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The Influence of Thiouracil on Growth, Fattening, Feed Consumption and Thyroid Weight of Turkey Broilers1
The Influence of Thiouracil on Growth, Fattening, Feed Consumption and Thyroid Weight of Turkey Broilers1 R. M. BLAKELY 2 AND R. W. ANDERSON 3 Dominion Experimental Station, Swift Current, Saskatchewan, Canada (Received for publication August 5, 1948)
HE testing of the value of thiouracil as a fattening agent was undertaken during the course of investigations into the possibility of turkey broiler production. Andrews and Schnetzler (1946) fed varying levels of thiouracil to Barred Rock broilers and reported that thiouracil had a progressively increasing effect on the weight and histology of the thyroid gland when fed at levels up to 0.2 percent for an eight week period. These authors also reported that growth was retarded at all levels but not significantly. Market grade and fat deposition were significantly improved and the efficiency of feed utilization was significantly higher for the thiouracil fed birds. Kempster and Turner (1945) showed that the feeding of thiouracil to New Hampshire broilers for a 36day period reduced the rate of growth and increased the amount of feed required to produce a pound of gain. Blakely4 fed 0.2 percent thiouracil to 19§ week old turkeys for a 40-day period during November 1946 and reported reduced weight gains for both sexes but more particularly for the 1 Contribution from the Poultry Division, Dominion Experimental Farms Service, Canada. 2 Officer-in-charge, Poultry. 3 Student Assistant, Poultry. 4 Annual Report, Dominion Experimental Station, Swift Current, Sask., 1946 (Unpublished).
females. Dressed carcass grades for males were improved by the addition of 0.2 percent thiouracil but in the case of females the control birds graded better than those fed thiouracil. The number of birds slaughtered was too small to make these latter results significant, however. It was also reported that the treated birds did not withstand a sudden drop in temperature to — 22°F. as well as the control birds did. EXPERIMENTAL METHODS
Six-week old turkey poults were randomized into two groups of twenty-five birds each. These birds were placed in a two pen brooder house and had access to outdoor runs where a small amount of green oats was available as green feed. Lot No. 1 was fed an all mash diet. Lot No. 2 was fed the same all mash diet with the addition of 0.1 percent thiouracil. The diets were fed ad lib in open hoppers and water was always available in enclosed founts. Table No. 1 gives the basal ration used in this test. Weekly body weights and feed consumption were recorded. At the conclusion of the 21-day feeding period the birds were slaughtered and their thyroid glands removed and weighed on an analytical balance. The carcasses were then wrapped in waxed paper and heavy manila paper 185
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T
186
R. M. BLAKELY AND R. W. ANDERSON TABLE 1.—Basal ration
TABLE 2.—The effect of feeding 0.1 percent thiouracil on body weights, rate of gain and feed utilization, of 9 week old turkey broilers Lot No.
Mixed Sexes 1 2 Males 1 2 Females 1 2
Ration No.
No. Birds
Body Weight
Average Gain
Feed Consumption/Bird
Pounds Feed/Pound Gain
lbs.
lbs.
lbs.
lbs.
7 7B
25 25
4.04 3.27
2.24 1.51
5.74 4.53
2.56 3.00
7 7B
12 11
4.42 3.49
2.49 1.65
— —
— —
7 7B
13 14
3.68 3.09
2.01 1.38
— —
— —
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
weight data in Table No. 2 shows that the rate of gain was reduced for both males Percent Ingredient and females by the addition of 0.1 percent Ground Wheat 30 thiouracil to the diet. Final body weights 20 Ground Oats for Lot No. 1 (Controls) were 4.04 pounds 15 Ground Barley 18 Meat Meal (50% Protein) compared to 3.27 pounds for Lot No. 2 2 Fish Meal (Thiouracil), being a difference of .77 2 Milk Powder 10 Alfalfa Meal pounds. Weight gain data shows an in1 Ground Limestone crease of .73 pounds in favour of the con1 Steamed Bone Meal 1 Iodized Salt trol group. When males and females were considered separately the males from the 100 Total control group showed an average increase of .84 pounds and the females .63 pounds and quick frozen at — 20°F. They were over the thiouracil fed groups. When exthen held at 0°F. pending the removal of. pressed as percent of the controls the skin samples for fat analyses. At the end average gains for the thiouracil fed males of five months' storage the dressed carand females were 66.26 percent and 68.66 casses were thawed at room temperature. percent respectively. Duplicate skin samples, from one-half to Column No. 6 from Table No. 2 shows one centimeter wide, were removed from clearly that feed consumption per bird across the feather tract on each side of the was reduced in the thiouracil fed group. breast. In the case of one bird it was only possible to remove the left sample owing The reduction amounted to 1.21 pounds to a blemish on the right side. The skin per bird for the 21-day period. The last samples were weighed and placed in test column of this table compares the feedtubes and covered with concentrated HC1. gain ratios. It required 2.56 pounds of They were then submitted to Dr. A. R. G. feed to produce a pound of gain for the Emslie, Chemistry Division, Science Serv- control group and 3.00 pounds to produce ice, Ottawa, for fat analyses. The birds a pound of gain for the thiouracil fed were sexed at the time of removal of the group. Feed consumption data for the different sexes were not recorded. skin samples. Table No. 3 shows the percentage fat of RESULTS AND DISCUSSION the skin samples. The increase in the skin A study of the feed consumption and fat for the thiouracil fed birds (males and
187
INFLUENCE OF THIOURACIL ON TURKEY BROILERS
females combined) is rather remarkable being over 100 percent. It is of interest to note that while the females from the control group showed 1.0 percent more fat than the males that the picture is reversed in the case of the thiouracil fed birds. In this latter group the males showed 1.37 percent more fat than the females. The difference in the increase in fattening, therefore, is 2.37 percent in favor of the males. TABLE 3.—The effect on deposition of skin fat* by the addition of 0.1 per cent thiouracil to the diet of 9 week old turkey poults
Mixed Males Females Difference (M-F)
Lot No. 2 Lot No. 1 0 . 1 % Difference Control Thiouracil
%
%
10.64 10.12 11.12 -1.00
22.10 22.87 21.50 1.37
% 11.46 12.75 10.38 2.37
* Calculations are based on left skin samples in all cases.
Gutteridge's method of comparing the fat content of skin samples taken from the birds before and after feeding trials (Gutteridge, 1937) would have given a much better picture of the actual increase in fattening of males and females but unfortunately this was not possible in this test. Table No. 4 shows the effect on thyroid TABLE 4.-
Lot No.
Mixed Sexes 1 2 Males 1 2 Females 1 2
This experiment was designed to test
-The effect of thyroid weight of 9 week old turkey poults by the addition of 0.1 percent thiouracil to the basal diet
Ration No.
No. Birds
Mean Body Wt.
Ave. Thyroid Weight
Thyroid Wt./lOO gms. BW
gms.
mgs.
mgs.
Increase
7 7B
25 25
1892.5 1599.8
84.384 402.208
4.459 25.140
5.6 times
7 7B
12 11
2081.0 1696.0
94.600 397.400
4.545 23.431
5.1 times
7 7B
13 14
1718.5 1524.4
74.953 403.985
4.361 26.633
6.1 times
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
Sex
size of the addition of 0.1 percent thiouracil to the basal ration. Thyroid weights for thiouracil fed males showed an increase of 5.1 times the controls while the corresponding females showed an increase of 6.1 times the control females. This differs from the findings of Reineke (1947) who stated that the thyroid enlargement induced by the feeding of thiouracil was greatest in 24 week old turkey males. The thyroid weight per 100 grams of body weight for control group is shown as 4.459 milligrams. This is considerably lower than previous figures obtained in this laboratory which showed thyroid weights per 100 grams body weight of 6.72 milligrams and 7.76 milligrams for poults which were 42 days old and 50 days old respectively. The poults in this experiment were 63 days of age when slaughtered. The only explanation offered is that previous figures were obtained from poults which were maintained on a starting ration and were reared entirely in wire floored batteries where they were subjected to considerable artificial illumination, especially during the early weeks of the test. The present group were floor brooded from the 4th week and had access to oat greenfeed during the course of the test.
188
R. M. BLAKKLY AND R. W. ANDERSON
SUMMARY
Six week old turkey poults were fed a growing mash diet, to which was added 0.1 percent thiouracil, during a 21-day feeding trial. A depression in weight gains was recorded for both males and females. In the case of males it was .84 pounds and for females .63 pounds below the corresponding controls. Feed consumption in the thiouracil fed group was 1.21 pounds per bird less than
for the controls but efficiency of feed utilization was slightly lower. Percentage skin fat of the thiouracil fed birds averaged more than double that of the controls. In the case of males it was 2.25 times greater and in the case of females 1.92 times that of the corresponding controls. The feeding of 0.1 percent thiouracil caused increases in thyroid weights per 100 grams body weight, of 5.1 times and 6.1 times, for males and females respectively. ACKNOWLEDGMENTS
Our thanks are due to Dr. A. R. G. Emslie who made the fat analyses on the skin samples and The Lederle Laboratories who so generously supplied the thiouracil used in this test. REFERENCES
Andrews, F. N., and E. E. Schnetzler, 1946. Influence of thiouracil on growth and fattening in broilers. Poultry Sci. 25: 124-129. —• •, 1945. The effect of feeding thiouracil to hens upon the thyroid glands of chicks. Endocrinology 37: 382-384. Gutteridge, H. S., 1937. Methods and rations for fattening poultry. II. Sci. Agri. 18: 198-206. Kempster, H. L., and C. W. Turner, 1945. The effect of feeding thiouracil on the fleshing of New Hampshire broilers. Poultry Sci. 24: 94-96. Mixner, J. P., B. A. Tower, C. W. Upp, 1946. The effect of feeding thiouracil on body weight of New Hampshire cockerels. Poultry Sci. 25: 536-538. Reineke, E. P., J. A. Davidson, L. F. Woterink, and F. N. Barrett, 1946. The effect of thiouracil on fattening turkeys. Poultry Sci. 25:410 (Abstract).
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
the value of thiouracil for the possible improvement in fattening of turkey broilers. The results should be considered in that light. Final weights of the dressed carcasses were significantly lower but there is definite evidence of increased skin fat and consequent improvement in grade and appearance of the carcasses. Gutteridge (1937) has shown that the percentage skin fat has a high degree of correlation to body and abdominal fat in the chicken and it, therefore, can be assumed that the increased skin fat shown in this test indicates corresponding increase in abdominal and body fat. Table No. 2 shows an increase of 0.44 pounds in the pounds of grain required to produce a pound of gain in the thiouracil fed group. It shows also that this group consumed 1.21 pounds of feed less per bird during the 21 days of the test. A study of the economics of turkey broiler production will be necessary to evaluate properly the factors brought out in this test.
HE testing of the value of thiouracil as a fattening agent was undertaken during the course of investigations into the possibility of turkey broiler production. Andrews and Schnetzler (1946) fed varying levels of thiouracil to Barred Rock broilers and reported that thiouracil had a progressively increasing effect on the weight and histology of the thyroid gland when fed at levels up to 0.2 percent for an eight week period. These authors also reported that growth was retarded at all levels but not significantly. Market grade and fat deposition were significantly improved and the efficiency of feed utilization was significantly higher for the thiouracil fed birds. Kempster and Turner (1945) showed that the feeding of thiouracil to New Hampshire broilers for a 36day period reduced the rate of growth and increased the amount of feed required to produce a pound of gain. Blakely4 fed 0.2 percent thiouracil to 19§ week old turkeys for a 40-day period during November 1946 and reported reduced weight gains for both sexes but more particularly for the 1 Contribution from the Poultry Division, Dominion Experimental Farms Service, Canada. 2 Officer-in-charge, Poultry. 3 Student Assistant, Poultry. 4 Annual Report, Dominion Experimental Station, Swift Current, Sask., 1946 (Unpublished).
females. Dressed carcass grades for males were improved by the addition of 0.2 percent thiouracil but in the case of females the control birds graded better than those fed thiouracil. The number of birds slaughtered was too small to make these latter results significant, however. It was also reported that the treated birds did not withstand a sudden drop in temperature to — 22°F. as well as the control birds did. EXPERIMENTAL METHODS
Six-week old turkey poults were randomized into two groups of twenty-five birds each. These birds were placed in a two pen brooder house and had access to outdoor runs where a small amount of green oats was available as green feed. Lot No. 1 was fed an all mash diet. Lot No. 2 was fed the same all mash diet with the addition of 0.1 percent thiouracil. The diets were fed ad lib in open hoppers and water was always available in enclosed founts. Table No. 1 gives the basal ration used in this test. Weekly body weights and feed consumption were recorded. At the conclusion of the 21-day feeding period the birds were slaughtered and their thyroid glands removed and weighed on an analytical balance. The carcasses were then wrapped in waxed paper and heavy manila paper 185
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
T
186
R. M. BLAKELY AND R. W. ANDERSON TABLE 1.—Basal ration
TABLE 2.—The effect of feeding 0.1 percent thiouracil on body weights, rate of gain and feed utilization, of 9 week old turkey broilers Lot No.
Mixed Sexes 1 2 Males 1 2 Females 1 2
Ration No.
No. Birds
Body Weight
Average Gain
Feed Consumption/Bird
Pounds Feed/Pound Gain
lbs.
lbs.
lbs.
lbs.
7 7B
25 25
4.04 3.27
2.24 1.51
5.74 4.53
2.56 3.00
7 7B
12 11
4.42 3.49
2.49 1.65
— —
— —
7 7B
13 14
3.68 3.09
2.01 1.38
— —
— —
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
weight data in Table No. 2 shows that the rate of gain was reduced for both males Percent Ingredient and females by the addition of 0.1 percent Ground Wheat 30 thiouracil to the diet. Final body weights 20 Ground Oats for Lot No. 1 (Controls) were 4.04 pounds 15 Ground Barley 18 Meat Meal (50% Protein) compared to 3.27 pounds for Lot No. 2 2 Fish Meal (Thiouracil), being a difference of .77 2 Milk Powder 10 Alfalfa Meal pounds. Weight gain data shows an in1 Ground Limestone crease of .73 pounds in favour of the con1 Steamed Bone Meal 1 Iodized Salt trol group. When males and females were considered separately the males from the 100 Total control group showed an average increase of .84 pounds and the females .63 pounds and quick frozen at — 20°F. They were over the thiouracil fed groups. When exthen held at 0°F. pending the removal of. pressed as percent of the controls the skin samples for fat analyses. At the end average gains for the thiouracil fed males of five months' storage the dressed carand females were 66.26 percent and 68.66 casses were thawed at room temperature. percent respectively. Duplicate skin samples, from one-half to Column No. 6 from Table No. 2 shows one centimeter wide, were removed from clearly that feed consumption per bird across the feather tract on each side of the was reduced in the thiouracil fed group. breast. In the case of one bird it was only possible to remove the left sample owing The reduction amounted to 1.21 pounds to a blemish on the right side. The skin per bird for the 21-day period. The last samples were weighed and placed in test column of this table compares the feedtubes and covered with concentrated HC1. gain ratios. It required 2.56 pounds of They were then submitted to Dr. A. R. G. feed to produce a pound of gain for the Emslie, Chemistry Division, Science Serv- control group and 3.00 pounds to produce ice, Ottawa, for fat analyses. The birds a pound of gain for the thiouracil fed were sexed at the time of removal of the group. Feed consumption data for the different sexes were not recorded. skin samples. Table No. 3 shows the percentage fat of RESULTS AND DISCUSSION the skin samples. The increase in the skin A study of the feed consumption and fat for the thiouracil fed birds (males and
187
INFLUENCE OF THIOURACIL ON TURKEY BROILERS
females combined) is rather remarkable being over 100 percent. It is of interest to note that while the females from the control group showed 1.0 percent more fat than the males that the picture is reversed in the case of the thiouracil fed birds. In this latter group the males showed 1.37 percent more fat than the females. The difference in the increase in fattening, therefore, is 2.37 percent in favor of the males. TABLE 3.—The effect on deposition of skin fat* by the addition of 0.1 per cent thiouracil to the diet of 9 week old turkey poults
Mixed Males Females Difference (M-F)
Lot No. 2 Lot No. 1 0 . 1 % Difference Control Thiouracil
%
%
10.64 10.12 11.12 -1.00
22.10 22.87 21.50 1.37
% 11.46 12.75 10.38 2.37
* Calculations are based on left skin samples in all cases.
Gutteridge's method of comparing the fat content of skin samples taken from the birds before and after feeding trials (Gutteridge, 1937) would have given a much better picture of the actual increase in fattening of males and females but unfortunately this was not possible in this test. Table No. 4 shows the effect on thyroid TABLE 4.-
Lot No.
Mixed Sexes 1 2 Males 1 2 Females 1 2
This experiment was designed to test
-The effect of thyroid weight of 9 week old turkey poults by the addition of 0.1 percent thiouracil to the basal diet
Ration No.
No. Birds
Mean Body Wt.
Ave. Thyroid Weight
Thyroid Wt./lOO gms. BW
gms.
mgs.
mgs.
Increase
7 7B
25 25
1892.5 1599.8
84.384 402.208
4.459 25.140
5.6 times
7 7B
12 11
2081.0 1696.0
94.600 397.400
4.545 23.431
5.1 times
7 7B
13 14
1718.5 1524.4
74.953 403.985
4.361 26.633
6.1 times
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
Sex
size of the addition of 0.1 percent thiouracil to the basal ration. Thyroid weights for thiouracil fed males showed an increase of 5.1 times the controls while the corresponding females showed an increase of 6.1 times the control females. This differs from the findings of Reineke (1947) who stated that the thyroid enlargement induced by the feeding of thiouracil was greatest in 24 week old turkey males. The thyroid weight per 100 grams of body weight for control group is shown as 4.459 milligrams. This is considerably lower than previous figures obtained in this laboratory which showed thyroid weights per 100 grams body weight of 6.72 milligrams and 7.76 milligrams for poults which were 42 days old and 50 days old respectively. The poults in this experiment were 63 days of age when slaughtered. The only explanation offered is that previous figures were obtained from poults which were maintained on a starting ration and were reared entirely in wire floored batteries where they were subjected to considerable artificial illumination, especially during the early weeks of the test. The present group were floor brooded from the 4th week and had access to oat greenfeed during the course of the test.
188
R. M. BLAKKLY AND R. W. ANDERSON
SUMMARY
Six week old turkey poults were fed a growing mash diet, to which was added 0.1 percent thiouracil, during a 21-day feeding trial. A depression in weight gains was recorded for both males and females. In the case of males it was .84 pounds and for females .63 pounds below the corresponding controls. Feed consumption in the thiouracil fed group was 1.21 pounds per bird less than
for the controls but efficiency of feed utilization was slightly lower. Percentage skin fat of the thiouracil fed birds averaged more than double that of the controls. In the case of males it was 2.25 times greater and in the case of females 1.92 times that of the corresponding controls. The feeding of 0.1 percent thiouracil caused increases in thyroid weights per 100 grams body weight, of 5.1 times and 6.1 times, for males and females respectively. ACKNOWLEDGMENTS
Our thanks are due to Dr. A. R. G. Emslie who made the fat analyses on the skin samples and The Lederle Laboratories who so generously supplied the thiouracil used in this test. REFERENCES
Andrews, F. N., and E. E. Schnetzler, 1946. Influence of thiouracil on growth and fattening in broilers. Poultry Sci. 25: 124-129. —• •, 1945. The effect of feeding thiouracil to hens upon the thyroid glands of chicks. Endocrinology 37: 382-384. Gutteridge, H. S., 1937. Methods and rations for fattening poultry. II. Sci. Agri. 18: 198-206. Kempster, H. L., and C. W. Turner, 1945. The effect of feeding thiouracil on the fleshing of New Hampshire broilers. Poultry Sci. 24: 94-96. Mixner, J. P., B. A. Tower, C. W. Upp, 1946. The effect of feeding thiouracil on body weight of New Hampshire cockerels. Poultry Sci. 25: 536-538. Reineke, E. P., J. A. Davidson, L. F. Woterink, and F. N. Barrett, 1946. The effect of thiouracil on fattening turkeys. Poultry Sci. 25:410 (Abstract).
Downloaded from http://ps.oxfordjournals.org/ by guest on April 15, 2015
the value of thiouracil for the possible improvement in fattening of turkey broilers. The results should be considered in that light. Final weights of the dressed carcasses were significantly lower but there is definite evidence of increased skin fat and consequent improvement in grade and appearance of the carcasses. Gutteridge (1937) has shown that the percentage skin fat has a high degree of correlation to body and abdominal fat in the chicken and it, therefore, can be assumed that the increased skin fat shown in this test indicates corresponding increase in abdominal and body fat. Table No. 2 shows an increase of 0.44 pounds in the pounds of grain required to produce a pound of gain in the thiouracil fed group. It shows also that this group consumed 1.21 pounds of feed less per bird during the 21 days of the test. A study of the economics of turkey broiler production will be necessary to evaluate properly the factors brought out in this test.