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The apparent digestibility of Atriplex barclayana and its effect onnitrogen balance in sheep

R. W. Benjamin, E. Oren, E. Katz and K. Becker

Animal Production / Volume 54 / Issue 02 / April 1992, pp 259 - 264DOI: 10.1017/S0003356100036886, Published online: 02 September 2010

Link to this article: http://journals.cambridge.org/abstract_S0003356100036886

How to cite this article:R. W. Benjamin, E. Oren, E. Katz and K. Becker (1992). The apparent digestibility of Atriplex barclayana andits effect on nitrogen balance in sheep. Animal Production, 54, pp 259-264 doi:10.1017/S0003356100036886

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Anim. Prod. 1992, 54: 259-264 0003-3561/92/07830259$02-00© 1992 British Society of Animal Production

The apparent digestibility of Atriplex barclayana and its effect onnitrogen balance in sheep

R. W. Benjamin1, E. Oren1, E. Katz2 and K. Becker3

department of Natural Resources, Agricultural Research Organization, Bet Dagan 50250, Israelinstitutes for Applied Research, Ben-Gurion University of the Negev, Beer Sheva 84110, Israelinstitute for Animal Production in the Tropics and Subtropics, University of Hohenheim, 7000 Stuttgart 70, Germany

Abstract

An in vivo digestibility trial was conducted by feeding sheep the leaves, fruits and twigs of Atriplex barclayana in aproportion roughly equivalent to that eaten by sheep grazing freely in Atriplex plantations. Four treatments were imposedon each of four sheep in a 4 X 4 Latin-square experimental design: Atriplex offered alone or with 100, 200 or 300 g/daytapioca meal.

The mean apparent digestibility of the Atriplex dry matter (DM) and organic matter (OM) consumed were 0-59 and 0-56,respectively. Addition of tapioca to the Atriplex in the diet did not improve these digestibility coefficients. The low OMcontent of 760 g/kg together with its digestibility of 0-56 resulted in the Atriplex having a low metabolizable energyconcentration of 6-28 MJ per kg DM. The in vitro apparent DM digestibility of Atriplex was approximately 0-09 higherthan the in vivo apparent digestibility.

The mean nitrogen concentration of the Atriplex DM was 16-6 g/kg, and its apparent digestibility 0-73, which was notimproved by the addition of tapioca to the diet. Nitrogen retention of the sheep eating only Atriplex was proportionately0-17 of the nitrogen intake. The addition of 300 g tapioca improved nitrogen retention to 0-27 but was not significantlydifferent from the other treatments.

Water intake and urine excreted were as high as 14 and 12 I/day respectively, for an Atriplex DM intake of about1300 g/day. During the experiment the sheep only maintained live weight, despite daily intakes of up to 1200 g AtriplexDM and up to 300 g tapioca.

Keywords: Atriplex, digestibility, nitrogen balance, sheep.

Introduction misleading because the ash content may include aAtriplex barclayana is a perennial halophyte shrub, high proportion of soluble salts of no energy value tonative to southern California, grown in Israel under animals. It is a problem to estimate the apparent DMpartial sea water irrigation for its high salt tolerance digestibility by in vitro methods, because of theand its ability to withstand repeated cutting. Like difficulty in simulating the animal's absorption-most halophytes, the ash content of its dry matter rejection mechanism for soluble salts in the(DM) is high relative to that of non-halophytic alimentary tract. This is particularly so for such anspecies. Depending on the growing conditions, the unconventional fodder plant as a halophytic shrub,ash content can be as low as 200 g/kg for shrubs with its high ash content,irrigated with sweet water and as high as 300 to 400under saline conditions (Pasternak, Nerd, Aronson, The situation is further complicated by the fact thatKlotz, Yagil and Venkert, 1986). Because of its high grazing animals consume twigs as well as leaves, inash content, the gross energy content of its DM is low an unknown proportion, but the apparentrelative to that of herbaceous species. In general, the digestibilities are usually estimated only for leavesapparent digestibility of Atriplex species has been (Wilson, 1977). Thus, the digestibility of the biomassexpressed in the literature on a DM basis, whether actually consumed by grazing animals is rarely givencalculated by in vivo or in vitro methods. This can be in the literature.

259

260 Benjamin, Oren, Katz and Becker

The high crude protein (CP) content of Atriplexleaves of up to 200 g/kg DM (Wilson, 1966) can alsobe misleading, because proportionately up to 0-60 ofthis chemical fraction may be non-protein nitrogen(Yaron, La vie, Forti and Benjamin, 1985), which isnot necessarily utilized by ruminants as a nitrogensource unless readily available energy material ispresent in the rumen during fermentation anddigestion. Hassan and Abdel-Aziz (1979) found thatsheep eating Atriplex nummularia leaves had anegative nitrogen balance, which became positivewhen their diets were supplemented with barleygrain.

Because of the high ash (salt) content of Atriplexleaves, animals eating it must have a relatively highwater intake in order to excrete the ingested salt.Where drinking water is freely available this may beof no concern, but where the supply is limited, as isoften the case in Africa, it may be a serious limitationto the use of Atriplex as an animal food.

This report describes an experiment conducted withsheep: (a) to determine the apparent digestibility ofA. barclayana leaves and twigs offered in a proportionsimilar to that eaten by sheep grazing freely onAtriplex shrubs; (b) to estimate the nitrogen balanceof sheep eating A. barclayana; (c) to estimate the waterintake per kg DM consumed; and (d) to study theeffect on the nitrogen retention of sheep eating A.barclayana by adding tapioca to the Atriplex ration, asupplement with a high metabolizable energy and alow crude protein concentration.

Material and methodsFoodsA. barclayana shrub foliage was harvested in June andJuly 1986 from an irrigated (fresh water) and NPK-fertilized plantation, planted in 1985 near Ashkelon,Israel. It was harvested by cutting with a mower andthe harvest was left to dry outdoors on polyethylenesheets. The concentration of twigs in the materialharvested was 400 g/kg on a dry weight basis.Proportionately this was approximately 010 higherthan that estimated to be consumed in an Atriplexplantation in a concurrent sheep grazing experiment.The air-dry material was gathered and groundcoarsely in a chopping machine and then mixedthoroughly to ensure uniformity for subsequentfeeding. Tapioca meal was obtained, commercially,in pellet form.

SheepFour 6-month-old, crossbred male lambs, eachweighing about 40 kg, which had previously grazedin an Atriplex shrub field and which had beensupplemented with a concentrate, were used in the

experiment. They were each held individually inmetabolic cages designed for digestibility trials.

Experimental designFour treatments were imposed on each of four sheep:Atriplex offered alone and together with 100, 200 or300 g tapioca meal per day in a 4 X 4 Latin-squareexperimental design, 9 days for each period. Beforeeach period, Atriplex was offered ad libitum to eachsheep in each treatment during a 10-day adjustmentinterval by offering 500 g Atriplex alone, or togetherwith 33, 66 or 100 g tapioca, every 4 h during 12 h ofdaylight. During each of the 9-day experimentalperiods and for all treatments, Atriplex was offeredat a rate that was proportionately 010 higher thanthat consumed during the adjustment period in thetreatment receiving 300 g tapioca.

Data were analysed by least-squares analysis ofvariance. Treatment, sheep and period were includedin the model (Statistical Analysis Systems Institute,1985). When differences were detected, means werecompared using Duncan's multiple range test(Duncan, 1955).

Feeding and samplingOne-third of the daily Atriplex and tapioca rationwas given to the sheep every 4 h during the daytime,beginning at 07.00 h. At 07.00 h every day theremaining food was collected and weighed, as werethe faeces. Samples of the Atriplex offered weretaken each day and pooled every 3 days, to givethree samples for each 9-day period. Atriplexremains were also pooled every 3 days and mixedthoroughly to give three 500-g samples. A similarprocedure was used for the faeces. Four tapiocasamples were taken, one for each 9-day period. Eachday at 07.00 h, urine excreted into acidifiedcontainers during the previous 24 h was collected,measured and stored. A pooled sample of 500 cm3

was taken every 3 days. All samples were stored in adeep freezer unit for future DM, ash and nitrogenanalyses.

Weighed water was made available in buckets to thesheep each day at 07.00 h and reweighed thefollowing day at the same hour.

Laboratory analysesDM concentration was determined by dryingduplicate samples to 70°C for 72 h in a forced-draught oven. Ash content was determined byashing DM samples at 500°C in an ashing furnace for4h.

Total nitrogen content of samples was determined bythe Kjeldahl procedure (Association of OfficialAnalytical Chemists, 1975). Protein nitrogen was

Atriplex for sheep 261

Table 1 Concentration (g/kg) of dry matter, ash and nitrogen in thefoods supplied, the Atriplex remains, the faeces and the urine in alltreatments and periods

Dry matterAsh

(in DM)Nitrogen(in DM)

Atriplex fedTapioca fedAtriplexremains

FaecesUrine

Mean

890920

840310

s.e.

73

108

Mean

23060

34017022

s.e.

41

2031-3+

Mean

1664

16121-7

s.e.

60-1

0-920-2+

t Calculated in the urine weight.

determined by removal of soluble non-proteinnitrogen in trichloride acetic acid before the Rjeldahlprocedure. Non-protein nitrogen was calculated bysubtracting protein nitrogen from total nitrogen.

In vitro apparent DM digestibilities of Atriplex andtapioca were determined using the artificial rumenmethod of Tilley and Terry (1963). Duplicate sampleswere incubated for 72 h.

The mean concentration of non-protein nitrogen inthe CP nitrogen fraction of Atriplex offered, Atriplexrefusals and faeces was 470, 430 and 230 g/kg,respectively.

The mean DM intakes of Atriplex, tapioca and waterand the mean amounts of faeces and urine excretedby the sheep in each treatment are presented in Table2.

The ash (salt) balance of the sheep in each treatmentis presented in Table 3. There was considerablevariation in ash retention between periods in alltreatments, being positive in the first three periodsbut negative in the fourth so that differences betweentreatments were not significant. However, the resultscannot be considered precise because of thedifficulties in collecting clean urine samples. Urinewas sampled (in some cases) after passing overfaeces, so that unknown amounts of dust and ash ofuncertain origin were also collected with the urine.Some ash (salts) may also have been lost during thedrying and ashing procedure when preparingsamples for analysis.

The mean nitrogen balance of the sheep in eachtreatment is also given in Table 3; differencesbetween treatments were not significant.

ResultsThe mean DM, ash and nitrogen concentrations inthe Atriplex and the tapioca offered, the Atriplex

Table 3 Ash and nitrogen balance of sheep in each treatment

Tapioca treatment (g/day)

remains (uneaten), the faeces and the urine of thesheep in each treatment are given in Table 1. Theresults are the means of 12 samples, each obtainedfrom the pooling of 3-day collections.

Table 2 Mean dry matter intake (DMI), water intake, faeces andurine excreted and the ratio of water intake per kg DM intake in eachtreatment

Tapioca treatment (g/day)

0 100 200 300 s.e.

DMIAtriplex (g/day) 1024 1076 1067 1111 104Tapioca intake(g/day) 0 92 184 277

Water intake(kg/day) 10-16 10-67 11-33 11-54 1-45(kg/kg DMI) 9-8 9-0 9-1 8-3 0-8

Faeces output (g DMper day) 418 510 494 499 74

Urine output(kg/day) 6-99 5-53 7-05 7-30 1-1

Ash balanceAsh intake

(g per period)Ash in faeces

(g per period)Ash in urine

(g per period)Ash retentiong per periodg per dayas fraction

of intakeNitrogen balanceNitrogen intake

(g per period)Nitrogen in faeces

(g per period)Nitrogen in urine

(g per period)Nitrogen retentiong per periodg per dayas fractionof intake

nU

2067

632

1218

21724

0-09

150-5

41-3

82-2

27-03-0

0-17

1 f\f\1UU

2238

686

1340

21224

0 1

160-6

47-9

84-8

27-93-1

0-18

zUU

2281

757

1443

819

0-04

164-4

51-1

87-0

26-32-9

0-16

J00

2378

773

1463

14216

0-06

169-7

52-7

70-0

47-05-2

0-27

s.e.

213

72

128

8911

0-5

12-5

4-6

9-6

9-81-1

0-06

262 Benjamin, Oren, Katz and Becker

Table4 Effects of treatment on apparent digestibility of componentsin ration and on calculated apparent digestibility of components inAtriplex

Ration digestibilityDry matterOrganic matterAshNitrogen

Tapioca treatment (g/day)

0

0-593c

0-563d

0-703a

0-728a

Calculated digestibilityof Atriplext

Dry matterOrganic matterAshNitrogen

0-5930-5630-703a

0-728a

100

0-608bc

0-583c

0-695a

0-703b

0-5850-5500-695a

0-702ab

200

0-623ab

0-608b

0-670b •0-695b

0-5800-5550-658c

0-697ab

300

0-643a

0-633a

0-673b

0-689b

0-5880-5600-673b

0-670b

s.e.

0-0150-0130-0090-025

0-0150-0130-0070-023

a,b,c,d Within rows, means with a common superscript do notdiffer significantly (P < 0-05).t Assuming 0-88 for apparent digestibility of tapioca.

The mean apparent digestibility coefficientsestimated for DM, organic matter (OM), ash andnitrogen in the treatment diets are listed in Table 4together with the mean apparent digestibilitycoefficients of the corresponding Atriplexcomponents consumed in each treatment, calculatedby assuming an apparent digestibility coefficient of0-88 for tapioca (from the in vitro analysis).

The in vivo apparent digestibilities calculated forAtriplex alone, and for Atriplex with 100, 200 or300 g tapioca, were 0-593, 0-608, 0-623 and 0-643,respectively. The corresponding in vitro values were0-678, 0-693, 0-714 and 0-726, respectively. For the invitro analysis samples were prepared by mixing theAtriplex with the tapioca in the same proportions asthey were consumed in the in vivo digestibility trial.

DiscussionChemical componentsThe ash concentration in the Atriplex DM offeredwas 230 g/kg, which is relatively high consideringthat the shrubs were irrigated with fresh water. Theleaf : stem ratio was 6 : 4, which is high and is due tothe young age (6 month) of the shrubs. However, asthe ash concentration in the leaves is higher than thatin the stems, the high leaf content could explain thisrelatively high ash content. The ash concentration inthe Atriplex refusals was always up toproportionately 014 higher than that in the Atriplexoffered. This was a result of leaves being the

principal component of the Atriplex not eaten by thesheep in all treatments and because of salt falling offthe dry leaves. The ash concentration in the faeces inthe treatments was relatively constant at 160 to191 g/kg DM. In the urine, the mean ashconcentration in the treatments varied from 21 to23 g/kg of the undried weight.

The nitrogen concentration in the Atriplex DMoffered was 18-5 g/kg in periods 1 and 2 but only14-4 and 15-1 in periods 3 and 4, respectively. Thesenitrogen concentrations correspond to CPconcentrations of 116, 90 and 94 g/kg, respectively,which is considerably lower than the 140 found byPasternak et al. (1986) for Atriplex irrigated with seawater. There is a trend for the CP concentration toincrease with an increasing ash concentration(Pasternak et ah, 1986) due to the shrubs increasingtheir soluble non-protein compounds content inorder to be able to exclude salt from circulating in theshrub (by storing salt in special cells under thecuticle) but at the same time maintaining theirosmotic pressure higher than that of the soil water.Nevertheless, the nitrogen concentration must beconsidered relatively high considering thatproportionately 0-40 of the Atriplex on offer to thesheep was stem material. It is not clear why thenitrogen concentration was lower during periods 3and 4, but may have been because the Atriplexoffered during periods 1 and 2 was cut 1 monthearlier than that of periods 3 and 4. However, thedrying conditions and other food preparations wereidentical.

The mean nitrogen concentration of the faecesbetween treatments showed little variation (11-1 to12-4 g/kg), whereas that in the urine varied from1-36 to 2-33. The higher variation in the urine wasdue to the high variation in total urine excreted,which was related to the variation in water intake.

'Non-protein nitrogen concentration in the CP of AtriplexThe value of 470 g/kg for the material on offer ismuch higher than that found in conventional foodsbut lower than the 600 found previously forA. nummularia (Yaron et al., 1985). The type of non-protein nitrogen in the Atriplex was not examined inthis experiment. However, Storey and Wyn Jones(1977) found significant quantities of quaternaryammonium compounds in salt resistant plants(including Atriplex spongiosa) which were identifiedas choline, trigonelline, proline and betaine; andincreased amounts of betaine were associated withincreased salt tolerance and drought resistance.

Intake of Atriplex and waterIn all tapioca treatments there were no tapiocarefusals. Differences between the mean intakes of

Atriplex for sheep 263

Atriplex for each treatment were small, even thoughwithin treatments and between periods there wasmore variation, due mainly to differences betweenindividual sheep. One of the sheep consistentlyconsumed less Atriplex than the others. Waterintakes were high, but tended to be lower as tapiocaintakes increased. The ratio of water drunk (kg/kgDM consumed) was lowest for the 300 g tapiocatreatment (8-3 :1) and highest for the Atriplex alonetreatment (9-8 : 1). Even considering the relativelyhigh daytime ambient temperatures of 24° to 30°C,these ratios are very high. With conventional food,the ratios at these temperatures rarely exceed 4:1(Chen, 1975). Observations showed that the sheeptended to alternate between eating and drinking.

Faeces and urine excretedMean faeces excreted in the Atriplex-alone treatment(lowest total DM intake) was proportionately 0-20less than in the other treatments, which were similar.On the other hand, the mean urine excreted in the100 g tapioca treatment was 0-25 less than in theother treatments. Even when the fractions of urine towater drunk are compared, the 100 g treatment wasonly 0-52 v. about 0-63 for the other treatments. Thereason for this difference appears to be the lower ashintake (Table 3).

Ash balanceThe mean ash intake over 9 days was about 2200 g inall treatments. These intakes, even on a daily basis(244 g), are high and explain the high water intakesand high amounts of urine excreted. In alltreatments, the ash in the faeces was proportionatelyabout 0-35 of the total ash excreted. This indicatesthat either there was some physiological mechanismoperating which limited the absorption of salts intothe blood, or that about 0-35 of the ash intake was inan insoluble form. The ash retention, in the first threeperiods, was positive at proportionately 0-04 to 0-1 ofthe ash intake but was unaccountably negative in thefourth. However, the accuracy of the determinationof the ash proportion of the urine is questionable,being subject to sampling errors. In addition, at least21 water with an unknown salt proportion were lostby respiration.

With the above reservations, from 30 to 50 kg urinewere excreted for each kg salts in the urine. On adaily basis, 100 to 155 g salt were absorbed into theblood and excreted through the urine. Even thoughthis is a heavy load on the kidneys, no ill effects onthe sheep were observed during the experiment butit could indicate a significantly heavier than normalenergy expenditure for urine excretion (Arieli, Nairn,Benjamin and Pasternak, 1989). The lack of anyobservable ill effects also indicates that it is unlikelythat there was any significant ash retention.

Nitrogen balanceThe nitrogen intake from the Atriplex was ca.18 g/day, or about 112 g CP. Of the nitrogenexcreted, about 0-65 was in the urine in alltreatments. Urine-nitrogen was proportionately 0-44,0-45, 0-54 and 0-46 of the total nitrogen intake in the0,100, 200 and 300 g tapioca treatments, respectively.That is, even though only up to 0-35 of the nitrogenwas excreted in the faeces, only 0-16 to 0-27 wasretained. Thus, nitrogen retention per day variedwith treatment from 3 to 5-4 g, which is equivalent to19 to 34 g CP per day, barely enough formaintenance requirements (Agricultural ResearchCouncil, 1980).

Digestibility coefficientsDifferences between component mean digestibilitiesbetween treatments were significant. The higher thetapioca intake, the higher the DM and OMdigestibility. However, for ash and nitrogen thesituation was the opposite, but differences were inmost cases small. Statistical analysis shows thatdifferences caused by sheep and period were in mostcases not significant, the nitrogen differences forperiod being the most important exception. This wasprobably due to the different nitrogen concentrationsof the Atriplex of 18-5,14-4 and 14-6 g/kg for periods1 and 2 and periods 3 and 4, respectively. The lowerthe nitrogen concentration, the higher thedigestibility.

The mean apparent digestibility of 0-59 for AtriplexDM was lower than the 0-69 and 0-62 forA. nummularia leaves found by Wilson (1977) andHassan, Abdel-Aziz and El-Tabbakh (1979),respectively, but higher than the 0-42 and 0-54 foundfor A. nummularia leaves and twigs by Contreras(1977) and Benjamin, Barkai, Hefetz, Lavie andYaron (1986), respectively. The mean apparentdigestibility of 0-70 for CP was lower than the 0-84,0-82 and 0-79 found by Newman (1969), Wilson(1977) and Hassan et al. (1979), respectively, forA. nummularia leaves.

Calculated digestibilities of Atriplex components in therations givenThese coefficients were calculated by assuming thatthe tapioca digestibility was 0-88 for all chemicalcomponents. This assumption was based on the DMdigestibility in the in vitro analysis. Differencesbetween treatment means were significant for ashand nitrogen and not significant for DM or OM.Differences caused by period were significant for ashand nitrogen. Differences caused by sheep were alsosignificant for ash and nitrogen.

Nitrogen retentionDifferences between means were not significant fornitrogen retention between treatments or between

264 Benjamin, Oren, Katz and Becker

sheep, but were so for period. Nitrogen retentionduring period 4 was significantly less than thatduring the other periods. This was apparently due tothe lower nitrogen proportion of the Atriplex duringthis period, as compared with periods 1 and 2.

In vitro and in vivo apparent DM digestibilitycoefficientsIn general, in vitro estimates were about 0-08 to 0-10higher than the in vivo estimates. The regression of invivo on in vitro digestibility was y = 0-116 + 0-712x, r2

= 0-68 (P < 0-01).

Live weights of the sheep during the experimentDuring the digestibility trial there were no significantlive-weight increases, although one of the sheepgrew from 45-5 to 48 kg (40 g/day). Following thedigestibility trial, the sheep were offered a diet of 900and 500 g DM Atriplex and tapioca, respectively.After 30 days, the sheep had increased their liveweight by about 3 kg (100 g/day). Unfortunately,feeding this ration could not be continued as therewas not enough Atriplex available. Possibly thehigher intake of tapioca enabled a higher nitrogenretention, enough to allow for a live-weight increase.

AcknowledgementsThis study was carried out with the financial support of theGerman Israel Agricultural Research Agreement (GIARA).We thank D. Barkai and Y. Hefetz (Department of NaturalResources, Agricultural Research Organization) whohelped feed the sheep. This work forms contribution no.3129-E (1990 series) of the Agricultural ResearchOrganization, Volcani Center, Bet Dagan.

ReferencesAgricultural Research Council. 1980. The nutrientrequirements of ruminant livestock. CommonwealthAgricultural Bureaux, Slough.Arieli, A., Nairn, E., Benjamin, R. W. and Pasternak, D.1989. The effect of feeding saltbush and sodium chloride onenergy metabolism in sheep. Animal Production 49:451-457.

Association of Official Analytical Chemists. 1975. Officialmethods of analysis of the Association of Official AnalyticalChemists. 12th ed. Association of Official AnalyticalChemists, Washington, DC.

Benjamin, R. W., Barkai, D., Hefetz, Y., Lavie, Y. andYaron, A. 1986. The apparent digestibility of Atriplexnummularia and the nitrogen balance of sheep consuming it.In Fodder production and its utilization by small ruminants inarid regions (FOPAR) (ed. A. Dovrat), fourth annual report,Institutes for Applied Research, Ben-Gurion University of theNegev, Beer Sheva, Israel.

Chen, M. 1975. [Water and food intake in Awassi andGerman Mutton Merino sheep.] M.Sc. Thesis, HebrewUniversity of Jerusalem, Israel.

Contreras, D. 1977. Analisis del preidio "Corral di Julio" comounidad di producicon en el semi arido del Norte Chico.Universidad de Chile, Facultad de Agronomia, Santiago.

Duncan, D. B. 1955. Multiple range and multiple F tests.Biometrics 11:1-42.

Hassan, N. I. and Abdel-Aziz, H. M. 1979. Effect of barleysupplementation on the nutritive value of saltbush (Atriplexnummularia). World Review of Animal Production 15: (4),47-55.

Hassan, N. I., Abdel-Aziz, H. M. and El-Tabbakh, A. E.1979. Evaluation of some forages introduced to newly-reclaimed areas in Egypt. World Review of Animal Production15: (2), 31-35.

Newman, D. M. R. 1969. The chemical composition,digestibility and intake of some native pasture species incentral Australia during winter. Australian Journal ofExperimental Agriculture and Animal Husbandry 9: 599-602.

Pasternak, D., Nerd, A., Aronson, J. A., Klotz, H., Yagil, R.and Venkert, R. W. 1986. Fodder production with salinewater. Report for the years 1984-1985, Institutes for AppliedResearch, Ben-Gurion University of the Negev, Beer Sheva,Israel.

Statistical Analysis Systems Institute. 1985. User's guide:statistics, version 5. Statistical Analysis Systems, Cary, NC.

Storey, R. and Wyn Jones, R. G. 1977. Quaternaryammonium compounds in plants in relation to saltresistance. Phytochemistry 16:447-453.

Tilley, J. M. A. and Terry, R. A. 1963. A two-stagetechnique for the in vitro digestion of forage crops. Journal ofthe British Grasslands Society 18:104-111.

Wilson, A. D. 1966. The value of Atriplex (saltbush) andKochia (bluebush) species as food for sheep. AustralianJournal of Agricultural Research 17:147-153.

Wilson, A. D. 1977. The digestibility and voluntary intakeof the leaves of trees and shrubs by sheep and goats.Australian Journal of Agricultural Research 28: 501-508.

Yaron, A., Lavie, Y., Forti, M. and Benjamin, R. W. 1985.Atriplex nummularia, Atriplex canescens and Cassia sturtiigrown under dryland conditions in the Negev. Value asfeed and as a nitrogen supply for ruminants. In Fodderproduction and its utilization by small ruminants in arid regions(FOPAR) (ed. A. Dovrat), third annual report, Institutes forApplied Research, Ben-Gurion University of the Negev, BeerSheva, Israel.

(Received 18 December 1990—Accepted 14 October 1991)