Microbiological method for assaying lincomycin in animal feed: collaborative study.

A microbiological assay for determining lincomycin in swine feed, supplement, and a vitamin-mineral premix was studied collaboratively in 16 laboratories. The design of the study involved a complete feed, feed supplement, and a vitamin-mineral premix covering a range of fortification from 20 to 80 g/ton and 80 to 2600 g/ton. Two methods of sample preparation were used depending on the concentration of lincomycin in the sample. Statistical evaluation of the results from the 2 methods indicated that 10 and 11 collaborators, respectively, had mean recoveries which were not significantly different from one another. Ten laboratories obtained a mean recovery of 112.2% (range 102.3--123.5%) for the lower level, and 11 laboratories obtained a mean recovery of 104.4% (range 100.0--107.7%) for the higher level. The method has been adopted as official first action.     

The response of cylindrocladium conidia to soil fungistasis

Direct observation of washed conidia of Cylindrocladium scoparium on non-sterile soils, air dried and rewetted immediately before deposition of conidia, indicated that peak germination (33–58%) occurred after 24 h incubation at 26°C. Peak germination on continually moist soils was lower (18–26%) than on rewetted soils. Lysis of germ tubes and germinating conidia on continually moist soils at 26°C was evident with 48 h. Conidia did not germinate on continually moist soils at 6°C and lysis did not become apparent until 168 h. Conidia germinated at a high level (93–99%) in axenic culture in the absence of exogenous C and N sources. The inhibition of conidial germination on soils may be attributed, in part, to the presence of soil volatiles. Germination of conidia placed on washed agar disks and exposed to volatiles from four soils ranged from 51 to 86% of the no-soil controls. Addition of carbon (13 ng C per conidium as glucose) and nitrogen (65 pg N ng^?1 C as NH₄C1) nullified the inhibitory effect of the soil volatiles. Germinability assayed on a selective medium at 26°C of conidia in artificially infested soils (approximately 10⁴ conidia g^?1 soil) decreased progressively during incubation at 26°C from 1 week to 4 months. No germinable conidia were recovered from artificially infested soils after 2 months incubation at 6°C. Conidia of C. floridanum and C. crotalariae responded similarly to C. scoparium in many assays.     

Microbial populations in pullman clay loam receiving large applications of cattle feedlot waste

One way to disperse waste from large commercial feedlots is to spread large amounts of the waste on limited areas nearby. The effects of this practice on the soil microbial populations was assessed. Feedlot waste (FLW) was applied for 5 yr at rates of 0, 22, 67, 134, and 269 t ha^?1 yr^?1. Additional treatments were 538 t ha^?1 yr^?1 for 1 and 3 years and applications of N and NPK fertilizer. Soil cores from plots were sampled for microbial analysis before, during, and after the fifth growing season. April, July. and December soil samples were analyzed to 180-, 20-, and 480-cm depths, respectively. The following utritional and physiological groups of microorganisms were counted: soil fungi on Rose Bengal agar; bacteria on a basal mineral salts medium, on nutrient agar (both aerobically and in BBL GasPak jars), and on EMB agar (Escherichia coli-type colonies and total counts); and nitrifying and denitrifying organisms. Little effect due to FLW application rates was found, and organisms producing coliform-type colonies on EMB agar did not persist in the soil. The results indicated that applying large amounts of feedlot waste will not deleteriously affect soil microorganisms.     

Morphology,composition and age of a buried paleosol,front range,Colorado, U.S.A.

A turf-banked lobe with a ground soil of post-Pinedale age overlies a buried paleosol which, although thin, appears to have been developed in situ. Organic matter from the Ab horizon of the paleosol yields a radiocarbon age of $\text{10,400 ± 400}\text{yrs}$ BP (Gak-3823) which corresponds with the waning stages of the Pinedale Glaciation in the Rocky Mountains. Abundant kaolinite and high amounts of silt and clay suggest that it may have developed over a long time interval.     

Fractionation of organo-mineral complexes by sedimentation and density techniques

Soil samples were fractionated by sedimentation in water and by flotation in heavy liquids to separate complexed and uncomplexed organic and inorganic components. Flocculation of clays in heavy organic liquids was delayed by addition of a surfactant. Heavy liquids and surfactants sorbed by soil components were removed by washing with acetone-water mixtures.In a sample of a red-brown earth, the organic carbon and nitrogen contents were highest in the finest separates. In samples of a ground-water rendzina and a chernozemic soil, the coarse clay and silt separates had the highest organic carbon and nitrogen contents. Organic matter was concentrated in low density fractions in all separates. Carbon/nitrogen ratios were lowest in the finer and heavier separates. Calcium, and to a lesser extent manganese, iron and phosphorus, were concentrated in low density fractions: thus these elements appear to be associated with organic matter and may be important in organo-mineral complex formation. Carbonates, titanium, iron, silicon and potassium were concentrated at the highest densities.Organic fractions < 2.06 g cm^?3 from sand size separates were insoluble in alkali and had wide carbon/nitrogen ratios characteristic of plant debris. The light fractions from fine silt and coarse clay separates were more soluble in alkali but showed high ratios of humic to fulvic materials and high absorption at 280 nm. Such materials were considered to be microbial cell debris and were associated with high contents of disordered aluminium and iron oxides and expanding lattice silicates in 1 to 5 μm aggregates.Heavier fractions, particularly of finer clay separates, contained more fulvic and humic materials of a more aliphatic nature than those in < 2.06 g cm^?3 fractions. It is suggested that physical sorption on clay surfaces may be more important in these fractions. Ellite and kaolinite were concentrated in medium density fractions, and contents of some iron oxides and titanium minerals were highest in fractions > 2.06 g cm^?3. Such minerals plus quartz and feldspars were associated with minor amounts of organic matter or possibly were not involved in organo-mineral associations.     

Extraction, cleanup, and quantitative determination of aflatoxins B1 ANd M1 in beef liver

A method for the determination of aflatoxin B1 in eggs was applicable for aflatoxin B1 in liver, but ineffective for aflatoxin M1 in liver because of poor recovery of added aflatoxin and interferences in thin layer chromatography. The method was modified by the addition of citric acid to the extracting solvent and ammonium sulfate to the extract solution for removing protein. The elution system for silica gel column cleanup was also changed by substituting methanol for acetone, and adding a step for confirmation of aflatoxin M1 identity. The method has been used successfully for survey and research on aflatoxin residues in animal tissues.