A. Study area

Foliage samples of T. nudatum were collected from the area of Mesrane in the province of Djelfa (3;03;E longitude, 34;36;N latitude and 830 m elevation) covered by a plant community, including Atriplex halimus, Suaeda fruticosa, and Salsola vermicular found in the Northern steppe of Algeria. The climate is typically Mediterranean, characterized by wet winters and hot dry summers with a mean annual precipitation of 250 mm/year. The average minimum winter and maximum summer temperatures are 5 ℃ in January and 26 ℃ in July, respectively. According to Halitim [11] the principal types of soil in the Mesrane zone are the calci-magnesic solontchak and isohumic soils.

B. Plant collection and sample preparation

Three 100 m transects were laid across the population of T. nudatum. These transects were further divided into three random blocks. Ten plants from each block were randomly harvested to measure chemical element content. Plant samples were clipped with stainless steel scissors with Teflon coated blades and, consequently, these samples were packed into paper bags. The samples were brought to the laboratory and were washed with distilled de-ionized water to remove any surface contamination and dried for 48 h in an oven at 60 ℃. The dried samples were ground to a fine powder in a high speed mill (IKA + A11 basic) to a particle size fraction of <200 μm. In order to minimize the contamination of Fe, Co, and Zn, dismountable Teflon coated blades were used for grinding.

Powdered plant samples were then stored in sterilized labeled polyethylene bottles and screw capped tightly to avoid absorption of moisture and any external contamination.

C. Instrumental Neutron Activation Analysis

The method used for the determination of chemical element mass fractions was a comparative (relative) neutron activation analysis, where both samples and standards were analyzed (irradiated and measured) under the same conditions. About 100 mg of the sample were sealed in quartz vials packed in aluminum containers and irradiated in the core of the reactor. For homogeneity, each sample was included in the mixture of 30 sample plants (i.e., 30 plants per transect). Three samples of plant material, together with triplicate CRM-GBW 07605 (GSV-4 tea leaves), were irradiated in the vertical channel of a multi-purpose, heavy-water research reactor (MHWRR) at a power of 5 MW, with a thermal neutron flux of 4.5×10¹³ cm^-1 s^-1 for 6 h, to carry out irradiation enough to activate the middle- and partially long-lived radionuclides in the samples. Before collecting data, a decay of 4 days and 4 weeks for the middle-lived and long-lived nuclides, respectively, was necessary. The powder was then put into new polypropylene capsules and reweighed. Both long and middle lived radionuclides were measured using a CANBERRA (HPGe p-type) coaxial detector and a CANBERRA inspector 2k. The system has a resolution (FWHM) of 1.87 keV for 1332.5 keV γ-peaks of ⁶⁰Co and a relative efficiency of 35% when operated by Genie 2k software, with a low dead time (< 5%). The data transferred from the inspector to the computer were processed using the Genie 2000 software. Middle-lived radionuclides (Na, K, and Zn) were measured after 4 days; the collection time was 3600 s for each sample and each standard. Whereas, the long-lived radionuclides (Ca, Fe, Co, Eu, Sb, and Sc) were measured after 4 weeks for a collection time of 7200 s. Table 1 presents radionuclides, possible interferences, and gamma-energy used in this study.

A. Chemical element contents

This investigation was conducted to determine the chemical element contents of T. nudatum used for animal gazing in the arid steppe of Algeria, in order to gain information on the deficiency and/or excess of mineral levels for ruminants grazing therein, fed mainly with this halophytic species.

Nine chemical elements were characterized in T. nudatum using INAA. Table 2 represents a comparison of our results for the reference materials to their certified values. For most of the elements, no significant discrepancy was observed between the measured concentrations and reference values. In order to evaluate the laboratory performance, we have determined the U-score test. This parameter is calculated according to the following equation

where x_lab and σ_lab are the laboratory measured value and the standard uncertainty of the laboratory measured value, respectively; x_ref and σ_ref are the certified value and the standard uncertainty of the certified value, respectively.

A U-score ࣘ1 is satisfactory (the result is in agreement with the certified value); and unsatisfactory (the result and certified value are not in agreement) if the U-score >3.29 [12]. This evaluation shows the good quality of the results obtained in this investigation (Table 2).

The results are presented in Table 3 where all mass fractions are reported on dry mass basis as the averages of at least three independent determinations with standard errors of mean (SEM). The chemical element contents quantified in T. nudatum follow the trend in a descending order: Na > K > Ca > Fe > Zn > Co > Sb > Sc > Eu.

Na and K have an electrochemical function in ruminants and are associated with maintenance of acid–base equilibrium, membrane permeability and the osmotic control of water in the body [13]. Mass fractions of K were high and adequate for ruminants, exceeding the critical level of 0.65% of diet dry matter, as recommended by the National Research Council (NRC) [14]. These results were in agreement with those found previously by Del Valle and Rosell [15] in shrubs growing in Northeastern Patagonia.

T. nudatum had Na contents well above the needs of a growing adult range ruminant (0.1 g of Na kg^-1 of diet dry matter for sheep). As stated by Masters et al. [16], small ruminants can tolerate a soluble salts intake in forage of about 100–150 g/day, provided that they have accessed to abundant water. High salt content is perhaps the major negative component in halophytic species. Therefore, mixing some halophytes with glycophyte forages is recommended for better utilization of saltbushes [5].

The Ca requirement for ruminants is 0.51% of diet dry matter, according to the NRC [14]. The results showed that the Ca mass fractions were higher than this requirement, therefore Ca deficiency would not be expected. Similar high forage Ca mass fractions were reported by Towhidi et al. [17] in other halophytes growing in a central arid zone of Iran.

T. nudatum contained Fe levels in substantial amounts to meet adult range ruminant requirements (45 mg of Fe kg^-1 of diet dry matter for sheep). Similar findings were reported by Ogebe and McDowell [18] and Khan et al. [19], who evaluated the Fe contained in native forages that grow respectively in semiarid regions of Nigeria and Pakistan.

It has been suggested that forage crops containing more than 27 mg of Zn kg^-1 of diet dry matter will protect livestock from Zn deficiency disorders [14]. In the present investigation, Zn mass fractions were sufficiently adequate for ruminant requirements. Other studies have found that browse halophytes from northern Brazil [20], arid regions of Jordan [21], and southern Tunisia [22] had sufficient amounts of Zn to meet requirements of adult range ruminants.

Co is often the most severe element deficiency of grazing livestock [13]. However in this study, T. nudatum had Co contents that were sufficient to meet adult range ruminant requirements (0.1 mg of Co kg^-1 of diet dry matter for sheep). These results were in sharp contrast to those reported by Chelliah et al. [23] who found poor forage Co mass fractions (<0.1 mg/kg) in North Florida.

The Sc, Sb, and Eu elements in T. nudatum are present in the descending mass fractions as Sc > Sb > Eu (Table 3). This halophyte is quantified with the lowest Sc, Sb, and Eu contents, with respective values of per-mode=symbol, 0.17, 0.033 and 0.034 mg/kg, and were far below the tolerable weekly intake recommended by the NRC [14]. Therefore, its toxic effects will be negligible. Similar low Sc, Sb, and Eu mass fractions were reported recently by Nordløkken et al. [24] in native species growing in southwest Norway.

B. Potential of ruminant mineral intake

Table 4 shows the potential of chemical element intakes and daily chemical element requirements by ruminants from the leaves of T. nudatum. It seems that a sheep weighing about 50 kg and consuming 2.0 kg per day DM of this halophytic species could eat substantial amounts of Ca, K, Fe, Zn, and Co to meet their requirements.