Dieldrin toxicity in housed merino sheep.

An outbreak of nervous disease with deaths and reproductive failure was investigated in a fully housed flock of 640 super fine wool (Sharlea) Merino sheep. During the 4 months after the flock was dipped in dieldrin, 70 adult sheep died and no live lambs were produced by the ewes. The diagnosis of poisoning with dieldrin was based upon the presence of characteristic clinical signs, pathological findings and the detection of residues of dieldrin in tissues. Deficiency of vitamin A was confirmed in 2 sheep and may have contributed to the reproductive failure.

Residues in cattle grazed on land contaminated with heptachlor.

Heptachlor epoxide residues exceeding the maximum residue limit of 0.2 mg/kg have been found in fat of cattle grazed on land previously treated with heptachlor prior to planting potatoes or maize. To determine the residues accumulated in cattle exposed to contaminated land and the rate of decline on removal from the contamination, steers were grazed on a former potato paddock which had been treated the 2 previous years with heptachlor at 1.1 kg/ha. Soil residues in the paddock varied from a total of 0.42 mg/kg heptachlor and its epoxide at the beginning of the trial to 0.31 mg/kg after 16 months. Residues in the soil decreased only slightly down to a depth of 300 mm. Pasture residues were less than 0.02 mg/kg (wet basis). Heptachlor epoxide residues in the body fat of the steers increased during 19 months of exposure and reached a maximum of 0.72 mg/kg. In 4 steers removed after 14 weeks exposure, the heptachlor epoxide concentrations continued to increase from a mean of 0.24 mg/kg to a mean of 0.34 mg/kg after a further 4 weeks. Concentrations then fell progressively with a half life of 11 weeks in the body fat. There was an apparent relationship between pasture length and body fat residue, with residues increasing as pasture length decreased. The results of the experiments preclude the option of grazing cattle on pasture grown on soil treated with heptachlor for any extended period of time. It is possible that if short pastures and soft soil are avoided, and if cattle are not exposed to contaminated land for any more than 1 week in each month, then residues would remain below the maximum residue limit of 0.2mg/kg heptachlor.

Behavior of amitraz in cattle dipping baths.

The settling rates of 0.025% w/v amitraz (used as a 50% w/w active ingredient wettable powder) and lime stabiliser (0.7% Ca(OH)2) were studied in cattle dipping baths in the Tick Quarantine Area of northern New South Wales. Although lime settled more rapidly than amitraz, the rate for both decreased as the number of cattle dipped increased. After a total of 1,200 head had been dipped the settling rate during the hour following stirring was negligible, and re-stirring was not necessary within the hour following use. Baths could also be cleaned of heavy sediment by scooping without significant loss of chemicals. When the bath volume was allowed to decrease to 2,100 liters below working volume no significant changes in amitraz and Ca(OH)2 concentrations occurred. Data collected from 796 baths showed a significant concentration change of +0.00066% amitraz and -0.017% Ca (OH)2 per 1,000 head of cattle. Replenishment per 700 liters of water with 254 g amitraz was found to be in good agreement with 250 g recommended by the manufacturer, while 12.53 kg for lime was substantially more than the 10 kg recommended.

Quickfit Florisil pesticide trap for use with assisted distillation technique.

A quickfit Florisil pesticide trap is described for use with the assisted distillation technique for the cleanup of pesticide residues in fats. Recoveries of 80--100% were obtained for 9 pesticides. No cooling is needed and there is no measurable carryover of fat from this Florisil trap.