Monensin 3 , a polyether antibiotic, was blended with a forage diet at levels of 0, 11, 22 and 33 ppm and fed to steers to determine its effect on cotton fiber, dietary carbohydrate and nitrogen digestibility, on numbers of rumihal microbes, and on concentration of ruminal volatile fatty acids. No differences (P>.10) in cellulose digestibility from cotton were observed in response to monensin level when cotton fiber samples were incubated in vitro in ruminal fluid from these steers. Neither were differences in loss of dry matter detectable (P>.10) when cotton fabric strips were placed within the rumens of steers for 72 hours. In v/vo digestion of dry matter, crude protein, hemicellulose and cellulose of the forage diet was not different (P>.05) among treatments. Total ruminal volatile fatty acid concentration was not affected by feeding monensin, but the molar proportion of acetic acid decreased (P<.01) from 66.7 to 61.3% and that of propionic acid increased (P<.01) from 20.1 to 26.1%. No other volatile fatty acids were affected. Neither the numbers of protozoa, total bacteria nor cellulolytic bacteria in rumihal fluid were affected by feeding up to 33 ppm dietary monensin.

Certain metals added as salts to a defined basal culture medium influenced the level of aflatoxin production by Aspergillus parasiticus in the low microgramsper-milliliter range of the added metal. In many cases no change or a relatively small change in mat weight and final pH of the medium accompanied this effect. With zinc at added levels of 0 to 10 Ag/ml in the medium, aflatoxin increased 30to 1,000-fold with increasing of zinc, whereas mat weight increased less than threefold. At 25 gg of added zinc per ml, aflatoxin decreased, but mat weight did not. At an added level of 25 ,gg or less of the metal per ml, salts of iron, manganese, copper, cadmium, trivalent chromium, silver, and mercury partly or completely inhibited aflatoxin production, without influencing mat weight.

A quantitative technique has been developed in which a weighed sample of cotton fiber is swollen in sodium hydroxide, centrifuged to remove liquid from between the fibers, and re weighed to determine its percentage increase in weight, the latter quantity being designated here as the fiber's "alkali-centrifuge value." The results obtained have been found to be related to two types of causal factors—namely, (1) the prior action of deteriorative agencies on the fiber, apparently especially on the outer wall of the fiber, and (2) the wall thickness of the fiber (as reflected in arealometer air-flow measurements). The fiber-deteriorative agencies which have been shown to bring about changes in the alkali-centrifuge value of cotton fiber include micro-organisms, certain enzymatically active filtrates from microbial growth media, sodium hypochlorite, hydrochloric acid, heat, and weathering. The microbial and enzymatic effects have been studied in more detail than the others. The new test is simple, rapid, inexpensive, quite highly reproducible, involves only standard laboratory equipment, and is essentially free from safety hazards to the operator. Several aspects of the methodology of the test are reported.

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Cotton seeds (Gossypium hirsutum L.) from 13 locations across the US Cotton Belt in 1969 and 11 locations in 1970 were analyzed for aflatoxins. Samples from most locations did not exhibit detectable aflatoxin contamination. However, aflatoxins Bj and B 2 were found in one or more samples collected near Brawley, California; Phoenix, Arizona; and Weslaco, Texas, all in areas where a boll rot caused by Aspergillus flavus Link has been noted repeatedly since the crop of 1953. Aflatoxins occurred especially in seeds whose fiber exhibited a bright greenish yellow (BGY) fluorescence which is diagnostic for this boll rot. When seeds from the 1970 crop were examined for internal fungal infection, A. flavus was detected only in the seeds from Brawley. Free fatty acids were high in seeds from several areas, both with and without accompanying aflatoxins. Weather records indicated that A. flavus boll rot occurs mainly, perhaps exclusively, in conjunction with exceptionally high field temperatures. Additional Index Words: Aspergillus flavus, boll rot, free fatty acid, fluorescence, temperature, mycotoxin.