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The chemical composition of the live-weight gain and the performance of growing pigs
Livestock Production Science, 3 (1976) 257--269 257 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
THE CHEMICAL COMPOSITION OF THE LIVE-WEIGHT GAIN AND THE PERFORMANCE OF GROWING PIGS
J. KIELANOWSKI Institute o f Animal Physiology and Nutrition, Jablonna, Warsaw (Poland) (Received November 28th, 1975)
ABSTRACT Kielanowski, J., 1976. The chemical composition of the live-weight gain and the performance of growing pigs. Livest. Prod. Sci., 3: 000--000. Investigations carried out in Poland are reviewed on the crude chemical body composition of growing pigs. The material comprises about 300 analyses of the bodies of females and castrated males, fed on different levels and slaughtered within the live-weight range from 2.5 to about 90 kg. Straight correlations between all body components are high, while partial correlations, with the content of protein held constant, between the body fat and the lean body mass and between the contents of fat and water in the body are very low and insignificant. This leads to the conclusion that in the animals investigated the growth of the lean body was independent of the fat content, the latter being merely a function of the energy surplus given to the animals. Regression equations are quoted that enable the total body composition to be estimated, if the live weight and the content of any individual component, preferably protein, are known. An attempt is also made to demonstrate, by a mathematical model, that the efficiency of feed conversion, as well as the ratio of fat to protein deposited in the growing body, depends mainly on the level of feeding applied and the ability of the animals to deposit protein in their tissues at a faster or slower rate. The practical application of this model is demonstrated, using an example taken from the reports of the Danish progeny testing stations. Assuming that the rate of protein deposition in the body is a highly inheritable trait it is also shown how the genotype and the level of feeding jointly affect the fat to protein ratio in the live-weight gain. INTRODUCTION Data o n the chemical c o m p o s i t i o n of the pig's b o d y were scarce in the literature u n t i l quite r e c e n t l y , a n d o n l y d u r i n g the last decade a c c u m u l a t e d considerably, allowing attempts at general conclusions. Such an attempt, based on Polish investigations and concerning the chemical composition of the l i v e - w e i g h t g a i n , i n r e l a t i o n t o t h e level o f f e e d i n g , r a t e o f p r o t e i n d e p o s i t i o n a n d o t h e r f a c t o r s , is p r e s e n t e d i n t h i s p a p e r . i
THE CHEMICAL COMPOSITION OF THE BODY OF THE GROWING PIG The accuracy of the chemical analysis of the pig's body depends on the
258 ability to produce a homogeneous and fully representative sample of the initial material. Several procedures were developed that accomplish this task satisfactorily. One of them, involving autoclaving (Kotarbifiska, 1971), developed at the Institute of Animal Physiology and Nutrition in Jablonna and applied there for 20 years, allowed results of over 1000 individual analyses to be collected. A b o u t 300 of these, published by Kotarbifiska (1969), were used for the purpose of this paper. The animals investigated (outbred Large White pigs), slaughtered at a live weight from a b o u t 2.5 to 90 kg, derived from nutritional balance trials, in which different feeding levels were applied. Samples for the analyses were taken from the e m p t y body, i.e. from the whole b o d y with the contents of the alimentary tract and of the urinary- and gall-bladder removed. The e m p t y b o d y weight (EBW) was linearly correlated with the live weight (LW) and amounted to 0.95 LW (CV = 1.77 %). In the samples the contents of water (W = EBW minus dry matter), crude protein (P = 6.25 N), crude fat (F, ether extract) and ash (A) were determined. The amounts of all these components increased proportionally to the growing live weight, and this was reflected by their mutual straight correlations, which were positive and high. It was found, however, that partial correlations, with P held constant, between W and F and between the lean b o d y mass (LBM = EBW minus F) and F were negligible (--0.017 and --0.034, respectively). The regression of W on P independent of F (all variables in kg) was: W = 4.43 + (3.00 -+ 0.06) P--(0.01 -+ 0.03) F -+ 1.34
(1)
The multiple correlation was 0.995. Sex differences in this respect were insignificant, and eq. (1), as well as the partial correlations mentioned, was obtained for analyses of the bodies of 190 females and 83 castrated males taken jointly. The animals were slaughtered within the live-weight range from 20 to 92 kg. The relationships shown justify the conclusion that in the material investigated the growth of LBM progressed independently of the content of fat in the body, the latter being solely a function of the energy surplus given to the animals, and this finding contradicts the supposition that fat "replaces" water in the body. Reid (1972), and several other authors quoted in his paper, expressed the chemical c o m p o n e n t s of the b o d y as functions of EBW. Since, however, EBW is equal to the sum of LBM and F, and in Kotarbiflska's material F was independent of the other components, she found it expedient to express W, LBM and A rather as functions of P. The best fitting for W and LBM were functions of a fractional power of P, and for A a simple linear function. Equations proposed by Kotarbiflska and by Reid are presented in Tables I and II. For the sake of comparison in Table I all components are expressed as functions of P, and in Table II as functions of EBW. It was found (Kotarbiflska, 1969; Kielanowski and Kotarbifiska, 1974) that within the same c o n t e n t of P the content of W was highest in males, lower in females and lowest in castrates. These differences, however, were insignificant and might have been due to the average age of animals, which was lowest
259
TABLE I C h e m i c a l c o m p o n e n t s o f t h e e m p t y b o d y o f g r o w i n g pigs, e x p r e s s e d as f u n c t i o n s o f t h e p r o t e i n c o n t e n t (P, kg) Sex
After Kotarbifiska (1969)
N 6 6,~ 6 9 6,9 6,Q 6,Q
104 209 313 104 209 313 -313
W W W LBM LBM LBM F A
= = = = = = = =
After Reid (1972) (recomputed)
Equation
r
4 . 6 9 8 p0-s6s 4.889P°'Sss 4.808P°'S62 5 . 9 1 8 po.sg~ 6.079P°'S~s 6 . 0 1 2 po.s92 0.725P ''35s** 0.189 P
0.999 0.955 0.998 0.999 0.998 0.998 -0.992
--W = 4.633P°'~93 --LBM = 5.842 p0.9,6, F=0.718P ''s'2 A = 0 . 2 1 8 po.936
A b b r e v i a t i o n s : P - p r o t e i n , W - w a t e r , L B M - l e a n b o d y m a s s , . F - fat, A - ash. * L B M c o m p u t e d as a s u m o f P, W a n d A. * * E s t i m a t e d f r o m K o t a r b i f i s k a ' s e q u a t i o n s o n t h e a s s u m p t i o n t h a t w i t h i n t h e live w e i g h t r a n g e f r o m 20 t o 9 0 kg g r o w i n g pigs d e p o s i t t w i c e as m u c h f a t as p r o t e i n , a n d t h a t t h e y c o n t a i n initially 3.0 kg P a n d 3.2 kg F.
in boars and greatest in castrates. The influence of age on the c o n t e n t of W was confirmed by Kotarbifiska {1969), who found highly significant partial correlations with P held constant between the age and W. The coefficient obtained were --0.385 for gilts, --0.540 for castrates and --0.453 within sexes. According to Kotarbihska's equation (Table I) the ratio of W to P equals 4.808 p-0.13s, and its value decreases infinitely with growing P. It is reasonable to assume, however, that this ratio approaches a limit, and for this rea-
T A B L E II C h e m i c a l c o m p o n e n t s o f t h e e m p t y b o d y o f g r o w i n g pigs, e x p r e s s e d as f u n c t i o n s o f t h e e m p t y b o d y w e i g h t (EBW, kg) Sex
After Reid ( 1 9 7 2 )
N 6,9 6,9 6,Q 6,9 6,9
714 -714 714 714
W LBM P F A
= = = = =
After Kotarbifiska (1969) ( r e c o m p u t e d ) **
Equation
r
0.889 1.076 0.158 0.044 0.039
0.996 -0.996 0.988 0.979
E B W °'s67 EBW °'ssg* E B W °'9~1 E B W 1"4's E B W °'9°s
A b b r e v i a t i o n s a n d r e m a r k s as in T a b l e I.
W LBM P F A
= = = = =
0.959 1.134 0.154 0.057 0.029
EBW ° ' s ~ E B W °'s96 E B W l"°°s E B W ~'3~4 EBW l"°°s
260 son the expression of W as a fractional power of P could n o t be regarded as satisfactory. It seems t h a t an equation of the following type would be more suitable: W = (cl +c2 e-c~P)P
(2)
The ratio of W to P c o m p u t e d from this equation approaches cl + c2 for very low, and cl for very high values of P. The constant c2 expresses thus the difference between the possibly highest and possibly lowest values of the W to P ratio, and the negative constant c3 is an expression of the rate of decrease of this ratio with increasing P. It can be assumed that the closer this ratio is to the constant c l , the more mature is the animal somatically. If it is so, then the higher is the negative value of c3, the faster is the rate of maturing. For example, in pigs weighing 90 kg (assumed P = 13.5 kg) values of c3 equal to --0.10, --0.15 and --0.20 correspond to about 74, 87 and 93% " m a t u r i t y " , expressed in percents of c2 depleted. For an illustration an equation has been c o m p u t e d fitting Kotarbifiska's (1969) data (W and P in kg): W = (3.09 + 2.13 e -0.16P) p
(2a)
It seems that sex differences are mainly due to different values of c~, and that c~ increases in response to selection for meatiness. This could be perhaps explained by the fact that the W to P ratio is higher in muscles than in total EBW. The equations listed in Tables I and II allow the crude chemical composition of the pig's body to be estimated, whenever P and EBW are known. They also permit estimation of the increments of W, A and P in body gain, when the increment of P and the initial body composition are known. In individual cases a strict reliance on these estimates can be misleading because of the variability of animals, and the parameters obtained for one breed or strain may n o t be applicable to others. However, initial observations at the Institute in Jablonna show t h a t within the fiducial limits the equations obtained for Large White pigs fit a population of the Norwegian Landrace, and t h e y fit also rather closely data on the composition of the pig's body published by Just Nielsen (1970). It should be remembered t h a t the meaning of the chemical body constituents discussed in this paper is vaguely defined. The multiplier 6.25 applied widely for computing body protein is not based on adequate experimental data. Moreover, unpublished data from the Institute in Jablonna indicate that the proportion of amino N in total N increases in the b o d y as the animals grow, being 78 and 89% in pigs weighing 10 and 100 kg, respectively. The identification of the ether extract with body fat is also purely arbitrary and in more detailed investigations structural and depot fat should be considered separately. Similar remarks could be made concerning the meaning of body water and ash. Nevertheless, apart from these reservations, the equations presented allow the course of changes of the chemical body composition of growing pigs to be outlined in general terms, creating a starting point for more detailed research.
261
INCREMENTS OF THE CHEMICAL BODY COMPONENTS AND THE PERFORMANCE OF A GROWING PIG An a t t e m p t to deduce the relationships between the increments of the chemical b o d y components and the measures of performance such as the daily live-weight gain and the feed conversion ratio was made in a paper published a decade ago (Kielanowski, 1966), and since adequate experimental data were lacking, this paper had to be based on rather roughly estimated values. The principles adopted were very simple. It has been postulated first that the intake (E i ) of metabolizable energy (ME) is equal to the sum of a c o m p o n e n t proportional to the live weight, called energy cost of maintenance (Em), a second component, obtained by multiplying the a m o u n t of protein deposited (A p) by the constant energy cost of unitary protein deposition (Ep), and a third component, obte~ned by multiplying the a m o u n t of fat deposited (A F ) b y the constant energy cost of unitary fat deposition (Ef). This could be expressed by the equation: El=Era +Ep A p+EfA
F
(3)
The value of Ef, consistent with biochemical deductions, was found to be nearly constant in energy balance trials (Schiemann et al., 1961), and the maintenance requirement of growing pigs was shown by Breirem (1939) to be the function of a fractional power of their live weight. The constancy of Ep, however, had to be assumed arbitrarily. The second postulate adopted was that the live weight gain (A LW) could be regarded as the sum of AF and of the product of Ap and the ratio (Q) of the lean body mass to A p, also arbitrarily assumed to be constant for a constant live weight range. Hence: A LW=AF+QAp
(4)
From equations (2) and (3) the two following ones could be obtained easily: F C = E i E f / [ E i -- E m + (EfQ -- Ep)A P]
(5)
AP = [E m + (Ef -- FC)A L W ] / ( E f Q - - E p )
(6)
In eq. (5) FC denotes the feed conversion ratio, i.e. the ratio of E i to A LW. If Ef and Ep, as well as E m and Q in animals growing over the same live weight range are ~ssumed constant then eq. (5) expresses FC as a function of Ei and A P, i.e. a function of the level of feeding and the protein deposition. In order to substantiate these deductions more experimental evidence was needed. As discussed previously, Kotarbifiska's investigations clarified the question of the LBM to P ratio and showed that it did n o t depend in practice on the fat c o n t e n t in the body. The applicability of eq. (4) was thus supported. Further, the suitability of eq. (3) was confirmed experimentally (Kotarbifiska, 1969) by the very close fit (T = 0.991) of the following equation,
262 obtained for 54 castrates growing from 30 to 90 kg (E i expressed in kcal ME, P and A F in g): E i = 101.5 + (16.0+ 1 . 9 ) ~ P + (13.0 + 0.9) A F_+ 4.9
(3a)
All this demonstrated that the approach adopted in the paper discussed was acceptable. The variables in eq. (3a) were taken as daily averages per unit (LW kg) °'75 , and so the regression constant corresponded to the maintenance requirement per kg °" 7s metabolic weight. It is worth mentioning that studies of Kotarbifiska's materials showed that the best possible fit was obtained b y raising LW to the power 0.734, n o t differing significantly from 0.75. Within the live weight range from 20 to 100 kg the maintenance requirement c o m p u t e d as 100 kcal (418 kJ) ME per kg °'Ts metabolic weight corresponds to that derived from Breirem's (1939) equation and is consistent with values obtained b y several other authors (Hoffmann et al., 1971; Verstegen et al., 1973). The regression coefficient for A P in eq. (3a) is an estimate of Ep. Several estimates of this value obtained later b y various authors for pigs and other animals were discussed in detail elsewhere (Kielanowski, 1976), and a hypothesis was proposed explaining the discrepancy between all these estimates and the energy cost of protein synthesis deduced biochemically. It was assumed that Ep consists of the cost of synthesis of protein deposited plus an additional increase of heat production correlated with A P, and that this increase results from protein turnover and/or endocrine factors, stimulating/x p and heat production simultaneously. Further investigations of this problem are desirable and should t h r o w more light on the causes of the rather high variability of experimental estimates of Ep, ranging for pigs from a b o u t 11.5 kcal ME/g in very y o u n g animals to 16.0 kcal ME/g in older ones. Thorbek (1970) in experiments with pigs weighing from 20 to 90 kg obtained an average estimate of a b o u t 13 kcal ME/g, n o t differing significantly from the estimate obtained from eq. (3a). The value of Ef estimated in pigs statistically, measured in respiration trials or deduced biochemically amounts consistently to a b o u t 13 kcal ME/g. If the same value is chosen as the unitary energy cost of protein deposition, Ep equals Ef, and this simplifies calculations. PRACTICAL CONSIDERATIONS The practical application of the model expressed by equations (3), (4), (5) and (6) can be demonstrated by the example of an annual report of the Danish progeny testing stations (Clausen et al., 1971). It has been assumed for this purpose that the average dally E m of pigs growing from 25 to 90 kg is 2.07 Mcal ME (0.1 Mcal per kg °'Ts metabolic weight), and the average LBM to P ratio in the e m p t y - b o d y gain is 4.3. It has been assumed also that the total e m p t y - b o d y gain is 6 ! . 7 5 kg (0.95 of the live-weight gain), and that 1 Scandinavian feed unit (SFU~ is equal to 3 Mcal ME. In agreement with previous remarks Ep and Ef have been assumed equal and amounting to 13 Mcal
263 ME/kg. All these values have been substituted for symbols in the basic equations. Data on FC and the average daily gain (lwg), as listed in the Danish reports, now allow the total and daily gains of P and F for each tested group of pigs to be computed. As an example, the equation for computing the total gain of P is given (FC expressed in Mcal/kg, and lwg in kg) : AP =
2.07 (65/lwg) + ( 1 2 . 3 5 - - F C ) 65
(6a)
42.9
In the report quoted the average FC was 2.88 SFU/kg and the average lwg was 0.686 kg, while in the most and least efficient groups they were 2.66 SFU/kg and 0.758 kg, and 3.44 SFU/kg and 0.565 kg, respectively. The computations showed t h a t this corresponded to the estimated daily gains of 108 g P and 189 g F on average, 125 g P and 181 g F in the best, and 75 g P and 214 g F in the worst group. The estimated difference in protein deposition between the best and the worst group is compatible with the results of actual N balance trials and offers the most probable explanation of the difference in their performance, as manifested by FC and lwg. The supposition that the different performances were due to differences in Em or Q, assumed somewhat arbitrarily as constant, is much less probable. If the different performances were caused by different Era, with the rate of P deposition held constant, the average E m should be about 1 Mcal in the best and 3 Mcal in the worst group. Similarly, if a different Q were the only reason, it should be about 5.1 in the best and 3.5 in the worst group, and such great differences in
SF c 3.! 3.4. 3.3" 3.2. 3.1 3.0 2.9-
2.5
~
2.8-
2.0
2.71.5 o'.s
o.8 '
0.7 '
o .'a
kq/da y
Fig.1. Curves corresponding to the low, medium and high chemical fat to protein ratio in the live-weight gain of pigs growing from 25 to 90 kg, in relation to the feed conversion ratio (Scand. feed units per kg gain) and the average daily live-weight gain (kg/day). The dots represent the performance of groups taken randomly from a report of Danish progeny testing stations (Clausen et al., 1971).
264
E m or Q are out of the question. The level of feeding was n o t very variable. It can be concluded, therefore, that factors other than the rate of protein deposition could have had only a slight modifying influence on the performance. In order to verify the model discussed with regard to carcass quality, the estimated total AP was correlated with the area of the longissimus dorsi cross section. For this purpose data for 46 groups were taken from a randomly chosen page in the quoted Danish report (Clausen et al., 1971, p. 75). The highly significant correlation was 0.475, i.e. very similar to that found by Babatunde et al. (1966) for the body protein actually determined. The ratio of total fat to protein deposited can be regarded as an index of carcass desirability, and it can be assumed that values of this ratio amounting to 2.5, 2.0 and 1.5 correspond to carcasses of poor, average and excellent quality, respectively. In Fig.1 lines are drawn depicting these values, in relation to FC and lwg, and test groups, taken from the same page of the Danish report are marked by dots. It can be seen that in most groups the estimated fat to protein ratio is between 2.0 and 1.5, in several groups it is less than 1.5, and in two groups about 2.5. In doubtful cases the equations proposed can help to classify the group performance, as judged by FC and lwg. For example, among the groups considered there was one with FC = 2.79 SFU/kg and lwg = 0.678 kg, and another with FC = 2.91 SFU/kg and lwg = 0.704 kg. It is difficult at first sight to decide which should be valued higher, the greater daily gain or the better feed conversion. By means of the equations, however, it can be c o m p u t e d that in the group with the lower gain the estimated daily protein deposition was about 111 g and the ratio of fat to protein deposited was about 1.5. It should be classified higher, therefore, than the other group, for which these values were about 108 g and 1.9. Such classifications can be useful, particularly in the case of comparing sire averages. It is obvious that all these estimates should n o t be taken at their face value. The constants assumed, though realistic and based on ample e x p e r i m e n t a l evidence, were chosen rather arbitrarily, and their values most suitable for the Danish stations could be slightly different. Even if it were so, however, the new and maybe more accurate constants would result in shifting the estimates more or less parallel in one or the other direction, but the ranking of groups would probably remain unchanged. Duniec et al. (1968) found that in pigs, which after reaching a weight of 30 kg were fed for 84 days on equal rations increased gradually t h r o u g h o u t the experiment, the rate of protein deposition actually determined was highly correlated with FC (r = --0.922) and with lwg (r = 0.869). Duniec et al. also found that the protein c o n t e n t of the e m p t y body was highly correlated with the a m o u n t of dissectable meat in the primal cuts (r = 0.853). The rate of protein deposition, therefore, should be considered the most important factor determining the performance of growing pigs, as far as both the feed conversion and the carcass quality are concerned. Feed conversion and the daily gain were shown to be highly inheritable. For example, Jonsson and
265 King (1962) estimated the heritabilities of these traits as 0.48 and 0.45, respectively. Both these traits, as demonstrated in this paper, depend predominant. ly on the rate of protein deposition, which, therefore, is most probably also highly inheritable. Fig.2 gives an example of the genotype--environment interaction. The " g e n o t y p e " is represented by the average rate of protein deposition, the "env i r o n m e n t " by the average level of feeding, and the carcass quality is characterized again by the fat to protein ratio. It can be seen that carcasses of a fair quality can be obtained with a wide range of " g e n o t y p e s " , provided a suitable level of feeding is applied. It would hardly be possible, however, to obtain gains with the fat to protein ratio of 1.5 or less, if the pigs were unable to deposit more than 90 g protein daily, and in pigs that deposit 130 g or more the fat to protein ratio will be always low, even if they are fed ad libitum. The picture presented in Fig.2 was drawn on the loose assumption that the rate of protein deposition is n o t influenced by the quality and level of nutrition. However, it is well known that until a certain plateau is reached, N balance depends strictly on the a m o u n t and quality of protein in the ration, and pigs in which the protein deposition is restricted by nutritional factors will behave as those in which the genotype sets the limit. It is also
2.2,4
2.1,
2,0,
/
1.9"
1.8'
o . o. s
J
o.12 o.~4 kq/d a y .~ o 9 . o.lo . o i l . . . o.~3 Fig.2. Lines representing several chemical fat to protein ratios in the live-weight gain of pigs growing from 25 to 90 kg, in relation to the average daily protein deposition (kg/day) and the average daily feed intake (Scand. feed units/day).
266
known that even when the feed protein supply is adequate and the level of feeding is low, supplements of energy to the ration result in an increased N balance. The rate of protein deposition can be modified also by other factors, e.g. compensatory growth (Kielanowski, 1967), feed additives, such as copper sulphate (Braude, 1965) and probably by the use of anabolizers. Nevertheless, Fig.2 can be understood as a fair illustration of the way in which the combined effect of the level of feeding and the rate of protein deposition, in practice depends mainly on the genotype. The model discussed can also be useful for interpreting feeding trials. The partial derivatives of eq. (5} with respect to Ei and to AP indicate that an increment of Ei results in an increase, and an increment of Ap in a decrease of FC. Thus, for example, if in a feeding trial a decrease of the feed intake did not result in an improvement of FC, it is an indication that the protein deposition must have declined. COROLLARY
The knowledge of the course of changes in the chemical b o d y composition of growing pigs has helped to demonstrate the main physiological factors responsible for the quantitative and qualitative results of pig production. This has made it possible to explain more explicitly than hitherto the effects of various treatments applied to pigs and even to predict these effects, and on the foundation of this newly acquired knowledge practical pig growth models could be constructed {Cop, 1974; Whittemore and Fawcett, 1974). Moreover, the way has been opened for studying comprehensively the growth response to hereditary and environmental factors, as well as for investigating the m o d e of action of physiological agents, such as hormones and feed additives. The crude composition of the b o d y presents only a framework, which should be filled up with more detailed analyses. The relative amounts of different nitrogenous c o m p o u n d s of the b o d y certainly change depending on the age and size of the animals and possibly also on their nutrition, and this could be related to the utilization of feed protein. For example, in piglets nearly 90% of the digested N was recovered in the growing tissues (Braude et al., 1970; Lassota, 1967), whereas in older pigs protein utilization seldom exceeds 40%. It can be assumed that the very high protein utilization in piglets is connected with the rapid multiplication of nuclei, while in older animals the protein deposition is predominantly an effect of cell hypertrophy, and this could be studied by investigating the DNA to protein ratio. More sophisticated data on other constituents of the body, and, particularly, on the metabolism and variability of the content of b o d y water are desirable, and all this detailed information could be built into a reference system of the kind similar to that described in this paper.
267
ACKNOWLEDGEMENTS
The author is greatly indebted to Dr. Maria Kotarbiflska, Professor Zofia Osiflska and Dr. A. Ziolecki for reading the manuscript and for advice. REFERENCES Babatunde, G.M., Pond, W.O., Van Vleck, L.D., Kroening, G.H., Reid, J.T., Staufer, J.R. and Wellington, G.H., 1966. Relationships among some physical and chemical parameters of full- versus limited-fed Yorkshire pigs slaughtered at different live weights. J. Anita. Sci., 25: 526--531. Braude, R., 1965. Copper as a growth stimulant in pigs. In: Trans. Syrup. Cuprum Pro Vita, Vienna, pp. 55--66. Braude, R., Mitchell, K.G., Newport, M.J. and Porter, J.W.C., 1970. Artificial rearing of pigs. Br. J. Nutr., 24: 501--516. Breirem, K., 1939. Der Energieumsatz bei den Schweinen. Tierern~hrung, 11: 487--528. Clausen, H., N~rtoft Thomson, R., Pedersen, O.K., Busk, H. and Christensen, A., 1971. 59. Beretning om Sammenlignende Fors~g med Svin. 390. Beretning fra Fors~gslaboratoriet, K~bbenhavn, 163 pp. CSp, W.A.C., 1974. Protein and fat deposition in pigs in relation to body weight gain and feeding level. H. Veenman en Zonen B.V., Wageningen, 74 pp. Duniec, H., Kielanowski, J. and Osiflska, Z., 1968. The method of pig progeny testing applied in Poland. Paper presented at the E.A.A.P. session of the Commission on Pig Production, Dublin, 1968 (mimeographed). Hoffmann, L., Schiemann, R. and Jentsch, W., 1971. Energetische Verwertung der N~ihrstoffe in Futterrationen. In: R. Schiemann (Editor), Energetische Futterbewertung und Energienormen. VEB Deutscher Landwirtschaftsverlag, Berlin, pp. 118--167. Jonsson, P. and King, J.W.B., 1962. Sources of variation in Danish Landrace pigs at progeny testing stations. Acta Agric. Scand., 12: 68--80. Just Nielsen, A., 1970. Alsdige foderrationers energetiske vaerdi til vuekst hos svin belyst ved forskellig metodik. Frederiksberg Bogtrykkeri, K~bbenhavn, 212 pp. Kielanowski, J., 1966. Conversion of energy and the chemical composition of gain in bacon pigs. Anim. Prod., 8: 121--128. Kielanowski, J., 1967. Efficiency of energy utilisation in growing pigs. In: Report of Proc. and Invited Papers, 9th Intern. Congress Anita. Prod., Edinburgh, 1966. Oliver and Boyd, Edinburgh, pp. 212--224. Kielanowski, J., 1976. Energy cost of protein deposition. In: D.J.A. Cole, K.N. Boorman, P.J. Buttery, D. Lewis, R.J. Neale and H. Swan (Editors), Protein Metabolism and Nutrition, E.A.A.P. Publ. No. 16, Butterworths, London--Boston, pp. 207--215. Kielanowski, J. and Kotarbiflska, M., 1974. Chemical composition and energy value of the live-weight gain in growing pigs. In: K.H. Menke, H.-J. Lantzsch and J.R. Reichl (Editors), 6th Symposium on Energy Metabolism of Farm Animals, Universit~it Hohenheim, Dokumentationsstelle, Stuttgart, pp. 165--168. Kotarbihska, M., 1969. Badania nad przemiana energii u rosnacych gwifl. Instytut Zootechniki, Wydawnictwa Wlasne, Nr 238, Wroclaw, pp. 68. Kotarbiflska, M., 1971. The chemical composition of the body in growing pigs. Rocz. Nauk rol., B-93-1: 129--135. Lassota, L., 1967. Utilization of feed protein in baby pigs as influenced by addition of lactose. Acta Universitatis Agriculturae, Brno, XXXVI, 3: 397--402. Reid, J.T., 1972. Body composition of animals: interspecific sex and age peculiarities, and the influence of nutrition, In: L.S. Spildo, T. Homb and H. Hvidsten (Editors), Fest-skrift til Knut Breirem. Mariendals Boktrykkeri A.S., Gj~bvik, pp. 213--238.
268
Schiemann, R., Hoffmann, L. and Nehring, K., 1961. Die Verwertung reiner N~ihrstoffe. 2. Mitteilung. Arch. Tierern~hr., 11: 253--283. Thorbek, G., 1970. The utilization of metabolizable energy for protein and fat gain in growing pigs. In: A. Schiirch and C. Wenk (Editors), 5th Symposium on Energy Metabolism of Farm Animals, Juris Druck + Verlag, Zurich, pp. 129--] 32. Verstegen, M.W.A., Close, W.H., Start, I.B. and Mount, L.E., 1973. The effect of environmental temperature and plane of nutrition on heat loss, energy retention and deposition of protein and fat in groups of growing pigs. Br. J. Nutr., 30: 21--35. Whittemore, C.T. and Fawcett, R.H., 1974. Model responses of the growing pig to the dietary intake of energy and protein. Anim. Prod., 19: 221--231. Rt~SUMI~ Kielanowski, J., 1976. Composition chimique du gain de poids vif et performance du porc en croissance. Livest. Prod. Sci., 3 : 257--269 (en anglais). Le texte expose les recherches effectu~es en Pologne sur la composition chimique du corps du porc en eroissance. Elle a ~t~ ~tudi~e sur pros de 300 porcs, femelles et m~les castr~s, qui ont ~t~ aliment~s suivant diff~rents niveaux et abattus ~ des poids couvrant l'intervalle de 2,5 ~ 90 kg. Les correlations directes entre t o u s l e s composants de l'organisme sont ~lev4es tandis qu'~ teneur en prot~ines maintenue constante, les correlations partielles entre la graisse corporelle et la masse corporelle maigre et entre les teneurs en graisse et en eau, sont tr~s faibles et non significatives. On peut en conclure que, chez les animaux ~tudi~s, la croissance de la masse maigre a ~t~ ind~pendante de celle de la teneur en graisse, cette derni~re ~tant simplement la consequence du surplus d'~nergie distribu~ aux animaux. Des ~quations de r~gression permettent d'~valuer la composition chimique totale du corps lorsque on conn~it le poids vif et la teneur en un seul des composants, les prot~ines de preference. On essaie ~galement de d~montrer, au moyen d'un module math~matique, que l'efficaeit~ de l'utilisation des aliments, ainsi que le rapport entre graisse et prot~ines d~pos~es dans le corps en croissance, d~pendent surtout du plan d'alimentation et de la capacit~ de l'animal ~ d~poser des prot~ines dans ses tissus fi une vitesse plus ou moins grande. L'application pratique de ce module est illustr~e par un exemple tir~ des rapports des stations de testage danoises. En supposant que la vitesse ~ laquelle les prot~ines se d~posent dans le corps est un caract~re hautement h~ritable, on montre c o m m e n t le g~notype et le plan d'alimentation influencent conjointement la proportion graisse/prot~ine dans le gain de poids vif. KURZFASSUNG Kielanowski, J., 1976. Die chemische Zusammensetzung des Zuwachses und die Mastleistung wachsender Schweine. Livest. Prod. Sci., 3 : 2 5 7 - - 2 6 9 (in Englisch). Die in Polen durchgefiihrten Untersuchungen iiber die chemische Zusammensetzung des KSrpers yon wachsenden Schweinen wurden geschildert. Den Berechnungen lagen etwa 300 KSrperanalysen yon unterschiedlich gefiittertenJungsauen und Kastraten, die beim 2.5 bis etwa 90 kg Lebendgewicht geschlachtet worden waren, zurgrunde. Die einfachen Korrelationen zwischen allen chemischen Bestandteilen waren hoch, die partiellen Korrelationen dagegen, bei konstantem Eiweissgehalt, zwischen d e m Fettgehalt und der fettfreien KSrpersubstanz, sowie d e m Fett- und Wassergehalt waren sehr niedrig und nicht signifikant. Daraus ergibt sich, dass in dem untersuchten Tiermaterial das Wachstum der fettfreien KSrpersubstanz unabh~ingig vom Fettgehalt verlief und dass der Fettgehalt lediglich als eine Funktion des Energieiiberschusses in den Futterrationen zu betrachten sei. Regressionsgleichungen wurden vo~gelegt, welche eine Seh~itzung der gesamten chemi-
269
schen KSrperzusammensetzung ermSglichen, wenn das Lebendgewicht sowie der Gehalt an einem einzigen Bestandteil, am zweckm/issigsten an Roheiweiss, bekannt sind. Es wurde weiter an einem mathematischen Modell veranschaulicht, dass die Futterausnutzung sowie das Fett-Eiweissverh~iltnis in der K~Srperzunahme haupts~chlich yon dem Fiitterungsniveau und der Kapazit~it der Tiere t~iglich mehr oder weniger Eiweiss abzulagern abh~ingen. Die praktische Anwendung dieses Modells wurde am Beispiel yon Angaben aus einem Bericht der d~inischen Schweinepri~fungsstationen dargestellt. Eine hohe Vererblichkeit der Eiweissablagerungsrate voraussetzend wurde ferner gezeigt, wie sich der Genotyp gemeinsam mit dem Fiitterungsniveau auf das Fett-Eiweissverh~ltnis des Zuwachses auswirkt.
THE CHEMICAL COMPOSITION OF THE LIVE-WEIGHT GAIN AND THE PERFORMANCE OF GROWING PIGS
J. KIELANOWSKI Institute o f Animal Physiology and Nutrition, Jablonna, Warsaw (Poland) (Received November 28th, 1975)
ABSTRACT Kielanowski, J., 1976. The chemical composition of the live-weight gain and the performance of growing pigs. Livest. Prod. Sci., 3: 000--000. Investigations carried out in Poland are reviewed on the crude chemical body composition of growing pigs. The material comprises about 300 analyses of the bodies of females and castrated males, fed on different levels and slaughtered within the live-weight range from 2.5 to about 90 kg. Straight correlations between all body components are high, while partial correlations, with the content of protein held constant, between the body fat and the lean body mass and between the contents of fat and water in the body are very low and insignificant. This leads to the conclusion that in the animals investigated the growth of the lean body was independent of the fat content, the latter being merely a function of the energy surplus given to the animals. Regression equations are quoted that enable the total body composition to be estimated, if the live weight and the content of any individual component, preferably protein, are known. An attempt is also made to demonstrate, by a mathematical model, that the efficiency of feed conversion, as well as the ratio of fat to protein deposited in the growing body, depends mainly on the level of feeding applied and the ability of the animals to deposit protein in their tissues at a faster or slower rate. The practical application of this model is demonstrated, using an example taken from the reports of the Danish progeny testing stations. Assuming that the rate of protein deposition in the body is a highly inheritable trait it is also shown how the genotype and the level of feeding jointly affect the fat to protein ratio in the live-weight gain. INTRODUCTION Data o n the chemical c o m p o s i t i o n of the pig's b o d y were scarce in the literature u n t i l quite r e c e n t l y , a n d o n l y d u r i n g the last decade a c c u m u l a t e d considerably, allowing attempts at general conclusions. Such an attempt, based on Polish investigations and concerning the chemical composition of the l i v e - w e i g h t g a i n , i n r e l a t i o n t o t h e level o f f e e d i n g , r a t e o f p r o t e i n d e p o s i t i o n a n d o t h e r f a c t o r s , is p r e s e n t e d i n t h i s p a p e r . i
THE CHEMICAL COMPOSITION OF THE BODY OF THE GROWING PIG The accuracy of the chemical analysis of the pig's body depends on the
258 ability to produce a homogeneous and fully representative sample of the initial material. Several procedures were developed that accomplish this task satisfactorily. One of them, involving autoclaving (Kotarbifiska, 1971), developed at the Institute of Animal Physiology and Nutrition in Jablonna and applied there for 20 years, allowed results of over 1000 individual analyses to be collected. A b o u t 300 of these, published by Kotarbifiska (1969), were used for the purpose of this paper. The animals investigated (outbred Large White pigs), slaughtered at a live weight from a b o u t 2.5 to 90 kg, derived from nutritional balance trials, in which different feeding levels were applied. Samples for the analyses were taken from the e m p t y body, i.e. from the whole b o d y with the contents of the alimentary tract and of the urinary- and gall-bladder removed. The e m p t y b o d y weight (EBW) was linearly correlated with the live weight (LW) and amounted to 0.95 LW (CV = 1.77 %). In the samples the contents of water (W = EBW minus dry matter), crude protein (P = 6.25 N), crude fat (F, ether extract) and ash (A) were determined. The amounts of all these components increased proportionally to the growing live weight, and this was reflected by their mutual straight correlations, which were positive and high. It was found, however, that partial correlations, with P held constant, between W and F and between the lean b o d y mass (LBM = EBW minus F) and F were negligible (--0.017 and --0.034, respectively). The regression of W on P independent of F (all variables in kg) was: W = 4.43 + (3.00 -+ 0.06) P--(0.01 -+ 0.03) F -+ 1.34
(1)
The multiple correlation was 0.995. Sex differences in this respect were insignificant, and eq. (1), as well as the partial correlations mentioned, was obtained for analyses of the bodies of 190 females and 83 castrated males taken jointly. The animals were slaughtered within the live-weight range from 20 to 92 kg. The relationships shown justify the conclusion that in the material investigated the growth of LBM progressed independently of the content of fat in the body, the latter being solely a function of the energy surplus given to the animals, and this finding contradicts the supposition that fat "replaces" water in the body. Reid (1972), and several other authors quoted in his paper, expressed the chemical c o m p o n e n t s of the b o d y as functions of EBW. Since, however, EBW is equal to the sum of LBM and F, and in Kotarbiflska's material F was independent of the other components, she found it expedient to express W, LBM and A rather as functions of P. The best fitting for W and LBM were functions of a fractional power of P, and for A a simple linear function. Equations proposed by Kotarbiflska and by Reid are presented in Tables I and II. For the sake of comparison in Table I all components are expressed as functions of P, and in Table II as functions of EBW. It was found (Kotarbiflska, 1969; Kielanowski and Kotarbifiska, 1974) that within the same c o n t e n t of P the content of W was highest in males, lower in females and lowest in castrates. These differences, however, were insignificant and might have been due to the average age of animals, which was lowest
259
TABLE I C h e m i c a l c o m p o n e n t s o f t h e e m p t y b o d y o f g r o w i n g pigs, e x p r e s s e d as f u n c t i o n s o f t h e p r o t e i n c o n t e n t (P, kg) Sex
After Kotarbifiska (1969)
N 6 6,~ 6 9 6,9 6,Q 6,Q
104 209 313 104 209 313 -313
W W W LBM LBM LBM F A
= = = = = = = =
After Reid (1972) (recomputed)
Equation
r
4 . 6 9 8 p0-s6s 4.889P°'Sss 4.808P°'S62 5 . 9 1 8 po.sg~ 6.079P°'S~s 6 . 0 1 2 po.s92 0.725P ''35s** 0.189 P
0.999 0.955 0.998 0.999 0.998 0.998 -0.992
--W = 4.633P°'~93 --LBM = 5.842 p0.9,6, F=0.718P ''s'2 A = 0 . 2 1 8 po.936
A b b r e v i a t i o n s : P - p r o t e i n , W - w a t e r , L B M - l e a n b o d y m a s s , . F - fat, A - ash. * L B M c o m p u t e d as a s u m o f P, W a n d A. * * E s t i m a t e d f r o m K o t a r b i f i s k a ' s e q u a t i o n s o n t h e a s s u m p t i o n t h a t w i t h i n t h e live w e i g h t r a n g e f r o m 20 t o 9 0 kg g r o w i n g pigs d e p o s i t t w i c e as m u c h f a t as p r o t e i n , a n d t h a t t h e y c o n t a i n initially 3.0 kg P a n d 3.2 kg F.
in boars and greatest in castrates. The influence of age on the c o n t e n t of W was confirmed by Kotarbifiska {1969), who found highly significant partial correlations with P held constant between the age and W. The coefficient obtained were --0.385 for gilts, --0.540 for castrates and --0.453 within sexes. According to Kotarbihska's equation (Table I) the ratio of W to P equals 4.808 p-0.13s, and its value decreases infinitely with growing P. It is reasonable to assume, however, that this ratio approaches a limit, and for this rea-
T A B L E II C h e m i c a l c o m p o n e n t s o f t h e e m p t y b o d y o f g r o w i n g pigs, e x p r e s s e d as f u n c t i o n s o f t h e e m p t y b o d y w e i g h t (EBW, kg) Sex
After Reid ( 1 9 7 2 )
N 6,9 6,9 6,Q 6,9 6,9
714 -714 714 714
W LBM P F A
= = = = =
After Kotarbifiska (1969) ( r e c o m p u t e d ) **
Equation
r
0.889 1.076 0.158 0.044 0.039
0.996 -0.996 0.988 0.979
E B W °'s67 EBW °'ssg* E B W °'9~1 E B W 1"4's E B W °'9°s
A b b r e v i a t i o n s a n d r e m a r k s as in T a b l e I.
W LBM P F A
= = = = =
0.959 1.134 0.154 0.057 0.029
EBW ° ' s ~ E B W °'s96 E B W l"°°s E B W ~'3~4 EBW l"°°s
260 son the expression of W as a fractional power of P could n o t be regarded as satisfactory. It seems t h a t an equation of the following type would be more suitable: W = (cl +c2 e-c~P)P
(2)
The ratio of W to P c o m p u t e d from this equation approaches cl + c2 for very low, and cl for very high values of P. The constant c2 expresses thus the difference between the possibly highest and possibly lowest values of the W to P ratio, and the negative constant c3 is an expression of the rate of decrease of this ratio with increasing P. It can be assumed that the closer this ratio is to the constant c l , the more mature is the animal somatically. If it is so, then the higher is the negative value of c3, the faster is the rate of maturing. For example, in pigs weighing 90 kg (assumed P = 13.5 kg) values of c3 equal to --0.10, --0.15 and --0.20 correspond to about 74, 87 and 93% " m a t u r i t y " , expressed in percents of c2 depleted. For an illustration an equation has been c o m p u t e d fitting Kotarbifiska's (1969) data (W and P in kg): W = (3.09 + 2.13 e -0.16P) p
(2a)
It seems that sex differences are mainly due to different values of c~, and that c~ increases in response to selection for meatiness. This could be perhaps explained by the fact that the W to P ratio is higher in muscles than in total EBW. The equations listed in Tables I and II allow the crude chemical composition of the pig's body to be estimated, whenever P and EBW are known. They also permit estimation of the increments of W, A and P in body gain, when the increment of P and the initial body composition are known. In individual cases a strict reliance on these estimates can be misleading because of the variability of animals, and the parameters obtained for one breed or strain may n o t be applicable to others. However, initial observations at the Institute in Jablonna show t h a t within the fiducial limits the equations obtained for Large White pigs fit a population of the Norwegian Landrace, and t h e y fit also rather closely data on the composition of the pig's body published by Just Nielsen (1970). It should be remembered t h a t the meaning of the chemical body constituents discussed in this paper is vaguely defined. The multiplier 6.25 applied widely for computing body protein is not based on adequate experimental data. Moreover, unpublished data from the Institute in Jablonna indicate that the proportion of amino N in total N increases in the b o d y as the animals grow, being 78 and 89% in pigs weighing 10 and 100 kg, respectively. The identification of the ether extract with body fat is also purely arbitrary and in more detailed investigations structural and depot fat should be considered separately. Similar remarks could be made concerning the meaning of body water and ash. Nevertheless, apart from these reservations, the equations presented allow the course of changes of the chemical body composition of growing pigs to be outlined in general terms, creating a starting point for more detailed research.
261
INCREMENTS OF THE CHEMICAL BODY COMPONENTS AND THE PERFORMANCE OF A GROWING PIG An a t t e m p t to deduce the relationships between the increments of the chemical b o d y components and the measures of performance such as the daily live-weight gain and the feed conversion ratio was made in a paper published a decade ago (Kielanowski, 1966), and since adequate experimental data were lacking, this paper had to be based on rather roughly estimated values. The principles adopted were very simple. It has been postulated first that the intake (E i ) of metabolizable energy (ME) is equal to the sum of a c o m p o n e n t proportional to the live weight, called energy cost of maintenance (Em), a second component, obtained by multiplying the a m o u n t of protein deposited (A p) by the constant energy cost of unitary protein deposition (Ep), and a third component, obte~ned by multiplying the a m o u n t of fat deposited (A F ) b y the constant energy cost of unitary fat deposition (Ef). This could be expressed by the equation: El=Era +Ep A p+EfA
F
(3)
The value of Ef, consistent with biochemical deductions, was found to be nearly constant in energy balance trials (Schiemann et al., 1961), and the maintenance requirement of growing pigs was shown by Breirem (1939) to be the function of a fractional power of their live weight. The constancy of Ep, however, had to be assumed arbitrarily. The second postulate adopted was that the live weight gain (A LW) could be regarded as the sum of AF and of the product of Ap and the ratio (Q) of the lean body mass to A p, also arbitrarily assumed to be constant for a constant live weight range. Hence: A LW=AF+QAp
(4)
From equations (2) and (3) the two following ones could be obtained easily: F C = E i E f / [ E i -- E m + (EfQ -- Ep)A P]
(5)
AP = [E m + (Ef -- FC)A L W ] / ( E f Q - - E p )
(6)
In eq. (5) FC denotes the feed conversion ratio, i.e. the ratio of E i to A LW. If Ef and Ep, as well as E m and Q in animals growing over the same live weight range are ~ssumed constant then eq. (5) expresses FC as a function of Ei and A P, i.e. a function of the level of feeding and the protein deposition. In order to substantiate these deductions more experimental evidence was needed. As discussed previously, Kotarbifiska's investigations clarified the question of the LBM to P ratio and showed that it did n o t depend in practice on the fat c o n t e n t in the body. The applicability of eq. (4) was thus supported. Further, the suitability of eq. (3) was confirmed experimentally (Kotarbifiska, 1969) by the very close fit (T = 0.991) of the following equation,
262 obtained for 54 castrates growing from 30 to 90 kg (E i expressed in kcal ME, P and A F in g): E i = 101.5 + (16.0+ 1 . 9 ) ~ P + (13.0 + 0.9) A F_+ 4.9
(3a)
All this demonstrated that the approach adopted in the paper discussed was acceptable. The variables in eq. (3a) were taken as daily averages per unit (LW kg) °'75 , and so the regression constant corresponded to the maintenance requirement per kg °" 7s metabolic weight. It is worth mentioning that studies of Kotarbifiska's materials showed that the best possible fit was obtained b y raising LW to the power 0.734, n o t differing significantly from 0.75. Within the live weight range from 20 to 100 kg the maintenance requirement c o m p u t e d as 100 kcal (418 kJ) ME per kg °'Ts metabolic weight corresponds to that derived from Breirem's (1939) equation and is consistent with values obtained b y several other authors (Hoffmann et al., 1971; Verstegen et al., 1973). The regression coefficient for A P in eq. (3a) is an estimate of Ep. Several estimates of this value obtained later b y various authors for pigs and other animals were discussed in detail elsewhere (Kielanowski, 1976), and a hypothesis was proposed explaining the discrepancy between all these estimates and the energy cost of protein synthesis deduced biochemically. It was assumed that Ep consists of the cost of synthesis of protein deposited plus an additional increase of heat production correlated with A P, and that this increase results from protein turnover and/or endocrine factors, stimulating/x p and heat production simultaneously. Further investigations of this problem are desirable and should t h r o w more light on the causes of the rather high variability of experimental estimates of Ep, ranging for pigs from a b o u t 11.5 kcal ME/g in very y o u n g animals to 16.0 kcal ME/g in older ones. Thorbek (1970) in experiments with pigs weighing from 20 to 90 kg obtained an average estimate of a b o u t 13 kcal ME/g, n o t differing significantly from the estimate obtained from eq. (3a). The value of Ef estimated in pigs statistically, measured in respiration trials or deduced biochemically amounts consistently to a b o u t 13 kcal ME/g. If the same value is chosen as the unitary energy cost of protein deposition, Ep equals Ef, and this simplifies calculations. PRACTICAL CONSIDERATIONS The practical application of the model expressed by equations (3), (4), (5) and (6) can be demonstrated by the example of an annual report of the Danish progeny testing stations (Clausen et al., 1971). It has been assumed for this purpose that the average dally E m of pigs growing from 25 to 90 kg is 2.07 Mcal ME (0.1 Mcal per kg °'Ts metabolic weight), and the average LBM to P ratio in the e m p t y - b o d y gain is 4.3. It has been assumed also that the total e m p t y - b o d y gain is 6 ! . 7 5 kg (0.95 of the live-weight gain), and that 1 Scandinavian feed unit (SFU~ is equal to 3 Mcal ME. In agreement with previous remarks Ep and Ef have been assumed equal and amounting to 13 Mcal
263 ME/kg. All these values have been substituted for symbols in the basic equations. Data on FC and the average daily gain (lwg), as listed in the Danish reports, now allow the total and daily gains of P and F for each tested group of pigs to be computed. As an example, the equation for computing the total gain of P is given (FC expressed in Mcal/kg, and lwg in kg) : AP =
2.07 (65/lwg) + ( 1 2 . 3 5 - - F C ) 65
(6a)
42.9
In the report quoted the average FC was 2.88 SFU/kg and the average lwg was 0.686 kg, while in the most and least efficient groups they were 2.66 SFU/kg and 0.758 kg, and 3.44 SFU/kg and 0.565 kg, respectively. The computations showed t h a t this corresponded to the estimated daily gains of 108 g P and 189 g F on average, 125 g P and 181 g F in the best, and 75 g P and 214 g F in the worst group. The estimated difference in protein deposition between the best and the worst group is compatible with the results of actual N balance trials and offers the most probable explanation of the difference in their performance, as manifested by FC and lwg. The supposition that the different performances were due to differences in Em or Q, assumed somewhat arbitrarily as constant, is much less probable. If the different performances were caused by different Era, with the rate of P deposition held constant, the average E m should be about 1 Mcal in the best and 3 Mcal in the worst group. Similarly, if a different Q were the only reason, it should be about 5.1 in the best and 3.5 in the worst group, and such great differences in
SF c 3.! 3.4. 3.3" 3.2. 3.1 3.0 2.9-
2.5
~
2.8-
2.0
2.71.5 o'.s
o.8 '
0.7 '
o .'a
kq/da y
Fig.1. Curves corresponding to the low, medium and high chemical fat to protein ratio in the live-weight gain of pigs growing from 25 to 90 kg, in relation to the feed conversion ratio (Scand. feed units per kg gain) and the average daily live-weight gain (kg/day). The dots represent the performance of groups taken randomly from a report of Danish progeny testing stations (Clausen et al., 1971).
264
E m or Q are out of the question. The level of feeding was n o t very variable. It can be concluded, therefore, that factors other than the rate of protein deposition could have had only a slight modifying influence on the performance. In order to verify the model discussed with regard to carcass quality, the estimated total AP was correlated with the area of the longissimus dorsi cross section. For this purpose data for 46 groups were taken from a randomly chosen page in the quoted Danish report (Clausen et al., 1971, p. 75). The highly significant correlation was 0.475, i.e. very similar to that found by Babatunde et al. (1966) for the body protein actually determined. The ratio of total fat to protein deposited can be regarded as an index of carcass desirability, and it can be assumed that values of this ratio amounting to 2.5, 2.0 and 1.5 correspond to carcasses of poor, average and excellent quality, respectively. In Fig.1 lines are drawn depicting these values, in relation to FC and lwg, and test groups, taken from the same page of the Danish report are marked by dots. It can be seen that in most groups the estimated fat to protein ratio is between 2.0 and 1.5, in several groups it is less than 1.5, and in two groups about 2.5. In doubtful cases the equations proposed can help to classify the group performance, as judged by FC and lwg. For example, among the groups considered there was one with FC = 2.79 SFU/kg and lwg = 0.678 kg, and another with FC = 2.91 SFU/kg and lwg = 0.704 kg. It is difficult at first sight to decide which should be valued higher, the greater daily gain or the better feed conversion. By means of the equations, however, it can be c o m p u t e d that in the group with the lower gain the estimated daily protein deposition was about 111 g and the ratio of fat to protein deposited was about 1.5. It should be classified higher, therefore, than the other group, for which these values were about 108 g and 1.9. Such classifications can be useful, particularly in the case of comparing sire averages. It is obvious that all these estimates should n o t be taken at their face value. The constants assumed, though realistic and based on ample e x p e r i m e n t a l evidence, were chosen rather arbitrarily, and their values most suitable for the Danish stations could be slightly different. Even if it were so, however, the new and maybe more accurate constants would result in shifting the estimates more or less parallel in one or the other direction, but the ranking of groups would probably remain unchanged. Duniec et al. (1968) found that in pigs, which after reaching a weight of 30 kg were fed for 84 days on equal rations increased gradually t h r o u g h o u t the experiment, the rate of protein deposition actually determined was highly correlated with FC (r = --0.922) and with lwg (r = 0.869). Duniec et al. also found that the protein c o n t e n t of the e m p t y body was highly correlated with the a m o u n t of dissectable meat in the primal cuts (r = 0.853). The rate of protein deposition, therefore, should be considered the most important factor determining the performance of growing pigs, as far as both the feed conversion and the carcass quality are concerned. Feed conversion and the daily gain were shown to be highly inheritable. For example, Jonsson and
265 King (1962) estimated the heritabilities of these traits as 0.48 and 0.45, respectively. Both these traits, as demonstrated in this paper, depend predominant. ly on the rate of protein deposition, which, therefore, is most probably also highly inheritable. Fig.2 gives an example of the genotype--environment interaction. The " g e n o t y p e " is represented by the average rate of protein deposition, the "env i r o n m e n t " by the average level of feeding, and the carcass quality is characterized again by the fat to protein ratio. It can be seen that carcasses of a fair quality can be obtained with a wide range of " g e n o t y p e s " , provided a suitable level of feeding is applied. It would hardly be possible, however, to obtain gains with the fat to protein ratio of 1.5 or less, if the pigs were unable to deposit more than 90 g protein daily, and in pigs that deposit 130 g or more the fat to protein ratio will be always low, even if they are fed ad libitum. The picture presented in Fig.2 was drawn on the loose assumption that the rate of protein deposition is n o t influenced by the quality and level of nutrition. However, it is well known that until a certain plateau is reached, N balance depends strictly on the a m o u n t and quality of protein in the ration, and pigs in which the protein deposition is restricted by nutritional factors will behave as those in which the genotype sets the limit. It is also
2.2,4
2.1,
2,0,
/
1.9"
1.8'
o . o. s
J
o.12 o.~4 kq/d a y .~ o 9 . o.lo . o i l . . . o.~3 Fig.2. Lines representing several chemical fat to protein ratios in the live-weight gain of pigs growing from 25 to 90 kg, in relation to the average daily protein deposition (kg/day) and the average daily feed intake (Scand. feed units/day).
266
known that even when the feed protein supply is adequate and the level of feeding is low, supplements of energy to the ration result in an increased N balance. The rate of protein deposition can be modified also by other factors, e.g. compensatory growth (Kielanowski, 1967), feed additives, such as copper sulphate (Braude, 1965) and probably by the use of anabolizers. Nevertheless, Fig.2 can be understood as a fair illustration of the way in which the combined effect of the level of feeding and the rate of protein deposition, in practice depends mainly on the genotype. The model discussed can also be useful for interpreting feeding trials. The partial derivatives of eq. (5} with respect to Ei and to AP indicate that an increment of Ei results in an increase, and an increment of Ap in a decrease of FC. Thus, for example, if in a feeding trial a decrease of the feed intake did not result in an improvement of FC, it is an indication that the protein deposition must have declined. COROLLARY
The knowledge of the course of changes in the chemical b o d y composition of growing pigs has helped to demonstrate the main physiological factors responsible for the quantitative and qualitative results of pig production. This has made it possible to explain more explicitly than hitherto the effects of various treatments applied to pigs and even to predict these effects, and on the foundation of this newly acquired knowledge practical pig growth models could be constructed {Cop, 1974; Whittemore and Fawcett, 1974). Moreover, the way has been opened for studying comprehensively the growth response to hereditary and environmental factors, as well as for investigating the m o d e of action of physiological agents, such as hormones and feed additives. The crude composition of the b o d y presents only a framework, which should be filled up with more detailed analyses. The relative amounts of different nitrogenous c o m p o u n d s of the b o d y certainly change depending on the age and size of the animals and possibly also on their nutrition, and this could be related to the utilization of feed protein. For example, in piglets nearly 90% of the digested N was recovered in the growing tissues (Braude et al., 1970; Lassota, 1967), whereas in older pigs protein utilization seldom exceeds 40%. It can be assumed that the very high protein utilization in piglets is connected with the rapid multiplication of nuclei, while in older animals the protein deposition is predominantly an effect of cell hypertrophy, and this could be studied by investigating the DNA to protein ratio. More sophisticated data on other constituents of the body, and, particularly, on the metabolism and variability of the content of b o d y water are desirable, and all this detailed information could be built into a reference system of the kind similar to that described in this paper.
267
ACKNOWLEDGEMENTS
The author is greatly indebted to Dr. Maria Kotarbiflska, Professor Zofia Osiflska and Dr. A. Ziolecki for reading the manuscript and for advice. REFERENCES Babatunde, G.M., Pond, W.O., Van Vleck, L.D., Kroening, G.H., Reid, J.T., Staufer, J.R. and Wellington, G.H., 1966. Relationships among some physical and chemical parameters of full- versus limited-fed Yorkshire pigs slaughtered at different live weights. J. Anita. Sci., 25: 526--531. Braude, R., 1965. Copper as a growth stimulant in pigs. In: Trans. Syrup. Cuprum Pro Vita, Vienna, pp. 55--66. Braude, R., Mitchell, K.G., Newport, M.J. and Porter, J.W.C., 1970. Artificial rearing of pigs. Br. J. Nutr., 24: 501--516. Breirem, K., 1939. Der Energieumsatz bei den Schweinen. Tierern~hrung, 11: 487--528. Clausen, H., N~rtoft Thomson, R., Pedersen, O.K., Busk, H. and Christensen, A., 1971. 59. Beretning om Sammenlignende Fors~g med Svin. 390. Beretning fra Fors~gslaboratoriet, K~bbenhavn, 163 pp. CSp, W.A.C., 1974. Protein and fat deposition in pigs in relation to body weight gain and feeding level. H. Veenman en Zonen B.V., Wageningen, 74 pp. Duniec, H., Kielanowski, J. and Osiflska, Z., 1968. The method of pig progeny testing applied in Poland. Paper presented at the E.A.A.P. session of the Commission on Pig Production, Dublin, 1968 (mimeographed). Hoffmann, L., Schiemann, R. and Jentsch, W., 1971. Energetische Verwertung der N~ihrstoffe in Futterrationen. In: R. Schiemann (Editor), Energetische Futterbewertung und Energienormen. VEB Deutscher Landwirtschaftsverlag, Berlin, pp. 118--167. Jonsson, P. and King, J.W.B., 1962. Sources of variation in Danish Landrace pigs at progeny testing stations. Acta Agric. Scand., 12: 68--80. Just Nielsen, A., 1970. Alsdige foderrationers energetiske vaerdi til vuekst hos svin belyst ved forskellig metodik. Frederiksberg Bogtrykkeri, K~bbenhavn, 212 pp. Kielanowski, J., 1966. Conversion of energy and the chemical composition of gain in bacon pigs. Anim. Prod., 8: 121--128. Kielanowski, J., 1967. Efficiency of energy utilisation in growing pigs. In: Report of Proc. and Invited Papers, 9th Intern. Congress Anita. Prod., Edinburgh, 1966. Oliver and Boyd, Edinburgh, pp. 212--224. Kielanowski, J., 1976. Energy cost of protein deposition. In: D.J.A. Cole, K.N. Boorman, P.J. Buttery, D. Lewis, R.J. Neale and H. Swan (Editors), Protein Metabolism and Nutrition, E.A.A.P. Publ. No. 16, Butterworths, London--Boston, pp. 207--215. Kielanowski, J. and Kotarbiflska, M., 1974. Chemical composition and energy value of the live-weight gain in growing pigs. In: K.H. Menke, H.-J. Lantzsch and J.R. Reichl (Editors), 6th Symposium on Energy Metabolism of Farm Animals, Universit~it Hohenheim, Dokumentationsstelle, Stuttgart, pp. 165--168. Kotarbihska, M., 1969. Badania nad przemiana energii u rosnacych gwifl. Instytut Zootechniki, Wydawnictwa Wlasne, Nr 238, Wroclaw, pp. 68. Kotarbiflska, M., 1971. The chemical composition of the body in growing pigs. Rocz. Nauk rol., B-93-1: 129--135. Lassota, L., 1967. Utilization of feed protein in baby pigs as influenced by addition of lactose. Acta Universitatis Agriculturae, Brno, XXXVI, 3: 397--402. Reid, J.T., 1972. Body composition of animals: interspecific sex and age peculiarities, and the influence of nutrition, In: L.S. Spildo, T. Homb and H. Hvidsten (Editors), Fest-skrift til Knut Breirem. Mariendals Boktrykkeri A.S., Gj~bvik, pp. 213--238.
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Schiemann, R., Hoffmann, L. and Nehring, K., 1961. Die Verwertung reiner N~ihrstoffe. 2. Mitteilung. Arch. Tierern~hr., 11: 253--283. Thorbek, G., 1970. The utilization of metabolizable energy for protein and fat gain in growing pigs. In: A. Schiirch and C. Wenk (Editors), 5th Symposium on Energy Metabolism of Farm Animals, Juris Druck + Verlag, Zurich, pp. 129--] 32. Verstegen, M.W.A., Close, W.H., Start, I.B. and Mount, L.E., 1973. The effect of environmental temperature and plane of nutrition on heat loss, energy retention and deposition of protein and fat in groups of growing pigs. Br. J. Nutr., 30: 21--35. Whittemore, C.T. and Fawcett, R.H., 1974. Model responses of the growing pig to the dietary intake of energy and protein. Anim. Prod., 19: 221--231. Rt~SUMI~ Kielanowski, J., 1976. Composition chimique du gain de poids vif et performance du porc en croissance. Livest. Prod. Sci., 3 : 257--269 (en anglais). Le texte expose les recherches effectu~es en Pologne sur la composition chimique du corps du porc en eroissance. Elle a ~t~ ~tudi~e sur pros de 300 porcs, femelles et m~les castr~s, qui ont ~t~ aliment~s suivant diff~rents niveaux et abattus ~ des poids couvrant l'intervalle de 2,5 ~ 90 kg. Les correlations directes entre t o u s l e s composants de l'organisme sont ~lev4es tandis qu'~ teneur en prot~ines maintenue constante, les correlations partielles entre la graisse corporelle et la masse corporelle maigre et entre les teneurs en graisse et en eau, sont tr~s faibles et non significatives. On peut en conclure que, chez les animaux ~tudi~s, la croissance de la masse maigre a ~t~ ind~pendante de celle de la teneur en graisse, cette derni~re ~tant simplement la consequence du surplus d'~nergie distribu~ aux animaux. Des ~quations de r~gression permettent d'~valuer la composition chimique totale du corps lorsque on conn~it le poids vif et la teneur en un seul des composants, les prot~ines de preference. On essaie ~galement de d~montrer, au moyen d'un module math~matique, que l'efficaeit~ de l'utilisation des aliments, ainsi que le rapport entre graisse et prot~ines d~pos~es dans le corps en croissance, d~pendent surtout du plan d'alimentation et de la capacit~ de l'animal ~ d~poser des prot~ines dans ses tissus fi une vitesse plus ou moins grande. L'application pratique de ce module est illustr~e par un exemple tir~ des rapports des stations de testage danoises. En supposant que la vitesse ~ laquelle les prot~ines se d~posent dans le corps est un caract~re hautement h~ritable, on montre c o m m e n t le g~notype et le plan d'alimentation influencent conjointement la proportion graisse/prot~ine dans le gain de poids vif. KURZFASSUNG Kielanowski, J., 1976. Die chemische Zusammensetzung des Zuwachses und die Mastleistung wachsender Schweine. Livest. Prod. Sci., 3 : 2 5 7 - - 2 6 9 (in Englisch). Die in Polen durchgefiihrten Untersuchungen iiber die chemische Zusammensetzung des KSrpers yon wachsenden Schweinen wurden geschildert. Den Berechnungen lagen etwa 300 KSrperanalysen yon unterschiedlich gefiittertenJungsauen und Kastraten, die beim 2.5 bis etwa 90 kg Lebendgewicht geschlachtet worden waren, zurgrunde. Die einfachen Korrelationen zwischen allen chemischen Bestandteilen waren hoch, die partiellen Korrelationen dagegen, bei konstantem Eiweissgehalt, zwischen d e m Fettgehalt und der fettfreien KSrpersubstanz, sowie d e m Fett- und Wassergehalt waren sehr niedrig und nicht signifikant. Daraus ergibt sich, dass in dem untersuchten Tiermaterial das Wachstum der fettfreien KSrpersubstanz unabh~ingig vom Fettgehalt verlief und dass der Fettgehalt lediglich als eine Funktion des Energieiiberschusses in den Futterrationen zu betrachten sei. Regressionsgleichungen wurden vo~gelegt, welche eine Seh~itzung der gesamten chemi-
269
schen KSrperzusammensetzung ermSglichen, wenn das Lebendgewicht sowie der Gehalt an einem einzigen Bestandteil, am zweckm/issigsten an Roheiweiss, bekannt sind. Es wurde weiter an einem mathematischen Modell veranschaulicht, dass die Futterausnutzung sowie das Fett-Eiweissverh~iltnis in der K~Srperzunahme haupts~chlich yon dem Fiitterungsniveau und der Kapazit~it der Tiere t~iglich mehr oder weniger Eiweiss abzulagern abh~ingen. Die praktische Anwendung dieses Modells wurde am Beispiel yon Angaben aus einem Bericht der d~inischen Schweinepri~fungsstationen dargestellt. Eine hohe Vererblichkeit der Eiweissablagerungsrate voraussetzend wurde ferner gezeigt, wie sich der Genotyp gemeinsam mit dem Fiitterungsniveau auf das Fett-Eiweissverh~ltnis des Zuwachses auswirkt.