| Abstrakt: |
Granulated phorate (formerly designated as Thimet) at 1 and 4 pounds actual per acre was applied to each of two plots of established alfalfa immediately following cutting and prior to an irrigation. Hay from these two plots harvested 27 days after treatment, was fed to two groups of five steers each for a 1-month period, while a similar group was fed hay from an untreated plot. All groups received untreated hay for a second month. Cattle fed hay from the 4-pound treatment gained weight at a lesser rate than cattle fed hay from the 1-pound treatment, and these in turn gained at a lesser rate than cattle fed untreated hay. The differences, however, were not significant. These differences were smaller during the second month when only untreated hay was fed to the three groups; however, the reduced number of individuals does not allow a valid comparison for this period. Residue determinations using an electrometric technique involving inhibition of blood plasma cholines terase were made on alfalfa samples taken during the growth period following treatment. Maximum residue concentrations, 390 ± 236 and 520±225 parts per million for the lower and higher treatment rates, respectively, were found on the third day after treatment. Samples from the 1-pound plot showed no residues on the 14th day, while those from the 4-pound rate continued to show residues through the 21st and perhaps through the 25th day. No residues were found in air air-dried hay from the 4-pound plot harvested on the 27th day. Cholinesterase activity of blood samples taken periodically from the steers during the feeding period was determined by a spectrophotometric method. Considerable variation in this activity was found between animals within groups and furthermore between sampling dates on individual animals. No evidence was found to indicate that blood cholinesterase activity was appreciably affected by the ingestion of hay from either of the two treatments. |
