Canavalia ensiformis : a legume for the tropics.

Abstract

129 Canavalia ensiformis : A LEGUME FOR THE TROPICS R. M. DIXON*, A. ESCOBAR*, J. MONTILLA**, J. VIERA***, J. CARABANO**, M. MORA*, J. RISSO*, R. PARRA* and T. R. PRESTON**** Canavcdiu WUL&Hmid is a legume adapted to. a*: wide range of . environmental conditions, is easy to establish, and once- established can tolerate drought. It is a fast-growing plant capable, under favourable conditions, of producing high yields of both forage and grain although it can also produce moderate yields cm acid and nutrient-depleted soils. The whole plant typically contains 19% crude protein, 41% cell wall constituents and has an organic matter digestibility & vm of 64%) while the grain contains approximately 30% crude protein. Problems are encountered firstly because it is an kndeveloped** cultivar without selection for desirable characteristics, and secondly due to the presence of several toxic factors. These toxic factors are associated with reduced production or even death. For poultry autoclaving is an effective treatment, and up treated CtWLv~CL meal can be used withoutto 15% dietary inclusion of detrimental effects. Pigs appear to be more susceptible than poultry to the toxins, and no effective treatment has as yet been developed. Ruminants appear to have a lesser susceptibility, presumably due to detoxification during rumen fermentation. Incorporation of 20930% untreated CmUVuCr meal in the diet has been associated with some depression in dry matter and fibre digestibility and in growth rate* Canavalia grain plus pods has been used as a supplement to grazing cattle J and the chopped whole plant has been incorporated into mixed rations. Limited trials suggest that there is no adverse effect on reproduction. ccuzct~~ enbi&Mkb appears to have considerable potential as a tropical legume to provide both grain and forage of high protein and digestible energy #content. INTRODUCTION The potential of legumes to produce both grain and forage of high protein content for animal diets is widely accepted and exploited in temperate climates. However there has been correspondingly little development of suitable legume species in tropical climates. Two premising species to provide both grain and forage of high protein content are CUrzavtia enSi@lunib and cana&!& @k&Z, also known in the English speaking world by the c-on names jackbean, horsebean or gotani bean and swordbean respectively, They are of the Order Legwn&~U~ and Family PaIn origin &WtZvt&& enSi&ti is a New World plant, while puonucae. C~UUW~~ g&&&& is an Old World plant. Tha latter species is cultivated in the h&d tropics of Africa and Asia for human consuqtion but although Canwatia @&6orurttib was cultivated in ancient times (Canales 1976) it is little used now for h-an consumption (National Academy of Sciences 1981), * l Institute de ProducciGn Animal, Facultad de Agronda, Universidad Central de Venezuela, Maracay, Venezuela. ** Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Venezuela. *** Instituto de Gengtica, Facultad de Agronda, Universidad Central de Venezuela, Maracay, Venezuela **** Department of Tropical Veterinaq Science, James Cook University, Townsville, 4811, Australia. 130 produces pods up to 30 cm in length is a high-climbing twining perennial produces pods up to 40 cm long and 5 is that ccu~a~tddt Ud~Od seeds are c&& seeds are usually red. Cmavakx enSi@& is an erect shrubby annual 1-2 m tall, and and 3.5 cm wide. cWW&& g&&c& with runners as long as 10' m, and cm wide. A distinguishing feature usually white, and CC~~VUU g&- Most of the work in Venezuela has been with ctwtad,d enSi@&?&, and for this reason the following discussion will be limited to this species, although undoubtedly candt~d&t g&U&& also has considerable potential. Various aspects of the agronogny and use as animal feed of Ctt.nuvt@&t en&i@tm& have been reviewed recently by.Viera ti &. C1982), Mora & &. (1982) and Risso & &. (1982) l ADVANTAGES OF &UULvaRia endi@ti (.I.) Legume . The species is a legume and as such-has a high protein content fn both the foliage and the seed. Nodulation is frequently observed and Frederick (1978) has reported N fixation of 49 kg ha-1 crop-l, less than most other pulses. . (II) Adaptation. It is a legume witi adaptation to a wide variety of climatic conditions (National Academy of Sciences 1981). The species is suitable for temperatures ranging from the warmer parts of the temperate zone to hot tropical rainforest zones, with. a range in average tpmberature from Y4'C to 27'C. The leaves) but not the pods, are affected by frost. Rainfall may range from 700 mm to 4 200 mm, and having a deep root system the plant is able to survive sustaineddryperiods once it.% established. ' The species is able to tolerate a wide range of soil textures and soil fertility, and is the only pulse that grows well on highly-leached, nutrient-depleted tropical lowland soils. It grows well on acid soils (pH 4.306~8) and is less affected by water logging and salinity than most other pulse crops. At least in South America there appear to be few problems with attack by insects, fungus, bacterial or viruses; my (1968) cites some reports of insect attack. (III) Agronomy. The species is rapid and easy to establish. Germination is usually greater than 90%, and the large seed (.1-S g) results in a vigorous seedling. In one experiment emergence at 24 d was not influenced by planting depths ranging fran on the surface to 15 cm, and emergence was always greater than 80% (Centeno, unpublished results). There is considerable information on density of planting in the range 30 000 - 70 000 plants per ha; there were fewer weed problems with higher densities, and apparently little effect on the maturation of the pods. Although an annual plant it has scme potential for regrowth.; for example Contreras (.1982) observed regrowth of 40060% of total plants hvested during the dry season at 184 d of growth. ~Regrmvth will presumably be affected by frequency and severity of defoliation and water stress. Pound ti c&. (1983) observed good regrowth, but as the frequency of defoliation for forage was increased the yield of grain decreased. (IV) Yield. It is a fast-growing plant producing a high yield of both entire w and grain within 4-5 months (Table 1). The results of the experiment in Table 3 also demonstrated that in the second phase of growth after harvest of all of the pods at 150 d, the proportion of leaf to stem and the production of grain were much lower than the first phase of growth.. Distribution of the various plant parts was similar for the 131 TABLE 1 Changes with time in yield (tonnes/ha) of various components of &WzUv&U grown at two densities at Maracay, Venezuela (Mora 1983) l two densities. On a world basis yields are usually in the range 800-1000 kg grainha (National Academy of Sciences 1981; I&y. 1978); but in Maracay, Venezuela with. fertile soil, irrigation, fertilizer and weed control yields. of up to 6 QQO kg/ha of grain plus 10 00.0 kg&a of crop residue have been observed. This was equivalent to 3 600 kg/ha of crude protein and 11 400 kg/ha of dfgestible organic matter [Table 2 and 31, The proximal analysis of various parts of the plant fran an experiment in Maracay are given in Table 3. Under the conditions of this experiment the grain comprised 39% of total dry matter, contained 31% crude protein and 17% cell wall constituents and was 89% digestible &Z V&LO. The leaf and immature pods together accounted for 28% of total dry matter, contained 19-20% crude protein and were 62064% digestible & V&&O. There was a low lipid content in the grab (4%). a and calculation by sfference suggests that approximately 45% of the graiZn was starch. The.amino acid composition (mg/gN) of the grain protein has been reported as: glutamic acid 644; threonine 275; serine 336; alangne 275; glycine 241; valine 288; methionine 85; isoleucine 250; leucine 453; tyrosine 239; phenylalanine 322; lysine 344; histidine 168; arginine 294; tryptophan 75 (Kay 19781, Hence, in common with most pulses the sulphur &no acids tend to be deficient. On the basis of the proximal analysfs. Ca~ra~td& enS~&&n& grain should be approximately equal to a I:3 mixture of maize grain and oil-seed meal. PRESENTLY IDENTIFIED PROBLEMS WITH cCmaVU&iU enSi$Q&?& (.I1 It is an Wnder-developed plant species. There are no selected cultivars ccxnmercially available, although results of preliminary selection trials Kontreras 1982; Viera, unpublished results.)suggest that there is cons$derable genetic variation in habit of the plant and dry matter yield. Secondly there Ls a lack of uniformity in the position of the pods on the plant and 2n time of maturation of the pods; both of these factors are important rki exploitation of the plant for grain. An appreciable proportion of the gr&n can be lost by some pods drying and opening before all pods are mature (eg 25% during one month after maturation of the pods; Mora '983). I . 132 TW 2 Production of &UZCWLh in various experiments and by rotting of pods in contact with the ground. Irregularity in seed siqe and shape also introduces problems of mechanization. (II), Toxicity. The most important problem of CWVW mb&(uhni,b 2s the presence of several toxic factors, those currently identified &ng the protein concanavalin A present in the seed, and the amino acids canavanine. and canaline which .are present in various parts of the plant. Rosenthal (:19r71, 1972) has demonstrated that canavanine occurs in the leaves and immature pods and that m.concentration decreases in these tixsues but increases in the seed during maturation. We are not -aware of any fnfomation on the variation in toxicity betwe.en various genetic straTns or w&h the phy&ologicaIstate of the plant. The protein concanavalin A is a lectins of PkUO&lA VL@LL4 CPuztai of action irs by di&ption of the cells reduczng the absoxptzon of nutrients. lectin CLiener 1981). Evidence from 1981) suggests that its primary mode lining the small intestine thus` This, protein constitutes 23-28% of 133 TABLE 3 Distribution of parts of the plant, and proximal analysis in the parts of . CCUZ~V~~ (150 d, 60 000 plants/ha). . (Mcra . 1983). the protein in UVIUVU enSi@!?& grain (Hauge. 1975). It is thermolabile in wet heat, and also since it is highly soluble in weak saline solution it is probably readily degraded in the rumen. The amino acid canavanine occurs in the free form and may`: coh'stittite (Rosenthal and Bell 1979). Its of the drymatter of the grain taxicity probably occurs because it is a structural analogue of arginine (.Hegarty and PetersOn 1973; Hegarty . 1978). i.and may perhaps cause interference with the transport of synthesis ok amino acids or with protein It is highly soluble, but stable to synthesis (F-den and Lea 1979) heat (decomposition temperature 184'C). A quantitative analysis has been descri&ed by Rosenthal (1977). 305% l The amino acid canaline is known to be produced by the hydrolysis of canavanine, and also occurs in the free form. Its quantitative importance is not know and the mechanism of its toxicity is controversial (Rosenthal and Bell 1979). It is a structural analogue of ornithine# and Miala ti &. (1971) have suggested that it is an inhibitor of pyridoxyl phosphate. It is also highly soluble and stable to heat. The intestinal m.icr&es+are implicated in the action of one or more of these toxic factors, since germ-free Japanese quai: have demonstrated a much greater tolerance than normal birds to the toxicity of untreated CAVE grain (Jayne-Williams 19731, There is no doubt that these toxic factors can have severely detrimental effects on animals. Feed intake and gruwth rate of growing chickens, 1aySng hens and pigs are severely depressed when untreated CUUJ~LU grain is included in diets, and if the CUUML&CL diets are continued death often results. In ruminants Shone (1961) demonstrated that CUZUVU ensi&V~& grain could cause death if given at 1 ,O-1.5% liveweight directly into the rumen for several consecutive days. In contrast to this observatia, Mora -( 1983) did not observe any toxicity symptoms or find any clinical abnormalities during postmortem analysis with sheep that had consumed diets containing 32% untreated (h+~Nd& meal for 4 ~months. As a consequence of these observations the principal research effort of the group in Maracay has been to examine treatments intended to reduce the toxic effects,' and to examine effects of subst2tution at various levels of CCWWaeCa enS;i@WbC6 for more conventional feed sources~ 134 USE OF Canavalia ensiformisi GRAIN IN POULTRY RATIONS Experiments with growing chicks (Table 4) have invariably demonstrated poor grwth rates and feed conversion when lo-15% of a conventional rati'on based on soyabean meal and maize flour resfdue was replaced by ground, but otherwise untreated, Can~rvae4ia enSi&&&& grain (untreated w~tb&kt meal). Depression tended to occur even with a 5% level of inclusion. Autoclaving of the -u&e& meal could remove the majority of this toxic effect(Table 4) - Supplementation with the amino acids lysine and methionine in a free form slightly improved growth rate when untreated CWU&& meal was used, but had no additional effect when the cmvdd meal was autoclaved. Supplementation with arginine of diets containing autoclaved CWV&X~ meal has given a positive response during the first 2 weeks of growth of chicks (Co Vierma, unpublished results). In the experiment of Risso (1983). ensiling C-V&~ meal [with 3% urea + 2% Nfl4OH: for 10 days at 50% dry matter) was partially effective, but less effective than autoclaving, in removihg the growth depression. &eatment of CWVti meal appears essential for use in diets of growing chicks, although whether cnrrmercial processes such as pelleting or extrusion provide sufficient heat treatment is not known. Laying hens appear less sensitive than growing chicks to incorporation of untreated cm~&itt meal in the ration. Neither egg production nor feed conversion were affected by the inclusion of 10% untreated C~WU& meal in the experiments of Carabtio a d. (.1980) or Herrera & a*e. (1981), although. the latter authors reported severely adverse effects with a 2Q% level of knclusi'on. In a second experiment (Mantilla & &. 1'9Sl)' intake was also reduced from 80 g/d to 26 g/d when 20% untreated CCUZ~V&& meal was incorporated into the ration; ensiling with ammonia or urea was moderately effective in increasing intake, but autoclaving was also required for intake and egg production to equal the positive control. These experiments suggest that concanavalin A is the primary toxic factor for poultry- and * that autoclaving is effective in destroying this toxicity. Ensiling under alkaline conditions permltted at least partial degradation of this protein and/or the toxic amino acids. USE QF CtWUtVdiiX fZJ+Zbi$O/uncd GRAIN IN PIG RATIONS Less information is available on the use of CWV& grain in rations for pigs than for poultry. Weaned pigs (.42 d) would not tolerate even 5% untreated hU~&ikt meal in the ration and in a 15 d trial all animals receiving C~tdLtt lost weight (6 to 120. g/d] although grwth on the control diet was 250 g/d (Russo 1983). C~V&& meal autoclaved or ensfled with (-3% urea + 2% NH4OH.I at 50% dry matter for 12 d and incorporated fnto diets for gruwfng pigs was also associated with some depression in growth rate even at the-S% level of incorporation CTable 5). It appears that pigs are highly susceptible to the toxins of untreated CauraV~ meal, A greater susceptibility of growing pigs and rats than of laying hens -to fngest3on of diets containing untreated grain of Ptab:eoh v@U, which. also codains ' lectirns a has also been observed (Puztal 1981). Possibly the presence of the urea cycle in pigs but'not in poultry iti important, or perhaps a greater arginine requirements of the former species during growth i's involved. The failure to remove the toxicity by autoclaving suggests that the amho adds canavanine. and canalfne are of greater I'aaportance in pigs than poultry as toxic factors, It is perhaps of interest that the white collared peccary [~&dl#!Uh &&CL& similar to the pig but possessing 135. 'TABLE 4 Effects of incorporating h+~Wcte*ia meal into diets for growing chicks'; . Leghorn chicks were used in Expt 1, 2 and 4, commercial broiler chicks in Expt 3 and 5 (n = 40 in each treatment in Expt 1 - 4)m Autoclaved, 90 min; 121�C, 15 psi; Vitamin B6# commercial pliridoxine chloride 8 mg/kg; Ensiled at 50% dry matter with 3% urea + 2% NH4OH for 12 days. Level, level of incorporation of ctU+ta~t&tt meal in the diet; FC, feed conversson efflcbncy in kg feed dry matter/kg liveweight gain. Car&&o & d.1977; Montilla & &. 7977; Carabiio 4*t et cd!. 1981; Risso 1983. d.1979; Carabaiio 136. . (I'). General. The potential of cavZaVCC& U+&.~&Vzn& for ruminants is more flex2ble than with monogastrics where only the mature grain is likely to be useful. I'n ruminants the possibilities include the use of the entire plant (.a) as a component of mixed grass-legume pasture, (b) as a 'protein bank?' with intensive control1e.d grazing, or cc) in a feedlot system. Alternatively it may be viable to use the grain or grain plus pods or the foliage remaining after harvesting the grain. We know of no information on the use of &uuv~!& under grazing conditions or of the foliage after harvesting the grain. In one experiment (Bughes-Jones & &. 1981) where C~mavW was usedas a forage supplement to sugar cane juice, intake of CCUUZVU&&X was much lower than that of wheat bran, sweet potato forage or &C&&U decwhtti forage, suggesting a low palatability of the CaMorvaeia.. Low, &ataEUi.'y~ has also been reported by Sherman (-3977). In contrast we have observed c&~&CL forage to be eaten readily when presented separately to cattle. accustomed over several months to consuming &u+zQ~& forage .mixed wi'$h NaOH treated gra&.fokage .(R;-M;:btion; 'unpuubL&hed results). The toxicity- problems appear to be less serious with ruminants than with monogastrics as i& to he expected from the ability of the nznen fermentati'on to change and therefore destroy the toxic components of cluzavm. Being soluble in aqueous solution, concanavalin A, canavanine and canaline are likely to be ra#dly fermented in the rumen. (JfL Rumen fermentation, The rate of fennentatAon in the rumen of var?ous. components of c'GWUQU&t &+Ui&?M plant in sheep fed freshlychopped P&&RI pu/rpUUURI forage plus concentrate such that either cottonseed meal of untreated CCUUWCUU meal constituted.20% and 27% 'respectively of the total dry matter intake are shown in Table 6, The results demonstrate a h%gh rate of fermentation of the graLn, which would imply that little C~V&!& protein would escape fermentation in the rumen of sheep. The rate of fermentat2on of leaf (Tz 35 and 43 h) suggests that in terms of availability of tigestible energy it is a good quality forage. These rates of fermentation are somewhat slower th& those observed in other experiments (Santana & a. 137, TAB= 6 Measurements of rumen fermentation and digestion in three sheep. consuming rations containing either 20% cottonseed meal or 27% untreated &WWCLf!kL meal, (Mora . Y 983) 1981; M-Gill, unpublished results). This experiment also clearly demonstrated that consumption of untreated &W&&&Z meal had an inhibitory effect on the rate of fermentation of fibrous materials in the rumen; rate of fermentation of stem and leaf of CUUZV&&X were reduced by 29% and 19% respectively (Table 6). This reduction is consistent with experiments &Z v&o where addition of untreated CUFUZV& meal reduced the rate of fermentation in rumen fluid of c&+&U m hay, and where canavanine severely reduced growth of pure bacterial cultures (Kihara & Snell 1955) 0 . Table 6 also shows the pH, concentration of ammonia,and concentrations and proportions of volatile fatty acids in the rumen of sheep supplemented with either cottcnseed meal of untreated Cavra~a*e*ia meal. The consumption of c@tdt~tddt was associated with tendencies for higher pH, 1ckJer ammonia concentration, a greater proportion of acetic acid and a lesser proportion of propionic acid, and a decreased fractional outflow rate of liquid from the rumen. The latter observation, suggesting a decreased rate of removal of digesta from the rumen, is consistent with-a, slaughter experient(Mora 1983). where in sheep fed &ets contaking 0, 22% or 32% untreated C~VU;~VCL&L meal the weight of rumen digesta tended to increase from 19.0% to 19.2% to 22.4% of liveweight as the proportim of dietary c~~tbbb was increased. (III) Digestibility and growth.,The results of two experiments where . untreated Ccrn~r~cteia meal was incorporated hto the rations of either sheep or heifers are given in Table 7. In sheep there tended to be a depression in digestibility of dry matter and cell wall constituents as untreated CUPUWL&& meal was incorporated irnto the diet. There was a tendency for growth rate of male sheep and of hei:fers to be depressed (92.94% of control) at the 22% and 30% levels of incorpaation respectively, while the 32% level of incorporation significantly reduced by 27% the growth rate of male sheep. In female sheep, a tendency for liveweight gain to increase with the c 138 incorporation of cWv&Cr was noted; but the effect was not statisticaly significant. The observation that the 30% incorporation appeared to have a lesser effect with the heifers than the male sheep may have been because the ration in the former experiment was treated with NaOH and pelleted, perhaps thereby reducing the toxicity. Ground CUZQVCL& enS~&rurtis grain plus pods, either alone or with Ca@ub cajan forage, has been used as a supplement for growing steers at pasture (Rosales 1983), The &WaV&& was readily consumed, although in this experiment growth rate was not increased by 1.2 kg/d of ground pods. Equal growth. LO.7 kg/d) with whole CCWZUV~&Q pods or cottonseed meal in a feeding trial with cattle has also been observed (Skennan 19771, We are aware of only one experiment where entire C~WZV&~CL plant has been incorporated into a ration (Dixon & t&.1983). Chopped CMVW ~6~ &Id plant was mixed with PGW&&WI puhpurteUm forage (.40/60 ratio),trezted with NaO& and the mixture used as a basal diet for growing cattle. With supplements of 350 or 700 g/d of cottonseed meal, intake was 2.9.3.2% of liveweight and grawth rate 5187562 g/d. Cwarison with other experiments in this departmen t (Castillo 1983; F. Alvarez, unpublished results)suggests that the httt~tZ.&tt forage had a replacement value equal to 1-2 kg/d of concentrate, (IV) Reproduction, Untreated h~~~ae*ia meal has,been compared to soyabean meal as a supplement to forage for ewes during joining and pregnancy (Medina & Miranda 1983)'. Although there were only 12 ewes in each treatment, the results do suggest that the caav&& supplementation had little or no detrimental effect on conception or pregnancy. Furthermore, there was apparently no difference in the subsequent reproductive performance of the heifers used fn the growth experiment described in Table 7. 139 coNcLusIoNs The principal advantage of CWV&%Z is that it is a legume that can, with minimal agronomic inputs, produce high yields of digestible organic matter and crude protein under favourable environmental conditions t but at the same time can produce on low fertility soils, Clearly much more information is needed'on the agronomy of the plant, particularly studies on genetic selection, effects of photoperiod, potential for regrowth after cutting, and the problems of mechanization. The principal pr&lem is the presence of various toxic factors, but we suggest that these problems are not likely to be more serious than those encountered during the development of, for example, soyabean as a commercial crop. Much more development must be carried out on simple treatments to avoid toxicity with poultry and pigs, to obtain more information in its use for ruminants under feedlot and grazing conditions, and to confirm that there are no long-term effects. on Growth :and reproduction, The suitability of cCWW&&Z as a component of l a grazing system is not currently known. Despite these problems we consider CWVU has a major role in animal production in the tropics. . aFERENCES . ADDISON, K.B. (1957), Rhodesia Agric. J. 54: 527 BELL, E.A. (1978) : In ,'Biochemical Aspectrof Plant and Animal CoevolutionV', P- 143, editor 3.B. Harborne. Annual Proceedings of the Phyt&hkx&al'. Society of Europe No.15. (Academic Press: London). CANALES, F.S. (1976). ',L& civilizaciones prehisp&icas de Amgrica,, (Editorial Suda&rica: Buenos Aires). CARAB~O, J.M.# VARGAS, R., SCHMIDT, B. and MONTILLA, 3.3. (1977). Acta CientZlfica Venezolana. 28 Supp 1: 36. CARAB~O, J.M., MONTILLA, W.,EDENHOFER, H. and SCHMIDT, B. (1979.). Anales de1 VI Conqreso Latinoamericano de Avicultura, Lima: 75 CARABA8f0, J.M., ARMAS, A., MADRIGAL, J. and.MONTIUA, J.J.- (-39.8O)- Acta Cientzfica Venezolana. 31: 244. CARABWO, J.M., WIEDENHOFER, EMONTILLA, J.J., BALDA, R.-and SCHM&B. (1981). Anales de1 VII Congreso Latinoamericano de Avicultura, Guatemala: 192. CASTIILO, E. (1983)e Teds de grado, Facultad de Agronda, Universidad Central de Venezuelae CONTRERAS, J. (1982). Tesis de grado, Facultad de Agronda, Universidad Central de Venezuela. DIXON, ReMe, ESCOBAR, Ae, PaSTON, TeRe ad PARRA, Re (1983). TrUp, AI&II, Prod. (In the press), ! FOWDENT and LEA, PeJe (1979), In 'Herbivores: their interaction with second- plant metabolites', pe 335, editors GeR. Rosenthal and De H.,Jangen, (Academic Press: New York), FREDERICK, LaRe (1978)e In 'Mineral Nutrition of Legumes in Tropical and Subtropical soils', pe 265, editors CeSeAndrew and E,J,aprath. (CSIRO: Melbourne), GARCIA, Me (7982)e Tesis de grado, Facultad de Agrommza, Universidad Central de Venezuela,- ' HAUGE, D.Re (1975)e Plant Phvsiol, 35: 636, HAVARD, DeRa (1975) 0 %as plantas f=rajeras tropicales' (Editorial Bhne: Barcelona) HEGARTY, M,P, (1978), In '*Effects of Poisonus Plants on Livestock!*, p.575, editors ReF,Keeler, K.R. VanKampen and L.F. 'James, (Academic Press: London). ' l 140 HEGARTY,M.P. and PETERSON, P-J. (1973). In 'Chemistry and Biochemistry of Herbage', Vol.I,p.2,editors G.W.Butler and R.W.Bailey.(Academic Press: London.) HERRERA, F.# GUTIERREZ, M., CUPUL,S., FERREIRO,M., CARABAN0,J.M. and MONTILLA, J.J. (1981). Trap. Anim. Prod. 6L: 375. HUGHES-JONES, M., ENCARNACION,C. and PRESTON,T.E. (1981). Trap. Anim. Prod. 6: 271. JANE-WILLIAMS, D.J. (1973). Nature New Biol. 243: 150. KAY, D.E. (1978). 'Food legumes*', Crop and Prom Digest No.3. (Tropical Products Institute: London). KIHARA, H. and SNELL, E. (1955). 3. Biol. Chem. 212: 83. LIENER, I.E. (1981). In 'Antinutrients and NaturToxicants in Foods', p.143, editor R.L.Ory. (Food and Nutrition Press: Westport, USA). MEDINA, So and MIRANDA, 0. (1983). Tesis de grado, Facultad de Agronda, Universidad Central de Venezuela. MONTILLA, J.J., 'CARABmO, J.M., SCHMIDT, B. and VARGAS, R. (1977). Acta 'Cientffica Venezolana. 28 Supp. 1:35. MONTIILA, J-J., FERREIRO, M.,%JPUL, S., GUTIERREZ, M. and PRESTON, T.R. (.1981). Trop. Anim. Prod. 6: 376. MORA, M. (1983). Tesis de grado, -Facultad de Agronotia, Universidad Central de Venezuela. MORA, M., PARRA, R. and ESCOBAR, A. (1982). In 'Simposium sobre leguminos-as en alimentacion animal', XXX11 Convenci& Anual de ASOVAC, Caracas, Venezuela. NANGJU, D. and BAUDOIN, J.P. (1979). J. Hort. Sci. 54: 329. NATIONAL ACADEMY OF SCIENCES. (1981). 'Tropical legzes, resources for the future'. Washington, DC. POUND, B., DQf$E, F. and PERALTA, G. (.!982), Trop. Anim. Prod. 7: 262. PUZTAI, A. (1981). In 'Rowett Research. Institute Annual Rep~rt~p. 110. (Aberdgen, Scotland). RAHIALA, E.L., KEKOMAKI, M., JANNE, J., RAINA, A. and RAHIA, N.C.R. (.1971). Biochem. Bibphys. Acta. 227: 337. RISSO, J. (1983). Tesis de graK Facultad de Agronda, Universidad Central de Venezuela. RISSO, J., CARABmO, J. and MONTILLA, J. (1982). In 'Simposium so&e leguminosas en alimentaci& animal', XxX11 Convenion anual de ASOVAC, Caracas, Venezuela. ROSALES, J.G. (1983). Tesis de grado MSc, Facultad de Agronoml'a, Universidad Central de Venezuela. ROSENTHAL, G.A. (1971). Plant Physiol. 47: 209. ROSENTHAL, G.A. (1972). Plant Physi.01. 50: 328. ROSENTHAL, G-A. (1977). Anal. Biochem. 7: %47. ROSENTHAL, CA. and BELL, E.A. (-197% z tvHervibores: their interactions w&&h second= p&t metabolites'!, p. 351, editors G.A. Rosenthal . . . and D-H. Janzen. :(Acade&c Press3 New york)J.. 5: SANTANA, A., PERALTA, GqJ and GILL, M. (198O)a'dTrop. Anim. Pied. = 82. SHONE, D.K. (.1961). Rhodesian Aqfic..J, 58: 10. ? . SKEI?MAN,*P.J'. (.l9.77]. '*Tropical Forage fgTkmesr,. FAO. Plant Production and Protection Series No. 2 '(FAO: me). . VIERA, J., ESCQBAR, A. and MORA, 'M. (11982). In 'Simposium sobrelegumixosas en alimentaci& animal', XXX11 Conveni6n Anual de ASOVAC, Cara;I . cas, Venezuela. WHYTE, R.e,:. NIZSSON-LEISSNER, G. and TRUMBLE, H.. (1953). In 'Agricultural Studies!', No. 21. p.242, 258. (FAO: Rome). Availibility of Seed. Upon request, we will endeavour to send samples of seed of our selected varietiesof cavzcrvw wui@?k6 0