Three flocks on 13 different broiler farms were monitored for Salmonella over three consecutive growout periods using the drag swab (DS) technique. One house was consistently negative for Salmonella contamination (7.7%); four houses were consistently positive (30.8%); and eight houses (61.5%) alternated between either a DS Salmonella-negative or -positive status. Simultaneously, numerous environmental parameters of the litter surface were measured, including water activity (Aw), ammonia, temperature, pH, moisture content (MC), ash content, and volatile solids. Analysis of these data as a corollary to either Salmonella-negative or -positive DS results revealed significant correlation coefficients for some of the parameters, especially Aw. The results suggest that there should be further exploration of remedial intervention based on control of some of the physical features of litter (e.g., controlling litter Aw and possibly MC and pH levels) in poultry houses.

The manifold pressure below which a diesel engine starts to misfire is related to the cetane number of the fuel. The method of engine throttling to misfire has been used to determine cetane quality of much smaller quantities of diesel fuel than can be used with the standard ASTM D 613 method. A comparison of reliability has been made between the two methods using identical test samples. The fact that published repeatability limits for ASTM D 613-84 are much smaller than the reproducibility limits suggests that there can be considerable bias at some laboratories using the standard method. A method of calibration and computation is presented that provides reliable estimates of the accuracy of misfire pressure results without reference to other laboratories. Confidence intervals determined for the misfire pressure method are consistent with the observed difference in the results determined on the one set of test materials by the two methods. This suggests that, in the procedure for engine throttling to misfire proposed here, the interlaboratory component of error could be small.