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Nutritive value of indigenous browse in Africa in relation to the needs of wild ungulates
ANIMALFEED SCIENCEAND TECHNOLOGY ELSEVIER
Animal Feed Science Technology 69 (1997) 143-154
Nutritive value of indigenous browse in Africa in relation to the needs of wild ungulates J.H. Topps* Deparimentof Agriculture,University of Aberdeen, King Street,AberdeenAB24 SUD, UK
Abstract From a review of published information on the nutritive value of indigenous browse in Africa, the intake of ruminant species of wild ungulates and the energy requirements for maintenance of these animals, an analysis has been carried out to assess the supply of energy and protein from browse in relation to meeting requirements. Although there are a large number of data giving chemical composition of browse, there is relatively little information on digestibility and energy value. Results on intake and energy requirements have been reported for a few species of wild ungulates and these have been used as such or formed the basis of derived values for other species. The analysis indicates that for four species of wild ungulates, differing in size from 20 to 500 kg, the intake of metabolisable energy may be 12-27% greater than or substantially less than the amount required for maintenance. The difference arises from the choice of values for fasting metabolism. The establishment of models of energy and protein systems, together with more measurements on the nutritive value of indigenous browse are advocated in order to obtain a better knowledge of the nutrient needs and productivity of wild ungulates that utilize indigenous browse. 0 1997 Elsevier Science B.V. Keywords: Wild ungulates;
Ruminants;
Browse; Intake; Energy requirements
1. Introduction Indigenous browse is the main source of forage (leaves and twigs) for several species of wild ungulates in Africa. In addition it makes an important contribution *Tel.: f44 1224 318685. 0377-8401/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PZZ SO377-8401(97)00102-8
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to the intake of food by other wildlife species, and goats and cattle have been known to browse during a drought when there is almost a complete absence of grazing. There are several hundred species of trees and shrubs which are known to be browsed by domestic livestock or wild ungulates in Africa (Le HouCrou, 1980) and a large number have been studied as an animal feed source in one or more locations. Valuable information has been accumulated on chemical composition as a guide to nutritive value, and in recent years, on the presence of secondary plant compounds which may act as anti-nutritional factors. From these data it has been concluded that in all the drier parts of Africa, the nutritive value of browse appears to be better than that of the native grasses throughout the year, except for the early season of grass growth. However, the presence of secondary plant compounds, especially those referred to as tannins, casts some doubt as to the availability of nutrients in browse (Barry and Manley, 1984) and to the validity of this general conclusion. In Zimbabwe there is increasing interest in the ranching of game animals (White, 1995). Furthermore, most of the countries in Southern Africa and in East Africa are blessed with a diverse range of these species, which has an enormous intrinsic and commercial value. Any reduction in this resource would erode the capacity within Southern Africa of making use of dry, fragile areas and of earning foreign exchange. Indigenous browse, therefore, is an essential component of many multi-species systems and the extent to which it is used to sustain animals that browse needs to be known. This paper reviews knowledge on the nutritive value of indigenous browse and attempts to relate it to the needs of ruminant species of wild ungulates. In establishing this relationship, three separate but related pieces of information about these species are needed. These are: . the nutritive value of browse consumed; . the intake of browse and the sources of variation; . the energy and protein requirements for maintenance. There is a lack of information in all three areas, so some use has been made of the data in the publications edited by Le HouCrou (1980) and Hudson and White (1985) and in the book written by Robbins (1983).
2. Nutritive value of browse consumed by game animals 2.1. Chemical composition There are a large amount of data on the chemical composition of browse in Africa (Le HouCrou, 1980). Much of it has been obtained using the proximate analysis of feeds which fractionates the dry matter into the following constituents: 1. Crude protein 2. Ash
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3. Crude fibre 4. Ether extract 5. N-free extractive This scheme provides only a small amount of useful data, i.e. crude protein and ash contents. Crude fibre is not a measure of the fibrosity of the plant material since it contains only some of the cellulose and lignin, the remainder being in the N-free extract which is obtained by difference, while the ether extract is likely to contain many other compounds in addition to true fat. An alternative approach is the Van So&t analysis of cell wall and its constituents, which gives a useful assessment of the total fibre in the plant and its composition (Gohing and Van So&t, 1970). The large number of results for crude protein content show that browse has a medium to high value. For example, Dougall et al. (1964) published values for 234 samples of browse collected in Kenya, of which 64 were from legume species (Table 1). Mean values for legume and non-legume species were 148 and 127 g kg- ’ DM, respectively with all but a few contents above 70 g kg- ’ DM. This indicates that protein in browse is less subject to seasonal changes than that in grasses which has been shown by Dube (1993) for four browse species in Zimbabwe. Very little information has been published on the availability of the protein to animals. Recent work in Zimbabwe (Baloyi et al., 1997) shows that the rumen degradability of protein in Brachystegiaspic$omis is in the range 0.4-0.5, and that tannins are present. It is possible that the presence of tannins impaired the degradation of protein. Ash content is inversely related to the total organic matter in the plant. Some species of browse have an average or low content of ash which means that organic matter content and gross energy value are higher in browse than that normally ascribed to plant material (Table 1). Values for detergent fibres in browse are often less than those for the surrounding grass vegetation especially during the dry season. A selection of values for Acacia species published by Pellew (1980) are shown in Table 2. Similar values were reported for seven browse species collected in South Africa by Hall-Martin et Table 1 Chemical composition (g kg-’ dry matter of species of browse harvested in Kenya (after Dougall et al., 1964)
Crude protein Mean Range Ash Mean Range
Legume n = 64
Non-legume n = 170
148 28-429
127 (n = 234)
86 30-267
117 (n = 234)
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al. (1982). They are difficult to interpret in terms of providing an indication of digestibility and energy value. While the content of neutral detergent fibre is low, which may indicate a high content of highly digestible cell content the lignin contents are high. The latter may be interpreted as an indication of heavily lignified and very indigestible cell wall. However, the values for neutral detergent fibre may underestimate the total content of cell wall since certain constituents such as pectin are soluble in the detergent solution. Furthermore, the acid detergent lignin fraction may not be an appropriate measure of lignin in browse due to the formation of artifacts arising from reactions of tannins with protein and carbohydrates (Mueller-Harvey and McAllan, 1992). Table 2 Chemical composition (g kg-’ of dry matter) of Acacia browse in the Serengeti Game Park (after Pellew, 1980) Crude protein
Neutral detergent fibre
Acid detergent fibre
Acid detergent lignin
A. tortilis New shoots Young shoots New leaves Old leaves
205 103 210 1.53
507 600 445 399
383 461 235 245
162 205 132 150
A. Senegal New shoots Young shoots New leaves Old leaves
336 141 329 219
479 603 401 448
290 431 203 248
111 222 89 103
A. xanthophloea New shoots Young shoots New leaves Old leaves
182 100 232 182
546 610 499 461
331 452 248 314
126 179 149 141
A. ho&ii New shoots Young shoots New leaves Old leaves
180 105 194 153
372 511 284 391
269 380 139 151
83 151 70 86
A. clavigera New shoots Young shoots New leaves Old leaves
242 102 202 126
452 492 399 353
268 359 228 213
102 143 142 106
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2.2. Digestibilityand energy value Relatively few values for digestibility are reported in the literature. Those given by Rees (1974) for Northern Zambia some of which are summarised in Table 3, are relevant to Zimbabwe. The values are for digestible dry matter content rather than a digestibility coefficient, but they show that 60% or less of the feed is digested. Very low values are obtained for old growth. A small proportion (approx. 5%) of the digestible DM will be in the form of ash so the digestible organic matter content will be lower. In ruminant nutrition, such values may be converted to energy values by the application of conversion factors (McDonald et al., 1995). Digestible organic matter in roughage and forages has an energy value close to 19.5 MJ kg-‘. For ruminant livestock, digestible energy (DE) may be converted to metabolisable energy (ME) by multiplying by 0.82, since the combined losses of
Table 3 Crude protein (CP) and digestible dry matter (DDM) contents (g kg -’ DM) of browse eaten by cattle in a Miombo region in Northern Zambia, together with approximate derived metabohsable energy (ME) values (MJ kg-’ DM) (adapted from Rees, 1974) Species
Growth
August
October
CP
DDM
ME
CP
DDM
ME
Baphia beguatii
New
281
615
9.0
235
571
8.4
Brachystegia glabem’ma
Old New
96 -
338 -
4.9 -
120
344
5.0
Old New
106 -
596 -
8.7 -
183
521
Old New
102 -
547
8.0
Old New
76
577
Old New
111 112
548 610
8.0 8.9
Old New
77
557
8.1
Old New
91 113
382 459
Old New
89 119
515 549
B. spicifonnis
B. utilis
Diplorhynchus condylocarpon
Julbernardiapaniculata
Mono&
spp.
Ochthocosmus lemaireanus
Uapaca nitida
-
7.6 -
178
464
6.8 -
8.4 152
627
9.2
113
574
8.4
123
418
6.1
5.6 6.7
153
664
9.7
7.5 8.0
189
646
9.5
-
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energy in urine and in methane are 18% of DE for many feeds. However, Robbins (1983) has listed values for this coefficient for wild ruminants given either deciduous or evergreen browse in temperate regions. The values range from 0.76 to 0.83 with a mean of 0.79 which is used, along with 19.5 MJ kg-’ to derive the ME values given in Table 3. The lower value of this coefficient probably arises from the urinary excretion of organic compounds, which are the results of certain dietary substances undergoing conjugation in the liver to make them water-soluble. Phenolic substances are some of the most likely compounds in this category. These low digestible dry matter contents bear some similarity to organic matter digestibilities of 0.24-0.47 reported by Snider and Asplund (1974) for leaves of woody species eaten by deer. 2.3. Intake of browse by game animals To obtain acceptable assessments of intake certain species need to be selected for which measurements have been made and the values may be judged by comparison with corresponding data for domesticated animals. Ruminants species fall in this category and from now on discussion will centre on four well known species, i.e. eland (Taurotragus oryx), greater kudu (Tragelaphus strepsiceros), impala tiepyceros melampus) and common duiker (Sylvicapra grimmia). These ruminant species selected for discussion range from the largest antelope, i.e. the eland to one of the small species, the duiker. In between, the kudu has a weight about half that of the eland, while impala are approximately one-tenth of this weight. Mature weights of each species varies considerably in published reports [see review by Petersen and Casebeer (1971)] and the difference between males and females of the same species differs also. For the purpose of assessing the intake and energy needs in this review, the larger values have been chosen with a small difference only between the sexes. The appropriate weights that are used are shown in Table 4. Published data on dry matter intake are conveniently given as percentage of live weight (Owen-Smith, 1982). Nevertheless, it is generally accepted that intake is
Table 4 Approximate live weights (kg), dry matter intakes (kg day-‘) and derived ME intakes (MJ day-‘) of four ruminant species of adult wild ungulates eating browse with an ME value of 9.0 MJ kg-’ DM Species
Live weight
Dry matter intake
ME intake
Common duiker Gylvicapra grimmia)
20
0.75
6.75
Impala ( Aepyceros melampus) Greater kudu
50
1.50
13.50
250
5.00
45.00
500
8.50
76.50
(Tragelophus strepsiceros)
Eland (Taurotragus OQJX)
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related to metabolic body weight (W”.75) which means that the percentage is smaller for larger than it is for smaller animals. For ruminant animals, it is well known that there is a positive relationship between the digestibility of the diet and dry matter intake, except for highly digestible feeds when the effect of rumen fill is unlikely to be a major factor controlling intake. Such a positive relationship has been found by Pietersen and Meissner (1993) for free-ranging male impalas in South Africa. Using oesophageal fistula and collecting faeces in a bag, they found that organic matter digestibility varied between 0.40 and 0.70 and it was directly related to dry matter intakes ranging from 900 to 1900 g day-‘. Using these data the authors derived intakes of dry matter and of ME by male impala weighing 50 kg for diets ranging in organic matter digestibility from 0.45 to 0.65 and these results have been used in this review. For the four ruminant species being discussed, the likely dry matter intakes which are for medium quality diets with an ME value close to 9.0 MJ kg-’ DM are given in Table 4. To obtain the percentage for the common duiker, use has been made of the values published for ruminant species of a similar size (Arman and Hopcraft, 1975; Hoppe et al., 1977). If these dry matter intakes are accepted it is possible to calculate the daily intake of ME by making use of the ME values derived for high quality browse (Table 3). The corresponding ME intakes are shown in Table 4.
3. Nutrient requirements of game animals Only a limited amount of information has been published on the output of energy and of nutrients in the form of products or as a result of the animal’s metabolism, which may be used to derive nutrient requirements using a factorial approach (Robbins, 1983; Hudson and White, 1985). Any comprehensive study with this objective is formidable in size. The training and domestication of game animals are major challenges with all but a few species. A large number of species needs to be covered if the work is to be comprehensive, and for each species several physiological functions such as growth or lactation need to be examined. Such a matrix would require many years of work by several teams of researchers with access to relatively sophisticated facilities. Furthermore, if such work was done, there would be some scepticism about the applicability of the results to the natural or field situation. On the other hand, it can be argued that if we are to make greater and better use of game animals, a knowledge of their requirements is essential. At present, attempts to acquire this knowledge are almost entirely restricted to quantifying a practical situation in which a feed source can be assessed and its use over a period of time related to the number of game present and their physiological status. The data obtained have the advantage of being obtained from practical assessments in situations similar to those that occur naturally. However, their application is restricted to the particular circumstances in which they are measured.
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In such an uncertain situation regarding the requirements of game animals, a realistic approach is to consider the basic energy needs (Blaxter, 1962). Such measurements have been carried out with one of the species under consideration, the eland (Rogerson, 1968). Rogerson measured the fasting metabolism of eland in Kenya and found it to be 0.46 MJ kg-’ W”.73. This value was about 30% greater than that of cattle, but it is consistent with determinations made elsewhere on other species of wild ruminants (Topps, 1975; Semiadi et al., 1995). Robbins (1983) has stated that wild ungulates often have a higher fasting metabolic rate than that predicted by the interspecies mean (Kleiber, 1961) but the determined value may be affected by the animal’s psychological state and activity. Corresponding data for the other three species selected for discussion in this review have not been published. However, it is possible that the value per unit of metabolic weight obtained with eland may apply to the other three species. Alternatively, they may have a lower metabolism close to that given by the interspecies mean. It was decided to use both relationships in this analysis. The two sets of fasting metabolism values in MJ day-’ for the four species are shown in Table 6. Measurement of fasting metabolism places severe restriction on the movement of the animal. Game species which are free-ranging exhibit a substantial amount of physical activity which will lead to an expenditure of energy. The amount of activity and the energy cost of different forms have been determined or derived for a few species of wild ungulates (Fancy and White, 1985) and these are used in this review. There is no absolute certainty that they apply to the four species being reviewed, however, no other data are available to argue otherwise. The extent of each activity per day is likely to vary between species and between animals within a species. However, for the purpose of deriving energy requirements in this review, average values have been chosen for each of the four species. Four different forms of activity, one of which is additional, need to be considered to obtain an increment of energy expenditure for activity over and above fasting metabolism. These are: extra standing; locomotion; eating; and ruminating. The increment for standing over lying has been measured for eight temperate wild ungulates and found to range from 10 to 35% (Fancy and White, 1985). A value of 10% has been chosen together with an extra time of 6 h which takes account of foraging activity and at times the need to stay alert. Values for locomotion have been calculated using the oxygen cost in ml g -’ live weight per km walked of 0.533 W-o.316 (Fancy and White, 1985). Th is assumes that there is no vertical movement and that the mean speed is 3.6 km h-‘. A relatively small distance of 5 km day-’ has been applied to all four species. This may be considered a conservative estimate especially for the two larger species, but wild animals have home territories and if food is abundant they are reluctant to move far unless they are forced by predators. The energy cost of browsing has been determined by Pauls et al. (1981) for Wapiti (Ceruus eluphus) and found to be 4.6 kJ h-r kg- ’ W”.75. This value has been applied to the four species under study. The time spent browsing has been measured by Jarman and Jarman (1973) for impala in the Serengeti and found to range from 8.0 to 10.7 h in a 24-h period. A value of 8 h has been applied to this
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species. For the other three species relationships reviewed by Bunnell and Gillingham (1985) have been used to obtain times spent browsing. They show that foraging time per unit of body weight is greater with smaller animals but there is an overall positive relationship between time spent foraging and metabolic body weight. For rumination, Fancy and White (1985) have concluded that the increase is approximately 2% in metabolic rate and an average time of 8 h day-’ has been applied to all four species. The calculated values for all forms of activity and of the total for each of the four species are given in Table 5. The activity increment in relation to fasting metabolism is large (between 19.1 and 42.0%) which is consistent with that derived for cattle and sheep kept under extensive grazing conditions. To obtain the energy required for maintenance expressed as metabolisable energy, the energy lost as fasting metabolism and that expended in physical activity are added, and an appropriate efficiency factor used to convert the sum to metabolisable energy bearing in mind the quality of the diet. Earlier it was concluded that browse at its best is likely to have an ME value close to 9.0 MJ kg-’ DM, for which a metabolisability of about 0.5 can be applied. The efficiency factor
Table 5 Energy costs (MJ day-’ 1 of physical activity in four ruminant species of wild ungulates Species
Common duiker Impala Greater kudu Eland
Locomotion
Standing a
b
0.07 0.14 0.46 0.77
0.11 0.22 0.73 1.23
Eating
0.66 1.27 3.87 6.19
0.04 0.56 2.89 5.83
Ruminating
Total
a
b
a
b
0.02 0.04 0.12 2.21
0.03 0.06 0.20 0.33
0.79 2.01 7.34 13.00
0.84 2.11 7.69 13.58
_
aRelated to fasting metabolism of 293 kJ kg-’ W”.75. bRelated to fasting metabolism of 465 kJ kg-’ W”.75.
Table 6 Fasting metabolism, energy expended in physical activity and energy requirements for maintenance (MJ day-’ ) of four ruminant game animals eating browse Species
Common duiker Impala Greater kudu Eland
Fasting metabolism
Activity increment
ME’ requirement for maintenance
a
b
a
b
a
b
2.77 5.51 18.43 30.97
4.40 8.74 29.25 49.15
0.79 2.01 7.34 13.00
0.84 2.11 7.69 13.58
5.3 11.1 38.2 65.1
7.8 16.1 54.7 92.9
aBased on fasting metabolism of 293 kJ kg-’ W”.“. bBased on fasting metabolism of 465 kJ kgg’ W’.“. ‘Using an efficiency factor (km) = 0.675 for browse with an ME value of 9.0 MJ kgg’ DM.
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that is used for this metabolisability is 0.675 (McDonald et al., 1995) and when it is applied the maintenance requirements shown in Table 6 are obtained. When these values are compared with those in Table 4 for ME intakes, the intakes are either greater or less than the energy requirements for maintenance depending on the values used for fasting metabolism. The lower set of values for maintenance are little less than those proposed by Meissner (1982) for the three larger species. It is possible that the actual requirements for maintenance for each of the four species may be between the two sets of values given in Table 6. If so the energy obtained from medium quality browse may be sufficient to meet the animal’s requirements for maintenance only. The energy content and dry matter intake of white-tailed deer (Dorcelaphus virginianus) given winter browse diets have been studied by Gray and Serve110 (1995) in North America. The digestible energy (DE) content of the browse diets ranged from 8.15 to 9.99 MJ kg-’ DM and it was found that both DMI and DE1 were positively and linearly related to dietary energy value. However, it was deduced that the intake of DE from the browse diets provided only 30-88% of energy requirements for maintenance. For browse with a DE content of 9.2 MJ kg-’ DM, which is the reputed minimum for maintenance, intake was only 63% of maintenance.
4. Conclusion It would be foolhardy to conclude from this analysis that wild ungulates eating browse obtain only enough energy to meet their maintenance requirements. The species that are considered are known to be productive in terms of reproduction and growth but not at high levels (Petersen and Casebeer, 1971). Furthermore, in the analysis certain values and relationships were applied which may not be the best for tropical ruminants. However, it does indicate that browse at certain times of the year for some ruminant species of wild ungulates may provide energy for maintenance needs only. It is interesting to note that Gwen-Smith and Novellie (1982) and Gwen-Smith and Cooper (1989) have suggested that for large browsing ruminants, energy rather than protein is the most likely limiting nutrient during critical times of the year. Although the crude protein content of browse is relatively high, the extent of its degradability in the rumen may be low due to the presence of interfering substances such as tannins. If so the yield of microbial protein may be less than the amount needed for maintenance. The digestion of undegradable protein in the small intestine then becomes important and such measurements on samples of browse are advocated. In addition the ability of the animal to recycle urea to the rumen becomes a key factor. To obtain a better understanding of nutrient needs of wild ungulates in relation to the supply of nutrients from species of browse, the establishment of models of energy and protein systems is likely to be useful. Two such models, that of Swift (1983) and that of Illius and Jessop (1995) may be useful as a basis for the evolution of these models. They would allow the sensitivity of certain factors or components to be tested. For example a small increase in rumen degradability or
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digestibility in the whole gut may lead to a greater increase in intake and an appreciable improvement in plane of nutrition. Until such work is carried out it may be shrewd to think of browse providing only modest amounts of energy and protein to ruminant species of wild ungulates. Work is needed to distinguish those shrubs and trees that may be better than others in providing forage that is well degraded and digested in the gut of ruminants.
References Arman, P., Hopcraft, D., 1975. Nutritional studies in East African herbivores. Digestibilities of dry matter, crude fibre and crude protein in antelope, cattle and sheep. Br. J. Nutr. 33, 255-264. Baloyi, J.J., Ngongoni, N.T., Topps, J.H., Ndlovu, P., 1997. Chemical composition and degradability of Brachysfigia spicifonis (Msasa) leaves and twigs harvested over four months from three sites. Anim. Feed. Sci. Tech. 68, 00. Barry, T.N., Manley, T.R., 1984. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep: 2 Quantitative digestion of carbohydrates and proteins, Br. J. Nutr. 51, 493-504. Blaxter, K.L. 1962. The Energy Metabolism of Ruminants, Hutchinson, London. Bunnell, F.L., Gillingham, M.P., 1985. Foraging behaviour: Dynamics of dining out. In: Hudson, R.J., White, R.G. (Eds.), Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL, pp. 53-79. Dougall, H.W., Drysdale, V.M., Glover, P.E., 1964. The chemical composition of Kenya browse and pasture herbage. East Afr. Wildl. J. 2, 86-121. Dube, J.S., 1993. Nutritive value of four species of browse preferred by indigenous goats in a redsoil thornveld in Southern Zimbabwe. M.Phil Dissertation, University of Zimbabwe, Harare. Fancy, S.G., White, R.G., 1985. Incremental cost of activity. In: Hudson, R.J., White, R.G. (Eds.), Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL, pp. 143-159. Goering, H.K., Van So&t, P.J., 1970. Forage fibre analysis: apparatus, reagents, procedures and some applications. Agricultural Handbook 379, ARS, USDA, Washington, DC. Gray, P.B., Servello, F.A., 1995. Energy intake relationships for white-tailed deer on winter browse diets. J. Wildl. Manage. 59, 147-152. Hall-Martin, A.J., Erasmus, T., Botha, B.P., 1982. Seasonal variation of diet and faeces composition of black rhinoceros Diceros bicornis in the Addo Elephant National Park. Koedoe 25, 63-82. Hoppe, P.P., Quortrup, S.A., Woodford, M.H., 1977. Rumen fermentation and food selection in East African sheep, goats, Thomson’s gazelle, Grant’s gazelle and impala. J. Agric. Sci. (Camb.) 89, 129-135. Hudson, R.J., White, R.G., (Eds.), 1985. Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL. Illius, A.W., Jessop, N.S., 1995. Modeling metabolic costs of allelochemical ingestion by foraging herbivores. J. Chem. Ecol. 21, 693-719. Jarman, M.V., Jarman, P.J., 1973. Daily activity of impala. East Afr. Wildl. J. 11, 75-92. Kleiber, M., 1961. The Fire of Life, Wiley, New York. Le Houerou, H.N., 1980. Browse in Africa. The current state of knowledge. International Livestock Centre for Africa, Addis Ababa, Ethiopia. McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., Morgan, C.A., 1995. Animal Nutrition, 5th ed. Longman Scientific and Technical, Harlow, Essex. Meissner, H.H., 1982. Theory and application of a method to calculate forage intake of wild Southern African ungulates for purposes of estimating carrying capacity. South Afr. J. Wildl. Res. 12, 41-47. Mueller-Harvey, I., McAllan, A.B., 1992. Tannins - their biochemistry and nutritional properties. Adv. PI. Cell. Bio. Biol. 1, 151-217. Owen-Smith, R.N., Novellie, P., 1982. What should a clever ungulate eat? Am. Nat. 119, 151-178.
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J.H. Topps /Animal Feed Science Technology 69 (1997) 143-154
Gwen-Smith, N., 1982. Factors influencing the consumption of plant products by large herbivores. In: Huntley, B.J., Walker, B.H. (Eds.), Ecological Studies, Vol. 42, Ecology of Tropical Savannas. Springer-Verlag, Berlin, pp. 359-404. Gwen-Smith, R.N., Cooper, S.M., 1989. Nutritional ecology of a browsing ruminant, the kudu (Tragelaphus strepsiceros) through the seasonal cycle. J. Zool. Lond. 219, 29-43. Pauls, R.W., Hudson, R.J., Sylven, S., 1981. Energy expenditure of free-ranging wapiti. Univ. Alberta Feeders Day Rep. 60,87-91. Pellew, R.A., 1980. The production and consumption of Acacia browse and its potential for animal protein production. In: Le HouCrou, H.N. (Ed.), Browse in Africa: The Current State of Knowledge. International Livestock Centre for Africa, Addis Ababa, Ethiopia, pp. 223-231. Petersen, J.C.B., Casebeer, R.L., 1971. A bibliography relating to the ecology and energetics of East African large mammals. East Afr. Wildl. J. 9, l-23. Pietersen, L.M., Meissner, H.H., 1993. Food selection and intake by male impalas in the Timbavati area. South Afr. J. Wild]. Res. 23, 6-11. Rees, W.A., 1974. Preliminary studies into bush utilisation by cattle in Zambia. J. Appl. Ecol 11, 207-214. Robbins, CT., 1983. Wildlife Feeding and Nutrition. Academic Press, Orlando, USA. Rogerson, A., 1968. Energy utilization by the eland and wildebeest. Symp. Zool. Sot. Lond. 21, 153-161. Semiadi, G., Barry, T.N., Muir, P.D., 1995. Comparison of seasonal patterns of growth, voluntary feed intake and plasma hormone concentrations in young sambar deer (Cervus unicolor) and red deer (Cetvus elaphus). J. Agric. Sci. (Camb.) 125, 109-124. Snider, C.C., Asplund, J.M., 1974. In vitro digestibility of deer foods from the Missouri Ozarks. J. Wildl. Manage. 38,20-31. Swift, D.M., 1983. A simulation model of energy and nitrogen balance for free ranging ruminants. J. Wildl. Manage. 47, 620-631. Topps, J.H., 1975. Behavioural and physiological adaptation of wild ruminants and their potential for meat production. Proc. Nutr. Sot. 34, 85-93. White, J., 1995. The wildlife producers. In: Holness, D.H. (Ed.), Proceedings of Livestock Production Symposium, Harare, 23-24 November 1994. Harare, Zimbabwe, Zimbabwe Society for Animal Production, pp. 81-84.
Animal Feed Science Technology 69 (1997) 143-154
Nutritive value of indigenous browse in Africa in relation to the needs of wild ungulates J.H. Topps* Deparimentof Agriculture,University of Aberdeen, King Street,AberdeenAB24 SUD, UK
Abstract From a review of published information on the nutritive value of indigenous browse in Africa, the intake of ruminant species of wild ungulates and the energy requirements for maintenance of these animals, an analysis has been carried out to assess the supply of energy and protein from browse in relation to meeting requirements. Although there are a large number of data giving chemical composition of browse, there is relatively little information on digestibility and energy value. Results on intake and energy requirements have been reported for a few species of wild ungulates and these have been used as such or formed the basis of derived values for other species. The analysis indicates that for four species of wild ungulates, differing in size from 20 to 500 kg, the intake of metabolisable energy may be 12-27% greater than or substantially less than the amount required for maintenance. The difference arises from the choice of values for fasting metabolism. The establishment of models of energy and protein systems, together with more measurements on the nutritive value of indigenous browse are advocated in order to obtain a better knowledge of the nutrient needs and productivity of wild ungulates that utilize indigenous browse. 0 1997 Elsevier Science B.V. Keywords: Wild ungulates;
Ruminants;
Browse; Intake; Energy requirements
1. Introduction Indigenous browse is the main source of forage (leaves and twigs) for several species of wild ungulates in Africa. In addition it makes an important contribution *Tel.: f44 1224 318685. 0377-8401/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PZZ SO377-8401(97)00102-8
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to the intake of food by other wildlife species, and goats and cattle have been known to browse during a drought when there is almost a complete absence of grazing. There are several hundred species of trees and shrubs which are known to be browsed by domestic livestock or wild ungulates in Africa (Le HouCrou, 1980) and a large number have been studied as an animal feed source in one or more locations. Valuable information has been accumulated on chemical composition as a guide to nutritive value, and in recent years, on the presence of secondary plant compounds which may act as anti-nutritional factors. From these data it has been concluded that in all the drier parts of Africa, the nutritive value of browse appears to be better than that of the native grasses throughout the year, except for the early season of grass growth. However, the presence of secondary plant compounds, especially those referred to as tannins, casts some doubt as to the availability of nutrients in browse (Barry and Manley, 1984) and to the validity of this general conclusion. In Zimbabwe there is increasing interest in the ranching of game animals (White, 1995). Furthermore, most of the countries in Southern Africa and in East Africa are blessed with a diverse range of these species, which has an enormous intrinsic and commercial value. Any reduction in this resource would erode the capacity within Southern Africa of making use of dry, fragile areas and of earning foreign exchange. Indigenous browse, therefore, is an essential component of many multi-species systems and the extent to which it is used to sustain animals that browse needs to be known. This paper reviews knowledge on the nutritive value of indigenous browse and attempts to relate it to the needs of ruminant species of wild ungulates. In establishing this relationship, three separate but related pieces of information about these species are needed. These are: . the nutritive value of browse consumed; . the intake of browse and the sources of variation; . the energy and protein requirements for maintenance. There is a lack of information in all three areas, so some use has been made of the data in the publications edited by Le HouCrou (1980) and Hudson and White (1985) and in the book written by Robbins (1983).
2. Nutritive value of browse consumed by game animals 2.1. Chemical composition There are a large amount of data on the chemical composition of browse in Africa (Le HouCrou, 1980). Much of it has been obtained using the proximate analysis of feeds which fractionates the dry matter into the following constituents: 1. Crude protein 2. Ash
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3. Crude fibre 4. Ether extract 5. N-free extractive This scheme provides only a small amount of useful data, i.e. crude protein and ash contents. Crude fibre is not a measure of the fibrosity of the plant material since it contains only some of the cellulose and lignin, the remainder being in the N-free extract which is obtained by difference, while the ether extract is likely to contain many other compounds in addition to true fat. An alternative approach is the Van So&t analysis of cell wall and its constituents, which gives a useful assessment of the total fibre in the plant and its composition (Gohing and Van So&t, 1970). The large number of results for crude protein content show that browse has a medium to high value. For example, Dougall et al. (1964) published values for 234 samples of browse collected in Kenya, of which 64 were from legume species (Table 1). Mean values for legume and non-legume species were 148 and 127 g kg- ’ DM, respectively with all but a few contents above 70 g kg- ’ DM. This indicates that protein in browse is less subject to seasonal changes than that in grasses which has been shown by Dube (1993) for four browse species in Zimbabwe. Very little information has been published on the availability of the protein to animals. Recent work in Zimbabwe (Baloyi et al., 1997) shows that the rumen degradability of protein in Brachystegiaspic$omis is in the range 0.4-0.5, and that tannins are present. It is possible that the presence of tannins impaired the degradation of protein. Ash content is inversely related to the total organic matter in the plant. Some species of browse have an average or low content of ash which means that organic matter content and gross energy value are higher in browse than that normally ascribed to plant material (Table 1). Values for detergent fibres in browse are often less than those for the surrounding grass vegetation especially during the dry season. A selection of values for Acacia species published by Pellew (1980) are shown in Table 2. Similar values were reported for seven browse species collected in South Africa by Hall-Martin et Table 1 Chemical composition (g kg-’ dry matter of species of browse harvested in Kenya (after Dougall et al., 1964)
Crude protein Mean Range Ash Mean Range
Legume n = 64
Non-legume n = 170
148 28-429
127 (n = 234)
86 30-267
117 (n = 234)
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al. (1982). They are difficult to interpret in terms of providing an indication of digestibility and energy value. While the content of neutral detergent fibre is low, which may indicate a high content of highly digestible cell content the lignin contents are high. The latter may be interpreted as an indication of heavily lignified and very indigestible cell wall. However, the values for neutral detergent fibre may underestimate the total content of cell wall since certain constituents such as pectin are soluble in the detergent solution. Furthermore, the acid detergent lignin fraction may not be an appropriate measure of lignin in browse due to the formation of artifacts arising from reactions of tannins with protein and carbohydrates (Mueller-Harvey and McAllan, 1992). Table 2 Chemical composition (g kg-’ of dry matter) of Acacia browse in the Serengeti Game Park (after Pellew, 1980) Crude protein
Neutral detergent fibre
Acid detergent fibre
Acid detergent lignin
A. tortilis New shoots Young shoots New leaves Old leaves
205 103 210 1.53
507 600 445 399
383 461 235 245
162 205 132 150
A. Senegal New shoots Young shoots New leaves Old leaves
336 141 329 219
479 603 401 448
290 431 203 248
111 222 89 103
A. xanthophloea New shoots Young shoots New leaves Old leaves
182 100 232 182
546 610 499 461
331 452 248 314
126 179 149 141
A. ho&ii New shoots Young shoots New leaves Old leaves
180 105 194 153
372 511 284 391
269 380 139 151
83 151 70 86
A. clavigera New shoots Young shoots New leaves Old leaves
242 102 202 126
452 492 399 353
268 359 228 213
102 143 142 106
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2.2. Digestibilityand energy value Relatively few values for digestibility are reported in the literature. Those given by Rees (1974) for Northern Zambia some of which are summarised in Table 3, are relevant to Zimbabwe. The values are for digestible dry matter content rather than a digestibility coefficient, but they show that 60% or less of the feed is digested. Very low values are obtained for old growth. A small proportion (approx. 5%) of the digestible DM will be in the form of ash so the digestible organic matter content will be lower. In ruminant nutrition, such values may be converted to energy values by the application of conversion factors (McDonald et al., 1995). Digestible organic matter in roughage and forages has an energy value close to 19.5 MJ kg-‘. For ruminant livestock, digestible energy (DE) may be converted to metabolisable energy (ME) by multiplying by 0.82, since the combined losses of
Table 3 Crude protein (CP) and digestible dry matter (DDM) contents (g kg -’ DM) of browse eaten by cattle in a Miombo region in Northern Zambia, together with approximate derived metabohsable energy (ME) values (MJ kg-’ DM) (adapted from Rees, 1974) Species
Growth
August
October
CP
DDM
ME
CP
DDM
ME
Baphia beguatii
New
281
615
9.0
235
571
8.4
Brachystegia glabem’ma
Old New
96 -
338 -
4.9 -
120
344
5.0
Old New
106 -
596 -
8.7 -
183
521
Old New
102 -
547
8.0
Old New
76
577
Old New
111 112
548 610
8.0 8.9
Old New
77
557
8.1
Old New
91 113
382 459
Old New
89 119
515 549
B. spicifonnis
B. utilis
Diplorhynchus condylocarpon
Julbernardiapaniculata
Mono&
spp.
Ochthocosmus lemaireanus
Uapaca nitida
-
7.6 -
178
464
6.8 -
8.4 152
627
9.2
113
574
8.4
123
418
6.1
5.6 6.7
153
664
9.7
7.5 8.0
189
646
9.5
-
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energy in urine and in methane are 18% of DE for many feeds. However, Robbins (1983) has listed values for this coefficient for wild ruminants given either deciduous or evergreen browse in temperate regions. The values range from 0.76 to 0.83 with a mean of 0.79 which is used, along with 19.5 MJ kg-’ to derive the ME values given in Table 3. The lower value of this coefficient probably arises from the urinary excretion of organic compounds, which are the results of certain dietary substances undergoing conjugation in the liver to make them water-soluble. Phenolic substances are some of the most likely compounds in this category. These low digestible dry matter contents bear some similarity to organic matter digestibilities of 0.24-0.47 reported by Snider and Asplund (1974) for leaves of woody species eaten by deer. 2.3. Intake of browse by game animals To obtain acceptable assessments of intake certain species need to be selected for which measurements have been made and the values may be judged by comparison with corresponding data for domesticated animals. Ruminants species fall in this category and from now on discussion will centre on four well known species, i.e. eland (Taurotragus oryx), greater kudu (Tragelaphus strepsiceros), impala tiepyceros melampus) and common duiker (Sylvicapra grimmia). These ruminant species selected for discussion range from the largest antelope, i.e. the eland to one of the small species, the duiker. In between, the kudu has a weight about half that of the eland, while impala are approximately one-tenth of this weight. Mature weights of each species varies considerably in published reports [see review by Petersen and Casebeer (1971)] and the difference between males and females of the same species differs also. For the purpose of assessing the intake and energy needs in this review, the larger values have been chosen with a small difference only between the sexes. The appropriate weights that are used are shown in Table 4. Published data on dry matter intake are conveniently given as percentage of live weight (Owen-Smith, 1982). Nevertheless, it is generally accepted that intake is
Table 4 Approximate live weights (kg), dry matter intakes (kg day-‘) and derived ME intakes (MJ day-‘) of four ruminant species of adult wild ungulates eating browse with an ME value of 9.0 MJ kg-’ DM Species
Live weight
Dry matter intake
ME intake
Common duiker Gylvicapra grimmia)
20
0.75
6.75
Impala ( Aepyceros melampus) Greater kudu
50
1.50
13.50
250
5.00
45.00
500
8.50
76.50
(Tragelophus strepsiceros)
Eland (Taurotragus OQJX)
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related to metabolic body weight (W”.75) which means that the percentage is smaller for larger than it is for smaller animals. For ruminant animals, it is well known that there is a positive relationship between the digestibility of the diet and dry matter intake, except for highly digestible feeds when the effect of rumen fill is unlikely to be a major factor controlling intake. Such a positive relationship has been found by Pietersen and Meissner (1993) for free-ranging male impalas in South Africa. Using oesophageal fistula and collecting faeces in a bag, they found that organic matter digestibility varied between 0.40 and 0.70 and it was directly related to dry matter intakes ranging from 900 to 1900 g day-‘. Using these data the authors derived intakes of dry matter and of ME by male impala weighing 50 kg for diets ranging in organic matter digestibility from 0.45 to 0.65 and these results have been used in this review. For the four ruminant species being discussed, the likely dry matter intakes which are for medium quality diets with an ME value close to 9.0 MJ kg-’ DM are given in Table 4. To obtain the percentage for the common duiker, use has been made of the values published for ruminant species of a similar size (Arman and Hopcraft, 1975; Hoppe et al., 1977). If these dry matter intakes are accepted it is possible to calculate the daily intake of ME by making use of the ME values derived for high quality browse (Table 3). The corresponding ME intakes are shown in Table 4.
3. Nutrient requirements of game animals Only a limited amount of information has been published on the output of energy and of nutrients in the form of products or as a result of the animal’s metabolism, which may be used to derive nutrient requirements using a factorial approach (Robbins, 1983; Hudson and White, 1985). Any comprehensive study with this objective is formidable in size. The training and domestication of game animals are major challenges with all but a few species. A large number of species needs to be covered if the work is to be comprehensive, and for each species several physiological functions such as growth or lactation need to be examined. Such a matrix would require many years of work by several teams of researchers with access to relatively sophisticated facilities. Furthermore, if such work was done, there would be some scepticism about the applicability of the results to the natural or field situation. On the other hand, it can be argued that if we are to make greater and better use of game animals, a knowledge of their requirements is essential. At present, attempts to acquire this knowledge are almost entirely restricted to quantifying a practical situation in which a feed source can be assessed and its use over a period of time related to the number of game present and their physiological status. The data obtained have the advantage of being obtained from practical assessments in situations similar to those that occur naturally. However, their application is restricted to the particular circumstances in which they are measured.
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In such an uncertain situation regarding the requirements of game animals, a realistic approach is to consider the basic energy needs (Blaxter, 1962). Such measurements have been carried out with one of the species under consideration, the eland (Rogerson, 1968). Rogerson measured the fasting metabolism of eland in Kenya and found it to be 0.46 MJ kg-’ W”.73. This value was about 30% greater than that of cattle, but it is consistent with determinations made elsewhere on other species of wild ruminants (Topps, 1975; Semiadi et al., 1995). Robbins (1983) has stated that wild ungulates often have a higher fasting metabolic rate than that predicted by the interspecies mean (Kleiber, 1961) but the determined value may be affected by the animal’s psychological state and activity. Corresponding data for the other three species selected for discussion in this review have not been published. However, it is possible that the value per unit of metabolic weight obtained with eland may apply to the other three species. Alternatively, they may have a lower metabolism close to that given by the interspecies mean. It was decided to use both relationships in this analysis. The two sets of fasting metabolism values in MJ day-’ for the four species are shown in Table 6. Measurement of fasting metabolism places severe restriction on the movement of the animal. Game species which are free-ranging exhibit a substantial amount of physical activity which will lead to an expenditure of energy. The amount of activity and the energy cost of different forms have been determined or derived for a few species of wild ungulates (Fancy and White, 1985) and these are used in this review. There is no absolute certainty that they apply to the four species being reviewed, however, no other data are available to argue otherwise. The extent of each activity per day is likely to vary between species and between animals within a species. However, for the purpose of deriving energy requirements in this review, average values have been chosen for each of the four species. Four different forms of activity, one of which is additional, need to be considered to obtain an increment of energy expenditure for activity over and above fasting metabolism. These are: extra standing; locomotion; eating; and ruminating. The increment for standing over lying has been measured for eight temperate wild ungulates and found to range from 10 to 35% (Fancy and White, 1985). A value of 10% has been chosen together with an extra time of 6 h which takes account of foraging activity and at times the need to stay alert. Values for locomotion have been calculated using the oxygen cost in ml g -’ live weight per km walked of 0.533 W-o.316 (Fancy and White, 1985). Th is assumes that there is no vertical movement and that the mean speed is 3.6 km h-‘. A relatively small distance of 5 km day-’ has been applied to all four species. This may be considered a conservative estimate especially for the two larger species, but wild animals have home territories and if food is abundant they are reluctant to move far unless they are forced by predators. The energy cost of browsing has been determined by Pauls et al. (1981) for Wapiti (Ceruus eluphus) and found to be 4.6 kJ h-r kg- ’ W”.75. This value has been applied to the four species under study. The time spent browsing has been measured by Jarman and Jarman (1973) for impala in the Serengeti and found to range from 8.0 to 10.7 h in a 24-h period. A value of 8 h has been applied to this
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species. For the other three species relationships reviewed by Bunnell and Gillingham (1985) have been used to obtain times spent browsing. They show that foraging time per unit of body weight is greater with smaller animals but there is an overall positive relationship between time spent foraging and metabolic body weight. For rumination, Fancy and White (1985) have concluded that the increase is approximately 2% in metabolic rate and an average time of 8 h day-’ has been applied to all four species. The calculated values for all forms of activity and of the total for each of the four species are given in Table 5. The activity increment in relation to fasting metabolism is large (between 19.1 and 42.0%) which is consistent with that derived for cattle and sheep kept under extensive grazing conditions. To obtain the energy required for maintenance expressed as metabolisable energy, the energy lost as fasting metabolism and that expended in physical activity are added, and an appropriate efficiency factor used to convert the sum to metabolisable energy bearing in mind the quality of the diet. Earlier it was concluded that browse at its best is likely to have an ME value close to 9.0 MJ kg-’ DM, for which a metabolisability of about 0.5 can be applied. The efficiency factor
Table 5 Energy costs (MJ day-’ 1 of physical activity in four ruminant species of wild ungulates Species
Common duiker Impala Greater kudu Eland
Locomotion
Standing a
b
0.07 0.14 0.46 0.77
0.11 0.22 0.73 1.23
Eating
0.66 1.27 3.87 6.19
0.04 0.56 2.89 5.83
Ruminating
Total
a
b
a
b
0.02 0.04 0.12 2.21
0.03 0.06 0.20 0.33
0.79 2.01 7.34 13.00
0.84 2.11 7.69 13.58
_
aRelated to fasting metabolism of 293 kJ kg-’ W”.75. bRelated to fasting metabolism of 465 kJ kg-’ W”.75.
Table 6 Fasting metabolism, energy expended in physical activity and energy requirements for maintenance (MJ day-’ ) of four ruminant game animals eating browse Species
Common duiker Impala Greater kudu Eland
Fasting metabolism
Activity increment
ME’ requirement for maintenance
a
b
a
b
a
b
2.77 5.51 18.43 30.97
4.40 8.74 29.25 49.15
0.79 2.01 7.34 13.00
0.84 2.11 7.69 13.58
5.3 11.1 38.2 65.1
7.8 16.1 54.7 92.9
aBased on fasting metabolism of 293 kJ kg-’ W”.“. bBased on fasting metabolism of 465 kJ kgg’ W’.“. ‘Using an efficiency factor (km) = 0.675 for browse with an ME value of 9.0 MJ kgg’ DM.
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that is used for this metabolisability is 0.675 (McDonald et al., 1995) and when it is applied the maintenance requirements shown in Table 6 are obtained. When these values are compared with those in Table 4 for ME intakes, the intakes are either greater or less than the energy requirements for maintenance depending on the values used for fasting metabolism. The lower set of values for maintenance are little less than those proposed by Meissner (1982) for the three larger species. It is possible that the actual requirements for maintenance for each of the four species may be between the two sets of values given in Table 6. If so the energy obtained from medium quality browse may be sufficient to meet the animal’s requirements for maintenance only. The energy content and dry matter intake of white-tailed deer (Dorcelaphus virginianus) given winter browse diets have been studied by Gray and Serve110 (1995) in North America. The digestible energy (DE) content of the browse diets ranged from 8.15 to 9.99 MJ kg-’ DM and it was found that both DMI and DE1 were positively and linearly related to dietary energy value. However, it was deduced that the intake of DE from the browse diets provided only 30-88% of energy requirements for maintenance. For browse with a DE content of 9.2 MJ kg-’ DM, which is the reputed minimum for maintenance, intake was only 63% of maintenance.
4. Conclusion It would be foolhardy to conclude from this analysis that wild ungulates eating browse obtain only enough energy to meet their maintenance requirements. The species that are considered are known to be productive in terms of reproduction and growth but not at high levels (Petersen and Casebeer, 1971). Furthermore, in the analysis certain values and relationships were applied which may not be the best for tropical ruminants. However, it does indicate that browse at certain times of the year for some ruminant species of wild ungulates may provide energy for maintenance needs only. It is interesting to note that Gwen-Smith and Novellie (1982) and Gwen-Smith and Cooper (1989) have suggested that for large browsing ruminants, energy rather than protein is the most likely limiting nutrient during critical times of the year. Although the crude protein content of browse is relatively high, the extent of its degradability in the rumen may be low due to the presence of interfering substances such as tannins. If so the yield of microbial protein may be less than the amount needed for maintenance. The digestion of undegradable protein in the small intestine then becomes important and such measurements on samples of browse are advocated. In addition the ability of the animal to recycle urea to the rumen becomes a key factor. To obtain a better understanding of nutrient needs of wild ungulates in relation to the supply of nutrients from species of browse, the establishment of models of energy and protein systems is likely to be useful. Two such models, that of Swift (1983) and that of Illius and Jessop (1995) may be useful as a basis for the evolution of these models. They would allow the sensitivity of certain factors or components to be tested. For example a small increase in rumen degradability or
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digestibility in the whole gut may lead to a greater increase in intake and an appreciable improvement in plane of nutrition. Until such work is carried out it may be shrewd to think of browse providing only modest amounts of energy and protein to ruminant species of wild ungulates. Work is needed to distinguish those shrubs and trees that may be better than others in providing forage that is well degraded and digested in the gut of ruminants.
References Arman, P., Hopcraft, D., 1975. Nutritional studies in East African herbivores. Digestibilities of dry matter, crude fibre and crude protein in antelope, cattle and sheep. Br. J. Nutr. 33, 255-264. Baloyi, J.J., Ngongoni, N.T., Topps, J.H., Ndlovu, P., 1997. Chemical composition and degradability of Brachysfigia spicifonis (Msasa) leaves and twigs harvested over four months from three sites. Anim. Feed. Sci. Tech. 68, 00. Barry, T.N., Manley, T.R., 1984. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep: 2 Quantitative digestion of carbohydrates and proteins, Br. J. Nutr. 51, 493-504. Blaxter, K.L. 1962. The Energy Metabolism of Ruminants, Hutchinson, London. Bunnell, F.L., Gillingham, M.P., 1985. Foraging behaviour: Dynamics of dining out. In: Hudson, R.J., White, R.G. (Eds.), Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL, pp. 53-79. Dougall, H.W., Drysdale, V.M., Glover, P.E., 1964. The chemical composition of Kenya browse and pasture herbage. East Afr. Wildl. J. 2, 86-121. Dube, J.S., 1993. Nutritive value of four species of browse preferred by indigenous goats in a redsoil thornveld in Southern Zimbabwe. M.Phil Dissertation, University of Zimbabwe, Harare. Fancy, S.G., White, R.G., 1985. Incremental cost of activity. In: Hudson, R.J., White, R.G. (Eds.), Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL, pp. 143-159. Goering, H.K., Van So&t, P.J., 1970. Forage fibre analysis: apparatus, reagents, procedures and some applications. Agricultural Handbook 379, ARS, USDA, Washington, DC. Gray, P.B., Servello, F.A., 1995. Energy intake relationships for white-tailed deer on winter browse diets. J. Wildl. Manage. 59, 147-152. Hall-Martin, A.J., Erasmus, T., Botha, B.P., 1982. Seasonal variation of diet and faeces composition of black rhinoceros Diceros bicornis in the Addo Elephant National Park. Koedoe 25, 63-82. Hoppe, P.P., Quortrup, S.A., Woodford, M.H., 1977. Rumen fermentation and food selection in East African sheep, goats, Thomson’s gazelle, Grant’s gazelle and impala. J. Agric. Sci. (Camb.) 89, 129-135. Hudson, R.J., White, R.G., (Eds.), 1985. Bioenergetics of Wild Herbivores. CRC Press, Boca Raton, FL. Illius, A.W., Jessop, N.S., 1995. Modeling metabolic costs of allelochemical ingestion by foraging herbivores. J. Chem. Ecol. 21, 693-719. Jarman, M.V., Jarman, P.J., 1973. Daily activity of impala. East Afr. Wildl. J. 11, 75-92. Kleiber, M., 1961. The Fire of Life, Wiley, New York. Le Houerou, H.N., 1980. Browse in Africa. The current state of knowledge. International Livestock Centre for Africa, Addis Ababa, Ethiopia. McDonald, P., Edwards, R.A., Greenhalgh, J.F.D., Morgan, C.A., 1995. Animal Nutrition, 5th ed. Longman Scientific and Technical, Harlow, Essex. Meissner, H.H., 1982. Theory and application of a method to calculate forage intake of wild Southern African ungulates for purposes of estimating carrying capacity. South Afr. J. Wildl. Res. 12, 41-47. Mueller-Harvey, I., McAllan, A.B., 1992. Tannins - their biochemistry and nutritional properties. Adv. PI. Cell. Bio. Biol. 1, 151-217. Owen-Smith, R.N., Novellie, P., 1982. What should a clever ungulate eat? Am. Nat. 119, 151-178.
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Gwen-Smith, N., 1982. Factors influencing the consumption of plant products by large herbivores. In: Huntley, B.J., Walker, B.H. (Eds.), Ecological Studies, Vol. 42, Ecology of Tropical Savannas. Springer-Verlag, Berlin, pp. 359-404. Gwen-Smith, R.N., Cooper, S.M., 1989. Nutritional ecology of a browsing ruminant, the kudu (Tragelaphus strepsiceros) through the seasonal cycle. J. Zool. Lond. 219, 29-43. Pauls, R.W., Hudson, R.J., Sylven, S., 1981. Energy expenditure of free-ranging wapiti. Univ. Alberta Feeders Day Rep. 60,87-91. Pellew, R.A., 1980. The production and consumption of Acacia browse and its potential for animal protein production. In: Le HouCrou, H.N. (Ed.), Browse in Africa: The Current State of Knowledge. International Livestock Centre for Africa, Addis Ababa, Ethiopia, pp. 223-231. Petersen, J.C.B., Casebeer, R.L., 1971. A bibliography relating to the ecology and energetics of East African large mammals. East Afr. Wildl. J. 9, l-23. Pietersen, L.M., Meissner, H.H., 1993. Food selection and intake by male impalas in the Timbavati area. South Afr. J. Wild]. Res. 23, 6-11. Rees, W.A., 1974. Preliminary studies into bush utilisation by cattle in Zambia. J. Appl. Ecol 11, 207-214. Robbins, CT., 1983. Wildlife Feeding and Nutrition. Academic Press, Orlando, USA. Rogerson, A., 1968. Energy utilization by the eland and wildebeest. Symp. Zool. Sot. Lond. 21, 153-161. Semiadi, G., Barry, T.N., Muir, P.D., 1995. Comparison of seasonal patterns of growth, voluntary feed intake and plasma hormone concentrations in young sambar deer (Cervus unicolor) and red deer (Cetvus elaphus). J. Agric. Sci. (Camb.) 125, 109-124. Snider, C.C., Asplund, J.M., 1974. In vitro digestibility of deer foods from the Missouri Ozarks. J. Wildl. Manage. 38,20-31. Swift, D.M., 1983. A simulation model of energy and nitrogen balance for free ranging ruminants. J. Wildl. Manage. 47, 620-631. Topps, J.H., 1975. Behavioural and physiological adaptation of wild ruminants and their potential for meat production. Proc. Nutr. Sot. 34, 85-93. White, J., 1995. The wildlife producers. In: Holness, D.H. (Ed.), Proceedings of Livestock Production Symposium, Harare, 23-24 November 1994. Harare, Zimbabwe, Zimbabwe Society for Animal Production, pp. 81-84.