Lasalocid

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).

A method for the determination of lasalocid, an antibiotic and coccidiostat, in grease and fat is described. The manufacture of lasalocid produces a grease-like residue as a waste byproduct. Recently this byproduct has been shown to have been illegally introduced into the animal feed chain. Therefore, a quantitative and confirmatory procedure to analyse for lasalocid in this matrix is needed. A portion of grease/oil sample was extracted into hexane-washed acetonitrile, and a portion of the extract was then applied to a carboxylic acid solid-phase extraction (SPE) column for concentration and clean-up. The SPE column was washed with additional hexane-washed acetonitrile and ethyl acetate/methanol, after which lasalocid was eluted with 10% ammoniated methanol. The eluate was evaporated to dryness, redissolved in (1:1) acetonitrile-water and filtered through a PTFE syringe filter. Confirmation and quantitation of lasalocid in the final extract employed a triple quadrupole LC-MS/MS.

The molecular structure of 1:1 complex formed between the naturally occurring polyether ionophore, called lasalocid acid (LAS) and propargylamine (PROP) is studied by X-ray, FT-IR, (1)H NMR, (13)C NMR and ESI-MS methods. The complex formed between deprotonated LAS acid and protonated PROP molecule is stabilized by intra- and inter-molecular hydrogen bonds. The protons of the protonated amine group are hydrogen bonded to etheric and hydroxyl oxygen atoms of the LAS anion. The similarity of the FT-IR spectra of the LAS-PROP complex in solid state and in solution demonstrated that the molecular structures of the complex in both states are comparable. It is shown that LAS in solution can form concurrent complexes with metal cations (M=Li(+), Na(+), K(+)) and amine existing in equilibrium. Analysis of the structures of lasalocid complexes is important for a better understanding of the antibacterial and anticancer properties of lasalocid acid.

BACKGROUND: Mastitis is a major disease of dairy cattle. Given the recent emergence of methicillin-resistant Staphylococcus aureus as a cause of bovine mastitis, new intramammary (IMA) treatments are urgently required. Lasalocid, a member of the polyether ionophore class of antimicrobial agents, has not been previously administered to cows by the IMA route and has favorable characteristics for development as a mastitis treatment. This study aimed to develop an IMA drug delivery system (IMDS) of lasalocid for the treatment of bovine mastitis.