,o-,
Everglades Station Mimeo Report EES65-24 April 1965
THIABENDAZOLE: A CATTLE DEWORMER /
C. E. Haines /
For many years, cattlemen have depended on phenothiazine a, e
main anthelmintic material for their cattle. However, a search
continued for a material that will be more effective against a gr tk
er variety of internal parasites and also be more palatable than ph
thiazine. A new material (thiabendazole) that may meet these require-
ments for an anthelmintic is now available. To test the anthelmintic
properties of thiabendazole, a group of crossbred yearling steers were
used at the Everglades Experiment Station.
Procedure
Eighty steers of Angus x Hereford x Brahman breeding were divided
into four equal groups of 20 animals. Each group received a different
rate of a concentrate mixture continuously while grazing on Roselawn
St. Augustinegrass pastures. Half of the steers in each nutritional
treatment were given thiabendazole at the rate of 3 grams per hundred
pounds of body weight. The material was administered by drench in
November, December, January and February. A month prior to the ini-.
tial test treatment, all steers in each group had been drenched with
phenothiazine.
The steers had an average weight of 543 pounds at the beginning
of the trial. The initial parasitic populations as measured by the
number of eggs per gram of feces (EPG), showed.some variations between
anthelmintic test groups within the nutritional treatment groups. This
resulted from the procedure of allotment by weight prior to parasitic
infestation determinations. The overall average initial number of EPG
was 143 for the treated groups compared to 172 EPG for the non-treated
groups. Animal weights and EPG counts which were obtained six months
after the initial administration of thiabendazole were used for deter-
mining its' effectiveness.
Although thiabendazole may be cheaper if purchased in large quan-
tities through certain commercial companies, the local retail price is
approximately $0.08 per gram. To present this information so that it
might be suitable for all sizes of cattle operations, the higher cost
of $0.08 has been used in computing the economical aspects of the anthel-
mintic treatment. Since each steer received from 15 to 18 grams of the
material per treatment, the cost of each treatment was between $1.20. and
$1.44 per steer. Thus, by using an average figure of $1.32 per treat-
ment and a total of four treatments per steer the total cost of the test
/ Thiabendazole supplied by Merck Sharp and Dohme, Research Laboratories,
Rahway, N. J. The trade name for thiabendazole is Thibenzole (TBZ).
Assistant Animal Husbandman, Everglades Experiment Station, Belle
Glade, Florida.
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
may be improved by this new anthelmintic if maximum nutritional levels
are not provided. If maximum well balanced nutrient intakes are main-
tained then the beneficial effects of thiabendazole appear to be re-
duced. These data also suggested that responses to thiabendazole oc-
curred under low levels of parasite infestation and even after the use
of phenothiazine.
Table 1. Average Gains of Steers Being
out Thiabendazole.
Fed on Pasture With and With-
Concentrate Feed/Day Full 10 lbs. 5 lbs. None
With Thiabendazole
Number of steers 10 10 10 10
Initial weight (Ibs.) 543 544 544 543
Final weight (Ibs.) 849 781 712 602
Total gain (lbs.) 306 237 168 59
% increase 56.4 43.6 30.9 10.9
No Thiabendazole
Number of steers 10 10 10 10
Initial weight (lbs.) 546 543 547 544
Final weight (lbs.) 855 736 704 571
Total gain (lbs.) 309 193 157 27
% increase 56.6 35.5 28.7 5.0
Table 2. Average EPG Counts of Steers Being Fed on Pasture With and
Without Thiabendazole.
Concentrate Feed/Day Full 10 lbs. 5 lbs. None
With Thiabendazole
Number of steers 5 5 5 5
Initial EPG 143 260 91 78
Final EPG 13 26 65 26
Total Decrease 130 234 26 52
% reduction 90.9 90.0 28.6 66.7
No Thiabendazole
Number of steers 5 5 5 5
Initial EPG 273 52 299. 65
Final EPG 156 0 78 52
Total decrease 117 52 221 13
% reduction 42.9 100.0 73.9 20.0
EES65-24
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