Performance of sheep and goats with offspring on semi-arid saltbush (Atriplex nummularia) grassland ranges in the early dry season

R C W König ¹, K Becker ¹, R W Benjamin ² and H Soller ²

¹ Institute of Animal Production in the Tropics and Subtropics
University of Hohenheim
7000 Stuttgart 70, Germany

² Agricultural Research Organization
Volcani Center
50250 Bet Dagan, Israel

ABSTRACT

Fifteen sheep and 15 goats, each suckling a single offspring, were allocated to three grazing treatments: Atriplex nummularia shrubs plus undisturbed annual ground vegetation (GV) (T1: control); Atriplex plus GV reduced by herbicide spraying (T2); and Atriplex plus reduced GV plus concentrate supplement (T3). The proportions of GV in the diets were 75% in T1 and 50% in T2 and T3.

Dry-matter intake and free-water consumption were measured over 40 days together with milk production and changes in liveweight and body solids. Dry-matter intakes and liveweight changes of ewes plus lambs were 106 g/kg LW^0.75 and -31 g/day in T1, 80 g/kg LW^0.75 and -93 g/day in T2 and 78 g/kg LW^0.75 and -375 g/day in T3: the corresponding values for does plus kids were 104 g/kg LW^0.75 and +44 g/day in T1, 88 g/kg LW^0.75 and +34 g/day in T2 and 94 g/kg LW^0.75 and +38 g/day in T3. All mothers lost weight and body solids. Goats drank less water than sheep. The milk production of does was almost three times that of ewes. Goats tended to utilise Atriplex diets better than sheep.

RESUME

Performances de brebis et de chèvres allaitantes élevées sur parcours d'Atriplex nummularia et d'herbages en zone semi-aride au début de la saison sèche

15 brebis et 15 chèvres, allaitant chacune un petit, ont été soumises à l'un des trois régimes alimentaires suivants: Atriplex nummularia plus de la végétation naturelle (témoin) (T₁); Atriplex plus de la végétation naturelle en partie détruite par pulvérisation d'herbicide (T₂); et T₂ plus un complément de concentré (T₃). La végétation naturelle sur pied entrait pour 75% dans la ration T₁ et pour 50% dans les rations T₂ et T₃.

Les consommations de biomasse de matière sèche (MS) et d'eau ainsi que les variations du poids vif du poids sec et de la production de lait ont été mesurées sur une période de 40 jours. La consommation de MS et la variation de poids vif ont été déterminées pour la mère et son petit pris ensemble. A cet effet, les chiffres enregistrés chez les ovins étaient respectivement de 106 g/kg PV^0,75 et -31 g/j avec la ration T₁, 80 g/kg PV^0,75 et -93 g/j avec T₂ et 78 g/kg PV^0,75 et -37g/j avec T₃. En ce qui concerne les caprins, les valeurs correspondantes étaient respectivement de 104 g/kg PV^0,75 et +44 g/jour avec la ration T₁, 88 g/kg PV^0,75 et +34 g/jour avec T₂ et 94 g/kg PV^0,75 et +38 g/j avec T₃. On a enregistré une baisse du poids vif et du poids sec chez toutes les mères. Quant à la consommation d'eau, elle variait de 1,3 à 4,5 kg par kilo de MS ingérée et était plus élevée chez les ovins que chez les caprins. Les chèvres produisaient prés de trois fois plus de lait que les brebis. Enfin, l'utilisation de ces rations contenant du fourrage d'Atriplex était généralement meilleure chez les caprins que chez les ovins.

INTRODUCTION

Halophytic shrubs of the genus Atriplex, particularly A. nummularia (oldman saltbush), tolerate high levels of salt in soil and water and resist low and high environmental temperatures and droughts (Pasternak et al, 1986; Uchiyama, 1987). With its remarkable phytomass production and regrowth after browsing, and its relatively high crude-protein content and apparent high digestibility coefficients, this shrub might be a valuable protein supplement to nutrient-deficient herbage on rangelands and in arid and saline zones.

Results of previous studies on the effect of Atriplex on livestock performance have been inconsistent. In some grazing experiments in Australia, Chile and Israel, no or only temporary advantage could be attributed to the presence of saltbush (eg, Benjamin, 1980; Benjamin et al, 1986; Leigh, 1986). Only from South Africa and Libya it is reported that the addition of Atriplex to the diet of sheep substantially increased their liveweight (Jacobs and Smit, 1977; Dumancic et al, 1982).

Goats are reported to be more efficient utilisers of tree and shrub vegetation than sheep (Merrill and Taylor, 1981) but little information is available on their performance on Atriplex diets. Goats also appear to drink less water per unit liveweight than sheep (Ghosh, 1987). This is of interest for management decisions, as the ingestion of considerable amounts of salt via Atriplex, and the accompanying increase in water consumption (Wilson, 1966; Arieli et al, 1989), may restrict the use of this shrub as feed in arid environments.

This paper reports on a comparative study of the responses of sheep and goats to Atriplex diets with varying proportions of ground vegetation or concentrate supplement. The parameters assessed were liveweight, chemical body composition, milk production and intake of free water and dry matter.

MATERIALS AND METHODS

The experiment was carried out at the Migda Experimental Station in northern Negev, Israel (longitude 34° 35' E; latitude 31° 22' N.; altitude 100 m) during the early dry season (24 March to 20 May 1988). The site is situated in a semi-arid area with a mediterranean type steppe climate and annual rainfall of 270 mm (SD = 70 mm), all of which falls between November and April. In 1983, a 3-ha field had been planted with A. nummularia shrubs at a density of 1056 shrubs/ha. In summer 1987 the plantation was grazed until the shrubs were completely defoliated. They had a good biomass regrowth before the experiment began. The field was divided into three equal sections, one for each treatment, and each section was subdivided into two plots, one for sheep and one for goats. Two of the sections were sprayed with a herbicide to reduce the availability of natural herbaceous ground vegetation and one was left undisturbed. Ground vegetation consisted primarily of annual and perennial grasses and a few fortes and thistles.

The experimental animals were German Mutton Merino x Awassi x Finnish Landrace sheep and Damascus x Local Black Bedouin goats. Fifteen ewes and 15 does, each suckling a single offspring, were selected and, within each species, were divided into three equal groups by matching for date of parturition and liveweights of mothers and offspring. The three groups of each species, consisting of five mothers with their five offspring, were then allocated to one of the following grazing treatments:

· A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding (T1)
· A. nummularia shrubs and reduced ground vegetation without supplementary feeding (T2)
· A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation (T3).

Treatment T1 represented good ground vegetation biomass availability after a winter with high rainfall, while treatments T2 and T3 represented biomass availability following a drought.

Animals began grazing at about 0800 hours and were corralled at the end of the day at about 1600 hours, at which time mothers in the T3 groups were individually fed 300 g pelleted concentrate feed (consisting mainly of maize, barley grain and soy); The animals changed to the next replicate plot when all the shrubs in their respective plot were completely defoliated, even if some ground vegetation still remained. Therefore, the total number of grazing days was not equal for all treatments. Grazing times on T1, T2 and T3 were, respectively, 47, 44 and 44 days for sheep and 47, 44 and 48 days for goats.

Before and after grazing in each plot the animals were separated from feed and water and the adults were injected intramuscularly with about 1 mg tritiated water (TOH), at the rate of 5 m Ci/kg liveweight, four hours after separation; the exact dosage of TOH was determined by weighing the syringes before and after the injection. Blood samples (10 ml) were taken from the jugular vein before the TOH injection and again after a further fast of 12 hours when TOH had equilibrated. At times of blood sampling all animals were weighed to the nearest 0.5 kg to determine shrunk liveweight.

Plasma was separated by centrifugation and stored at -4°C. Duplicate sub-samples (100 mg) of plasma per animal were weighed to the nearest milligram into counting vials. The samples were mixed with 5 ml of Bray's scintillation fluid and stored in the dark for 24 hours. Samples, and diluted TOH standards, were counted for radioactivity in a Kontron liquid scintillation counter for three minutes. The results were corrected for quenching and background activities and expressed as disintegrations per minute (dpm). When radioactivity of plasma duplicates differed by more than 5% a new set of duplicates was prepared.

The following formulae were used to calculate body water space labelled by tritium dilution (TOH space) and body solids:

The average daily dry-matter intake was calculated from the difference of estimated biomass of the vegetation components before and after grazing in each plot. Shrub biomass was estimated by the method of Seligman et al (1986) and ground vegetation biomass was determined by the calibrated weight estimate method of Tadmor et al (1975).

Samples of feedstuffs were dried and ground to pass through a 1-mm screen. Crude protein (N x 6.25) was determined by the Kjeldahl method and crude ash was obtained by incinerating at 550°C for four hours. The in vitro digestibility of feedstuff dry matter was determined by the method of Tilley and Terry (1963).

Water troughs equipped with swimmer automates supplied groups of animals separately. The flow of water was measured with an automatic water meter. Drinking water was available ad libitum, but access to the troughs was restricted to one hour after grazing commenced in the morning and one hour at the end of the day.

Daily (24-hour) milk production was estimated four times in each group. Two methods were used. In one, offspring were separated from their mothers for 12 hours and then weighed on an electronic balance, accurate to 25 g, before and after suckling. The process was repeated after another 12 hours of separation. In the second method, mothers were separated from their offspring for 12 hours and then injected with 5 ml of oxytocin per animal. Afterwards, their udders were milked out by hand and the amount of milk was measured volumetrically. Total milk produced per day per mother was calculated by summation.

Three-way analyses of variance were carried out for different criteria using species, treatment and replicate as independent variables. Computations were done using the statistical package Staview-512.

RESULTS AND DISCUSSION

Nutritive value of feedstuffs

Crude-protein and crude-ash contents and in vitro digestibility of A. nummularia, ground vegetation and concentrate feed are summarised in Table 1. (The Atriplex samples analysed comprised 25% soft terminal twigs and 75% leaves; these were the proportions of the plant parts seen to be eaten by the animals.) The crude-protein content of Atriplex (10.5%) is at the lower end of the expected range (Beadle et al, 1957; Kandil and El Shaer, 1989). The digestibility of Atriplex (73.3%) is, however, slightly higher than expected (Benjamin et al, 1986, 1987a; Silva-Colomer et al, 1986). The ground vegetation remained green for about 10 days at the beginning of the experiment but then dried out within eight days.

Dry-matter intake

Dry-matter intake was measured for each "production unit" (mother and offspring) rather than for individual animals. Results are shown in Table 2.

Intakes were highest in T1, where the high proportion of ground vegetation in the total diet represented good biomass availability after a winter with high rainfall. In T2 and T3, where the ground vegetation was artificially limited to represent a drought year, total intakes decreased but the share of Atriplex increased. The intake depression was more pronounced in sheep than in goats. Feeding the concentrate supplement (T3) increased total intake of goats but suppressed intake of Atriplex. In sheep fed the concentrate, total intake decreased slightly.

Table 1. Crude-protein and crude ash contents and in vitro dry-matter digestibilities of feedstuffs

Feedstuff		Crude protein (%)		Crude ash (%)		In vitro dry-matter digestibility (%)
		Mean	SD	Mean	SD	Mean	SD
Atriplex nummularia		10.5	1.55	25.2	1.66	73.3	3.51
Ground vegetation
	Green	8.9	0.28	9.0	0.77	75.2	0.69
	Dry	5.0	1.35	7.5	0.99	44.1	3.89
Concentrate		15.4	0.68	7.7	0.56	81.4	1.21

Table 2. Daily dry-matter intakes of sheep and goats

Treatment		Content in total diet (%)		Dry-matter intake per production unit (mother + offspring)
				Ground vegetation (g/day)		Atriplex (g/day)		Concentrate (g/day)	Total
		Ground vegetation	Atriplex	Mean	SD	Mean	SD		(g/day)	g/day LW0.75 per day a
Sheep
	T1	72.6	27.4	2401	238	907	375	0	3308	106.2
	T2	51.9	48.1	1248	197	1157	92	0	2405	80.4
	T3	43.5	43.6	1018	255	1020	135	300	2338	77.6
Gods
	T1	72.6	27.4	1944	193	734	413	0	2678	104.4
	T2	49.7	50.3	1099	231	1113	99	0	2212	88.1
	T3	48.9	38.3	1148	110	899	89	300	2347	93.6

^a Mean metabolic weight calculated as mean LW^0.75 of mother plus mean LW^0.75 of offspring
T1 = A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding
T2 =A. nummularia shrubs and reduced ground vegetation without supplementary feeding
T3 = A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation

Water intake

Daily free-water intakes of sheep and goats and their offspring are shown in Table 3. Average absolute water intake remained constant within species, irrespective of treatment, with goats drinking less than sheep. This constancy does not mean that water intake was unaffected by treatment; the reduced dry-matter intake, and therefore the reduced water demand, in T2 and T3 obviously just compensated the increased water requirements with enhanced Atriplex intake. Actually the ratio of water to feed intake rose in T2 and T3. Sheep were more affected than goats.

With time, and therefore increasing temperatures and decreasing moisture content of the ground vegetation, water intake increased significantly (P<0.01). In sheep in T2, for example, the absolute water intake almost trebled, from 3.6 to 9.5 kg. This effect largely masked minor influences from species or treatment.

Other studies of sheep on Atriplex diets have found water-intake values of 1-8 kg/head or 0.5-5.9 kg/kg DMI (Wilson, 1966), 4-8 kg/head (Jacobs and Smit, 1977) and 7.9 kg/head or 10.3 kg/kg DMI (Arieli et al, 1989). For goats, values of 0.5-1.6 kg/head (Hassan et al, 1982) and 3-4 kg/head or 4-6 kg/kg DMI (Kandil and El Shaer, 1989) are reported. Ghosh (1987) quotes several sources where goats had lower water requirements than sheep under similar conditions (values in the ranges 0.09-0.19 kg/kg LW^0.82 in goats and 0.11-0.21 kg/kg LW^0.82 in sheep). In the present study water intake on a metabolic weight basis was not different between sheep and goats but absolute water intake and the water to feed intake ratio were lower in goats. In general the values are very comparable to those of Ghosh (1987), although those were not established on Atriplex diets.

Table 3. Mean daily water intake and ratio of water to feed intake of sheep and goats

Treatment		Water intake per production unit (mother + offspring)
		kg/day		kg/kg DMI a per day	kg/kg LW0.82 per day b
		Mean	SD
Sheep
	T1	6.44	2.35	1.95	0.16
	T2	6.23	1.58	2.56	0.16
	T3	6.71	2.21	2.98	0.17
Goats
	T1	5.27	2.18	1.94	0.16
	T2	5.25	1.46	2.34	0.16
	T3	4.99	2.14	2.14	0.16

^a Total dry-matter intake, including concentrate
^b Mean metabolic weight calculated as mean LW^0.82 of mother plus mean LW^0.82 of offspring
T1 = A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding
T2 = A. nummularia shrubs and reduced ground vegetation without supplementary feeding
T3 = A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation

Milk production

Milk production of ewes and does, as determined by two methods, is shown in Table 4. The two methods did not produce constantly different or similar results, and neither method could be clearly preferred over the other. Theoretically, the oxytocin method should give slightly higher values as the residual milk in the udder, which is not normally released, is included.

Several factors, such as the difference in time between sampling days and therefore possibly different milk production, and minor technical disturbances (wind, spillage), made both techniques rather crude and, given the high standard deviation of the data, it was not possible to quantify the influence of diet treatment on milk production of ewes or does. However, in both cases the methodology was good enough to show huge differences in milk production between ewes and does. On average, kids received almost three times as much milk as lambs did (618 vs 224 ml) and this difference was clearly reflected in the higher weight gains of kids compared to lambs.

Table 4. Milk production of ewes and does, measured by two methods

Treatment		Milk production (ml/day)
		Weighing		Oxytocin		Average
		Mean	SD	Mean	SD
Ewes
	T1	280	220	116	112	198
	T2	170	157	296	234	233
	T3	200	160	280	180	240
Does
	T1	860	540	538	98	699
	T2	610	417	442	203	526
	T3	650	366	610	187	630

T1 = A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding
T2 =A. nummularia shrubs and reduced ground vegetation without supplementary feeding
T3 =A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation

Live weights

Mean liveweights and liveweight changes of ewes, lambs, does and kids are presented in Table S. Initial liveweights within a class of animal (ewes, lambs, does, kids) were not significantly different (P>0.05). Between species and between classes of animals there were significant differences (P<0.05). All mothers lost weight; all offspring gained weight. On a production unit (mother plus offspring) basis, sheep lost weight and goats gained weight in all treatments.

Gains of kids tended to decrease on reduced ground vegetation (T2) compared to T1, but losses of does remained constant. For sheep, gains of lambs were constant but ewes lost weight significantly. Compared to T2, concentrate supplements (T3) improved performance of all classes of animals except does.

Differences between treatments were not significant (P>0.05). Nevertheless, they seem to be real as they largely correspond to the pattern found in the milk production and feed intake results.

In a similar trial at the same site in the wet season, lactating ewes lost 147 and 18 g/day at high and low stocking rates, respectively, while their suckling lambs gained more than 200 g/day. The animals browsed about 700 g DM/day from shrubs including Atriplex; although little ground vegetation was available they received 1.5 kg concentrate per ewe (Benjamin et al, 1987b). Compared to that result, a maximum average loss of 120 g/day per ewe and a gain of 27 g/day per lamb in T2, where no concentrate was given and ground vegetation was limited, seems a rather good performance at a low input level. In a study by Dumancic et al (1982), ewes fed in pens on cut-and-carry A. nummularia or A. halimus showed liveweight changes of 10 and -27 g/day, respectively.

Table 5. Mean liveweights and liveweight changes of ewes, lambs, does and kids

Treatment		Ewes	Lambs	Ewes + lambs	Does	Kids	Does + kids
Liveweight at start of experiment (kg)
	T1	49.3	27.1	76.4	38.0	20.3	58.3
	T2	51.4	27.1	78.5	38.7	20.2	58.9
	T3	49.6	25.6	75.2	38.0	20.5	58.5
Liveweight change during experiment (g/day)
	T1	-57a	26	-31	-37	81	44
	T2	-120b	27	-93	-32	66	34
	T3	-80a	43	-37	-40	77	38

Within a column and data set, means followed by the same letter, or no letter, do not differ significantly (P>0.05). Species always differed significantly (P<0.05)

T1 = A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding
T2 = A. nummularia shrubs and reduced ground vegetation without supplementary feeding
T3 = A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation

Body solids

Mean body solids and their changes in ewes and does are shown in Table 6. All mothers lost body solids. Both ewes and does lost more body solids in T2, where ground vegetation was limited, than they did in T1. The relationship confirms the losses in liveweight of these groups. The heavy loss in liveweight of ewes in T3 is not reflected to the same extent by a loss in body solids. It is possible that ewes profited relatively more from the concentrate supplement than does did.

Table 6. Mean body solids and their changes in ewes and does

Treatment		Ewes	Does
Body solids at start of experiment (kg)
	T1	14.7a	9.4a
	T2	18.0b	11.2b
	T3	14.2a	11.4a
Change in body scuds during experiment (g/day)
	T1	-100a	-60a
	T2	-175b	-98b
	T3	-9c	-94b

Within a column and data set, means followed by the same letter do not differ significantly (P>0.05). Species always differed significantly (P<0.05)

T1 = A. nummularia shrubs and undisturbed ground vegetation without supplementary feeding
T2 = A. nummularia shrubs and reduced ground vegetation without supplementary feeding
T3 = A. nummularia shrubs and reduced ground vegetation plus concentrate supplementation

The absolute values for body solids are probably underestimated as they were calculated from the TOH dilution space, and the TOH space may overestimate actual total body water (Panaretto and Till, 1963; Donnelly and Freer, 1974). A correction factor might be applied but it would affect the results equally and the relative change would remain the same. The daily losses of body solids were higher (except for ewes in T3) than the losses in liveweight. This means that the animals melted down their body fat reserves and incorporated water to the extent of around 50 g/day. In other studies where Atriplex was a major part of the diet, both sheep and goats increased the proportion of water in their bodies (MacFarlane et al, 1967).

CONCLUSIONS

In the early dry season Atriplex-grassland pastures can provide enough nutrients to does and kids for combined net weight gain, but not to ewes and lambs. Hence, goats tend to utilise Atriplex diets better than sheep do.

Goats tend to drink less water than sheep, and to have a lower water to feed intake ratio, when fed Atriplex diets, although their milk production is higher than that of sheep.

Even small amounts of concentrate improve the performance of mothers and offspring fed diets containing about 50% Atriplex.

REFERENCE

Arieli A, Naim E, Benjamin R W and Pasternak D. 1989. The effect of feeding saltbush and sodium chloride on energy metabolism in sheep. Animal Production 49:451-457.

Beadle N C W. Whalley R D B and Gibson J B. 1957. Studies in halophytes. 2. Analytic data on the mineral constituents of three species of Atriplex and their accompanying soils in Australia. Ecology 38:340-344.

Benjamin R W. 1980. The use of forage shrubs in the Norte Chico region of Chile. In: le Houérou H N (ed), Browse in Africa The current state of knowledge. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia, pp. 299-302.

Benjamin R W. Barkai D, Lavie Y and Forti M. 1986. Summer grazing of a 18-month old plantation of fodder shrubs by weaned ewe lambs. In: Dovrat A (ed), Fodder production and its utilization by small ruminants in arid regions. Fourth Annual Report No BGUN-ARI-61-86. Institute for Applied Research, Ben Gurion University of the Negev, Beer-Sheva, Israel. pp. 8-27.

Benjamin R W. Oren E and Katz E. 1987a. Apparent digestibility of Atriplex barclayana and the nitrogen balance of sheep consuming it. In: Benjamin R W. Seligman N G. Forti M and Becker K (eds), Analysis of animal nutrition in shrub-grassland grazing systems with special reference to semi-arid Africa. Report No BGUN-ARI-41-87. Institute for Applied Research, Ben Gurion University of the Negev, Beer-Sheva, Israel. pp. 7-35.

Benjamin R W. Barkai D, Lavie Y and Forti M. 1987b. Winter grazing of a fodder shrub component within sheep production systems. In: Dovrat A (ed), Fodder production and its utilization by small ruminants in arid regions. Fifth Annual Report No BGUN-ARI-48-87. Institute for Applied Research, Ben Gurion University of the Negev, Beer-Sheva, Israel, pp. 5-20.

Donnelly J R and Freer M. 1974. Prediction of body composition in live sheep. Australian Journal of Agricultural Research 25:825-834.

Dumancic D, Eskileh M and le Houérou H N. 1982. Study on fodder shrubs consumption by sheep in Wishtata range development project. Report No LIB 18. FAO (Food and Agriculture Organization of the United Nations), Rome, Italy. 11 pp.

Ghosh T K 1987. Water requirements and water feeding strategies in goats. In: Santana O D, da Silva A G and Foote W C (eds), Proceedings of the 4th International Conference on Goats, 8-13 March 1987, Brasilia. Departamento de Difusao de Technologia, Brasilia, Brazil. pp. 1267-1274.

Hassan N I, El-Shaer H M and Kandil H M. 1982. Lamb performance on pasture supplemented with concentrates. World Review of Animal Production 18(4):37-40.

Jacobs G A and Smit C J. 1977. Benutting von vier Atriplex-spesies deur skape. Agroanimalia 9:37-43.

Kandil H M and El Shaer H M. 1989. The utilization of Atriplex nummularia by goats and sheep in Sinai. In: Galal E S E, Aboul-Ela M B and Shafie M M (eds), Ruminant production in the dry subtropics: Constraints and potential. Proceedings, International Symposium, 5-7 November 1988, Cairo, Egypt. EAAP [European Association for Animal Production] Publication No 38. Centre for Agricultural Publishing and Documentation (Pudoc), Wageningen, The Netherlands, pp. 71-73.

Leigh J H. 1986. Forage value and utilization of Chenopod dominated shrubland. Reclamation and Revegetation Research 5:387-402.

MacFarlane W V, Howard B and Siebert B D. 1967. Water metabolism of Merino and Border Leicester sheep grazing saltbush. Journal of Agricultural Research 18:947-985.

Merrill L B and Taylor C A. 1981. Diet selection, grazing habits, and the place of goats in range management. In: Gall C (ed), Goat production. Academic Press, London, UK pp. 233-252.

Panaretto B A and Till A R. 1963. The composition of mature goats and its relationship to the antipyrine, tritiated water and N-acetyl-4-amino antipyrine spaces. Australian Journal of Agricultural Research 14:926-943.

Pasternak D, Aronson J A, Ben-Dov J. Forti M, Mendlinger S. Nerd A and Sitton D. 1986. Development of new arid zone crops for the Negev of Israel. Journal of Arid Environments 11:37-59.

Silva-Colomer J, Fonolla J. Raggi L A and Boza J. 1986. Valoración nutritive del Atriplex nummularia en ganado caprina. Revista Argentina de Producion Animal 6(11-12):661-665.

Seligman N G. Benjamin R W. Lavie Y. Forti M and Mills D. 1986. Estimation of the standing biomass of fodder shrubs under grazing conditions. In: Dovrat A (ed), Fodder production and its utilization by small ruminants in arid regions. Fourth Annual Report No BGUN-ARI-61-86. Institute for Applied Research, Ben Gurion University of the Negev, Beer-Sheva, Israel. pp. 46-58.

Tadmor N H. Brieghet A, Noy-Meir J. Benjamin R W and Eyal E. 1975. An evaluation of the calibrated weight-estimate method for measuring production in annual vegetation. Journal of Range Management 28:65-69.

Tilley J M A and Terry R A. 1963. A two-stage technique for the in vitro digestion of forage crops. Journal of the British Grassland Society 18:104-111.

Uchiyama Y. 1987. Salt tolerance of Atriplex nummularia. Technical Bulletin of the Tropical Agricultural Research Center No 22. Tropical Agricultural Research Center, Yatabe, Tsukuba, Ibaraki, Japan, 69 pp.

Wilson A D. 1966. The intake and excretion of sodium by sheep fed on species of Atriplex (saltbush) and Kochia (bluebush). Australian Journal of Agricultural Research 17:155-163.