The net energy value of crude (catabolized) protein for growth in pigs

Livestock Production Science, 9 (1982) 349--360 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

349

THE NET ENERGY VALUE OF CRUDE (CATABOLIZED) PROTEIN FOR GROWTH IN PIGS A. JUST

National Institute o f Animal Science, Rolighedsvej 25, 1958 Copenhagen V (Denmark) (Accepted 16 November 1981)

ABSTRACT Just, A., 1982. The net energy value of crude (catabolized) protein for growth in pigs. Livest. Prod. Sci., 9: 349--360. An experiment was performed with 36 growing pigs of Danish Landrace, to study the influence of digestible crude protein on the energy excretion with the urine and on the efficiency of utilization of metabolizable energy. The pigs (3 litters of females and 3 litters of male castrates) were distributed on six dietary treatments on a within-litter basis, taking into account the live weight of the pigs. The daily intake of the different diets was adjusted in such a way that the daily gain in the different treatment groups was almost identical through the entire experimental period from 20--90 kg. Three digestibility and nitrogen balance experiments were performed with each pig. At approximately 90 kg live weight the pigs were killed, dissected, ground, mixed and chemically analysed. The energy loss in urine increased by 4.9 kJ and the efficiency of utilization of metabolizable energy was decreased by approximately 6.6 kJ/g of catabolized protein. Digestibility experiments with ileo-caecal cannulated pigs indicated that the proportion of the digested energy disappearing in the caecum-colon increased with increasing dietary concentration of crude protein.

INTRODUCTION

The energy value of digestible protein has been the objective of several investigations and discussions. Thus Wolff et al. (1888) assumed that the energy value of digestible pure protein for horses was identical to the energy value of digestible NFE substances per weight unit. However, Kellner (1900) on the basis of respiration experiments with full-grown steers found the net energy value of digestible pure protein was only 94% of that of digestible carbohydrate, whereas Hansson (1913) on the basis of feeding trials with dairy cows calculated the "energy value" of digestible pure protein to be 143% of that of digestible carbohydrate per weight unit. In respiration experiments with almost full-grown pigs, Schiemann et al. (1971) found the net energy value of digestible crude protein to be only 85% of that of digestible NFE substances per unit of weight. Rubner (1902),

0301-6226/82/0000--0000]$02.75 © 1982 Elsevier Scientific Publishing Company

350 Borsook and Winegarden (1931), Martin and Blaxter (1965) and Tyrrell et al. (1970), among others, showed that the low net energy value of digestible protein is due to the fact that oxidation of protein increases the energy loss in urine and increases the heat production. The objective of the present investigation is to elucidate in more detail the influence of digestible crude protein on the energy loss in urine and on the efficiency of utilization of ME in growing pigs. The experiments were also performed with ileo-caecal re-entrant cannulated pigs to study the relationship between diet composition, site of absorption of the nutrients and energy utilization. MATERIAL AND METHODS The experiment comprised six litters, each consisting of seven pigs. One pig from each litter was killed at the beginning of the experiment to provide information about the initial c o n t e n t of energy, protein, etc., in the experimen tal pigs. The remaining six pigs in the litter were distributed on six different diets, as shown in Table I, taking into account the live weight of the pigs. Thus six pigs were allotted each dietary treatment. The main feedstuff composition of the diets is given in Table II. The pigs were fed in the six treatment groups with 75%, 100%, 125%, 150%, 175% and 200%, respectively, of their daily requirement for digestible crude protein according to the current Danish Standard (Andersen and Just, 1979). As the protein requirement of pigs in relation to the requirement for energy decreases with age or weight all diets were supplemented with a protein mixture as described in Table II. The supplement varied from 170 g in Group 1 to 740 g per day in Group 6 at 20 kg and was gradually decreased to 0 g at approximately 70 kg live weight. Lysine and methionine were added to the protein supplement for Group 1 so t h a t the daily digestible a m o u n t of these amino acids should be identical to those consumed by Group 2, i.e., identical to the TABLE I Experimental

design

Group

Litter 1 Litter 2 Litter 3 Litter 4 Litter 5 Litter 6

1

2

3

4

5

6

f* f f m** m m

f f f m m m

f f f m m m

f f f m m m

f f f m m m

f f f m m m

*f = female * * m = m a l e castrates.

351 TABLE II Feedstuff composition of the diets* Diet

1

2

3

% Barley % Wheat bran % Soya bean meal % Meat and bone meal % Maize starch % Animal fat % Sugar % Calcium carbonate % Dicalcium phosphate % NaC1 % Lysine mixture % Methionine mixture % Micromi.- and vit. mix.

30.9 30.2 -2.0 27.6 1.9 2.0 1.1 0.7 0.6 2.4 0.5 0.1

79.2 74.6 9.3 6.9 1.6 9.9 2.0 2.0 . . . 1.9 2.0 2.0 2.0 1.0 1.0 0.9 0.9 0.6 0.6 1.3 . . 0.1 . . 0.1 0.1

4

5

6

69.3 4.8 17.3 2.0 . 2.1 2.0 1.0 0.8 0.6 . . 0.1

63.8 2.5 25.0 2.0

58.6 0.4 32.4 2.0

2.2 2.0 1.0 0.8 0.6

2.3 2.0 0.9 0.7 0.6

0.1

0.1

.

. .

* The diets were supplemented with a protein mixture consisting of 85.7% soya meal, 5.0% skim milk powder, 2.2% meat and bone meal plus sugar, minerals, and vitamins. To Group 1, the protein mixture was further admixed with 9.9% of a lysine mixture (10% DL-lysine and 90% wheat bran) and 2.9% of a methionine mixture (10% methionine and 90% wheat bran). The protein supplement varied from 170 g in Group 1, to 740 g/day in Group 6 at 20 kg, and was gradually decreased to 0 g at approximately 70 kg live weight. All diets had added minerals and vitamins according to the current Danish Standards (Andersen and Just, 1979). TABLE III Average chemical composition of the diet dry matter Diet

1

2

3

4

5

6

% Crude protein % Stoldt fat* % Crude fibre % NFE % Soluble carbohydrate** % Neutral detergent fibre (NDF)*** MJ GE/kg

13.2 5.6 4.8 70.7 57.4

16.3 5.4 4.9 67.9 56.8

20.0 5.5 5.2 63.3 51.1

23.2 5.5 5.7 59.3 45.7

27.0 5.5 5.9 55.0 41.0

29.4 5.5 5.7 52.5 38.4

18.1 18.47

16.0 18.59

17.4 18.86

19.3 18.82

19.9 18.95

19.8 19.12

*Including a hydrolysis with hydrochloric acid prior to the ether extraction (Stoldt, 1957). **Starch plus sugar determined by an enzymatic procedure (Christensen, 1980). ***% NDF calculated = % crude fibre + % NFE - % soluble carbohydrate. standards for these a m i n o acids. With regard to o t h e r essential n u t r i e n t s , the d i e t s w e r e c o m p o s e d t o f u l f i l t h e daffy r e q u i r e m e n t s a n d t o a v o i d e x c e s s s u p ply. T h e a v e r a g e c h e m i c a l c o m p o s i t i o n o f t h e d i e t s c o n s u m e d is g i v e n i n T a b l e I I I . T h e daffy a m o u n t s o f t h e d i e t s w e r e r e g u l a t e d i n s u c h a w a y t h a t t h e

352 average live weight of the pigs in the different treatment groups was almost the same at all stages in the growth period from 20--90 kg to minimize variations in the maintenance requirement. Evenly distributed over the growth period (at approximately 25, 50 and 80 kg) three digestibility and nitrogen balance experiments were performed with each pig, i.e., in total 108 experiments. The pigs were fed twice daily. Faeces and urine were collected quantitatively t w o times daily over a seven day collection period. To prevent loss of ammonia from the urine, sulphuric acid was added to the collection container so that the pH of the urine remained below 2. The urine samples were stored in airtight plastic bottles and b o t h faeces and urine were stored at approximately 4 ° C. At the conclusion of the balance experiments, the faeces were ground and mixed and all analyses were performed on freeze
353 The digestibility experiments were performed during the growth period from 50--70 kg according to a 3 X 3 Latin square design. The diets were composed of the same kind of feedstuffs as used for the balance--slaughter investigations and the chemical composition o f the diets was intended to be identical to that of Groups 2, 4 and 6, respectively (Table III). The diets were ground through a 1-mm screen to prevent blockage of the cannulae. Each experimental period lasted seven days and equal amounts of the diet were given three times daily at 07.00 h, 15.00 h and 23.00 h. Faeces were collected for 24 h on Day 6 and ileal digesta was collected for 8 h on Day 7. Soft plastic tubing was attached to the ileal cannula during the collection period and led into a container filled with ice. As soon as digesta passed through the ileal cannula into the tubing, it was squeezed b y hand until the digesta was below the ice level in the container. Every 1--2 h, depending on flow rate, the digesta was transferred from the tubing to a graduated beaker and distilled water was added. After thorough mixing, a 50% sample was drawn for chemical analyses and frozen immediately. The remainder was made up to the original volume with distilled water, warmed to 38°C and gradually infused through the caecal cannula. Chromic oxide was used as a marker and the analyses for chromic oxide were performed b y the m e t h o d of Schiirch et al. (1950), modified as described b y Jakobsen and Weidner (1973). More details a b o u t procedures, diet composition etc., are given b y Just et al. (1980a,b) and Sauer et al. (1980) RESULTS AND DISCUSSION The pigs in the balance--slaughter investigation were in good health except one in each of Groups 1, 4 and 5, which were therefore removed. The pigs' appetites, when fed on protein-rich diets were somewhat poor, and a few cases of diarrhoea occurred among the pigs fed on Diet 6. The daily intake of digestible crude protein varied slightly less than planned. The relative values were 8 3 , 1 0 0 , 1 1 9 , 1 4 1 , 1 6 5 and 186, respectively, for the six treatments. The average results are shown in Table IV. The pigs fed on Diet 1 consumed 6--10% more ME than those fed on the other diets, b u t the daily gain was slightly lower. The explanation is most likely an insufficient supply of digestible threonine as the diet was fortified with lysine and methionine to fulfil the requirements of the pigs, b u t the size of the daily intake o f digestible protein should also be considered. Nevertheless, the results obtained with Diet 1 are in accordance with those obtained with the other diets with respect to digestibility and energy utilization. The influence of catabolized protein on energy utilization should also b y and large be independent of whether the catabolized protein originates from an excessive supply or from a poor amino acid composition. To test that hypothesis a number of comparative regression analyses were performed, b u t only slight and insignificant differences were f o u n d as illustrated b y the following

354 TABLE IV The influence of crude protein on the digestibility, metabolizability and the utilization of ME (n = 33) Group

3

4

5

6

Feed intake, gain and carcass weight DM (kg/day) 1.74 1.60 ME (MJ/day) 24.73 23.23 Gain (g/day) * 577 607 Carcass weight (kg) 68.9 68.5

1.55 22.43 632 68.7

1.55 22.37 627 68.7

1.54 22.47 600 67.3

1.58 23.48 583 67.5

Digestibility (%) Crude protein Stoldt fat Crude fibre NFE Soluble carbohydrate Energy

79 56 29 91 100 80

Metabolizability In urine (MJ/kg DM) ME (MJ/kg DM) ME (% of GE) ME (% of DE) Utilization of ME Deposited energy (MJ/kg DM) NE (MJ/kg DM)** Deposited energy (% of ME) NE** (% of ME)

1

2

74 57 25 90 100 79

79 53 30 91 99 80

81 60 36 91 99 81

82 63 45 92 99 82

82 63 54 93 97 83

0.39 14.26 77 97

0.48 14.49 78 97

0.62 14.46 77 96

0.75 14.41 77 95

0.88 14.59 77 94

1.03 14.87 78 94

5.20 9.05

4.97 9.07

4.86 9.08

4.67 8.93

4.17 8.27

4.53 8.50

36 64

34 63

34 63

32 62

29 57

30 57

*Adjusted to 25% slaughter loss, i.e., carcass weight/0.75. **NE, MJ = deposited energy, MJ + 0.326 MJ × average live weight, kg °-7~. example Deposited energy, % of ME = Y Digestible crude protein, g/day = X I n c l u s i v e t r e a t m e n t 1 (n = 3 3 ) . Y = 4 0 . 1 - 0 . 0 2 7 X . s b = 0.004, CV = 5.7, r 2 = 0.74 W i t h o u t t r e a t m e n t 1 (n = 2 8 ) . Y = 3 9 . 6 - 0 . 0 2 5 X . s b = 0 . 0 0 6 , C V -- 6 . 4 , r2 = 0.67 The digestibility of crude protein increased with increasing percentages in t h e d i e t , as w a s t o b e e x p e c t e d p a r t l y b e c a u s e t h e d i g e s t i b i l i t y o f c r u d e p r o t e i n i n s o y a m e a l is h i g h e r t h a n t h a t o f t h e o t h e r f e e d s t u f f s in t h e d i e t s a n d p a r t l y b e c a u s e e n d o g e n o u s f a e c a l p r o t e i n m o r e o r less is p r o p o r t i o n a l t o t h e amount of diet dry matter (approximately 9 g per kg DM) and therefore exerts a greater negative effect on low protein diets than on high protein diets.

355

The digestibility of crude fibre increased with increasing content of dietary protein and dietary fibre. The explanation is probably a combination of a high digestibility of crude fibre in soya meal (approximately 75%) per se and an increase of the fermentative processes in the hind gut as can be derived from Table V. The digestibility of GE increased with increasing levels of dietary protein, because of the increase in the digestibility of the nutrients. Increasing amounts of digestible crude protein increased the energy loss with the urine, decreased ME in per cent of DE and decreased the efficiency of utilization of ME. The results obtained with cannulated pigs are shown in Table V. The pattern of the digestibility coefficients is similar to that in Table IV, b u t the digestibility is generally a few units higher. The explanation may be that these diets were ground through a 1 mm screen to avoid blockage of the cannulae, whereas the diets used in the balance--slaughter investigations were ground through a 4 mm screen and the digestibility increases with increasing fineness of the ground material especially in fibrous diets (Just, 1978). The use of chromic oxide as a marker instead of quantitative collection m a y also influence TABLE V The influence of crude protein o n the digestibility and site of absorption, i.e., small intestine versus hind gut Diet In diet, DM % Crude protein % Stoldt fat % Crude fibre Daily feed intake kg DM

I(2)

16.5 5.4 5.7

1.37

II(4)

24.1 5.4 4.9

1.38

III(6)

32.8 5.7 5.6

1.36

% Digested (A) and % of digested disappearing in caecum-colon (B) Crude p r o t e i n A* 78 84 87 Crude protein B* 14 10 9 Lysine A* 84 86 90 Lysine B 2 3 7 Stoldt fat A 69 73 74 Stoldt fat B 0 0 -4 Linoleic acid A 97 99 98 L i n o l e i c acid B 14 11 9 Crude fibre A* 21 35 55 Crude fibre B* 54 90 97 Soluble carbohydrate A 100 100 100 Soluble carbohydrate B* 3 4 6 Energy A* 79 84 86 Energy B 13 15 17 * The difference between diets is statistically significant (P < 0.05).

356 the calculated digestibility, b u t several comparative studies have shown that the calculated digestibility 0nly seldom deviates more than 2 units between methods. The fact that the feedstuffs used in the t w o investigations were from different batches may also contribute to the difference in the digestibility. The diet composition had a significant influence on the amount o f the different nutrients being absorbed in the small intestine and disappearing in the hind gut, respectively. For example the amount of lysine disappearing in the hind gut increased with increasing concentration of dietary crude protein, but the value of that lysine for protein synthesis in the pig is almost nil (Just et al., 1 9 7 9 , 1 9 8 1 ), probably because the amino acids transferred to the hind gut are degraded to ammonia and other lower nitrogen c o m p o u n d s b y the microflora. The lower nitrogen c o m p o u n d s are absorbed, but transformed to urea and excreted with the urine. The ability of the hind gut to absorb intact amino acids seems also to be very limited as lysine infused into the caecum was recovered in the faeces (Just et al., 1981). On the diet richest in crude protein more Stoldt fat was f o u n d in the faeces than had been transferred to the hind gut from the small intestine. That could be due to errors, b u t it could also be due to a microbial synthesis of fat from other nutrients in the hind gut (Just and Mason, 1974; Just et al., 1980b). The data for crude fibre given in Table V, clearly illustrates the significance of the fermentation processes in the hind gut as 54% to 97% of the digested fibre disappeared in that region. Although not significant the a m o u n t of digested energy disappearing in the hind gut increased from 13--17% with increasing concentration of dietary protein. In Table VI the relationship between the a m o u n t of digestible crude protein in the diets and the amount and utilization of ME is elucidated b y the results of regression analyses. Equation 1 shows that the energy excretion into the urine increases 30.6 kJ/g nitrogen, which corresponds to 20.5% of the energy in the digestible crude protein. If all the nitrogen in the urine were in the form of urea, the energy loss should be only 16.0% (Kleiber, 1961), but although most of the nitrogen is present in the urea, the urine m a y contain other nitrogenous substances, for example amino acids as well as nitrogen-free substances containing energy. Equation 2 is similar to eqn. 1, b u t it gives the decrease in the metabolizability in per cent per g increase in digestible crude protein. Equation 3 gives the contribution from the digestible nutrients to ME. The contribution from digestible crude protein to ME is 2 kJ less per g than that found by Just (1970, 1982) which is in accordance with the lower protein utilization due to the excess supply of digestible crude protein to four of the six treatment groups. The utilization of ME was highly influenced by the concentration of digestible crude protein in the diets, as shown b y eqns. 4, 5 and 6 in Table VI. The negative effect of oxidized digestible crude protein varied from 6.1 kJ/g in eqn. 4, to 7.2 kJ/g in eqn. 5. Calculation of the negative effect from eqn. 6 gives 6.6 kJ/g, which is exactly the mean of the former equations. The dif-

357 TABLE VI E q u a t i o n s e l u c i d a t i n g t h e e f f e c t o f d i g e s t i b l e crude protein on the a m o u n t a n d u t i l i z a t i o n of ME (n = 33) Amount of ME ( 1 ) E n e r g y in u r i n e , k J / g N = 3 3 4 + 3 0 . 6 × N, g / d a y sb

=l.1;t

b = 28.2;CV=6.3;r2=0.97

( 2 ) M E in % o f D E = 1 0 0 . 3 - 0 . 0 1 8 × d i g e s t i b l e crude protein, g / d a y sb = 0 . 0 0 1 ; t b = 2 7 . 8 ; C V = 0.3; r 2 = 0.97 ( 3 ) M E , k J / d a y = 1 3 6 + 1 9 . 5 X 1 + 2 8 . 3 X 2 + 14.2 X 3 + 1 7 . 6 X 4 sb

tb

1.3 14.8

5.7 4.9

5.5 2.6

0.6 31.6

C V = 0.4, R 2 = 0 . 9 9 X1--X2--X3--X

4 = g digestible

crude protein, -fat, -fibre a n d N F E p e r d a y

Utilization of ME ( 4 ) Deposited energy, k J / d a y = - - 6 7 9 - 6.1 × d i g e s t i b l e crude protein, g / d a y + 0 . 4 3 × M E , kJ/day sb tb

1.0 6.0

0.08 5.0

CV = 5 . 5 ; R 2 = 0.87 (5) N E * , k J / d a y = 5 6 9 5 -- 7.2 x d i g e s t i b l e crude protein, g / d a y + 0 . 4 5 × M E , k J / d a y sb tb

1.4 5.3

0.11 3.9

CV = 4.0;R 2 = 0.83 (fi) N E * , % o f M E = 6 8 . 7 - 0 . 0 2 9 × d i g e s t i b l e crude protein, g / d a y s b = 0.006,

t b = 4.8,

CV = 4.2, r 2 = 0.59 0.75

* N E , M J = deposited energy, M J + 0 . 3 2 6 M J x average live w e i g h t kg

ferences between the regression coefficients are partly due to the limited number of observations (33) and correlations (approximately 0.5) between the independent variables. The heat loss 6.6 kJ/g oxidized digestible crude protein corresponds to 28% of the energy in the digestible crude protein (23.85 kJ/g) or 35% of the ME in catabolized protein (18.96 kJ/g). The collective energy losses from catabolized protein thus account for 48.5% or approximately 50% of the ener gy in the protein.

358 The heat loss from oxidized digestible crude protein is far higher than the energy cost of urea formation and excretion (Martin and Blaxter, 1965). The higher heat loss is probably due to recirculation of urea (Rerat, 1978) and as can be derived from Table V, the heat loss is confounded with the size of the fermentation processes in the hind gut. As will be shown in the forthcoming papers, (Just, 1982) a negative relationship seems to exist between the percentage of the energy disappearing in the hind gut and the efficiency of utilization of ME. The physiological background of that relationship is probably a different chemical composition of the nutrients absorbed from the small intestine and those disappearing in the hind gut. In the hind gut, a large proportion of the carbohydrates is fermented b y the microflora to volatile fatty acids, which most likely have a lower metabolic efficiency than the glucose absorbed from the small intestine. Besides, gas production takes place in the hind gut. The energy in the gases as well as the energy released due to the fermentation processes is lost, b u t counted as having been absorbed. That energy loss may very well be positively correlated to the proportion of digested energy disappearing in the hind gut. It follows that a part of the energy loss due to the fermentation processes may have been included in the regression coefficients. On the other hand the heat loss, 35% of the ME in catabolized protein, is identical to the heat loss found b y Martin and Blaxter (1961), b u t low compared to the results o f H o f f m a n n (1965), who on the basis of biochemical considerations calculated the heat loss to be within 35--50%. In investigations with pure nutrients Schiemann et al. (1961) found an average heat loss of 38% of ME from protein, but it varied between 28--45%. However, the overall energy loss from digestible protein found in this investigation (48.5%) is not far from the overall energy loss (55%) that is given b y the equation published b y Schiemann et al. (1971). It is amazing that the overall energy loss from catabolized protein is of the same magnitude as the numerous indirect estimates of the energy loss from protein deposition. The explanation may well be as stated by Van Es (1980) that the indirect estimates of the energy costs of protein deposition lack precision and are confounded with the maintenance metabolism. REFERENCES Andersen, P.E. and Just, A., 1979. Tabeller over fodermidlers sammensaetning m.m.K.dan. Landhusholdnings., K~benhavn, 56 pp. Borsook, H. and Winegarden, H.M., 1931. The energy cost of the excretion of urine. Proc. Natl. Acad. Sci., 17: 13--28. Christensen, K.D., 1980. Bestemmelse af let~ploseligeog lethydrolyserbare kulhydrater (LHK). Ugeskr. Jordbr., 12: 340. Hansson, N., 1913. En ny metod fSr ber~kning av fodermedlens produktionsv6xde rid utfodring av rnjSlkkor. Meddn. Nr. 85 fr~n Cent. Anst. F~irs.Jordbr. Omr~d, Stockholm, 17 pp. Hoffmann, L., 1965. Modellvorstellungen zur Leistungsvorhersage auf der Basis der Nettoenergie und der umsetzbaren Energie. Arch. Tierern~hr., 15: 487--506.

359 Jakobsen, P.E. and Weidner, K., 1973. In: Chemistry of Feedstuffs and Animals. Comp. 1., Vet. Fac. FAO Fellows, Royal Vet. Agric. Univ., Copenhagen, pp. 14--55. Just (Nielsen), A., 1970. Alsidige foderrationers energetiske vaerdi til vaekst hos svin belyst ved forskellig metodik. 381. beretn, fors~gslab., K~benhavn, 212 pp. Just, A., 1978. The influence of processing on the nutritive value of cereals for pigs. 29th Ann. Meet. EAAP, Stockholm, 9 pp. Just, A., 1982. The net energy value of balanced diets for growth in pigs. Livest. Prod. Sci., 8: 541--555. Just (Nielsen), A. and Mason, V.C., 1974. The influence of the intestinal microflora of growing pigs on the apparent digestibility of fatty acids and energy. Proc. 6th Symposium on Energy Metabolism of Farm Animals. EAAP publication, 14: 193--196. Just, A., J5rgensen, H. and Fernandez, J., 1979. The digestive capacity of the caecumcolon and the value of the nitrogen in the hind gut for protein synthesis in pigs. 30th Annual Meeting EAAP, Harrogate, 5 pp. Just, A., Sauer, W.C., Bech-Andersen, S., JSrgensen, H.H. and Eggum, B.O., 1980a. The influence of the hind gut microflora on the digestibility of protein and amino acids in growing pigs elucidated by addition of antibiotics to different fractions of barley. Z. Tierphysiol. Tierern~ihr. Futtermittelkde., 43: 83--91. Just, A., Andersen, J.O. and J5rgensen, H., 1980b. The influence of diet composition on the apparent digestibility of crude fat and fatty acids at the terminal ileum and overall in pigs. Z. Tierphysiol. Tierern~ihr. Futtermittelkde., 44 : 82--92. Just, A., J5rgensen, H. and Fernandez, J.A., 1981. The digestive capacity of the caecumcolon and the value of the nitrogen absorbed from the hind gut for protein synthesis in pigs. Br. J. Nutr., 46: 209--219. Kellner, O., 1900. Untersuchungen fiber den Stoff- und Energie-Umsatz des erwachsenen Rindes bei Erhaltungs- und Produktionsfutter. K. Landw. Versuchs-Station zu MSckern, Berlin, 53: 1--474. Kleiber, M., 1961. The Fire of Life. Wiley, New York/London, 454 pp. Martin, A.K. and Blaxter, K.L., 1961. The utilization of the energy of protein by ruminants 2. Symposium on energy metabolism, Wageningen, The Netherlands, EAAP Publ., 10: 200--210. Martin, A.K. and Blaxter, K.L., 1965. In: K.L. Blaxter (Editor), The Energy Cost of Urea Synthesis in Sheep. I: Energy Metabolism. Academic Press, London, pp. 83--90. Rerat, A., 1978. Digestion and absorption of carbohydrates and nitrogenous matters in the hind gut of the omnivorous nonruminant animal. J. Anita. Sci., 46: 1808--1837. Rubner, M., Die Gesetze des Energieverbrauchs bei Ern~hrung. Franz Deuticke, Leipzig und Wien, 426 pp. Sauer, W.C., Just, A., JOrgensen, H.H., Fekadu, M. and Eggum, B.O., 1980. The influence of diet composition on the apparent digestibility of crude protein and amino acids at the terminal ileum and overall in pigs. Acta Agric. Scand., 4: 449--459. Schiemann, R., Hoffmann, L. and Nehring, K., 1961. Die Varwertung reiner N~ihrstoffe. Versuche mit Schweinen. Arch. Tierern~ihr., 11: 265--283. Schiemann, R., Nehring, K., Hoffmann, L., Jentsch, W. and Chudy, A., 1971. Energetische Futterbewertung und Energienormen. VEB Deutscher Landwirtschaftsverlag, Berlin, 344 pp. Schfirch, A.F., Lloyd, L.E. and Crampton, E.W., 1950. The use of chromic oxide as an index for determining the digestibility of a diet. J. Nutr., 41 : 629--636. Stoldt, W., 1957. Mitteilung der Fachgruppe Futtermitteluntersuchung. Landwirtsch. Forsch., 10: 273--277. Tyrrell, H.F., Moe, P.W. and Flatt, W.P., 1970. Influence of excess protein intake on energy metabolism of the dairy cow. In: Energy Metabolism of Farm Animals. EAAP publ. 13: 69--71. Van Es, A.J.H., 1980. Energy costs of protein deposition. In: Protein Deposition in Animals. Butterworth, London/Boston, pp. 215--224.

360 Wolff, E.S., Kreuzhage, C. and Riees, C., 1888. Grundlagen fiir die rationelle Fiitterung des Pferdes. Biedermann's Zentralbl. Agrik. Chem., 17: 299--314. RESUME Just, A., 1982. Valeur Energ~tique nette des mati~res grasses pour la croissance du porc. Livest. Prod. Sci., 9 : 349--360 (en anglais). On a r~alisE une expdrience sur 36 porcs en croissance Landrace Danois pour ~tudier l'influence des mati~res grasses (graisses animales) sur leur digestibilit~ et sur le rendement de l'~nergie mEtabolisable. Les porcs (3 port~es pour les femelles et 3 portEes pour les m~les castr~s) ont ~tE rEpartis entre les six regimes alimentaires, intra-port~e et en tenant compte de leur poids vif. La quantit~ ing4r4e des diff~rents regimes a Et~ ajust~e de sorte que le gain de poids journalier soit presque identique pour les diff~rents regimes pendant la totalitE de la p~riode expErimentale, entre 20 et 90 kg. Trois mesures de digestibilit~ et de bilan ont ~t~ effectu~es sur chaque pore. Les animaux ont Et~ abattus ~ un poids d'environ 90 kg, diss~qu~s, broy~s et analys~s. La digestibilit~ des mati~res grasses a augment~ en m~me temps que leur concentration dans le r~gime. L'utilisation de l'~nergie mEtabolisabie a augment~ de 5,0 kJ par g de mati~re grasse digestibles. Les mesures de digestibilitE effectu~es sur des porcs portant une canule ilEo-eaecale montrent que la proportion des mati~res grasses et des acides gras dig~r~s qui disparaft dans le gros intestin diminue en m~me temps que la teneur en mati~res grasses du r4gime augmente. Cela explique la contribution positive des mati~res grasses digestibles ~ la teneur en Energie nette, en plus de leur contribution fi la teneur en ~nergie m~tabolisable. KURZFASSUNG Just, A., 1982. Der Nettoenergiewert von Rohprotein (katabolisiert) fiir das Wachstum bei Schweinen, Livest. Prod. Sci., 9 : 349--360 (auf englisch). Es wurde ein Versuch mit 36 wachsenden Schweinen der D~nischen Landrasse durchgefiihrt, um den Einfluss des verdaulichen Rohproteins auf die Ausscheidung yon Energie im Urin und auf den Ausnutzungsgrad der umsetzbaren Energie zu untersuchen. Die Schweine (aus drei Wiirfen die weiblichen Tiere und aus drei Wiirfen die m~/nnlichen Kastraten) wurden auf sechs Ffitterrungsbehandlungen auf der Basis innerhalb Wurf verteilt unter der Beriicksichtigung des Lebendgewichtes der Schweine. Die t~gliche Aufnahme der versehiedenen Rationen wurde in der Weise festgelegt, dass die t~gliche Zunahme in den verschiedenen Behandlungsgruppen w~hrend des gesamten Versuchszeitraumes yon 20--90 kg ann~'hernd gleich war. Mit jedem Tier wurden drei Verdaulichkeits- und Stickstoff-Bilanz-Versuche durchgefiihrt; mit etwa 90 kg Lebendgewicht wurden die Schweine geschlachtet, zerlegt, homogenisiert und chemiseh analysiert. Der Energieverlust iiber den Urin erh6hte sich um 4,9 kJ und der Ausnutzungsgrad der umsetzbaren Energie erniedrigte sich um etwa 6,6 kJ pro g katabolisiertem Protein. Verdaulichkeitsversuche mit ileo-caecal fistulierten Schweinen zeigten an, dass der Anteil an verdauter Energie, die im Dickdarm verschwand, sich mit steigender Konzentration an Rohprotein in der Ration erh~iht.