Cattle Grub Control with Feed Additives (Coumaphos and Fenthion) and Pour-ons (Fenthion and Trichlorfon)1

Abstract

The effectiveness of 3 organic phosphorus compounds (coumaphos, fenthion, trichlorfon) against the common cattle grub. Hypoderma lineatum (de Villers), and the cattle grub, H. bovis (L.), was investigated. A 133-day feedlot trial consisted of 216 calves used in 6 feed-additive treatment groups, 1 pour-on treatment group, and a control group. Forty-four additional calves received 3 pour-on treatments in a separate 133-day trial. The control group (48 animals) averaged 20 grubs per head. All 6 feed additive treatments and the 4 pour-on treatments significantly (P < 0.05) reduced the number of grubs present, as compared with an average of the peak grub count of individual animals in the control group. The reductions of grub counts by the feed additive treatments were: 3 mg per kg and 4 mg per kg coumaphos daily. 6 days-56%, 90%; 1 mg per kg and 1.5 mg per kg fenthion daily, 6 days-92 %, 98%; and 2 mg per kg and 3 mg per kg fenthion daily, 3 days-86%, 90%. The pour-on treatments, applied once at a rate of Y2 fl oz per 100 lb, gave results as follows: 8% and 12% trichlorfon—96%, 95%; and 1 % and 2% fenthion—77%, 85%. When the percent control by the various treatments is considered in conjunction with the number of animals free of grubs throughout the trial and those with a peak count of fewer than 5 grubs per head, it appears that fenthion feed additives at 1.0 mg per kg and 1.5 mg per kg per day for 6 days and trichlorfon pour-ons (8%, 12%) were the most satisfactory treatments. No significant differences in total weight gain or overall feed efficiency existed among the treatment groups and the control group. The usual better performance by steers as compared with heifers was observed, but sex of animal had no effect on grub counts.