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Factorial Estimation of Energy Requirement for Egg Production1
Factorial Estimation of Energy Requirement for Egg Production1 A. CHWALIBOG Department of Animal Science and Animal Health, The Royal Veterinary and Agricultural University, Biilmosvej 13, 1870 Frederiksberg C, Denmark (Received for publication May 28, 1991)
1992 Poultry Science 71509-515
sum of energy required for maintenance and production, by inserting fixed values The different methods used to estimate for the maintenance requirement and an the energy requirement for production can overall efficiency of energy utilization for be classified into two categories: empirical growth and egg production. and factorial methods. Empirical methods For egg production, the efficiency of are based on measurements of animal ME utilization for energy deposition in performance at given levels of energy eggs (Kb) varies between .60 and .85, as intake, and have often been used to reviewed by Chwalibog (1985) and Luiting evaluate energy requirements for egg (1990). This variation is undoubtedly due production. The factorial method is based to a number of genetic, nutritional, and on separation of the metabolic processes environmental factors (Farrell, 1975; Balcontributing to the energy requirement. nave et al, 1978; Rising et al, 1988; Luiting, The energy requirement is calculated as a 1990; Pesti et al., 1990; Spratt et al, 1990), but the main reason is an inconsistency in the Ko estimate, as it includes both the Supported by the Danish Agricultural and Veteri- utilization for energy deposition in protein (Kop) and in fat (Kof), which are not nary Research Council. INTRODUCTION
509
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ABSTRACT Based on balance and respiration measurements with 60 White Leghorns during the laying period from 27 to 48 wk of age, a factorial method for estimating the energy requirement for egg production is proposed. The present experiment showed that the deposition of fat and energy increased during the laying period, but protein deposition slightly decreased. It has been shown that the efficiency of ME utilization for fat energy deposition is higher than for protein energy deposition in the egg. Because the proportions of protein and fat differ during the laying period, and because energy utilization is different between protein and fat, the ME requirement was calculated as the sum of ME for maintenance and the partial requirements for protein, fat, and carbohydrate deposition. For practical applications, functions for prediction of protein (OP), fat (OF), and energy (OE) in eggs during the laying period have been established according to the following model: OP, OF, or OE = a + bl x egg (grams per day) + b2 x age (weeks). The average ME requirement [calculated with either measured or predicted chemical composition, and by applying a constant maintenance requirement of 98 kcal/kg BW 75 and partial efficiencies for energy retention in protein (Kop = .50), fat (Kof = .79), and carbohydrates (Koc = .79)]increased from .26 Meal at 27 wk of age to .29 Meal at 48 wk, corresponding to 5.93 and 6.07 Mcal/kg egg. {Key words: egg composition, energetic efficiency, egg production, requirement, prediction)
CHWALIBOG
510
MATERIALS AND METHODS Sixty White Leghorn hens were measured during a laying period from 27 to 48 wk of age. The hens were kept in the battery cages either singly (12 birds) or 3 hens per cage (48 birds) with an area of 2,100 or 700 cm2 per hen, respectively. The battery cages were adjusted for separate feeding and collection of droppings and eggs. Ambient temperature was maintained at 17 or 21 C, and a constant 17-h lighting was applied. All hens were provided ad libitum access to a commercial diet containing 150 g crude protein and 3.91 Meal gross energy/kg feed. The amount of ME measured from balance experiments was on average 2.76 Mcal/kg feed. The composition of the diet and the chemical analyses are shown in Table 1. The measurements started after a preliminary period of 5 to 7 wk during which the hens were kept under the same conditions as during the experimental time. Each hen or group of hens was
TABLE 1. Feed composition Ingredients and composition Barley Oat Maize Alfalfa meal Meat and bone meal Rshmeal Fat, animal CaCQ3 Nad MnS04 ZnO Ethoxyquin Vitamin mixture1 Chemical composition Dry matter Ash Nitrogen Crude fat Energy, Mcal/kg
Content (g/kg) 608.0 100.0 50.0 70.0 57.0 40.0 30.0 35.0 4.4 5 .1 2 4.8 882.0 865 23.9 72.0 3.94
Supplied in milligrams per kilogram of diet: retinol, 4.61; cholecakiferol, .048; a-tocopherol, 13.44; thiamin, 24; riboflavin, 8.16; nicotinamid, 12.0; glutamic acid, .77; cyanocobalamin, .015; pantothenic acid, 1656; biotin, .072; and choline, 192.0.
measured in eight consecutive balance periods. Each period consisted of 7 days collection of droppings and eggs, and was followed by a 14-day intermediate period. A total of 188 measurements were made. The feed was weighed out for each animal or group of hens for a 7-day period and aliquot samples were taken for chemical analyses. Droppings were collected daily before feeding, and stored in a deepfreezer until the end of a balance period. Eggs were collected daily, weighed, and cooled until each balance period was concluded. After concluding a collection period, droppings were thawed, weighed, mixed, and their energy content was analyzed. Prior to chemical analyses, eggs were boiled, minced, and freezedried. The freeze-dried material was ground in mortars and distributed for chemical analyses of dry matter, ash, nitrogen, fat, and energy. The chemical analyses were done according to standard procedures of the Association of Official Analytical Chemists (1975). Statistical analyses were based on procedures suggested by Gill (1978) and
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equal. For growing animals it is well established that the partial efficiency for protein retention is lower than for fat retention (as reviewed by Klein and Hoffmann, 1989). There is also information that the partial efficiencies of protein and fat deposition in the egg are of the same order of magnitude as the respective values in growing animals (Klein and Hoffmann, 1989; Chwalibog, 1991). Furthermore, the chemical composition of eggs depends on the genetic background and age of the birds (Chwalibog, 1985), and thus the amount of energy deposited in protein and fat will be different during a laying period. Therefore, the objective of the present work was to investigate the partition of energy deposition in the egg during the laying period, and to demonstrate a factorial method in which the partial efficiencies of ME utilization for each component of energy in the egg are considered. Because the amount of protein and fat deposited in eggs during a laying period can be difficult to assess under practical conditions, predictions of egg composition have been developed and applied in energy requirement calculations.
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TABLE 2. Protein (OP), fat (OF), and energy (OE) content in eggs, during the laying period from 27 to 48 wk of age (x ± SEM) OP
Age (wk) 27 30 33 36 39 42 45 48
OF (g/kg)
25 27 26 23 23 21 21 22
1.11 .99 .80 .85 1.19 1.08 .96 1.45
251 .0176
92 ± 1.18 97 ± .98 97 ± .99 99 ± .99 101 ± 1.43 102 ± 1.61 104 ±1.22 107 ± 1.84 Statistics 13.0 .0001
(Mcal/kg) 1.69 ± .015 1.71 ± .011 1.72 ± .010 1.74 ± .010 1.75 ± .018 1.74 ± .018 1.77 ± .014 1.79 ± .024 4.43 .0001
'Number of measurements.
performed by means of base SAS® software (Ray, 1982). The main effect in the analysis was age of hen. All results were calculated per hen per day. The following terminology was used in the present studies: BW-75 = metabolic body weight; MEm = ME requirement for maintenance; MEo = ME requirement for egg production; MEreq = ME requirement for maintenance and production; OE = energy deposited in eggs; OPE = protein energy deposited in eggs; OFE = fat energy deposited in eggs; OCE = carbohydrate energy deposited in eggs; OP = protein deposited in eggs; OF = fat deposited in eggs; OC = carbohydrate deposited in eggs; Ko = efficiency of ME utilization for OE; Kop = efficiency of ME utilization for OPE; Kof = efficiency of ME utilization for OFE; and Koc = efficiency of ME utilization for OCE.
of eggs divided by the number of days in the collection period, and it varied between 83 and 88%. Egg size increased from about 52 g at an age of 27 wk to 60 g at 48 wk. As demonstrated in Table 2, the amount of protein averaged 131 ± .39 g/kg egg, with values tending to decrease with age. The amount of fat increased from 92 to 107 g/ kg egg, and consequently energy content increased from 1.7 to 1.8 Mcal/kg egg. In both cases the increase was highly significant. The average content of ash was 9 ± .07 and carbohydrates 9 ± .13 g/kg egg. Based on individual determinations (n = 188) of energy content and chemical composition of eggs, estimations of the energetic equivalents (kilocalories) of OP
RESULTS AND DISCUSSION The average BW during the period of laying was 1.680 ± .012 kg (x ± SEM). Generally, all hens showed the same pattern for feed intake, increasing from 95 g at the beginning of the experiment to 125 g by an age of 35 wk, and remaining relatively constant after that time. The course of egg production demonstrated in Figure 1 followed the same pattern for all hens, reaching a plateau of about 50 g/ day at an age of 38 to 40 wk. The laying percentage was calculated as the number
33
36 39 42 Age, weeks
FIGURE 1. Egg production and laying percentage in relation to the age of hens.
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F value Probability
133 ± 134 ± 131 ± 132 ± 131 ± 129 ± 129 ± 130 ±
OE
512
CHWAUBOG TABLE 3. Requirement for metabolizable energy (MEreq), calculated as the sum of ME for maintenance (MEm) and ME for egg production (MEo), and the difference between ME intake (MEi) and MEreq BW
MEm
MEo
MEreq
(wk) 27 30 33 36 39 42 45 48
(kg) 159 1.64 1.64 1.69 1.69 1.71 1.76 1.77 1.68
139 142 142 145 145 146 150 150 145
118 130 129 136 138 137 138 138 133
256 272 271 281 284 284 288 288 278
X
(grams), OF (grams), and OC (grams) were made according to the following regression (with standard errors in parentheses):
MEi (kcal) 257 300 315 345 318 308 301 297 305
Difference between MEi and MEreq 1 28 44 64 34 24 13 9 27
MEo = (OP x 5.8 x 1.99) + (OF x 9.5 x 1.27) + (OC x 4.1 x 1.27), [2]
where MEo is in kalocalories, and OP, OF, and OC are in grams. The values 5.8, 9.5, OE = [5.8 (.12) x OP] + [9.5 (.15) X OF] and 4.1 kcal are energetic equivalents of + [4.1 (.35) x OC], [1] OP, OF, and OC from Regression [1], and the values 1.99 and 1.27 kcal are reciprowhere residual standard deviation (RSD) cals of Kop, Kof, and Koc, corresponding = .73; CV = .87%; and R2 = .997. The to the amount of MEo necessary for parameters obtained were applied to cal- deposition of 1 kcal of OPE, OFE, and culations of energy deposition in egg OCE, respectively. In other words, the protein, fat, and carbohydrates during the MEo was calculated as a sum of ME necessary for deposition of 1 g of protein laying period. As demonstrated in Figure 2, the main (5.8 x 1.99 = 11.5 kcal/g), 1 g of fat (9.5 x energy components in eggs were fat and 1.27 = 12.1 kcal/g), and 1 g carbohydrates protein, which contributed different (4.1 X 1.27 = 5.2 kcal/g) in eggs. The amounts of energy depending on the age calculations of mean values and differof the birds. Thus, at the beginning of the ences between ME intake and requirement laying period the ratio OPE:OE was 46%, and OFE:OE was 51%, but during laying these ratios changed to 42% and 56% for OPE:OE and OFE:OE, respectively, at the DU • OPEOE D 0FE:OE age of 48 wk. The contribution of energy from carbohydrates was on average 2% of 55 n n OE. The requirement of ME for maintenance : r-| and egg production (MEreq = MEm + 50 MEo) was calculated by inserting the values obtained by Chwanbog (1985) with 45 White Leghorns kept singly in battery cages at 17 C. The MEm was calculated as equal to 98 kcal/kg BW-75; the MEo was 27 30 33 36 39 42 45 48 calculated from Kop (.50) and Kof (.79). Age, weeks Furthermore, it was assumed that Koc was the same (.79) as Kof. Subsequently, MEo FIGURE 2. Partition of energy deposited in eggs. was calculated according to the following Values are protein (OPE) and fat (OFE) in relation to formula: die total energy (OE).
IMJII
1i i
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Age
513
ENERGY REQUIREMENT FOR EGG PRODUCTION
[3] 2
where RSD = .25; CV = 3.91%; and R = .930.
5
290 : 280 : 270 : 260 j 250 : 240^
27
30
33 36 39 42 Age, weeks
45
48
FIGURE 3. Requirement of ME calculated from measured egg composition (Function [2] and Table 3) and from predicted values (Function [6]).
OF = -1.14 (.176) + [.101 (.0033) X egg] stant 12.1 was the amount of MEo neces+ [.029 (.0032) X age], [4] sary for deposition of 1 g of fat, multiplied by the predicted fat deposition; and the 2 where RSD = .29; CV = 6.16%; and R = constant 5.2 was the amount of MEo necessary for deposition of 1 g of carbohy.867. drate, multiplied by the average carbohydrate content in eggs. As demonstrated in OE = -B.5 (2.10) + [1.76 (.04) x egg] Figure 3, the differences between MEreq + [.20 (.038) x age] calculated from measured egg composi[5] tion and from predicted values were negligible. On average, the requirement of where RSD = 3.54; CV = 4.21%; and R2 = ME for maintenance and egg production .924. The equations showed very good fit was 256 kcal at 27 wk of age, and 286 at 48 between the applied models and the wk of age, corresponding to 5.92 and 6.07 measured data, with low CV and high R2 Mcal/kg egg. values. Finally, similar calculations of MEreq General Discussion were performed as a sum of MEm and The chemical composition of egg content MEo calculated from predicted values of protein and fat from Regressions [3] and showed a tendency for decreasing OP with [4], and by adding a constant value of 9 g/ age, but OF and OE increased significantly. kg egg for carbohydrate content. The Although there are several measurements computations were accomplished as fol- of egg composition, only a few reports describe the effect of age on egg composilows: tion. The pattern of OP observed in the present experiments is in general agreeMEreq = (98 X kg BW-75) + 11.5 X [(.138 ment with Anderson et ah (1978), and Fisher x egg) - (.0086 x age)] + 12.1 x (1983), who reported a decline in OP over [-1.14 + (.101 x egg) + (.029 x the 1st laying yr. Whether or not age has an age)] + 5.2 x (.009 x egg). influence on OF and OE in eggs, has not [6] been reported in the literature. However, the well-known fact that egg size increases The inserted value of MEm was 98 kcal/ with age supports the present results, as kg BW75; the constant 11.5 was the increases in egg size are directly related amount of MEo (kilocalories) necessary for with increases in OE (Sibbald, 1979). deposition of 1 g of protein, multiplied by Energy partition between OP, OF, and the predicted protein deposition; the con- OC was calculated with the regression
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OP = [.138 (.0018) X egg] - [.0086 (.00238) X age],
300 r requirement, kcal/day
are demonstrated in Table 3. On average, the consumed ME was about 10% higher than the calculated requirement. Because the amount of protein, fat, and energy deposited in eggs can be difficult to assess, the following predictions for OP (grams per day), OF (grams per day), and OE (kilocalories per day) were established based on egg production (grams per day) and age of animals (weeks), (with standard errors in parentheses).
514
CHWALIBOG
that of OFE. In the present calculations it was assumed that Koc = Kof, which may or may not be correct. However, due to very small amount of carbohydrate deposited in eggs, changes in Koc will have negligible influence on the final MEreq. Nevertheless, it has to be emphasized that the presented absolute values of MEm and energy utilization cannot be generalized, as they were obtained under the specific conditions of the experiment. It is likely that MEm and Kop, especially, may be different for other breeds and under different conditions. Even so, the concepts of the equations can be used as a framework for a factorial approach. The advantage of the presented method of calculation is undoubtedly the recognition that the overall utilization of ME for egg production is a less accurate predictor of ME requirement than are the partial efficiencies. Using the same Ko implies that the ratio between OPE and OFE is constant during the laying period, or that Kop = Kof (Chwalibog, 1991). Because, neither of these assumptions is true, as demonstrated in the present paper, the two major components of energy in the egg must be separated. Thus, by applying partial efficiencies, a bias, caused by different chemical composition of eggs during the laying period or due to different genetic and nutritional factors, will be markedly reduced. In the present approach, two major components of energy metabolism (i.e., MEm and MEo) have been taken into account. However, a difference of about 10% between ME intake and MEreq was measured. Part of this difference may be related to changes in body weight. The correction for body weight changes can be achieved from net energy values of body gain and energetic efficiencies of growth, with values reported by Klein and Hoffmann (1989), Spratt et al. (1990), and Chwalibog (1991). Because the method described is based on measurement of the chemical composition of eggs, it is essential to have data for OP and OF during the laying period. These can be difficult to obtain, and therefore the predictions of OP, OF, and OE were developed by regression techniques. The obtained functions showed very good fit between the experimental data and the
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constants obtained in the present experiment. These constant are close to mean enthalpies tabulated by Brouwer (1965). It has been shown in the present paper that increased OE during the laying period was due to increases in OFE, but not in OPE. In the present calculations the values of MEm, Kop, and Kof, obtained from measurements with birds kept singly at ambient temperature of 21C, were incorporated in the calculations applied to the material including hens kept in groups of three per cage, and at 17 C. This may be debatable, as MEm values depend on a number of nutritional and environmental factors, as reviewed by Luiting (1990). However, as discussed by Chwalibog (1985), the use of the same value of MEm can be justified within one breed and for hens kept close to the optimum biological temperature of 19 C (Tzschentke and Nichelmann, 1984). Although different housing may change the energy expenditure for locomotor activity (Madrid et ah, 1981; MacLeod et at, 1982), and thus influence MEm values, it was assumed for the present calculations that those changes would be smaller than the individual variation in MEm. Concerning the partial energetic efficiencies for egg production, there is no information concerning the extent to which they may be influenced by internal and external factors. Klein and Hoffmann (1989) concluded from literature in the last 25 yr that the values of Kof for growing animals lie very close to .8. For Kop the variation is much higher, between .4 and .7, depending on a number of genetic, nutritional, and environmental factors, as well as due to different experimental techniques and methods of calculations (MacLeod and Jewitt, 1988; Chwalibog, 1991). There have been only a few attempts to estimate the partial efficiencies for laying hens. The values inserted in the present calculations are in good agreement with those reported by Hoffmann and Schiemann (1973), who demonstrated nearly similar values for Kof of .74 and slightly lower values for Kop of .44, and are thus of the same order of magnitude as the respective values for energy utilization in growing animals. This also confirms that the energy requirement for OPE is higher than
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Association of Animal Production Publication 31, Clermont-Ferrand, France. Gill,}. L., 1978. Design and Analyses of Experiments in the Animal and Medical Sciences. Vol. 1. The Iowa State University Press, Ames, IA. Hoffmann, L., and R. Schiemann, 1973. Die Verwertung der Futterenergie durch die legende Henne. Arch. Tirernahr. 23:105-132. Klein, M., and L. Hoffmann, 1989. Bioenergetics of protein retention. Pages 404-440 in: Protein Metabolism in Farm Animals. H. D. Block, B. O. Eggum, A. G. Low, O. Simon, and T. Zebrowska, ed. Oxford Scientific Publications, Deutscher Landwirtschaftsverlag, Berlin, Germany. Luiting, P., 1990. Genetic variation of energy partitioning in laying hens: causes of variation in residual feed consumption. World's Poult. Sci. J. 46: 133-152. Madrid, A., P. M. Maiorino, and B. L. Reid, 1981. Cage density and energy utilization. Nutr. Rep. Int. 23: 89-93. MacLeod, M. G., and T. R. Jewitt, 1988. Maintenance energy requirements of laying hens: A comparREFERENCES ison of measurements made by two methods based on indirect calorimetry. Br. Poult. Sci. 29: Anderson, G. B., W. Bolton, R. M. Jones, and M. H. 63-74. Draper, 1978. Effect of age of the laying hen on the composition of the egg. Br. Poult. Sci. 19:741-745. MacLeod, M. G., T. R. Jewitt, J. White, M. Verbrugge, and M. Mitchell, 1982. The contribution of Association of Official Analytical Chemists, 1975. locomotor activity to energy expenditure in the Official Methods of Analysis. 12th ed. Association domestic fowl. Pages 297-300 in: Proceedings of of Official Analytical Chemists, Washington, DC. the 9th Symposium on Energy Metabolism, Balnave, D., D. J. FarreU, and R. B. Cumming, 1978. The European Association of Animal Production minimum metabolizable energy requirement of Publication 29, Lillehammer, Norway. laying hens. World's Poult. Sci. J. 34:149-154. Brouwer, E., 1965. Report of Sub-Committee on Pesti, G. M., E. Thomson, and D. J. Farrell, 1990. Energy exchange of two breeds of hens in respiration Constants and Factors. Pages 441-443 in: Proceedchambers. Poultry Sci. 6958-104. ings of the 3rd Symposium on Energy Metabolism, European Association of Animal Produc- Ray, A. A., 1982. SAS* User's Guide: Statistics. SAS Institute Inc., Cary, NC. tion Publication 11, Troon, Scotland. Chwalibog, A., 1985. Studies on Energy Metabolism in Rising, R., P. M. Maiorino, J. Alak, and B. L. Reid, 1989. Indirect calorimetry evaluation of dietary protein Laying Hens. Statens Husdyrbrugsforseg, and animal fat effects on energy utilization of Beretning 578, Denmark. laying hens. Poultry Sci. 68258-264. Chwalibog, A., 1991. Energetics of Animal Production. Research in Copenhagen, Review and Sugges- Sibbald, I. R., 1979. The gross energy of avian eggs. Poultry So. 58:404-409. tions. Acta Agric. Scand. 41:147-160. Farrell, D. J., 1975. A comparison of the energy Spratt, R. S., H. S. Bayley, B. W. McBride, and S. Leeson, 1990. Energy metabolism of broiler breeder hens. metabolism of two breeds of hens and their cross 1. The partition of dietary energy intake. Poultry using respiration calorimetry. Br. Poult. Sci. 16: ScL 69:1339-1347. 103-113. Fisher, C, 1983. The physiological basis of the amino Tzschentke, B., and M. Nichehnann, 1984. Beeinflussung der biologisch optimalen Temperatur von acid requirements of poultry. Pages 385-404 in: Legehybriden durch die Lufteschwindigkeit. Proceedings of the 4th International Symposium Arch. Exper. Veterinaenned. 38319-326. on Protein Metabolism and Nutrition, European
equations. The predicted values were used in similar calculations as with measured values, in order to estimate ME requirement. Although the predicted values cannot be generalized, the equations demonstrate the pattern of OP, OF, and OE during a laving period. Consequently, the only variables necessary to calculate ME requirement are live weight, age, and amount of eggs produced. Finally, it can be suggested that the proposed method be challenged by a dynamic model of energy metabolism in laying hens, in order to evaluate potential effects of genotype, plan of nutrition, and environmental conditions on the applied constants.
1992 Poultry Science 71509-515
sum of energy required for maintenance and production, by inserting fixed values The different methods used to estimate for the maintenance requirement and an the energy requirement for production can overall efficiency of energy utilization for be classified into two categories: empirical growth and egg production. and factorial methods. Empirical methods For egg production, the efficiency of are based on measurements of animal ME utilization for energy deposition in performance at given levels of energy eggs (Kb) varies between .60 and .85, as intake, and have often been used to reviewed by Chwalibog (1985) and Luiting evaluate energy requirements for egg (1990). This variation is undoubtedly due production. The factorial method is based to a number of genetic, nutritional, and on separation of the metabolic processes environmental factors (Farrell, 1975; Balcontributing to the energy requirement. nave et al, 1978; Rising et al, 1988; Luiting, The energy requirement is calculated as a 1990; Pesti et al., 1990; Spratt et al, 1990), but the main reason is an inconsistency in the Ko estimate, as it includes both the Supported by the Danish Agricultural and Veteri- utilization for energy deposition in protein (Kop) and in fat (Kof), which are not nary Research Council. INTRODUCTION
509
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ABSTRACT Based on balance and respiration measurements with 60 White Leghorns during the laying period from 27 to 48 wk of age, a factorial method for estimating the energy requirement for egg production is proposed. The present experiment showed that the deposition of fat and energy increased during the laying period, but protein deposition slightly decreased. It has been shown that the efficiency of ME utilization for fat energy deposition is higher than for protein energy deposition in the egg. Because the proportions of protein and fat differ during the laying period, and because energy utilization is different between protein and fat, the ME requirement was calculated as the sum of ME for maintenance and the partial requirements for protein, fat, and carbohydrate deposition. For practical applications, functions for prediction of protein (OP), fat (OF), and energy (OE) in eggs during the laying period have been established according to the following model: OP, OF, or OE = a + bl x egg (grams per day) + b2 x age (weeks). The average ME requirement [calculated with either measured or predicted chemical composition, and by applying a constant maintenance requirement of 98 kcal/kg BW 75 and partial efficiencies for energy retention in protein (Kop = .50), fat (Kof = .79), and carbohydrates (Koc = .79)]increased from .26 Meal at 27 wk of age to .29 Meal at 48 wk, corresponding to 5.93 and 6.07 Mcal/kg egg. {Key words: egg composition, energetic efficiency, egg production, requirement, prediction)
CHWALIBOG
510
MATERIALS AND METHODS Sixty White Leghorn hens were measured during a laying period from 27 to 48 wk of age. The hens were kept in the battery cages either singly (12 birds) or 3 hens per cage (48 birds) with an area of 2,100 or 700 cm2 per hen, respectively. The battery cages were adjusted for separate feeding and collection of droppings and eggs. Ambient temperature was maintained at 17 or 21 C, and a constant 17-h lighting was applied. All hens were provided ad libitum access to a commercial diet containing 150 g crude protein and 3.91 Meal gross energy/kg feed. The amount of ME measured from balance experiments was on average 2.76 Mcal/kg feed. The composition of the diet and the chemical analyses are shown in Table 1. The measurements started after a preliminary period of 5 to 7 wk during which the hens were kept under the same conditions as during the experimental time. Each hen or group of hens was
TABLE 1. Feed composition Ingredients and composition Barley Oat Maize Alfalfa meal Meat and bone meal Rshmeal Fat, animal CaCQ3 Nad MnS04 ZnO Ethoxyquin Vitamin mixture1 Chemical composition Dry matter Ash Nitrogen Crude fat Energy, Mcal/kg
Content (g/kg) 608.0 100.0 50.0 70.0 57.0 40.0 30.0 35.0 4.4 5 .1 2 4.8 882.0 865 23.9 72.0 3.94
Supplied in milligrams per kilogram of diet: retinol, 4.61; cholecakiferol, .048; a-tocopherol, 13.44; thiamin, 24; riboflavin, 8.16; nicotinamid, 12.0; glutamic acid, .77; cyanocobalamin, .015; pantothenic acid, 1656; biotin, .072; and choline, 192.0.
measured in eight consecutive balance periods. Each period consisted of 7 days collection of droppings and eggs, and was followed by a 14-day intermediate period. A total of 188 measurements were made. The feed was weighed out for each animal or group of hens for a 7-day period and aliquot samples were taken for chemical analyses. Droppings were collected daily before feeding, and stored in a deepfreezer until the end of a balance period. Eggs were collected daily, weighed, and cooled until each balance period was concluded. After concluding a collection period, droppings were thawed, weighed, mixed, and their energy content was analyzed. Prior to chemical analyses, eggs were boiled, minced, and freezedried. The freeze-dried material was ground in mortars and distributed for chemical analyses of dry matter, ash, nitrogen, fat, and energy. The chemical analyses were done according to standard procedures of the Association of Official Analytical Chemists (1975). Statistical analyses were based on procedures suggested by Gill (1978) and
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equal. For growing animals it is well established that the partial efficiency for protein retention is lower than for fat retention (as reviewed by Klein and Hoffmann, 1989). There is also information that the partial efficiencies of protein and fat deposition in the egg are of the same order of magnitude as the respective values in growing animals (Klein and Hoffmann, 1989; Chwalibog, 1991). Furthermore, the chemical composition of eggs depends on the genetic background and age of the birds (Chwalibog, 1985), and thus the amount of energy deposited in protein and fat will be different during a laying period. Therefore, the objective of the present work was to investigate the partition of energy deposition in the egg during the laying period, and to demonstrate a factorial method in which the partial efficiencies of ME utilization for each component of energy in the egg are considered. Because the amount of protein and fat deposited in eggs during a laying period can be difficult to assess under practical conditions, predictions of egg composition have been developed and applied in energy requirement calculations.
ENERGY REQUIREMENT FOR EGG PRODUCTION
511
TABLE 2. Protein (OP), fat (OF), and energy (OE) content in eggs, during the laying period from 27 to 48 wk of age (x ± SEM) OP
Age (wk) 27 30 33 36 39 42 45 48
OF (g/kg)
25 27 26 23 23 21 21 22
1.11 .99 .80 .85 1.19 1.08 .96 1.45
251 .0176
92 ± 1.18 97 ± .98 97 ± .99 99 ± .99 101 ± 1.43 102 ± 1.61 104 ±1.22 107 ± 1.84 Statistics 13.0 .0001
(Mcal/kg) 1.69 ± .015 1.71 ± .011 1.72 ± .010 1.74 ± .010 1.75 ± .018 1.74 ± .018 1.77 ± .014 1.79 ± .024 4.43 .0001
'Number of measurements.
performed by means of base SAS® software (Ray, 1982). The main effect in the analysis was age of hen. All results were calculated per hen per day. The following terminology was used in the present studies: BW-75 = metabolic body weight; MEm = ME requirement for maintenance; MEo = ME requirement for egg production; MEreq = ME requirement for maintenance and production; OE = energy deposited in eggs; OPE = protein energy deposited in eggs; OFE = fat energy deposited in eggs; OCE = carbohydrate energy deposited in eggs; OP = protein deposited in eggs; OF = fat deposited in eggs; OC = carbohydrate deposited in eggs; Ko = efficiency of ME utilization for OE; Kop = efficiency of ME utilization for OPE; Kof = efficiency of ME utilization for OFE; and Koc = efficiency of ME utilization for OCE.
of eggs divided by the number of days in the collection period, and it varied between 83 and 88%. Egg size increased from about 52 g at an age of 27 wk to 60 g at 48 wk. As demonstrated in Table 2, the amount of protein averaged 131 ± .39 g/kg egg, with values tending to decrease with age. The amount of fat increased from 92 to 107 g/ kg egg, and consequently energy content increased from 1.7 to 1.8 Mcal/kg egg. In both cases the increase was highly significant. The average content of ash was 9 ± .07 and carbohydrates 9 ± .13 g/kg egg. Based on individual determinations (n = 188) of energy content and chemical composition of eggs, estimations of the energetic equivalents (kilocalories) of OP
RESULTS AND DISCUSSION The average BW during the period of laying was 1.680 ± .012 kg (x ± SEM). Generally, all hens showed the same pattern for feed intake, increasing from 95 g at the beginning of the experiment to 125 g by an age of 35 wk, and remaining relatively constant after that time. The course of egg production demonstrated in Figure 1 followed the same pattern for all hens, reaching a plateau of about 50 g/ day at an age of 38 to 40 wk. The laying percentage was calculated as the number
33
36 39 42 Age, weeks
FIGURE 1. Egg production and laying percentage in relation to the age of hens.
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F value Probability
133 ± 134 ± 131 ± 132 ± 131 ± 129 ± 129 ± 130 ±
OE
512
CHWAUBOG TABLE 3. Requirement for metabolizable energy (MEreq), calculated as the sum of ME for maintenance (MEm) and ME for egg production (MEo), and the difference between ME intake (MEi) and MEreq BW
MEm
MEo
MEreq
(wk) 27 30 33 36 39 42 45 48
(kg) 159 1.64 1.64 1.69 1.69 1.71 1.76 1.77 1.68
139 142 142 145 145 146 150 150 145
118 130 129 136 138 137 138 138 133
256 272 271 281 284 284 288 288 278
X
(grams), OF (grams), and OC (grams) were made according to the following regression (with standard errors in parentheses):
MEi (kcal) 257 300 315 345 318 308 301 297 305
Difference between MEi and MEreq 1 28 44 64 34 24 13 9 27
MEo = (OP x 5.8 x 1.99) + (OF x 9.5 x 1.27) + (OC x 4.1 x 1.27), [2]
where MEo is in kalocalories, and OP, OF, and OC are in grams. The values 5.8, 9.5, OE = [5.8 (.12) x OP] + [9.5 (.15) X OF] and 4.1 kcal are energetic equivalents of + [4.1 (.35) x OC], [1] OP, OF, and OC from Regression [1], and the values 1.99 and 1.27 kcal are reciprowhere residual standard deviation (RSD) cals of Kop, Kof, and Koc, corresponding = .73; CV = .87%; and R2 = .997. The to the amount of MEo necessary for parameters obtained were applied to cal- deposition of 1 kcal of OPE, OFE, and culations of energy deposition in egg OCE, respectively. In other words, the protein, fat, and carbohydrates during the MEo was calculated as a sum of ME necessary for deposition of 1 g of protein laying period. As demonstrated in Figure 2, the main (5.8 x 1.99 = 11.5 kcal/g), 1 g of fat (9.5 x energy components in eggs were fat and 1.27 = 12.1 kcal/g), and 1 g carbohydrates protein, which contributed different (4.1 X 1.27 = 5.2 kcal/g) in eggs. The amounts of energy depending on the age calculations of mean values and differof the birds. Thus, at the beginning of the ences between ME intake and requirement laying period the ratio OPE:OE was 46%, and OFE:OE was 51%, but during laying these ratios changed to 42% and 56% for OPE:OE and OFE:OE, respectively, at the DU • OPEOE D 0FE:OE age of 48 wk. The contribution of energy from carbohydrates was on average 2% of 55 n n OE. The requirement of ME for maintenance : r-| and egg production (MEreq = MEm + 50 MEo) was calculated by inserting the values obtained by Chwanbog (1985) with 45 White Leghorns kept singly in battery cages at 17 C. The MEm was calculated as equal to 98 kcal/kg BW-75; the MEo was 27 30 33 36 39 42 45 48 calculated from Kop (.50) and Kof (.79). Age, weeks Furthermore, it was assumed that Koc was the same (.79) as Kof. Subsequently, MEo FIGURE 2. Partition of energy deposited in eggs. was calculated according to the following Values are protein (OPE) and fat (OFE) in relation to formula: die total energy (OE).
IMJII
1i i
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Age
513
ENERGY REQUIREMENT FOR EGG PRODUCTION
[3] 2
where RSD = .25; CV = 3.91%; and R = .930.
5
290 : 280 : 270 : 260 j 250 : 240^
27
30
33 36 39 42 Age, weeks
45
48
FIGURE 3. Requirement of ME calculated from measured egg composition (Function [2] and Table 3) and from predicted values (Function [6]).
OF = -1.14 (.176) + [.101 (.0033) X egg] stant 12.1 was the amount of MEo neces+ [.029 (.0032) X age], [4] sary for deposition of 1 g of fat, multiplied by the predicted fat deposition; and the 2 where RSD = .29; CV = 6.16%; and R = constant 5.2 was the amount of MEo necessary for deposition of 1 g of carbohy.867. drate, multiplied by the average carbohydrate content in eggs. As demonstrated in OE = -B.5 (2.10) + [1.76 (.04) x egg] Figure 3, the differences between MEreq + [.20 (.038) x age] calculated from measured egg composi[5] tion and from predicted values were negligible. On average, the requirement of where RSD = 3.54; CV = 4.21%; and R2 = ME for maintenance and egg production .924. The equations showed very good fit was 256 kcal at 27 wk of age, and 286 at 48 between the applied models and the wk of age, corresponding to 5.92 and 6.07 measured data, with low CV and high R2 Mcal/kg egg. values. Finally, similar calculations of MEreq General Discussion were performed as a sum of MEm and The chemical composition of egg content MEo calculated from predicted values of protein and fat from Regressions [3] and showed a tendency for decreasing OP with [4], and by adding a constant value of 9 g/ age, but OF and OE increased significantly. kg egg for carbohydrate content. The Although there are several measurements computations were accomplished as fol- of egg composition, only a few reports describe the effect of age on egg composilows: tion. The pattern of OP observed in the present experiments is in general agreeMEreq = (98 X kg BW-75) + 11.5 X [(.138 ment with Anderson et ah (1978), and Fisher x egg) - (.0086 x age)] + 12.1 x (1983), who reported a decline in OP over [-1.14 + (.101 x egg) + (.029 x the 1st laying yr. Whether or not age has an age)] + 5.2 x (.009 x egg). influence on OF and OE in eggs, has not [6] been reported in the literature. However, the well-known fact that egg size increases The inserted value of MEm was 98 kcal/ with age supports the present results, as kg BW75; the constant 11.5 was the increases in egg size are directly related amount of MEo (kilocalories) necessary for with increases in OE (Sibbald, 1979). deposition of 1 g of protein, multiplied by Energy partition between OP, OF, and the predicted protein deposition; the con- OC was calculated with the regression
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OP = [.138 (.0018) X egg] - [.0086 (.00238) X age],
300 r requirement, kcal/day
are demonstrated in Table 3. On average, the consumed ME was about 10% higher than the calculated requirement. Because the amount of protein, fat, and energy deposited in eggs can be difficult to assess, the following predictions for OP (grams per day), OF (grams per day), and OE (kilocalories per day) were established based on egg production (grams per day) and age of animals (weeks), (with standard errors in parentheses).
514
CHWALIBOG
that of OFE. In the present calculations it was assumed that Koc = Kof, which may or may not be correct. However, due to very small amount of carbohydrate deposited in eggs, changes in Koc will have negligible influence on the final MEreq. Nevertheless, it has to be emphasized that the presented absolute values of MEm and energy utilization cannot be generalized, as they were obtained under the specific conditions of the experiment. It is likely that MEm and Kop, especially, may be different for other breeds and under different conditions. Even so, the concepts of the equations can be used as a framework for a factorial approach. The advantage of the presented method of calculation is undoubtedly the recognition that the overall utilization of ME for egg production is a less accurate predictor of ME requirement than are the partial efficiencies. Using the same Ko implies that the ratio between OPE and OFE is constant during the laying period, or that Kop = Kof (Chwalibog, 1991). Because, neither of these assumptions is true, as demonstrated in the present paper, the two major components of energy in the egg must be separated. Thus, by applying partial efficiencies, a bias, caused by different chemical composition of eggs during the laying period or due to different genetic and nutritional factors, will be markedly reduced. In the present approach, two major components of energy metabolism (i.e., MEm and MEo) have been taken into account. However, a difference of about 10% between ME intake and MEreq was measured. Part of this difference may be related to changes in body weight. The correction for body weight changes can be achieved from net energy values of body gain and energetic efficiencies of growth, with values reported by Klein and Hoffmann (1989), Spratt et al. (1990), and Chwalibog (1991). Because the method described is based on measurement of the chemical composition of eggs, it is essential to have data for OP and OF during the laying period. These can be difficult to obtain, and therefore the predictions of OP, OF, and OE were developed by regression techniques. The obtained functions showed very good fit between the experimental data and the
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constants obtained in the present experiment. These constant are close to mean enthalpies tabulated by Brouwer (1965). It has been shown in the present paper that increased OE during the laying period was due to increases in OFE, but not in OPE. In the present calculations the values of MEm, Kop, and Kof, obtained from measurements with birds kept singly at ambient temperature of 21C, were incorporated in the calculations applied to the material including hens kept in groups of three per cage, and at 17 C. This may be debatable, as MEm values depend on a number of nutritional and environmental factors, as reviewed by Luiting (1990). However, as discussed by Chwalibog (1985), the use of the same value of MEm can be justified within one breed and for hens kept close to the optimum biological temperature of 19 C (Tzschentke and Nichelmann, 1984). Although different housing may change the energy expenditure for locomotor activity (Madrid et ah, 1981; MacLeod et at, 1982), and thus influence MEm values, it was assumed for the present calculations that those changes would be smaller than the individual variation in MEm. Concerning the partial energetic efficiencies for egg production, there is no information concerning the extent to which they may be influenced by internal and external factors. Klein and Hoffmann (1989) concluded from literature in the last 25 yr that the values of Kof for growing animals lie very close to .8. For Kop the variation is much higher, between .4 and .7, depending on a number of genetic, nutritional, and environmental factors, as well as due to different experimental techniques and methods of calculations (MacLeod and Jewitt, 1988; Chwalibog, 1991). There have been only a few attempts to estimate the partial efficiencies for laying hens. The values inserted in the present calculations are in good agreement with those reported by Hoffmann and Schiemann (1973), who demonstrated nearly similar values for Kof of .74 and slightly lower values for Kop of .44, and are thus of the same order of magnitude as the respective values for energy utilization in growing animals. This also confirms that the energy requirement for OPE is higher than
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515
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Association of Animal Production Publication 31, Clermont-Ferrand, France. Gill,}. L., 1978. Design and Analyses of Experiments in the Animal and Medical Sciences. Vol. 1. The Iowa State University Press, Ames, IA. Hoffmann, L., and R. Schiemann, 1973. Die Verwertung der Futterenergie durch die legende Henne. Arch. Tirernahr. 23:105-132. Klein, M., and L. Hoffmann, 1989. Bioenergetics of protein retention. Pages 404-440 in: Protein Metabolism in Farm Animals. H. D. Block, B. O. Eggum, A. G. Low, O. Simon, and T. Zebrowska, ed. Oxford Scientific Publications, Deutscher Landwirtschaftsverlag, Berlin, Germany. Luiting, P., 1990. Genetic variation of energy partitioning in laying hens: causes of variation in residual feed consumption. World's Poult. Sci. J. 46: 133-152. Madrid, A., P. M. Maiorino, and B. L. Reid, 1981. Cage density and energy utilization. Nutr. Rep. Int. 23: 89-93. MacLeod, M. G., and T. R. Jewitt, 1988. Maintenance energy requirements of laying hens: A comparREFERENCES ison of measurements made by two methods based on indirect calorimetry. Br. Poult. Sci. 29: Anderson, G. B., W. Bolton, R. M. Jones, and M. H. 63-74. Draper, 1978. Effect of age of the laying hen on the composition of the egg. Br. Poult. Sci. 19:741-745. MacLeod, M. G., T. R. Jewitt, J. White, M. Verbrugge, and M. Mitchell, 1982. The contribution of Association of Official Analytical Chemists, 1975. locomotor activity to energy expenditure in the Official Methods of Analysis. 12th ed. Association domestic fowl. Pages 297-300 in: Proceedings of of Official Analytical Chemists, Washington, DC. the 9th Symposium on Energy Metabolism, Balnave, D., D. J. FarreU, and R. B. Cumming, 1978. The European Association of Animal Production minimum metabolizable energy requirement of Publication 29, Lillehammer, Norway. laying hens. World's Poult. Sci. J. 34:149-154. Brouwer, E., 1965. Report of Sub-Committee on Pesti, G. M., E. Thomson, and D. J. Farrell, 1990. Energy exchange of two breeds of hens in respiration Constants and Factors. Pages 441-443 in: Proceedchambers. Poultry Sci. 6958-104. ings of the 3rd Symposium on Energy Metabolism, European Association of Animal Produc- Ray, A. A., 1982. SAS* User's Guide: Statistics. SAS Institute Inc., Cary, NC. tion Publication 11, Troon, Scotland. Chwalibog, A., 1985. Studies on Energy Metabolism in Rising, R., P. M. Maiorino, J. Alak, and B. L. Reid, 1989. Indirect calorimetry evaluation of dietary protein Laying Hens. Statens Husdyrbrugsforseg, and animal fat effects on energy utilization of Beretning 578, Denmark. laying hens. Poultry Sci. 68258-264. Chwalibog, A., 1991. Energetics of Animal Production. Research in Copenhagen, Review and Sugges- Sibbald, I. R., 1979. The gross energy of avian eggs. Poultry So. 58:404-409. tions. Acta Agric. Scand. 41:147-160. Farrell, D. J., 1975. A comparison of the energy Spratt, R. S., H. S. Bayley, B. W. McBride, and S. Leeson, 1990. Energy metabolism of broiler breeder hens. metabolism of two breeds of hens and their cross 1. The partition of dietary energy intake. Poultry using respiration calorimetry. Br. Poult. Sci. 16: ScL 69:1339-1347. 103-113. Fisher, C, 1983. The physiological basis of the amino Tzschentke, B., and M. Nichehnann, 1984. Beeinflussung der biologisch optimalen Temperatur von acid requirements of poultry. Pages 385-404 in: Legehybriden durch die Lufteschwindigkeit. Proceedings of the 4th International Symposium Arch. Exper. Veterinaenned. 38319-326. on Protein Metabolism and Nutrition, European
equations. The predicted values were used in similar calculations as with measured values, in order to estimate ME requirement. Although the predicted values cannot be generalized, the equations demonstrate the pattern of OP, OF, and OE during a laving period. Consequently, the only variables necessary to calculate ME requirement are live weight, age, and amount of eggs produced. Finally, it can be suggested that the proposed method be challenged by a dynamic model of energy metabolism in laying hens, in order to evaluate potential effects of genotype, plan of nutrition, and environmental conditions on the applied constants.