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Liveweight changes in sheep supplemented with seed pods of two leguminous trees in south Kordofan, Sudan, during the dry season

I.M. Hashim
Range/Livestock Section Centre
Western Sudan Agricultural Research Project, (WSARP)
P. O. Box 10, Kadugli, Sudan


Abstract
Introduction
Study area
Materials and methods
Results and discussion
References

Abstract

This paper examines the effect of supplementing seed pods of kadad (Dichrostachys cinera) and haraz (Acacia albida) on sheep liveweight change during the dry season. Seed pods were collected after maturity in December. Diet selected by sheep was determined by the bite-count method and intake was estimated by the faecal index method, using 4 non-lactating sheep for the total faecal collection. Seed pods and the diet selected were analysed for nitrogen (N), neutral detergent fibre (NDF), in vitro dry-matter digestibility (IVDMD) and in vitro organic matter digestibility (IVOMD).

Three groups of non-lactating sheep, with 4 ewes in each group were selected randomly from the stock of sheep belonging to WSARP at the research farm. The first group was supplemented with kadad seed pods, the second group with haraz seed pods and the third group was the control, which survived on range forage only. Supplements were offered every other day for 7 weeks. Sheep in the three groups were then mixed in a corral and weighed at random.

Crude protein (6.25 × % N) and NDF constituents of kadad were 10.9% and 53.1%, of haraz 16.5% and 59.2% and of the diet selected were 12.3 and 68.1% respectively. In vitro dry matter digestibility and IVOMD were 50.5% and 48.1% for kadad, 43.9% and 45.8% for haraz and 31.5% and 28.7% for the selected diet respectively.

Dry-matter intake was 2.9 kg/100 kg body weight and crude protein intake was 8.4 g/W0.75 kg/day. Kadad and haraz provided additional N supplements of 6.8 and 11.2 g/W0.75 every other day, respectively and more energy that resulted in an increase in liveweight (P<0.005) for the supplemented group. Sheep supplemented with haraz' however, gained more liveweight (P<0.05) than sheep supplemented with kadad.

Introduction

Sheep rank second to cattle in importance within the transhumant production system in south Kordofan. They are slaughtered for various religious occasions and also sold in local markets to cover cash expenditures (Fadlalla, 1985 a).

The primary constraint limiting sheep productivity is the poor nutrition during the dry season, which extends from November to June. During this period, crude protein contents of range forage decrease from 19.3 - 13.3% in July to 6.6 - 2.9% in December and standing crop of herbage decreases from 3830 kg/ha in October to 1838.4 kg/ha in February (Fadlalla, 1982) and is almost consumed by the end of June. Under these conditions, supplemental feeding is often of primary importance during the dry season (Williamson and Payne, 1959). To address this problem, sesame cake was supplemented to sheep during this period (Cook and Fadlalla, 1985) but with a limited success since the supplemented sheep performed only slightly better than the control.

In the experiment reported herein, seed pods of kadad (Dichrostachys cinera) and haraz (Acacia albida) are being tested as an alternative supplement for sheep during the dry season. Kadad yields about 1 kg of seed pods per tree (Hashim, in prep) and haraz yields 125-135 kg/tree of seed pods that can be dried and stored for future use (NAS, 1979). Objective of this experiment were: (1) to quantify the nutritive value of sheep diet and seed pods of kadad and haraz, (2) to determine intake and liveweight changes of non-lactating sheep supplemented with seed pods of the two locally available leguminous trees.

Study area

This study was conducted at the experimental farm belonging to Kadugli Research Station in south Kordofan. South Kordofan lies within the savanna zone of the sahelian belt, and can be classified as having hot, semiarid climate. March is the hottest month at Kadugli with a maximum of 41°C and a minimum of 24°C. December and January are the coolest months with 35°C and a minimum of 18°C. Rainfall varies from 700 to 800 mm, which occurs in a single season, primarily from June to September, although there is some rainfall in May and October. A short, hot season occurs after the rains from October to November, followed by cool, dry season from December to February. The main hot season occurs from March to May.

The research farm, which is fenced, encompasses 760.6 ha. The soil is dominated by cracking clays with patches of sandy clays and sandy loams. Acacia seyal dominates the cracking clays and sandy loams; associated with this species are Sorghum spp., Aristida hordaceae, Cymbopogon sp. and Dinebra refraflexa, Balanites aegyptiaca, Ziziphus spina-christi and Acacia polyacantha are widely dispersed in the research farm. Dichrostachys cinera exclusively covers patches of sandy clays and sandy loams.

The research farm is stocked with cattle, sheep and goats at the rate of 9 ha/head-year, 10 ha/head-year and 10 ha/head-year, respectively. Tap water is provided from the station headquarters to the camp site on the research farm year-round.

Cattle; sheep and goats are herded separately in the research farm, the herding usually starts at 8.00 a.m. After a distance of 1.5 km or so the animals are herded back to the camp for watering and shading, herded again in the evening for grazing and corraled at the camp around 5.30 p.m.

Materials and methods

Sixteen non-lactating sheep were selected and divided randomly into 4 groups, 1 group was used for studying diet selection and intake and the other 3 groups were for the feeding trials.

Sheep in the group of diet selection and intake studies were harnessed with bags that were specially designed to fit females. Sheep in this group were trained for accepting the bags while they were being herded as usual before the start of the experiment. After the completion of the training period, sheep were followed by two observers, one for determining herbaceous vegetation cover and the other for determining diet selected and intake. Either observer selected sheep randomly from the group.

The first bite made by the selected sheep was considered the starting point for the sampling of the herbaceous vegetation cover in each grazed area. From this point, 4 line transects each of 1/2 km long were randomly selected and were traversed. Readings for the cover determination were recorded at 50 m intervals along the line transects, using the ten-point frame procedure (Leavy and Madden, 1933). The sampling was continued for a week and was replicated for at least 3 sheep per day.

Diet selection was determined by the bite-count method (Reppert, 1960). About 100 bites were recorded for a single sheep per day and replicated for at least 3 sheep in each grazed area. The sampling continued for a week. The diet selected was composited for each sheep and was pooled for all sheep during the period of sampling.

Intake was estimated by the faecal index method (Maynard and Loosli, 1969) and 24 hr faecal collection according to the following equation.

where DMI is dry matter intake. The indicator used was faecal NDF (Waller et al, 1980).

Group feeding was conducted in a randomised complete block design (Steel and Torrie, 1960). In addition to grazing, one group was supplemented with seed pods of kadad, the second group with seed pods of haraz and the third group was control. All groups were corraled at 6.00 p.m. when supplements were offered following the usual practice of herding and grazing. Intake of the supplements was estimated by the following equation:

Intake, g/W0.75kg = 110.4 - 1716(100-CWC),

where CWC is the cell wall constituents and W is the body weight (Goering and van Soest, 1970).

Dry matter and N contents were determined according to AOAC (1984). Neutral-detergent fibre determination followed the procedure of Goering and van Soest (1970). In vitro dry matter digestibility followed the procedure of Tilley and Terry (1963) and IVOMD was determined as a loss in weight after being ashed ir a muffle furnace for 8 hrs at 500°C.

Initial weight was recorded for sheep, which were numbered in each group at the start of the experiment and every week thereafter. Weighing was standardised according to Harris et al. (1970). Sheep in the three groups were gathered in a corral at 7.00 a.m. and were given sufficient time to urinate and defaecate. Weighing was then conducted at random.

Liveweight changes in sheep were calculated as the difference between the starting weekly weight and the ending weekly weight and averaged for sheep in each group. Weight changes were then subjected to an analysis of variance and means were separated by the least significant differences (Steel and Torrie, 1960).

Results and discussion

Herbaceous vegetation constituted 1.7% of the ground cover, of which 0.6% were grasses and 0.5% were fortes. Litter constituted 17.9%, and the bare ground 81% (Table 1). Cover was not determined for trees and shrubs because in sandy soils where Dichrostachys cinera dominated, it formed inpenetrable thickets that rendered the sampling of this species and the species associated with it impossible. Pratt and Gwynne (1977) reported that D. cinera increased in overgrazed rangelands. After 3 years of grazing it diminished in size to form impenetrable thickets that had to be eradicated (Mckay, 1968).

During the dry season, sheep selected more shrubs and trees than grasses and fortes (Table 2). Although it was not important in the herbaceous cover and composition, Dinebra refraflexa was the grass species selected most. As for shrubs and trees, D. cinera constituted the major proportion of sheep diet; sheep ate its dead, fallen leaves and fallen seed pods. Fallen flowers and leaves of Acacia seyal and Balanites aegyptiaca were eaten by sheep as well as fallen fruits from the latter species. Seed pods of Acacia polyacantha and A. seyal also constituted a considerable proportion of sheep diet during the dry season.

Table 1. Herbaceous vegetation cover and composition in the research farm during the dry season.

Taxon

Cover %

Composition (%)

Grasses

Hyparrhenia pseudocymbora

0.26

23.4

Brachairia obtusiflora

0.05

4.5

Sehima ischaemoides

0.32

28.8

Forbs

Chorchorus sp.

0.16

14.4

Justicia sp.

0.32

28.8

Litter

17.89


Bare ground

81.00


Table 2. Diet botanical composition of sheep in the research farm during the dry season.

Taxon

Composition (%)

Grasses

Aristida hordaceae

0.42

Sehima ischaemoides

0.05

Dinebra refraflexa

10.54

Forbs

Ipomea sp.

0.83

Trees and shrubs

Dichrostachys cinera (leaves)

29.07

seed pods

9.88

Balanites aegyptiaca (leaves)

10.66

fruits

0.95

Acacia seyal (leaves)

0.74

flowers

33.12

Ziziphus spina-christi (leaves)

0.06

Acacia polyacantha (seed pods)

1.05

Albizia amara (leaves)

0.71

Acacia senegal (seed pods)

1.88

Cadaba farinosa

0.05

In Drongas area of south Kordofan, Schima ischaemoides constituted 71.6% of sheep diet, Balanites aegyptiaca 5.9%, A. seyal 5.7% and Dichrostachys cinera, A. polyacantha and Ziziphus spina-christi less than 1% (Fadlalla, 1985b). Fadlalla also reported that fortes and shrubs constituted over 90% of the transhumant sheep diet in late dry season.

Diet selected by sheep showed high crude protein and NDF constituents (Table 3), and low digestibility. The high NDF concentration and the low digestibility suggested low energy intake by sheep during the dry season. The high crude protein of the diet could be attributed to the high proportion of trees and shrubs (88%) in the diet, particularly fallen seed pods and flowers. During mid-dry season, sheep diet, which comprised 16% trees and shrubs, contained 8% crude protein (Fadlalla, 1985b). Crude protein constituents of the herbaceous vegetation during the same period ranged between 6.6 and 2.9% (Fadlalla, 1982).

Seed pods of Acacia albida showed high crude protein and energy contents (Table 3) and low dry matter and organic matter digestibilities compared to seed pods of Dichrostachys cinera.

Dry-matter intake was 814.8 g/head/day for sheep supplemented with seed pods of kadad, 855.9 g/head/day with haraz, and 908.6 g/head/day for the control (Table 4). During mid-dry season, dry-matter intake for lactating transhumant sheep was 1252 g/head/day (Fadlalla, 1985b). On Forb Range in Montana, dry-matter intake estimated for sheep during early, mid-and late dry season was 900, 1100 g/head/day, respectively (Buchanan et al., 1972).

Dry-matter intake per 100 kg body weight was 2.9 kg/day. For breeds of sheep, including Merino, Blackhead Persian and Droper, dry-matter intake per 100 kg body weight was 0.93, 1.27, 1.14 kg/day, respectively (Williamson and Payne, 1959). Fadlalla (1985b) reported 3.9 kg/day for pregnant sheep in south Kordofan.

Crude protein intake ranged between 100.2 and 111.7 g/head/day (Table 4), which is comparable with crude protein intake of 100 g/head/day by pregnant transhumant sheep (Fadlalla, 1985b). This could be related to the high crude protein content of the diet selected by sheep in this study.

Supplements of seed pods offered, which were 3.5 kg of kadad and 3.6 kg of haraz, were calculated according to the regression equation of Goering and van Soest (1970). The amount of supplement predicated by this equation was sufficient to feed each group of sheep ad libitum, the intake being 3.0 kg for kadad and 3.4 kg for haraz. However, the intake of the supplement predicted by this equation is subject to large errors and hence should be used with caution. The relationship, which was based on cell wall constituents and intake is fairly consistent in some forages but unpredictable in others (Goering and van Soest,

Table 3. Chemical constituents of supplements and the diet selected by non-lactating sheep in south Kordofan, Sudan during the dry season.



Supplement

Constituent

Diet

Dichrostachys cinera

Acacia albida

Dry matter

9.34

93.1

94.9

Crude protein

12.3

10.9

16.5

NDF

68.1

53.1

59.2

In vitro dry-matter digestibility

31.5

50.5

43.9

In vitro organic digestibility

28.7

48.1

45.8

Table 4. Performance of non-lactating sheep supplemented with seed pods of Kadad (Dichrostachys cinera) and Haraz (Acacia albida) in south Kordofan, Sudan during the dry season.


Item


Control

Supplemented

Kadad

Haraz

Number of animals

4

4

4

Average weight (initial) kg

31.0

27.8

29.2

Voluntary dry-matter intake:


g/day

908.6

814.8

855.9


g/W0.75

69.2

67.3

68.1


kg/100 kg BW

2.9

2.9

2.9

Crude protein intake:


g/head/day

111.7

100.2

105.2


g/w0.75/day

0.5

8.3

8.4

Supplement/every other day: amount offered (g/head)

-

875.0

900.0


intake, (g/head)

-

750.0

850.0

crude protein intake:





g/head

-

81.8

140.3


g/W0.75/head

-

27.0

44.7

Average 7-week weight


change (kg)

0.17

0.59a

1.12ab

Means with different superscripts are significantly different.

Supplemented sheep gained more liveweight (P<0.005) than the control. The two supplements provided additional N intake of 81.8 g/head by kadad and 140.3 g/head by haraz every other day, and additional energy as well. On the other hand, sheep supplemented with haraz gained more liveweight (P<0.05) than sheep supplemented with kadad. The control sheep lost liveweight during the experiment.

References

AOAC, 1-984. Official methods of analysis (13th ed). Association of Analytical Chemists, Washington, D.C.

Buchanan, H., Laycock, W.A. and Price, D.A. 1972. Botanical and nutritive content o the summer diet of sheep on a tall forte range in southern Montana. J. Anim. Sci. 35:423-430.

Cook, R.H. and Fadlalla, B. 1985. Dry season supplements of baggara sheep. In: R.H. Cook (ed.). Transhumant production systems 1984/1985 research results. Vol. III. WSARP publication No. 43. Khartoum, Sudan and Pullman, Washington, U.S.A. pp. 122-147.

Fadlalla, B. 1985b. The nutritional status of transhumant sheep. 1. Pregnant ewes during the dry season. In. R.H. Cook (ed.), Transhumant production systems 1984/1985 research results. Vol. III WSARP publication No. 43. Khartoum, Sudan and Pullman, Washington, U.S.A. pp. 31-43.

Fadlalla, B. 1985b. The nutritional status of transhumant sheep. 2. Lactating ewes during the mid-dry season. In: R.H. Cook (ed.), Transhumant Production systems 1984/1985 research results. Vol. III. WSARP publication No. 43. Khartoum, Sudan and Pullman, Washington, U.S.A. pp. 43-51.

Fadlalla, B. 1982. Effect of sampling date on yield of dry matter and crude protein of herbage clipped from ten enclosures around Kadugli, south Kordofan. Annual report 1981/1982. WSARP, Kadugli, Sudan.

Goering, H.K. and van Soest, P.J. 1970. Forage fibre analysis (apparatus, reagents, procedures and some applications). USDA-ARS Handbook No. 379. USDA.

Harris, L.E., Lofgreen, G.P., Kercher, C.J., Raleigh, R.J. and Bohan, V.R. 1970. Techniques of research in range livestock nutrition. Bulletin 471 (Technical). Utah Agricultural Experiment Station, Utah, U.S.A.

Leavy, E.B. and Madden, E.A. 1933. The point method of pasture analysis. New Zealand J. Agri. 46:267-279.

Maynard, L.A. and Loosli, J.K. 1969. Animal nutrition (6th ed). McGraw-Hill Book Company, New York.

McKay, A.D. 1968. Rangeland productivity in Botswana. E. Afri. Agr. and Forestry J. 34:178-192.

NAS, 1979. Tropical legumes: resources for the future. National Academy of Science, Washington, D.C.

Pratt, D.J. and Gwynne, M.D. 1977. Range management and ecology in East Africa. Robert E. Krieger Publishing Co. Inc. Huntington, New York.

Reppert, J.N. 1960. Forage preference and grazing habits of cattle at the Eastern Colorado Range Station. J. Range Manage. 13:58-62.

Steel, R.G. and Torrie, J.H. 1960. Principles and procedures of statistics. McGraw-Hill Book. Co., New York.

Tilley, J.M.A. and Terry, R.A. 1963. A two stage technique for the in vitro digestion of forage crops. J. Brit. Grassl. Waller, J., Merchens, N., Harrison, T. and Klopfenstein, T. 1980. Effect of sampling intervals and digesta markers on abomasal flow determination. J. Anim. Sci. 50:1122. Soc. 18:104-111.

Williamson, G. and Payne, W.J.A. 1959. An introduction to animal husbandry in the tropics. 3rd ed. Longmans, London.


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