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The Energy Value of Fats and Fatty Acids for Chicks
The Energy Value of Fats and Fatty Acids for Chicks 2. EVALUATED BY CONTROLLED FEED INTAKE ROBERT J. YOUNG1 AND NEIL R. AKTMAN The Procter and Gamble Company, Miami Valley Laboratories, Cincinnati 39, Ohio
T
(Received for publication February 20, 1961)
1 Present address: Department of Poultry Husbandry, Cornell University, Ithaca, New York.
able energy added to the diet. When feed intake is limited so that each experimental group consumes the same amount of feed, differences in the caloric density of the diets and increased feed consumption of chicks receiving the low energy diets will no longer be experimental variables. It is, of course, essential that all the chicks receive adequate amounts of all nutrients, and especially that the Calorie to protein ratio be adequate for the chicks receiving the highest levels of dietary energy. EXPERIMENTAL PROCEDURE AND RESULTS
Preliminary Experiment. The purposes of this experiment were to determine whether growth and feed efficiency of chicks fed ad libitum could be used to evaluate the utilizable energy in fats which have different absorbability values, and to determine the Calorie to protein ratio needed for linear results. Degummed soybean oil and edible beef tallow were used as the fats of high and low absorbability, respectively. Graded levels of each fat were added to 23.9% and 28% protein diets at increments of 3 % in place of cellulose (Solka-Floc). The compositions of the 23.9% and 28% protein diets are shown in Table 1. Each diet in any one protein series provided the same amount of all nutrients except for the amount of energy which was changed by adding graded levels of fat. The diets were fed ad libitum for four weeks to three pens of ten Peterson X White Rock cockerels each. The four-week results of this experiment are shown in Figures 1 and 2. The results obtained with chicks fed the 23.9% protein
653
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HE absorbability values of free fatty acid mixtures from hydrolyzed lard and beef tallow were found by Young (1961) to be significantly higher than values reported by Renner and Hill (1958). To evaluate further the utilizable energy in fats, and perhaps to help explain the above discrepancy, it was desirable to have another procedure for evaluating the utilizable energy of fats and fatty acids for poultry. The comparison of the response of animals fed graded amounts of a test material with the response of animals fed graded levels of a standard has been used for evaluating the quality of protein (Hinners and Scott, 1957) and the availability of dietary nutrients such as phosphorus (Gillis, Norris and Heuser, 1954) and zinc (Edwards, 1959). This method of evaluating the utilizable energy in fats is limited by the fact that substituting fat for a non-digestible ingredient such as cellulose alters the caloric density of the diets; moreover, the chick can compensate for a low energy intake by increasing its food consumption. The restricted or equalized feeding of rats has been used by Rice, Warner, Mone and' Poling (1957) for comparing the metabolic energy content of various foods. Rand, Scott and Kummerow (1958) used a similar technique to evaluate the growth stimulating effect of corn oil for the chick. It therefore appears that chicks fed equal amounts of a basal diet which is adequate in all nutrients but low in calories will gain weight in proportion to the amount of avail-
1654
R. J. YOUNG AND N. R. ARTMAN
TABLE 1.—Diets for preliminary experiment
Protein concentrate21 Vitamin mixture #3 Mineral mixture #23 Dicalcium phosphate Ground limestone Glucose (cerelose) Cellulose (Solka-Floc) Total Crude protein Metabolizable energy, Cal./ 100 g.
28% Protein
24% Protein
%
15.0
/o 66.0 1.0 3.5 2.2 1.0 11.3 15.0
100.0 28.0
100.0 23.91
230
238
77.3 1.0 3.5 2.2 1.0
—
The protein concentrate contained: 45.28% soybean oil meal (50% protein), 32.54% ground yellow corn, 5.17% isolated soybean protein (Archer Daniels Midland, C-l Assay Protein), 6.47% fish meal (60% protein), 2.59% dehydrated alfalfa meal (17% protein), 2.59% dried whole whey (12% protein), 3.23% distillers dried solubles, 1.29% corn oil, 0.388% DL-methionine, and 0.161% L-lysine HC1. 2 This amount of vitamin mixture supplied: 400 mg. choline CI (25% concentrate), 100 mg. vitamin B12 concentrate (1.3 mg./lOO g.), 50 mg. stabilized vitamin A (10,000 I.U./g.), 50 mg. dry vitamin E (220 units/g.), 2.0 mg. vitamin D 3 (200,000 I.C.U./ g.), 4.0 mg. thiamine, 4.0 mg. niacin, 1.0 mg. Ca pantothenate, 0.4 mg. riboflavin, 0.3 mg. pyridoxine, 0.25 mg. menadione, 0.2 mg. folic acid, 0.03 mg. biotin, and 387.82 mg. glucose. 3 The mineral mixture supplied: 0.8 g. iodized NaCl, 1.0 g. KC1, 1.5 g. MgSO„-xH 2 0, 0.04 g. MnS0 4 -H 2 0, 0.04 g. FeS0 4 -7H 2 0, 0.005 g. ZnS0 4 •7H 2 0, 0.002 g. CuSCv5H 2 0,0.001 g. CoCl 2 -6H 2 0, 0.0001 g. NaMo0 4 -2H 2 0, and 0.1119 g. CaC0 3 .
diet (Figure 1) show that when the metabolizable energy Calorie to protein ratio exceeds about 13.4,2 then protein limits the growth of chicks. When this Calorie to protein ratio is exceeded it is not possible to compare the responses of chicks to fats of different absorbabilities, since the more highly absorbed fats exceed the optimum Calorie to protein ratio at lower dietary levels than the less well absorbed fats. These results illustrate the danger of using too low an energy value for a fat in the formulation of diets. For example, if the 2
Ratio of 13.4 Calories of metabolizable energy per 100 grams of diet for each per cent protein in the diet is equivalent to a ratio of 61 metabolizable energy Cal./lb./unit protein.
GAIN/FEED BEEF TALLOW
FIG. 1. Four-week growth (solid line) and feed conversion (broken line) of chicks fed the 24% protein diet with graded levels of soybean oil ( • ) and beef tallow (x). Figures in parentheses are the Calories of metabolizable energy per 100 grams of diet for each percent of dietary protein using 9.26 Cal./g. for soybean oil and 6.S Cal./g. for beef tallow. Vertical lines through each point represent the mean ± the standard error of the mean.
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1
single productive energy value of 2,900 Cal./lb. were assigned to a well utilized and a poorly utilized fat for calculation of the Calorie to protein ratio, then the energy value of the well utilized fat would be underestimated, the Calorie to protein ratio would be too high, and growth of the chicks would be limited by the protein level. Chicks which received the corresponding diet containing poorly utilized fat would have an optimum Calorie to protein ratio, but their growth would be limited by the Calorie level. Therefore, the growth response obtained would make the two fats appear to be similar. In the 28% protein series, the critical metabolizable energy Calorie to protein ratio of 13.4 was not exceeded with the highest level of fat. Therefore, growth and feed
1655
UTILIZATION OF FATS AND FATTY ACIDS
3 Although the metabolizable energy value of soybean oil has been found to be 9.26 Cal./g. (Renner and Hill, 19S8; Young, 1961), the apparent digestibility as determined in a number of experiments in this laboratory using diets similar to those fed in the present work has been found to average 96.5% (Young, 1961). Therefore, the gross energy of 9.4 X 96.5 = 9.07 Cal./g. has been used as the metabolizable energy value of soybean oil in calculating the utilizable energy of the various test fats.
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FIG. 2. Four-week growth (solid line) and feed conversion (broken line) of chicks fed the 28% protein diet with graded levels of soybean oil ( • ) and beef tallow (x). Figures in parentheses are the Calories of metabolizable energy per 100 grams of diet for each percent of dietary protein using 9.26 Cal./g. for soybean oil and 6.5 Cal./g. for beef tallow. Vertical lines through each point represent the mean ± the standard error of the mean.
periments feed intake was carefully regulated in order to eliminate this uncontrolled variable. Controlled Feeding Experiments. Three controlled feeding experiments were conducted to compare the results obtained by this method with the results of the more conventional metabolizable energy and absorbability determinations. Degummed refined soybean oil was selected as the standard reference fat in these experiments, since it is well utilized by the chick and is consistent in performance (Renner and Hill, 1958; Young, 1961). Figure 3 shows the response curves which were obtained in the three experiments when the basal diet was supplemented with graded levels of soybean oil. The utilizable energy of each test fat
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conversion were not limited by the amount of protein and the responses of the chicks were related to the available energy of the fats. In the 28% protein series, the diets containing 6, 9 and 12% beef tallow produced the same growth response as would have been produced by diets containing 3.7, 6.7 and 9.4% soybean oil, respectively. This comparison shows that, on the average, beef tallow supplies about 70% as much energy as soybean oil. Since the energy value of soybean oil3 is 9.07 Calories per gram, the energy value of beef tallow would then calculate to be about 6.35 Calories per gram. The responses of the chicks fed the 3% fat in both protein series show that when the diets are low in energy the chicks are able to compensate for the difference in utilizable energy of the two fats by a higher intake of the diet containing the beef tallow. Although chicks fed the diets containing the higher levels of beef tallow also overate, as shown by the poorer feed conversion, they apparently were not able to eat enough to compensate completely for the lower utilizable energy of beef tallow as compared to soybean oil. This experiment established that a biological comparison of fat is possible, provided that the Calorie to protein ratio of 13.4 is not exceeded. However, it appears that a closer control of feed intake would be necessary to evaluate fats which may not be so widely different in utilizable energy as are soybean oil and beef tallow. Therefore, in the following ex-
16S6
R. J. YOUNG AND N. R. ARTMAN
34
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They were then allotted to groups of eight chicks each on an equal weight basis, and restricted feeding of the experimental diets was started at the beginning of the fourth day. Each group of chicks was restricted to the same amount of feed regardless of diet. The method of calculating the amount of ration fed is described under each experiment. By this procedure of controlled feeding, each group in each experiment, regardless of diet, consumed the same amount of feed in each 24-hour period. The chicks were brooded in a windowless room where the lights were automatically controlled to go out four hours after the regular feeding 360time and to come on again after another ten hours. It was found that at the end of °4 6 8 10 12 14 16 !8 20 22 Percent Soybean 01! four hours the chicks had consumed about FIG. 3. Growth and feed conversion of chicks one-half the feed offered. Therefore, this fed graded levels of soybean oil but restricted to controlled light period forced the chicks to the same total daily feed intake within each expericonsume the second half of their daily food ment. Figures in parentheses are the average feed supply in the last half of each 24-hour peconversion values (feed/gram gain) for the reriod. This procedure was equivalent to spective groups. Vertical lines through each point represent the mean ± the standard error of the twice a day feeding and prevented those mean. groups on the relatively low energy diets from consuming their daily allotment durwas determined by comparing the response ing the first 12 hours, while the groups fed curve for the test fat with the soybean oil the relatively high energy diets had feed reference curve from the corresponding ex- available over 20 to 22 hours each day. periment. The results of such comparisons Experiment 1. The basal diet used in the can be expressed in terms of soybean oil first restricted feeding experiment is shown equivalents (SBO equiv.) or estimated as in Table 2. The soybean oil was substituted Calories. The SBO equiv. was calculated as for cellulose at levels of 11, 16.5 and 22% the level of test fat which resulted in a of the diet; each of the test fats, edible beef given growth response divided into the (in- tallow and hydrolyzed animal and vegetable terpolated) level of soybean oil which gave fat, was fed at levels of 11% and 22%. the same growth response. This value mul- All rations contained 33% protein, so that tiplied by the metabolizable energy value the highest energy diet (22% soybean oil) of soybean oil3 was designated the utilizable had a Calorie to protein ratio of 11.8, well energy of the test fat as compared to soy- below the critical value of 13.4 found in the bean oil. preliminary experiment. The diet was Day-old chicks which were to be fed un- formulated to supply the same amounts of der conditions of restricted feeding in each protein, vitamins and minerals on a daily experiment were fed ad libitum for the first basis when restricted to 90% of that conthree days the diet containing the lowest sumed by chicks fed ad libitum a 30% level of soybean oil in that experiment. protein diet high in fat and adequate
1657
UTILIZATION OF FATS AND FATTY ACIDS
4
The calculated amount of each nutrient required per 100 grams of gain for chicks fed the high protein, high fat diet indicated the protein in the basal diet would be limiting in both methionine and lysine. In a separate four-week experiment, chicks showed a definite response to 0.3% methionine but did not show a further increase when 0.1% lysine was added. Therefore, lysine was not added to this diet. All other nutrients were added at levels to supply the amounts indicated by the method of calculation described by Edwards and Young (1959).
TABLE 2.—Diets for controlled feeding experiments
Soybean oil meal (50% protein) Ground yellow corn Isolated soya bean protein 1 Fish meal (60% protein) Dehydrated alfalfa meal (17% protein) Dried whole whey (12% protein) Distillers dried solubles DL-methionine Dicalcium phosphate Ground limestone Vitamin mixture #3 2 Mineral mixture #22 Chromic oxide bread Cellulose3 Total
Experiment 1
Experiments 2 and 3
%
%
46 3.3 6.0 5.6
46 10.3 5.0 5.6
2.2
2.2
2.2 2.8 0.3 2.5 1.1 1.1 3.9 1.0 22
2.2 2.8 0.3 2.5 1.1 1.1 3.9 1.0 16
100.0
100.0
1
Archer Daniels Midland C-l Assay Protein. The vitamin and mineral mixtures were the same mixtures described in Table 1, footnotes 2 and 3. The quantity of each was increased 10% for the controlled feeding diets. 3 Brown Company, Chicago, Illinois—Solka-Floc BNB-40. 2
70% as much utilizable energy as soybean oil. Compared to the metabolizable energy value of 9.07 Cal./g. for soybean oil3 these fats would have energy values of 8.25 and 6.35 Cal./g. The values are similar to the metabolizable energy values of 8.22 and 6.56 Cal./g. (Young, 1961) for these same fats, and show that the restricted feeding technique should be a useful method for the comparative evaluation of fats. Experiment 2. Since the 22% soybean oil diet of experiment 1 did not give a linear growth response as compared to the 11% and 16% soybean oil diets, the levels of soybean oil used to obtain the reference curve for experiment 2 (Figure 3) were reduced to 6, 11 and 16%. The other dietary ingredients were adjusted as shown in Table 2. The experimental technique was the same as in experiment 1. In this experiment, however, the restricted chicks were given 95% as much feed as was consumed
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in all nutrients. The amount of each nutrient required per 100 g. of gain by the chick was calculated by the procedure of Edwards and Young (1959)4 to insure that they were supplied at levels which would not limit the growth of the chicks fed the high energy diets. Three lots of White Rock cockerels were fed the 22% soybean oil diet ad libitum. Their feed consumption was measured daily. Each of the other diets was fed daily to four groups of eight chicks each in such amount that the average daily intake was equal to 90% of the average daily intake of the birds fed ad libitum. The lower curve of Figure 3 shows the growth response of the chicks to the increasing levels of soybean oil in the diet. The response to 22% soybean oil was not linear as compared to the other levels. The reason for this is not known. Since the chicks fed the 22% soybean oil diet ad libitum showed good growth and feed conversion (Table 3) it does not appear that an imbalance in the diet is responsible. At lower levels of soybean oil the growth response can be compared reliably with the growth response from the other fats. The results of this comparison and the other observations made from this experiment are shown in Table 3. These results show that the hydrolyzed animal and vegetable fat and the beef tallow yield, respectively, about 9 1 % and
1658
R. J. YOUNG AND N. R. ARTMAN
TABLE 3.—Evaluation of the utilizable energy in fats by controlled feeding of chicks Average weight 4 weeks2 A. Restricted feeding1 11% Beef tallow 22% Beef tallow Average 11% Hydrolyzed animal and vegetable fat6 22% Hydrolyzed animal and vegetable fat6 Soybean oil B. Ad Libitum feeding 22% Soybean oil
Feed/gram 1 gain
Average SBO equiv. 3
1) Calculated utilizable energy value 4 Cal./g.
358 + 5.9 457 + 9.1
1.95 1.49
0.66 0.73 0.70 0.91
6.35 8.25 390 + 9.3 1.77 5 482 + 7.5 1.40 (See growth curve for experiment 1, Fig. 3) 551 + 7.3
1.37
by the chicks fed the 16% soybean oil diet ad libitum,5 rather than the 90% used in experiment 1. In addition, the ad libitum fed chicks in experiment 2 ate more of the 16% soybean oil diet than did the chicks fed ad libitum the 22% soybean oil diet in experiment 1. Therefore, the restricted chicks received more feed, and growth was significantly higher in the second experiment (Figure 3). The absorbability value of each fat was determined during the fourth week with both the ad libitum and the restricted fed chicks. Details of the method have been published previously (Young, 1961). Five different fats or fatty acid mixtures were tested individually. In addition, a specific mixture of these individual fats and 5
The average daily ad libitum feed intake for a group of eight Arbor Acre White Rock chicks or eight Vantress X White Rock chicks fed the diet containing 16% soybean oil during the first 28 days for any specific day was found to be (26 + 12 a) and (30 + 13.6 a), respectively; where a = the specific day (1 through 28), 12 and 13.6 = average daily increase in feed consumption for eight chicks, and 26 and 30 = average grams of feed consumed at day one by eight chicks.
fatty acids was prepared and compared to soybean oil. The hydrolyzed animal and vegetable fat used in the first experiment was also evaluated in this experiment. Each test fat was fed at 11% and 16% of the diet. The description and analyses of the fats and fatty acids are given in Table 4. The results of the experiment are shown in Table 5. The utilizable energy values of each fat based on the soybean oil equivalents are in good agreement with the energy value calculated from the absorbability value times 9.4 Cal./g. There is also good agreement between the soybean oil equivalent found for the composited mixture and the value calculated from the soybean oil equivalents of its components. The utilizable energy value of 8.43 Cal./g. calculated from the soybean oil equivalent determined in this experiment for the hydrolyzed animal and vegetable fat is slightly higher than the value of 8.25 Cal./g. found in experiment 1. The average of seven estimates of the energy value of this fat is 8.24 Cal./g. These estimates are the following: 8.25 and 8.43, determined by the restricted feeding technique; 8.29 and
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1 All groups were restricted to 90% of the feed consumption of those chicks fed the 22% soybean oil diet ad libitum 2 Average of four groups of eight chicks. 3 Soybean oil equivalent (see text). 4 9.07 Cal./g. for soybean oil times SBO equiv. 5 The soybean oil curve was not linear at this growth level. Therefore, the SBO equiv. was not considered reliable for this fat at the 22% level. 6 The Procter and Gamble Company's commercial feed fat HEF®.
1659
UTILIZATION OF FATS AND FATTY ACIDS TABLE 4.—Analyses of fats evaluated in the second restricted feeding experiment Free Fatty Acids
Total Fatty Acids
Description
%
/o
40.0 97.0 75.6 67.8 75.4 13.6 45.9
96.0 95.1 97.5 93.7 96.1 94.7 95.3
%
1.6 0.7 3.5 1.7 3.1 0.6 1.5
%
0.4 2.9 0.6 1.4 1.1 0.4 0.9
Iodine Value
70.6 50.3 66.6 56.5 130.0 56.5 65.3
The Procter and Gamble Company's commercial feed fat HEF®.
measurements with four- and eight-week-old chicks (Young, 1961). The absorbability values for soybean oil, hydrolyzed animal and vegetable fat, and
8.27, determined by absorbability measurements; and the previously reported values of 8.22, 8.24 and 7.99 based on metabolizable energy measurements and absorbability
TABLE 5.—Evaluation of the utilizable energy in fats and fatty acids by controlled feeding of chicks {experiment 2) Average four week results—level of dietary fat
n%
Treatments Average weight 2 A. Restricled feed intake Soybean oil Hydrolyzed animal and vegetable fat 7 F a t t y acids recovered from tallow refining foots F a t s recovered from continuous soap making F a t s from soap processing F a t t y acids recovered from soybean oil refining foots Animal fat (yellow grease) Composite mixture B. Ad libitum Soybean oil Hydrolyzed animal and vegetable fat 7 Composite mixture 1 2 3 4
Feed/ gain
16% SBO equiv. 4
g.
Average weight 3
F e e d / SBO equiv. 4 gain
Average SBO equiv. 4
Utilizable % Absorbenergy value ability 3-4 9.4 Cal./g. calculated weeks 16% X % absorbability from SBO fat level
g-
(See growth curve for experiment;2, Fig. 3)
1.00
(9.07)5
—
—
450+ 8.7
1.68
0.91
506+ 9.6
1.46
0.96
0.93
8.43
0.88
8.29
411+
7.5
1.85
0.65
462+ 9.8
1.63
0.70
0.68
6.17
0.66
6.20
418+ 6.8
1.82
0.71
460+ 8.9
1.63
0.69
0.70
6.35
0.72
6.77
428+13.7
1.77
0.77
489+11.1
1.52
0.86
0.82
7.44
0.76
7.14
441+ 6.2
1.71
0.83
488+ 3.6
1.52
0.85
0.84
7.62
0.84
7.90
437+ 9.9 436± 5.5
1.73 1.73
0.84 0.83
497+10.9 486± 8.4
1.50 1.53
0.91 0.84
0.88 7.98 0.86 8.08 0.84(0.82)5 7.62 (7.44)» 0 . 7 7 ( 0 . 8 0 ) 7.24(7.52)
— — — — — —
566+10.3
1.48
555+10.2 553±12.1
1.54 1.56
— — —
— — — — — —
— — —
0.93
8.74
0.88 0.73
8.27 6.86
See Table 3 for detailed description of the various fats. Diets containing 11% fat and diets fed ad libitum were each fed to three groups of eight chicks each. Diets containing 16% fat fed to two groups of eight chicks each except as noted in footnote 2. Soybean oil equivalent (see text). 5 Soybean oil was assigned a value of 9.07 Cal./g. based on an average absorbability value of 95.6% observedi n several experiments in this laboratory. 6 Values in parentheses are the.SBO equiv. and per cent absorbability, respectively, calculated for the mixture shown in Table 4 from the actual values found for the individual fats and fatty acids. ' The Procter and Gamble Company's commercial feed fat HEF®.
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Hydrolyzed animal and vegetable fat 1 Fatty acids recovered from tallow refining foots Fats recovered from continuous soapmaking Fats from soap processing Fatty acids recovered from soybean oil refining foots Animal fat (yellow grease) Composite mixture 10 parts fatty acids recovered from tallow refining foots 20 parts fats recovered from continuous soapmaking 10 parts fats from soap processing 10 parts fatty acids recovered from soybean oil refining foots 50 parts animal fat (yellow grease)
Unsaponifiable Moisture Matter
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R. J. YOUNG AND N. R. ARTMAN
TABLE 6.—Evaluation of the utilizable energy in intact and hydrolyzed triglycerides by the controlled feeding of chicks {experiment 3) Average four-week results—level of dietary fat
Average weight'
B. Ad tibitum Soybean oil 1 2 R 4
^ed/ 8 .
AbSBQ equiv.2 sorba-3 bility
Average weight 1
%
g.
Feed/ gram gain
AbSBO equiv.1 sorba-3 bility
1.68 1.64 1.74 1.76 1.81
0.96 1.04 0.86 0.82 0.75
88 91 83 79 69
equfv
fatlCTd
%
g-
94 482+7.6 493+7.7 469+7.3 463 + 6.7 454+8.7
Utilizable energy 9.4 Cal./g. AYirage ^ X%.abSB .° calculated " " I » ™ y equiv.22 , at 16% ST10
549+11.5 545+11.8 530+10.0 518+11.8 495+ 7.7
1.44 1.46 1.50 1.55 1.63
610+ 9.5
1.46
1.00 1.00 0.92 0.86 0.73
95
1.00
(9.07)«
8.93
89 92 85 78 73
0.98 1.02 0.89 0.84 0.74
8.89 9.25 8.07 7.62 6.71
8.37 8.65 7.99 7.33 6.86
96
9.02
Average results of three groups of eight chicks each. Soybean oil equivalent (see text). Absorbability values are not corrected for small amount of fat in basal ingredients. See footnote 5, Table 5.
the composited mixture, which were determined in the present work with the chicks fed ad libitum, agreed with the corresponding values from the chicks whose feed was restricted. Thus, it appears that the feeding of fat under conditions of restricted feed intake does not affect absorbability. Similar observations were reported by Fedde, Waibel and Burger (1959), who found that restriction of feed intake to 80% and 60% of controls produced no change in the digestibility of tallow. Experiment 3. This experiment was designed to evaluate the utilizable energy of three triglycerides, soybean oil, lard and beef tallow, and of the fatty acids formed by the hydrolysis of each of these triglycerides. The restricted feeding technique described for the second experiment was duplicated in this experiment except that Vantress X White Rock cockerels were used as the experimental chicks. The growth curve for chicks fed the graded levels of soybean oil is linear and shows the same slope as the curve for the other two experiments (Figure 3).- The Vantress X White Rock cockerels used in this experiment showed a greater growth po-
tential than the White Rock cockerels used in the previous experiments; this increased growth is evident with chicks fed the soybean oil diet both ad libitum and by restricted feeding. The results (Table 6) confirm the observations made in the previous paper (Young, 1961), which showed that although the utilizable energy value of fats decreases upon hydrolysis, the decrease is not as great as that observed by Renner and Hill (1958). The absorbabilities of the various fats and fatty acids were similar at both the 11% and 16% levels of supplemental fat in the diet. The energy values calculated from the absorbability values times 9.4 Cal./g. are in good agreement with the utilizable energy values calculated from the soybean oil equivalent times 9.07 Cal./g. These values also agree with the metabolizable energy values and absorbability values determined by Young (1961) for the intact soybean oil and lard and for the free fatty acid mixtures from hydrolyzed soybean oil and lard. However, the utilizable energy values and absorbability values for beef tallow and the beef tallow fatty acids determined in this
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A. Restricted feed intake Soybean oil (see growth curve for experiment 3, Fig. 3) Soybean oil fatty acids Lard Lard fatty acids Beef tallow Beef tallow fatty acids
16%
11%
Treatment
UTILIZATION OF FATS AND FATTY ACIDS
experiment were significantly higher than the corresponding values determined by Young (1961) for similar material. DISCUSSION
and hydrolyzed triglycerides. The utilizable energy values confirm the metabolizable energy values reported by Young (1961) and show that under these experimental conditions the lard fatty acids and beef tallow fatty acids have a higher energy value for the chick than was found by Renner and Hill (1958). The reason for this discrepancy is not known, although there was a difference in the strains of chicks used, and this could be responsible. The utilizable energy value and absorbability of the beef tallow fatty acids in this experiment were higher than the metabolizable energy values for this material reported by Young (1961). This result could be attributed to some characteristic of the restricted feeding technique, but since no such discrepancy appears with the other fats or fatty acids, and since the utilizable energy values and absorbability values agree with each other for all the fats, including beef tallow fatty acids, it seems more likely that this discrepancy also reflects differences in the breeds of chicks used. SUMMARY Certain fats were evaluated by a method whereby all chicks were carefully restricted to the same feed intake. The utilizable energy in various fats and fatty acids was determined by comparing the growth responses of chicks fed the test fats to growth responses of chicks fed graded levels of soybean oil. This biological evaluation of these fats gave utilizable energy values which were in good agreement with the metabolizable energy values and absorbability values. The absorbability values of these fats were not affected by restricted feeding or by the level of fat in the diet. The restricted feeding technique was used to evaluate the utilizable energy value of intact and hydrolyzed fats. The utilizable energy values of soybean
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The procedure of restricted feeding of chicks described in these experiments gives an evaluation of the utilizable energy in various fats. This procedure eliminates the need for analyzing the feed and excreta for moisture, fat, chromic oxide, nitrogen and combustible energy as is done in determinations of absorbability and metabolizable energy. In addition, no involved assumptions and calculations are necessary to correct for endogenous fat and nitrogen retention. The utilizable energy values calculated from the soybean oil equivalents agree well with the absorbability and metabolizable energy values of various fats and fatty acids; hence, the procedure does measure the energy actually available to the chick. It is recognized that chicks fed the low fat (low energy) diets on a restricted basis will utilize some of the protein in the diet as a source of energy. Just how much energy is derived from this source by the chick is not known; however, the growth response at thei various levels of fat is linear, and the soybean oil equivalents determined at the 11 and 16% fat levels are in good agreement. Therefore, the amount of energy derived from the protein does not appear to be a significant variable in evaluating fats by controlled feeding. No change in utilization was apparent when several fats and fatty acid mixtures with different amounts of utilizable energy were mixed together. The energy content of the mixture calculated from the utilizable energy values of the individual component fats was in good agreement with the value actually determined for the mixture. The restricted feeding technique was used to evaluate the utilizable energy in intact
1661
1662
R. J. YOUNG AND N. R. ARTMAN
oil fatty acids, lard and lard fatty acids were found to be similar to their respective metabolizable energy values. Beef tallow and beef tallow fatty acids showed utilizable energy values slightly higher than their metabolizable energy values. REFERENCES
Estimates of Egg Quality Parameters Utilizing a Polyallel Crossing System1,2 C. E. REDMAN3 AND R. N. SHOFFNER Poultry Department, Minnesota Agricultural Experiment Station, St. Paul, Minnesota (Received for publication February 21, 1961) V
' I HE applications of a diallel crossing -•• system for obtaining genetic information was put on a practical basis with the publication of the classical paper of Sprague and Tatum (1942). Although, in poultry studies, many of the assumptions of the theoretical models may not be fulfilled, the diallel crossing system is a powerful breeding scheme for obtaining genetic informa1 Published as paper No. 4562, Scientific Journal Series of the Minnesota Agricultural Experiment Station, St. Paul, Minnesota. This work is in cooperation with the North Central Regional Poultry Breeding Project, NC-47. 2 Portion of a thesis submitted by the senior author to the Graduate School, University of Minnesota, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. 3 Presently with Eli Lilly and Company, Indianapolis, Indiana.
tion. This is indicated by the many recent publications: Kan et al. (1959), Hill (1959), King and Mitchell (1959), Goodman and Jaap (1960), and others. However, the idea of mating sires to more than one dam and vice versa is not a new technique. The increased usage is a result of recent developments in theoretical genetics. Many workers, such as Henderson (1948, 1953), Hayman (1954a,b, 1957, 1958), Kempthorne (1956), Matzinger and Kempthorne (1956), have developed the theoretical models necessary for the interpretation of the diallel mating system. Griffing (1956a, 1958), developed the thoretical genetical models used in this study. REVIEW OF HERITABILITY ESTIMATES
Estimates of heritability for specific gravity have been reported by Johnson and Mer-
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Edwards, H. M., Jr., 1959. The availability to chicks of zinc in various compounds and ores. J. Nutrition, 69: 306-308. Edwards, H. M., Jr., and R. J. Young, 1959. Calculation of the nutrient requirements for broilers. Poultry Sci. 38: 1430-1432. Fedde, M. R., P. E. Waibel and R. E. Burger, 1959. Factors affecting the digestibility of certain dietary fats in the chick. Poultry Sci. 38: 1203. Gillis, M. B., L. C. Norris and G. F. Heuser, 1954.
Studies on the biological value of inorganic phosphates. J. Nutrition, 52: 115-125. Hinners, S. W., and H. M. Scott, 1957. A bioassay for determining the nutritional adequacy of protein supplements for chick growth. Poultry Sci. 36: 1126. Rand, N. T., H. M. Scott and F. A. Kummerow, 1958. Dietary fat in the nutrition of the growing chick. Poultry Sci. 37: 1075-1085. Renner, R., and F. W. Hill, 1958. Metabolizable energy values of fats and fatty acids for chickens. Proc. Cornell Nutrition Conference for Feed Manufacturers, pp. 95-100. Rice, E. E., W. D. Warner, P. E. Mone and C. E. Poling, 1957. Comparison of the metabolic energy contributions of foods by growth under conditions of energy restriction. J. Nutrition, 61: 253-266. Young, R. J., 1961. The energy value of fats and fatty acids for chicks. 1. Metabolizable energy. Poultry Sci. 40: 1225-1233.
T
(Received for publication February 20, 1961)
1 Present address: Department of Poultry Husbandry, Cornell University, Ithaca, New York.
able energy added to the diet. When feed intake is limited so that each experimental group consumes the same amount of feed, differences in the caloric density of the diets and increased feed consumption of chicks receiving the low energy diets will no longer be experimental variables. It is, of course, essential that all the chicks receive adequate amounts of all nutrients, and especially that the Calorie to protein ratio be adequate for the chicks receiving the highest levels of dietary energy. EXPERIMENTAL PROCEDURE AND RESULTS
Preliminary Experiment. The purposes of this experiment were to determine whether growth and feed efficiency of chicks fed ad libitum could be used to evaluate the utilizable energy in fats which have different absorbability values, and to determine the Calorie to protein ratio needed for linear results. Degummed soybean oil and edible beef tallow were used as the fats of high and low absorbability, respectively. Graded levels of each fat were added to 23.9% and 28% protein diets at increments of 3 % in place of cellulose (Solka-Floc). The compositions of the 23.9% and 28% protein diets are shown in Table 1. Each diet in any one protein series provided the same amount of all nutrients except for the amount of energy which was changed by adding graded levels of fat. The diets were fed ad libitum for four weeks to three pens of ten Peterson X White Rock cockerels each. The four-week results of this experiment are shown in Figures 1 and 2. The results obtained with chicks fed the 23.9% protein
653
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HE absorbability values of free fatty acid mixtures from hydrolyzed lard and beef tallow were found by Young (1961) to be significantly higher than values reported by Renner and Hill (1958). To evaluate further the utilizable energy in fats, and perhaps to help explain the above discrepancy, it was desirable to have another procedure for evaluating the utilizable energy of fats and fatty acids for poultry. The comparison of the response of animals fed graded amounts of a test material with the response of animals fed graded levels of a standard has been used for evaluating the quality of protein (Hinners and Scott, 1957) and the availability of dietary nutrients such as phosphorus (Gillis, Norris and Heuser, 1954) and zinc (Edwards, 1959). This method of evaluating the utilizable energy in fats is limited by the fact that substituting fat for a non-digestible ingredient such as cellulose alters the caloric density of the diets; moreover, the chick can compensate for a low energy intake by increasing its food consumption. The restricted or equalized feeding of rats has been used by Rice, Warner, Mone and' Poling (1957) for comparing the metabolic energy content of various foods. Rand, Scott and Kummerow (1958) used a similar technique to evaluate the growth stimulating effect of corn oil for the chick. It therefore appears that chicks fed equal amounts of a basal diet which is adequate in all nutrients but low in calories will gain weight in proportion to the amount of avail-
1654
R. J. YOUNG AND N. R. ARTMAN
TABLE 1.—Diets for preliminary experiment
Protein concentrate21 Vitamin mixture #3 Mineral mixture #23 Dicalcium phosphate Ground limestone Glucose (cerelose) Cellulose (Solka-Floc) Total Crude protein Metabolizable energy, Cal./ 100 g.
28% Protein
24% Protein
%
15.0
/o 66.0 1.0 3.5 2.2 1.0 11.3 15.0
100.0 28.0
100.0 23.91
230
238
77.3 1.0 3.5 2.2 1.0
—
The protein concentrate contained: 45.28% soybean oil meal (50% protein), 32.54% ground yellow corn, 5.17% isolated soybean protein (Archer Daniels Midland, C-l Assay Protein), 6.47% fish meal (60% protein), 2.59% dehydrated alfalfa meal (17% protein), 2.59% dried whole whey (12% protein), 3.23% distillers dried solubles, 1.29% corn oil, 0.388% DL-methionine, and 0.161% L-lysine HC1. 2 This amount of vitamin mixture supplied: 400 mg. choline CI (25% concentrate), 100 mg. vitamin B12 concentrate (1.3 mg./lOO g.), 50 mg. stabilized vitamin A (10,000 I.U./g.), 50 mg. dry vitamin E (220 units/g.), 2.0 mg. vitamin D 3 (200,000 I.C.U./ g.), 4.0 mg. thiamine, 4.0 mg. niacin, 1.0 mg. Ca pantothenate, 0.4 mg. riboflavin, 0.3 mg. pyridoxine, 0.25 mg. menadione, 0.2 mg. folic acid, 0.03 mg. biotin, and 387.82 mg. glucose. 3 The mineral mixture supplied: 0.8 g. iodized NaCl, 1.0 g. KC1, 1.5 g. MgSO„-xH 2 0, 0.04 g. MnS0 4 -H 2 0, 0.04 g. FeS0 4 -7H 2 0, 0.005 g. ZnS0 4 •7H 2 0, 0.002 g. CuSCv5H 2 0,0.001 g. CoCl 2 -6H 2 0, 0.0001 g. NaMo0 4 -2H 2 0, and 0.1119 g. CaC0 3 .
diet (Figure 1) show that when the metabolizable energy Calorie to protein ratio exceeds about 13.4,2 then protein limits the growth of chicks. When this Calorie to protein ratio is exceeded it is not possible to compare the responses of chicks to fats of different absorbabilities, since the more highly absorbed fats exceed the optimum Calorie to protein ratio at lower dietary levels than the less well absorbed fats. These results illustrate the danger of using too low an energy value for a fat in the formulation of diets. For example, if the 2
Ratio of 13.4 Calories of metabolizable energy per 100 grams of diet for each per cent protein in the diet is equivalent to a ratio of 61 metabolizable energy Cal./lb./unit protein.
GAIN/FEED BEEF TALLOW
FIG. 1. Four-week growth (solid line) and feed conversion (broken line) of chicks fed the 24% protein diet with graded levels of soybean oil ( • ) and beef tallow (x). Figures in parentheses are the Calories of metabolizable energy per 100 grams of diet for each percent of dietary protein using 9.26 Cal./g. for soybean oil and 6.S Cal./g. for beef tallow. Vertical lines through each point represent the mean ± the standard error of the mean.
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1
single productive energy value of 2,900 Cal./lb. were assigned to a well utilized and a poorly utilized fat for calculation of the Calorie to protein ratio, then the energy value of the well utilized fat would be underestimated, the Calorie to protein ratio would be too high, and growth of the chicks would be limited by the protein level. Chicks which received the corresponding diet containing poorly utilized fat would have an optimum Calorie to protein ratio, but their growth would be limited by the Calorie level. Therefore, the growth response obtained would make the two fats appear to be similar. In the 28% protein series, the critical metabolizable energy Calorie to protein ratio of 13.4 was not exceeded with the highest level of fat. Therefore, growth and feed
1655
UTILIZATION OF FATS AND FATTY ACIDS
3 Although the metabolizable energy value of soybean oil has been found to be 9.26 Cal./g. (Renner and Hill, 19S8; Young, 1961), the apparent digestibility as determined in a number of experiments in this laboratory using diets similar to those fed in the present work has been found to average 96.5% (Young, 1961). Therefore, the gross energy of 9.4 X 96.5 = 9.07 Cal./g. has been used as the metabolizable energy value of soybean oil in calculating the utilizable energy of the various test fats.
SOYBEAN OIL
(ll-OU BEEF TALLOW
560
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doaZ
£ £ 540
/]
/
/
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/I
• , ' ' GAIN/FEED , ' ' SOYBEAN OIL"
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5 520 * 500
5
•19.6)
19.2*^-^'^ /f(&9)
5
-
/ I
' \ ''
/_[ /
480
/
'
f
'
' GAIN/FEED , ' ' * BEEF TALLOW
" x
y
*'
,''
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460
'/ /' * 44q
ke.z)
420
"/
400
/ i
i
i
i
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FIG. 2. Four-week growth (solid line) and feed conversion (broken line) of chicks fed the 28% protein diet with graded levels of soybean oil ( • ) and beef tallow (x). Figures in parentheses are the Calories of metabolizable energy per 100 grams of diet for each percent of dietary protein using 9.26 Cal./g. for soybean oil and 6.5 Cal./g. for beef tallow. Vertical lines through each point represent the mean ± the standard error of the mean.
periments feed intake was carefully regulated in order to eliminate this uncontrolled variable. Controlled Feeding Experiments. Three controlled feeding experiments were conducted to compare the results obtained by this method with the results of the more conventional metabolizable energy and absorbability determinations. Degummed refined soybean oil was selected as the standard reference fat in these experiments, since it is well utilized by the chick and is consistent in performance (Renner and Hill, 1958; Young, 1961). Figure 3 shows the response curves which were obtained in the three experiments when the basal diet was supplemented with graded levels of soybean oil. The utilizable energy of each test fat
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conversion were not limited by the amount of protein and the responses of the chicks were related to the available energy of the fats. In the 28% protein series, the diets containing 6, 9 and 12% beef tallow produced the same growth response as would have been produced by diets containing 3.7, 6.7 and 9.4% soybean oil, respectively. This comparison shows that, on the average, beef tallow supplies about 70% as much energy as soybean oil. Since the energy value of soybean oil3 is 9.07 Calories per gram, the energy value of beef tallow would then calculate to be about 6.35 Calories per gram. The responses of the chicks fed the 3% fat in both protein series show that when the diets are low in energy the chicks are able to compensate for the difference in utilizable energy of the two fats by a higher intake of the diet containing the beef tallow. Although chicks fed the diets containing the higher levels of beef tallow also overate, as shown by the poorer feed conversion, they apparently were not able to eat enough to compensate completely for the lower utilizable energy of beef tallow as compared to soybean oil. This experiment established that a biological comparison of fat is possible, provided that the Calorie to protein ratio of 13.4 is not exceeded. However, it appears that a closer control of feed intake would be necessary to evaluate fats which may not be so widely different in utilizable energy as are soybean oil and beef tallow. Therefore, in the following ex-
16S6
R. J. YOUNG AND N. R. ARTMAN
34
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They were then allotted to groups of eight chicks each on an equal weight basis, and restricted feeding of the experimental diets was started at the beginning of the fourth day. Each group of chicks was restricted to the same amount of feed regardless of diet. The method of calculating the amount of ration fed is described under each experiment. By this procedure of controlled feeding, each group in each experiment, regardless of diet, consumed the same amount of feed in each 24-hour period. The chicks were brooded in a windowless room where the lights were automatically controlled to go out four hours after the regular feeding 360time and to come on again after another ten hours. It was found that at the end of °4 6 8 10 12 14 16 !8 20 22 Percent Soybean 01! four hours the chicks had consumed about FIG. 3. Growth and feed conversion of chicks one-half the feed offered. Therefore, this fed graded levels of soybean oil but restricted to controlled light period forced the chicks to the same total daily feed intake within each expericonsume the second half of their daily food ment. Figures in parentheses are the average feed supply in the last half of each 24-hour peconversion values (feed/gram gain) for the reriod. This procedure was equivalent to spective groups. Vertical lines through each point represent the mean ± the standard error of the twice a day feeding and prevented those mean. groups on the relatively low energy diets from consuming their daily allotment durwas determined by comparing the response ing the first 12 hours, while the groups fed curve for the test fat with the soybean oil the relatively high energy diets had feed reference curve from the corresponding ex- available over 20 to 22 hours each day. periment. The results of such comparisons Experiment 1. The basal diet used in the can be expressed in terms of soybean oil first restricted feeding experiment is shown equivalents (SBO equiv.) or estimated as in Table 2. The soybean oil was substituted Calories. The SBO equiv. was calculated as for cellulose at levels of 11, 16.5 and 22% the level of test fat which resulted in a of the diet; each of the test fats, edible beef given growth response divided into the (in- tallow and hydrolyzed animal and vegetable terpolated) level of soybean oil which gave fat, was fed at levels of 11% and 22%. the same growth response. This value mul- All rations contained 33% protein, so that tiplied by the metabolizable energy value the highest energy diet (22% soybean oil) of soybean oil3 was designated the utilizable had a Calorie to protein ratio of 11.8, well energy of the test fat as compared to soy- below the critical value of 13.4 found in the bean oil. preliminary experiment. The diet was Day-old chicks which were to be fed un- formulated to supply the same amounts of der conditions of restricted feeding in each protein, vitamins and minerals on a daily experiment were fed ad libitum for the first basis when restricted to 90% of that conthree days the diet containing the lowest sumed by chicks fed ad libitum a 30% level of soybean oil in that experiment. protein diet high in fat and adequate
1657
UTILIZATION OF FATS AND FATTY ACIDS
4
The calculated amount of each nutrient required per 100 grams of gain for chicks fed the high protein, high fat diet indicated the protein in the basal diet would be limiting in both methionine and lysine. In a separate four-week experiment, chicks showed a definite response to 0.3% methionine but did not show a further increase when 0.1% lysine was added. Therefore, lysine was not added to this diet. All other nutrients were added at levels to supply the amounts indicated by the method of calculation described by Edwards and Young (1959).
TABLE 2.—Diets for controlled feeding experiments
Soybean oil meal (50% protein) Ground yellow corn Isolated soya bean protein 1 Fish meal (60% protein) Dehydrated alfalfa meal (17% protein) Dried whole whey (12% protein) Distillers dried solubles DL-methionine Dicalcium phosphate Ground limestone Vitamin mixture #3 2 Mineral mixture #22 Chromic oxide bread Cellulose3 Total
Experiment 1
Experiments 2 and 3
%
%
46 3.3 6.0 5.6
46 10.3 5.0 5.6
2.2
2.2
2.2 2.8 0.3 2.5 1.1 1.1 3.9 1.0 22
2.2 2.8 0.3 2.5 1.1 1.1 3.9 1.0 16
100.0
100.0
1
Archer Daniels Midland C-l Assay Protein. The vitamin and mineral mixtures were the same mixtures described in Table 1, footnotes 2 and 3. The quantity of each was increased 10% for the controlled feeding diets. 3 Brown Company, Chicago, Illinois—Solka-Floc BNB-40. 2
70% as much utilizable energy as soybean oil. Compared to the metabolizable energy value of 9.07 Cal./g. for soybean oil3 these fats would have energy values of 8.25 and 6.35 Cal./g. The values are similar to the metabolizable energy values of 8.22 and 6.56 Cal./g. (Young, 1961) for these same fats, and show that the restricted feeding technique should be a useful method for the comparative evaluation of fats. Experiment 2. Since the 22% soybean oil diet of experiment 1 did not give a linear growth response as compared to the 11% and 16% soybean oil diets, the levels of soybean oil used to obtain the reference curve for experiment 2 (Figure 3) were reduced to 6, 11 and 16%. The other dietary ingredients were adjusted as shown in Table 2. The experimental technique was the same as in experiment 1. In this experiment, however, the restricted chicks were given 95% as much feed as was consumed
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in all nutrients. The amount of each nutrient required per 100 g. of gain by the chick was calculated by the procedure of Edwards and Young (1959)4 to insure that they were supplied at levels which would not limit the growth of the chicks fed the high energy diets. Three lots of White Rock cockerels were fed the 22% soybean oil diet ad libitum. Their feed consumption was measured daily. Each of the other diets was fed daily to four groups of eight chicks each in such amount that the average daily intake was equal to 90% of the average daily intake of the birds fed ad libitum. The lower curve of Figure 3 shows the growth response of the chicks to the increasing levels of soybean oil in the diet. The response to 22% soybean oil was not linear as compared to the other levels. The reason for this is not known. Since the chicks fed the 22% soybean oil diet ad libitum showed good growth and feed conversion (Table 3) it does not appear that an imbalance in the diet is responsible. At lower levels of soybean oil the growth response can be compared reliably with the growth response from the other fats. The results of this comparison and the other observations made from this experiment are shown in Table 3. These results show that the hydrolyzed animal and vegetable fat and the beef tallow yield, respectively, about 9 1 % and
1658
R. J. YOUNG AND N. R. ARTMAN
TABLE 3.—Evaluation of the utilizable energy in fats by controlled feeding of chicks Average weight 4 weeks2 A. Restricted feeding1 11% Beef tallow 22% Beef tallow Average 11% Hydrolyzed animal and vegetable fat6 22% Hydrolyzed animal and vegetable fat6 Soybean oil B. Ad Libitum feeding 22% Soybean oil
Feed/gram 1 gain
Average SBO equiv. 3
1) Calculated utilizable energy value 4 Cal./g.
358 + 5.9 457 + 9.1
1.95 1.49
0.66 0.73 0.70 0.91
6.35 8.25 390 + 9.3 1.77 5 482 + 7.5 1.40 (See growth curve for experiment 1, Fig. 3) 551 + 7.3
1.37
by the chicks fed the 16% soybean oil diet ad libitum,5 rather than the 90% used in experiment 1. In addition, the ad libitum fed chicks in experiment 2 ate more of the 16% soybean oil diet than did the chicks fed ad libitum the 22% soybean oil diet in experiment 1. Therefore, the restricted chicks received more feed, and growth was significantly higher in the second experiment (Figure 3). The absorbability value of each fat was determined during the fourth week with both the ad libitum and the restricted fed chicks. Details of the method have been published previously (Young, 1961). Five different fats or fatty acid mixtures were tested individually. In addition, a specific mixture of these individual fats and 5
The average daily ad libitum feed intake for a group of eight Arbor Acre White Rock chicks or eight Vantress X White Rock chicks fed the diet containing 16% soybean oil during the first 28 days for any specific day was found to be (26 + 12 a) and (30 + 13.6 a), respectively; where a = the specific day (1 through 28), 12 and 13.6 = average daily increase in feed consumption for eight chicks, and 26 and 30 = average grams of feed consumed at day one by eight chicks.
fatty acids was prepared and compared to soybean oil. The hydrolyzed animal and vegetable fat used in the first experiment was also evaluated in this experiment. Each test fat was fed at 11% and 16% of the diet. The description and analyses of the fats and fatty acids are given in Table 4. The results of the experiment are shown in Table 5. The utilizable energy values of each fat based on the soybean oil equivalents are in good agreement with the energy value calculated from the absorbability value times 9.4 Cal./g. There is also good agreement between the soybean oil equivalent found for the composited mixture and the value calculated from the soybean oil equivalents of its components. The utilizable energy value of 8.43 Cal./g. calculated from the soybean oil equivalent determined in this experiment for the hydrolyzed animal and vegetable fat is slightly higher than the value of 8.25 Cal./g. found in experiment 1. The average of seven estimates of the energy value of this fat is 8.24 Cal./g. These estimates are the following: 8.25 and 8.43, determined by the restricted feeding technique; 8.29 and
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1 All groups were restricted to 90% of the feed consumption of those chicks fed the 22% soybean oil diet ad libitum 2 Average of four groups of eight chicks. 3 Soybean oil equivalent (see text). 4 9.07 Cal./g. for soybean oil times SBO equiv. 5 The soybean oil curve was not linear at this growth level. Therefore, the SBO equiv. was not considered reliable for this fat at the 22% level. 6 The Procter and Gamble Company's commercial feed fat HEF®.
1659
UTILIZATION OF FATS AND FATTY ACIDS TABLE 4.—Analyses of fats evaluated in the second restricted feeding experiment Free Fatty Acids
Total Fatty Acids
Description
%
/o
40.0 97.0 75.6 67.8 75.4 13.6 45.9
96.0 95.1 97.5 93.7 96.1 94.7 95.3
%
1.6 0.7 3.5 1.7 3.1 0.6 1.5
%
0.4 2.9 0.6 1.4 1.1 0.4 0.9
Iodine Value
70.6 50.3 66.6 56.5 130.0 56.5 65.3
The Procter and Gamble Company's commercial feed fat HEF®.
measurements with four- and eight-week-old chicks (Young, 1961). The absorbability values for soybean oil, hydrolyzed animal and vegetable fat, and
8.27, determined by absorbability measurements; and the previously reported values of 8.22, 8.24 and 7.99 based on metabolizable energy measurements and absorbability
TABLE 5.—Evaluation of the utilizable energy in fats and fatty acids by controlled feeding of chicks {experiment 2) Average four week results—level of dietary fat
n%
Treatments Average weight 2 A. Restricled feed intake Soybean oil Hydrolyzed animal and vegetable fat 7 F a t t y acids recovered from tallow refining foots F a t s recovered from continuous soap making F a t s from soap processing F a t t y acids recovered from soybean oil refining foots Animal fat (yellow grease) Composite mixture B. Ad libitum Soybean oil Hydrolyzed animal and vegetable fat 7 Composite mixture 1 2 3 4
Feed/ gain
16% SBO equiv. 4
g.
Average weight 3
F e e d / SBO equiv. 4 gain
Average SBO equiv. 4
Utilizable % Absorbenergy value ability 3-4 9.4 Cal./g. calculated weeks 16% X % absorbability from SBO fat level
g-
(See growth curve for experiment;2, Fig. 3)
1.00
(9.07)5
—
—
450+ 8.7
1.68
0.91
506+ 9.6
1.46
0.96
0.93
8.43
0.88
8.29
411+
7.5
1.85
0.65
462+ 9.8
1.63
0.70
0.68
6.17
0.66
6.20
418+ 6.8
1.82
0.71
460+ 8.9
1.63
0.69
0.70
6.35
0.72
6.77
428+13.7
1.77
0.77
489+11.1
1.52
0.86
0.82
7.44
0.76
7.14
441+ 6.2
1.71
0.83
488+ 3.6
1.52
0.85
0.84
7.62
0.84
7.90
437+ 9.9 436± 5.5
1.73 1.73
0.84 0.83
497+10.9 486± 8.4
1.50 1.53
0.91 0.84
0.88 7.98 0.86 8.08 0.84(0.82)5 7.62 (7.44)» 0 . 7 7 ( 0 . 8 0 ) 7.24(7.52)
— — — — — —
566+10.3
1.48
555+10.2 553±12.1
1.54 1.56
— — —
— — — — — —
— — —
0.93
8.74
0.88 0.73
8.27 6.86
See Table 3 for detailed description of the various fats. Diets containing 11% fat and diets fed ad libitum were each fed to three groups of eight chicks each. Diets containing 16% fat fed to two groups of eight chicks each except as noted in footnote 2. Soybean oil equivalent (see text). 5 Soybean oil was assigned a value of 9.07 Cal./g. based on an average absorbability value of 95.6% observedi n several experiments in this laboratory. 6 Values in parentheses are the.SBO equiv. and per cent absorbability, respectively, calculated for the mixture shown in Table 4 from the actual values found for the individual fats and fatty acids. ' The Procter and Gamble Company's commercial feed fat HEF®.
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Hydrolyzed animal and vegetable fat 1 Fatty acids recovered from tallow refining foots Fats recovered from continuous soapmaking Fats from soap processing Fatty acids recovered from soybean oil refining foots Animal fat (yellow grease) Composite mixture 10 parts fatty acids recovered from tallow refining foots 20 parts fats recovered from continuous soapmaking 10 parts fats from soap processing 10 parts fatty acids recovered from soybean oil refining foots 50 parts animal fat (yellow grease)
Unsaponifiable Moisture Matter
1660
R. J. YOUNG AND N. R. ARTMAN
TABLE 6.—Evaluation of the utilizable energy in intact and hydrolyzed triglycerides by the controlled feeding of chicks {experiment 3) Average four-week results—level of dietary fat
Average weight'
B. Ad tibitum Soybean oil 1 2 R 4
^ed/ 8 .
AbSBQ equiv.2 sorba-3 bility
Average weight 1
%
g.
Feed/ gram gain
AbSBO equiv.1 sorba-3 bility
1.68 1.64 1.74 1.76 1.81
0.96 1.04 0.86 0.82 0.75
88 91 83 79 69
equfv
fatlCTd
%
g-
94 482+7.6 493+7.7 469+7.3 463 + 6.7 454+8.7
Utilizable energy 9.4 Cal./g. AYirage ^ X%.abSB .° calculated " " I » ™ y equiv.22 , at 16% ST10
549+11.5 545+11.8 530+10.0 518+11.8 495+ 7.7
1.44 1.46 1.50 1.55 1.63
610+ 9.5
1.46
1.00 1.00 0.92 0.86 0.73
95
1.00
(9.07)«
8.93
89 92 85 78 73
0.98 1.02 0.89 0.84 0.74
8.89 9.25 8.07 7.62 6.71
8.37 8.65 7.99 7.33 6.86
96
9.02
Average results of three groups of eight chicks each. Soybean oil equivalent (see text). Absorbability values are not corrected for small amount of fat in basal ingredients. See footnote 5, Table 5.
the composited mixture, which were determined in the present work with the chicks fed ad libitum, agreed with the corresponding values from the chicks whose feed was restricted. Thus, it appears that the feeding of fat under conditions of restricted feed intake does not affect absorbability. Similar observations were reported by Fedde, Waibel and Burger (1959), who found that restriction of feed intake to 80% and 60% of controls produced no change in the digestibility of tallow. Experiment 3. This experiment was designed to evaluate the utilizable energy of three triglycerides, soybean oil, lard and beef tallow, and of the fatty acids formed by the hydrolysis of each of these triglycerides. The restricted feeding technique described for the second experiment was duplicated in this experiment except that Vantress X White Rock cockerels were used as the experimental chicks. The growth curve for chicks fed the graded levels of soybean oil is linear and shows the same slope as the curve for the other two experiments (Figure 3).- The Vantress X White Rock cockerels used in this experiment showed a greater growth po-
tential than the White Rock cockerels used in the previous experiments; this increased growth is evident with chicks fed the soybean oil diet both ad libitum and by restricted feeding. The results (Table 6) confirm the observations made in the previous paper (Young, 1961), which showed that although the utilizable energy value of fats decreases upon hydrolysis, the decrease is not as great as that observed by Renner and Hill (1958). The absorbabilities of the various fats and fatty acids were similar at both the 11% and 16% levels of supplemental fat in the diet. The energy values calculated from the absorbability values times 9.4 Cal./g. are in good agreement with the utilizable energy values calculated from the soybean oil equivalent times 9.07 Cal./g. These values also agree with the metabolizable energy values and absorbability values determined by Young (1961) for the intact soybean oil and lard and for the free fatty acid mixtures from hydrolyzed soybean oil and lard. However, the utilizable energy values and absorbability values for beef tallow and the beef tallow fatty acids determined in this
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A. Restricted feed intake Soybean oil (see growth curve for experiment 3, Fig. 3) Soybean oil fatty acids Lard Lard fatty acids Beef tallow Beef tallow fatty acids
16%
11%
Treatment
UTILIZATION OF FATS AND FATTY ACIDS
experiment were significantly higher than the corresponding values determined by Young (1961) for similar material. DISCUSSION
and hydrolyzed triglycerides. The utilizable energy values confirm the metabolizable energy values reported by Young (1961) and show that under these experimental conditions the lard fatty acids and beef tallow fatty acids have a higher energy value for the chick than was found by Renner and Hill (1958). The reason for this discrepancy is not known, although there was a difference in the strains of chicks used, and this could be responsible. The utilizable energy value and absorbability of the beef tallow fatty acids in this experiment were higher than the metabolizable energy values for this material reported by Young (1961). This result could be attributed to some characteristic of the restricted feeding technique, but since no such discrepancy appears with the other fats or fatty acids, and since the utilizable energy values and absorbability values agree with each other for all the fats, including beef tallow fatty acids, it seems more likely that this discrepancy also reflects differences in the breeds of chicks used. SUMMARY Certain fats were evaluated by a method whereby all chicks were carefully restricted to the same feed intake. The utilizable energy in various fats and fatty acids was determined by comparing the growth responses of chicks fed the test fats to growth responses of chicks fed graded levels of soybean oil. This biological evaluation of these fats gave utilizable energy values which were in good agreement with the metabolizable energy values and absorbability values. The absorbability values of these fats were not affected by restricted feeding or by the level of fat in the diet. The restricted feeding technique was used to evaluate the utilizable energy value of intact and hydrolyzed fats. The utilizable energy values of soybean
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The procedure of restricted feeding of chicks described in these experiments gives an evaluation of the utilizable energy in various fats. This procedure eliminates the need for analyzing the feed and excreta for moisture, fat, chromic oxide, nitrogen and combustible energy as is done in determinations of absorbability and metabolizable energy. In addition, no involved assumptions and calculations are necessary to correct for endogenous fat and nitrogen retention. The utilizable energy values calculated from the soybean oil equivalents agree well with the absorbability and metabolizable energy values of various fats and fatty acids; hence, the procedure does measure the energy actually available to the chick. It is recognized that chicks fed the low fat (low energy) diets on a restricted basis will utilize some of the protein in the diet as a source of energy. Just how much energy is derived from this source by the chick is not known; however, the growth response at thei various levels of fat is linear, and the soybean oil equivalents determined at the 11 and 16% fat levels are in good agreement. Therefore, the amount of energy derived from the protein does not appear to be a significant variable in evaluating fats by controlled feeding. No change in utilization was apparent when several fats and fatty acid mixtures with different amounts of utilizable energy were mixed together. The energy content of the mixture calculated from the utilizable energy values of the individual component fats was in good agreement with the value actually determined for the mixture. The restricted feeding technique was used to evaluate the utilizable energy in intact
1661
1662
R. J. YOUNG AND N. R. ARTMAN
oil fatty acids, lard and lard fatty acids were found to be similar to their respective metabolizable energy values. Beef tallow and beef tallow fatty acids showed utilizable energy values slightly higher than their metabolizable energy values. REFERENCES
Estimates of Egg Quality Parameters Utilizing a Polyallel Crossing System1,2 C. E. REDMAN3 AND R. N. SHOFFNER Poultry Department, Minnesota Agricultural Experiment Station, St. Paul, Minnesota (Received for publication February 21, 1961) V
' I HE applications of a diallel crossing -•• system for obtaining genetic information was put on a practical basis with the publication of the classical paper of Sprague and Tatum (1942). Although, in poultry studies, many of the assumptions of the theoretical models may not be fulfilled, the diallel crossing system is a powerful breeding scheme for obtaining genetic informa1 Published as paper No. 4562, Scientific Journal Series of the Minnesota Agricultural Experiment Station, St. Paul, Minnesota. This work is in cooperation with the North Central Regional Poultry Breeding Project, NC-47. 2 Portion of a thesis submitted by the senior author to the Graduate School, University of Minnesota, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. 3 Presently with Eli Lilly and Company, Indianapolis, Indiana.
tion. This is indicated by the many recent publications: Kan et al. (1959), Hill (1959), King and Mitchell (1959), Goodman and Jaap (1960), and others. However, the idea of mating sires to more than one dam and vice versa is not a new technique. The increased usage is a result of recent developments in theoretical genetics. Many workers, such as Henderson (1948, 1953), Hayman (1954a,b, 1957, 1958), Kempthorne (1956), Matzinger and Kempthorne (1956), have developed the theoretical models necessary for the interpretation of the diallel mating system. Griffing (1956a, 1958), developed the thoretical genetical models used in this study. REVIEW OF HERITABILITY ESTIMATES
Estimates of heritability for specific gravity have been reported by Johnson and Mer-
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Edwards, H. M., Jr., 1959. The availability to chicks of zinc in various compounds and ores. J. Nutrition, 69: 306-308. Edwards, H. M., Jr., and R. J. Young, 1959. Calculation of the nutrient requirements for broilers. Poultry Sci. 38: 1430-1432. Fedde, M. R., P. E. Waibel and R. E. Burger, 1959. Factors affecting the digestibility of certain dietary fats in the chick. Poultry Sci. 38: 1203. Gillis, M. B., L. C. Norris and G. F. Heuser, 1954.
Studies on the biological value of inorganic phosphates. J. Nutrition, 52: 115-125. Hinners, S. W., and H. M. Scott, 1957. A bioassay for determining the nutritional adequacy of protein supplements for chick growth. Poultry Sci. 36: 1126. Rand, N. T., H. M. Scott and F. A. Kummerow, 1958. Dietary fat in the nutrition of the growing chick. Poultry Sci. 37: 1075-1085. Renner, R., and F. W. Hill, 1958. Metabolizable energy values of fats and fatty acids for chickens. Proc. Cornell Nutrition Conference for Feed Manufacturers, pp. 95-100. Rice, E. E., W. D. Warner, P. E. Mone and C. E. Poling, 1957. Comparison of the metabolic energy contributions of foods by growth under conditions of energy restriction. J. Nutrition, 61: 253-266. Young, R. J., 1961. The energy value of fats and fatty acids for chicks. 1. Metabolizable energy. Poultry Sci. 40: 1225-1233.