In general, commercial laboratories show a lack of proficiency in testing for Giardia and Cryptosporidium. The authors conducted a blind survey of 16 commercial laboratories in order to evaluate their ability to test for Giardia and Cyptosporidium using the American Society for Testing and Materials (ASTM) method. After filters were spiked with approximately 740 Giardia cysts and Cyptosporidium oocysts or 500 cells of the alga Oocystis, they were sent to the laboratories for analysis. For the laboratories that submitted reports, Giardia cyst recoveries ranged from 0.8 to 22.3 percent, averaging 9.1 percent; Cyptosporidium oocyst recoveries ranged from 1.3 to 5.5 percent, averaging 2.8 percent. Four of the laboratories falsely reported the Oocystis as positive, four laboratories failed to recover the Giardia cysts, and six laboratories failed to recover the Cryptosporidium oocysts. Not all laboratories strictly followed the ASTM method. The majority of laboratories need to make improvements in one or more of the following areas: response to clients, adequacy of sampling equipment and directions for use, analytical methods, and data accuracy.

No abstract

Propionic acid at all levels tried (0.125, 0.25, 0.5, 1.0 and 2.0 mg/g of substrate) decreased the total mold count of poultry feed of 15 or 20% H2O content, but increased the count at 25 or 30% H2O content. The paradoxical effect which was time-dependent could be explained on the basis that the total mold count reflected the status of spores rather than the total fungal activity. Assessments of antifungal activity based on respiratory activity, such as weight loss of substrate, heat production and changes in CO2, O2, and H2O content of feed but not pH, did not display such paradoxical behavior. Measurement of CO2 production from feed and ingredients for assessment of antifungal agents was preferred for its ease, speed, economy, accuracy and precision. The findings that most of the CO2 was produced aerobically (assuming a respiratory quotient of 1.0), that yeasts, bacteria, and some fungi produced some CO2 anaerobically, that selective inhibitors of isolates from com meal could not differentiate the production of CO2 from corn meal by bacteria, yeast and fungi, that all three types of microorganisms were active at water concentrations likely to occur in stored feed and ingredients, and that differential plate counts revealed increases in all three classes suggested that all three classes are involved in deterioration of feed ingredients. Consequently, antifungal agents used in feed and ingredients need broad antimicrobial activity and the methods for the assessment of antifungal agents should detect this broad spectrum of activity.

No abstract

The inhibition of fungal activity in poultry feed and ingredients by gentian violet was investigated by measuring respiratory CO2 liberated into the headspace gas above samples of feed and ingredients. Inhibition by gentian violet depended on 1) the lot of corn meal, 2) the concentration of gentian violet, 3) the moisture of the substrate, 4) time of incubation, 5) particle sizes of corn meal and gentian violet, and 6) temperature of a short heating episode mimicking the feed-pelleting process. These same factors were reported earlier to control and limit the activity of organic acid mold inhibitors. These results imply that differences between gentian violet and other mold inhibitors used in poultry feed are quantitative rather than qualitative.