J Sci Food Agric 1998, 76, 173È178

Eþects of Diþerent Additives on the Cell Walland Mineral Fractions of Artichoke (Cynarascolymus and Orange aurantiumL) (Citrus L)By-Product SilageM D Megi�as,1* Fuensanta Herna� ndez,1 Juan-Antonio Cano,2 AntonioMartinez-Teruel1 and Jose A Gallego11 Departamento de Produccio� n Animal, Universidad de Murcia, Campus de Espinardo, 30071 Murcia,Spain2 Departamento de Matema� tica Aplicada y Estadi� stica, Universidad de Murcia, Campus de Espinardo,30071 Murcia, Spain

(Received 20 May 1996 ; revised version received 25 March 1997 ; accepted 16 June 1997)

Abstract : The quality of the cell wall fraction content of two silage by-productswas assessed together with their di†erent mineral composition. Various treat-ments to test possible improvements in the ensilage of canning industry artichokeand orange by-products were compared with the addition of di†erent additives.Three treatments were assessed : sodium chloride (25 g kg~1), dehydrated beetpulp (62É5 g kg~1), formic acid at 4% in doses of 62É5 ml kg~1. A fourth batchacted as a control group. Samples were analysed for their nutritive character-istics. After a 100-day ensilage period the results showed that the use of theadditives in the given doses did not signiÐcantly improve the quality of the silage,although the composition of the sodium chloride batch appeared to be better.

1998 SCI.(

J Sci Food Agric 76, 173È178 (1998)

Key words : artichoke ; orange ; silage ; by-product ; additives

INTRODUCTION

Interest in conserving by-products by ensiling is steadilyincreasing, largely due to the increase in their use asanimal feed and to the rapid deterioration they undergoas a result of a low dry matter content. Orange pulpand artichoke by-products are used as a signiÐcant partof dairy animal rations during the picking season.Maymone and Dattilo (1962) carried out a test to deter-mine the apparent digestibility coefficient in citrus pulpand found it could substitute cereal grain in ruminantfeeding. In this way, Marti� nez Pascual and Ferna� ndezCarmona (1980) concluded that the incorporation ofcitrus pulp to levels of 30% in the rations of lambs

* To whom correspondence should be addressed.

did not alter daily gain, feed efficiency and dressing per-centage.

On the other hand, the considerable amount of waterin the original material is due to industrial processing ;this greatly limits the quality of the silage, which makesit necessary for both by-products to undergo previousdrying or ventilation drying treatments. Furthermore,due to the steady deterioration of artichoke by-productsilage the silo should be opened on day 50 to preventlosses in the fermentative quality (Megi� as et al 1993a).Megi� as et al (1993b) found that the fermentationprocess of orange by-product silage is stabilised moreeasily than that of artichoke.

The use of additives in ensiling is to ensure an effi-cient fermentation so that a high-quality silage can beproduced without animal health or handling related

1731998 SCI. J Sci Food Agric 0022-5142/98/$17.50. Printed in Great Britain(

174 M D Meg•�as et al

problems and without negative e†ects on rumen fer-mentation as a result of these additives. For the presentstudy we selected three di†erent materials. Formic acidprevents respiratory losses of substrate, lowers tem-perature and stops excessive protein breakdown duringthe Ðrst or second day. Dehydrated beet pulp is con-sidered a stimulant additive for silage ; when this addi-tive is used, most effluents are absorbed and sugarsolubilises in the juice to become available for fermenta-tion (Pettersson 1988). The use of sodium chloride as asilage additive has two main purposes : it aids consoli-dation of the material and protects silage from theaerobic deterioration caused on opening the silo(Wilson et al 1979).

In earlier experiments we found no signiÐcant di†er-ences in the fermentation parameters between the treat-ments with these additives for artichoke or orangeby-product silage (Megi� as et al 1991, 1992). However,limited data are available on the e†ect of these additiveson the digestibility of these materials. The aim of thisexperiment was to assess the e†ects of di†erent additiveson high-moisture by-products in order to improve thefermentative quality and the digestibility when used inruminant feeding.

EXPERIMENTAL

Materials

The study materials consisted of two di†erent by-products : orange (Citrus aurantium L, Satsuma variety),produced from the industrial process of washing andextracting segments to leave the peel as the main con-stituent ; artichoke (Cynara scolymus L) the residue fromthe industrial processing of artichoke hearts. The arti-

chokes were washed and scalded (at 90¡C for 20 min),and the hearts removed mechanically. The outer bractsand stems are the principal parts of this by-product.The material was transferred to the laboratory anddried at room temperature for 12 h to eliminate theliquids accumulated during the industrial processing.After this time both by-products were ensiled and com-pressed. The microsilos were sealed, except for anopening at the base, which was sealed after seepagerelease. One hundred days later, the silos were openedand three samples taken from the centre of each ensiledmass. The nutritive and fermentative characteristics ofboth by-products prior to ensiling are shown in Table 1.

Treatments

Both by-products were treated with three di†erent addi-tives : (1) formic acid at 4% in doses of 62É5 ml kg~1 ; (2)dehydrated beet pulp (62É5 g kg~1) ; and (3) sodiumchloride (25 g kg~1). A fourth batch was used for thecontrol treatment. Twenty-four air-tight plastic bags(three replicates per treatment) were Ðlled with by-products and placed inside a similar number of 12É50-litre polyethylene containers. These were stored at roomtemperature (21¡C).

Methods

The methods to determine the di†erent parameters wereas follows : three replicates were taken from each silocore and were frozen to [ 20¡C immediately and laterdefrosted at 4¡C for 12 h. Initial acidity was determinedby taking measurements with a pH meter from a macer-ation of the sample with distilled water. The organic

TABLE 1Nutritional and fermentative characteristics of artichoke and orange by-

product before ensiling

Artichoke Orangeby-product by-product

pH 4É10 3É34Dry matter (g kg~1) 178É9 216Constituents on g kg~1 dry matter

Crude protein 84É9 50É7NDF 499É9 128É9ADF 317É9 129É2Ash 40É3 24É9Lactic acid 26É3 23É0Acetic acid 11É3 20É0Propionic acid 1É0 0É3Isobutyric acid 0É3 0É6Butyric acid 1É3 NDa

a ND, Not detected.

E†ects of additives on artichoke and orange by-product silage 175

acids were determined by high-resolution liquid chro-matography according to the method described byMegias et al (1993b).

Dry matter determinations were made in triplicateusing approximately 300 g samples dried at 100¡C for24 h. The dried samples were milled through a 0É5 mm.Neutral detergent Ðbre (NDF), acid detergent Ðbre(ADF) and lignin permanganate, cellulose (ADF-lignin)and hemicellulose (NDF-ADF) were determinedaccording to Goering and Van Soest (1970). The grossenergy of silages was assessed with a ballistic bombcolorimeter. Tannins were determinated using themethod of Horvath (1980). Dry matter digestibility(DMD) and organic matter digestibility (OMD) werecalculated according to Vanderhaeghe and Biston(1987). The total mineral content was determined byincineration of the sample at 500¡C for 3 h in an electricmuffle furnace. The di†erent minerals (Ca, K, Mg, Fe,Cu, Zn and Mn) were determinated according to theofficial method proposed by the BOE (1989) using aPelkin-Elmer 3100 atomic absorption spectrophoto-meter.

Statistical analysis

To compare the di†erent treatments we used a varianceanalysis with the LSD (Least Square Di†erence) variant.

RESULTS AND DISCUSSION

The concentration of di†erent organic acids producedand pH values of the samples treated with additives andthe control samples are shown in Table 2 for both by-

product silages. For artichoke it can be appreciated thatthe best fermentation was obtained with the control, thepH being less than 4É2 and the lactic acid concentrationin the range 3È13%. This concentration is higher thanthe volatile fatty acid concentrations suggested byCatchpoole and Henzell (1971) for high-quality silage intemperate zones. However, the di†erences between thetreatments were not signiÐcant as revealed by varianceanalysis. In the orange fermentative study, the di†erenttreatments only showed signiÐcant di†erences in theÐnal silage pH. Those results are not in agreement withRooke (1988) whose results showed no signiÐcant di†er-ences between batches.

Table 3 summarises the results for artichoke by-product and Table 4 for orange by-product. Theseresults generally conÐrm those of our previous studies(Megi� as et al 1991, 1992). There was a signiÐcantincrease in the dry matter content of artichoke by-product when dehydrated beet pulp was added(P\ 0É05) (Table 3), but, no signiÐcant di†erences werefound between treatments for the DM content of orangeby-product on ensiling (Table 4).

ModiÐcations in DM composition in both by-products during preservation were signiÐcant for mostconstituents, particularly increases in gross energy forthe batches treated with formic acid and in structuralcarbohydrates for the batches treated with sodium chlo-ride were observed. DM losses in the way of andCO2effluents cause an increase in the silage Ðbre content.On the other hand, microorganisms, plant enzymes,acid additives or acids formed during fermentation canreduce the silage cell wall content. Jaakkola (1990)found that the formic acid in treated grass silage mainlyreduces the hemicellulose content. Adding sodium chlo-ride to the ensiled by-product reduce the hemicellulosecontent signiÐcantly, although the e†ect was more pro-nounced in the orange by-product.

TABLE 2Mean composition (g kg~1 dry matter) and variance analysis (LSD) in various treatments of artichoke and

orange by-products silagea

By-product T reatment L actic Acetic Propionic Isobutyric Butyric pHacid acid acid acid acid

Artichoke Sodium chloride 25É3a 43É6a 10É6a 10É6a 13É0a 43É1aFormic acid 23É3a 44É3a 12É6a 6É0a 16É0a 40É8aDehydrated beet pulp 19É3a 58É0a 10É6a 10É6a 14É3a 41É6aControl 28É0a 39É0a 08É0a 9É3a 9É0a 40É8aLevel of signiÐcance NS NS NS NS NS NS

Orange Sodium chloride 82É6a 118É3a 4É6a 1É3a 1É0a 24É8aFormic acid 102É3a 69É6a 4É6a 1É3a 1É3a 27É1bDehydrated beet pulp 123É0a 115É3a 5É0a 1É6a 1É3a 27É3bControl 138É0a 120É6a 5É6a 1É6a 1É3a 29É8cLevel of signiÐcance NS NS NS NS NS ***

a Means in the same column with di†erent following letters are signiÐcantly di†erent. SigniÐcance level\ (*)P\ 0É05, (**) P\ 0É01, (***) P\ 0É001, (NS) not signiÐcant.

176 M D Meg•�as et al

TABLE 3E†ect of treatments on cell wall composition of artichoke by-product after 100 days of ensilinga

Control T reatments SigniÐcancelevel

Formic Dehydrated Sodiumacid beet pulp chloride

Dry matter (g kg~1) 160É2b 163É8b 189É2a 177É6ab *Gross energy (MJ kg~1 DM) 42É0b 53É1a 51É2ab 41É7b ***Constituents (g kg~1 dry matter)

Crude Ðbre 759É5ab 821É0a 768É5ab 667É3b **NDF 767É6a 674É5ab 668É0ab 574É3b **ADF 514É1ab 533É8a 485É5ab 442É8b **Cellulose 428É6ab 450É6a 393É9ab 364É9b **Hemicellulose 186É8a 140É7ab 182É5a 133É8b **Lignin 85É4a 85É2a 89É3a 74É3a NSDMD 575É5b 459É9c 582É0b 631É6a ***OMD 583É4b 473É2c 595É0b 640É6a ***Tannins 37É7ab 41É1ab 46É3a 36É8b *Ash 41É5b 36É9b 47É8b 154É7a ***Ca 2É34a 1É42a 1É62a 1É50a NSK 2É53a 2É77a 3É08a 3É01a NSMg 0É87a 0É41b 0É46b 0É44b ***Fe (ppm) 1É92a 3É61a 4É08a 3É55a NSCu (ppm) 0É25a 0É23a 0É21a 0É17a NSZn (ppm) 2É05a 1É20b 1É41ab 0É81b *Mn (ppm) 0É24b 0É24b 0É56a 0É22b ***

a Means in the same row with di†erent following letters are signiÐcantly di†erent. SigniÐcance level\ (*)P\ 0É05, (**) P\ 0É01, (***) P\ 0É001, (NS) not signiÐcant.

With the NaCl treatment, digestibility tended to behigher for both by-products than with the other treat-ments. The signiÐcant di†erences (P\ 0É001) in DMDand OMD must be due, as reported Kung et al (1990),to the partial hydrolysis of the cell wall, which improvesdigestibility ; therefore there must be alterations in thehemicellulose/lignin ratio. The same e†ects were notedin the ADF and NDF contents for both by-products.

In our study, the nutritive value was not signiÐcantlya†ected by inhibitory components (lignins and tannins)in any of the four trials. Minerals represent anotherbarrier against the attack of rumen microorganisms onstructural carbohydrates. A number of minerals havebeen found to be associated with the plant cell wall(Spears 1994). The mineral fraction varies greatly withthe di†erent soil conditions and possible contamination.On the other hand, the nutritive value of minerals ishighly signiÐcant for animal feeding.

As far as the macrominerals of artichoke by-productare concerned, we found that the potassium level wasvery close to that required for maintenance in goats(3É1 g per day). No signiÐcant di†erences were foundbetween treatments for this mineral. For orange by-product silage, the magnesium level was higher than theamount recommended for sheep (0É69 g per day) andvery close to that recommended for goats (1 g per day).These results are conÐrmed in the artichoke by-product

silage, which presented signiÐcant di†erences(P\ 0É001). The high K and Mg levels are not signiÐ-cant because possible excesses are not retained by theanimal but mainly eliminated via the urine, as reportedKessler (1991). However, high mineral concentrationsmay cause importants metabolic disorders, which canonly be prevented by adding feedstu† with a low K andMg content to the rations of animals feed with arti-choke and orange by-product silage.

The di†erences found in Mg and Zn contents as aresult of the treatments on artichoke by-product, or inthe Cu level in the trials with orange by-product, arenot relevant. Only the level of calcium, potassium andthe trace minerals (Fe, Cu, Zn, Mn) required for rumi-nant maintenance are higher than the levels in artichokeby-product (except potassium) and orange by-product,independently of the additive used.

In conclusion, the results of this experiment give riseto interesting considerations. The results indicate thatthe additives, used in the doses reported, did notimprove the fermentation quality of artichoke or orangeby-products silages. On the other hand, althoughneither of the silages was of high-quality, the chemicaland nutritive parameters showed beneÐcial e†ects forthe sodium chloride treatment on both by-products.Special care is needed if these silages are used in smallruminants because of the excess of certain minerals ; it

E†ects of additives on artichoke and orange by-product silage 177

TABLE 4E†ect of treatments on cell wall composition of orange by-product after 100 days of ensilinga

Control T reatments SigniÐcancelevel

Formic Dehydrated Sodium levelacid beet pulp chloride

Dry matter (g kg~1) 225É6a 202É9a 212É8a 221É7a NSGross energy (MJ kg~1 DM) 40É4ab 49É6a 44É4a 34É6b ***Constituents (g kg~1 dry matter)

Crude Ðbre 308É5a 305É7a 306É3a 256É7b **NDF 272É8a 277É5a 281É5a 206É9b ***ADF 241É8a 234É4a 231É5a 200É1b **Cellulose 200É6a 194É5ab 172É0bc 157É0c **Hemicellulose 31É0a 43É1a 50É1a 6É8b ***Lignin 38É9b 38É5b 54É9a 47É6ab *DMD 794É9b 782É6b 794É8b 854É5a ***OMD 813É1b 807É4b 810É9b 865É1a ***Tannins 51É6a 46É7a 37É1a 32É6a NSAsh 51É3b 46É6b 42É2b 122É7a ***Ca 2É19a 2É45a 2É13a 1É68a NSK 1É69ab 1É31c 1É36bc 1É78a *Mg 2É43a 2É80a 2É93a 2É26a NSFe (ppm) 3É34a 1É33a 2É19a 2É25a NSCu (ppm) 1É20bc 2É16a 0É14ab 0É11c **Zn (ppm) 0É67a 0É80a 0É65a 0É62a NSMn (ppm) 0É26a 0É26a 0É32a 0É38a NS

a Means in the same row with di†erent following letters are signiÐcantly di†erent. SigniÐcance level\ (*)P\ 0É05, (**) P\ 0É01, (***) P\ 0É001, (NS) not signiÐcant.

will also be necessary to calculate the contents of othermajor minerals in these by-products. Finally, a study isin progress to determine whether the sodium chloridetreatment is more palatable for the animals so that wecan justify the extra cost.

ACKNOWLEDGEMENT

The authors are indebted to Murcia University for itsÐnancial support (Programa de Acciones Concertadas,N 96.646.9.12.1991). In addition, we wish to thank JMateo Ban8 o Pujante for his expert technical assistance.

REFERENCES

BOE 1989 OÐcial del Estado 128 16023.Boleti�nCatchpoole V R, Henzell E F 1971 Silage and silage-making

from tropical herbage species. Herb Abstr 41 (3) 213È221.Goering H K, Van Soest P J 1970. Forage Fiber Analyses

(Apparatus, Reagents, Procedure and some Applications)(USDA/ARS Agricultural Handbook no 379). USDA/ARS,Washington, DC, USA.

Horvath P J 1980 MS Thesis, Cornell University, Ithaca, NY,USA.

Jaakkola S 1990 The e†ect of cell wall degrading enzymes onthe preservation of grass and the silage intake and digest-ibility in sheep. J Agric Sci Finland 62 51È62.

Kessler J 1991 Mineral nutrition of goat. In : Goat Nutrition,ed Morand-Fehr P. Pudoc, Wageningen, The Netherlands,pp 104È119.

Kung Jr L, Carmena B R, Tung R S 1990 Microbial inocu-lation or cellulase enzyme treatment of barley and vetchsilage harvested at three maturities. J Dairy Sci 73 1304È1311.

Maymone B, Dattilo M 1962 Annalli dela SperimentazioneAgraria 15 3È30.

Marti� nez-Pascual J, Ferna� ndez Carmona J 1980 Citrus pulpin diets for fattening lambs. Anim Feed Sci T echnol 5 11È22.

Megi� as M D, Martinez-Teruel A, Gallego J A, Domenech V1991 Estudio comparativo de ensilado de subproducto dealcahofa (Cynara scolymus L .) con diferentes aditivos(Comparative study in artichoke (Cynara scolymus L .) by-product silage). Ann V et 6–7 101È105.

Megi� as M D, Gallego J A, Martinez-Teruel A, Sa� nchez M1992 Estudio comparativo de diferentes aditivos en el ensil-ado de subproducto de naranja (Comparative study withdi†erent additives in orange by-product silage). Arch Zooch41 179È182.

Megi� as M D, Martinez-Teruel A, Gallego J A, Oliver P 1993aFermentative and nutritive changes during artichoke(Cynara scolymus L .) by-product ensilage. BioresourceT echnol 43 237È239.

Megi� as M D, Martinez-Teruel A, Gallego J A, Nu� n8 ez J M1993b Chemical changes during ensiling of orange peel.Anim Feed Sci T echnol 43 269È274.

178 M D Meg•�as et al

Pettersson K 1988 Ensiling forages. Factors a†ecting silagefermentation and quality. Sveriges L antbruksuniversitet 17911È14.

Rooke J A 1988 The chemical composition and nutritive valueof grass silage of additives containing either Lactobacilusplantarumor formic acid. Grass Forage Sci 43 (1) 87È97.

Spears J W 1994 Minerals in forage. In : Forage Quality,Evaluation and Utilization, ed Fahey Jr G C, Collins M,

Mertens D R & Moser L E. ASA, CSSA and SSSA,Wisconsin, USA, pp 281È317.

Vanderhaeghe S, Biston R 1987 Estimation in vitro de ladigestibilite� des herbages. Adaptation de la me� thodepepsine-cellulase au systeme Fibertec Enzymatique. BullRech Agron Gembloux 22 (3) 209È219.

Wilson R F, Woolford M K, Cook J E, Wilkinson J M 1979 JAgric Sci Camb 92 409È415.