The net energy value of crude fat for growth in pigs

Livestock Production Science, 9 (1982) 501--509

501

Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

THE NET ENERGY VALUE OF CRUDE FAT FOR GROWTH IN PIGS

A. JUST

National Institute of Animal Science, Rolighedsvej 25, 1958 Copenhagen V (Denmark) (Accepted 17 November 1981)

ABSTRACT Just, A., 1982. The net energy value of crude fat for growth in pigs. Livesto Prod. Sc~, 9: 501--509. An experiment with 36 growing pigs of Danish Landrace was performed to study the influence of crude (animal) fat on the digestibility of crude fat and on the efficiency of utilization of metabolizable energy. The pigs (females from 3 litters and male castrates from 3 litters) 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 regulated in such a way that the daily gain in the different treatment groups was almost identical throughout the entire experimental period from 20--90 kg. Three digestibility and balance experiments were performed with each pig, and at approximately 90 kg live weight the pigs were killed, dissected, ground, mixed and chemically analysed. The digestibility of crude fat increased with increasing concentration of dietary fat and the efficiency of utilization of metabolizable energy was increased by 5.0 kJ g-' digestible crude fat. Digestibility experiments with ileo-caecal cannulated pigs showed that the proportion of the digested crude fat and fatty acids disappearing in the caecum--colon decreased with increasing concentration of dietary crude fat, which results in a positive contribution of digestible crude fat to net energy besides its contribution to metabolizable energy. INTRODUCTION

Earlier investigations with balanced diets (Just, 1970, 1982a) showed that digestible crude fat improved the efficiency of utilization of metabolizable energy (ME) by 4.8 kJ g-'. The objective of this investigation was to elucidate in more detail the influence of crude fat on the digestibility of crude fat and on the efficiency of utilization of ME. Experiments with ileo-caecal cannulated pigs were performed to study the relationship between diet composition, site of absorption of the nutrients and the utilization of ME. 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 in-

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

502 f o r m a t i o n a b o u t t h e initial c o n t e n t o f energy, p r o t e i n , etc., in t h e e x p e r i m e n tal pigs. T h e r e m a i n i n g six pigs in t h e litter w e r e d i s t r i b u t e d on six d i f f e r e n t diets t a k i n g i n t o a c c o u n t t h e live w e i g h t s o f t h e pigs as d e s c r i b e d b y J u s t ( 1 9 8 2 b). T h u s six pigs w e r e a l l o t t e d t o each d i e t a r y t r e a t m e n t . T h e m a i n f e e d s t u f f c o m p o s i t i o n o f t h e diets is given in T a b l e I. T h e anim a l f a t was p r o d u c e d b y t h e m e a t a n d b o n e m e a l f a c t o r y , " S j a e l l a n d " A.M.B.A., R i n g s t e d , D e n m a r k . I t was a t t e m p t e d t o fulfil t h e p i g s ' d a f f y req u i r e m e n t f o r digestible a m i n o acids, m i n e r a l s a n d v i t a m i n s a c c o r d i n g t o t h e c u r r e n t Danish S t a n d a r d s ( A n d e r s e n a n d J u s t , 1 9 7 9 ) a n d to a v o i d excessive s u p p l y . T h e p r o t e i n r e q u i r e m e n t o f pigs decreases w i t h age or w e i g h t in rel a t i o n t o t h e r e q u i r e m e n t f o r e n e r g y a n d t h e r e f o r e all diets w e r e supplem e n t e d w i t h a p r o t e i n m i x t u r e as d e s c r i b e d in T a b l e I. T h e s u p p l e m e n t a m o u n t e d t o 2 0 0 g / d a y at 20 kg a n d was g r a d u a l l y d e c r e a s e d t o 0 g at app r o x i m a t e l y 70 kg live weight. TABLE I Feedstuff composition of the diets a Diet

1

2

3

4

5

6

% Barley % Wheat bran % Soya meal % Meal and bone meal % Animal fat b % Sugar % Lysine mixture c % Methionine mixture d

79.5 1.9 10.3 2.0 0.9 2.0 0.9 --

66.4 7.9 13.2 2.1 4.9 2.1 0.8 0.1

54.0 13.6 16.0 2.2 8.8 2.2 0.6 0.1

41.0 19.6 19.1 2.3 12.8 2.3 0.3 0.1

28.3 25.3 22.0 2.4 16.7 2.4 0.2 0.1

18.4 28.9 24.6 2.5 20.3 2.5 -0.1

aThe diets were supplemented with a protein mixture consisting of 90.9% soya meal, 2.3% meat and bone meal plus sugar, minerals and vitamins. The daily amounts of the protein supplement were gradually decreased from 200 g per day at 20 kg live weight to 0 g at approximately 70 kg live weight. All diets were added minerals and vitamins according to the current Danish Standards (Andersen and Just, 1979). bStabilized with 500 mg ethoxyquin per kg. c10% L-lysine and 90% wheat bran. d10% DL-methionine and 90% wheat bran.

T h e average c h e m i c a l c o m p o s i t i o n o f t h e diets c o n s u m e d is given in T a b l e II. T h e d i e t a r y c o n c e n t r a t i o n o f c r u d e f a t i n c r e a s e d a l m o s t linearly f r o m 4.4% in D i e t 1 t o 23.6% in D i e t 6. T h e daily a m o u n t s o f t h e diets w e r e regul a t e d in such a w a y t h a t t h e average live w e i g h t o f t h e pigs in t h e d i f f e r e n t t r e a t m e n t g r o u p s was a l m o s t t h e s a m e a t all stages in t h e g r o w t h p e r i o d f r o m 2 0 - - 9 0 k g t o m i n i m i z e v a r i a t i o n s in t h e m a i n t e n a n c e r e q u i r e m e n t . T h r e e digestibility a n d n i t r o g e n b a l a n c e e x p e r i m e n t s w e r e p e r f o r m e d at an even d i s t r i b u t i o n o v e r t h e g r o w t h p e r i o d ( a t a p p r o x i m a t e l y 25, 50 a n d 80 kg) w i t h e a c h pig, i.e., a t o t a l o f 1 0 8 e x p e r i m e n t s .

503 TABLE II Average chemical composition of the diet dry matter Diet

1

2

3

4

5

6

% Crude protein % Stoldt fat a % Crude fibre % NFE % Soluble carbohydrateb % Neutral detergent fibre (NDF)c GE (MJ kg -1 )

18.9 4.4 4.8 66.5 53.5

19.8 8.1 4.8 61.9 49.7

20.7 11.9 5.0 56.8 42.9

21.2 15.6 5.4 51.9 37.5

21.8 19.8 5.6 46.7 31.8

22.3 23.6 5.6 42.1 28.1

17.8 18:23

17.0 19.10

18.9 19.91

19.8 20.61

20.5 20.96

19.6 22.05

aIncluding a hydrolysis with hydrochloric acid prior to the ether extraction (Stoldt, 1957). b Starch plus sugar determined by an enzymatic procedure (Christensen, 1980). c% NDF calculated = % NFE + % crude fibre--% soluble carbohydrate. The influence o f diet c o m p o s i t i o n on the site of absorption of the nutrients was studied using ileo-caecal cannulated pigs. The objective was to elucidate a possible relationship bet w e e n the site of absorption and the efficiency of utilization o f ME, which might explain the significant influence of energy c o n c e n t r a t i o n on ME utilization as f o u n d by Just (1970, 1982a). The digestibility experiments with cannulated pigs were p e r f o r m e d according to a 3 X 3 Latin square design during the growth period from 50--70 kg. Th e diets were c o m p o s e d of the same kind of feedstuffs as used for the balance-slaughter investigations and the c om posi t i on was m e a n t t o be identical with t h a t of Diet 1, t he mean of Diets 3 and 4, and Diet 6, but due to technical errors more fat was adm i xe d with the diets at the fabrication than was intended. Th e f a t t y acid c o m p o s i t i o n and the ileal and overall digestibility o f the individual f a t t y acids are described by Just et al. (1980b). The balance-slaughter investigations, the experiments with cannulated pigs, the chemical analyses, the statistical analyses, etc., were p e r f o r m e d as described by Just ( 1 9 8 2 a , b). More details a b o u t digestibility experiments with cannulated pigs are given by Just et al. (1980a,b). RESULTS AND DISCUSSION Th e pigs in the balance-slaughter investigation were in good health e x c e p t one in G r o u p 2, which was t h e r e f o r e discounted. T he appetite and daily gain were satisfactory. T he main average results are shown in Table III. T he digestibility o f crude fat increased with increasing dietary c o n t e n t , partly because the added animal fat has a higher digestibility t han the crude fat o f the o t h e r feedstuffs in t he diets, and partly because the a m o u n t o f endogenous f a e c ~ fat varies t o g e t h e r with the a m o u n t and c o m p o s i t i o n o f diet dry

504 TABLE III

The influence of dietary fat on the digestibility, metabolizability and the utilization of ME (n=35) Diet

1

2

3

4

5

6

Feed intake, gain and carcass weight DM (kg/day) ME (MJ/day) Gain (g/day) a

Carcass weight (kg) Digestibility (%) Crude protein Stoldt fat Crude fibre NFE

Soluble carbohydrate Energy

1.54 21.89 595 68.9

1.43 21.52 626 69.2

1.43 21.88 604 69.2

1.39 21.49 606 69.8

1.32 21.71 650 70.9

1.28 21.52 630 70.0

80 56 32 91 99 81

82 70 40 91 99 82

80 74 35 89 98 80

79 75 38 88 98 79

82 80 44 88 98 81

80 81 45 87 98 80

0.56 14.21 78 96

0.62 15.08 79 96

0.67 15.29 77 96

0.73 15.49 75 96

0.73 16.48 77 96

0.78 16.87 77 96

4.93 9.19

5.25 9.88

5.58 10.13

5.96 10.71

6.38 11.38

6.60 11.76

36 66

38 69

39 69

39 70

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 b (MJ/kg DM)

Deposited energy (% of ME) NE b (% of ME)

35 65

35 66

aAdjusted to 25% slaughter loss, i.e.,carcass weight/0.75. bNE, M J = deposited energy, M J ÷ 0.326 M J × average live weight, kg °'Ts.

matter (Just, 1970; Sundstol, 1974) and therefore exerts a greater negative effect on low fat diets than on high fat diets. The analytical procedure has a large influence on the calculated digestibility of fat and fatty acids especially because a major part of the total lipid content o f faeces is saponified. Simple extraction with ether will not remove these soaps and therefore the estimated digestibility will be too high. That problem can be overcome by performing a hydrolysis with hydrochloric acid prior to the ether extraction (Stoldt, 1957; Sundst~bl, 1974; Just, 1976; Kidder and Manners, 1978). The digestibility of fat is influenced by several dietary factors such as type of starch or crude fibre (Just and Mason, 1974; Just et al., 1976, 1980b), type or nature of fat (Madsen, 1963; Carlson and Bayley, 1968; Braude and Newport, 1973; Sundst~l, 1974), and age or weight of the pigs (Cunningham and Brisson, 1955; Lloyd et al., 1957; J~brgensen et al., 1978}. A detailed review

505

of the factors influencing the digestibility of fat is given by Kidder and Manners (1978). The digestibility of crude fibre increased with increasing concentration of dietary fat probably due to the fact that a larger proportion of the crude fibre originated from soya meal, which has a higher digestibility (75%) than crude fibre from barley and wheat bran (20%). The decreasing digestibility of NFE-substances and soluble carbohydrates corresponds to the increasing inclusion of wheat bran in the diets. Energy losses into urine and ME in per cent of DE were independent of the diet composition, whereas the utilization of ME increased with increasing c o n t e n t of dietary fat as found by Just (1970, 1982a). The results obtained with cannulated pigs are shown in Table IV. The trend in the digestibility coefficients is similar to that in Table III, but the digestibility is a few units higher in most cases. The explanation may be that these diets were finely ground, to avoid blocking the cannulae, and digestibility increases with increasing fineness of the material (Just, 1978). The use of chromic oxide as a marker, instead of quantitative collection, may also inTABLE IV The influence of dietary fat on 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 % Digested (A) and % of Crude protein Crude protein Lysine Lysine Stoldt fat Stoldt fat Linoleic acid Linoleic acid Crude fibre Crude fibre Soluble carbohydrate Soluble carbohydrate Energy Energy

I

II

20.0 4.5 5.5 1.41

III

20.1 17.0 5.6 1.42

20.7 26.8 5.7 1.42

digested disappearing in caecum--colon (B) A* 82 81 85 B 10 10 11 A 83 84 87 B 0 0 2 A* 69 84 87 B* 17 3 1 A 99 99 99 B 29 14 9 A* 34 35 42 B 100 100 100 A 100 100 99 B 5 5 6 A 82 82 82 B 21 18 16

*The difference between diets is statistically significant (P ~ 0.05).

506 f l u e n c e t h e c a l c u l a t e d digestibility, as well as t h e f a c t t h a t t h e f e e d s t u f f s u s e d in t h e t w o investigations were f r o m d i f f e r e n t b a t c h e s . All t h e d i g e s t e d c r u d e f i b r e was a p p a r e n t l y d e g r a d e d in t h e h i n d gut. T h e d i e t a r y c o n t e n t o f c r u d e f a t h a d a significant i n f l u e n c e o n t h e p r o p o r t i o n o f t h e digested f a t a n d linoleic acid d i s a p p e a r i n g in t h e h i n d gut. T h e higher t h e d i e t a r y c o n c e n t r a t i o n , t h e g r e a t e r t h e p r o p o r t i o n o f f a t a b s o r b e d in t h e small i n t e s t i n e a n d t h e smaller t h e p r o p o r t i o n t h a t d i s a p p e a r e d in t h e h i n d gut. As a c o n s e q u e n c e o f t h e site o f n u t r i e n t a b s o r p t i o n , t h e p r o p o r t i o n o f t h e digested e n e r g y d i s a p p e a r i n g in t h e h i n d g u t d e c r e a s e d With increasing c o n c e n t r a t i o n o f d i e t a r y fat. The relationship between the concentration of dietary crude fat and the u t i l i z a t i o n o f ME is e l u c i d a t e d in T a b l e V b y t h e results o f regression analysis. E q u a t i o n s 1 a n d 2 s h o w t h a t t h e digestible c r u d e f a t increased t h e daily e n e r g y d e p o s i t i o n a n d t h e d a i l y a m o u n t o f N E b y 5.0 a n d 5.1 k J g - ' , respectively. T h i s is in a g r e e m e n t w i t h J u s t ( 1 9 7 0 ) , w h o f o u n d t h a t digestible c r u d e f a t m a d e a p o s i t i v e c o n t r i b u t i o n o f 4.8 k J p e r g t o d e p o s i t e d e n e r g y in a d d i t i o n t o its c o n t r i b u t i o n t o ME. TABLE V Equations elucidating the effect of digestible crude fat on the efficiency of utilization of ME (n=35) Deposited energy, kJ/day = 7335 + 5.0 x digestible crude fat (g/day) Sb

=

1.0;

tb =

4.7; CV = 5,4, r 2= 0.76

(1)

NE a, kJ/day = 13877 + 5.1 × digestible crude fat (g/day) s b = 1.0; t b =

4.9; CV = 3.0; r 2 = 0.75

(2)

Deposited energy, MJ/kg DM = -4.07 + 0.63 ME, MJ/kg DM sb

= 0.06;

tb =

10.0; CV = 5.9; r 2 = 0.83

(3)

NE a, MJ/kg DM = - 4 . 4 4 + 0.96 ME, MJ/kg DM sb

= 0.07;

tb =

13.8; CV = 3.5; r 2 = 0.88

(4)

aNE, MJ = deposited energy, MJ + 0.326 MJ X average live weight, kg '°'~j . T h e e f f i c i e n c y o f u t i l i z a t i o n o f ME i n c r e a s e d w i t h increasing e n e r g y conc e n t r a t i o n as s h o w n b y t h e eqs. 3 a n d 4. A similar result was f o u n d b y J u s t (1970, 1982a). Based o n b i o c h e m i c a l c o n s i d e r a t i o n s H o f f m a n n ( 1 9 6 5 ) c a l c u l a t e d t h e NE value o f digestible c r u d e f a t t o be w i t h i n 8 0 - - 9 5 % o f t h e ME value a n d acc o r d i n g t o t h e e q u a t i o n s p u b l i s h e d b y S c h i e m a n n e t al. ( 1 9 7 1 ) t h e N E value o f c r u d e f a t is 91% o f t h e ME value or 36.1 k J g - ' . H o w e v e r , t h e regression was f i x e d at t h e z e r o p o i n t a n d t h e value o f t h e regression c o e f f i c i e n t s was l i m i t e d t o w i t h i n t h e r a n g e e s t i m a t e d o n basis o f t h e b i o c h e m i c a l considerations.

507 Regardless o f w h e t h e r t he c o n t r i b u t i o n of digestible crude fat to NE in addition to its c o n t r i b u t i o n t o ME (5.1 kJ ~-1) is added to the ME value (36.1 kJ g-l) f o u n d by Schiemann et al. (1971) or t o the ME value (37.7 kJ g-l) f o u n d by Just (1970, 1982a) the efficiency of utilization of fat ME becomes higher than 100%. Initially, one would say t hat this efficiency of utilization must be erroneous. With regard t o the biochemical effect of the fat, it must certainly be a t y p e of artifact, but taking into a c c o u n t t he site of absorption o f the crude fat and the energy (Table IV}, the overall effect could very well be real. In the regression analysis the increased value of ME due to site of absorption and the decrease in the fermentative processes is " c o n f o u n d e d " with the a m o u n t o f dietary crude fat, which m os t likely has resulted in regression coefficients overestimating the biochemical value o f the digested crude fat per se, but nevertheless the regression coefficients m ay be realistic estimates of the energetic p r o d u c t i o n value of the fat in the diets. T h e positive ef f ect o f energy c o n c e n t r a t i o n on the efficiency of utilization o f ME (eqs. 3 and 4) is pr oba bl y also due t o the influence of the site of absorption and the size of the fermentative processes in the hind gut, which in turn depends on the chemical composition, and the a m o u n t of diet dry matter.

REFERENCES Andersen, P.E. and Just, A., 1979. Tabeller over fodermidlers sammensmtning m.m.K. Dan. Landhusholdningsselskab, K~bbenhavn, 56 pp. Braude, R. and Newport, M.J., 1973. Artificialrearing of pigs. Br. J. Nutr., 29: 447--455. Carlson, W.E. and Bayley, H.S., 1968. Utilization of fat by young pigs. Can. J. Anita. Sci.,

48: 315--322. Christensen, K.D., 1980. Bestemmeise af letopl~selige og lethydrolyserbare kulhydrater (LHK). Ugeskr. Jordbr., 12: 340. Cunningham, H.M. and Brisson, G.J., 1955. The utilization of lard by baby pigs. Can. J. Agric. Sci., 35: 371--376. Hoffmann, L., 1965. Modellvorstellungen zur Leistungsvorhersage auf der Basis der Nettoenergie und der umsetzbaren Energie. Arch. Tierern~ihr., 15: 487--506. JSrgensen, H., Just, A. and Fekadu, M., 1978. Formalingsgradens og traestofkoncentrationens indflydelse ph foderets fordSjelighed hos svin af forskellig alder (vaegt). 230, Medd. Statens Husdyrbrugs-Fors~g, KSbenhavn, 4 pp. Just (Nielsen), A., 1970. Alsidige foderrationers energetiske vaerdi til vaekst hos svin belyst ved forskellig metodik. 381. Beretn. ForsSgslab., KSbenhavn, 212 pp. Just, A., 1976. Factors affecting feed conversion under practical farm conditions. Some qualitative aspects of pig nutrition. 27th Annual Meeting EAAP, Ziirich, 31 pp. Just, A., 1978. The influence of processing on the nutritive value of cereals for pigs. 29th Annual Meeting EAAP, Stockholm, 9 pp. Just, A., 1981. The net energy value of balanced diets for growth in pigs. Livest. Prod. Sci., 8: 541--555. Just, A., 1982b. The net energy value of crude (catabolized) protein for growth in pigs. Livest. Prod. Sci., 9: 349--360.

508 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. 6th Symposium on energy metabolism of farm animals, Stuttgart. E A A P publ., 14: 193--196. Just, A., Rasmussen, O.K. and Hansen, H.L., 1976. Factors influencing the digestibility and efficiency of utilization of metabolizable energy in diets for growing pigs. 7th Symposium on energy metabolism of farm animals, Vichy. E A A P publ., 19: 289--292. Just, A., Sauer, W.C., Bech-Andersen, S., J~rgensen, 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~'hr. Futtermittelkd., 43: 83--91. Just, A., Andersen, J.O. and J~rgensen, H.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~hr. Futtermittelkd., 44: 82--92. Kidder, D.E. and Manners, M.J., 1978. Digestion in the pig. Scientechnica, Bristol, 201 pp. Lloyd, L.E., Crampton, E.W. and Mackay, V.G., 1957. The digestibility of ration nutrients by three versus seven week old pigs. J. Anita. Sci., 16: 383--388. Madsen, A., 1963. Ford~bjelighedsfors~g reed svin. 337, Beretn. Fors~bgslab., K~$benhavn, 191 pp. Schiemann, R., Nehring, K., Hoffmann, L., Jentsch, W. and Chudy, A., 1971. Energetisehe Futterbewertung und Energienormen. VEB Deutscher Landwirtschaftsverlag, Berlin, 344 pp. Stoldt, W., 1957. Mitteilung der Fachgruppe Futtermitteluntersuchung. Landwirtsch. Forsch., 10: 273--275. Sundst~l, F., 1974. Hydrogenated marine fat as feed supplement. Report No. 159, Agricultural University of Norway, 200 pp.

RESUME Just, A., 1982. Valeur dnerg~tique nette des mati~res grasses pour la croissance du porc. Livest. Prod, Sci., 9:501--509 (en anglais). O n a r~alis~ une experience 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 m~tabolisable. Les porcs (3 port~es pour les femelles et 3 port~es pour les males castr~s) ont ~t~ r~partis entre les six r~gimes alimentaires, intra-port~e et en tenant compte de leur poids vif. La quantitfi ing~r~e des difffirentsr~gimes a ~t~ ajust~e de sorte que le gain de poids journalier soit presque identique pour les diff~rents r~gimes pendant la totalit~ de la p~riode exp~ri~ mentale, entre 20 et 90 kg. Trois mesures de digestibilit~ et de bilan ont ~t~ effectu~es sur chaque porc. Les animaux ont ~t~ abattus a un poids d'environ 90 kg, diss~qu~s, broy~s et analys~s. La digestibilitd des mati~res grasses a augrnentfi en m ~ m e temps que leur concentration dans le r~gime. L'utilisation de l'~nergie m~tabolisable a augment~ de 5,0 kJ par g de mati~res grasses digestibles. Les mesures de digestibilit~ effectu~es sur des porcs portant une canule il~o-caecale montrent que la proportion des mati~res grasses et des acides grasses dig~r~s qui disparait darts la gros intestin diminue en m ~ m e temps que la teneur en mati~res grasses du r~gime augmente. Cela explique la contribution positive des mati~res grasses digestibles ~ la teneur en ~nergie nette, en plus de leur contribution ~ la teneur en ~nergie m~tabolisable. KURZFASSUNG

Just, A., 1982. Der Nettoenergiewert yon Rohfett ftir das Wachstum bei Schweinen. Livest. Prod. Sci., 9 : 5 0 1 - - 5 0 9 (auf englisch).

509 Es wurde ein Versuch wit 36 wachsenden Schweinen der D~nischen Landrasse durchgefiihrt, um den Einfluss des Rohfettes (tierisches Fett) auf seine Verdaulichkeit 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 Fiitterungbehandlungen auf der Basis innerhalb Wurf verteilt unter Beriicksichtigung des Lebendgewichtes der Schweine. Die t~gliche Aufnahme der verschiedenen Rationen wurde in der Weise reguliert, dass die t~gliche Zunahme in den verschiedenen Behandlungsgruppen w~/hrend des gesamten Versuchszeitraumes von 20--90 kg ann~hernd gleich war. Mit jedem Tier wurden drei Verdaulichkeits- und Stickstoff-Bilanzversuche durchgefiihrt; mit etwa 90 kg Lebendgewicht wurden die Schweine geschlachtet, zerlegt, homogenisiert u n d chemisch analysiert. Die Verdaulichkeit des Rohfettes erh~hte sich mit steigender Konzentration yon Fett in der Ration und der Ausnutzungsgrad der urnsetzbaren Energie wurde um 5.0 kJ g-~ verdaulichem Rohfett erh~ht. Verdaulichkeitsversuche mit ileo-caecal fistulierten Schweinen zeigten bei zunehmender Rohfettkonzentration in der Ration eine Abnahme des Anteiles an verdautem Rohfett und Fetts~iuren, die im Dickdarm verschwanden; dies resultierte in einem positiven Beitrag des verdaulichen Rohfettes zur Nettoenergie neben seinem Beitrag zur umsetzbaren Energie.