable at high cell or vesicle densities. Streptococcus bovis was inhibited by both monensin and lasalocid (5 microM), but cells that were re-incubated in medium lacking ionophore grew rapidly. Lasalocid-treated cells grew very slowly when they were resuspended in fresh medium. Based on these results, it seemed that lasalocid had a higher affinity for bacterial membranes than monensin. Mixed bacteria, however, bound nearly equal amounts of [14C]monensin and [14C]lasalocid (P > .05). Monensin binding was greatly reduced when the mixed ruminal bacteria were pretreated with Tris+EDTA (P < .05), but Tris+EDTA did not affect the binding of lasalocid. Mixed ruminal protozoa always took up more lasalocid than monensin (P < .05), but feed particles bound equal amounts of [14C]lasalocid and [14C]monensin (P > .05). Based on the binding capacity of mixed ruminal bacteria, ruminal protozoa, and feed particles, there would be little free ionophore in ruminal fluid.

Animal Feed↗
PubMed1985

Reduction of 3-methylindole production and prevention of acute bovine pulmonary edema and emphysema with lasalocid.

A study was conducted to determine the dose of lasalocid that would effectively reduce ruminal conversion of tryptophan (TRP) to 3-methylindole (3MI) and prevent the development of acute bovine pulmonary edema and emphysema (ABPE). After adaptation to a maintenance diet for 3 wk, 20 mature beef cows were randomly divided into four groups of five cows each and fed 0, 200, 400 or 600 mg lasalocid X head-1 X d-1 in .5 kg ground barley for the 12-d experimental period. In vitro conversion of TRP to 3MI and indole by ruminal fluid and volatile fatty acid (VFA) concentrations were determined on d 0, 2, 4, 6 and 12. On d 6, an oral dose of .35 g TRP/kg body weight was given to induce ABPE, and ruminal production of 3MI and indole was determined at intervals thereafter. Formation of 3MI was sharply reduced (P less than .01) both in vitro and in vivo by lasalocid treatment at 200 mg X head-1 X d-1. Further suppression of 3MI production occurred as the lasalocid dose was increased (P less than .05). Linear (P less than .0001) and quadratic (P less than .002) components were determined for the relationship between lasalocid dose and 3MI production. Indole formation was variable, but tended to increase (P less than .05) with increasing lasalocid dose. Cows that received no lasalocid developed moderate to severe clinical signs of ABPE and three cows died of acute lung disease. Lasalocid treatment at all levels prevented ABPE. Lasalocid decreased ruminal acetate and butyrate, and increased propionate concentration (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Structural and kinetic studies of lasalocid A (X537A) and its silver, sodium, and barium salts in nonpolar solvents.

The ionophore lasalocid A (X537A) and its metal salts have been investigated by high resolution (270 MHz and 360 MHz) proton nuclear magnetic resonance spectroscopy to obtain structural and kinetic information in nonpolar solution. The proton resonances were assigned from double resonance studies on lasalocid A and on its salts, homologs, isomers, and chemically modified derivatives. Studies of proton and carbon longitudinal relaxation time suggest that lasalocid A exists as a monomer, whereas the sodium and barium salts exist as dimers in nonpolar solvents. A study of the magnitude of the vicinal proton coupling constants and the chemical shifts and linewidths of the hydroxyl resonances suggest that the backbone conformation and intramolecular hydrogen bonds are similar for lasalocid A and its sodium and barium salts in nonpolar solvents. Nuclear magnetic resonance studies on the role of bound solvent molecules suggest a tightly bound water molecule in the barium complex dimer (crystallized from water-ethanol) and a weakly bound ethanol molecule in the lasalocid A monomer (crystallized from ethanol) in cyclohexane. The selective changes in proton chemical shift on complexation [where the polar faces of two lasalocid anions coordinate the metal cation(s) in nonpolar solvents have been analyzed in terms of the proximity of the resonances to the cation, their linkage to the coordinating oxygen atoms, and the magnetic anisotropy effects of the polar groups of one ligand on the resonances of its partner in the dimer. The nuclear magnetic resonance studies in solution are compared with earlier observations on lasalocid A and its salts in the crystalline state. Thus, the short Ag-C5 distance in the crystal structure of silver complex dimer is also observed in the solution structure. The kinetic parameters associated with the exchange between lasalocid A and its barium complex in chloroform have been measured from an analysis of the resonance line shapes as a function of temperature.

Anti-Bacterial Agents↗
PubMed1988

Long-term supplementation of lasalocid-sodium for beef bulls during grazing and subsequent finishing period.

117 white-red beef bulls were involved to investigate the effect of lasalocid-sodium when fed either during the grazing period, or the finishing period, or during both subsequent periods. The ionophore was fed at 250 mg daily per head incorporated in 1 kg dry sugar beet pulp on pasture and at 65 mg per kg concentrate afterwards (corresponding with 27 ppm in the ration DM). The finishing diet consisted of maize silage ad libitum and 0.75 kg concentrate per 100 kg liveweight per day. On pasture lasalocid significantly increased daily gain form 0.6 to more than 0.7 kg, without affecting the grazed area per animal. During the finishing period growth rate was only slightly affected by lasalocid, but feed intake was reduced (P less than 0.05) and feed conversion improved (P less than 0.05). Feeding lasalocid permanently for more than 400 days did not reduce these positive effects. Cumulative daily gain, total feed intake per head and feed conversion were 1.12 kg, 2176 kg dry matter (DM) and 4.70 kg DM. These figures amounted to 1.05 kg, 2283 kg DM and 5.16 kg DM when no lasalocid was fed; 1.06 kg, 2141 kg DM and 4.87 kg DM when lasalocid was only fed during the finishing period and 1.09 kg, 2246 DM and 4.99 kg DM when lasalocid was only fed during the grazing period. Daily gains of 1.05 and 1.06 kg were significantly lower (P less than 0.05) than 1.12 kg. Most carcass data were unaffected, except fatness. The permanent feeding of lasalocid increased carcass fatness, mainly as the result of a higher final weight.

Animal Feed↗
PubMed1989

Effect of lasalocid sodium and molasses on performance of fattening lambs and on rumen liquor and blood parameters.

Two experiments were conducted to evaluate the effects of sugar beet molasses (0, 8 and 16%) with or without lasalocid sodium (33 ppm) on rumen liquor and blood parameters of sheep, and on fattening reared Karagouniko breed lambs. In Expt. 1 six adult Karagouniko fistulated wethers were fed six different pelleted diets. The results showed that lasalocid decreased (P less than 0.01) total VFAs concentration in the rumen (7.1%) by reducing (P less than 0.001) acetic, n-butyric and iso-valeric acids while increased (P less than 0.001) propionic acid concentrations. The same trends were observed in molar proportions of the individual VFAs. The total VFAs production was also depressed by 13.75% when molasses were used at the level of 16%. No interaction among the main treatments was observed with the exception of L X M with 16% molasses where the propionic acid concentration decreased, and those of butyric and iso-valeric acids increased. Lasalocid did not alter the mean values of rumen liquor pH and ammonia nitrogen concentration while molasses increased the later parameter. No significant differences on dietary protein degradability were observed among treatments. Lasalocid reduced the beta-HBA concentration by 13% in the blood while molasses increased it (P less than 0.001). Free fatty acids' concentration was decreased by the molasses inclusion to the diets, while lasalocid didn't alter blood glucose concentration. Finally, the number of protozoa in the rumen liquor was reduced by 49 and 70% at 0 and 5 hours post feeding respectively with the addition of lasalocid to the diets, regardless of the use of molasses. In Expt. 2 utilized 86 weaned male Karagouniko fattening lambs, with initial mean LW 13 kg, for 60 days. They were assigned to six groups and fed ad libitum with diets of the same composition as in Exp 1. Lasalocid increased the growth rate by 8.6%, reduced feed consumption by 4.8% (P less than 0.005) and improved feed conversion by 11.8%. Molasses also improved growth rate by 16-34% and increased feed consumption by 15-22%. The interaction of L X M to feed consumption was significant (P less than 0.001). None of the treatments had an effect on carcass characteristics. Finally lasalocid showed its positive action when it was used in combination with molasses in ruminants' diets.

3-Hydroxybutyric Acid↗