Immobilizing European Wild Hogs with Succinylcholine Chloride

Abstract

Sixty-three pen-reared European wild hogs (Sus scrofa) were injected one or several times for a total of 92 injections with succinylcholine chloride at doses ranging from 0.1 to 6.7 mg/lb. Thirtyeight hogs (41 percent) died from overdosages; at the lowest effective level, 0.3 mg/lb, 3 of 13 animals died (23 percent). In only 32 (35 percent) of the observations were the hogs successfully immobilized. The time elapsed from injection to immobilization averaged 97 + 10 seconds (range 3s250 seconds) and that from injection to recovery averaged 25.6 + 7.4 minutes (range 3.S134 minutes). In most casesn hogs that survived the first dose could be immobilized at a wider range of dose levels without mortality. Two animals were unaffected at doses of over 3 mg/lb. An anesthetic index of only 2.6 indicates that succinylcholine chloride has a very narrow safety margin for European wild hogs. Several immobilizing drugs have been tested on the European wild hog in Tennessee. Cap-Chur-Barb3 (pentobarbital scopolamine ) has the advantage of a wide safety margin but has the disadvantage of long preand postimmobilization periods (Henry and Matschke 1968). These were undesirable characteristics in our studies because of the time spent tending the traps, the distance between traps, and the necessity of replacing the hog in the trap overnight to prevent predation by feral dogs or bears, thus rendering the trap inoperative for that night. In this study, succinylcholine chloride, a muscle-relaxant, was evaluated because of its short preand postimmobilization period. Thanks are extended to J. C. Lewis, Research Supervisor, and B. H. Erickson7 UTAEC Agricultural Research Laboratory, Oak Ridge, Tennessee, for reviewing the manuscript. R. H. Conley, L. A. Hunt, J. D. Morris, and D. J. Williams assisted in the collection of data. 1A contribution from Tennessee Federal Aid Project W-34-R, Game Division, Research Section. 2 Present address: Bureau of Sport Fisheries and Wildlife, Wildlife Research Center, Federal Center, Denver, Colorado. 3Palmer Chemical Company, Douglasville, Georgia. PROCEDURES Pen-reared hogs ( progeny of trapped and confined wild hogs) were used in this study. Succinylcholine chloride was injected into the muscles of the hindquarters by a hand syringe. Time at injection and the length of preand postimmobilization periods were recorded for most hogs. When a hog regained its footing, it was considered recovered. Statistical estimates of the dose necessary to immobilize (ED50) or kill (LD50) onehalf of the population were computed by the technique outlined by Litchfield and Wilcoxon (1949). RESULTS AND DISCUSSION Sixty-three hogs were injected at doses ranging from 0.1 to 6.7 mg/lb (Table 1). Some were injected several times, for a total of 92 observations. Action of the drug was similar to that described by Zurowski and Sakowicz (1965), in that the preimmobilization period was very short, averaging 100.0 + 9.4 seconds and ranging from 30 to 250 seconds, and was characterized by tremors over the whole body and bristling of the dorsal guard hairs. The front feet of the animal usually