material was $5.28 per steer in this study. It should be kept in mind,
however, that a lower price for the material and less frequent appli-
cations would both tend to decrease the total cost of thiabendazole to
cattlemen.

 Results

 The average weight gains for the steers in each group are'presented
 in Table 1. Thiabendazole failed to improve the weight gains of steers
 being full fed the concentrate mixture on pasture as both the treated and
 control steers increased in body weight by about 56 percent. However,
 thiabendazole did improve the gains of steers on the three lower levels
 of nutrition. Steers receiving an average of 10 pounds of concentrate
 per head daily gained an average of 44 pounds more when given thiabenda-
 zole while steers treated with thiabendazole on 5 pounds of concentrate
 per head daily gained only 11 pounds more per head than control animals.
 Percentage-wise, the greatest difference in gains was in the group of
 steers on pasture receiving no supplemental feed.- The thiabendazole
 treated animals in this group gained an average of 59 pounds compared to
 27 pounds by control steers; a difference of 32 pounds.

 The EFG counts indicated that there was an.overall low level of para-
 sitic infestation in the steers at the beginning of the trial and through-.
 out the test period. These values are presented in Table 2 and show that
 thiabendazole reduced the parasitic infestation in the full fed group-and
 the group receiving no supplemental feed but not in the two limited fed-
 groups. The figures also show that the parasitic infestation was reduced
 throughout the trial in all groups whether.,they received the anthelmintic
 treatment or not. Some of this variation could have been due to a com-
 bination of biological variations and environmental factors. It is possi-
 ble that the low level of parasitic infestation plus the continual rein-
 festation of the pastures by control animals minimized the EPG differences.

 If steers were selling for $0.20 per pound on the market, additional
 body weight increases of slightly more than 26 pounds would be necessary
 to compensate for the cost of'the thiabendazole used in this study ($5.28).'
 Since thiabendazole did not improve the gains of full fed steers and only
 increased gains by 11 pounds in steers receiving 5 pounds of concentrate
 per day it was not economically advantageous in these groups. However, a
 monetary benefit of $3.60 per steer was realized for thiabendazole treat-
 ed animals receiving 10 pounds of concentrate daily and $1.20 for the steers
 receiving no supplemental feed. It is possible that economic returns might
 have been higher for thiabendazole treatments if fewer doses had been ad--
 ministered and phenothiazine had not been used just prior to the test.

 Conclusion

 The evaluation of thiabendazole as an anthelmintic agent in'this .
study suggested that the plane.of nutrition had some effect on responses.
In general, gains by steers on pasture receiving either limited amounts
of a concentrate feed or no supplemental feed were improved when thia-
bendazole was administered. Thus, the performance of steers on pasture