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Effects of Energy Restriction on Laying Hens1
GONADAL HORMONES AND PHOSPHORUS metabolism of pullets. X. The effects of gonadal hormones on retention and turnover of calcium by the skeleton. Can. J. Agric. Sci. 33: 216-224. Kjerulf-Jensen, K., 1941. Excretion of phosphorus by the bowel. Acta. Physiol. Scand. 3: 1-27. Kleiber, M., A. H. Smith, N. B. Ralston and A. L. Black, 1951. Radiophosphorus P32 as tracer for measuring endogenous phosphorus in cow faeces.
353
J. Nutrition, 35: 253:263. Lofgreen, G. P., and M. Kleiber, 1953. The availability of phosphorus in alfalfa hay. J. Animal Sci. 12: 366-371. Visek, W. J., R. A. Monroe, E. W. Swanson and C. L. Comar, 1953. Determination of endogenous faecal calcium in cattle by a simple isotope dilution method. J. Nutrition, 50: 23-33.
W. E. DONALDSON AND R. I. MILLAR 2 Poultry Science Department, University of Rhode Island, Kingston, Rhode Island (Received for publication May 10. 1961)
INTRODUCTION
B
ECAUSE high feed consumption, obesity and relatively low egg production are characteristic of heavy meattype laying hens, interest has developed in attempting to improve the performance of this type of hen by restriction of feed intake. Numerous reports dealing with the effects of feed restriction during the growing period on subsequent egg production have been published, but there are few reports available on restriction during the laying period. Heywang (1940) observed drastic reductions in egg production but no effect on body weight or egg size by restricting the feed intake of Leghorn hens to 87J and 75% of ad libitum intake. Singsen et al. (1959) used body weight, egg production and environmental temperature to predict feed consumption of White Rock laying hens. Controlled feeding (based on predicted consumption) of high and low energy rations was compared with ad libitum feeding of the same rations. Al1
Contribution No. 1025 of the Rhode Island Agricultural Experiment Station. 2 Present address: Beacon Milling Company, Cayuga, New York.
though intake of the high energy ration was only 84.3% of ad libitum, production was not affected. Production was reduced when the low energy ration was controlfed (77% of ad libitum) even though digestible nutrient intake was calculated to be the same as the intake of the birds control-fed the high energy rations. Combs et al. (1961) reported that restriction of energy intake of heavy-type hens to 81 and 87% of ad libitum intake did not affect egg production, Haugh unit scores or mortality. Reductions in body weight gain and rate of increase in egg size were observed with energy restriction. The purpose of the experiments reported herein was to determine the effects of energy restriction on productive traits of meat-type laying hens. PROCEDURE
Two experiments were conducted in each of which April hatched pullets were placed on experiment on the succeeding January 21st and continued for 36 weeks All birds were reared on an ad libitumieeding system. In experiment 1, 29 White Plymouth Rock pullets were randomly assigned to
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 4, 2015
Effects of Energy Restriction on Laying Hens 1
354
W.
E. D O N A L D S O N AND R. I.
TABLE 1.-—Rations used in energy restriction experiment Ingredients
Calculated analysis: Protein, % Productive energy, Cal./lb.s 1 Metabolizable energy, Cal./lb.
Restricted
66.4125 10.0000 4.0000 2.0000
52.0631 12.5000 5.0000 2.5000
10.0000
18.4500
3.0000 1.2500 1.5000 1.0000 0.5000 0.1000
3.7500 1.5625 1.8750 1.2500 0.6250 0.1250
0.0750
0.0938
0.0500 0.0125 0.0500 0.0500
0.0625 0.0156 0.062S 0.0650
16.18 943 1,337
20.21 859 1,259
1 Contains not less than 6% manganese, 2% iron, 0.2% copper,2 0.12% iodine, 0.02% cobalt and 26.5% calcium. Contains not less than (per lb.) 2 gm. riboflavin, 4 gm. calcium3 pantothenate, 9 gm. niacin and 10 gm. choline chloride. Values of Fraps (1946) were used. ' Values of Titus (1955, revised in 1957) were used.
each of 8 groups. Four groups were placed on each of the experimental rations shown in Table 1. The control ration was available ad libitum. Daily feed consumption was measured. The consumption figures were used to determine the intake for the next day of the birds fed the restricted ration. For each pound of control feed consumed, the restricted birds received approximately 0.8 pounds. The feeding of the restricted ration at 8 0 % of the control ration intake resulted in calculated energy intakes of 72.9% (productive energy) and 7 5 . 3 % (metabolizable energy) of control {ad libitum) while the calculated intake of all other nutrients was essentially 100% of control. Adjustments of daily feed allowances were made as mortality occurred so t h a t the relative differences in feed intake between the t r e a t m e n t s were constant on a per bird basis. In experiment 2, 25 pullets were randomly assigned to each of 6 groups. The pullets were the progeny of the females
used in experiment 1 and males of a synthetic broiler strain (predominantly W y a n d o t t e ) . Three groups were placed on each of the treatments from experiment 1. Weekly feed consumption was determined for the control {ad libitum) birds, a n d restricted birds were given daily feed allotments based on the consumption of the controls for the previous week ( 8 0 % of ad libitum). Each group was maintained in 1 2 ' X 1 2 ' floor pens equipped with 2 hanging cylinder feeders. Water and calcite grit were available to all groups ad libitum. All groups were trapnested 3 days per week and pen egg production was recorded for the remainder of the time. Individual body weights were obtained initially and at 6-week intervals thereafter until the conclusions of the tests. Hen-day egg production during the two weeks immediately preceding each experiment was 47 and 4 2 % in experiment 1 and 35 and 33% in experiment 2 for the ad libitum and restricted groups, respectively. In experiment 2, all eggs produced on one day each week were weighed b y groups. At the beginning of experiment 2, 16 eggs ranging in weight from 63 to 69 grams were obtained for gross energy analysis from 2 groups of birds (one on each treatment). The eggs with shell were autoclaved at 250°C. and 15 p.s.i. steam pressure for 10 minutes; ground individually in a Waring blendor with an equal weight of water; dried to constant weight (approximately 12 hours) at 9 5 ° C ; ground with mortar and pestle to pass a 20 mesh screen; and pelleted and burned in an oxygen bomb calorimeter. RESULTS AND DISCUSSION The egg production, feed conversion, egg weight and mortality d a t a from both experiments are shown in Table 2. Analyses of variance based on the 3-day trapnest
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 4, 2015
Ground yellow corn Standard wheat middlings Fish meal, menhaden, 60% protein Meat and bone scrap, 50% protein Soybean oil meal, solvent, 44% protein Dhy. alfalfa meal, 17% protein, 70,000 IU of vitamin A per lb. Dried corn distillers' solubles Ground limestone Dicalcium phosphate Iodized salt Trace mineral mix1 Dry vitamin A and Ds supplement, 10,000 10 of A and 1,500 ICU of D> per gm. Vitamin Bn supplement, 6 mg, per lb. Butylated hydroxytoluene Choline chloride, 25% mixture Vitamin supplement2
Level in ration, % Control
MILLAR
355
ENERGY RESTRICTION OF HENS TABLE 2.—Effect
Period
1
of energy restriction on egg production, feed conversion, egg weight and mortality
Hen -day production, %
d
A
Lbs. feed/dozen eggs
libitum
Restricted
Ad libitum
Restricted
1 2 3 4 S 6
45.4 60.8 58.8 55.4 46.8 31.0
37.1 48.8 46.2 55.0 48.2 33.0
8.74 7.34 7.63 8.49 9.25 13.99
8.43 6.80 7.76 7.24 7.15 10.00
All
49.8
44.7
8.79
7.73
1 2 3 4 5 6
74.3 67.9 63.3 60.7 54.2 35.9
67.5 59.3 55.4 53.5 44.6 28.0
5.97 6.46 6.92 7.06 7.75 12.45
4.98 5.99 6.27 6.33 7.24 12.21
All
59.8
51.7
7.27
6.58
Lbs. feed/lbs. eggs2 Ad libitum
Restricted
Egg weight, gm.•/egg
Mortality,
%
Ad libitum
Restricted
Ad libiium
Restricted
.— — —. — .— — —
— — .— — — — —
12.1
22.4
66.5 67.5 67.9 67.7 68.0 69.3
65.2 65.9 65.4 67.0 65.9 66.0
67.6
65.9
14.7
8.0
Experiment P
—. — .— — —. — —
Experiment 2* 3.39 2.89 3.62 3.43 3.85 3.62 3.94 3.57 4.31 4.15 6.79 6.99 4.07
3.77
1 Each period was 6 weeks in duration. The experiment began on January 21st and ended on September 28th. 2 No egg weights were obtained in experiment 1, therefore conversion expressed as pounds of feed per pound of eggs are given for experiment 2 only. 3 Each value represents the average of 4 groups of 29 birds each. 4 Each value represents the average of 3 groups of 25 birds each.
records reveal statistically significant (P = 0.01) decreases in egg production in the restricted groups in both experiments. The apparent interaction between treatments and periods in experiment 1 is not statistically significant (P = 0.05). The restricted hens consumed less feed per dozen eggs except during period 3 in experiment 1. The restricted hens in experiment 2 consumed less feed per pound of egg except during period 6. The egg weights of the restricted hens were significantly (P = 0.01) lower. Egg weight generally increased with age in the ad libitum groups but not in the restricted groups. There was no consistent effect of treatment on mortality in the two experiments. The body weight data from both experiments are shown in Table 3. Body weights were significantly lower (P = 0.01) in the
restricted groups. The general tendency in both experiments was for gradual weight increase in the ad libitum groups over the entire experimental period and for weight decreases in the restricted groups during the first two periods. The restricted groups regained much of the weight losses during the remaining periods. The data from both experiments demonstrate that restriction of energy intake of meat-type laying hens to approximately 75% of ad libitum reduces egg production. There is an indication in experiment 1 that during conditions of warmer environmental temperatures (periods 4, 5 and 6), energy restriction did not affect production (see Table 4 for mean environment temperatures). This apparent effect of an interaction of temperature (periods) with energy restriction on egg production was not statistically
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— — — — — — —
356
W. E. DONALDSON AND R. I. MILLAR
TABLE 3.—Effect Period 1
of energy restriction on body weight Average body weight, lbs. Ad libitum
Restricted
Experiment 1 6.99 6.64 6.35 6.53 6.78 6.83 6.87
7.00 7.05 7.02 7.06 7.26 7.27 7.10
Start 1 2 3 4 5 6
Experiment 7.17 7.30 7.29 7.54 7.64 7.77 7.69
2 7.09 6.88 6.49 6.60 6.60 6.24 6.80
1 Each period was six weeks in duration. The experiments began on January 21st and ended on September 28th.
significant (P = 0.05) and did not appear in experiment 2; therefore it must be concluded that energy intake approximating 75% of ad libitum is too severe a restriction under all conditions of temperature encountered in these experiments. These data are. in disagreement with those of Singsen et al. (1959) and Combs et al. (1961) who reported that energy restriction had no effect on production. However, the levels of energy restriction employed by both groups of workers cited (approximately 84% by Singsen et al. and 8 1 % by Combs et al.) were less than the levels used in these experiments. Thus, it would appear that the minimum energy requirement of heavy-breed laying hens is between 75 and 8 1 % of ad libitum intake. The depression of egg weights by energy restriction was consistent and is in agreement with the data of Combs et al. (1961). Singsen et al. (1959) did not observe a reduction in egg weight, probably due to less severe restriction. Lowered egg weight may reflect attempt by the hen to maintain reproductive capacity under condi-
The restricted hens exhibited better feed conversions when expressed both as pounds of feed per dozen eggs and pounds of feed per pound of eggs even though egg production was lower. This result was not wholly unexpected since the restricted TABLE 4.—Mean environmental temperature by periods Mean temperature, °F. l Period
Duration of period
1 2 3 4 5 6
Jan. 21-Mar. 2 Mar. 3-Apr. 13 Apr. 14-May 25 May 26-July 6 July 7-Aug. 17 Aug. 18-Sept. 28
Average
Experiment 1
Experiment 2
28.7 40.7 54.9 64.8 71.5 67.5
33.0 38.2 53.9 65.8 68.3 61.7
54.7
53.5
1 Temperature values are based on averages of daily minimum and maximum temperatures recorded at a weather station within 2 miles of the pens.
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Start 1 2 3 4 5 6
tions of restriction by allotting less nutrients to each egg. The body weight data demonstrate quite conclusively that the level of energy intake in the restricted groups was not high enough to maintain normal body weight at the relatively cold temperatures of periods one and two in both experiments. As the temperatures moderated during succeeding periods, there were indications that energy intake would have been sufficient to maintain weight since the hens in the restricted groups showed a trend toward regaining the earlier weight losses. Heywang (1940) reported that 75% restriction of feed intake did not reduce the body weight of White Leghorn hens in the relatively mild Arizona climate. The data reported herein tend to confirm this • report and also the reports of Singsen et al. (1959) and Combs et al. (1961) which showed that restriction markedly reduced the weight gains of hens in comparison to hens fed ad libitum.
ENERGY RESTRICTION OF HENS
Net energetic efficiency =
84.4 and 92.5% of the observed consumptions by the ad libitum hens. Equations proposed by Bird and Sinclair (1939) and Brody (1945) were found to predict even lower consumptions. Possible explanations of the failure of the Byerly equation to predict feed consumption in these experiments are differences in environmental temperature encountered and differences in activity of the birds. The Byerly equation is based on data from hens housed in cages at room temperature (ranging from 60° to 80°F.) while the data from these experiments were obtained from hens housed in floorpens at average temperatures of 54°F. Hence, it would seem likely that the Byerly data would under-predict feed consumption in these experiments because of the lower maintenance requirement of caged hens at room temperature. The Byerly equation can now be used to determine net energetic efficiency which is defined by Brody (1945) as follows:
gm. egg producedX1.6
— X100 gm. feed consumed for eggs X 3
945 Cal. of productive energy per pound. The control ration in Table 1 contained 943 Cal. of productive energy per pound. The Byerly equation is as follows: ^ = 0.523 W°-6™± 1.126AW+1.135E in which, F = feed consumption in grams per hen per day. W = average weight in grams. AW = average daily weight change in grams. E = grams of egg produced per hen per day. The above equation predicted feed consumptions of the control ration that were
in which 1.6 = the caloric value per gm. of egg. 3 = the caloric equivalent of TDN (total digestible nutrients) per gm. of feed. The above equation was refined as follows: 1) energy content determinations of eggs from hens in experiment 2 gave an average value of 1.66+.009 Cal. per gm. of whole egg including shell over a range of egg weights from 63 to 69 gm. Therefore, 1.66 was substituted for 1.6 in the original equation, and 2) the caloric equivalent of the feed was expressed as calculated Calories of metabolizable energy per gm. instead of TDN. The equation then becomes:
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hens consumed 20% less feed than the ad libitum hens. However, calculated intakes of protein, vitamins and minerals were comparable between treatments, therefore the restricted hens utilized these nutrients less efficiently because of lower egg production. Feed conversion is markedly influenced by energy level of the ration, level of egg production and maintenance requirement. The treatments used in these experiments exhibited wide differences in egg production and body weight (which is correlated to maintenance requirements), and the energy levels of the rations and energy intakes differed. Therefore, it was decided to use some method other than feed conversion to express efficiency of energy utilization for egg production. Hill (1956) used a partition equation proposed by Byerly (1941) to predict the feed consumption of Leghorn hens and found that the equation accurately predicted consumption of a ration containing
357
358
W. E. DONALDSON AND R. I. MILLAR
Net energetic efficiency =
gm. egg producedX1.66
-X100 gm. feed consumed for eggs X (y) or (3)
of the values between experiments despite wide differences in egg production and y = 2.947 Cal. of ME (calculated) per body weight, is a good indication that the gm. of control feed. method used for determining net effi2 = 2.776 Cal. of ME (calculated) per ciency was valid. gm. of restricted feed. When feed or energy intake is severely An indirect determination of feed con- restricted, hens lose body weight, and sumed for eggs can be made by using the their maintenance feed requirements are E term (1.135E) from the Byerly equation therefore lower. It is possible that in these where E equals gm. of egg produced per experiments economics of maintenance hen per day. The coefficient (1.135) con- offset inefficiencies of lower egg production verts E to gm. feed consumed above and that the net result was more efficient maintenance for eggs. Using this method, feed conversion and relative efficiency of the difference between observed and pre- restricted hens. Economies of maintedicted (by the Byerly equation) feed nance would not explain higher net enerconsumption is partitioned to mainte- getic efficiency in restricted hens as net nance. Since conditions of temperature and energetic efficiency is defined as the effimanagement favored a lower mainte- ciency of conversion of feed energy connance requirement in the Byerly data, and sumed beyond maintenance to egg energy. since a lower maintenance requirement in Basal metabolic rate (BMR) decreases the Byerly data would cause the Byerly in humans with caloric restriction. Since equation to under predict the total feed caloric restriction severe enough to alter consumption of the ad libitum hens, it BMR also results in weight loss, and since seemed logical to partition the discrepen- BMR is a function of weight or a power of cies to maintenance. weight, it is impossible to determine The predicted feed consumption of the whether or not decreased BMR is due to restricted hens was greater than the ob- weight loss or more economical energy served consumption. The above method of utilization or both. If decreased BMR is a determining E thus assumes that in the reflection of more economical energy restricted hens, the Byerly equation overestimates rather than underestimates TABLE 5.—Effect of energy restriction on net energetic efficiency of egg production maintenance. The assumption seems legitimate since Benedict et al. (1919) showed Net energetic efficiency1 that basal metabolic rate decreases in Experiment Ad libitum Restricted humans with caloric restriction. The resulting E terms were then sub52.6 1 49.5 52.7 2 49.6 stituted in the denominator of the Brody 52.7 Average 49.6 equation, and net energetic efficiency for the treatments were calculated and are Net energetic efficiency presented in Table 5. The restricted hens Cal. per gm. of egg produced -X100 were more efficient in converting feed Cal. consumed above maintenance per gm. energy into egg energy. The repeatability of egg produced in which
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ENERGY RESTRICTION OF HENS
SUMMARY
In two 36-week experiments using meat-type laying hens, intake of an experimental ration was controlled so that while protein, vitamin and mineral intakes were comparable, energy intake was resticted to 75% of controls. Energy restriction resulted in lower egg production, body weight and egg size but did not affect mortality. Although energy restriction improved feed conversion, the utilization of protein, vitamins and minerals for egg production was poorer. A method of appraising efficiency of energy utilization is presented which indicates that the restricted hens were more efficient than the controls. ACKNOWLEDGMENTS
The authors gratefully acknowledge supplies of materials used in these experiments from the following companies: Commercial Solvents Corporation, New York, New York for choline chloride;
Limecrest Research Laboratories, Newton, New Jersey for trace mineral supplement; Chas. Pfizer and Company, Brooklyn, New York for vitamin Bi2 and other B vitamin supplements; and Stabilized Vitamins Incorporated, Garfield, New Jersey for vitamins A and D 3 supplements. REFERENCES Benedict, F. G., W. R. Miles, P. Roth and H. MSmith, 1919. Human vitality and efficiency under prolonged restricted diet. Carnegie Inst. Publ. 280. Bird, S., and J. W. Sinclair, 1939. A study of the energy required for maintenance, egg production and changes in body weight in the domestic hen. Sci. Agriculture, 19: 542-550. Brody, S., 1945. Bioenergetics and Growth. Reinhold Publishing Corporation, New York, New York. Byerly, T. C , 1941. Feed and other costs of producing market eggs. Maryland Agr. Exp. Sta. Technical Bulletin A 1. Combs, G. F., B. Gattis and C. S. Shaffner, 1961. Studies with laying hens. 2. Energy restriction. Poultry Sci. 40: 220-224. Fraps, G. S., 1946. Composition and productive energy of poultry feeds and rations. Texas Agr. Exp. Sta. Bulletin 678. Heywang, B. W., 1940. The effect of restricted feed intake on egg weight, egg production and body weight. Poultry Sci. 19: 29-34. Hill, F. W., 1956. Studies of the energy requirements of chickens. 4. Evidence for a linear relationship between dietary productive energy level and the efficiency of egg production. Poultry Sci. 35: 59-63. Singsen, E. P., L. D. Matterson, J. Tlustohowicz and L. M. Potter, 1959. The effect of controlled feeding, energy intake and type of diet on the performance of heavy-type laying hens. Storrs (Connecticut) Agr. Exp. Sta. Bulletin 346. Titus, H. W., 1955, revised 1957. Energy values of feedstuffs for poultry. A chapter from The Scientific Feeding of Chickens. Interstate Printers and Publishers, Danville, Illinois.
MAY 10-12. AMERICAN FEED MANUFACTURERS ASSOCIATION, CONRAD HILTON HOTEL, CHICAGO, ILL. JUNE 26-29. ANNUAL MEETING OF POULTRY SCIENCE ASSOCIATION, UNIVERSITY OF ILLINOIS, URBANA
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utilization during restriction, it is logical that other body functions, such as egg formation, would also be more economical. Brody (1945) reviewed extensive data which showed that animals on low planes of nutrition utilized nutrients more efficiently due to increases in digestibility, metabolizability and assimilability. Hence, the better net energetic efficiency of egg production of energy restricted hens might well be explained by decreased BMR, more efficient digestion and assimilation of nutrients, and increased efficiency of the secretory processes of the ovary and oviduct.
359
353
J. Nutrition, 35: 253:263. Lofgreen, G. P., and M. Kleiber, 1953. The availability of phosphorus in alfalfa hay. J. Animal Sci. 12: 366-371. Visek, W. J., R. A. Monroe, E. W. Swanson and C. L. Comar, 1953. Determination of endogenous faecal calcium in cattle by a simple isotope dilution method. J. Nutrition, 50: 23-33.
W. E. DONALDSON AND R. I. MILLAR 2 Poultry Science Department, University of Rhode Island, Kingston, Rhode Island (Received for publication May 10. 1961)
INTRODUCTION
B
ECAUSE high feed consumption, obesity and relatively low egg production are characteristic of heavy meattype laying hens, interest has developed in attempting to improve the performance of this type of hen by restriction of feed intake. Numerous reports dealing with the effects of feed restriction during the growing period on subsequent egg production have been published, but there are few reports available on restriction during the laying period. Heywang (1940) observed drastic reductions in egg production but no effect on body weight or egg size by restricting the feed intake of Leghorn hens to 87J and 75% of ad libitum intake. Singsen et al. (1959) used body weight, egg production and environmental temperature to predict feed consumption of White Rock laying hens. Controlled feeding (based on predicted consumption) of high and low energy rations was compared with ad libitum feeding of the same rations. Al1
Contribution No. 1025 of the Rhode Island Agricultural Experiment Station. 2 Present address: Beacon Milling Company, Cayuga, New York.
though intake of the high energy ration was only 84.3% of ad libitum, production was not affected. Production was reduced when the low energy ration was controlfed (77% of ad libitum) even though digestible nutrient intake was calculated to be the same as the intake of the birds control-fed the high energy rations. Combs et al. (1961) reported that restriction of energy intake of heavy-type hens to 81 and 87% of ad libitum intake did not affect egg production, Haugh unit scores or mortality. Reductions in body weight gain and rate of increase in egg size were observed with energy restriction. The purpose of the experiments reported herein was to determine the effects of energy restriction on productive traits of meat-type laying hens. PROCEDURE
Two experiments were conducted in each of which April hatched pullets were placed on experiment on the succeeding January 21st and continued for 36 weeks All birds were reared on an ad libitumieeding system. In experiment 1, 29 White Plymouth Rock pullets were randomly assigned to
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 4, 2015
Effects of Energy Restriction on Laying Hens 1
354
W.
E. D O N A L D S O N AND R. I.
TABLE 1.-—Rations used in energy restriction experiment Ingredients
Calculated analysis: Protein, % Productive energy, Cal./lb.s 1 Metabolizable energy, Cal./lb.
Restricted
66.4125 10.0000 4.0000 2.0000
52.0631 12.5000 5.0000 2.5000
10.0000
18.4500
3.0000 1.2500 1.5000 1.0000 0.5000 0.1000
3.7500 1.5625 1.8750 1.2500 0.6250 0.1250
0.0750
0.0938
0.0500 0.0125 0.0500 0.0500
0.0625 0.0156 0.062S 0.0650
16.18 943 1,337
20.21 859 1,259
1 Contains not less than 6% manganese, 2% iron, 0.2% copper,2 0.12% iodine, 0.02% cobalt and 26.5% calcium. Contains not less than (per lb.) 2 gm. riboflavin, 4 gm. calcium3 pantothenate, 9 gm. niacin and 10 gm. choline chloride. Values of Fraps (1946) were used. ' Values of Titus (1955, revised in 1957) were used.
each of 8 groups. Four groups were placed on each of the experimental rations shown in Table 1. The control ration was available ad libitum. Daily feed consumption was measured. The consumption figures were used to determine the intake for the next day of the birds fed the restricted ration. For each pound of control feed consumed, the restricted birds received approximately 0.8 pounds. The feeding of the restricted ration at 8 0 % of the control ration intake resulted in calculated energy intakes of 72.9% (productive energy) and 7 5 . 3 % (metabolizable energy) of control {ad libitum) while the calculated intake of all other nutrients was essentially 100% of control. Adjustments of daily feed allowances were made as mortality occurred so t h a t the relative differences in feed intake between the t r e a t m e n t s were constant on a per bird basis. In experiment 2, 25 pullets were randomly assigned to each of 6 groups. The pullets were the progeny of the females
used in experiment 1 and males of a synthetic broiler strain (predominantly W y a n d o t t e ) . Three groups were placed on each of the treatments from experiment 1. Weekly feed consumption was determined for the control {ad libitum) birds, a n d restricted birds were given daily feed allotments based on the consumption of the controls for the previous week ( 8 0 % of ad libitum). Each group was maintained in 1 2 ' X 1 2 ' floor pens equipped with 2 hanging cylinder feeders. Water and calcite grit were available to all groups ad libitum. All groups were trapnested 3 days per week and pen egg production was recorded for the remainder of the time. Individual body weights were obtained initially and at 6-week intervals thereafter until the conclusions of the tests. Hen-day egg production during the two weeks immediately preceding each experiment was 47 and 4 2 % in experiment 1 and 35 and 33% in experiment 2 for the ad libitum and restricted groups, respectively. In experiment 2, all eggs produced on one day each week were weighed b y groups. At the beginning of experiment 2, 16 eggs ranging in weight from 63 to 69 grams were obtained for gross energy analysis from 2 groups of birds (one on each treatment). The eggs with shell were autoclaved at 250°C. and 15 p.s.i. steam pressure for 10 minutes; ground individually in a Waring blendor with an equal weight of water; dried to constant weight (approximately 12 hours) at 9 5 ° C ; ground with mortar and pestle to pass a 20 mesh screen; and pelleted and burned in an oxygen bomb calorimeter. RESULTS AND DISCUSSION The egg production, feed conversion, egg weight and mortality d a t a from both experiments are shown in Table 2. Analyses of variance based on the 3-day trapnest
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 4, 2015
Ground yellow corn Standard wheat middlings Fish meal, menhaden, 60% protein Meat and bone scrap, 50% protein Soybean oil meal, solvent, 44% protein Dhy. alfalfa meal, 17% protein, 70,000 IU of vitamin A per lb. Dried corn distillers' solubles Ground limestone Dicalcium phosphate Iodized salt Trace mineral mix1 Dry vitamin A and Ds supplement, 10,000 10 of A and 1,500 ICU of D> per gm. Vitamin Bn supplement, 6 mg, per lb. Butylated hydroxytoluene Choline chloride, 25% mixture Vitamin supplement2
Level in ration, % Control
MILLAR
355
ENERGY RESTRICTION OF HENS TABLE 2.—Effect
Period
1
of energy restriction on egg production, feed conversion, egg weight and mortality
Hen -day production, %
d
A
Lbs. feed/dozen eggs
libitum
Restricted
Ad libitum
Restricted
1 2 3 4 S 6
45.4 60.8 58.8 55.4 46.8 31.0
37.1 48.8 46.2 55.0 48.2 33.0
8.74 7.34 7.63 8.49 9.25 13.99
8.43 6.80 7.76 7.24 7.15 10.00
All
49.8
44.7
8.79
7.73
1 2 3 4 5 6
74.3 67.9 63.3 60.7 54.2 35.9
67.5 59.3 55.4 53.5 44.6 28.0
5.97 6.46 6.92 7.06 7.75 12.45
4.98 5.99 6.27 6.33 7.24 12.21
All
59.8
51.7
7.27
6.58
Lbs. feed/lbs. eggs2 Ad libitum
Restricted
Egg weight, gm.•/egg
Mortality,
%
Ad libitum
Restricted
Ad libiium
Restricted
.— — —. — .— — —
— — .— — — — —
12.1
22.4
66.5 67.5 67.9 67.7 68.0 69.3
65.2 65.9 65.4 67.0 65.9 66.0
67.6
65.9
14.7
8.0
Experiment P
—. — .— — —. — —
Experiment 2* 3.39 2.89 3.62 3.43 3.85 3.62 3.94 3.57 4.31 4.15 6.79 6.99 4.07
3.77
1 Each period was 6 weeks in duration. The experiment began on January 21st and ended on September 28th. 2 No egg weights were obtained in experiment 1, therefore conversion expressed as pounds of feed per pound of eggs are given for experiment 2 only. 3 Each value represents the average of 4 groups of 29 birds each. 4 Each value represents the average of 3 groups of 25 birds each.
records reveal statistically significant (P = 0.01) decreases in egg production in the restricted groups in both experiments. The apparent interaction between treatments and periods in experiment 1 is not statistically significant (P = 0.05). The restricted hens consumed less feed per dozen eggs except during period 3 in experiment 1. The restricted hens in experiment 2 consumed less feed per pound of egg except during period 6. The egg weights of the restricted hens were significantly (P = 0.01) lower. Egg weight generally increased with age in the ad libitum groups but not in the restricted groups. There was no consistent effect of treatment on mortality in the two experiments. The body weight data from both experiments are shown in Table 3. Body weights were significantly lower (P = 0.01) in the
restricted groups. The general tendency in both experiments was for gradual weight increase in the ad libitum groups over the entire experimental period and for weight decreases in the restricted groups during the first two periods. The restricted groups regained much of the weight losses during the remaining periods. The data from both experiments demonstrate that restriction of energy intake of meat-type laying hens to approximately 75% of ad libitum reduces egg production. There is an indication in experiment 1 that during conditions of warmer environmental temperatures (periods 4, 5 and 6), energy restriction did not affect production (see Table 4 for mean environment temperatures). This apparent effect of an interaction of temperature (periods) with energy restriction on egg production was not statistically
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TABLE 3.—Effect Period 1
of energy restriction on body weight Average body weight, lbs. Ad libitum
Restricted
Experiment 1 6.99 6.64 6.35 6.53 6.78 6.83 6.87
7.00 7.05 7.02 7.06 7.26 7.27 7.10
Start 1 2 3 4 5 6
Experiment 7.17 7.30 7.29 7.54 7.64 7.77 7.69
2 7.09 6.88 6.49 6.60 6.60 6.24 6.80
1 Each period was six weeks in duration. The experiments began on January 21st and ended on September 28th.
significant (P = 0.05) and did not appear in experiment 2; therefore it must be concluded that energy intake approximating 75% of ad libitum is too severe a restriction under all conditions of temperature encountered in these experiments. These data are. in disagreement with those of Singsen et al. (1959) and Combs et al. (1961) who reported that energy restriction had no effect on production. However, the levels of energy restriction employed by both groups of workers cited (approximately 84% by Singsen et al. and 8 1 % by Combs et al.) were less than the levels used in these experiments. Thus, it would appear that the minimum energy requirement of heavy-breed laying hens is between 75 and 8 1 % of ad libitum intake. The depression of egg weights by energy restriction was consistent and is in agreement with the data of Combs et al. (1961). Singsen et al. (1959) did not observe a reduction in egg weight, probably due to less severe restriction. Lowered egg weight may reflect attempt by the hen to maintain reproductive capacity under condi-
The restricted hens exhibited better feed conversions when expressed both as pounds of feed per dozen eggs and pounds of feed per pound of eggs even though egg production was lower. This result was not wholly unexpected since the restricted TABLE 4.—Mean environmental temperature by periods Mean temperature, °F. l Period
Duration of period
1 2 3 4 5 6
Jan. 21-Mar. 2 Mar. 3-Apr. 13 Apr. 14-May 25 May 26-July 6 July 7-Aug. 17 Aug. 18-Sept. 28
Average
Experiment 1
Experiment 2
28.7 40.7 54.9 64.8 71.5 67.5
33.0 38.2 53.9 65.8 68.3 61.7
54.7
53.5
1 Temperature values are based on averages of daily minimum and maximum temperatures recorded at a weather station within 2 miles of the pens.
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Start 1 2 3 4 5 6
tions of restriction by allotting less nutrients to each egg. The body weight data demonstrate quite conclusively that the level of energy intake in the restricted groups was not high enough to maintain normal body weight at the relatively cold temperatures of periods one and two in both experiments. As the temperatures moderated during succeeding periods, there were indications that energy intake would have been sufficient to maintain weight since the hens in the restricted groups showed a trend toward regaining the earlier weight losses. Heywang (1940) reported that 75% restriction of feed intake did not reduce the body weight of White Leghorn hens in the relatively mild Arizona climate. The data reported herein tend to confirm this • report and also the reports of Singsen et al. (1959) and Combs et al. (1961) which showed that restriction markedly reduced the weight gains of hens in comparison to hens fed ad libitum.
ENERGY RESTRICTION OF HENS
Net energetic efficiency =
84.4 and 92.5% of the observed consumptions by the ad libitum hens. Equations proposed by Bird and Sinclair (1939) and Brody (1945) were found to predict even lower consumptions. Possible explanations of the failure of the Byerly equation to predict feed consumption in these experiments are differences in environmental temperature encountered and differences in activity of the birds. The Byerly equation is based on data from hens housed in cages at room temperature (ranging from 60° to 80°F.) while the data from these experiments were obtained from hens housed in floorpens at average temperatures of 54°F. Hence, it would seem likely that the Byerly data would under-predict feed consumption in these experiments because of the lower maintenance requirement of caged hens at room temperature. The Byerly equation can now be used to determine net energetic efficiency which is defined by Brody (1945) as follows:
gm. egg producedX1.6
— X100 gm. feed consumed for eggs X 3
945 Cal. of productive energy per pound. The control ration in Table 1 contained 943 Cal. of productive energy per pound. The Byerly equation is as follows: ^ = 0.523 W°-6™± 1.126AW+1.135E in which, F = feed consumption in grams per hen per day. W = average weight in grams. AW = average daily weight change in grams. E = grams of egg produced per hen per day. The above equation predicted feed consumptions of the control ration that were
in which 1.6 = the caloric value per gm. of egg. 3 = the caloric equivalent of TDN (total digestible nutrients) per gm. of feed. The above equation was refined as follows: 1) energy content determinations of eggs from hens in experiment 2 gave an average value of 1.66+.009 Cal. per gm. of whole egg including shell over a range of egg weights from 63 to 69 gm. Therefore, 1.66 was substituted for 1.6 in the original equation, and 2) the caloric equivalent of the feed was expressed as calculated Calories of metabolizable energy per gm. instead of TDN. The equation then becomes:
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hens consumed 20% less feed than the ad libitum hens. However, calculated intakes of protein, vitamins and minerals were comparable between treatments, therefore the restricted hens utilized these nutrients less efficiently because of lower egg production. Feed conversion is markedly influenced by energy level of the ration, level of egg production and maintenance requirement. The treatments used in these experiments exhibited wide differences in egg production and body weight (which is correlated to maintenance requirements), and the energy levels of the rations and energy intakes differed. Therefore, it was decided to use some method other than feed conversion to express efficiency of energy utilization for egg production. Hill (1956) used a partition equation proposed by Byerly (1941) to predict the feed consumption of Leghorn hens and found that the equation accurately predicted consumption of a ration containing
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Net energetic efficiency =
gm. egg producedX1.66
-X100 gm. feed consumed for eggs X (y) or (3)
of the values between experiments despite wide differences in egg production and y = 2.947 Cal. of ME (calculated) per body weight, is a good indication that the gm. of control feed. method used for determining net effi2 = 2.776 Cal. of ME (calculated) per ciency was valid. gm. of restricted feed. When feed or energy intake is severely An indirect determination of feed con- restricted, hens lose body weight, and sumed for eggs can be made by using the their maintenance feed requirements are E term (1.135E) from the Byerly equation therefore lower. It is possible that in these where E equals gm. of egg produced per experiments economics of maintenance hen per day. The coefficient (1.135) con- offset inefficiencies of lower egg production verts E to gm. feed consumed above and that the net result was more efficient maintenance for eggs. Using this method, feed conversion and relative efficiency of the difference between observed and pre- restricted hens. Economies of maintedicted (by the Byerly equation) feed nance would not explain higher net enerconsumption is partitioned to mainte- getic efficiency in restricted hens as net nance. Since conditions of temperature and energetic efficiency is defined as the effimanagement favored a lower mainte- ciency of conversion of feed energy connance requirement in the Byerly data, and sumed beyond maintenance to egg energy. since a lower maintenance requirement in Basal metabolic rate (BMR) decreases the Byerly data would cause the Byerly in humans with caloric restriction. Since equation to under predict the total feed caloric restriction severe enough to alter consumption of the ad libitum hens, it BMR also results in weight loss, and since seemed logical to partition the discrepen- BMR is a function of weight or a power of cies to maintenance. weight, it is impossible to determine The predicted feed consumption of the whether or not decreased BMR is due to restricted hens was greater than the ob- weight loss or more economical energy served consumption. The above method of utilization or both. If decreased BMR is a determining E thus assumes that in the reflection of more economical energy restricted hens, the Byerly equation overestimates rather than underestimates TABLE 5.—Effect of energy restriction on net energetic efficiency of egg production maintenance. The assumption seems legitimate since Benedict et al. (1919) showed Net energetic efficiency1 that basal metabolic rate decreases in Experiment Ad libitum Restricted humans with caloric restriction. The resulting E terms were then sub52.6 1 49.5 52.7 2 49.6 stituted in the denominator of the Brody 52.7 Average 49.6 equation, and net energetic efficiency for the treatments were calculated and are Net energetic efficiency presented in Table 5. The restricted hens Cal. per gm. of egg produced -X100 were more efficient in converting feed Cal. consumed above maintenance per gm. energy into egg energy. The repeatability of egg produced in which
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ENERGY RESTRICTION OF HENS
SUMMARY
In two 36-week experiments using meat-type laying hens, intake of an experimental ration was controlled so that while protein, vitamin and mineral intakes were comparable, energy intake was resticted to 75% of controls. Energy restriction resulted in lower egg production, body weight and egg size but did not affect mortality. Although energy restriction improved feed conversion, the utilization of protein, vitamins and minerals for egg production was poorer. A method of appraising efficiency of energy utilization is presented which indicates that the restricted hens were more efficient than the controls. ACKNOWLEDGMENTS
The authors gratefully acknowledge supplies of materials used in these experiments from the following companies: Commercial Solvents Corporation, New York, New York for choline chloride;
Limecrest Research Laboratories, Newton, New Jersey for trace mineral supplement; Chas. Pfizer and Company, Brooklyn, New York for vitamin Bi2 and other B vitamin supplements; and Stabilized Vitamins Incorporated, Garfield, New Jersey for vitamins A and D 3 supplements. REFERENCES Benedict, F. G., W. R. Miles, P. Roth and H. MSmith, 1919. Human vitality and efficiency under prolonged restricted diet. Carnegie Inst. Publ. 280. Bird, S., and J. W. Sinclair, 1939. A study of the energy required for maintenance, egg production and changes in body weight in the domestic hen. Sci. Agriculture, 19: 542-550. Brody, S., 1945. Bioenergetics and Growth. Reinhold Publishing Corporation, New York, New York. Byerly, T. C , 1941. Feed and other costs of producing market eggs. Maryland Agr. Exp. Sta. Technical Bulletin A 1. Combs, G. F., B. Gattis and C. S. Shaffner, 1961. Studies with laying hens. 2. Energy restriction. Poultry Sci. 40: 220-224. Fraps, G. S., 1946. Composition and productive energy of poultry feeds and rations. Texas Agr. Exp. Sta. Bulletin 678. Heywang, B. W., 1940. The effect of restricted feed intake on egg weight, egg production and body weight. Poultry Sci. 19: 29-34. Hill, F. W., 1956. Studies of the energy requirements of chickens. 4. Evidence for a linear relationship between dietary productive energy level and the efficiency of egg production. Poultry Sci. 35: 59-63. Singsen, E. P., L. D. Matterson, J. Tlustohowicz and L. M. Potter, 1959. The effect of controlled feeding, energy intake and type of diet on the performance of heavy-type laying hens. Storrs (Connecticut) Agr. Exp. Sta. Bulletin 346. Titus, H. W., 1955, revised 1957. Energy values of feedstuffs for poultry. A chapter from The Scientific Feeding of Chickens. Interstate Printers and Publishers, Danville, Illinois.
MAY 10-12. AMERICAN FEED MANUFACTURERS ASSOCIATION, CONRAD HILTON HOTEL, CHICAGO, ILL. JUNE 26-29. ANNUAL MEETING OF POULTRY SCIENCE ASSOCIATION, UNIVERSITY OF ILLINOIS, URBANA
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utilization during restriction, it is logical that other body functions, such as egg formation, would also be more economical. Brody (1945) reviewed extensive data which showed that animals on low planes of nutrition utilized nutrients more efficiently due to increases in digestibility, metabolizability and assimilability. Hence, the better net energetic efficiency of egg production of energy restricted hens might well be explained by decreased BMR, more efficient digestion and assimilation of nutrients, and increased efficiency of the secretory processes of the ovary and oviduct.
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