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Fat Studies in Poultry
Fat Studies in Poultry 2. FAT SUPPLEMENTS IN CHICK AND POULT RATIONS J. BIELY AND B. MARCH Poultry Nutrition Laboratory, The University of British Columbia, Vancouver, B.C., Canada (Received for publication March 1, 1954)
T
In the investigation here described, experiments have been carried out to de-
termine the effect of adding fat to diets containing various levels of protein. Two experiments were conducted with chicks and two with turkey poults. EXPERIMENTAL
Experiment 1. Day-old New Hampshire chicks were fed diets of different caloric contents. The control diet was formulated according to Table 1 to contain 23 percent protein. Diets 2, 3 and 4 contained 7 percent of ground cellulose, tallow, and cornstarch respectively. These supplements were added to the control ration without adjustment in the levels of the other ingredients in the diet. That is, 93 lbs. of the control diet were equivalent TABLE 1.—Composition of rations in Experiment 1 1. Control ration Ingredient ground wheat ground corn soybean oil meal fishmeal dried brewers' yeast livermeal limestone bonemeal iodized salt feeding oil manganese sulphate choline chloride (25%) antibiotic supplement* riboflavin nicotinic acid
lbs. 28.41 28.41 18.0 9.0 2.0 3.0 1.0 1.75 0.5 0.25 0.025 0.4 0.25 0.1 gm. 0.9 gm. 93.01b.
2. 3. 4. 5.
93 93 93 93
lb. control lb. control lb. control lb. control cornstarch.
ration ration ration ration
plus plus plus plus
7 lb. 7 lb. 7 lb. 7 lb.
cellulose tallow. cornstarch. tallow plus 7 lb.
* "Aurofac A" containing 1.8 gm. aureomycin per pound.
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HE amount of research which has been conducted on fats and oils in poultry rations is comparatively small. This lack of interest in fats has been due to the fact that, first, a specific requirement for fat has not been clearly established with the chick or the adult bird; and secondly, the ingredients commonly used in poultry rations are presumed to supply sufficient fat to meet the ordinary needs of poultry. The demands of the rapidly growing chick for many of the vitamins and for protein have been found to be much greater than was first supposed. Conceivably, the energy requirement of the growing chick may likewise be higher than the caloric level provided by modern rations. This concept of high energy rations is already widely employed in broiler rations since the development of the "Connecticut ration" by Scott, Matterson and Singsen (1947). With regard to the use of fat as an energy source in poultry rations, Henderson and Irwin (1940) reported that up to 10 percent of soybean oil could be fed to chicks without affecting the rate of growth to 8 weeks of age. Similarly Siedler and Schweigert (1953) observed that growth and feed efficiency of chicks fed 2 and 8 percent of supplementary fat was equal to that of those fed a similar diet without the supplementary fat. Pepper, Slinger and Snyder (1953) showed that wheat-soya broiler diets were improved when supplemented with 2 percent of soybean oil.
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FAT SUPPLEMENTS IN CHICK AND POULT RATIONS TABLE 2.—Average weights of chicks in Experiment 1 at 6 weeks of age and efficiency of feed utilization
Cockerels Ration
#1 (control) #2 (7 lb. cellulose) #3 (7 lb. tallow) #4 (7 lb. cornstarch) #5 (7 lb. tallow+7 lb. cornstarch)
ms
Wt. ^ ->
Pullets
Feed
Gain
654 639 680 642
2.27 2.33 1.98 2.15
702 679 698 687
2.21 2.22 1.90 2.06
0.51 0.47 0.41 0.44
651
2.11
682
2.02
0.40
750 719 715 732
2.15 2.10 1.82 1.98
714
1.93
Protein level of diet Ingredient 24%
100
lb. 100
28% 7.5 lb. 23.9 23.9 24.0 12.0 2.0 3.0 1.0 1.5 0.5 0.25 0.4 0.025 0 . 1 gm. 0 . 9 gm.
lb. 100
lb.
Lbs. gain
The composition of the basal diets is given in Table 3. Each of these three basal diets was in turn fed at three energy levels. The energy level was adjusted by replacing part or all of the cornstarch in the basal rations with tallow. The energy level of the diets was adjusted, therefore, without altering the amounts of the protein concentrates and cereals in the diets. The average weights of the chicks and the efficiency of feed utilization are given in Tables 4 and 5. Experiment 3. Growing turkeys utilize feed more efficiently than do chicks. To maintain a high degree of efficiency with the high-protein diets commonly fed, it was felt that there might be some advantage in increasing the available energy content of turkey broiler rations, particularly towards the end of the feeding period. In the following experiments edible tallow was used to raise the level of available energy beyond that attainable by the use of ingredients generally included in turkey broiler rations. Two experiments using turkeys as test animal have been carried out. Like the foregoing experiments with chicks, these tests were designed to compare the effect of different fat levels with rations containing different levels of protein. The levels of protein and fat in some of the diets have been varied every two weeks throughout the experiments. Other ra-
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TABLE 3.—Composition of basal diets in Experiment 2
7.5 lb. 7.5 lb. 34.2 28.3 34.2 28.3 10.0 18.0 5.0 9.0 2.0 2.0 3.0 3.0 1.0 1.0 2.0 1.75 0.5 0.5 0.25 0.25 0.4 0.4 0.025 0.025 0 . 1 gm 0 . 1 gm 0.9 gm 0.9 gm
Feed
Gain
Gain
to 100 lbs. of the supplemented diets with respect to all of the nutrients except the cellulose, tallow and cornstarch used in adjusting the energy content of the diets. In ration 5, 7 lbs. each of cornstarch and tallow were added to 93 lbs. of the control diet. In this ration, therefore, 107 lbs. were required to supply the nutrients provided by 93 lbs. of the control ration. The rations were fed ad lib. to day-old New Hampshire chicks. Each ration was fed to a lot of pullets and to a lot of cockerels. Growth rate and feed consumption were recorded every two weeks until 6 weeks of age. These data are summarized in Table 2. Experiment 2. Day-old New Hampshire chicks were fed diets containing 19, 24 and 28 percent of protein respectively.
cornstarch ground wheat ground yellow corn soybean oil meal fishmeal dried brewers' yeast livermeal limestone bonemeal iodized salt feeding oil (2.250A-300D) choline chloride (25%) manganese sulphate riboflavin nicotinic acid
Lbs. protein
Wt. tems->
Wt. tems")
19%
Feed
Average
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J. BIELY AND B. MARCH
TABLE 4.—Average weekly weights (grams) of chicks (Lots A and B) in Experiment 2
Description of Diet
Without antibiotic
With antibiotic
Weeks oi age
Weeks ol age 2
3
4
5
6
7
82
155
252
350
497
636
764
786 80 7 1 -2
156
259
387
535
686
817
1
3
11
8
8
7
84
164
266
394
538
680
804
84
168
272
405
563
722
851
0
2
2
3
5
6
6
2
3
4
5
6
7
19% protein
76
140
223
334
463
600
732
24% protein % gain over 19% diet
77 1
150 7
242 9
364 9
508 10
652 9
782 7
28% protein % gain over 19% diet % gain over 24% diet
80 5 4
154 10 3
250 12 3
370 11 2
515 652 9 11 0 1
19% protein, 5% tallow 24% protein, 5% tallow % gain over 19% diet
74 80 8
140 152 9
220 254 15
324 372 15
435 510 17
562 648 15
680 760 12
28% protein, 5 % tallow 78 % gain over 19% diet 5 % gain over 24% diet - 2
158 13 4
258 17 2
383 18 3
530 22 4
690 23 6
818 20 8
19% protein, 7.5% tallow
74
136
222
326
438
572
692
24% protein, 7.5% tallow % gain over 19% diet
81 9
160 18
262 18
389 19
536 22
678 19
817 18
83
164
264
392
528
656
796
28% protein, 7.5% tallow % gain over 19% diet % gain over 24% diet
79 7 0
156 15 -2
253 14 -3
377 16 -3
519 18 -3
633 11 -7
804 16 -2
86
170
276
408
562
713
850
4
4
5
4
6
9
7
tions were formulated in which the protein level was kept constant and the fat content was increased. In still other diets the protein level was gradually lowered TABLE 5.—Average weights of chicks in Experiment 2
at 7 weeks of age and efficiency of feed utilization Protein content of diet
Average w eights of chicks (gms.)
Feed
Lot A
Lot Avera age
Gain
Supplement to diet
19%
none 5 % tallow 7.5% tallow
736 686 694
728 675 690
732 680 692
2.39 2.43 2.47
24%
none aureomycin* 5 % tallow 5 % tallow plus aureomycin 7.5% tallow 7.5% tallow plus aureomycin
809 758 760
756 771 760
782 764 760
2.32 2.32 2.19
80.5 835
803 799
804 817
2.20 2.14
782
811
796
2.14
770 820 818
802 814 819
786 817 818
2.28 2.24 2.14
832 796
870 811
851 804
2.03 2.12
850
851
850
2.04
28%
none aureomycm 5 % tallow 5 % tallow plus aureomycin 7.5% tallow 7.5% tallow plus aureomycin
* 4.5 mg. aureomycin per pound from "Aurofac A.'
while the fat content was raised. The dietary regimens were as follows: 1. 28 percent protein 0-10 weeks. 2. 32, 29, 26, 23 and 20 percent protein with adjustments at 2, 4, 6 and 8 weeks. 3. 32, 29, 26, 23 and 20 percent protein with 0, 2, 4, 6 and 8 percent tallow, with adjustments at 2, 4, 6 and 8 weeks. 4. 32 percent protein 0-10 weeks. 0, 2, 4, 6 and 8 percent tallow with adjustments at 2,4, 6 and 8 weeks.
The composition of the 28 percent protein diet used in the experiment is shown in Table 6. In the other rations the supplements were maintained at the levels indicated in Table 6 but the protein concentrates and the cereals were varied to adjust the protein content of the rations to the desired levels. To prevent the development of rancidity in the rations containing added fat, the antioxidants propyl gallate and citric acid were added to the tallow. In the
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1
1
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS TABLE 6.—Composition of 28% protein diet in Experiments 3 and 4 Ingredient
25. SS 25.55 15.0 10.0 10.0 3.0 5.0 2.0 0.5 0.5 1.5 1.0 0.25 0.025 0.01 0.01 2.0 gm. 0.15gm. 0.45 gm. 400,000 units 60,000 units 0.0125 lb.
* "Aurofac A" containing 1.8 gm. aureomycin per lb.
rations without tallow, the antioxidants were added directly to the feed. Each dietary regimen was tested with lots of 23 male and 20 female day-old Beltsville Small White poults. Feed and water were kept before the birds at all times. The average weights of the birds and the efficiency of feed utilization are shown in Table 7.
The average weights of the turkeys at 10 weeks of age and the efficiency with which the birds utilized the experimental diets are given in Table 8. RESULTS AND DISCUSSION
The data obtained in these four experiments point to very similar conclusions regarding the use of supplementary fat
TABLE 7.—Average weights and efficiency of feed utilization of turkey poulls to 10 weeks of age in Experiment 3
Dietary Regimen
Males 2 8 % protein 32—20% protein 32—20% protein with tallow 3 2 % protein with tallow Females 2 8 % protein 32—20% protein 32—20% protein with tallow 3 2 % protein with tallow
2 wks.
4 wks.
6 wks.
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 28% diet
8 wks.
10 wks.
0-6 wks.
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 28% diet 2,547
Feed Gain
Feed Gain 0-10 wks.
1.94
1,716
' 191
-10
542
-6
1,004
-4
2.12
1,653
-4
2,399
-6
191
-10
548
-5
1,022
-2
1.89
1,700
-1
2,473
-3
2.24
191
-10
527
-9
993
-5
1.94
1,661
-3
2,435
-4
2.32
212
576
158
1,043
2.34
2.08
1,284
163
3
428
-2
786
-2
2.11
1,300
1
1,836
-1
167
6
455
4
827
3
1.99
1,353
5
1,917
3
2.32
169
7
447
2
817
2
2.01
1,322
3
1,866
0
2.46
437
800
1,858
2.50
2.49 2.38
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Experiment 4. A second experiment with turkeys sought to ascertain the effect of feeding different levels of protein and energy to turkeys to 10 weeks of age. Broad Breasted Bronze males and females were reared separately in battery brooders. In the light of results obtained in the previous experiment, the control protein level was fixed at 28 percent, i.e., the protein level was 28 percent in the basal diet and the rations were maintained at constant protein level throughout the experiment. The composition of this diet was similar to that given in Table 6. The vitamin and mineral supplements were maintained at the levels indicated in Table 6. Only the protein supplements and the cereals were adjusted. The dietary regimens were the same as those in the previous test except that the successive levels of protein fed were 28, 26, 24, 22 and 20 percent.
lbs./cwt.
ground yellow corn ground wheat soybean oil meal fishmeal meatrheal livermeal dried brewers' yeast dehydrated cereal grass iodized salt choline chloride (25%) bonemeal limestone antibiotic supplement* manganese sulphate propyl gallate citric acid nicotinic acid riboflavin calcium pantothenate vitamin A vitamin D3 sulfaquinoxaline
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J. BIELY AND B. MARCH TABLE 8.—Average weights and efficiency of feed utilization of turkey poults to 10 weeks of age in Experiment 4 2 wks.
Dietary Regimen
Males 28% protein 28—20% protein 28% protein with tallow 28—20% protein with tallow Females 28% protein
208
Wt. (gms.)
541
210
1
562
214
3
216
4
193
8 wks.
6 wks.
% incr. over 28% diet
% incr. over Wt. 28% (gms.) diet
2,722
Gain
-6
2.40
2,903
0-10 wks. 2.22
2,005
1,318
3
2,199
4
3,130
8
2.21
1,206
-5
2,018
-5
2,812
-3
2.30
578
7
565
4
1,692
1,072
4
498
4
1,019
-5
1,607
193
0
487
2
1,039,
-3
1,750
462
-3
971
-10
1,616
-2
-6
Feed
% incr. ovet 28% diet
-4
1,225
200
189
Wt. (gms.)
2,122
1,276 4
478
Wt. (gms.)
10 wks.
% incr. over 28% diet
in chick and poult rations. The greatest benefit from the addition of fat to the rations appeared in the efficiency with which rations containing supplementary fat were utilized. In experiment 1, for example, utilization of feed was affected to a greater extent than was the rate of growth of the chicks when the rations fed were "diluted." The rate of growth in the cockerels was reduced when cellulose, tallow or cornstarch was added to the basal diet. The growth rate of the pullets remained much the same on the various rations although tallow supplementation of the basal ration resulted in a faster rate of growth than was obtained with the basal ration. With the rations "diluted" with ground cellulose, the efficiency of feed utilization was the same as with the control ration. This means that the available nutrients were more efficiently utilized in the ration with additional bulk than in the control ration. Calculated on the basis of the protein consumed, the efficiency of protein utilization for the ration containing 7 percent cellulose was 0.47 as compared to a value of 0.51 for the basal ration. The extra bulk in the ration containing cellulose may have retarded the passage of
2,359 -5 3 -5
.2.26 2.38
2,223
-6
2,495
6
2.11
2,268
-4
2.39
feed through the digestive tract and permitted more complete utilization of the nutrients. Since the fibre from the added cellulose is not bound up with the other nutrients it probably does not interfere with digestion in the same way as it usually does in natural feedstuffs of high fibre content. The addition of tallow to the control ration improved the efficiency of feed utilization from 2.21 to 1.90. This difference represents a considerable saving in the other ingredients in the ration. Whereas the chicks in the control lot consumed 0.51 lb. of protein per lb. of gain, those in the two lots fed tallow consumed only 0.41 and 0.40 lb. of protein per lb. of gain. The addition of starch to the.control ration improved the efficiency of feed utilization to 2.06. This value does not represent so great a degree of efficiency as was attained by the addition of oil to the ration. Nevertheless it does indicate that the protein in the control ration was being "wasted" to some extent as an energy source. The efficiency of utilization of the rations containing both tallow and cornstarch was similar to that of the ration supplemented with cornstarch alone, in
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28—20% protein 28% protein with tallow 28—20% protein with tallow
Wt. (gms.)
4 wks.
% incr. over 28% diet
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS
The effect of tallow in depressing the rate of growth with the 19 percent protein diet but increasing it with higher levels of protein would indicate an interrelationship between protein and fat utilization in the chick. Studies with rats by Barnes, Primrose and Burr (1944) showed a low protein intake to be associated with low fat digestibility. Forbes et al. (1946a, b) also working with rats presented data to demonstrate that the energy utilization of the diet as a whole is improved when liberal amounts of fat
are supplied. With the rations not supplemented with tallow it will be seen (Table 4) that the chicks receiving 24 and 28 percent protein grew more rapidly than those receiving only 19 percent protein. The increased rate of growth was apparent during the first 2 weeks and did not vary appreciably percentage-wise from the rate of growth of chicks fed the control diet through to 7 weeks. Rates of growth did not vary between chicks fed the 24 percent and those fed the 28 percent ration. This is in accord with the results obtained by Almquist and Asmundson (1944) upon feeding White Leghorn cockerels mashes containing 30 and 20 percent of protein respectively. It was found that although the birds started on the high protein diet grew more quickly during the first week and maintained their advantage in weight to 8 weeks, there was no consistent variation in the percentage rate of increase. With the addition of 5 percent of oil to the rations the advantage with respect to rate of growth of the higher protein diets became more pronounced. Furthermore, it will be seen from Table 4 that percentage gain in growth between the 19 and the 24 and 28 percent protein rations increased as the birds became older. In the case of the rations without tallow, no difference appeared in the rates of growth of chicks fed 24 or 28 percent protein. When the rations were supplemented with 5 percent tallow, however, the chicks fed 28 percent protein grew faster from 4 to 8 weeks than those on 24 percent protein. When 7.5 percent of tallow was added to the rations, the chicks fed 24 and 28 percent protein again grew faster than those fed 19 percent protein. It has already been reported by Biely, March and Smith (1952) that a greater response can be expected to aureomycin
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spite of the fact that this ration was diluted to 107 lbs. The protein efficiency was indicative again that the energy content of the basal ration was suboptimal and that protein was being "wasted" as an energy source. In experiment 2 the protein levels of 19, 24 and 28 percent were chosen in order to determine if protein level had any effect on the response or tolerance of the growing chick for fat, and, conversely, if the fat level in the diet had any effect on the protein requirement of the chick for maximum growth rate. It will be seen (Table 5) that growth in the birds fed the 19 percent protein diets was depressed 52 and 40 grams respectively by the addition of 5.0 or 7.5 percent of tallow to the diet. When fat was added to the 19 percent diet the efficiency of feed utilization was lowered. The addition of fat to the diet containing 24 percent protein had no significant effect on growth. Feed efficiency, however, was improved with 5.0 and 7.5 percent fat by 5 and 8 percent respectively. Similarly at the 28 percent level of protein the increased rate of growth obtained by supplementing the basal diet with 5.0 or 7.5 percent of fat was not statistically significant. As with the 24 percent protein diet, however, efficiency was increased when fat was added to the 28 percent protein diet.
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J. BIELY AND B. MARCH
one in which the protein level was reduced from 32 to 20 percent with the addition of 0 to 8 percent of tallow resulted in the most efficient utilization of feed. Lloyd, Reed and Fritz (1949) reported similar results on the feeding of high protein diets to turkeys. These investigators obtained the best growth to 7 or 8 weeks when the diet contained approximately 28 percent protein. They reported that while diets at the 32 percent protein level gave more rapid growth during the first two weeks, maintenance of this high level of protein beyond this period was found to be undesirable. In the second experiment using turkey poults the range of protein used was from 20 to 28 percent in view of the lack of response to higher levels in the previous experiment. In this experiment the poults (both males and females) fed 28 percent protein from 0 to 10 weeks grew faster than the poults receiving graded levels of protein. The addition of tallow to the rations fed under either regimen increased the weight of the poults at 10 weeks of age. It will be seen from the average weekly weights in Table 8 that the reduction of the protein level depressed the rate of growth at six weeks. When tallow was added to the 28 percent protein ration an increase in the rate of growth was observed in the males at 4 weeks and in the females at 8 weeks. The effect of supplementary tallow on the growth of the poults fed the rations in which the level of protein was lowered was not so striking as when the protein level was maintained at 28 percent. Nevertheless, by the time the poults were 10 weeks of age there was a slight difference in the average weights in favor of the rations supplemented with tallow. Feed utilization was most efficient with the ration maintained at 28 percent protein and supplemented with tallow. Low-
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at high protein levels than at low. Aureomycin was not added, therefore, to the rations at the 19 percent protein level in the present experiment. In the case of the 24 percent protein diets there was a response to aureomycin only with the ration supplemented with 5 percent of tallow. At the 28 percent protein level, however, there was a response to aureomycin with each of the different diets. When the 24 and the 28 percent protein rations were supplemented with aureomycin the 28 percent rations gave consistently better weights at 7 weeks of age than the 24 percent rations. It will be noted in addition that the percentage difference between the 24 and the 28 percent protein rations in the rate of growth was greatest from 4 to 8 weeks. This is at variance with the data of Almquist and Asmundson mentioned above. The experiments conducted with turkeys indicated that tallow could be added to poult rations without any adverse effect on growth. Under certain conditions it may be advantageous to add tallow for the effects on both growth rate and efficiency of feed utilization. In no instance where tallow was added to the rations did symptoms of hock disorder appear, as has been reported by Scott (1953) when cod liver oil was added to poult rations. In the first experiment using poults there appeared to be no advantage in starting poults at a protein level higher than 28 percent. Supplementation of the rations with increasing levels of tallow at the same time as the protein level was decreased resulted in a faster rate of growth and an improvement in feed efficiency as compared with growth rate and feed efficiency on the rations in which the protein was decreased without increasing the fat level. Of the four dietary regimens tested, the
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS
ering the protein level in the rations from 28 to 20 percent lowered the feed efficiency as well as the rate of growth. The addition of tallow to the rations with the lower protein content raised the feed efficiency negligibly. Since the preparation of this paper, Sunde (1954) has reported that feed utilization was improved when up to 5 percent of fat was fed to either chicks or turkey poults.
Four experiments have been carried out to study the relationship between optimum protein and fat levels in chick and poult rations. With chicks it was found that the addition of fat to a 19 percent protein diet depressed growth and feed efficiency. When fat was added to a 24 percent or a 28 percent protein diet, growth was unaffected or stimulated and feed efficiency was improved. Supplementation with tallow increased the level of protein which might be considered to give maximum growth to 7 or 8 weeks. Fastest growth obtained to 7 weeks of age was with a 28 percent protein diet containing 5.0 or 7.5 percent of tallow and supplemented with aureomycin. With Beltsville Small White poults, the rate of growth to 10 weeks of age was faster with a ration maintained at 28 percent than with one starting at 32 percent and gradually reduced to 20 percent. With Broad Breasted Bronze poults, growth was faster when the ration was maintained at 28 percent protein than when it was gradually reduced to 20 percent. This was the case whether or not the rations were supplemented with tallow. The addition of tallow to the rations increased the rate of growth, particularly
in the ration maintained at 28 percent protein. In both chick and poult rations the addition of fat may be advantageous when relatively high levels of protein are fed. In rations in which the energy content is raised by the addition of fat, the level of protein which may be utilized efficiently is higher than in rations of lower energy content. REFERENCES Almquist, H. J., and V. S. Asmundson, 1944. High protein mashes for broilers. Poultry Sci. 23: 6771. Barnes, R. H., M. F. Primrose and G. O. Burr, 1944. The influence of the protein content of the diet upon fat digestibility. J. Nutrition, 27: 179-184. Biely, J., B. E. March and D. F. Smith, 1952. Effect of feeding antibiotics on the carbohydrate and protein requirements of the chick. Poultry Sci. 31:863-870. Forbes, E. B., R. W. Swift, R. F. Elliott and W. H. James, 1946a. Relation of fat to economy of food utilization (I) by the growing albino rat. J. Nutrition, 31: 203-212. Forbes, E. B., R. W. Swift, R. F. Elliott and W. H. James, 1946b. Relation of fat to economy of food utilization (II) by the mature albino rat. J. Nutrition, 31: 213-227. Henderson, E. W., and W. E. Irwin, 1940. The tolerance of growing chicks for soybean oil in their ration. Poultry Sci. 19: 389-395. Lloyd, M. D., C. A. Reed and J. C. Fritz, 1949. Experiences with high protein diets for chicks and poults. Poultry Sci. 28: 69-74 Pepper, W. F., S. J. Slinger and E. S. Snyder, 1953. Value of low levels of soybean oil in broiler diets containing a high percentage of wheat. Poultry Sci. 32: 1084-1085. Scott, H. M., L. D. Matterson and E. P. Singsen, 1947. Nutrition factors influencing growth and efficiency of feed utilization. I. The effect of the source of carbohydrate. Poultry Sci. 26:554. Scott, M. L., 1953. Prevention of the enlarged hock disorder in turkeys with niacin and vitamin E. Poultry Sci. 32:670-677. Siedler, A. J., and B. S. Schweigert, 1953. Effect of feeding graded levels of fat with and without choline and antibiotic+Bi 2 supplements to chicks. Poultry Sci. 32: 449-.454. Sunde, M. L., 1954. The use of animal fats in poultry feeds. J. Amer. Oil Chem. Soc. 31: 49-52.
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SUMMARY
1227
T
In the investigation here described, experiments have been carried out to de-
termine the effect of adding fat to diets containing various levels of protein. Two experiments were conducted with chicks and two with turkey poults. EXPERIMENTAL
Experiment 1. Day-old New Hampshire chicks were fed diets of different caloric contents. The control diet was formulated according to Table 1 to contain 23 percent protein. Diets 2, 3 and 4 contained 7 percent of ground cellulose, tallow, and cornstarch respectively. These supplements were added to the control ration without adjustment in the levels of the other ingredients in the diet. That is, 93 lbs. of the control diet were equivalent TABLE 1.—Composition of rations in Experiment 1 1. Control ration Ingredient ground wheat ground corn soybean oil meal fishmeal dried brewers' yeast livermeal limestone bonemeal iodized salt feeding oil manganese sulphate choline chloride (25%) antibiotic supplement* riboflavin nicotinic acid
lbs. 28.41 28.41 18.0 9.0 2.0 3.0 1.0 1.75 0.5 0.25 0.025 0.4 0.25 0.1 gm. 0.9 gm. 93.01b.
2. 3. 4. 5.
93 93 93 93
lb. control lb. control lb. control lb. control cornstarch.
ration ration ration ration
plus plus plus plus
7 lb. 7 lb. 7 lb. 7 lb.
cellulose tallow. cornstarch. tallow plus 7 lb.
* "Aurofac A" containing 1.8 gm. aureomycin per pound.
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HE amount of research which has been conducted on fats and oils in poultry rations is comparatively small. This lack of interest in fats has been due to the fact that, first, a specific requirement for fat has not been clearly established with the chick or the adult bird; and secondly, the ingredients commonly used in poultry rations are presumed to supply sufficient fat to meet the ordinary needs of poultry. The demands of the rapidly growing chick for many of the vitamins and for protein have been found to be much greater than was first supposed. Conceivably, the energy requirement of the growing chick may likewise be higher than the caloric level provided by modern rations. This concept of high energy rations is already widely employed in broiler rations since the development of the "Connecticut ration" by Scott, Matterson and Singsen (1947). With regard to the use of fat as an energy source in poultry rations, Henderson and Irwin (1940) reported that up to 10 percent of soybean oil could be fed to chicks without affecting the rate of growth to 8 weeks of age. Similarly Siedler and Schweigert (1953) observed that growth and feed efficiency of chicks fed 2 and 8 percent of supplementary fat was equal to that of those fed a similar diet without the supplementary fat. Pepper, Slinger and Snyder (1953) showed that wheat-soya broiler diets were improved when supplemented with 2 percent of soybean oil.
1221
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS TABLE 2.—Average weights of chicks in Experiment 1 at 6 weeks of age and efficiency of feed utilization
Cockerels Ration
#1 (control) #2 (7 lb. cellulose) #3 (7 lb. tallow) #4 (7 lb. cornstarch) #5 (7 lb. tallow+7 lb. cornstarch)
ms
Wt. ^ ->
Pullets
Feed
Gain
654 639 680 642
2.27 2.33 1.98 2.15
702 679 698 687
2.21 2.22 1.90 2.06
0.51 0.47 0.41 0.44
651
2.11
682
2.02
0.40
750 719 715 732
2.15 2.10 1.82 1.98
714
1.93
Protein level of diet Ingredient 24%
100
lb. 100
28% 7.5 lb. 23.9 23.9 24.0 12.0 2.0 3.0 1.0 1.5 0.5 0.25 0.4 0.025 0 . 1 gm. 0 . 9 gm.
lb. 100
lb.
Lbs. gain
The composition of the basal diets is given in Table 3. Each of these three basal diets was in turn fed at three energy levels. The energy level was adjusted by replacing part or all of the cornstarch in the basal rations with tallow. The energy level of the diets was adjusted, therefore, without altering the amounts of the protein concentrates and cereals in the diets. The average weights of the chicks and the efficiency of feed utilization are given in Tables 4 and 5. Experiment 3. Growing turkeys utilize feed more efficiently than do chicks. To maintain a high degree of efficiency with the high-protein diets commonly fed, it was felt that there might be some advantage in increasing the available energy content of turkey broiler rations, particularly towards the end of the feeding period. In the following experiments edible tallow was used to raise the level of available energy beyond that attainable by the use of ingredients generally included in turkey broiler rations. Two experiments using turkeys as test animal have been carried out. Like the foregoing experiments with chicks, these tests were designed to compare the effect of different fat levels with rations containing different levels of protein. The levels of protein and fat in some of the diets have been varied every two weeks throughout the experiments. Other ra-
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TABLE 3.—Composition of basal diets in Experiment 2
7.5 lb. 7.5 lb. 34.2 28.3 34.2 28.3 10.0 18.0 5.0 9.0 2.0 2.0 3.0 3.0 1.0 1.0 2.0 1.75 0.5 0.5 0.25 0.25 0.4 0.4 0.025 0.025 0 . 1 gm 0 . 1 gm 0.9 gm 0.9 gm
Feed
Gain
Gain
to 100 lbs. of the supplemented diets with respect to all of the nutrients except the cellulose, tallow and cornstarch used in adjusting the energy content of the diets. In ration 5, 7 lbs. each of cornstarch and tallow were added to 93 lbs. of the control diet. In this ration, therefore, 107 lbs. were required to supply the nutrients provided by 93 lbs. of the control ration. The rations were fed ad lib. to day-old New Hampshire chicks. Each ration was fed to a lot of pullets and to a lot of cockerels. Growth rate and feed consumption were recorded every two weeks until 6 weeks of age. These data are summarized in Table 2. Experiment 2. Day-old New Hampshire chicks were fed diets containing 19, 24 and 28 percent of protein respectively.
cornstarch ground wheat ground yellow corn soybean oil meal fishmeal dried brewers' yeast livermeal limestone bonemeal iodized salt feeding oil (2.250A-300D) choline chloride (25%) manganese sulphate riboflavin nicotinic acid
Lbs. protein
Wt. tems->
Wt. tems")
19%
Feed
Average
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J. BIELY AND B. MARCH
TABLE 4.—Average weekly weights (grams) of chicks (Lots A and B) in Experiment 2
Description of Diet
Without antibiotic
With antibiotic
Weeks oi age
Weeks ol age 2
3
4
5
6
7
82
155
252
350
497
636
764
786 80 7 1 -2
156
259
387
535
686
817
1
3
11
8
8
7
84
164
266
394
538
680
804
84
168
272
405
563
722
851
0
2
2
3
5
6
6
2
3
4
5
6
7
19% protein
76
140
223
334
463
600
732
24% protein % gain over 19% diet
77 1
150 7
242 9
364 9
508 10
652 9
782 7
28% protein % gain over 19% diet % gain over 24% diet
80 5 4
154 10 3
250 12 3
370 11 2
515 652 9 11 0 1
19% protein, 5% tallow 24% protein, 5% tallow % gain over 19% diet
74 80 8
140 152 9
220 254 15
324 372 15
435 510 17
562 648 15
680 760 12
28% protein, 5 % tallow 78 % gain over 19% diet 5 % gain over 24% diet - 2
158 13 4
258 17 2
383 18 3
530 22 4
690 23 6
818 20 8
19% protein, 7.5% tallow
74
136
222
326
438
572
692
24% protein, 7.5% tallow % gain over 19% diet
81 9
160 18
262 18
389 19
536 22
678 19
817 18
83
164
264
392
528
656
796
28% protein, 7.5% tallow % gain over 19% diet % gain over 24% diet
79 7 0
156 15 -2
253 14 -3
377 16 -3
519 18 -3
633 11 -7
804 16 -2
86
170
276
408
562
713
850
4
4
5
4
6
9
7
tions were formulated in which the protein level was kept constant and the fat content was increased. In still other diets the protein level was gradually lowered TABLE 5.—Average weights of chicks in Experiment 2
at 7 weeks of age and efficiency of feed utilization Protein content of diet
Average w eights of chicks (gms.)
Feed
Lot A
Lot Avera age
Gain
Supplement to diet
19%
none 5 % tallow 7.5% tallow
736 686 694
728 675 690
732 680 692
2.39 2.43 2.47
24%
none aureomycin* 5 % tallow 5 % tallow plus aureomycin 7.5% tallow 7.5% tallow plus aureomycin
809 758 760
756 771 760
782 764 760
2.32 2.32 2.19
80.5 835
803 799
804 817
2.20 2.14
782
811
796
2.14
770 820 818
802 814 819
786 817 818
2.28 2.24 2.14
832 796
870 811
851 804
2.03 2.12
850
851
850
2.04
28%
none aureomycm 5 % tallow 5 % tallow plus aureomycin 7.5% tallow 7.5% tallow plus aureomycin
* 4.5 mg. aureomycin per pound from "Aurofac A.'
while the fat content was raised. The dietary regimens were as follows: 1. 28 percent protein 0-10 weeks. 2. 32, 29, 26, 23 and 20 percent protein with adjustments at 2, 4, 6 and 8 weeks. 3. 32, 29, 26, 23 and 20 percent protein with 0, 2, 4, 6 and 8 percent tallow, with adjustments at 2, 4, 6 and 8 weeks. 4. 32 percent protein 0-10 weeks. 0, 2, 4, 6 and 8 percent tallow with adjustments at 2,4, 6 and 8 weeks.
The composition of the 28 percent protein diet used in the experiment is shown in Table 6. In the other rations the supplements were maintained at the levels indicated in Table 6 but the protein concentrates and the cereals were varied to adjust the protein content of the rations to the desired levels. To prevent the development of rancidity in the rations containing added fat, the antioxidants propyl gallate and citric acid were added to the tallow. In the
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1
1
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS TABLE 6.—Composition of 28% protein diet in Experiments 3 and 4 Ingredient
25. SS 25.55 15.0 10.0 10.0 3.0 5.0 2.0 0.5 0.5 1.5 1.0 0.25 0.025 0.01 0.01 2.0 gm. 0.15gm. 0.45 gm. 400,000 units 60,000 units 0.0125 lb.
* "Aurofac A" containing 1.8 gm. aureomycin per lb.
rations without tallow, the antioxidants were added directly to the feed. Each dietary regimen was tested with lots of 23 male and 20 female day-old Beltsville Small White poults. Feed and water were kept before the birds at all times. The average weights of the birds and the efficiency of feed utilization are shown in Table 7.
The average weights of the turkeys at 10 weeks of age and the efficiency with which the birds utilized the experimental diets are given in Table 8. RESULTS AND DISCUSSION
The data obtained in these four experiments point to very similar conclusions regarding the use of supplementary fat
TABLE 7.—Average weights and efficiency of feed utilization of turkey poulls to 10 weeks of age in Experiment 3
Dietary Regimen
Males 2 8 % protein 32—20% protein 32—20% protein with tallow 3 2 % protein with tallow Females 2 8 % protein 32—20% protein 32—20% protein with tallow 3 2 % protein with tallow
2 wks.
4 wks.
6 wks.
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 28% diet
8 wks.
10 wks.
0-6 wks.
% incr. Wt. over (gms.) 2 8 % diet
% incr. Wt. over (gms.) 28% diet 2,547
Feed Gain
Feed Gain 0-10 wks.
1.94
1,716
' 191
-10
542
-6
1,004
-4
2.12
1,653
-4
2,399
-6
191
-10
548
-5
1,022
-2
1.89
1,700
-1
2,473
-3
2.24
191
-10
527
-9
993
-5
1.94
1,661
-3
2,435
-4
2.32
212
576
158
1,043
2.34
2.08
1,284
163
3
428
-2
786
-2
2.11
1,300
1
1,836
-1
167
6
455
4
827
3
1.99
1,353
5
1,917
3
2.32
169
7
447
2
817
2
2.01
1,322
3
1,866
0
2.46
437
800
1,858
2.50
2.49 2.38
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Experiment 4. A second experiment with turkeys sought to ascertain the effect of feeding different levels of protein and energy to turkeys to 10 weeks of age. Broad Breasted Bronze males and females were reared separately in battery brooders. In the light of results obtained in the previous experiment, the control protein level was fixed at 28 percent, i.e., the protein level was 28 percent in the basal diet and the rations were maintained at constant protein level throughout the experiment. The composition of this diet was similar to that given in Table 6. The vitamin and mineral supplements were maintained at the levels indicated in Table 6. Only the protein supplements and the cereals were adjusted. The dietary regimens were the same as those in the previous test except that the successive levels of protein fed were 28, 26, 24, 22 and 20 percent.
lbs./cwt.
ground yellow corn ground wheat soybean oil meal fishmeal meatrheal livermeal dried brewers' yeast dehydrated cereal grass iodized salt choline chloride (25%) bonemeal limestone antibiotic supplement* manganese sulphate propyl gallate citric acid nicotinic acid riboflavin calcium pantothenate vitamin A vitamin D3 sulfaquinoxaline
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J. BIELY AND B. MARCH TABLE 8.—Average weights and efficiency of feed utilization of turkey poults to 10 weeks of age in Experiment 4 2 wks.
Dietary Regimen
Males 28% protein 28—20% protein 28% protein with tallow 28—20% protein with tallow Females 28% protein
208
Wt. (gms.)
541
210
1
562
214
3
216
4
193
8 wks.
6 wks.
% incr. over 28% diet
% incr. over Wt. 28% (gms.) diet
2,722
Gain
-6
2.40
2,903
0-10 wks. 2.22
2,005
1,318
3
2,199
4
3,130
8
2.21
1,206
-5
2,018
-5
2,812
-3
2.30
578
7
565
4
1,692
1,072
4
498
4
1,019
-5
1,607
193
0
487
2
1,039,
-3
1,750
462
-3
971
-10
1,616
-2
-6
Feed
% incr. ovet 28% diet
-4
1,225
200
189
Wt. (gms.)
2,122
1,276 4
478
Wt. (gms.)
10 wks.
% incr. over 28% diet
in chick and poult rations. The greatest benefit from the addition of fat to the rations appeared in the efficiency with which rations containing supplementary fat were utilized. In experiment 1, for example, utilization of feed was affected to a greater extent than was the rate of growth of the chicks when the rations fed were "diluted." The rate of growth in the cockerels was reduced when cellulose, tallow or cornstarch was added to the basal diet. The growth rate of the pullets remained much the same on the various rations although tallow supplementation of the basal ration resulted in a faster rate of growth than was obtained with the basal ration. With the rations "diluted" with ground cellulose, the efficiency of feed utilization was the same as with the control ration. This means that the available nutrients were more efficiently utilized in the ration with additional bulk than in the control ration. Calculated on the basis of the protein consumed, the efficiency of protein utilization for the ration containing 7 percent cellulose was 0.47 as compared to a value of 0.51 for the basal ration. The extra bulk in the ration containing cellulose may have retarded the passage of
2,359 -5 3 -5
.2.26 2.38
2,223
-6
2,495
6
2.11
2,268
-4
2.39
feed through the digestive tract and permitted more complete utilization of the nutrients. Since the fibre from the added cellulose is not bound up with the other nutrients it probably does not interfere with digestion in the same way as it usually does in natural feedstuffs of high fibre content. The addition of tallow to the control ration improved the efficiency of feed utilization from 2.21 to 1.90. This difference represents a considerable saving in the other ingredients in the ration. Whereas the chicks in the control lot consumed 0.51 lb. of protein per lb. of gain, those in the two lots fed tallow consumed only 0.41 and 0.40 lb. of protein per lb. of gain. The addition of starch to the.control ration improved the efficiency of feed utilization to 2.06. This value does not represent so great a degree of efficiency as was attained by the addition of oil to the ration. Nevertheless it does indicate that the protein in the control ration was being "wasted" to some extent as an energy source. The efficiency of utilization of the rations containing both tallow and cornstarch was similar to that of the ration supplemented with cornstarch alone, in
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28—20% protein 28% protein with tallow 28—20% protein with tallow
Wt. (gms.)
4 wks.
% incr. over 28% diet
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS
The effect of tallow in depressing the rate of growth with the 19 percent protein diet but increasing it with higher levels of protein would indicate an interrelationship between protein and fat utilization in the chick. Studies with rats by Barnes, Primrose and Burr (1944) showed a low protein intake to be associated with low fat digestibility. Forbes et al. (1946a, b) also working with rats presented data to demonstrate that the energy utilization of the diet as a whole is improved when liberal amounts of fat
are supplied. With the rations not supplemented with tallow it will be seen (Table 4) that the chicks receiving 24 and 28 percent protein grew more rapidly than those receiving only 19 percent protein. The increased rate of growth was apparent during the first 2 weeks and did not vary appreciably percentage-wise from the rate of growth of chicks fed the control diet through to 7 weeks. Rates of growth did not vary between chicks fed the 24 percent and those fed the 28 percent ration. This is in accord with the results obtained by Almquist and Asmundson (1944) upon feeding White Leghorn cockerels mashes containing 30 and 20 percent of protein respectively. It was found that although the birds started on the high protein diet grew more quickly during the first week and maintained their advantage in weight to 8 weeks, there was no consistent variation in the percentage rate of increase. With the addition of 5 percent of oil to the rations the advantage with respect to rate of growth of the higher protein diets became more pronounced. Furthermore, it will be seen from Table 4 that percentage gain in growth between the 19 and the 24 and 28 percent protein rations increased as the birds became older. In the case of the rations without tallow, no difference appeared in the rates of growth of chicks fed 24 or 28 percent protein. When the rations were supplemented with 5 percent tallow, however, the chicks fed 28 percent protein grew faster from 4 to 8 weeks than those on 24 percent protein. When 7.5 percent of tallow was added to the rations, the chicks fed 24 and 28 percent protein again grew faster than those fed 19 percent protein. It has already been reported by Biely, March and Smith (1952) that a greater response can be expected to aureomycin
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spite of the fact that this ration was diluted to 107 lbs. The protein efficiency was indicative again that the energy content of the basal ration was suboptimal and that protein was being "wasted" as an energy source. In experiment 2 the protein levels of 19, 24 and 28 percent were chosen in order to determine if protein level had any effect on the response or tolerance of the growing chick for fat, and, conversely, if the fat level in the diet had any effect on the protein requirement of the chick for maximum growth rate. It will be seen (Table 5) that growth in the birds fed the 19 percent protein diets was depressed 52 and 40 grams respectively by the addition of 5.0 or 7.5 percent of tallow to the diet. When fat was added to the 19 percent diet the efficiency of feed utilization was lowered. The addition of fat to the diet containing 24 percent protein had no significant effect on growth. Feed efficiency, however, was improved with 5.0 and 7.5 percent fat by 5 and 8 percent respectively. Similarly at the 28 percent level of protein the increased rate of growth obtained by supplementing the basal diet with 5.0 or 7.5 percent of fat was not statistically significant. As with the 24 percent protein diet, however, efficiency was increased when fat was added to the 28 percent protein diet.
1225
1226
J. BIELY AND B. MARCH
one in which the protein level was reduced from 32 to 20 percent with the addition of 0 to 8 percent of tallow resulted in the most efficient utilization of feed. Lloyd, Reed and Fritz (1949) reported similar results on the feeding of high protein diets to turkeys. These investigators obtained the best growth to 7 or 8 weeks when the diet contained approximately 28 percent protein. They reported that while diets at the 32 percent protein level gave more rapid growth during the first two weeks, maintenance of this high level of protein beyond this period was found to be undesirable. In the second experiment using turkey poults the range of protein used was from 20 to 28 percent in view of the lack of response to higher levels in the previous experiment. In this experiment the poults (both males and females) fed 28 percent protein from 0 to 10 weeks grew faster than the poults receiving graded levels of protein. The addition of tallow to the rations fed under either regimen increased the weight of the poults at 10 weeks of age. It will be seen from the average weekly weights in Table 8 that the reduction of the protein level depressed the rate of growth at six weeks. When tallow was added to the 28 percent protein ration an increase in the rate of growth was observed in the males at 4 weeks and in the females at 8 weeks. The effect of supplementary tallow on the growth of the poults fed the rations in which the level of protein was lowered was not so striking as when the protein level was maintained at 28 percent. Nevertheless, by the time the poults were 10 weeks of age there was a slight difference in the average weights in favor of the rations supplemented with tallow. Feed utilization was most efficient with the ration maintained at 28 percent protein and supplemented with tallow. Low-
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at high protein levels than at low. Aureomycin was not added, therefore, to the rations at the 19 percent protein level in the present experiment. In the case of the 24 percent protein diets there was a response to aureomycin only with the ration supplemented with 5 percent of tallow. At the 28 percent protein level, however, there was a response to aureomycin with each of the different diets. When the 24 and the 28 percent protein rations were supplemented with aureomycin the 28 percent rations gave consistently better weights at 7 weeks of age than the 24 percent rations. It will be noted in addition that the percentage difference between the 24 and the 28 percent protein rations in the rate of growth was greatest from 4 to 8 weeks. This is at variance with the data of Almquist and Asmundson mentioned above. The experiments conducted with turkeys indicated that tallow could be added to poult rations without any adverse effect on growth. Under certain conditions it may be advantageous to add tallow for the effects on both growth rate and efficiency of feed utilization. In no instance where tallow was added to the rations did symptoms of hock disorder appear, as has been reported by Scott (1953) when cod liver oil was added to poult rations. In the first experiment using poults there appeared to be no advantage in starting poults at a protein level higher than 28 percent. Supplementation of the rations with increasing levels of tallow at the same time as the protein level was decreased resulted in a faster rate of growth and an improvement in feed efficiency as compared with growth rate and feed efficiency on the rations in which the protein was decreased without increasing the fat level. Of the four dietary regimens tested, the
FAT SUPPLEMENTS IN CHICK AND POULT RATIONS
ering the protein level in the rations from 28 to 20 percent lowered the feed efficiency as well as the rate of growth. The addition of tallow to the rations with the lower protein content raised the feed efficiency negligibly. Since the preparation of this paper, Sunde (1954) has reported that feed utilization was improved when up to 5 percent of fat was fed to either chicks or turkey poults.
Four experiments have been carried out to study the relationship between optimum protein and fat levels in chick and poult rations. With chicks it was found that the addition of fat to a 19 percent protein diet depressed growth and feed efficiency. When fat was added to a 24 percent or a 28 percent protein diet, growth was unaffected or stimulated and feed efficiency was improved. Supplementation with tallow increased the level of protein which might be considered to give maximum growth to 7 or 8 weeks. Fastest growth obtained to 7 weeks of age was with a 28 percent protein diet containing 5.0 or 7.5 percent of tallow and supplemented with aureomycin. With Beltsville Small White poults, the rate of growth to 10 weeks of age was faster with a ration maintained at 28 percent than with one starting at 32 percent and gradually reduced to 20 percent. With Broad Breasted Bronze poults, growth was faster when the ration was maintained at 28 percent protein than when it was gradually reduced to 20 percent. This was the case whether or not the rations were supplemented with tallow. The addition of tallow to the rations increased the rate of growth, particularly
in the ration maintained at 28 percent protein. In both chick and poult rations the addition of fat may be advantageous when relatively high levels of protein are fed. In rations in which the energy content is raised by the addition of fat, the level of protein which may be utilized efficiently is higher than in rations of lower energy content. REFERENCES Almquist, H. J., and V. S. Asmundson, 1944. High protein mashes for broilers. Poultry Sci. 23: 6771. Barnes, R. H., M. F. Primrose and G. O. Burr, 1944. The influence of the protein content of the diet upon fat digestibility. J. Nutrition, 27: 179-184. Biely, J., B. E. March and D. F. Smith, 1952. Effect of feeding antibiotics on the carbohydrate and protein requirements of the chick. Poultry Sci. 31:863-870. Forbes, E. B., R. W. Swift, R. F. Elliott and W. H. James, 1946a. Relation of fat to economy of food utilization (I) by the growing albino rat. J. Nutrition, 31: 203-212. Forbes, E. B., R. W. Swift, R. F. Elliott and W. H. James, 1946b. Relation of fat to economy of food utilization (II) by the mature albino rat. J. Nutrition, 31: 213-227. Henderson, E. W., and W. E. Irwin, 1940. The tolerance of growing chicks for soybean oil in their ration. Poultry Sci. 19: 389-395. Lloyd, M. D., C. A. Reed and J. C. Fritz, 1949. Experiences with high protein diets for chicks and poults. Poultry Sci. 28: 69-74 Pepper, W. F., S. J. Slinger and E. S. Snyder, 1953. Value of low levels of soybean oil in broiler diets containing a high percentage of wheat. Poultry Sci. 32: 1084-1085. Scott, H. M., L. D. Matterson and E. P. Singsen, 1947. Nutrition factors influencing growth and efficiency of feed utilization. I. The effect of the source of carbohydrate. Poultry Sci. 26:554. Scott, M. L., 1953. Prevention of the enlarged hock disorder in turkeys with niacin and vitamin E. Poultry Sci. 32:670-677. Siedler, A. J., and B. S. Schweigert, 1953. Effect of feeding graded levels of fat with and without choline and antibiotic+Bi 2 supplements to chicks. Poultry Sci. 32: 449-.454. Sunde, M. L., 1954. The use of animal fats in poultry feeds. J. Amer. Oil Chem. Soc. 31: 49-52.
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SUMMARY
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