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The Effect of Dietary Ronidazole on the Growth of Young Chicks and Turkeys
The Effect of Dietary Ronidazole on the Growth of Young Chicks and Turkeys GEORGE OLSON, WALTHER H. OTT AND ANN VAN IDERSTINE Merck Sharp and Dohme Research Laboratories, Rahway, New Jersey (Received for publication April 13, 1970)
EXPERIMENTAL PROCEDURES
Day-old sex-separated chicks and turkeys were obtained from commercial hatcheries and reared in electrically-heated, wire-floored metal batteries in temperaturecontrolled rooms in a masonry building with cement slab floor and roof. The experimental rooms were cleaned, fumigated and
RONIDAZOLE
0 II -CH2-0—C-NH2
0 2 NI CH3
(l-Methyl-5-nitroimidazol-2-yl) methyl carbamate FIG. 1. Chemical structure of ronidazole.
washed with hot water prior to each experiment. Under these conditions of operation, no bacterial or viral disease has been recognized clinically during the past 15 years. Commercial corn-soybean type chick or turkey starter diets were employed as the basal ration. All diets for one experiment were mixed from one blended lot of basal. The medication was pre-mixed into a small quantity of basal and then the pre-mix was incorporated into the experimental diet. For each experiment, at least 50% morebirds were available than were required for> the experiment. These birds were reared to 3 days of age in the case of chicks, and to 6 days of age in the case of turkeys, and then were weighed and the middle portion of the weight distribution was divided into groups of 4 or 5 birds each, on an equal-weight basis. The groups of birds and the experimental diets were randomly assigned to the pen locations. Replicate groups within each treatment consisted of one pen of males and one pen of females. Weight gain to 3 or 4 weeks of age was used as the critical cri-
1291
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
ONIDAZOLE [ (l-methyl-5-nitroimi- dazol-2-yl)methylcarbamate, Figure 1 ] is a new drug, effective for the prevention of histomoniasis in turkeys (Peterson, 1968; Whitmore et al., 1968). The turkeys fed ronidazole at levels of 0.003%, 0.006% and 0.012% from one day to 25 weeks of age were reported to have significantly improved body weight gains (Sullivan et al., 1968). Previous studies with dimetridazole (Condren et al., 1963) demonstrated a significant growth improvement in turkeys receiving dietary levels of 0.025% to 0.05% from one day to 8 weeks of age. Moeller (1967) reported that dimetridazole improved the growth rate and feed efficiency of swine. A recent study (Cox et al., 1970) demonstrated that pigs fed 0.003%, 0.006% or 0.012% ronidazole gained faster and more efficiently than pigs receiving a non-medicated control diet. Four series of experiments were conducted in this laboratory to measure the effect of ronidazole on the growth of young non-infected chicks and turkeys and to establish the safety of this compound for use in poultry. Two nitrogen retention experiments were conducted to determine if ronidazole was an anabolic agent.
R
1292
G. OLSON, W. H. OTT AND A. VAN IDERSTINE
RESULTS AND DISCUSSION The first series of experiments consisted of feeding graded levels of ronidazole, ranging from 0.0015% to 0.2% to chicks from 3 days to 3 weeks of age to determine the maximum concentration of ronidazole that could be incorporated into the diet without adversely affecting weight gain. The results of these experiments (Figure 2) show that the maximum tolerated concentration (MTC) of ronidazole was 0.042% in the diet of chicks. Dietary levels of ronidazole below the MTC resulted in an average relative percent weight gain of 1.2% less than the non-medicated controls. However, the 95% confidence interval ( ± 1.4%) around this average weight gain includes the average weight gain of the non-medicated control chicks. Thus, these results show that dietary levels of 0.04% or less ronidazole have neither detrimental nor beneficial
effect on weight gain in chicks. Feeding levels of ronidazole above 0.04% resulted in growth depressions reaching a maximum of 51% when a level of 0.2% was fed. However, even at this highest level of supplementation no mortality or particular syndrome was observed. The second series of experiments consisted of feeding graded levels of ronidazole ranging from 0.003% to 0.16% to turkeys from 6 days to 4 weeks of age. As shown in Figure 3, the MTC was found to be 0.04%. Dietary levels of ronidazole above 0.04% resulted in growth depressions reaching a maximum of approximately 50% when a level of 0.16% was fed. Thus it was found that the MTC and growth depression curves obtained for turkeys were essenEFFECT OF FEEDING RONIDAZOLE ON THE GROWTH OF CHICKS
O.OOI5
0.003 0.006 O.OI O.02 0.04 0.07 0.1 PERCENT RONIDAZOLE IN FEED
0.2
FIG. 2. Effect of feeding ronidazole upon the growth of chicks from | to 3 weeks of age. Each dot represents the relative percent weight gain of 1 pen of 4 or 5 chicks. The horizontal line represents the average weight gain of 68 pens of control chicks (100% = 320 g.). The horizontal dash lines are the 0.95 probability confidence limits for the average growth response (—1.2%) of 83 pens of chicks fed 0.0015 to 0.03% ronidazole. The sloping lines are the dose response curve (solid line) and its 0.95 probability confidence limits (dash lines) for growth responses of 34 pens of chicks fed 0.04% to 0.2% ronidazole. The equation of the dose response curve is Y = —107.0—79.0 X, where X = log percent dietary ronidazole and Y = relative percent weight gain.
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
terion of measurement. Feed and water were supplied ad libitum in all growth studies. In the nitrogen retention experiments, four 3-week-old male turkeys were randomly allotted on an equal-weight basis to each of the experimental pens. In each experiment, 3 pens received the non-medicated control diet and 3 pens received a diet containing 0.012% ronidazole. Feed consumption was recorded during the 5-day pre-experimental period. During the experiment, all pens were limited to the quantity of feed consumed by the pen of turkeys eating the least the preceding day. Total excreta were collected in a dilute acid solution during the experiment. The excreta were homogenized, dried and the nitrogen content was measured by the Kjeldahl method. Statistical analyses involved the use of the analysis of variance (Snedecor and Cochran, 1967) and the calculation of confidence intervals for dose response curves as outlined by Bliss (1951).
1293
RONIDAZOLE AND GROWTH
EFFECT OF FEEDING RONIDAZOLE ON THE GROWTH OF TURKEYS
_ .
•
.
f
• • • ._..-i—t«o
- 1 — : — T
-J—,--0
/
\•
s
I
% % \
1 1 1 1 i i i 0.003 0.006 0.01 0.02 0.04 0 0 7 0.1 PERCENT RONIDAZOLE IN FEED
s
\\ \ 1 0.2
FIG. 3. Effect of feeding ronidazole upon the growth of turkeys from \ to 3 or 4 weeks of age. Each dot represents the relative percent weight gain of 1 pen of 4-5 turkeys. The horizontal solid line represents the average weight gain of 47 pens of control turkeys (100% = 380 g.). The horizontal dash lines are the 0.95 probability confidence limits for the average growth response (+2.2%) of 29 pens of turkeys fed 0.003% to 0.03% ronidazole. The sloping lines are the dose response curve (solid line) and its 0.95 probability confidence limits (dash lines) for growth responses of 30 pens of (urkeys fed 0.04% to 0.16% ronidazole. The equation of the dose response curve is Y = —93.4—67.2 X, where X = log percent of dietary ronidazole and Y = relative percent weight gain.
TABLE 1.—Effect of dietary ronidazole on young turkeys from 1 to 4 weeks of age ,,, Treatment
No. of Turkeys
Control 0.006% Ronidazole 0.012% Ronidazole
Avg. Wt. &.„
Feed per ^
64
496.6 g.
64
508.5 (+2.4)* 1.56 (-1.9)
64
518.2 (+4.5)
1.59 g./g.
1.55 (-2.6)
* Relative percent of the appropriate control group.
tion of histomoniasis in turkeys. The cumulative growth data of these four experiments are presented in Table 1. Statistical analysis of these data demonstrated a significant (P <0.0S) treatment effect. Further analysis showed a significant (P <0.0S) linear growth response as the ronidazole level was increased from 0 to 0.012% in the diet. These results confirmed those obtained in the preceding series of experiments with turkeys. Analysis of the feed efficiency data (Table 1) showed no significant differences among treatments. However, in general, the feed efficiency appeared to improve as the weight gain increased. The significant increase in growth observed in non-infected turkeys reared in clean quarters with no clinical symptoms of disease raised the possibility that dietary ronidazole was an anabolic agent. Two nitrogen retention experiments were conducted to test this possibility. The results of these experiments (Table 2) show that the average nitrogen retained by the nonmedicated turkeys was 52.7% as compared
TABLE 2.—Effect of dietary ronidazole on nitrogen retention in turkeys Percent Nitrogen Retained Treatment Control 0.012% Ronidazole
Exp. 1
Exp. 2
Avg.
53.37 54.08
52.03 51.81
52.70 52.94
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
tially identical to those observed in chicks. However, when levels of ronidazole below 0.04% were fed to turkeys, an average growth improvement of +2.2% above the non-medicated controls was observed. The 95% confidence interval around this average growth improvement was ± 1.9%, which indicated a true growth response. This observation is in contrast to that observed in chicks. To investigate further this apparent improved growth of turkeys fed levels of ronidazole below the MTC, a series of 4 experiments was conducted. Levels of 0.006% and 0.012% ronidazole were selected for these experiments on the basis of efficacy data which had demonstrated these were effective levels of ronidazole for the preven-
1294
G. OLSON, W. H. OTT AND A. VAN IDEESTINE
SUMMARY
A series of experiments was conducted to measure the effect of dietary ronidazole on the growth of young chicks and turkeys. The maximum dietary concentration of ronidazole that could be fed without adversely affecting growth was found to be approximately 0.04% for both chicks and
turkeys. Dietary levels of 0.006% and 0.012% ronidazole significantly improved the growth of non-infected turkeys, but had no effect on the growth of chicks. Nitrogen retention studies showed that the increased weight gain in turkeys was not due to an anabolic response. REFERENCES Bliss, C. I., 1951. Statistical methods in vitamin research. Vitamin Methods, I I : 445-610. Academic Press Inc., New York, New York. Condren, H. B., R. E. Davies, C. W. Deyoe, M. A. Zavala, C. R. Creger and J. R. Couch, 1963. Studies on the effect of l,2-dimethyl-5-nitroimidazole on growth and reproduction in turkeys and its residual concentration in tissue. Poultry Sci. 42: 585-594. Cox, J. L., W. H. Ott and W. R. Cobb, 1970. Performance of pigs fed graded levels of ronidazole. J. Animal Sci. 3 1 : 470-473. Moeller, M. W., 1967. Effect of dimetridazole on rate of gain and feed efficiency of swine. J. Animal Sci. 26: 64-66. Peterson, E. H., 1968. The efficacy of l-methyl-2carbamoyloxy-methyl-5-nitroimidazole against enterohepatitis in experimental poults. Poultry Sci. 47: 1245-1254. Peterson, E. H., 1969. The efficacy of l-methyl-2carbamoyloxy-methyl-5-nitroimidazole against Arizona paracolon 7: 1,7,8 infection in experimental poults. Poultry Sci. 48: 1206-1208. Skelly, B. J., J. Kosowsky, W. York and D. Hendlin, 1969. Efficacy of ronidazole in CRD. I. Prophylaxis in turkey laboratory infections. Bacterid Proc. 69 : 86. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th Edition, Iowa State University Press, Ames, Iowa. Sullivan, T. W., O. D. Grace and R. J. Mitchell, 1968. Therapeutic efficacy of ronidazole in water against histomoniasis and effect of continuous feed levels on growth of turkeys. Poultry Sci. 47: 1724. Whitmore, J. H., T. W. Sullivan and O. D. Grace, 1968. Prophylactic efficacy of l-methyl-2-carbamoyloxy-methyl-5-nitroimidazole against histomoniasis in young turkeys. Poultry Sci. 47: 428-430.
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
to 52.9% for the turkeys receiving 0.012% dietary ronidazole. Since the nitrogen retained in both treatments was essentially identical, it is apparent that ronidazole is not an anabolic agent for turkeys. These results coincide with those of Cox et al. (1970) who reported that dietary ronidazole had no effect on either nitrogen digestability or nitrogen retention in swine. The mechanism by which ronidazole improves the growth of turkeys has not been established. The lack of an anabolic effect and the absence of clinical symptoms of disease in these experiments make a specific explanation of the growth response impossible at the present time. However, Skelly et al. (1969) have reported that dietary ronidazole was effective in controlling the development of CRD in turkeys infected with three strains of Mycoplasma gallisepticum. Peterson (1969) reported that ronidazole, administered in either the feed or drinking water, was effective in reducing mortality in turkeys infected subcutaneously with Arizona paracolon-7. While no clinical signs of disease were apparent in the turkeys used in the experiments reported here, it is possible that the birds were harboring a sub-clinical infection caused by some microorganism which is sensitive to ronidazole and that this is the mechanism that resulted in the growth response.
EXPERIMENTAL PROCEDURES
Day-old sex-separated chicks and turkeys were obtained from commercial hatcheries and reared in electrically-heated, wire-floored metal batteries in temperaturecontrolled rooms in a masonry building with cement slab floor and roof. The experimental rooms were cleaned, fumigated and
RONIDAZOLE
0 II -CH2-0—C-NH2
0 2 NI CH3
(l-Methyl-5-nitroimidazol-2-yl) methyl carbamate FIG. 1. Chemical structure of ronidazole.
washed with hot water prior to each experiment. Under these conditions of operation, no bacterial or viral disease has been recognized clinically during the past 15 years. Commercial corn-soybean type chick or turkey starter diets were employed as the basal ration. All diets for one experiment were mixed from one blended lot of basal. The medication was pre-mixed into a small quantity of basal and then the pre-mix was incorporated into the experimental diet. For each experiment, at least 50% morebirds were available than were required for> the experiment. These birds were reared to 3 days of age in the case of chicks, and to 6 days of age in the case of turkeys, and then were weighed and the middle portion of the weight distribution was divided into groups of 4 or 5 birds each, on an equal-weight basis. The groups of birds and the experimental diets were randomly assigned to the pen locations. Replicate groups within each treatment consisted of one pen of males and one pen of females. Weight gain to 3 or 4 weeks of age was used as the critical cri-
1291
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
ONIDAZOLE [ (l-methyl-5-nitroimi- dazol-2-yl)methylcarbamate, Figure 1 ] is a new drug, effective for the prevention of histomoniasis in turkeys (Peterson, 1968; Whitmore et al., 1968). The turkeys fed ronidazole at levels of 0.003%, 0.006% and 0.012% from one day to 25 weeks of age were reported to have significantly improved body weight gains (Sullivan et al., 1968). Previous studies with dimetridazole (Condren et al., 1963) demonstrated a significant growth improvement in turkeys receiving dietary levels of 0.025% to 0.05% from one day to 8 weeks of age. Moeller (1967) reported that dimetridazole improved the growth rate and feed efficiency of swine. A recent study (Cox et al., 1970) demonstrated that pigs fed 0.003%, 0.006% or 0.012% ronidazole gained faster and more efficiently than pigs receiving a non-medicated control diet. Four series of experiments were conducted in this laboratory to measure the effect of ronidazole on the growth of young non-infected chicks and turkeys and to establish the safety of this compound for use in poultry. Two nitrogen retention experiments were conducted to determine if ronidazole was an anabolic agent.
R
1292
G. OLSON, W. H. OTT AND A. VAN IDERSTINE
RESULTS AND DISCUSSION The first series of experiments consisted of feeding graded levels of ronidazole, ranging from 0.0015% to 0.2% to chicks from 3 days to 3 weeks of age to determine the maximum concentration of ronidazole that could be incorporated into the diet without adversely affecting weight gain. The results of these experiments (Figure 2) show that the maximum tolerated concentration (MTC) of ronidazole was 0.042% in the diet of chicks. Dietary levels of ronidazole below the MTC resulted in an average relative percent weight gain of 1.2% less than the non-medicated controls. However, the 95% confidence interval ( ± 1.4%) around this average weight gain includes the average weight gain of the non-medicated control chicks. Thus, these results show that dietary levels of 0.04% or less ronidazole have neither detrimental nor beneficial
effect on weight gain in chicks. Feeding levels of ronidazole above 0.04% resulted in growth depressions reaching a maximum of 51% when a level of 0.2% was fed. However, even at this highest level of supplementation no mortality or particular syndrome was observed. The second series of experiments consisted of feeding graded levels of ronidazole ranging from 0.003% to 0.16% to turkeys from 6 days to 4 weeks of age. As shown in Figure 3, the MTC was found to be 0.04%. Dietary levels of ronidazole above 0.04% resulted in growth depressions reaching a maximum of approximately 50% when a level of 0.16% was fed. Thus it was found that the MTC and growth depression curves obtained for turkeys were essenEFFECT OF FEEDING RONIDAZOLE ON THE GROWTH OF CHICKS
O.OOI5
0.003 0.006 O.OI O.02 0.04 0.07 0.1 PERCENT RONIDAZOLE IN FEED
0.2
FIG. 2. Effect of feeding ronidazole upon the growth of chicks from | to 3 weeks of age. Each dot represents the relative percent weight gain of 1 pen of 4 or 5 chicks. The horizontal line represents the average weight gain of 68 pens of control chicks (100% = 320 g.). The horizontal dash lines are the 0.95 probability confidence limits for the average growth response (—1.2%) of 83 pens of chicks fed 0.0015 to 0.03% ronidazole. The sloping lines are the dose response curve (solid line) and its 0.95 probability confidence limits (dash lines) for growth responses of 34 pens of chicks fed 0.04% to 0.2% ronidazole. The equation of the dose response curve is Y = —107.0—79.0 X, where X = log percent dietary ronidazole and Y = relative percent weight gain.
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
terion of measurement. Feed and water were supplied ad libitum in all growth studies. In the nitrogen retention experiments, four 3-week-old male turkeys were randomly allotted on an equal-weight basis to each of the experimental pens. In each experiment, 3 pens received the non-medicated control diet and 3 pens received a diet containing 0.012% ronidazole. Feed consumption was recorded during the 5-day pre-experimental period. During the experiment, all pens were limited to the quantity of feed consumed by the pen of turkeys eating the least the preceding day. Total excreta were collected in a dilute acid solution during the experiment. The excreta were homogenized, dried and the nitrogen content was measured by the Kjeldahl method. Statistical analyses involved the use of the analysis of variance (Snedecor and Cochran, 1967) and the calculation of confidence intervals for dose response curves as outlined by Bliss (1951).
1293
RONIDAZOLE AND GROWTH
EFFECT OF FEEDING RONIDAZOLE ON THE GROWTH OF TURKEYS
_ .
•
.
f
• • • ._..-i—t«o
- 1 — : — T
-J—,--0
/
\•
s
I
% % \
1 1 1 1 i i i 0.003 0.006 0.01 0.02 0.04 0 0 7 0.1 PERCENT RONIDAZOLE IN FEED
s
\\ \ 1 0.2
FIG. 3. Effect of feeding ronidazole upon the growth of turkeys from \ to 3 or 4 weeks of age. Each dot represents the relative percent weight gain of 1 pen of 4-5 turkeys. The horizontal solid line represents the average weight gain of 47 pens of control turkeys (100% = 380 g.). The horizontal dash lines are the 0.95 probability confidence limits for the average growth response (+2.2%) of 29 pens of turkeys fed 0.003% to 0.03% ronidazole. The sloping lines are the dose response curve (solid line) and its 0.95 probability confidence limits (dash lines) for growth responses of 30 pens of (urkeys fed 0.04% to 0.16% ronidazole. The equation of the dose response curve is Y = —93.4—67.2 X, where X = log percent of dietary ronidazole and Y = relative percent weight gain.
TABLE 1.—Effect of dietary ronidazole on young turkeys from 1 to 4 weeks of age ,,, Treatment
No. of Turkeys
Control 0.006% Ronidazole 0.012% Ronidazole
Avg. Wt. &.„
Feed per ^
64
496.6 g.
64
508.5 (+2.4)* 1.56 (-1.9)
64
518.2 (+4.5)
1.59 g./g.
1.55 (-2.6)
* Relative percent of the appropriate control group.
tion of histomoniasis in turkeys. The cumulative growth data of these four experiments are presented in Table 1. Statistical analysis of these data demonstrated a significant (P <0.0S) treatment effect. Further analysis showed a significant (P <0.0S) linear growth response as the ronidazole level was increased from 0 to 0.012% in the diet. These results confirmed those obtained in the preceding series of experiments with turkeys. Analysis of the feed efficiency data (Table 1) showed no significant differences among treatments. However, in general, the feed efficiency appeared to improve as the weight gain increased. The significant increase in growth observed in non-infected turkeys reared in clean quarters with no clinical symptoms of disease raised the possibility that dietary ronidazole was an anabolic agent. Two nitrogen retention experiments were conducted to test this possibility. The results of these experiments (Table 2) show that the average nitrogen retained by the nonmedicated turkeys was 52.7% as compared
TABLE 2.—Effect of dietary ronidazole on nitrogen retention in turkeys Percent Nitrogen Retained Treatment Control 0.012% Ronidazole
Exp. 1
Exp. 2
Avg.
53.37 54.08
52.03 51.81
52.70 52.94
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
tially identical to those observed in chicks. However, when levels of ronidazole below 0.04% were fed to turkeys, an average growth improvement of +2.2% above the non-medicated controls was observed. The 95% confidence interval around this average growth improvement was ± 1.9%, which indicated a true growth response. This observation is in contrast to that observed in chicks. To investigate further this apparent improved growth of turkeys fed levels of ronidazole below the MTC, a series of 4 experiments was conducted. Levels of 0.006% and 0.012% ronidazole were selected for these experiments on the basis of efficacy data which had demonstrated these were effective levels of ronidazole for the preven-
1294
G. OLSON, W. H. OTT AND A. VAN IDEESTINE
SUMMARY
A series of experiments was conducted to measure the effect of dietary ronidazole on the growth of young chicks and turkeys. The maximum dietary concentration of ronidazole that could be fed without adversely affecting growth was found to be approximately 0.04% for both chicks and
turkeys. Dietary levels of 0.006% and 0.012% ronidazole significantly improved the growth of non-infected turkeys, but had no effect on the growth of chicks. Nitrogen retention studies showed that the increased weight gain in turkeys was not due to an anabolic response. REFERENCES Bliss, C. I., 1951. Statistical methods in vitamin research. Vitamin Methods, I I : 445-610. Academic Press Inc., New York, New York. Condren, H. B., R. E. Davies, C. W. Deyoe, M. A. Zavala, C. R. Creger and J. R. Couch, 1963. Studies on the effect of l,2-dimethyl-5-nitroimidazole on growth and reproduction in turkeys and its residual concentration in tissue. Poultry Sci. 42: 585-594. Cox, J. L., W. H. Ott and W. R. Cobb, 1970. Performance of pigs fed graded levels of ronidazole. J. Animal Sci. 3 1 : 470-473. Moeller, M. W., 1967. Effect of dimetridazole on rate of gain and feed efficiency of swine. J. Animal Sci. 26: 64-66. Peterson, E. H., 1968. The efficacy of l-methyl-2carbamoyloxy-methyl-5-nitroimidazole against enterohepatitis in experimental poults. Poultry Sci. 47: 1245-1254. Peterson, E. H., 1969. The efficacy of l-methyl-2carbamoyloxy-methyl-5-nitroimidazole against Arizona paracolon 7: 1,7,8 infection in experimental poults. Poultry Sci. 48: 1206-1208. Skelly, B. J., J. Kosowsky, W. York and D. Hendlin, 1969. Efficacy of ronidazole in CRD. I. Prophylaxis in turkey laboratory infections. Bacterid Proc. 69 : 86. Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods, 6th Edition, Iowa State University Press, Ames, Iowa. Sullivan, T. W., O. D. Grace and R. J. Mitchell, 1968. Therapeutic efficacy of ronidazole in water against histomoniasis and effect of continuous feed levels on growth of turkeys. Poultry Sci. 47: 1724. Whitmore, J. H., T. W. Sullivan and O. D. Grace, 1968. Prophylactic efficacy of l-methyl-2-carbamoyloxy-methyl-5-nitroimidazole against histomoniasis in young turkeys. Poultry Sci. 47: 428-430.
Downloaded from http://ps.oxfordjournals.org/ at Yale University on May 18, 2015
to 52.9% for the turkeys receiving 0.012% dietary ronidazole. Since the nitrogen retained in both treatments was essentially identical, it is apparent that ronidazole is not an anabolic agent for turkeys. These results coincide with those of Cox et al. (1970) who reported that dietary ronidazole had no effect on either nitrogen digestability or nitrogen retention in swine. The mechanism by which ronidazole improves the growth of turkeys has not been established. The lack of an anabolic effect and the absence of clinical symptoms of disease in these experiments make a specific explanation of the growth response impossible at the present time. However, Skelly et al. (1969) have reported that dietary ronidazole was effective in controlling the development of CRD in turkeys infected with three strains of Mycoplasma gallisepticum. Peterson (1969) reported that ronidazole, administered in either the feed or drinking water, was effective in reducing mortality in turkeys infected subcutaneously with Arizona paracolon-7. While no clinical signs of disease were apparent in the turkeys used in the experiments reported here, it is possible that the birds were harboring a sub-clinical infection caused by some microorganism which is sensitive to ronidazole and that this is the mechanism that resulted in the growth response.