Protein and energy value of vinasse for pigs

Animal Feed Science and Technology, 5 (1980) 221--231

221

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

PROTEIN AND ENERGY VALUE OF VINASSE FOR PIGS

E. W E I G A N D

and M. K I R C H G E S S N E R

Institut f~r Erna"hrungsphysiologie, Techn. Universit~t M~nchen, D-8050 Freising-Weihenstephan (W. Germany) (Received 22 January 1980; accepted for publication 13 May 1980)

ABSTRACT Weigand, E. and Kirchgessner, M., 1980. Protein and energy value of vinasse for pigs. Anirn. Feed Sei. Technol., 5: 221--231. A vinasse, originating as the condensed molasses residue from the microbial production of citric acid, was chemically analyzed and given to growing pigs to determine its protein and energy value. It contained, per kg dry matter (62.6%), 185 g crude protein, 538 g N-free extracts, 48 g total sugar, 277 g ash and 12.8 MJ gross energy. Ammonia, betaine and amino acids (about half glutamic acid) accounted for 3.5, 9.1 and 28.6%, respectively, of the crude-protein N. In a 25-day balance trial with the final 10 days as collection period, ten pigs initially weighing 33 kg were pair-fed daily an average of about 1 kg of dry matter of either a basal diet (95% ground barley plus 5% cellulose) or of a mixed diet composed of, on dry basis, 77% basal diet plus 23% vinasse. Partial digestibility of components in the vinasse was: organic matter, 52%; crude protein, 45%; N-free extract, 58%; ash, 83%; and gross energy, 42%. Average dally gain and N retention were not different between dietary groups. The vinasse contained, per kg dry matter, 5.40 MJ DE and 3.61 MJ ME compared with 14.96 MJ DE and 14.48 MJ ME for the dry basal diet. The conclusion is that this vinasse, according to its low protein and energy value, can provide only a small percentage of the daily ration for pigs.

INTRODUCTION

Vinasse, or condensed molasses solubles, arise as by-products from the fermentation industry producing yeast, alcohol, citric acid, ephedrine and other substances from beet and cane molasses. In consequence of the extensive conversion and withdrawal of the sugar, the organic non-sugar compounds and the inorganic matter present in the original molasses accumulate in the condensed residue. Certainly, the addition of auxilliary chemicals and the partial removal of additional ingredients may cause further shifts in the composition and hence in the nutritive value of vinasse compared with that of the original molasses. In the work presented here, a vinasse derived from the manufacturing of citric acid was subjected to chemical analysis and was given to growing pigs in a balance trial to assess its protein and energy value for pigs.

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222 M A T E R I A L AND METHODS

Balance trial Ten castrated male pigs of the German Landrace, with an initial mean liveweight of 33 kg (SE + 2.7 kg), were housed individually in metabolism crates. They were divided into five pairs and t w o treatment groups according to parentage and liveweight. One mate of each pair (Group I) was fed on a basal diet c o m p o u n d e d of 95% ground barley and 5% cellulose powder (B 00; Rettenmaier, Holzmiihle/Ellwangen, F.R.G.). The other mates (Group II) were fed on a mixed ration of 70% basal diet plus 30% vinasse (Citragil R ; Joh. A. Benckiser GmbH, Ludwigshafen/Rhein, F.R.G.). The vinasse provided 23% of the dry matter of the mixed diet. The cellulose was to increase the capacity of the basal diet to adsorb vinasse. The daily ration offered in two equal meals per day was restricted to 1032 g dry matter for four pairs and to 860 g for one pair. There was no feed refusal at this level of intake. All animals were offered water free choice before each meal. The pigs were given the respective diets for a total period of 25 days. During the final ten days, the total faeces and 10%-aliquots of the urine were collected twice daily and stored at 4°C. Urine was collected into vessels containing 6 N H~SO4 to avoid NH3 loss. For chemical analysis, pooled samples were prepared from the 10-day collections of faeces and urine of each pig.

Analyses The proximate principles of the experimental diets, the vinasse and faeces were determined by official methods (Naumann and Bassler, 1976). Faeces were freeze,dried (30°C) before analysis, except for total dry matter and crude protein which were assayed with fresh samples at the conclusion of the balance trial. Total N of samples was determined as Kjeldahl N by a Kjel--Foss apparatus (Montag, 1974). An adiabatic b o m b calorimeter was used for gross energy analysis. The energy content of urine and vinasse was determined after freeze-drying appropriate aliquots on thin polyethylene sheets of known combustion energy. Analyses of vinasse for total sugar by the method of Luff--Schoorl, for true protein b y the method of Barnstein, and for free ammonia N by Conway's method of micro-diffusion were carried o u t as described by Naumann and Bassler {1976). Betaine was determined by the method of Ranfft and Gerstl (1975). Amino acids were analyzed after acid hydrolysis of the vinasse by methods described by Steinhart and Kirchgessner (1973). The results of the balance trial were analyzed by statistical procedures appropriate for the experimental design (Steel and Torrie, 1960).

223 RESULTS

Composition of the diets and vinasse Table I shows the proximate composition and gross energy content of the experimental diets and the vinasse giving to the pigs. The differences in composition between the diets of the t w o groups reflect the shifts ~o be expected on the basis that vinasse supplied 23% of the dry matter of the mixed ration of Group II. The dry matter of the vinasse was partitioned into three proximate nutrients, crude protein, N-free extract and crude ash, since its content of ether extract and crude fibre was negligibly small (< 2 g/kg DM). The total sugar c o n t e n t (glucose equivalents) of the vinasse was 48 g/kg DM, which accounts for a b o u t 9% of the N-free extract. Owing to the very high ash c o n t e n t of 277 g/kg of dry vinasse, the mixed diet of Group II contained a b o u t three times as much ash as the basal diet of Group I. The mineral composition of the vinasse ash has been characterized elsewhere (Weigand and Kirchgessner, 1980a). The gross energy content of the vinasse (Table I) was, on a dry matter basis, just two-thirds that of the basal diet. Based on the organic matter, however, this difference in gross energy concentration was much smaller. TABLE I P r o x i m a t e c o m p o s i t i o n and gross energy c o n t e n t of the experimental diets and the vinasse Citragil R

Group

Dry m a t t e r (DM), as fed, (g/kg)

Vinasse

I

II

Basal diet 1

Basal diet + vinaase 2

860

844

626

973 115 26 104 728 27

916 129 21 87 679 84

723 185 0 0 538 277

P r o x i m a t e nutrients (g/kg DM) Organic m a t t e r (OM) Crude protein E t h e r extract Cru de fibre N-free e x t r a c t Crude ash Gross energy (MJ/kg) In DM In OM

18.7 19.2

195% ground barley plus 5% cellulose. 277% basal diet plus 23% vinasse o n dry basis.

17.3 18.9

12.8 17.7

224 The results of Table II show that free ammonia accounted for a fairly small portion of the total Kjeldahl N of the vinasse. About 9% of the N was due to betaine (22.5 g/kg DM). The low contribution of the true protein fraction emphasizes that the vinasse contained mostly non-protein N. Nevertheless, a considerable portion of at least 28.6% of the total N was bound to amino acids. This indicates t h a t these amino acids were, for the most part, present in a free form or as peptides not precipitable by tannic acid. Glutamic acid contributed a b o u t half of the total amino-acid N (Table III) and about 15% of the total N. Aspartic acid was the second most a b u n d a n t amino acid. The remaining amino acids of Table III share approximately 40% of the total amino-acid N and 11% of the total N of the vinasse. The amino-acid hydrolysate contained more NHa-N (Table III) than was f o u n d in the fresh vinasse by the micro
Concentration (g S/kg DM)

Relative (%)

Total N1 Ammonia N2 Betaine N True protein N3 Amino acid N4

29.60 1.03 2.70 1.92 8.46

100 3.5 9.1 6.5 28.6

1Kjeldahl N. 2Free NH3-N determined by Conway's micro-diffusion method. 3N precipitable by tannic acid (Barnstein's method). 4 See Table III.

Results o f balance trial All pigs gained weight during the time of feeding with the basal and mixed diets. The average daily gain for the final ten days of the balance trial was 236 + 54 g in Group I and 236 + 41 g in Group II. Pigs o f Group II, fed on the vinasse-containing diet, consumed more water and, accordingly, excreted more urine. The pH value of fresh urine collected at the termination of the trial differed markedly ( P < 0.01) between Group I (5.6 + 0.6) and Group II (8.0 + 0.3). In both groups, faeces had a firm and normal consistence. Fresh faeces

225 TABLE III Amino-acid composition of the vinasse Amino acid

Concentration (g/kg DM)

Alanine Arginine Aspartic acid Cysteine Glutamic acid Glycine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tyrosine Valine

3.20 0.80 6.69 0.45 47.17 2.67 0.43 0.99 1.71 0.51 0.97 2.35 1.44 2.78 2.18 1.55 2.03

Sum Ammonia1

77.92 5,52

% of total amino-acid N 6.0 3.0 8.3 0.6 53.1 5.9 1.4 1.2 2.1 1.2 1.1 2.4 2.1 4.4 2.9 1.4 2.9 100 --

i Present in the amino-acid hydrolysate.

averaged 34.6 + 1.6% DM in Group I versus 30.4 + 1.3% DM in Group II (P < 0.01). Health problems were not encountered with any of the animals. Apparent digestibility coefficients of the proximate nutrients and gross energy in the diets and in the vinasse are summarized in Table iV. In the mixed diet of Group II, dry matter, organic matter, crude protein, N-free extract and gross energy were markedly less digestible than in the basal diet of Group I. Accordingly, partial digestibility coefficients derived for these components of vinasse are very much lower than the corresponding values for the basal diet. Vinasse did n o t significantly affect digestibility of the ether extract or crude fibre of the basal diet. In contrast to the organic constituents, the ash component of the diet of Group II, and accordingly of the vinasse, had a much higher digestibility than that of the basal diet. Table V presents the mean daily amounts of N and energy intake, excretion, digestion and retention during the 10-day balance period. Since DM consumption was the same in the two treatment groups, the differences in N and energy intakes were directly proportional to their respective concentrations in the two diets (Table I). The two groups of pigs differed significantly in faecal N excretion, b u t were comparable with regard to urinary N loss and actual amounts of N digested and retained. Daily N retention per kg liveweight gain

226 T A B L E IV A p p a r e n t digestibility (%) o f p r o x i m a t e nutrients and gross energy o f the t w o experimental diets and the v i n a u e during the final 10 days of the balance trial with growing pigs Group

Dry m a t t e r Organic m a t t e r Crude protein Ether extract Crude fibre N-free extract Crude ash Gross energy

I

II

Basal diet

Basal diet + v i n a ~ e

80 82 78 67 30 90 31 80

76 76 67 72 28 84 70 74

S.E. and significance of difference ~

Vinasse=

1.6"* 1.6"* 3.3** 5.0 NS 4.5 NS 1.0"* 3.7** 0.8**

60 + 6.4 52 + 5.4 45 ± 6.7 0 0 58 ± 4.6 83 -+ 2.4 42 ± 3.8

1 Probability level: NS, non-significant (P > 0.05); **, P < 0.01. 2 Mean (+ S.E.) partial digestibility calculated f r o m the observed values of the five pairs o f pigs. TABLE V Nitrogen and energy r e t e n t i o n by the pigs o f G r o u p I (basal diet) and G r o u p II (basal diet + vinasse) during the final 10 days of the balance e x p e r i m e n t Nitrogen (g/day)

Intake Excretion in faeces in urine Digested Retained = Metabolizable 2

Group I

Group II

S.E. and significance o f difference I

Energy ( M J / d a y ) Group I

G r o u p II

S.E. and significance o f difference

18.36

20.55

0.14"*

18.65

17.27

0.13"*

4.04 9.44 14.32 4.88 --

6.70 8.83 13.85 5.02 --

0.64** 0.63 NS 0.65 NS 0.78 NS --

3.67 0.53 14.98 -14.45

4.52 0.82 12.75 -11.93

0.39** 0.10"* 0.43** -0.46**

1 See f o o t n o t e 1 to Table IV. 2 Intake minus a m o u n t e x c r e t e d in faeces and urine.

was also closely comparable and averaged 21.6 + 5.5 g for Group I and 21.5 + 1.7 g for Group II. With regard to energy, both the faecal and urinary energy losses were higher in Group II than in Group I (Table V). Since methane loss can be regarded as negligibly small in pigs (Nehring, 1972), the values for energy retention reflect the supply of metabolizable energy, which was a b o u t 17% lower for the pigs of Group II compared with that for Group I.

227

Table VI shows the energy value of the vinasse in comparison with that of the basal diet. Digestible energy and total digestible nutrients were derived from the composition data of Table I and the digestibility data of Table IV. The metabolizable energy concentrations were c o m p u t e d from the results of Table V. For the vinasse, metabolizable energy amounted to only 67% of the digestible energy, a value which is substantially lower than the corresponding percentage of 96 for the basal diet. T A B L E VI

Energy value of the basal diet (95% barley + 5 % cellulose) and the vinasse CitragilR as determined in the balance trialwith growing pigs In the dry m a t t e r

In the organic m a t t e r

Basal diet

Basal diet

Vinasse

Vinasse

Digestible energy (MJ/kg)

14.96

5.38

15.38

7.43

Metabolizable energy (MJ/kg)

14.48

3.61

14.88

5.00

Total digestible nutrients (TDN/kg) 1

817

395

840

546

1TDN -- (dig. crude protein + 2.3 x dig. ether e x t r a c t + dig. crude fibre + dig. N-free extract) (g/kg).

DISCUSSION

A fairly high crude protein content is a general compositional characteristic of vinasse, mainly because the extensive withdrawal of the sugar from molasses entails an increased concentration of its other dry matter constituents remaining in the condensed residue. The crude protein concentration of the vinasse used in the present work was, however, relatively moderate and lower than that found in a previous study (Weigand and Kirchgessner, 1975) for a vinasse batch that also originated from the microbial production of citric acid. A reasonable explanation for this difference in composition might be that the vinasse of the present study came from a batch in which a major portion of the substrate was cane molasses, which contains less crude protein than beet molasses (DLG, 1970; Nehring, 1970). The assumption that the present vinasse was from a production in which both cane and beet molasses were used is supported b y the finding that betaine had a share of only a b o u t 9% of the total N (Table II). In beet molasses, betaine generally acccounts for at least 20--30% of the total N (Davies and Dowden, 1936; Stark et al., 1959; Schiweck and

228 Haberl, 1973). In a previously analyzed vinasse, even as much as 40% of the N was b o u n d to this quarternary ammonium base (Weigand and Kirchgessner, 1975). Amino acids, betaine and ammonia shared together over 40% of the crudeprotein N of the vinasse (Table II). This percentage agrees rather'closely with the observed partial digestibility of 45% for the vinasse crude protein (Table IV), presumably because these N components comprised the major portion of the digestible crude protein. For glutamic acid and betaine, which alone accounted for nearly one quarter of the total N of the vinasse studied here, apparent digestibility coefficients of 97 and 99%, respectively, were observed with pigs (Weigand and Kirchgessner, 1980b). The indigestible N fraction of vinasse could perhaps primarily be due to melanoid compounds. Fujimaki et al. (1979) found that rats consuming melanoidin prepared from glycine and glucose excreted a b o u t three quarters of this c o m p o u n d in their faeces. The relatively low crude protein digestibility of 45% for the vinasse of the present study (Table IV) confirms previous findings with pigs. Boeve et al. (1973) reported digestibility values of around 40% for the crude protein of cane molasses and cane vinasse, b u t much higher percentages for a beet vinasse. These authors, however, ultimately set the contents of digestible crude protein for the cane and beet vinasses equal to the analytically determined contents of amino acids, which accounted for about 30 and 40%, respectively, of the total crude-protein N. To what extent betaine might positively contribute to the protein metabolism of pigs, perhaps by sparing methionine as a source of labile methyl groups, is n o t evident from reports in the literature. When, accordingly, the N bound to betaine and also that b o u n d to ammonia (Table II) is subtracted from the digestible crude protein fraction of the vinasse used in the present investigation, some 60 g of digestible crude protein per kg DM remain; that is 32% of the total crude protein. Agaim this percentage closely agrees with the fraction of the amino-acid b o u n d N of the vinasse (Table II), especially in view of the fact that certain amino acids are partially or totally destroyed during analysis. It may be concluded that only a b o u t one-third of the crude protein of vinasse is of nutritional value to pigs because of its moderate digestibility and its unbalanced composition. The finding that the pigs of Group II did not excrete more N in the urine than those of Group I (Table V) is evidence that the absorbed N of vinasse was as well retained as that from the barley of the basal diet. The vinasse had a relatively low concentration of metabolizable energy (ME) of 3.61 MJ/kg dry matter. According to feed tables for pigs (Nehring, 1970; National Research Council, 1973), beet and cane molasses contain approximately four times as much ME on a dry matter basis. This difference can only partly be explained by the rather high ash content of the vinasse. Based on organic matter, the gross energy concentration of the vinasse (Table I) closely agrees with that of molasses (17.7 MJ/kg cane molasses; Nehring, 1970). This is, however, n o t the case for DE (digestible energy) or ME. The major reason for the low ME value of vinasse is certainly the limited digestibility of

229 its organic matter and energy (Table IV). Boeve et al. (1973) reported a similarly low digestibility for the organic matter of cane vinasse in a digestion trial with pigs. A further factor also to contribute to the moderate ME value of the vinasse used in the present study was the metabolizability of the DE, observed to average just 67%. By contrast, there was only a small difference between the ME and DE of the basal diet (Table VI). Reported ME values of molasses for pigs also differ at most a b o u t 5% from DE levels (Nehring, 1970; National Research Council, 1973). The lower metabolizability of the DE of the vinasse resulted from the substantially higher urinary energy loss of the pigs in Group II compared with those of Group I (Table V). Since there was no equivalent difference in urinary N excretion, it may be assumed that the higher urinary energy loss of the vinasse-fed pigs was predominantly due to the renal clearance of organic c o m p o u n d s free of, or low in, nitrogen. The results for the concentration of DE, ME and total digestible nutrients in the basal diet (Table VI) are n o t different from reported energy values of barley for pigs (DLG, 1970; Nehring, 1970; National Research Council, 1973). Hence the cellulose powder, comprising a b o u t 5% of the basal diet, did not significantly lower the energy concentration of the basal diet compared with its major constituent, barley. This is not unexpected, since pure cellulose is highly digestible for pigs (Kirchgessner et al., 1975). With the basal diet reflecting the energy value of barley, the data of Table VI indicate that the organic matter of the vinasse contained only about half as much DE and one third as much ME as the organic matter of barley. On the basis that the vinasse used in the present investigation contained 48 g total sugar per kg dry matter (equivalent to 45.6 g saccharose) and that saccharose supplies 16.4 kJ ME to pigs {Nehring, 1970), the sugar-free organic matter of vinasse would contain about 4.5 kJ ME/g. Since this sugar-free organic matter essentially originates from its parent substrate, molasses, it must be expected that the ME value of both vinasse and molasses will greatly vary with their sugar content. The results of the present study allow the conclusion that vinasse may be used as a feed ingredient for pigs. According to its relatively low energy value it may, however, compose just a minor portion of the daily ration, even though the pigs of the present study consumed as much as 237 g/day of dry matter of vinasse, without obvious ill effects, throughout the experiment. Results of a practical feeding trial with market pigs (Kirchgessner and Weigand~ 1980a) showed that vinasse may advantageously supply as much as 2.5% (on dry basis) of the complete feed for the growing period and twice this percentage during the finishing period. In this study, in which the pigs were fed individually according to a restricted feeding scheme and the experimental groups were allowed to consume wheat bran and vinasse in addition to the basal ration consumed by the control groups, growth performance indicated a definite nutritional value for vinasse similar to that of wheat bran. This finding confirms, under practical feeding conditions, the energy value observed in the present study with pigs. Vinasse also showed a nutritive value a b o u t

230

comparable with that of wheat bran in a feeding trial with broiler chicks (Kirchgessner and Weigand, 1980b). The rather high ash content of vinasse (Table I) m a y seem to be more a disadvantage than an advantage to its use in animal feeding, especially since it involves a diminution of the crude protein and energy concentration and m a y increase the potassium load. However, mineral balances established in growing pigs clearly showed that vinasse can substantially contribute to the supply of Ca, M g and Na, and drastically improve the mineral and acid--base balance of animals that otherwise do not receive an adequate supply of these minerals (Weigand and Kirchgessner, 1980a). Apart from the nutritional value, the technological properties of vinasse m a y be important in considering its profitable use as a feed ingredient, especially by the feed industry. Observations m a d e in connection with the present and other studies (Kirchgessner and Weigand, 1980a, b) indicated that vinasse, even w h e n present at a low percentage in diets, was a powerful agent to bind feed particles and remove the inherent dustiness of fine components. Accordingly, vinasse should be qualified, similarly to molasses, to serve as a pelleting aid and binding agent in the production of mixed feeds and mineral mixtures.

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231 Schiweck, H. and Haberl, L., 1973. Einfluss der Zusammensetzung der R~benmelasse auf die Hefeausbeute. Zucker, 26: 347--355. Stark, J.B., Goodban, A.E. and McCready, R.M., 1959. Fractionation of nitrogen compounds in beet molasses. J. Amer. Soc. Sugar Beet Technol., 10: 571--577. Steel, R.G.D. and Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York. Steinhart, H. and Kirchgessner, M., 1973. Peptidverteilung auf MolekulargewichtsblScke bei der In-vitro-Verdauung yon Sojaprotein mit Pepsin unter dem Einfluss verschiedener Verdauungszeiten. Z. Tierphysiol., Tierern~hrg. u. Futtermittelkde., 32: 55--64. Weigand, E. and Kirchgessner, M., 1975. Futterwert der Vinasse Citragil und ihr Einsatz in der Wiederk~u erf~ tteru ng. Wirtschaftseigene Futter, 21 : 191--197. Weigand, E. and Kirchgessner, M., 1980a. Mineralstoffbilanzen yon wachsenden Schweinen bei einer Vinassezulage. Z. Tierphysiol., Tierern~/hr. u. Futtermittelkde., 43: 121--129. Weigand, E. and Kirchgessner, M., 1980b. Betain- und Glutamins~iureanteile an der Stickstoffverdauung und -bilanz bei Vinassefiitterung an wachsende Schweine. Arch. Tierern~'hrg., in press.