Palatability and nutritive value of some common plant ...

Journal of Arid Environments (1996) 34: 115–123

Palatability and nutritive value of some common plant species from the Aqaba Gulf area of Sinai, Egypt

S.Z. Heneidy Botany Department, Faculty of Science, University of Alexandria, Egypt (Received 18 February 1995, accepted 13 May 1995) The Sinai Peninsula includes rangeland with highly palatable plant species. Many physical and chemical factors influence palatability of plant species, of which animal behaviour and chemical composition are the most important. Average digestible crude protein (DCP) in the study area was 4·6%, which almost meets the requirements of the grazing animals. Average total digestible nutrients (TDN) was 66·5%. Average gross energy (GE) was 4100 kcal kg–1, digestible energy (DE) was 2650 kcal kg–1 and metabolisable energy (ME) was 2200 kcal kg–1. The energy content in the study area was equal 0·66 Scandinavian feed units. Therefore it appears that animals feeding on Sinai pasture receive most of their requirements. ©1996 Academic Press Limited Keywords: palatability; parts grazed; digestible crude protein; total digestible nutrients

Introduction The Sinai Peninsula is situated on the border between Asia and Africa and comprises an area of 61,000 km2 (Fig. 1). Sinai proper lies between the Red Sea Gulfs of Suez and Aqaba, and is bordered in the north by the calcareous plateau of El-Tih. It is an arid region where land-use is mainly grazing with some rain-fed farming in waterspreading areas (runoff farming). This area is lacking in adequate scientific studies, especially in the field of range management. The pasture species growing in Sinai (shrubs or semi-shrubs and herbs) are related to the amount of rainfall (range of 30–70 mm year–1) and exhibit varied nutritive values. Pasture production is low, therefore the area is also poor in livestock production (El-Shaer, 1981). Animals in southern Sinai mainly depend on natural vegetation to provide their nutrient requirements. Pasture plants vary in their distribution. However, annual species are found in a high density in the coastal region of the Gulf of Aqaba throughout the year, forming long strips of pasture boundering the Gulfs of Suez and Aqaba (c. 240 and 170 km long, respectively). In addition to natural grazing, some supplementary foodstuffs are offered by the Government (such as a co-operative feed mixture (manufactured concentrate consisting of a mixture of cotton seed cake, barley 0140–1963/96/010115 + 09 $18.00/0

© 1996 Academic Press Limited

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grains and bran), berseem (Medicago sativa L.), hay and barley) to help maintain production of livestock (El-Shaer, 1981). Goats, sheep and camels are the most important stock species grazing in southern Sinai (Ministry of Agriculture, Department of Animal Production in Southern Sinai, 1981, as quoted by El-Shaer, 1981). There are approximately 44,917 goats, 12,698 sheep and 16,282 camels. Generally, goats and sheep are smaller in size and weight than those in the Nile valley because of food shortage. Supplementary feed is provided to replace the natural resources during the dry season, and most of the grazing animals are moved to the north of Sinai when range herbage becomes limiting. The majority of the inhabitants in Sinai are pastoralists (sheep, goats, camels), hence the importance of studying range management in the area, especially as there is a lack of the information required to improve management. The present study was initiated to collect information about pastures in the Aqaba Gulf area which could help understand local grazing systems. The objectives of the study were: (1) to identify the different range species; (2) to assess the value and palatability of the species, and (3) to determine the nutritive value of the plants to evaluate the quality and quantity of the range. 34° MEDITERRANEAN SEA PORT SAID

RISH

EL-A

ISMAILIA

NAKHL SUEZ

30° Plateau of EL-Tih TABA

FO

L GU St. KATHERINA

EL TOR 0

50 km

AQA

DAHAB

GUL F OF

Z

BA

UE FS

NUWEIBA

TIRAN Ras Mohamed RED SEA

Figure 1. Map of Sinai showing the location of the study area.

FEED VALUE OF SINAI PLANTS

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The study area The desert of Sinai belongs to the Arabian Type desert (McGinnies et al., 1968), and is characterised by: (1) arid to extremely arid climate with a Mediterranean influence; (2) precipitation mainly in winter (ranges 250 mm at the northern boundary (Negev Desert) to 10–20 mm in the south of Sinai) (Danin, 1983); and (3) mean temperature of 10–20°C in the coldest month and 20–30°C in the warmest month. The study area extends approximately between latitudes 25° 30' N, and longitudes 34° 0' E and 34° 30' E, from Ras-Mohammed, to the south of Nuweiba, parallel to the Aqaba Gulf (Fig. 1). Near its southern end the Sinai peninsula has an intricate complex of high, very rugged igneous and metamorphic mountains rising to 2500 m (Said, 1962). The top of these mountains are covered with a Mediterranean-type steppe dominated by Serephidium herba-alba (Asso) Y.R. Li (syn. Artemisia herba-alba Asso). Mean annual rainfall at the top of the mountains probably ranges between 150 and 200 mm. Most of the grazing is concentrated in the wadis and valleys where runoff occurs (Le Houérou & Boulos, 1991). In Sinai there are large expanses of gravel plains where the silty soil is covered by chert gravels. This soil type is known as reg (Dan & Raz, 1970) or hammadas (Ravikovitch, 1967). The chalk, marl and clay are composed of fine-grained components and are characterized by a loess-like surface material which accumulates as the result of weathering of the Cretaceous limestone rocks (Danin, 1983). The northern two-thirds of the peninsula is occupied by a great northward-draining limestone plateau. The highest part of the limestone plateau forms Gebel El-Tih. The central portion of the plateau drains to the Mediterranean by the numerous affluents of Wadi El-Arish. The eastern and western edges are dissected by numerous narrow wadis draining to the Gulfs of Aqaba and Suez. Southern Sinai belongs to the hyperaid province (P/ETP < 0·03, where P is the annual precipitation, and ETP is the potential evapo-transpiration) (Ayyad et al., 1983). The site of the study extends parallel to the Aqaba Gulf. Observations on vegetation and grazing animals behaviour were recorded in different locations distributed randomly within this site.

Methods Several flocks of grazing animals (sheep, goats and sometimes camels) were observed at two different times during the rainy season at different locations within the study area. Records were collected on the plants and plant parts which were preferred and actually consumed by the grazing animals as well as the unpalatable species. Samples of the eaten parts (young branches, leaves, flowers, fruits and lateral branches), of the selected common species were collected during the survey. The samples were cleaned, dried and analysed as follows: total carbohydrates (NFE) were estimated according to Murata et al. (1968). Crude protein (CP), ether extract (EE), total organic matter and ash were estimated according to Allen et al. (1974). Crude fibre (CF) was calculated from the formula CF = 100 – (CP + EE + NFE) (Le Houérou, 1980a).

Results The vegetation of the study area is floristically very rich, especially in the wadis during the growing season. Most of these species are referred to as good rangeland species, a selection of which are shown in Table 1. The present study deals with a selection of 14

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perennials and three annuals from a pool of other annual species (grasses) (Table 1). About 44% of the species are highly palatable, 22% are palatable, 17% less palatable and 17% unpalatable (Table 1). As a preliminary study, the palatability index, based on observation, is a very important source of useful information about the rangeland species in the study area. Some of these species are among the most common and are heavily grazed by domestic animals. On the other hand, most of these species are perennials, and constitute the major forage species, thus representing the skeleton of the grazing ecosystem in the study area. The percentage chemical composition of the grazeable parts of different plant species is presented in Table 2. The maximum percentage of NFE is attained in the grazeable parts of Ochradenus baccatus*, approximately 44·7%, while the minimum NFE is from similar parts of Nitraria retusa with 31·3%; O. baccatus also gave the maximum of CF and the minimum CP (it is notable that O. baccatus is a palatable species, while N. retusa is not). The annual Trigonella stellata gave the maximum CP (15·3%). Artemisia inculta attained maximum EE, 11·8%, with a high CP content and low CF content. Annuals attained the maximum concentration of mineral ash, 27%. Table 1. Palatability rating, family, life-form and parts consumed of different plant species

Palatability Species Acacia tortilis (Forssk.) Hayne subsp. raddiana (Savi) Brenan Aerva lanata (L.) Juss. ex Schult. Artemisia inculta Del. Avicennia marina (Forssk.) Vierh. Calligonum comosum L’Hér. Iphiona mucronata (Forssk.) Asch. & Schweinf. Nitraria retusa (Forssk.) Asch. Ochradenus baccatus Del. Pulicaria undulata (L.) Kostel Salvadora persica L. Schouwia thebaica* (DC.) Webb Tephrosia appollinea (Del). Link Trigonella stellata* Forssk. Zygophyllum album L. f. Aeluropus lagopoides (L.) Trin. ex Thwaites Panicum turgidum (L.) Forssk. Asphodelus fistulosus* L. Annuals (grasses)

Family

Lifeform

1

Mimosoideae** Amaranthaceae Compositae Avicenniaceae Polygonaceae Compositae

Ch. Ch. Ch. Ch. Ch. Ch.

HP – HP UP HP –

Nitrariaceae Resedaceae Compositae Salvadoraceae Cruciferae Papilionoideae** Papilionoideae** Zygophyllaceae Gramineae Gramineae Liliaceae Gramineae

Parts 2 consumed HP P HP UP HP P

Y.B. Y.B. Y.B. – Y.B. Y.B.

Ch. UP Ch. P Ch. UP Ch. P-HP Th. – Ch. – Th. HP Ch. UP Cr. –

UP LP LP P LP HP HP UP HP

– Y.B. L. Y.B. L. L.B. A.Gr. – A.Gr.

Cr. Th. Th.

HP P HP

L.B. L+Fl. A.Gr.

– – HP

Th. = Therophytes; Cr. = Cryptophytes; Ch. = Chamaephytes. HP = highly palatable; P = palatable; LP = less palatable; UN = unpalatable. L. = leaves; L.B. = lateral branches; Y.B. = young branches; L+Fl = leaves + flowers; A.Gr. = above ground. 1 = determined in a previous study (Le Houérou, 1980b); 2 = observation of the present study. *Annual species; **Subfamily (Family Leguminosae). *Nomenclature follows Täckholm (1974).


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Table 2. Chemical composition [percentage of nitrogen free extract (NFE), crude protein (CP), ether extract (EE), crude fibre (CF), ash and organic matter (OM)] of different plant species (grazeable parts)

Species

NFE

CP

EE

CF

Ash

OM

Acacia tortilis subsp. raddiana Aerva lanata Artemisia inculta Avicennia marina Calligonum comosum Iphiona mucronata Nitraria retusa Ochradenus baccatus Pulicaria undulata Salvadora persica Schouwia thebaica* Tephrosia apollinea Trigonella stellata* Zygophyllum album Aeluropus lagopoides Panicum turgidum Asphodelus fistulosus* Annuals (grasses)

34·24 35·62 32·70 29·32 40·58 36·23 31·31 44·66 35·72 38·32 37·22 38·22 36·28 32·91 37·67 39·37 38·74 33·22

13·2 6·21 11·8 6·50 2·90 5·21 6·80 3·50 11·9 5·13 9·30 10·4 15·3 7·10 3·70 6·63 7·63 5·25

5·0 9·61 11·84 7·64 8·14 8·31 3·85 6·39 8·34 2·66 10·6 6·50 7·36 5·47 6·12 5·33 7·99 4·29

36·56 34·36 35·52 30·02 42·22 36·65 32·36 41·93 33·39 37·42 34·32 37·84 34·88 34·42 30·39 39·93 35·75 30·21

9·01 14·20 8·01 26·52 6·16 13·60 25·68 4·32 10·71 16·47 8·50 7·10 6·38 20·10 22·12 9·12 9·51 27·03

89·0 85·8 91·86 73·50 93·84 86·40 74·32 86·48 89·55 83·53 91·44 92·94 93·82 79·9 78·48 90·89 90·11 72·97

*Annual species.

Aeluropus lagopoides also had a high content of nutrients, 22·1%, and represents an important forage of species in the salt marshes. Gross energy content (Mcal kg–1), total digestible nutrients (TDN) and digestible crude protein (DCP) are presented in Table 3. Total energy content (gross energy Mcal kg–1) in the grazeable parts of different plant species in the study area showed that the total energy content reaches its highest level in the grazeable parts of Artemisia inculta (4·7 Mcal kg–1) with little variation among the remaining species (ranging from 3·4 Mcal kg–1 in N. retusa to 4·5 Mcal kg–1 in T. stellata). The maximum TDN is attained in the grazeable parts of A. inculta, followed by the annual Schouwia thebaica with 70·1% and 69·5%, respectively. The minimum TDN concentration is attained in Aeluropus lagopoides, 66·6%. The highest contents of DE and ME in the grazeable parts are found in O. baccatus, despite its low contribution to the GE content. The maximum DCP contents were attained by T. stellata (10·7%) and Acacia tortilis subsp. raddiana (8·8%). The minimum DCP content was that of Salvadora persica (1·3%). Ochradenus baccatus contributes the highest content of OM (95·5%), while annuals contribute the least (73%). Discussion The importance of the Sinai Peninsula for domestic grazing animals is attributed to the presence of a variety of rangelands covering different landscapes, with varying floristic composition, which may provide different animal diets compared to other Egyptian rangelands. Palatability of range plant species is a very complex notion, and difficult to generalize as it is linked to many factors that vary in time and space and is relative to what other alternatives are available. Some of these variables are linked to the plant, others to the

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animals while a third category depends on various environmental factors (Le Houérou, 1980b). In the present study numerous factors were considered when classifying a plant as palatable or not; phenological stage, morphological form, odour, taste, chemical composition and its abundance relative to associated species. The topography of the habitat, climate and state of the animal itself are all contributing factors. Most of the species in the present study are highly palatable, which agrees with the evaluation of Le Houérou (1980b) for the majority of these species in other areas. Some of these species are also recorded from the western Mediterranean coastal area of Egypt, and their palatability is discussed by Abdel-Razik et al. (1988a,b) and Heneidy (1992). The forage value of a consumed plant is the result of two main components: (1) palatability and voluntary intake by livestock, and (2) nutritive value, i.e. chemical composition and digestibility (Le Houérou, 1980b). In the present study, data on the voluntary intake was not available, hence the forage value in this study was evaluated according to palatability and the chemical composition of different plant species. DCP in the study area was estimated using approximate analysis according to Demarquilly & Weiss (1970), quoted by Le Houérou (1980a): DCP = 0·93 CP – 3·52. This equation is only valid in the case of nitrogen concentrations ≥ to 0·61% (or CP > 3·81%) (De Ridder et al., 1982, quoted by Duivenbooden, 1985). The average DCP in the study area was 4·6%, excluding those species with CP < 3·81. Heneidy (1992) reported the percentage of DCP as 4·9% of the dry matter in plants from the western Mediterranean coastal area of Egypt, while Sarson & El-Hamroum (1974), quoted by Le Houérou (1980c) reported values of DCP in the range of 4–20% DM for Tunisia. It may be concluded that the pasture in the study area is good pasture for grazing animals. However, it requires better management in order to increase the Table 3. Energy content [gross (GE), digestible (DE), and metabolizable energy (ME) in Mcal kg-1], total digestible nutrients (TDN) and digestible crude protein (DCP) (%) in different plant species

Mcal kg

%

Species

GE

DE

ME

TDN

DCP

Acacia tortilis subsp. raddiana Aerva lanata Artemisia inculta Avicennia marina Calligonum comosum Iphiona mucronata Nitraria retusa Ochradenus baccatus Pulicaria undulata Salvadora persica Schouwia thebaica* Tephrosia apollinea Trigonella stellata* Zygophyllum album Aeluropus lagopoides Panicum turgidum Asphodelus fistulosus* Annuals (grasses)

4·19 3·52 4·65 3·57 4·41 4·16 3·42 4·43 4·35 3·72 4·53 4·39 4·53 3·75 3·64 4·19 4·32 3·63

2·66 2·66 2·77 2·27 2·99 2·63 2·29 3·06 2·68 2·62 2·79 2·83 2·76 2·47 2·25 2·83 2·78 2·27

2·24 2·24 2·35 1·84 2·57 2·21 1·86 2·64 2·26 2·19 2·37 2·41 2·34 2·04 1·82 2·41 2·36 1·84

61·3 69·1 70·13 67·48 68·29 68·16 64·49 66·86 67·39 63·76 69·46 66·14 62·99 65·72 66·6 65·67 67·62 65·02

8·75 — 7·45 2·53 — 1·33 2·8 — 7·55 1·25 5·13 6·13 10·71 3·09 — 2·65 3·58 1·36

*Annual species.


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Table 4. Annual average percentage of total digestible nutrients (TDN) in supplementary feed, Western Mediterranean Desert and the study area

Fodder

Determined by

TDN (%)

Soliman & El-Shazly, 1978 berseem barley corn

56·0 64·0 68·0

Western Mediterranean Desert

Abdel-Salam, 1985 Abdel-Razik et al·, 1988a

66·0 75·0

Aqaba Gulf, Sinai

Present study

66·5

Supplementary feed

productivity of the pasture. On the other hand, although some of the plants in the present study are unpalatable, they have a relatively high percentage of DCP (e.g. 3·1% in Zygophyllum album), while the reverse is true for the annual grasses. It is also concluded that DCP is not the only factor influencing palatability. The term TDN is only an approximate measure of the food energy available to the animal after digestion losses have been deducted (Lofgreen, 1951); TDN can be recorded as a measure of energy requirement of animals and the energy value of feeds. TDN was calculated using a legume and non-legume equation according to Abu-ElNaga & El-Shazly (1971). Table 4 compares the annual average percentage of TDN in supplementary feed and Egyptian pastures with that from the study area. TDN in the study area is 66·5% which is less than the average for the western Mediterranean desert (70·5%: Abdel-Salam, 1985; Abdel-Razik et al., 1988a), while it is higher than the average for common fodder crops (62·7%; Soliman & El-Shazly, 1978). Thus the nutritive value of the pasture in the study area is considered fair for grazing animals compared to common fodder crops. DE was calculated according to Crampton & Harris (1969). Average DE in the study area is 2650 kcal kg–1, compared with 2610 kcal kg–1 obtained by Heneidy (1992) in the western coastal region of Egypt. GE is calculated from protein analysis (Lofgreen, 1951) as about 4100 kcal kg–1, while it is about 3606 kcal kg–1 in the western coastal area (Heneidy, 1992). Average ME is about 2200 kcal kg–1 in the study area. Le Houérou & Hoste (1977) reported that 1 SFU* = 1650 kcal. Accordingly, the energy content in the study area is equivalent to 0·66 SFU. The energy content of forage at Omayed, Egypt was estimated by El-Kady (1983) as 0·3 SFU. Le Houérou et al. (1982) recorded the energy content of 1 kg DM of the best fodder roughage and good fodder crops (alfalfa) as 0·8 and 0·6 SFU, respectively. Le Houérou & Hoste (1977) estimated the energy content of shrub and dried annuals as between 0·2 and 0·4 SFU. It seems that the energy content of the pasture in the study area is close to the energy content of the best fodder roughage, and higher than that reported in alfafa. However, it is also higher than the energy content of the forage at Omayed. Conclusion In general, most species in the study area were highly palatable and browse species represented the main supply of most chemical components that are available *SFU = Scandinavian feed unit.

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throughout the year and needed by grazing animals. The area needs an extensive study of all the rangeland species, their productivity and consumption by grazing animals, to fill the gaps in our knowledge of this grazing system. The natural forage of the study area may be enough to meet animal requirements provided a good management plan is prepared to advise inhabitants about using their range resources on an annual basis. In view of the fact that there is no adequate legislation covering the utilization of the rangeland of the region for ensuring long-term sustainable productivity, it is necessary to improve the rangeland through better management of the available browse plants. In any rangeland improvement programme using browse plants the necessary steps are to investigate the indigenous species, and to introduce and multiply those best adapted to multiple utilization. The author wishes to thank Dr M.S. Abdel-Razik, Prof. of Plant Ecology, Botany Department, Faculty of Science, Alexandria University and Prof. H.N. Le Houérou of the CNRS/CEPE, Montpellier, France, for their careful revision of the manuscript.

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