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The Effect of Level of Feed Intake on Metabolizable Energy Values Measured with Adult Roosters
The Effect of Level of Feed Intake on Metabolizable Energy Values Measured with Adult Roosters I. R. SlBBALD Animal Research Institute, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6 (Received for publication March 12, 1975)
POULTRY SCIENCE 54; 1990-1997, 1975
INTRODUCTION
A
PPARENT dietary metabolizable energy (M.E.) values should vary with the level of feed intake because, under standardized conditions, the excretion of metabolic fecal energy (FE m ) plus endogenous urinary energy (UE e ) is constant. When feed energy intake is high the energy loss as F E m + U E e is relatively small but as the energy intake is reduced these energy losses become increasingly significant and should depress the apparent M.E. value. This hypothesis has been explained by Guillaume and Summers (1970) using theoretical values and while it is logical it does not appear to have been proven in poultry with experimental data. Hill and Anderson (1958) reduced the feed consumption of chicks to as little as 30% of ad libitum and found no effect of level of feed intake on dietary M.E. values. Potter et al. (1960) also restricted the feed consumption of chicks and found that the M.E. per gram of diet increased with the degree of
Contribution No. 566.
restriction. This finding tends to contradict that of Hill and Anderson (1958) and is the opposite of what is expected if the initial hypothesis is correct. Lockhart et al. (1966) found that deficiencies of B-vitamins depressed observed M.E. values. The changes may have been associated with reduced feed intakes but this cannot be proven. The experiments described in this paper were designed to test the hypothesis that apparent dietary M.E. values decrease when the energy consumption is reduced, all other conditions being constant. Such information is important to those concerned with the development of M.E. bioassays and with the measurement of the M.E. values of diets and ingredients.
MATERIALS AND METHODS Experiment 1. Adult S.C.W.L. roosters of the Kentville Control Strain were housed in individual wire cages in a windowless room where they received 12 hr. of light each day. Alternate cages were left vacant to minimize the possibility of cross contamination of
1990
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ABSTRACT Two experiments were made with S.C.W.L. roosters to test the hypothesis that the apparent M.E. value of a feedingstuff is affected by the level of intake. In the first experiment the birds were starved for 18 hr. and then fed varying amounts of whole wheat. Excreta voided during the 24 hr. experimental period was collected quantitatively and assayed for gross energy. Energy voided as excreta increased in a linear manner as the intake of wheat increased. The apparent M.E. value also varied with wheat consumption according to the equation M.E. (kcal./g.) = 3.17X - 8.5/X where: 3.17 kcal./g. is the true M.E. value of the wheat; 8.5 kcal. represents the sum of the metabolic fecal and endogenous urinary energy losses; and X is the weight of wheat consumed (g.). A supplementary observation was that the metabolic fecal and endogenous nitrogen excretion of the roosters was 144 mg./kg./24 hr. In the second experiment corn oil was placed in the crops of starved roosters and the energy voided as excreta in 24 hr. was measured. The true M.E. value of the corn oil was 9.40 kcal./g. but the apparent value varied with intake. It is therefore concluded that the original hypothesis is correct. The findings of these experiments may explain some of the reported variations in M.E. data. A new approach to the assay for M.E. is proposed.
FEED INTAKE AND METABOLIZABLE ENERGY
Samples of ground wheat and excreta were assayed for gross energy in a Parr adiabatic bomb calorimeter fitted with a digital thermometer. When sufficient excreta remained after the energy measurements it was assayed for nitrogen using the method of Kjeldahl (A.O.A.C, 1965). Statistical treatment of the data is described later. Experiment 2. The procedures were similar to those of the first experiment but the source of dietary energy was corn oil which was placed directly into the crop from a pipette. This procedure ensured that a known amount of feed reached the crop at a specific time and avoided the possible criticism of the first experiment that the time and rate of feed intake differed between birds. The experiment was of a randomized block design with 10 levels of corn oil and 4 replications. A total of 40 birds, drawn from the same population as those of experiment 1, were used. The volume of corn oil administered ranged from about 1 to 10 ml. per bird. The weights of corn oil delivered by the pipettes were measured in the laboratory and were found to range from 0.62 to 8.41 g. per bird.
At the time of the second weighing and excreta collection it appeared that several birds had regurgitated oil. This was confirmed by the high gross energy levels of their excreta. Data from birds suspected of regurgitation were discarded. A total of 32 observations was obtained. RESULTS Experiment 1. The weight of air dry excreta (Y) voided by the roosters increased in a linear manner as the wheat consumption (X) increased. Statistical analysis revealed a correlation coefficient of 0.983 at 46 degrees of freedom and a regression equation having the form: Y = 2.72+ 0.176 X
(1)
This equation indicates that birds which consumed no wheat voided 2.72 g. of air dry excreta in the 24 hr. experimental period. For each gram of wheat consumed an additional 0.176 g. of excreta was voided. The distribution of the data around the regression line is displayed in Figure 1. There was a linear relationship between the gross energy (kcal.) voided as excreta (Y e ) and the weight of wheat consumed. The two variables had a correlation coefficient of 0.991 at 46 degrees of freedom while the regression equation had the form: Y e = 8.5+ 0.709 X
(2)
The equation indicates that under the conditions of the experiment the average bird suffered a combined F E m + UE e loss of 8.5 kcal./24 hours. For each gram of wheat consumed an additional 0.709 kcal. were voided as excreta. The distribution of the data around the regression line is displayed in Figure 2. Deviations from regression did not appear to be associated with either body weight or body weight change. It is probable
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excreta. Each cage was fitted with an individual feeder and water nipple. Forty-eight birds were starved for 18 hr. to ensure complete passage of previously consumed feed. The birds were individually weighed to within 10 g. and offered various amounts of whole wheat (cultivar Selkirk). Feeders were removed at intervals ranging from 1.5 to 7.5 hr., to encourage variable wheat intakes, and the weights of wheat consumed were recorded. Twenty-four hours after the start of the experiment the birds were again weighed and the excreta which they had voided during the 24 hr. period was collected quantitatively. The excreta was frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and ground to pass through a 20-mesh sieve.
1991
1992
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I I 40 60 WHEAT INTAKE (g.l
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that the methods of excreta collection, processing and analysis lacked the sensitivity to detect differences in excreta energy associated with these variables. The correlation coefficient between the gross energy excreted per kg. of mean body weight and the amount of wheat consumed was 0.976 at 46 degrees of freedom. The apparent M.E. value of a diet may be defined as: (GE d x X) - Ye
(3)
.A.
where GE d is the gross (kcal./g.) and X is the consumed. The GE d of was 3.88 kcal./g. Using
energy of the weight of diet the wheat, as this value and
I 40
I 60
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L 100
WHEAT INTAKE (g.)
FIG. 1. The effect of wheat consumption on the amount of air dry excreta voided.
M.E. (kcal./g.) =
-J 20
diet (g.) fed, Ye,
FIG. 2. The relationship between wheat consumption and the gross energy voided as excreta.
as defined in equation 2, it is possible to simplify equation 3:
M.E. kcal./g.) =
3.17 X - 8 . 5 X
(4)
The equation indicates that true M.E. value of the wheat was 3.17 kcal./g. but the apparent M.E. value was lower. The relationship between apparent M.E. values and wheat consumption is shown in Figure 3. The relationship appears to be a hyperbolic curve with the apparent M.E. value approaching the true M.E. value at high levels of intake and becoming negative at low levels of intake. Data for only 35 birds are plotted in Figure 3 because data from the remaining 13 yielded negative M.E. values. These results are in
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 12, 2014
I
I. R.
FEED INTAKE AND METABOLIZABLE ENERGY
1993
excreta (Y n ) and the weight of nitrogen consumed (X n ). Regression analysis revealed a correlation coefficient of 0.917 at 30 degrees of freedom while the regression equation had the form: Y = 0.375 + 0.602 X„
40
60
80
100
WHEAT INTAKE lg.)
FIG. 3. The effect of level of intake on the apparent M.E. value of wheat.
general agreement with those calculated by Guillaume and Summers (1970) and lead to the conclusion that in this experiment the apparent M.E. value of wheat was affected by the level of intake. The mean bird weight (BW) during the experiment was 2.52 kg., therefore the combined F E m + U E e loss, calculated from equation 2, was 3.37 kcal./kg. BW/24 hr.; this is substantially less than the value of 5.2 kcal. estimated by Guillaume and Summers (1970). The value of 3.37 kcal./kg. was obtained by regression analysis of data from 48 individual birds; however, 35 of the birds had consumed some wheat. When data from 13 birds which consumed no wheat were pooled a mean value of 3.88 kcal./kg. BW/24 hr. was obtained. Nitrogen excretion values were obtained for 32 birds. There was a linear relationship between the gross nitrogen (g.) voided as
The equation indicates that birds receiving no dietary nitrogen had a mean nitrogen excretion of 375 mg./day. The mean body weight of the 32 birds was 2.6 kg.; therefore, the total of metabolic fecal and endogenous urinary nitrogen excretion was 144 mg./kg. BW/day. This is identical to the value obtained by Ackerson et al. (1926) with R.I.R. hens. The equation further indicates that for each gram of wheat nitrogen consumed 602 mg. were excreted; consequently, the nitrogen retention was about 40 percent. It is possible that the procedure for measuring nitrogen retention could be developed to provide a relatively rapid bioassay for protein quality. The distribution of observed values about the regression line is shown in Figure 4. Experiment 2. The weight of air dry excreta (Y) voided by the roosters did not appear to be affected by the amount of corn oil (X) administered, for although regression analysis of the data yielded the following equation: Y = 3.73 - 0.075 X
(6)
a t-test indicated that the regression coefficient was not different from zero (P < 0.05) therefore X and its regression line may be discarded; the best estimate of Y becomes its mean and equation 6 may be rewritten as: Y = 3.43
(7)
This equation indicates that the birds voided 3.43 g. of air dry excreta in a 24 hr. period
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20
(5)
1994
I . R . SlBBALD
irrespective of the amount of corn oil consumed within the range of 0.62 to 8.41 grams. The distribution of the observed data around the regression line is displayed in Figure 5. The gross energy voided as excreta (Y e ) also appeared to remain constant irrespective of the amount of corn oil administered. Regression analysis yielded the following equation: (8)
Y = 11.19
(9)
This equation indicates that under the conditions of the experiment the average bird suffered a combined F E m + U E e loss of 11.19 kcal./24 hours. The administration of
1.5
1.0 LU
CC O X
• •_
LU
z
• •.
LU
O tr
0.5
Y p = 0.375 + 0.602X n r = 0.917at30D.F.
0.5
1.0
1.5
WHEAT NITROGEN INTAKE (g.) FIG. 4. The relationship between nitrogen excretion and wheat nitrogen intake.
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Y , = 10.98 + 0.054 X
Again the regression coefficient was not different from zero (P < 0.05) and the best estimate of Y e becomes its mean. The equation may be rewritten as:
1995
FEED INTAKE AND METABOLIZABLE ENERGY
ior
M.E. (kcal./g.)
9.40 X - 11.19 X
cc u X
(10)
UI
>-
cc o cc
< I
a
10'
True M.E. value 9.40 kcal./g.
CORN OIL INTAKE (g.)
FIG. 5. The effect of corn oil consumption on the amount of air dry excreta voided. up to 8.41 g. of corn oil per bird had no noticeable effect upon the amount of energy voided as excreta. The distribution of observed values around the regression line is displayed in Figure 6. The gross energy value of the corn oil was 9.40 kcal./gram. By substituting this value and Ye, as defined in equation 9, in equation 3 the following equation is obtained:
( - 2 0 -cc O X
Y
1
o °|-
• I.
e = 11 19
t
, •
. J . •
•
>-
o cc 1.
10
C/3
V)
O
CC
CORN OIL INTAKE (g.)
FIG. 6. The relationship between corn oil consumption and the gross energy voided as excreta.
CORN OIL INTAKE (g.)
FIG. 7. The effect of level of intake on the apparent M.E. value of corn oil.
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 12, 2014
The equation indicates that the true M.E. value of the corn oil was 9.40 kcal./g. but that the apparent M.E. value was lower. The relationship between apparent M.E. values and corn oil intake is shown in Figure 7. Data are plotted for only 27 birds because the remaining 5 birds yielded negative M.E. values.
Y = 3.43
1996
I. R. SlBBALD
The mean bird weight during the experiment was 2.38 kg. therefore the combined F E m + U E e loss, calculated from equation 9, was 4.70 kcal./kg. BW/24 hr.; this is intermediate between the value obtained in experiment 1 and that estimated by Guillaume and Summers (1970). There is no apparent reason for the difference between the two experiments.
The results of experiment 1 clearly demonstrate that the apparent M.E. value of wheat was affected by the level of intake. The results of experiment 2, which covered a narrower range of energy intakes, provide additional proof that the level of feed consumption is important. The reason is that the combined metabolic and endogenous losses are charged against the energy input. The combined F E m + U E e losses may exceed the energy input at low levels of feed consumption thus yielding negative apparent M.E. values. At high levels of feed intake the F E m + U E e losses have only a small effect on the apparent M.E. value. If the maintenance M.E. requirement of the adult rooster is 117 kcal./kg. BW/day (Guillaume and Summers, 1970) then the average bird of experiment 1, which weighed 2.52 kg., required 295 kcal. of M.E./day. The true M.E. value of the wheat was 3.17 kcal./g. therefore the maintenance requirement of the average bird should be met by 93 g. of wheat. When an intake of 93 g. is substituted in equation 4 the apparent M.E. value of the wheat is estimated to be 3.08 kcal./gram This is 97% of the true M.E. value. It is of interest that Anderson et al. (1958) working with chicks found that the apparent M.E. value of glucose was equivalent to 97% of its gross energy value. Their apparent M.E. value of 3.64 kcal./g. of dry matter has been widely used as a constant in M.E. bioassays. If the true M.E. value
The findings of the present experiments suggest that the true M.E. values of diets and feed ingredients can be measured by feeding graded levels to starved birds and measuring the energy voided. The biological phase of the assay is only 24 hr.; a significant reduction in time compared to current bioassays. An additional advantage is that the amount of sample required is much less than in conventional assays. Development work will be required before the assay can be widely accepted but it offers potential advantages not only in terms of time and cost but also in terms of more valid data. ACKNOWLEDGEMENTS The author wishes to thank R. W. Allen and A. M. Richardson for their able technical assistance and K. Price of the Statistical Research Service of Agriculture Canada for his useful suggestions. The nitrogen assays were conducted by the Chemical and Biological Research Institute of Agriculture Canada. REFERENCES Ackerson, L. W., M. J. Blish and E. F. Mussehl, 1926. The endogenous nitrogen of hens as affected by molting. Poultry Sci. 5: 153-161.
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DISCUSSION
of glucose, which is probably about 3.75 kcal./g., had been used many of the published M.E. values of ingredients would be appreciably different. There is evidence in the literature that apparent M.E. values measured with birds may differ with species (Slinger et al., 1964; Bayley et al., 1968; Fisher and Shannon, 1973), strains (Slinger et al., 1964; Foster, 1968; March and Biely, 1971) and age (Bayley etal., 1968;Zelenka, 1968,Lodhi etal., 1969). The differences are generally small and it is possible that they are attributable in part to variations in the F E m + U E e losses relative to intake. If this is correct then there is reason to measure true rather than apparent M.E. values.
FEED INTAKE AND METABOLIZABLE ENERGY
Lockhart, W. C , R. L. Bryant and D. W. Bolin, 1966. The effects of B-vitamin deficiencies on the efficiency of metabolizable energy and protein utilization. Poultry Sci. 45: 939-945. Lodhi, G. N., R. Renner and D. R. Clandinin, 1969. Studies on the metabolizable energy of rapeseed meal for growing chickens and laying hens. Poultry Sci. 48: 964-970. March, B. E., and J. Biely, 1971. Factors affecting the response of chicks to diets of different protein value: breed and age. Poultry Sci. 50: 1036-1040. Potter, L. M., L. D. Matterson, A. W. Arnold, W. J. Pudelkiewicz and E. P. Singsen, 1960. Studies in evaluating energy content of feeds for the chick. 1. The evaluation of the metabolizable energy and productive energy of alpha-cellulose. Poultry Sci. 39: 1166-1178. Slinger, S. J., I. R. Sibbald and W. F. Pepper, 1964. The relative abilities of two breeds of chickens and two varieties of turkeys to metabolize dietary energy and dietary nitrogen. Poultry Sci. 43: 329-333. Zelenka, J., 1968. Influence of the age of chicken on the metabolizable energy values of poultry diets. Br. Poultry Sci. 9: 135-142.
NEWS AND NOTES (Continued from page 1989)
Department of Agricultural Chemistry, Macdonald College of McGill University, in May. Dr. Common came to Canada in 1947 and retired as Chairman of the Department in 1972. He continued teaching until recently. MERCK NOTES A total of $52,200 in grants to further animal health education was awarded by The Merck Company Foundation in 1974. The recipients include: The College of Veterinary Medicine and Biomedical Science, Colorado State University, Fort Collins, Colorado—$5,000 for the development of diagnostic techniques in parasitology; Department of Poultry Science, Cornell University, Ithaca, New York—$5,000 for support of poultry science education; School of Veterinary Medicine, Purdue University, West Lafayette, Indiana—$5,000 for innovative in-
struction in differential diagnosis of diseases of large animals; College of Veterinary Medicine, University of Georgia, Athens, Georgia—$7,200 final payment of a three-year, $21,600 grant for development of a competency-based veterinary medical curriculum; Department of Veterinary Science, University of Idaho, Moscow, Idaho—$5,000 for development of self-learning programs in veterinary science at the Northwest Regional Instruction Center operated jointly with Washington State University; College of Veterinary Medicine, Tuskegee Institute, Tuskegee, Alabama—$5,000 final payment of a threeyear, $15,000 grant. The Foundation also gave $10,000 to the American Association of Veterinary Medical Colleges, Chicago, Illinois, as part of a $22,500 grant over three years. The Association will establish a central office with a full-time staff to better serve veterinary medical colleges.
(Continued on page 2006)
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Anderson, D. L., F. W. Hill and R. Renner, 1958. Studies of the metabolizable and productive energy of glucose for the growing chick. J. Nutrition, 65: 561-574. Association of Official Agricultural Chemists, 1965. Official Methods of Analysis, 10th ed. Washington, D.C. Bayley, H. S., J. D. Summers and S. J. Slinger, 1968. Effect of heat treatment on the metabolizable energy value of wheat germ meal and other wheat milling by-products. Cereal Chem. 45: 557-563. Fisher, C , andD. W. F. Shannon, 1973. Metabolizable energy determinations using chicks and turkeys. Br. Poultry Sci. 14: 609-613. Foster, W. H., 1968. The response of Brown Leghorn and Light Sussex laying flocks to dilution of the diet. Record Agric. Res. 17: 13-17. Guillaume, J., and J. D. Summers, 1970. Maintenance energy requirement of the rooster and influence of plane of nutrition on metabolizable energy. Can. J. Anim. Sci. 50: 363-369. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutrition, 64: 587-604.
1997
POULTRY SCIENCE 54; 1990-1997, 1975
INTRODUCTION
A
PPARENT dietary metabolizable energy (M.E.) values should vary with the level of feed intake because, under standardized conditions, the excretion of metabolic fecal energy (FE m ) plus endogenous urinary energy (UE e ) is constant. When feed energy intake is high the energy loss as F E m + U E e is relatively small but as the energy intake is reduced these energy losses become increasingly significant and should depress the apparent M.E. value. This hypothesis has been explained by Guillaume and Summers (1970) using theoretical values and while it is logical it does not appear to have been proven in poultry with experimental data. Hill and Anderson (1958) reduced the feed consumption of chicks to as little as 30% of ad libitum and found no effect of level of feed intake on dietary M.E. values. Potter et al. (1960) also restricted the feed consumption of chicks and found that the M.E. per gram of diet increased with the degree of
Contribution No. 566.
restriction. This finding tends to contradict that of Hill and Anderson (1958) and is the opposite of what is expected if the initial hypothesis is correct. Lockhart et al. (1966) found that deficiencies of B-vitamins depressed observed M.E. values. The changes may have been associated with reduced feed intakes but this cannot be proven. The experiments described in this paper were designed to test the hypothesis that apparent dietary M.E. values decrease when the energy consumption is reduced, all other conditions being constant. Such information is important to those concerned with the development of M.E. bioassays and with the measurement of the M.E. values of diets and ingredients.
MATERIALS AND METHODS Experiment 1. Adult S.C.W.L. roosters of the Kentville Control Strain were housed in individual wire cages in a windowless room where they received 12 hr. of light each day. Alternate cages were left vacant to minimize the possibility of cross contamination of
1990
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 12, 2014
ABSTRACT Two experiments were made with S.C.W.L. roosters to test the hypothesis that the apparent M.E. value of a feedingstuff is affected by the level of intake. In the first experiment the birds were starved for 18 hr. and then fed varying amounts of whole wheat. Excreta voided during the 24 hr. experimental period was collected quantitatively and assayed for gross energy. Energy voided as excreta increased in a linear manner as the intake of wheat increased. The apparent M.E. value also varied with wheat consumption according to the equation M.E. (kcal./g.) = 3.17X - 8.5/X where: 3.17 kcal./g. is the true M.E. value of the wheat; 8.5 kcal. represents the sum of the metabolic fecal and endogenous urinary energy losses; and X is the weight of wheat consumed (g.). A supplementary observation was that the metabolic fecal and endogenous nitrogen excretion of the roosters was 144 mg./kg./24 hr. In the second experiment corn oil was placed in the crops of starved roosters and the energy voided as excreta in 24 hr. was measured. The true M.E. value of the corn oil was 9.40 kcal./g. but the apparent value varied with intake. It is therefore concluded that the original hypothesis is correct. The findings of these experiments may explain some of the reported variations in M.E. data. A new approach to the assay for M.E. is proposed.
FEED INTAKE AND METABOLIZABLE ENERGY
Samples of ground wheat and excreta were assayed for gross energy in a Parr adiabatic bomb calorimeter fitted with a digital thermometer. When sufficient excreta remained after the energy measurements it was assayed for nitrogen using the method of Kjeldahl (A.O.A.C, 1965). Statistical treatment of the data is described later. Experiment 2. The procedures were similar to those of the first experiment but the source of dietary energy was corn oil which was placed directly into the crop from a pipette. This procedure ensured that a known amount of feed reached the crop at a specific time and avoided the possible criticism of the first experiment that the time and rate of feed intake differed between birds. The experiment was of a randomized block design with 10 levels of corn oil and 4 replications. A total of 40 birds, drawn from the same population as those of experiment 1, were used. The volume of corn oil administered ranged from about 1 to 10 ml. per bird. The weights of corn oil delivered by the pipettes were measured in the laboratory and were found to range from 0.62 to 8.41 g. per bird.
At the time of the second weighing and excreta collection it appeared that several birds had regurgitated oil. This was confirmed by the high gross energy levels of their excreta. Data from birds suspected of regurgitation were discarded. A total of 32 observations was obtained. RESULTS Experiment 1. The weight of air dry excreta (Y) voided by the roosters increased in a linear manner as the wheat consumption (X) increased. Statistical analysis revealed a correlation coefficient of 0.983 at 46 degrees of freedom and a regression equation having the form: Y = 2.72+ 0.176 X
(1)
This equation indicates that birds which consumed no wheat voided 2.72 g. of air dry excreta in the 24 hr. experimental period. For each gram of wheat consumed an additional 0.176 g. of excreta was voided. The distribution of the data around the regression line is displayed in Figure 1. There was a linear relationship between the gross energy (kcal.) voided as excreta (Y e ) and the weight of wheat consumed. The two variables had a correlation coefficient of 0.991 at 46 degrees of freedom while the regression equation had the form: Y e = 8.5+ 0.709 X
(2)
The equation indicates that under the conditions of the experiment the average bird suffered a combined F E m + UE e loss of 8.5 kcal./24 hours. For each gram of wheat consumed an additional 0.709 kcal. were voided as excreta. The distribution of the data around the regression line is displayed in Figure 2. Deviations from regression did not appear to be associated with either body weight or body weight change. It is probable
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 12, 2014
excreta. Each cage was fitted with an individual feeder and water nipple. Forty-eight birds were starved for 18 hr. to ensure complete passage of previously consumed feed. The birds were individually weighed to within 10 g. and offered various amounts of whole wheat (cultivar Selkirk). Feeders were removed at intervals ranging from 1.5 to 7.5 hr., to encourage variable wheat intakes, and the weights of wheat consumed were recorded. Twenty-four hours after the start of the experiment the birds were again weighed and the excreta which they had voided during the 24 hr. period was collected quantitatively. The excreta was frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and ground to pass through a 20-mesh sieve.
1991
1992
1 20
I I 40 60 WHEAT INTAKE (g.l
I 80
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I 100
that the methods of excreta collection, processing and analysis lacked the sensitivity to detect differences in excreta energy associated with these variables. The correlation coefficient between the gross energy excreted per kg. of mean body weight and the amount of wheat consumed was 0.976 at 46 degrees of freedom. The apparent M.E. value of a diet may be defined as: (GE d x X) - Ye
(3)
.A.
where GE d is the gross (kcal./g.) and X is the consumed. The GE d of was 3.88 kcal./g. Using
energy of the weight of diet the wheat, as this value and
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L 100
WHEAT INTAKE (g.)
FIG. 1. The effect of wheat consumption on the amount of air dry excreta voided.
M.E. (kcal./g.) =
-J 20
diet (g.) fed, Ye,
FIG. 2. The relationship between wheat consumption and the gross energy voided as excreta.
as defined in equation 2, it is possible to simplify equation 3:
M.E. kcal./g.) =
3.17 X - 8 . 5 X
(4)
The equation indicates that true M.E. value of the wheat was 3.17 kcal./g. but the apparent M.E. value was lower. The relationship between apparent M.E. values and wheat consumption is shown in Figure 3. The relationship appears to be a hyperbolic curve with the apparent M.E. value approaching the true M.E. value at high levels of intake and becoming negative at low levels of intake. Data for only 35 birds are plotted in Figure 3 because data from the remaining 13 yielded negative M.E. values. These results are in
Downloaded from http://ps.oxfordjournals.org/ at Columbia University Libraries on December 12, 2014
I
I. R.
FEED INTAKE AND METABOLIZABLE ENERGY
1993
excreta (Y n ) and the weight of nitrogen consumed (X n ). Regression analysis revealed a correlation coefficient of 0.917 at 30 degrees of freedom while the regression equation had the form: Y = 0.375 + 0.602 X„
40
60
80
100
WHEAT INTAKE lg.)
FIG. 3. The effect of level of intake on the apparent M.E. value of wheat.
general agreement with those calculated by Guillaume and Summers (1970) and lead to the conclusion that in this experiment the apparent M.E. value of wheat was affected by the level of intake. The mean bird weight (BW) during the experiment was 2.52 kg., therefore the combined F E m + U E e loss, calculated from equation 2, was 3.37 kcal./kg. BW/24 hr.; this is substantially less than the value of 5.2 kcal. estimated by Guillaume and Summers (1970). The value of 3.37 kcal./kg. was obtained by regression analysis of data from 48 individual birds; however, 35 of the birds had consumed some wheat. When data from 13 birds which consumed no wheat were pooled a mean value of 3.88 kcal./kg. BW/24 hr. was obtained. Nitrogen excretion values were obtained for 32 birds. There was a linear relationship between the gross nitrogen (g.) voided as
The equation indicates that birds receiving no dietary nitrogen had a mean nitrogen excretion of 375 mg./day. The mean body weight of the 32 birds was 2.6 kg.; therefore, the total of metabolic fecal and endogenous urinary nitrogen excretion was 144 mg./kg. BW/day. This is identical to the value obtained by Ackerson et al. (1926) with R.I.R. hens. The equation further indicates that for each gram of wheat nitrogen consumed 602 mg. were excreted; consequently, the nitrogen retention was about 40 percent. It is possible that the procedure for measuring nitrogen retention could be developed to provide a relatively rapid bioassay for protein quality. The distribution of observed values about the regression line is shown in Figure 4. Experiment 2. The weight of air dry excreta (Y) voided by the roosters did not appear to be affected by the amount of corn oil (X) administered, for although regression analysis of the data yielded the following equation: Y = 3.73 - 0.075 X
(6)
a t-test indicated that the regression coefficient was not different from zero (P < 0.05) therefore X and its regression line may be discarded; the best estimate of Y becomes its mean and equation 6 may be rewritten as: Y = 3.43
(7)
This equation indicates that the birds voided 3.43 g. of air dry excreta in a 24 hr. period
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20
(5)
1994
I . R . SlBBALD
irrespective of the amount of corn oil consumed within the range of 0.62 to 8.41 grams. The distribution of the observed data around the regression line is displayed in Figure 5. The gross energy voided as excreta (Y e ) also appeared to remain constant irrespective of the amount of corn oil administered. Regression analysis yielded the following equation: (8)
Y = 11.19
(9)
This equation indicates that under the conditions of the experiment the average bird suffered a combined F E m + U E e loss of 11.19 kcal./24 hours. The administration of
1.5
1.0 LU
CC O X
• •_
LU
z
• •.
LU
O tr
0.5
Y p = 0.375 + 0.602X n r = 0.917at30D.F.
0.5
1.0
1.5
WHEAT NITROGEN INTAKE (g.) FIG. 4. The relationship between nitrogen excretion and wheat nitrogen intake.
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Y , = 10.98 + 0.054 X
Again the regression coefficient was not different from zero (P < 0.05) and the best estimate of Y e becomes its mean. The equation may be rewritten as:
1995
FEED INTAKE AND METABOLIZABLE ENERGY
ior
M.E. (kcal./g.)
9.40 X - 11.19 X
cc u X
(10)
UI
>-
cc o cc
< I
a
10'
True M.E. value 9.40 kcal./g.
CORN OIL INTAKE (g.)
FIG. 5. The effect of corn oil consumption on the amount of air dry excreta voided. up to 8.41 g. of corn oil per bird had no noticeable effect upon the amount of energy voided as excreta. The distribution of observed values around the regression line is displayed in Figure 6. The gross energy value of the corn oil was 9.40 kcal./gram. By substituting this value and Ye, as defined in equation 9, in equation 3 the following equation is obtained:
( - 2 0 -cc O X
Y
1
o °|-
• I.
e = 11 19
t
, •
. J . •
•
>-
o cc 1.
10
C/3
V)
O
CC
CORN OIL INTAKE (g.)
FIG. 6. The relationship between corn oil consumption and the gross energy voided as excreta.
CORN OIL INTAKE (g.)
FIG. 7. The effect of level of intake on the apparent M.E. value of corn oil.
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The equation indicates that the true M.E. value of the corn oil was 9.40 kcal./g. but that the apparent M.E. value was lower. The relationship between apparent M.E. values and corn oil intake is shown in Figure 7. Data are plotted for only 27 birds because the remaining 5 birds yielded negative M.E. values.
Y = 3.43
1996
I. R. SlBBALD
The mean bird weight during the experiment was 2.38 kg. therefore the combined F E m + U E e loss, calculated from equation 9, was 4.70 kcal./kg. BW/24 hr.; this is intermediate between the value obtained in experiment 1 and that estimated by Guillaume and Summers (1970). There is no apparent reason for the difference between the two experiments.
The results of experiment 1 clearly demonstrate that the apparent M.E. value of wheat was affected by the level of intake. The results of experiment 2, which covered a narrower range of energy intakes, provide additional proof that the level of feed consumption is important. The reason is that the combined metabolic and endogenous losses are charged against the energy input. The combined F E m + U E e losses may exceed the energy input at low levels of feed consumption thus yielding negative apparent M.E. values. At high levels of feed intake the F E m + U E e losses have only a small effect on the apparent M.E. value. If the maintenance M.E. requirement of the adult rooster is 117 kcal./kg. BW/day (Guillaume and Summers, 1970) then the average bird of experiment 1, which weighed 2.52 kg., required 295 kcal. of M.E./day. The true M.E. value of the wheat was 3.17 kcal./g. therefore the maintenance requirement of the average bird should be met by 93 g. of wheat. When an intake of 93 g. is substituted in equation 4 the apparent M.E. value of the wheat is estimated to be 3.08 kcal./gram This is 97% of the true M.E. value. It is of interest that Anderson et al. (1958) working with chicks found that the apparent M.E. value of glucose was equivalent to 97% of its gross energy value. Their apparent M.E. value of 3.64 kcal./g. of dry matter has been widely used as a constant in M.E. bioassays. If the true M.E. value
The findings of the present experiments suggest that the true M.E. values of diets and feed ingredients can be measured by feeding graded levels to starved birds and measuring the energy voided. The biological phase of the assay is only 24 hr.; a significant reduction in time compared to current bioassays. An additional advantage is that the amount of sample required is much less than in conventional assays. Development work will be required before the assay can be widely accepted but it offers potential advantages not only in terms of time and cost but also in terms of more valid data. ACKNOWLEDGEMENTS The author wishes to thank R. W. Allen and A. M. Richardson for their able technical assistance and K. Price of the Statistical Research Service of Agriculture Canada for his useful suggestions. The nitrogen assays were conducted by the Chemical and Biological Research Institute of Agriculture Canada. REFERENCES Ackerson, L. W., M. J. Blish and E. F. Mussehl, 1926. The endogenous nitrogen of hens as affected by molting. Poultry Sci. 5: 153-161.
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DISCUSSION
of glucose, which is probably about 3.75 kcal./g., had been used many of the published M.E. values of ingredients would be appreciably different. There is evidence in the literature that apparent M.E. values measured with birds may differ with species (Slinger et al., 1964; Bayley et al., 1968; Fisher and Shannon, 1973), strains (Slinger et al., 1964; Foster, 1968; March and Biely, 1971) and age (Bayley etal., 1968;Zelenka, 1968,Lodhi etal., 1969). The differences are generally small and it is possible that they are attributable in part to variations in the F E m + U E e losses relative to intake. If this is correct then there is reason to measure true rather than apparent M.E. values.
FEED INTAKE AND METABOLIZABLE ENERGY
Lockhart, W. C , R. L. Bryant and D. W. Bolin, 1966. The effects of B-vitamin deficiencies on the efficiency of metabolizable energy and protein utilization. Poultry Sci. 45: 939-945. Lodhi, G. N., R. Renner and D. R. Clandinin, 1969. Studies on the metabolizable energy of rapeseed meal for growing chickens and laying hens. Poultry Sci. 48: 964-970. March, B. E., and J. Biely, 1971. Factors affecting the response of chicks to diets of different protein value: breed and age. Poultry Sci. 50: 1036-1040. Potter, L. M., L. D. Matterson, A. W. Arnold, W. J. Pudelkiewicz and E. P. Singsen, 1960. Studies in evaluating energy content of feeds for the chick. 1. The evaluation of the metabolizable energy and productive energy of alpha-cellulose. Poultry Sci. 39: 1166-1178. Slinger, S. J., I. R. Sibbald and W. F. Pepper, 1964. The relative abilities of two breeds of chickens and two varieties of turkeys to metabolize dietary energy and dietary nitrogen. Poultry Sci. 43: 329-333. Zelenka, J., 1968. Influence of the age of chicken on the metabolizable energy values of poultry diets. Br. Poultry Sci. 9: 135-142.
NEWS AND NOTES (Continued from page 1989)
Department of Agricultural Chemistry, Macdonald College of McGill University, in May. Dr. Common came to Canada in 1947 and retired as Chairman of the Department in 1972. He continued teaching until recently. MERCK NOTES A total of $52,200 in grants to further animal health education was awarded by The Merck Company Foundation in 1974. The recipients include: The College of Veterinary Medicine and Biomedical Science, Colorado State University, Fort Collins, Colorado—$5,000 for the development of diagnostic techniques in parasitology; Department of Poultry Science, Cornell University, Ithaca, New York—$5,000 for support of poultry science education; School of Veterinary Medicine, Purdue University, West Lafayette, Indiana—$5,000 for innovative in-
struction in differential diagnosis of diseases of large animals; College of Veterinary Medicine, University of Georgia, Athens, Georgia—$7,200 final payment of a three-year, $21,600 grant for development of a competency-based veterinary medical curriculum; Department of Veterinary Science, University of Idaho, Moscow, Idaho—$5,000 for development of self-learning programs in veterinary science at the Northwest Regional Instruction Center operated jointly with Washington State University; College of Veterinary Medicine, Tuskegee Institute, Tuskegee, Alabama—$5,000 final payment of a threeyear, $15,000 grant. The Foundation also gave $10,000 to the American Association of Veterinary Medical Colleges, Chicago, Illinois, as part of a $22,500 grant over three years. The Association will establish a central office with a full-time staff to better serve veterinary medical colleges.
(Continued on page 2006)
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Anderson, D. L., F. W. Hill and R. Renner, 1958. Studies of the metabolizable and productive energy of glucose for the growing chick. J. Nutrition, 65: 561-574. Association of Official Agricultural Chemists, 1965. Official Methods of Analysis, 10th ed. Washington, D.C. Bayley, H. S., J. D. Summers and S. J. Slinger, 1968. Effect of heat treatment on the metabolizable energy value of wheat germ meal and other wheat milling by-products. Cereal Chem. 45: 557-563. Fisher, C , andD. W. F. Shannon, 1973. Metabolizable energy determinations using chicks and turkeys. Br. Poultry Sci. 14: 609-613. Foster, W. H., 1968. The response of Brown Leghorn and Light Sussex laying flocks to dilution of the diet. Record Agric. Res. 17: 13-17. Guillaume, J., and J. D. Summers, 1970. Maintenance energy requirement of the rooster and influence of plane of nutrition on metabolizable energy. Can. J. Anim. Sci. 50: 363-369. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutrition, 64: 587-604.
1997