Effect of monensin on rumen fermentation, performance and body composition of growing bulls

Livestock Production Science, 8 (1982) 479--488

479

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

EFFECT OF MONENSIN ON RUMEN FERMENTATION, PERFORMANCE AND BODY COMPOSITION OF GROWING BULLS

R. D A E N I C K E , K. R O H R

and H.J. O S L A G E

Institute of Animal Nutrition, Federal Research Center of Agriculture, BraunschweigVSlkenrode (FAL) (W. Germany) (Accepted 17 September 1981)

ABSTRACT Daenicke, R., Rohr, K. and Oslage, H.J., 1982. Effect of monensin on rumen fermentation, performance and body composition of growing bulls. Livest. Prod. Sci., 8: 479--488. The influence of monensin on growth performance, chemical body composition and tureen fermentation was studied in an experiment with 2 × 12 German Friesian bulls (live weight range: 146--555 kg). All bulls were offered the same amounts of concentrates (2.3 up to 3.0 kg per day) and maize silage (in the milky stage) to 90--95% of their ad libitum intake. Animals of the experimental group were given 30 mg monensin per kg feed on an 88% dry matter basis, i.e., increasing amounts from 100 mg to 270 mg monensin per animal per day. Animals of the control group were fed without any growth promoting substance. The results can be summarized as follows: (1) Though feed- and nutrient intakes were the same, the bulls of the monensin group showed 4.8% higher daily empty body gains as compared to those of the control group. This resulted in 5.1% better feed efficiency. Differences were not significant. (2) Protein content in empty body was not significantly affected by monensin; fat content, however, was significantly increased (15.3%). Daily energy retention was calculated to be 15.9% higher in the monensin group when compared to the control group. (3) Propionate concentration in r u m e n fluid significantly increased, concentration of acetate and butyrate significantly decreased by monensin treatment. Thus it can be concluded, that the higher energy retention of the monensin fed bulls resulted from a more efficient energy utilisation.

INTRODUCTION

Monensin sodium is a growth promoting substance which is produced b y

Streptomyces cinna-monensis in a fermentation process. Its positive effect on feedlot performance has been shown in many experiments with bulls and steers. In most cases there was an improvement in feed efficiency in the range of 5--10%. This improvement was due to a decrease in feed intake with unaffected growth rate (Gill et al., 1976; Perry et al., 1976; Dinius and Baile, 1977; Geay and B~ranger, 1977; Lettner and Nies, 1977; Byers, 1980) or to an increase of daffy gain with similar intake (Oliver, 1975; Dinius et al., 1978; Soller and Pfeffer, 1979) or to higher gains with even lower intakes

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

480

(Davis and Erhart, 1976; Potter et al., 1976; Raun et al., 1976; Boling et al., 1977; Mowat et al., 1977; Steen et al., 1978; Henning et al., 1979). So far it has not been clarified completely by which mechanism this improvement is achieved. There is wide agreement that by the addition of monensin, the proportion of propionic acid in the r u m e n is increased, while that of acetic and butyric acids is decreased (Perry et al., 1976; Richardson et al., 1976; Boling et al., 1977; Mowat et al., 1977; Prange et al., 1978). Other experiments have shown that methane production was dramatically decreased by addition of monensin to steer rations (Thornton et al., 1976) or lamb rations (Joyner et al., 1979). F r o m this it can be concluded that monensin results in a more efficient energy utilisation. Thus, J o y n e r et al. (1979) have shown in an experiment with lambs, that the proportion of dietary energy retained was increased by monensin treatment. Potter et al. (1976) estimated protein-, fat- and energy retention of steers and heifers by carcass data and found no effect of monensin supplementation. Since cattle fed monensin consumed less feed, the percentage of dietary energy and protein retained in the carcass was increased. Byers (1980), however, calculated from carcass specific growing measurements in steers that monensin may decrease maintenance requirements and (or) increase efficiency of energy utilisation for maintenance. The objective of this investigation was to determine the effects of monensin on rumen fermentation, performance and body composition of growing bulls. MATERIALS AND METHODS For the experiment 24 male calves (German Friesians) were reared with liquid milk replacer (42 days), concentrates and hay up to live weights of about 145 kg. At the beginning of the experiment they were randomly allotted to 2 groups of 12 bulls each. Daffy gains from the beginning to the end of the preliminary rearing period were 754 g (control group) and 756 g (experimental group). Animals were fed the amounts of feed given in Table I. According to previous experiments at this institute, these amounts of feed were equivalent to 90--95% ad libitum intake. Animals of the experimental group were given 30 mg monensin per kg feed on an 88% dry matter basis, i.e., increasing amounts from 100 mg to 270 mg monensin per animal per day. Animals of the control group were fed without any growth promoting substance. Chemical composition and nutritive value of the feedstuffs are listed in Table II. Maize silage was analysed weekly, concentrate every 4 weeks. Sheep were used to measure digestibility of maize silage. Digestible crude protein and SE content in soybean meal and concentrate mixtures were derived from feedstuff tables (Deutsche Landwirtschaftsgesellschaft, 1968). The animals were tethered in a stable without bedding and were fed indi-

481 TABLE

I

Feeding plan L i v e weight range

up to 150 151--200 201--250 251--300 301--350 351--400 401--450 451--500 5 0 0 to e n d

B o t h groups C o n t r o l group

M o n e n s i n group

Maize silage dry matter

Concentrate m i x t u r e A*

Soybean meal

Concentrate m i x t u r e A*

Concentrate Soybean m i x t u r e B** meal

Monensin intake

(kg/day)

(kg/day)

(kg/day)

(kg/day)

(kg/day)

(kg/day)

(mg/day)

1.2 1.6 2.4 3.2 4.0 4.4 4.6 4.8 5.0

2.2 2.2 2.4 2.4 2.5 2.6 2.7 2.8 3.0

0.1 0.1 0.05 -------

1.2 0.9 0.8 0.5 0.4 0.3 0.3 0.3 0.3

1.0 1.3 1.6 1.9 2.1 2.3 2.4 2.5 2.7

0.1 0.1 0.05 -------

100 130 160 190 210 230 240 250 270

*I kg Concentrate mixture A contained: 300 g soybean meal, 260 g oats, 200 g barley, 120 g wheat bran, 5 0 g t a p i o c a , 2 0 g s o y b e a n oil, 5 0 g minerals and vitamins. * * C o n c e n t r a t e m i x t u r e B: same c o m p o s i t i o n as c o n c e n t r a t e m i x t u r e A , h o w e v e r , c o n t a i n i n g 1 0 0 m g m o n e n s i n per k g .

TABLE

II

Chemical c o m p o s i t i o n and nutritive value o f the f e e d s t u f f s Feedstuffs

Maize silage Concentrate mixture* Soybean meal

No. of samples

Dry matter

Crude protein

Crude fat

Crude fibre

(%)

(%)

(%)

(%)

NfE (%)

DCP (g)

N e t energy (SE)

56

28.5

2.6

0.9

6.3

17.0

14

175

12

87.8

19.2

4.7

7.1

49.2

168

657

12

86.5

41.6

1.8

6.6

30.3

387

688

* C o m p o s i t i o n see Table I.

vidually twice a day. Weighing of the bulls was done before the morning feed once a week and for 3 consecutive days at the beginning and the end of the experiment, so that initial and final live weights are the average of 3 measurements. Twice during the fattening period (about 300 kg and 400 kg live weight) rumen samples were taken from all bulls by stomach tube 3 h after the morning feed. Volatile fatty acids in tureen liquor were measured by the method of Honig and Rohr (1973). All bulls were killed in the slaughterhouse of the institute. They received their last meal 24 h before slaughtering. The empty bodies were dissected into several fractions (muscles, adipose tissue, skin, bones, internal organs and offal, blood) and analysed for their chemical composition (dry matter, protein, fat, ash) by methods which have been described previously (Schulz et al., 1974). Some relevant details of empty body analysis are: Dry matter: Oven drying after treatment with methanol. Adipose tissue at 95°C, other fractions at 105°C.

482

Protein: Kjeldahl method. Total a m o u n t of N multiplied b y 6.25. Fat: Pre-extraction with ether, residue treated with HC1. Ash: Oven, temperature 550 ° C. Gains in protein, fat and energy were calculated b y subtracting the respective initial amounts analysed in 5 calves from a previous experiment. All data were statistically analysed. Means of the experimental group were compared to those of the control group using the Student t test. RESULTS

Feed and nutrient intake Data on intake of feeds, dry matter, digestible crude protein, metabolisable energy and net energy are given in Table III. TABLE III Feed and nutrient intake Item

Control

Monensin -+ s.d.

Concentrate mixture (kg/day) Maize silage (kg/day) Dry matter (kg/day) Digestible crude protein (g/day) Metabolisable energy* (MJ/day) Net energy (SE/day)

2.6 13.3 6.1 635 69.2 4076

0.05 0.45 0.14 12 1.9 120

~

2.6 13.4 6.1 633 69.2 4077

-+ s.d.

0.03 0.56 0.19 12 2.2 130

*Calculated after Schiemann et al., 1971.

As can be seen from this table, feed consumption as well as dry matter and nutrient intake were the same in b o t h groups. There were no feed refusals.

Rumen fermentation Results on volatile f a t t y acid concentration in rumen liquor are shown in Table IV. Large differences can be seen between groups: Monensin caused a substantial increase of propionate (P < 0.001) in rumen fluid with a corresponding decrease in acetate (P < 0.001) and to some degree in butyrate (n.s., P < 0.01) concentration.

Growth performance and feed efficiency Results on weight gains and feed efficiency are summarized in Table V.

483 TABLE IV Volatile fatty acids in the rumen fluid Item

Control £

Monensin

± s.d.

Statistical significance*

± s.d.

£

300 kg live weight Acetic acid (Molar %) Propionic acid (Molar %) Butyric acid (Molar %)

75.5 13.4 9.8

4.2 3.9 4.9

59.1 31.0 7.1

5.1 7.1 3.6

*** *** n.s.

76.0 12.3 10.4

4.9 4.7 3.9

63.0 26.8 5.6

3.7 6.5 2.4

*** *** **

400 kg live weight Acetic acid (Molar %) Propionic acid (Molar %) Butyric acid (Molar %)

*n.s. = not significant, **P < 0.01, ***P < 0.001.

TABLE V Weights, daily gains and feed conversion ratio Item

Control

Monensin ± s.d.

± s.d.

Statistical significance*

Initial live weight (kg) Final live weight (kg)

146.0 557.3

6.6 12.9

146.3 555.6

4.6 6.0

n.s. n.s.

initialempty body weight** (kg) Finalempty body weight (kg)

118.5 480.7

5.3 6.7

118.8 486.8

3.7 8.0

n.s. n.s.

Live weight gain (g/day) Empty body weight gain (g/day)

1112 979

122 100

1141 1026

89 71

n.s. n.s.

Net energy/live weight gain (SE/kg) 3706 Net e n e r g y / e m p t y body weight gain (SE/kg) 4211

527

3594

329

n.s.

522

3995

333

n.s.

*n.s. = not significant. * * E m p t y body weight = live weight minus contents of intestine, urine- and gall bladder. Initial empty body weights were calculated.

Though final live weight in the control group was nearly 2 kg higher than in the monensin group, the empty body weight at the end of the experiment was about 6 kg higher in the latter.This was due to a lower amount of gut contents. Daily live weight gain was improved by 2.6%, daily empty body

484

gain increased by 4.8% in the monensin group. Feed efficiency (starch equivalents per kg gain) was positively influenced by monensin supplementation. The improvement was 3.0% referred to live weight gain and 5.1% referred to empty body gain. On account of the large standard deviations differences were not significant.

Body composition, daily protein, fat and energy accretion Chemical composition of empty bodies at the end of the experiment as well as daffy accretion of protein, fat and energy are shown in Table VI. TABLE VI Chemical composition of empty bodies, daily protein, fat and energy accretion Item

Control

Monensin +

s.d.

~

-+ s.d.

Statistical significance a

Empt y body composition Protein (%) Fat (%) Ash (%) Water (%)

18.0 20.2 4.8 56.9

0.5 2.9 0.5 2.3

17.6 23.3 4.4 54.7

1.0 3.7 0.5 2.6

n.s. * * *

173 238 13.2

19 37 1.5

175 292 15.3

18 53 1.9

n.s. ** **

Accretion Protein (g/day) Fat (g/day) Energy (MJ/day) b

an.s. = not significant, * = P < 0.05, ** = P < 0.01. bCalculated: 22.6 kJ/g protein, 39.0 kJ/g fat ( B S h m e

and G~/deken, 1980).

Protein content did not differ significantly between groups, while the other fractions changed significantly. Fat percentage increased relatively by 15.3%, ash content decreased by a relative 8.3% in the monensin group. The decrease in ash content was mainly due to a lower proportion of bones in the empty bodies of the monensin fed bulls. Corresponding to the change in fat content, water content decreased in the experimental group. Daily protein accretion was not significantly affected by monensin, however, daily fat accretion was significantly increased by 22.6%. This results in a 15.9% higher daily energy retention in the monensin group as compared to the control group.

485 DISCUSSION AND CONCLUSIONS

In this experiment with intensively fed Friesian bulls, the addition of monensin sodium did not affect feed intake. This may be explained by the fact that the animals of the control group as well as those of the experimental group were only offered 90--95% of their ad libitum intake. In spite of identical energy intakes, empty body weight gain (EBWG) and feed efficiency were improved by 4.8% and 5.1%, respectively, in the monensin group. As shown in Table VI, the higher EBWG was largely due to an increase in fat accretion; protein accretion was unaffected. A potential influence of monensin on rumen nitrogen metabolism (Poos et al., 1979: Thompson and Riley, 1980) probably did not affect N retention. This is because crude protein of between 18.0% in DM (at the beginning) and 13.5% (at the end of the fattening period) was well in excess of the animals' requirements (Rohr et al., 1981). Though monensin did not affect N retention of Friesian bulls, it cannot be excluded that bulls of higher muscular potential would have deposited more protein in response to this polyether antibiotic. There may be two reasons for a higher fat and energy deposition at equal energy intake in the monensin group: first, a lower maintenance requirement (Byers, 1980) and secondly, an improved efficiency of energy utilisation. Most experimental data support the second explanation. Certainly, the improvement in energy utilisation is not due to an increase in digestibility (Soller and Pfeffer, 1980) but rather to an increase in metabolisability. The authors' results on rumen fermentation agree with those of other workers, in that propionate production is remarkably increased. This increase in propionate and the corresponding decrease in methane (Thornton et al., 1976; Joyner et al., 1979) result in a higher content of metabolisable energy (ME) of the diet. In our opinion, ME-values should be corrected when using monensin as a growth promoting substance for growing bulls. The ME-values for the monensin group in Table III should thus be increased by some 4.6% (72.4 MJ instead of 69.2 MJ), if kf-values of 0.65 are applied.

REFERENCES BShme, H. and G~ideken, D., 1980. Der Brennwert von K6rperprotein und KSrperfett von Schweinen und Rindern unterschiedlicher Lebendmasse. Z. Tierphysiol., Tierernaehr, Futtermittelkde., 44: 165--171. Boling, J.A., Bradley, N.W. and Campbell, L.D., 1977. Monensin levels for growing and finishing steers. J. Anita. Sci., 44: 867--871. Byers, F.M., 1980. Determining effects of monensin on energy value of corn silage diets for beef cattle by linear or semi-log methods. J. Anita. Sci., 51: 158--169. Davis, G.V. and Erhart, A.B., 1976. Effects of monensin and urea in finishing steer rations. J. Anita. Sci., 43: 1--8. Dinius, D.A. and Baile, G.A., 1977. Beef cattle response to a feed intake stimulant given alone and in combination with a propionate enhancer and an anabolic agent. J. Anita. Sci., 45: 147--153.

486

Dinius, D.A., Goering, H.K., Oltjen, R.R. and Cross, H.R., 1978. Finishing beef steers on forage diets with additives and supplemental lipid. J. Anita. Sci., 46: 761--768. Geay, Y. and B~ranger, C., 1977. Utilisation d ' u n anticoccidien (Monensin) dans la ration des ruminants. 1. Effets sur les performances d'engraissement des taurillons. Ann. Zootech., 26: 59--68. Gill, D.R., Martin, J.R. and Lake, R., 1976. High, medium and low corn silage diets with and without monensin for feedlot steers. J. Anita. Sci., 43 : 363--368. Henning, A., Flachowsky, G., Wolfram, D., Stubendorff, G., Geissler, Ch., Flachowsky, E. and Richter, G., 1979. Untersuchungen zum Einsatz des Pansenfermoregulators "Monensin" in der Mastbullenfiitterung. Arch. Tierernaehr., 29: 731--741. Honig, H. and Rohr, K., 1973. Uber den Einfluss yon Formalin und formalinhaltigen Zusatzmitteln auf den Silierverlauf und die Vormagenverdauung bei Milchkiihen. Wirtschaftseigene Futter, 19: 21--30. Joyner, A.E., Brown, L.J., Fogg, T.J. and Rossi, R.T., 1979. Effect of monensin on growth, feed efficiency and energy metabolism of lambs. J. Anita. Sci., 48: 1065--1069. Lettner, F. and Nies, W., 1977. Einsatz des Wirkstoffes Rumensin in der Rindermast mit Maissilage. Paper presented at the 28th meeting of the EAAP, Brussels. Mowat, D.N., Wilton, J.W. and Buchanan-Smith, J.G., 1977. Monensin fed to growing and finishing cattle. Canad. J. Anita. Sci., 57: 769--773. Oliver, W.M., 1975. Effect of monensin on gains of steers on coastal bermuda grass. J. Anim. Sci., 41: 999--1001. Perry, T.W., Beeson, W.M. and Mohler, M.T., 1976. Effect of monensin on beef cattle performance. J. Anim. Sci., 43: 761--765. Poos, M.J., Hanson, T.L. and Klopfenstein, T.J., 1979. Monensin effects on diet digestibility, ruminal protein bypass and microbial protein synthesis. J. Anita. Sci., 48: 1516-1524. Potter, E.C., Cooley, C.O., Richardson, L.F., Raun, A.R. and Rathmacher, R.P., 1976. Effect of monensin on performance of cattle fed forage. J. Anita. Sci., 43: 665---669. Prange, R.W., Davis, C.L. and Clark, J.H., 1978. Propionate production in the rumen of Holstein steers fed either a control or monensin supplemented diet. J. Anita. Sci., 46: 1120--1124. Raun, A.P., Cooley, C.O., Potter, E.L., Rathmacher, R.P. and Richardson, L.F., 1976. Effect of monensin on feed efficiency of feedlot cattle. J. Anim. Sci., 43: 670--677. Riclaardson, L.F., Raun, A.P., Potter, E.L., Cooley, C.O. and Rathmacher, R.P., 1976. Effect of monensin on rumen fermentation in vitro and in vivo. J. Anita. Sci., 43 : 657--664. Rohr, K., Daenicke, R. and Oslage, H.J., 1981. The optimum protein supply for young fattening bulls on a high-energy level. Proceedings of the Symposium on observations on the practical use of new sources of protein in relation to energy supply for high production of milk and meat. Pergamon, Oxford, in press. Schiemann, R., Nehring, K., Hoffmann, L., Jentsch, W. and Chudy, A., 1971. Energetische Futterbewertung und Energienormen. VEB Deutscher Landwirtschaftsverlag, Berlin, p. 120. Soller, H. and Pfeffer, E., 1979. Untersuchungen iiber den Einfluss yon Monensin auf die Futterverwertung bei der Bullenmast mit Mais- und Riibenblattsilage. Ziichtungskunde, 51: 392--400. Soller, H. and Pfeffer, E., 1980. Weitere Untersuchungen iiber die Wirkung yon Monensin beim Einsatz in der Bullenmast. Ziichtungskunde, 52: 36--39. Schulz, E., Oslage, H.J. and Daenicke, R., 1974, Untersuchungen fiber die Zusammensetzung der KSrpersubstanz sowie den Stoff- und Energieansatz bei wachsenden Mastbullen. Fortschritte in der Tierphysiologie und Tierern~hrung. H. 4. Paul Parey, Hamburg und Berlin. Steen, W.W., Gay, N., Boling, J.A., Bradley, N.W., McCormick, J.W. and Pendlum, L.C., 1978. Effect of monensin on performance and plasma metabolites in growing finishing steers. J. Anim. Sci., 46: 350--355.

487 Thompson, W.R. and Riley, J.G., 1980. Protein levels with and without monensin for finishing steers. J. Anim. Sci., 50: 563--571. Thornton, J.H., Owen, F.N., Lemenager, R.P. and Totusek, R., 1976. Monensin and ruminal methane production. J. Anim. Sci., 4 3 : 3 3 6 (Abstr.). RESUME Daenicke, R., Rohr, K. et Oslage, H.J., 1982. Influence du monensin sur lea fermentations dans le rumen et les performances et la composition corporelle des taurillons. Livest. Prod. Sci., 8 : 4 7 9 - - 4 8 8 (en anglais). On a @tudi@l'influence du monensin sur les performances de croissance, la composition chimique du corps et les fermentations du rumen, sur 2 x 12 taurillons (entre 146 ~ 555 kg de poids vif) de la race Pie noire allemande. T o u s l e s animaux ont re~;u la m~me quantit@ d'aliments concentr@s (2,3--3 kg par jour) et une quantit@ d'ensilage de ma~s, au stade laiteux, @gale fi 90--95% de l'ingestion ad libitum. Lea animaux du lot experimental ont requ 30 mg de monensin par kg d'aliment (sur la base de 88% de mati~re s~che), soit une quantit@ croissant de 100 ~ 270 mg par animal par jour. Les animaux du lot t@moin n ' o n t requ aucune substance stimulant la croissance. Les r@sultats peuvent ~tre r@sum@sde la fa~on suivante: (1) Bien q u ' a y a n t consomm@ la m@me quantit@ d'aliments et de nutriments, les taurillons recevant du monensin ont eu un gain de poids vif vide de 4,8% plus @lev@que ceux du lot t@moin et, par suite, une efficacit~ alimentaire sup@rieure de 5,1%, ces diff@rences n'@tant pas significatives. (2) Le monensin n'a pas modifi@ significativement la teneur en prot@ines du corps vide mais il a augment@ significativement, de 15,3%, sa teneur en lipides. Les animaux recevant du monensin ont donc retenu 15,9% d'@nergie de plus par jour que ceux du lot t@moin. (3) Le monensin a accru la concentration en acide propionique du liquide du rumen et diminu~ celle des acides ac~tique et butyrique. On peut donc conclure que la r@tention @nerg@tique plus ~lev@e des taurillons recevant du monensin r@sulte d'une meilleure utilisation de l'@nergie. KURZFASSUNG Daenicke, R., Rohr, K. und Oslage, H.J., 1982. Der Einfluss yon Monensin auf die Pansenfermentation, Mastleistung und Sehlachtk~rperzusammensetzung bei Mastbullen. Livest. Prod. Sci., 8 : 4 7 9 - - 4 8 8 (auf englisch). In einem Versuch mit 2 × 12 Mastbullen der Rasse Deutsche Schwarzbunte (Gewichtsabschnitt 146--555 kg) wurde der Einfluss yon Monensin auf die Mastleistung, die chemische Zusammensetzung des Leerk6rpers und die Pansenfermentation untersucht. Allen Bullen wurden die gleichen Mengen an Kraftfutter (im Laufe der Mastperiode yon 2,3 auf 3 kg je Tier und Tag ansteigend) und teigreife Maissilage in einer Menge angeboten, die 90--95% ihrer ad-libitum-Aufnahme entsprach. Die Tiere der Versuchsgruppe erhielten 30 mg Monensin je kg Gesamtfutter (bezogen auf 88% TS). Die Tiere der Kontrollgruppe wurden ohne jeglichen Wachstumsf~rderer ern~ihrt. Die Ergebnisse lassen sich wie folgt zusammenfassen: (1) Bei gleicher Futter- und N~ihrstoffaufnahme waren in der Monensingruppe die Leerkbrperzunahme um 4.8% und die Futterverwertung um 5.1% besser als in der Kontrollgruppe. (2) Die Bullen der Monensingruppe wiesen im Leerk~rper einen nur geringfiigig niedrigeren Protein-, jedoch einen um 15.3% signifikant h~heren Fettgehalt auf als die

488 der Kontrollgruppe. Daraus konnte ein um 15.9% hSherer t~iglicher Energieansatz f~ir die mit Monensin gefiitterten Bullen berechnet werden. (3) Die im Laufe der Mastperiode durchgefiihrte Untersuchung des Pansensaftes der Bullen ergab in der Monensingruppe einen signifikant hSheren molaren Anteil an Propion s~iure als in der Kontrollgruppe. Entsprechend signifikant niedriger waren die molaren Anteile an Essig- und Butter~ure. Demzufolge resultierte die hShere Energieretention in der Monensingruppe aus einem hSheren Anteil an umsetzbarer Energie in der Ration.