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Antibiotics and Nitrogen Utilization in Growing Cockerels
Antibiotics and Nitrogen Utilization in Growing Cockerels ROLLIN H. THAYER 1 AND V. G. HELLER Oklahoma Agricultural Experiment Station, Stillwater, Oklahoma (Received for publication April 12, 1954)
ANTIBIOTICS are reported to improve -**• the growth-promoting value of a chicken- or turkey-starter ration when the total protein level in the ration is below the level generally considered to be adequate for optimum growth (McGinnis, 1951; Bird el al, 1951; Machlin el al., 1952; and Biely el al., 1952). According to Baldini el al. (1953) Bobwhite quail grew as well on a ration containing 20 percent protein supplemented with aureomycin as they did on a 28 percent protein diet without aureomycin. Feed consumption and the efficiency of feed utilization, as obtained in these feeding tests, did not always point to a reduced protein requirement.
dent. Biely et al. (1952) were of the opinion that, since the additional growth obtained with aureomycin was the same regardless of protein level, the antibiotic effect was related to some factor other than protein level. Saxena et al. (1953) reported that the increase in chick weight due to penicillin additions was essentially the same at protein levels of 15, 18, and 21 percent. Growth studies by Slinger et al. (1952), Matterson et al. (1951), and Johnson (1951) did not support the view that the protein requirement of the growing chick was reduced by the feeding of antibiotics. In view of the contradictory results cited above, it was deemed desirable to obtain a more exact measure of the relative efficiency of protein utilization between antibiotic and non-antibiotic fed chicks. Nitrogen balance techniques were, therefore, used in this study in addition to obtaining information on growth response.
The increase in chick growth obtained by Machlin et al. (1952) was accompanied by an increase in efficiency of feed utilization. These workers concluded that the protein requirement of the growing chick was reduced by the addition of aureomycin to the feed. In the case of quail, Baldini et al. (1953) it was apparent that the feed and protein intake on a 20 percent protein diet was less than on a 24 percent diet, with an equal gain in weight on both diets. On the other hand, the data of Scott el al. (1952) showed that feed and protein intake increased when an increase in chick growth was obtained by the addition of aureomycin. Since efficiency of utilization of feed and protein were equal on all rations, no protein-sparing action was evi-
EXPERIMENTAL PROCEDURE
This study consisted of four feeding trials conducted in battery brooders. New Hampshire chicks of the Oklahoma A. and M. College strain of both sexes were used in all trials. These chicks were hatched from the Oklahoma A. and M. College breeder flocks. Each feeding trial consisted of four lots with approximately fifty day-old chicks in each lot. Two lots in each feeding trial were fed the basal diet, and two lots were fed the basal diet supplemented with 20 mg. per pound of either procaine penicillin G (trials 1, 2, 3) or aureomycin hydrochloride (trial 4). The length of the feeding period varied
1
From a thesis to be submitted by the senior author to the Graduate School, the State College of Washington, in partial fulfillment of the requirements for the Ph.D. degree.
97
98
R. H. THAYER AND V. G. HELLER TABLE 1.—Composition of basal rations Ration 2 4
Ration l 4 Ingredients Cerelose Soybean Meal (Protein 44%) Wheat Protein Hydrolysate Soybean Oil Mineral Mix1 Vitamin Mix2 DL-Methionine
Percent 41.26 45.00 1.00 2.SO 5.00 5.00 0.24 100.00
Ingredients
Percent
Ground Yellow Corn Pulverized Oats Soybean Meal (Protein 44%) Fish Meal (Protein 60%) Dried Yeast Dried Buttermilk Meat and Bone Scrap (Protein 50%) Alfalfa Meal (Protein 17%) Dicalcium Phosphate Salt Vitamin Mix3
54.0 5.0 22.5 5.0 3.0 2.0 3.0 2.0 1.0 0.5 2.0 100.0
1 Mineral Mix: Calcium Carbonate 29.24%, Dicalcium Phosphate 32.41%, Potassium Phosphate 15.65%, Salt 11.18%, Magnesium Sulfate 9.31%, Ferrous Sulfate 1.53%, Manganese Sulfate 0.58%, Potassium Iodide 0.061%, Copper Sulfate 0.028%, Zinc Chloride 0.019%, and Cobalt Chloride 0.0038%. 2 Vitamin Mix adds per pound of ration: Vitamin A 5,2001.U., Vitamin D 975 I.C.U., Choline 400 mg., Vitamin E 0.7 mg., Niacin 12.32 mg., Vitamin K 0.18 mg., Riboflavin 3.9 mg., Pantothenic Acid 4.0 mg., Thiamine 2.0 mg., Pyridoxine 2.0 mg., Folic Acid 0.2 mg., Biotin 0.04 mg., Vitamin Bi2 3 micrograms. 3 Vitamin Mix adds per pound of ration: Vitamin A 3,000 I.U., Vitamin D3 450 I.C.U., Riboflavin 3.6 mg., Niacin 10 mg., Choline 114 mg., Vitamin B !2 3 micrograms. 4 Crude Protein: Ration 1—21.49 percent, Ration 2—22.47 percent.
from 27 to 33 days in the various trials (Table 2). The composition of the two experimental rations which were fed is given in Table 1. Ration 1 composed principally of cerelose and soybean meal, was fed in trials 1 and 3. Ration 2, a practical type broiler mash, was fed in trials 2 and 4. Records were maintained for body weight and feed consumption. These data are presented in Table 2 for each of the treatments. Two days prior to the end of each feeding trial, 5 cockerels were selected at random from each treatment and placed in individual metabolism cages. A two-day adjustment period preceded the initiation of fecal collection. During the following four days, the daily feed intake of each cockerel was accurately measured. The daily excreta from each cockerel was collected separately in glass containers, moistened with ethyl alcohol to decrease bacterial growth. The birds were weighed at the beginning and end of the metabolism period.
The separate 24-hour excreta from each cockerel were analyzed for fecal and urinary nitrogen using the procedure of Eckman et al. (1949). Using these analytical data, values were calculated for the percent of absorbed nitrogen excreted in the urine, the percent of absorbed nitrogen retained in the chick's body, and the percent of dietary nitrogen excreted as apparent true protein nitrogen in the feces. RESULTS AND DISCUSSION
Average weight gain and feed conversion figures for each of the four feeding trials are given in Table 2. In trials 1, 2, and 4 the antibiotic fed chicks gained faster than did the controls. The differences obtained in trials 1 and 2 are statistically significant. A complete reversal of this trend with the controls gaining faster than the antibiotic fed chicks was observed in trial 3. Since the weight gains obtained in the metabolism cages in trial 3 were in favor of the antibiotic fed cockerels, the metabolism data were included in
99
ANTIBIOTICS AND N I T R O G E N UTILIZATION
TABLE 2.—Average weight gain and feed conversion in the four feeding trials Trial No.
No. chicks
Ration
50 1
Antibiotic supplement
Age at end of test period (days)
Average weight gain (gm.)
Feed/ gain
33
452 +
2.30
None Ration 1
50
Penicillin
7.83
1
489* + 3
Diff. 64 2
None
29
310 ±
Penicillin
None
45
327f±
73
1.48
69
320 ±
33
Diff.
17 + 6.29
Ration 1 46
1.57 4.45
Diff. 3
2.23
37 +11.08
Ration 2 66
Penicillin
42
None Ration 2
45
4 82
1.83 6.67
290 +
27
118
1.83
294f + Diff. - 2 6 + 9.44
4
Av. gain in metabolism cage (gm-)
Diff.
36
2.01
70
1.84
106
4.77
Aureomycin2
301 + Diff.
11 + 6.75
Diff.
36
* P = .05. f P = .01. 1 20 mg. per pound of diet, 2 20 mg. per pound of diet, 3 Antibiotic supplemented minus control.
the over-all summary. A similar situation existed in trial 2 where the difference in average weight gain between control and antibiotic fed chicks was highly significant statistically, but the five antibiotic fed cockerels selected for metabolism trials, failed to make better gains than did the controls during the metabolism period. None of the weight gain differences obtained during the metabolism period were statistically significant. The antibiotic fed chicks showed a more efficient feed conversion than did the controls in all trials, with the exception of trial 3. However, it is apparent that insofar as these four feeding trials are concerned, the net result of antibiotic feeding was to produce greater growth and more efficient feed conversion. The average percentage of dietary protein nitrogen which was excreted as apparent true protein nitrogen in the feces is
presented in Table 3 together with the statistical analysis of these data. This nitrogen represents the undigested nitrogen of the ration plus the undetermined portion of the metabolic nitrogen. In each of the individual trials the highest percentage of apparent true fecal nitrogen was found in the control lots which had received no antibiotic in the diet. As indicated in Table 3, the significance levels of these differences ranged from less than 50 to 97.5. However, the average difference obtained when the four trials were combined had a significance level of 99.9. These data indicate that penicillin and aureomycin under the conditions of these feeding trials brought about an increase in the amount of dietary nitrogen which was digested and absorbed from the digestive tract of the four-week-old cockerels. Even though this increase in absorbed nitrogen
100
R. H. THAYER AND V. G. HELLER TABLE 3.—The percent of dietary protein nitrogen excreted as apparent true protein nitrogen in the feces
Trial No. No. chicks
.. p Katlon
Antibiotic supplement
Screte 6 d (percent)
None Ration 1 Penicillin
14.17
Standard error
±
13.85
±
0.32
+
None
13.37
+
Penicillin
12.00
+
Diff.
1.37
+
15.16
±
Ration 2
None Penicillin
13.53
±
Diff.
1.63
±
15.54
+
None Aureomycin
2
Diff. All Trials
20
1 3
-1.47
2.10
12.10
14.64
10.73
13.27
0.78
-0.43
3.17
14.08
16.24
12.45
14.61
None
0.66
0.11
3.15
14.23
16.85
+
11.84
14.46
2.39
±
14.56
+
0.81
0.52
4.26
14.01
15.11
12.58
13.68
0.65
2.21
0.27 20
2
0.77
0.57 13.15
Antibiotic
13.13
±
Diff.
1.43
+
Level of significance
0.18
50
3.12
87
6.03
95
8.76
97.5
14.33
99.9
15.10
0.47
Ration 2 5
12.60
0.55
Ration 1
Computed F
12.92 to 15.42 0.54
1
Diff.3
5
95% confidence limits
0.38
20 mg. per pound of ration. 20 mg. per pound of ration. Control minus antibiotic supplemented.
was relatively small, it represents a decrease of 9.8 percent in the undigested nitrogen in the control diet or an increase of 1.67 percent in the digested nitrogen in the control diet. If the action of the antibiotic was responsible for increasing the supply of some amino acids which were limiting growth, this difference could be sufficient to account for the increase in growth response which was observed. The values for the percent of absorbed dietary nitrogen excreted as urinary nitrogen are listed in Table 4, and the values for the percent of absorbed dietary nitrogen retained in the chick's body are listed in Table 5. In addition, a summary of the statistical analyses of each set of data is given. In all trials, nitrogen reten-
tion was increased and apparent urinary nitrogen decreased in the cockerels which received antibiotics. These differences had a significance level above 95 only when the four trials were combined. It can be concluded that the antibiotics, penicillin and aureomycin, when fed as a part of the ration, increased the amount of nitrogen absorbed from the digestive tract of the growing cockerel. A possible explanation is that the rate of digestion may have in some way been increased. The antibiotics may have reduced the number or type of competitive intestinal bacteria which used amino acids as they were released in the digestion process. These data do indicate that the increased growth response due to the addi-
101
ANTIBIOTICS AND NITROGEN UTILIZATION TABLE 4.—The percent of absorbed dietary protein nitrogen excreted as urinary nitrogen
-
5 1
Antibiotic supplement None
Ration 1 Penicillin
5
5
None
5 3
1.84
45.73
+
Penicillin
43.71
±
Diff.
2.02
±
47.24
+
Penicillin
42.76
+
Diff.
4.48
+
43.22
+
None
5 4
None Ration 2
5
Aureomycin2 Diff.
All Trials
20 20
3
3.88
Ration 1 5
1
36.80
Ration 2 5
2
1.30
40.68 1
Diff.3 2
Standard
^H!£? « £ * 1+ 1+
„..
R a l
1+
Trial No. No. chicks
None
42.03
+
1.19
+
44.22
+
Antibiotic
41.32
+
Diff.
2.90
±
95% confidence limits
Computed F
Level of significance
4.46
92.5
0.64
50
2.41
80
0.17
50
5.08
96.5
37.68 to 43.68 33.80
39.80
-0.36
8.12
41.60
49.86
39.58
47.84
1.79 2.53
-3.81
7.85
42.54
51.94
38.06
47.46
-2.18
11.14
38.56
47.88
37.37
46.69
-5.41
7.79
42.37
46.07
39.47
43.17
0.29
5.51
2.04 2.89 2.02 2.86 0.91 1.28
20 mg. per pound of diet. 20 mg. per pound of diet. Control minus antibiotic supplemented.
tion of antibiotics to rations for chickens may be, at least in part, due to an increased efficiency in the digestion and absorption of dietary nitrogen. SUMMARY 1. A nitrogen balance study with fourweek-old New Hampshire cockerels to determine the effect of orally administered penicillin and aureomycin upon dietary nitrogen utilization is reported. The apparent true fecal nitrogen, the apparent urinary nitrogen, and the nitrogen retention were determined. 2. The antibiotics, penicillin and aureomycin, increased the amount of nitrogen absorbed from the intestinal tract of the four-week-old cockerels.
3. An increase in nitrogen retention and a decrease in urinary nitrogen excretion were observed in the antibiotic-fed cockerels. REFERENCES Baldini, J. T., R. E. Roberts and C. M. Kirkpatrick, 1953. Antibiotic and vitamin B ]2 supplements as related to the crude protein level of Bobwhite quail diets. Poultry Sci. 32:563-567. Biely, J., B. E. March and D. F. Smith, 1952. The effect of feeding antibiotics on the carbohydrate and protein requirements of the chick. Poultry Sci. 31:863-870. Bird, H. R., R. J. Lillie, L. J. Machlin and C. A. Denton, 1951. Antibiotics in poultry nutrition. Proc. 9th World's Poultry Congress, 2: 46-51. Ekman, P., H. Emanuelson and A. Fransson, 1949. Investigations concerning the digestibility of protein in poultry. Annals of the Royal Agricultural College of Sweden, 16: 751-777.
102
CALIFORNIA N O T E S
TABLE S.—The percent of absorbed dietary protein nitrogen retained in the chick's body Trial No. No. chicks S
Rati0
"
Ration 1
5
Nitrogen
Antibiotic s^ple-nt
g
None
59.34
Penicillin1
63.20
Diff.3 None
Standard
1.30
3.86
+
1.83
54.27
+
Penicillin
56.29
+
Diff.
2.02
±
52.76
+
None
57.24
±
diff.
4.48
±
2.89
56.78
+ ±
2.02
1.19
±
2.86
55.79
+
Aureomycin
2
57.97
Diff.
3
60.20
66.20
-0.36
8.08
50.14
58.40
52.16
60.42
-3.81
7.85
48.06
57.46
52.54
61.94
-2.18
11.14
52.12
61.44
53.31
62.63
-5.41
7.79
None
53.94
57.64
56.83
60.53
0.28
5.50
0.91 20
2
2.53
Penicillin
None
^
56.34 to 62.34
2.04
Ration 2
1
Computed
1.79
Ration 1
20
^ limits
+ ± +
Ration 2
All Trials
J
g
Antibiotic
58.68
+
Diff.
2.89
+
1.28
4.43
92.5
0.64
54
2.41
81
0.17
50
5.08
96.5
20 mg. per pound of diet. 20 mg. per pound of diet. Antiobiotic supplemented minus control.
Johnson, E. L., 1952. Providing vitamin Bi2, antibiotic and unknown growth factor activity for chick diets. Poultry Sci. 31: 955-961. Machlin, L. J., C. A. Denton, W. L. Kellog and H. R. Bird, 1952. Effect of dietary antibiotic upon feed efficiency and protein requirement of growing chickens. Poultry Sci. 31: 106-109. Matterson, L. D., E. P. Singsen, L. Decker and A. Zozeff, 1952. The influence of protein level, aureomycin and vitamin B12 on the growth and feed efficiency of chicks. Poultry Sci. 31:940-941. McGinnis, J. 1951. The effect of antibiotics on nutritional requirement of turkeys and chicks. Poultry
Sci. 30: 924. Saxena, H. C , M. E. Starr, L. G. Blaylock, J. S. Carver and J. McGinnis, 1953. Effect of dietary penicillin on the efficiency of protein utilization by chicks. Arch. Biochem. Biophysics, 44: 346350. Scott, H. M., E. A. Goffi and W. A. Glista, 1952. The protein requirement of the chick as influenced by aureomycin. Poultry Sci. 31: 751-752. Slinger, S. J., J. E. Bergey, W. F. Pepper, E. S. Snyder and D. Arthur, 1952. Effect of antibiotics on the protein requirement of broilers. Poultry Sci. 31:757-764.
CALIFORNIA NOTES The regents of the University of California have allocated $95,000 for the construction of a maximum
security laboratory for research on respiratory diseases at the School of Veterinary Medicine, Davis.
ANTIBIOTICS are reported to improve -**• the growth-promoting value of a chicken- or turkey-starter ration when the total protein level in the ration is below the level generally considered to be adequate for optimum growth (McGinnis, 1951; Bird el al, 1951; Machlin el al., 1952; and Biely el al., 1952). According to Baldini el al. (1953) Bobwhite quail grew as well on a ration containing 20 percent protein supplemented with aureomycin as they did on a 28 percent protein diet without aureomycin. Feed consumption and the efficiency of feed utilization, as obtained in these feeding tests, did not always point to a reduced protein requirement.
dent. Biely et al. (1952) were of the opinion that, since the additional growth obtained with aureomycin was the same regardless of protein level, the antibiotic effect was related to some factor other than protein level. Saxena et al. (1953) reported that the increase in chick weight due to penicillin additions was essentially the same at protein levels of 15, 18, and 21 percent. Growth studies by Slinger et al. (1952), Matterson et al. (1951), and Johnson (1951) did not support the view that the protein requirement of the growing chick was reduced by the feeding of antibiotics. In view of the contradictory results cited above, it was deemed desirable to obtain a more exact measure of the relative efficiency of protein utilization between antibiotic and non-antibiotic fed chicks. Nitrogen balance techniques were, therefore, used in this study in addition to obtaining information on growth response.
The increase in chick growth obtained by Machlin et al. (1952) was accompanied by an increase in efficiency of feed utilization. These workers concluded that the protein requirement of the growing chick was reduced by the addition of aureomycin to the feed. In the case of quail, Baldini et al. (1953) it was apparent that the feed and protein intake on a 20 percent protein diet was less than on a 24 percent diet, with an equal gain in weight on both diets. On the other hand, the data of Scott el al. (1952) showed that feed and protein intake increased when an increase in chick growth was obtained by the addition of aureomycin. Since efficiency of utilization of feed and protein were equal on all rations, no protein-sparing action was evi-
EXPERIMENTAL PROCEDURE
This study consisted of four feeding trials conducted in battery brooders. New Hampshire chicks of the Oklahoma A. and M. College strain of both sexes were used in all trials. These chicks were hatched from the Oklahoma A. and M. College breeder flocks. Each feeding trial consisted of four lots with approximately fifty day-old chicks in each lot. Two lots in each feeding trial were fed the basal diet, and two lots were fed the basal diet supplemented with 20 mg. per pound of either procaine penicillin G (trials 1, 2, 3) or aureomycin hydrochloride (trial 4). The length of the feeding period varied
1
From a thesis to be submitted by the senior author to the Graduate School, the State College of Washington, in partial fulfillment of the requirements for the Ph.D. degree.
97
98
R. H. THAYER AND V. G. HELLER TABLE 1.—Composition of basal rations Ration 2 4
Ration l 4 Ingredients Cerelose Soybean Meal (Protein 44%) Wheat Protein Hydrolysate Soybean Oil Mineral Mix1 Vitamin Mix2 DL-Methionine
Percent 41.26 45.00 1.00 2.SO 5.00 5.00 0.24 100.00
Ingredients
Percent
Ground Yellow Corn Pulverized Oats Soybean Meal (Protein 44%) Fish Meal (Protein 60%) Dried Yeast Dried Buttermilk Meat and Bone Scrap (Protein 50%) Alfalfa Meal (Protein 17%) Dicalcium Phosphate Salt Vitamin Mix3
54.0 5.0 22.5 5.0 3.0 2.0 3.0 2.0 1.0 0.5 2.0 100.0
1 Mineral Mix: Calcium Carbonate 29.24%, Dicalcium Phosphate 32.41%, Potassium Phosphate 15.65%, Salt 11.18%, Magnesium Sulfate 9.31%, Ferrous Sulfate 1.53%, Manganese Sulfate 0.58%, Potassium Iodide 0.061%, Copper Sulfate 0.028%, Zinc Chloride 0.019%, and Cobalt Chloride 0.0038%. 2 Vitamin Mix adds per pound of ration: Vitamin A 5,2001.U., Vitamin D 975 I.C.U., Choline 400 mg., Vitamin E 0.7 mg., Niacin 12.32 mg., Vitamin K 0.18 mg., Riboflavin 3.9 mg., Pantothenic Acid 4.0 mg., Thiamine 2.0 mg., Pyridoxine 2.0 mg., Folic Acid 0.2 mg., Biotin 0.04 mg., Vitamin Bi2 3 micrograms. 3 Vitamin Mix adds per pound of ration: Vitamin A 3,000 I.U., Vitamin D3 450 I.C.U., Riboflavin 3.6 mg., Niacin 10 mg., Choline 114 mg., Vitamin B !2 3 micrograms. 4 Crude Protein: Ration 1—21.49 percent, Ration 2—22.47 percent.
from 27 to 33 days in the various trials (Table 2). The composition of the two experimental rations which were fed is given in Table 1. Ration 1 composed principally of cerelose and soybean meal, was fed in trials 1 and 3. Ration 2, a practical type broiler mash, was fed in trials 2 and 4. Records were maintained for body weight and feed consumption. These data are presented in Table 2 for each of the treatments. Two days prior to the end of each feeding trial, 5 cockerels were selected at random from each treatment and placed in individual metabolism cages. A two-day adjustment period preceded the initiation of fecal collection. During the following four days, the daily feed intake of each cockerel was accurately measured. The daily excreta from each cockerel was collected separately in glass containers, moistened with ethyl alcohol to decrease bacterial growth. The birds were weighed at the beginning and end of the metabolism period.
The separate 24-hour excreta from each cockerel were analyzed for fecal and urinary nitrogen using the procedure of Eckman et al. (1949). Using these analytical data, values were calculated for the percent of absorbed nitrogen excreted in the urine, the percent of absorbed nitrogen retained in the chick's body, and the percent of dietary nitrogen excreted as apparent true protein nitrogen in the feces. RESULTS AND DISCUSSION
Average weight gain and feed conversion figures for each of the four feeding trials are given in Table 2. In trials 1, 2, and 4 the antibiotic fed chicks gained faster than did the controls. The differences obtained in trials 1 and 2 are statistically significant. A complete reversal of this trend with the controls gaining faster than the antibiotic fed chicks was observed in trial 3. Since the weight gains obtained in the metabolism cages in trial 3 were in favor of the antibiotic fed cockerels, the metabolism data were included in
99
ANTIBIOTICS AND N I T R O G E N UTILIZATION
TABLE 2.—Average weight gain and feed conversion in the four feeding trials Trial No.
No. chicks
Ration
50 1
Antibiotic supplement
Age at end of test period (days)
Average weight gain (gm.)
Feed/ gain
33
452 +
2.30
None Ration 1
50
Penicillin
7.83
1
489* + 3
Diff. 64 2
None
29
310 ±
Penicillin
None
45
327f±
73
1.48
69
320 ±
33
Diff.
17 + 6.29
Ration 1 46
1.57 4.45
Diff. 3
2.23
37 +11.08
Ration 2 66
Penicillin
42
None Ration 2
45
4 82
1.83 6.67
290 +
27
118
1.83
294f + Diff. - 2 6 + 9.44
4
Av. gain in metabolism cage (gm-)
Diff.
36
2.01
70
1.84
106
4.77
Aureomycin2
301 + Diff.
11 + 6.75
Diff.
36
* P = .05. f P = .01. 1 20 mg. per pound of diet, 2 20 mg. per pound of diet, 3 Antibiotic supplemented minus control.
the over-all summary. A similar situation existed in trial 2 where the difference in average weight gain between control and antibiotic fed chicks was highly significant statistically, but the five antibiotic fed cockerels selected for metabolism trials, failed to make better gains than did the controls during the metabolism period. None of the weight gain differences obtained during the metabolism period were statistically significant. The antibiotic fed chicks showed a more efficient feed conversion than did the controls in all trials, with the exception of trial 3. However, it is apparent that insofar as these four feeding trials are concerned, the net result of antibiotic feeding was to produce greater growth and more efficient feed conversion. The average percentage of dietary protein nitrogen which was excreted as apparent true protein nitrogen in the feces is
presented in Table 3 together with the statistical analysis of these data. This nitrogen represents the undigested nitrogen of the ration plus the undetermined portion of the metabolic nitrogen. In each of the individual trials the highest percentage of apparent true fecal nitrogen was found in the control lots which had received no antibiotic in the diet. As indicated in Table 3, the significance levels of these differences ranged from less than 50 to 97.5. However, the average difference obtained when the four trials were combined had a significance level of 99.9. These data indicate that penicillin and aureomycin under the conditions of these feeding trials brought about an increase in the amount of dietary nitrogen which was digested and absorbed from the digestive tract of the four-week-old cockerels. Even though this increase in absorbed nitrogen
100
R. H. THAYER AND V. G. HELLER TABLE 3.—The percent of dietary protein nitrogen excreted as apparent true protein nitrogen in the feces
Trial No. No. chicks
.. p Katlon
Antibiotic supplement
Screte 6 d (percent)
None Ration 1 Penicillin
14.17
Standard error
±
13.85
±
0.32
+
None
13.37
+
Penicillin
12.00
+
Diff.
1.37
+
15.16
±
Ration 2
None Penicillin
13.53
±
Diff.
1.63
±
15.54
+
None Aureomycin
2
Diff. All Trials
20
1 3
-1.47
2.10
12.10
14.64
10.73
13.27
0.78
-0.43
3.17
14.08
16.24
12.45
14.61
None
0.66
0.11
3.15
14.23
16.85
+
11.84
14.46
2.39
±
14.56
+
0.81
0.52
4.26
14.01
15.11
12.58
13.68
0.65
2.21
0.27 20
2
0.77
0.57 13.15
Antibiotic
13.13
±
Diff.
1.43
+
Level of significance
0.18
50
3.12
87
6.03
95
8.76
97.5
14.33
99.9
15.10
0.47
Ration 2 5
12.60
0.55
Ration 1
Computed F
12.92 to 15.42 0.54
1
Diff.3
5
95% confidence limits
0.38
20 mg. per pound of ration. 20 mg. per pound of ration. Control minus antibiotic supplemented.
was relatively small, it represents a decrease of 9.8 percent in the undigested nitrogen in the control diet or an increase of 1.67 percent in the digested nitrogen in the control diet. If the action of the antibiotic was responsible for increasing the supply of some amino acids which were limiting growth, this difference could be sufficient to account for the increase in growth response which was observed. The values for the percent of absorbed dietary nitrogen excreted as urinary nitrogen are listed in Table 4, and the values for the percent of absorbed dietary nitrogen retained in the chick's body are listed in Table 5. In addition, a summary of the statistical analyses of each set of data is given. In all trials, nitrogen reten-
tion was increased and apparent urinary nitrogen decreased in the cockerels which received antibiotics. These differences had a significance level above 95 only when the four trials were combined. It can be concluded that the antibiotics, penicillin and aureomycin, when fed as a part of the ration, increased the amount of nitrogen absorbed from the digestive tract of the growing cockerel. A possible explanation is that the rate of digestion may have in some way been increased. The antibiotics may have reduced the number or type of competitive intestinal bacteria which used amino acids as they were released in the digestion process. These data do indicate that the increased growth response due to the addi-
101
ANTIBIOTICS AND NITROGEN UTILIZATION TABLE 4.—The percent of absorbed dietary protein nitrogen excreted as urinary nitrogen
-
5 1
Antibiotic supplement None
Ration 1 Penicillin
5
5
None
5 3
1.84
45.73
+
Penicillin
43.71
±
Diff.
2.02
±
47.24
+
Penicillin
42.76
+
Diff.
4.48
+
43.22
+
None
5 4
None Ration 2
5
Aureomycin2 Diff.
All Trials
20 20
3
3.88
Ration 1 5
1
36.80
Ration 2 5
2
1.30
40.68 1
Diff.3 2
Standard
^H!£? « £ * 1+ 1+
„..
R a l
1+
Trial No. No. chicks
None
42.03
+
1.19
+
44.22
+
Antibiotic
41.32
+
Diff.
2.90
±
95% confidence limits
Computed F
Level of significance
4.46
92.5
0.64
50
2.41
80
0.17
50
5.08
96.5
37.68 to 43.68 33.80
39.80
-0.36
8.12
41.60
49.86
39.58
47.84
1.79 2.53
-3.81
7.85
42.54
51.94
38.06
47.46
-2.18
11.14
38.56
47.88
37.37
46.69
-5.41
7.79
42.37
46.07
39.47
43.17
0.29
5.51
2.04 2.89 2.02 2.86 0.91 1.28
20 mg. per pound of diet. 20 mg. per pound of diet. Control minus antibiotic supplemented.
tion of antibiotics to rations for chickens may be, at least in part, due to an increased efficiency in the digestion and absorption of dietary nitrogen. SUMMARY 1. A nitrogen balance study with fourweek-old New Hampshire cockerels to determine the effect of orally administered penicillin and aureomycin upon dietary nitrogen utilization is reported. The apparent true fecal nitrogen, the apparent urinary nitrogen, and the nitrogen retention were determined. 2. The antibiotics, penicillin and aureomycin, increased the amount of nitrogen absorbed from the intestinal tract of the four-week-old cockerels.
3. An increase in nitrogen retention and a decrease in urinary nitrogen excretion were observed in the antibiotic-fed cockerels. REFERENCES Baldini, J. T., R. E. Roberts and C. M. Kirkpatrick, 1953. Antibiotic and vitamin B ]2 supplements as related to the crude protein level of Bobwhite quail diets. Poultry Sci. 32:563-567. Biely, J., B. E. March and D. F. Smith, 1952. The effect of feeding antibiotics on the carbohydrate and protein requirements of the chick. Poultry Sci. 31:863-870. Bird, H. R., R. J. Lillie, L. J. Machlin and C. A. Denton, 1951. Antibiotics in poultry nutrition. Proc. 9th World's Poultry Congress, 2: 46-51. Ekman, P., H. Emanuelson and A. Fransson, 1949. Investigations concerning the digestibility of protein in poultry. Annals of the Royal Agricultural College of Sweden, 16: 751-777.
102
CALIFORNIA N O T E S
TABLE S.—The percent of absorbed dietary protein nitrogen retained in the chick's body Trial No. No. chicks S
Rati0
"
Ration 1
5
Nitrogen
Antibiotic s^ple-nt
g
None
59.34
Penicillin1
63.20
Diff.3 None
Standard
1.30
3.86
+
1.83
54.27
+
Penicillin
56.29
+
Diff.
2.02
±
52.76
+
None
57.24
±
diff.
4.48
±
2.89
56.78
+ ±
2.02
1.19
±
2.86
55.79
+
Aureomycin
2
57.97
Diff.
3
60.20
66.20
-0.36
8.08
50.14
58.40
52.16
60.42
-3.81
7.85
48.06
57.46
52.54
61.94
-2.18
11.14
52.12
61.44
53.31
62.63
-5.41
7.79
None
53.94
57.64
56.83
60.53
0.28
5.50
0.91 20
2
2.53
Penicillin
None
^
56.34 to 62.34
2.04
Ration 2
1
Computed
1.79
Ration 1
20
^ limits
+ ± +
Ration 2
All Trials
J
g
Antibiotic
58.68
+
Diff.
2.89
+
1.28
4.43
92.5
0.64
54
2.41
81
0.17
50
5.08
96.5
20 mg. per pound of diet. 20 mg. per pound of diet. Antiobiotic supplemented minus control.
Johnson, E. L., 1952. Providing vitamin Bi2, antibiotic and unknown growth factor activity for chick diets. Poultry Sci. 31: 955-961. Machlin, L. J., C. A. Denton, W. L. Kellog and H. R. Bird, 1952. Effect of dietary antibiotic upon feed efficiency and protein requirement of growing chickens. Poultry Sci. 31: 106-109. Matterson, L. D., E. P. Singsen, L. Decker and A. Zozeff, 1952. The influence of protein level, aureomycin and vitamin B12 on the growth and feed efficiency of chicks. Poultry Sci. 31:940-941. McGinnis, J. 1951. The effect of antibiotics on nutritional requirement of turkeys and chicks. Poultry
Sci. 30: 924. Saxena, H. C , M. E. Starr, L. G. Blaylock, J. S. Carver and J. McGinnis, 1953. Effect of dietary penicillin on the efficiency of protein utilization by chicks. Arch. Biochem. Biophysics, 44: 346350. Scott, H. M., E. A. Goffi and W. A. Glista, 1952. The protein requirement of the chick as influenced by aureomycin. Poultry Sci. 31: 751-752. Slinger, S. J., J. E. Bergey, W. F. Pepper, E. S. Snyder and D. Arthur, 1952. Effect of antibiotics on the protein requirement of broilers. Poultry Sci. 31:757-764.
CALIFORNIA NOTES The regents of the University of California have allocated $95,000 for the construction of a maximum
security laboratory for research on respiratory diseases at the School of Veterinary Medicine, Davis.