MARDI Res. Bul l . (1986) 14(1),69-80

EFFECTS OF STOCKING RATE AND GRAZING MANAGEMENT ONCATTLE PRODUCTION FROM TROPICAL GRASS

DIGITARIA SETIVALYA STENT

C.P. CHEN* and O. OTHMAN*

Keywords: Stocking rate, Rotational grazing, Continuous grazing, Pasture and animalproduction, Botanical and chemical composition.

RINGKASAN

Satu percubaan te lah di ja lankan di Serdang selama empat tahun untuk mengkaj i kesan-kesankadar muatan ternakan (stocking rate) dan pengurusan ragutan terhadap berat kering pastura,pengeluaran ternakan serta kandungan botani dan kimia pastura Digitaria setivalva yang dibaja dengannl t rogen.

Pengeluaran ternakan yang tinggi dihasilkan dengan penambahan bilangan ternakan di dalamsistem ragutan berpusingan iaitu sistem di mana pastura diragut selama seminggu dan dibiarkan tanparagutan selama tiga minggu. Di dalam sistem ini berat kering pastura yang tinggi telah dicatatkan. Disamping itu peratus rumput digit adalah lebih tinggi dan kewujudan rumpai lebih rendah berbandingdengan ragutan berterusan.

Perlakuan ragutan berpusingan pada kadar muatan ternakan 6.7 ekor/ha dan ragutan berterusanpada kadar muatan ternakan 5.3 ekor/ha mengekalkan pastura yang stabil untuk mencapai kadarpengeluaran ternakan yang terbaik di samping menghasilkan penambahan berat hidup yang tinggi bagiseekor lembu. Walau bagaimanapun. paras mineral pada pastura yang diragut secara berterusan lebihtinggi berbanding dengan pastura yang diragut secara pusingan.

INTRODUCTION

In any area being grazed. whetherimproved pasture, natural grassland orrangeland, the output of animal per unitarea is a function of the production peranimal and the number of animals per unitarea. The production per animal reflects thegenetic potential of the animal and moreimportantly the quality of the pasture. Thenumber of animals per unit area (stockingrate) which can be supported by the pasturefor a given period of t ime, is basically afunction of pasture yield (WHtrelteN,1977). Pasture yield under grazing isdependent upon a number of factors ofwhich ferti l izer regime, stocking rate andthe management system are major deter-minants. Earlier report on Digitariasetivalva under continuous grazing systemhad shown the impact of nitrogen ferti l izeron both pasture and animal production withthe optimal stocking rate to be slightly

below six heads of local Kedah-Kelantancat t le per hectare (CHex. A: t r and Evnxs,1981). The productivity of D. setivalvasubjected to similar stocking rate treatmentbut under d i f ferent graz ing managementsystems is not yet known.

Qui te recent ly great controversy iscentred on grazing management system onpasture i.e. continuous yr rotational grazing.MnruNet:e, JoNEs and Srosss (1976) hadreviewed and summarized the data from 16grazing trials in the tropics. They found thatout of 12 trials, eight showed continuousgrazing was superior to rotational grazingand two showed reverse results while inanother two trials the l iveweight gains ofanimals from both grazing systems weresimi lar .

Continuous set stocking is preferredunder practical farming simply becauseavailable information does not seem to

*Livestock Research Division, MARDI, Serdang, Selangor, Malavsia

69

favour any grazing management system toprovide higher animal production thancontinuous grazing system. This system isalso the easiest and least expensive methodto implement. However, under the hot andhumid environment with high and evendistribution of rainfall throughout the year,the performance and production of pasturein association with cattle production mayvary greatly from one place to another evenunder the same management svstem.

This study examines the performanceand production of nitrogen-ferti l izedDigitaria setivalva (digit grass) grazed atdifferent stocking rates under rotational andcontinuous grazing management systems.

MATERIALS AND METHODS

The experiment was conducted inMARDI Station at Serdang (Lat.3'N, Long.101" 41'E). Soils were red-yellow podzolicsof the Serdang series (typic dystropept-tropudult), well-drained with sandy loam tosandy clay loam top soil and yellow-brownto strong brown subsoil (Lnw and Tax,1975). Rainfall at Serdang adjusted to 37-year mean was 2 568 mm/yr and was welldistributed with a minimum of 114 mm(June Ju l y ) and a mean m in imumtemperature of 21'C - 22'C (September -

May) (ANoN ., 1966).

The experiment was of a factorialdesign with three stocking rates of 4.0 (SR4.0,) 5.3 (SR 5.3) and 6.7 heads/ha (SR 6.7) .and two grazing management systems(rotational ys continuous) with tworeplications. Under rotational grazingmanagement, pasture was grazed on for oneweek and rested for three weeks in four sub-paddocks arrangement. However, after twoyears of grazing, SR 4.0 and SR 5.3 (lowerstocking rates) were adjusted (14 November1979) respectively to 6.0 headsiha (SR 6.0)and 8 headsiha (SR 8.0) by adding oneanimal to each treatment. The thirdstocking rate (SR 6.7) was maintainedthroughout the trial.

Stocking rates were obtained byvarying the paddock size but keeping twoanimals per paddock. A total of 24 Kedah-Kelantan cat t le (KK) were used dur ing thefirst two years of grazing ( 1 2 January 1978 to15 November 1979). The adjusted stockingrates of three heads of Brahman x KK (BK)crossbred cattle per treatment completedthe second stage of experiment ( 15November 1979 to 12 November 1981).

The one-year-old bulls with meanliveweights of 89 kg/head of KK and 91 kg/head of BK were put to graze on thepasture. The bul ls were removed wi thaverage finishing l iveweight (LW) of 272 kgand 305 kg per head respectively. Theanimals were dewormed with Nilverm andsprayed wilh Asuntol before grazing started.These practices were repeated at yearlyinterval . The BK crossbred animals weregiven cobal t bul le ts on 26 November 1979,soon after the replacement of KK cattle onpasture. Two dosages of FMD vaccine wereadminis tered on 24 October and l5November 1980 when foot and mouthdisease was prevalent . Water and minerall icks were avai lable a l l the t ime. Thechanges in animal l iveweight gain (LWG)were recorded everv four-weekly after anovernight s tarv ing. Two animals f rom eachtreatment were selected for carcass analysesat the end of the exper iment . Resul ts of theanalyses would be reported separately fromthis paper.

Pastures were hand-planted on a gr idof 1 m x 1 m using vegetat ive mater ia ls .Standard fer t i l izer of 300 N, 50 P. and 100 Kkg/ha/yr as urea. triple superphosphate andmur iate of potash respect ive lv were appl ied.Ni t rogen was spl i t equal lv in three appl i -cat ions whi le P and K were appl ied twiceyear ly . Pastures were sampled (27 January1978) soon after the imposition of grazingand subsequently at three-monthly intervalsfor estimation of dry matter yield on offer toanimals. I t was cut wi th a t ractor-mountedreciprocal cutter bar at about 1-5 cm heighton randomly selected st r ips (1.8 m x 5 m).

70

Four strips were taken from the continuousgrazing paddock. In the rotational grazingtreatment, a random of one strip per sub-paddock was sampled. Botanicalcomposition of pasture sward wasmonitored by the point quadrat method onthree occasions on 26 June 1980: 2 Marchand 5 November 1981, with 60, 75 and 100quadrats being scored depending onpaddock size. The plant mineralcomposition was analysed from randomlyhand-grabbed samples of grazing pasture soas to simulate the cattle grazing. Thegrabbed pasture sampling was done twice ayear during the monsoon as well as the dryseason. Samples from rotational grazingpaddock were analysed according todifferent ages of pasture regrowth whilesamples from continuous grazing paddockwere bulked before analysis.

Attempts were also made to correlatethe pasture on offer in association with totalbiomass of cattle in the grazing paddock l.e.grazing pressure which is expressed as totaldry matter (DM) of pasture (kg/ha) per totalbiomass of animal l iveweight (kg/ha). Thegrazing pressure sustained at the end ofsecond and fourth year were computed.

RESULTS

The annual rainfall recorded since theestablishment of pasture were 3 027 (1977).1 e5s (1e78),2 s64 (1e79),2 175 (1980) and2 060 mm (1981). These amounts of rainfallwere arranged according to the dates ofpasture yield sampling, cumulative to three-monthly interval for analyses. The effect ofrainfall l on pasture and animal LWG wasnot clear despite some visual stress onpasture during drought.

Dry Matter Yield

The three-monthly changes in pastureDM on offer in response to animal stockingrate, grazing management and rainfall overthe four-year experimental period areshown in Figure 1. The yearly mean DM onoffer in relation to the main treatment

effects is given in Table 1.

Table 1 shows that after two years ofgrazing. neither stocking rate nor grazingmanagemant system had any effect onpasture production. This implied that theinit ial stocking rates designed for thepasture were slightly below optimum. Thusthe stocking rate treatments were adjustedfrom SR 4.0 to SR 6.0 and f rom SR 5.3 toSR 8.0 by adding one animal to eachtreatment while SR 6.'7 remained un-changed. In the third year, the effect ofgrazing management on pasture was signifi-cant (P<0.05). Rotational grazing systemmaintained higher mean DM yield on offer(2 977 kg/ha/yr) than continuous grazing(2328 kglhalyr). By the fourth year, whengrazing pressure increased, pasture DM onoffer responded markedly (P<0.01) to bothgrazing management and stocking ratetreatments. Pasture under rotational grazingsystem sti l l maintained higher DM yield onoffer than that of continuously grazedpaddocks at all levels of stocking rat€s.However, as the stocking rate increased theamount of DM yield on offer decreased. AtSR 8.0 overall mean pasture DM on offer(l 162 kg/ha/yr) was significantly lowerthan that at SR 6.7 (1 816 kg/ha/yr) which inturn was not significantly different from SR6.0 (2 361 kg/ha/yr). At the end of theexperiment all pastures under continuousgrazing management were over-grazed withmean DM on offer of 315, 588 and 340 kglha* for SR 6.0. SR 6.7 and SR 8.0respectively, whereas under rotationalgrazing management the amount of pastureavailable for similar stocking rates were2 603,2753 and 1 686 kg/ha* respectively.There was no interaction between stockingrate and grazing management treatments. Itwas also true of the other parameters suchas botanical and chemical composition,animal production measured in this ex-periment.

Botanical Composition

Botanical composition of pastureduring the early stage (about 2.5 years) of

* last DM on offer recorded before termination of exoeriment

'71

-e

. a

0700600

400

200

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O

5 000

4 000

2 000

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Stocking rate

Grazing system

R = Rotational grazing

C = Continuous grazing

Rainfall

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1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 ' 7

No. of harvesting

Figure I . Changes in pasture dry matter yield on offer in relation to stocking rate,grazing system and rainfall.

Table 1. Effects of stocking rates and grazing management on changes in mean pasture drymatter on offer of Digitaria setivalva

Initial SR(heads/ha)

Mean DM on offer(kg/ha/yr)

lst year 2nd year

Adjusted SR(heads/ha)

Mean DM on offer(kg/ha/yr)

3rd year 4th year

Continuous grazing

SR 4.0

sR 5 .3

SR 6 ,7

Mean

Rotational grazing

SR 4,0

SR 5 .3

SR 6 .7

Mean

3 1702 6272 8422 880

2 7'732 7102 5482 677

3 0042 9832 1022 696

3 1482 9372 7392 941

sR. 6.0sR. 8.0SR. 6,7Mean

sR. 6.0sR. 8.0sR. 6.7Mean

2 8391 9752 1702 328

a ) t z

2 7072 9132 9',77

1 879489

1 340

| 23rJ

2 8431 8352 2912 323

L .S .D (5Vo )

Between grazing

system means

Between SR

N . S .N . S .

N , S .N . S . N . S .

SR = Stocking rate*Significant al 5Ea level

***Significant at 0.17o level

N.S.= Not significant

72

the trial had litt le changes. It was only afteradjustment in stocking rate that the changesin sward composition were accelerated.Different grazing systems greatly affectedthe main pasture (digit) as well as weeds butnot the bare ground (Figure 2). The area ofbare ground formed in the pasture swardincreased tremendously with time. The per-centages of bare ground recorded undercontinuous and rotational grazing systemswere similar ranging from about 2Vo to 72Vain the third year and 367o in the fourth year.

The overall proportions of digit inpasture sward for the continuous and rota-tional grazing systems were 62.9Vo and82.3% respectively at 32-month grazing;22.0% and7l.8Vo at 42-month grazing; and4.6Vo and 52.6Vo at the end of the ex-periment. However, the percentages ofvolunteer weeds increased under bothgrazing systems during similar period ofgrazing, viz.36.9Vo and 13.97a;65.27c and17 .0%; and 57.2Vo and 11.37c resDect ive lv .

The volunteer weeds comprised more than90% of monocotyledon species with a fewper cent of broadleaf weeds. Among thegrasses, Paspalum conjugatum andAxonopus compressus formed the majorcomponent plus some Eleusine indica,sedges and native Digitaria species. Effectof stocking rate on the botanicalcomposition in sward was not significant inthe analyses. However, low stocking ratemaintained higher percentage of sownspecies compared with that of medium andhigh stocking rates, whereas the amount ofvolunteer species showed the reverse trend.The bare ground area in the sward was fairlystable when comparison was made amongthe various stocking rates.

Chemical Composition

The ef fects of graz ing managementand stocking rates on changes in plantchemical composition of D. setivalva arelisted in Table 2. The differences between

100

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20

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S R 6 . 7

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WeedsBare groundD. setivalva

SR 6.0 = 6.0 heads/haSR 6.7 = 6.7 heads/haSR 8.0 : 8.0 heads/ha

Figure 2. changes in botanical composition in response to grazing managementand stocking rate.

Rotat ional grazing

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the rotational and continuous grazing andthe variations in plant mineral contents atdifferent ages of plant regrowth under rota-tional grazing are shown in Figure 3.

Statistical analyses showed that therewere no differences in certain mineral inplant either within or between the treat-

ments in this experiment, but it was evidentthat the level of nutrients fluctuatedmarkedly (P<0.01) between dates ofsampling (Table 2). In particular, thenitrogen content in pasture varied a lot(P<0.05) under continuous and rotationalgrazingat earlier sampling; but the variationwas later reduced. However. it was clearlv

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I = l-week regrowth

2 = Z-week regrowth

3 = 3-week regrowth

4 = 4-week regrowth

(cattle grazing)

Figure 3a. Changes in plant chemicalcomposition and variations in different

regrowth under rotational grazing.

C = Continuous grazing

R = Rotational grazing

Figure 3b. Changes in plant chemicalcomposition under rotational and

continuous grazing.

75

seen that pastures under continuous grazing

generally had higher nutrient levels thanunder rotational grazing (Figure 3b).Furthermore, when pastures were rota-

tionally grazed, the nutrient levels in plant

differed with the age of regrowth such thatyounger regrowth plant materials hadhigher nutrient status than older pastures(Figure 3a). The animals under rotationalgrazing system often grazed on pastures thatwere relatively low in mineral value. The

effect of stocking rate on plant mineralcontent was not c lear .

Animal Production

Animal production (kgihalyr) anddaily LWG of cattle arranged annually andbiannually where common stocking ratetook place were analysed. It showed that theeffect of grazing management on animalLWG became evidently significant onlyafter the third year. Both the animal pro-duction and daily LWG under the twograzing management systems were signi-ficant (P<0.01) in the fourth year while thestocking rate effect appeared to be con-sistent on the yearly animal production level(Table 3). For the first two years, animalproduction at SR 4.0 was significantly lowerthan those at SR 5.3 and SR 6.7 which inturn had no difference between the two. Inthe following period particularly in thefourth year, SR 6.7 emerged to be the beststocking rate in animal production with anoverall mean animal LWG of 628 kglhalyear. Similar trend was observed in the dailyLWG measurement. One interesting point(Figure 4) was that all pastures managedunder continuous grazing system. irrespec-tive of stocking rates, init ially producedhigher LWG than those under rotationalgrazing. However, after the adjustment tohigher stocking rates, rotationally grazedpasture resulted in higher animal LWG thanthose grazed continuously.

The grazing pressure recorded at the

end of second and fourth year showed great

variations not only between managementsystems but also between stocking rate

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6 1 2 1 8 2 4 0

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Time (months)

6 1 2 1 8

3rd year

244th year

remained relatively unchanged ( 1 .40 kgDM/kg LW in the second year and 1.11 kgDM/kg LW in the fourth year). The studyshowed that at lower stocking rates, con-tinuous grazing system was favoured withlO% l8.5Vo improvement in LWGwhereas at higher stocking rates. rotationalgrazing system would be better for bothpasture and animal production. It wasshown that irrespective of stocking rates, anoverall 60Vo higher animal LWG fromrotational grazing (656 kg/ha/vr) wasobtained compared with that of continuousgrazing (255 kglhalyr). On the humidtropical coast of North Queensland (annualrainfall 3 226 mm). Gnop and HnnolNc(1970) reported that two weeks on and twoweeks off rotational grazing system (155 kg/head/yr) achieved 14.87o better animalLWG (135 kg/head/yr) over continuousgrazing from a guinea-centro pasture. How-ever, in the drier environment (700 and1084 mm rainfall), i t was reported thatcontinuous grazing management improvedanimal LWG by 14Vo in Kenya (McKev,l97I) and by 257o - 55Vo in Tanzania(Wer-rEn and Scorr, 1968).

treatments. In general, grazing pressure (kgDM/kg LW) increased with time as theanimals grew. The pressures were 1.70 kgDM/kg LW in the second year and 0.20 kgDM/kg LW in the fourth year for conti-nuous grazing, and 1.40 kg DM/kg LW(second year) and 1.11 kg DM/kg LW(fourth year) for rotational grazing, whereasfo r SR 4 .0 , SR 5 .3 , SR 6 .0 , SR 6 .7 and SR8.0, the grazing pressures were 2.19, 1.4'7,0.68, .0.95 and 0.37 kg DM/kg LW respec-t ive ly .

DISCUSSION

An interesting outcome of this studywas that when grazing pressure was sti l l lowin the second year (1.70 kg DM/kg LW)both the animal production per hectare anddaily LWG per head under the continuousgrazing were superior to those under rota-tional grazing. However, when the stockingrate was adjusted to a high grazing pressurewhich increased to 0.20 kg DM/kg LW inthe fourth year under continuous grazing,animal production was adversely affected(Table 3). The overall grazing pressureunder rotational grazing management then

77

Of a l l the stocking rates tested underthe two grazing systems, treatment SR 6.7under rotational grazing was most im-pressive and outstanding. I ts animal pro-duction in the fourth year recorded 892 kg/ha/yr, equivalent to 396 g/head/day of LWG(Table 3) which also sustained a stablepasture of 2 753 kgiha of DM on offer in thelast sampl ing of graz ing t r ia l . Moreover, theoverall mean animal production over thefour-year exper imenta l per iod of SR 6.7 was703 kg/ha/yr (or 304 g/headiday) which wascomparable to 69fl kg/ha/yr (mean of twtryears) of an ear l ier exper iment us ing con-t inuous grazing system at 6 animals/ha(CHex et al., 1981). However, the reporta lso stated that unstable pasture and poormean DM on offer of 1 648 kg/haiyr wassusta ined by such a t reatment . Al thoughhigher mean LWG (332 g/head/dav) wasobta ined at SR 8.0 in the rotat ic ' rnal graz ing.the pasture stabi l i t l ' was not mainta ined.Under cont inuous stocking. a l l the h igherstocking rates imposed in the second hal f o fthe experiment were so severe to the digitpastures ( range: 340 - ,588 kg DM/ha in thelast sampling) that low weight gains u'ereobta ined (Table 3/ . At lower s tock ing rate(SR 5.3) , h ighest animal product ion (meanover two years of 484 kg/ha/yr or 272 g/head/day) and best pasture DM on offer wereobtained at the end of the trial (2 125 kglha) . This indicates that a sui table stock ingrate for continuous grazing management ondig i t pasture wi l l l ike ly be at 5.3 headsihectare. The marked differences in bothanimal production and daily LWG betweenthe first and second half of grazing trial wereprobably because of the cattle breeddifferences rather than the treatmenteffects.

The major effect of grazing manage-ment and stocking rate on digit grass was adecline in its production. It was accom-panied by a marked increase in both bareground and volunteer weeds. The change inbotanical composition of the pasture swardwas observed to be slow in the init ial twcryears, but the process speeded up im-mediate ly af ter adjustment in s tock ing

rates. The drastic drop in digit grass to-gether wi th the rapid invasion of vo lunteerweeds under continuous grazing suggestedthat th is management system was not su i t -able for digit pasture production, even atlow stocking rate of SR 6.0 (Figure 2).Simi lar problem of non-pers is tence in d ig i tsward was fbund when continuous grazingmanagement was adopted for the same digitgrass production with stocking rates of 6.0,8 .0 and 10 .0 heads /ha (CHr r e t a / . , 1981 ) .Srosss (1969) a lso exper ienced thatHvparrhenia rufa pasrure sward deterio-rated when i ts s tock ing rate increased undercontinuous grazing. In contrast. the rota-t ional graz ing management kept thevolunteer weeds dclwn to mainta in h igherpercentage of d ig i t grass in the sward.par t icu lar ly in lower s tock ing rate (SR 6.0and SR 6 .7 ) t r ea tmen ts .

In compar ison wi th the lower minerals tatus in d ig i t pasture under cut t ing e.g. N :

t .gc i . P : 1 .5() . t and K : l .54ct i . (WoNc.1980). i t is c lear lv ind icated that graz inganimals in th is t r ia l have ample opportuni tvto select forage of h igher nutr ient contentthan fhose sta l l - fed animals. I t is bel ievedthat in rotat ional graz in-e svstem the animalswi l l be restr ic ted in select ing h igher qual i tyforage. Resul ts f rom th is s tudv conf i rmedthat the nutr ient content in pasture on of ferto animal was h igher under cont inuous thanrotational grazing (Figure Jbl. The chemicalvalues in thc sward under rotat ional graz ingwere re lat ive lv lower compared wi th that ofthe younger age of pasture regrowth ( Figure3a) or those of under continuous grazing(Table 2/ . I t is ev ident a lso that h igheranimal LWGs from continuously grazedpasture were recorded init ially whenstocking rates were low (Figure 4) andsufficientlv high quality forage on offer wasavai lable for se lect ion. However. af ter ad-justment of stocking rates when grazingpressure was increased, the gains fromcont inuously grazed pasture were s igni -ficantly lower (Figure 1). This was mainlydue to the shortage of pasture on offer.Nevertheless. the best t reatment of SR 6.7on rotationallv grazed pasture pr<tduced

t8

highest animal production through sufficientfeed on offer (Table 1) during the course ofexperiment rather than through qualityforage (Table 2) to achieve faster growthrate. Similar results were reported byKlssocr (1966) in New Zealand wherehigher production in rotational grazingresulted from an increased number ofanimals per hectare.

The results show the advantage ofrotational grazing over continuous grazing.the former can withstand higher stockingrate associated with the higher forage pro-duction. The rotational grazing systemadopted in this trial was carried out for oneweek followed by three weeks off in foursubpaddocks arrangement. It is certainlvtoo tedious and laborious for actual farm

ANoN. (1966). Guide to the Federal ExperimentalStat ion, Dept. Agr ic. . Serdang. Malavsia.

Csp .N , C .P . , A r t r . S .S . and Ev rNs . T .R . ( 19 t i l ) . Bee fproduct ion f rom three ni t rc lgen-fer t i l ized grassesin Pen insu la r Ma lays i a . MARDI Res . Bn l l , 9 (2 ) .207 -24

Gnop . B . and Heno tNc . W.A .T . ( 1970 ) . D ry ma t t e ry ie ld and animal product ion of guinea grass(Panicum maximum) on the humid t ropicalcoast of North Queensland. Trop. Grasslds. 4,85 - 95.

Krssocx, W.J (1966). Hi l l country sheep t r ia l mobstocking proves supcr ior . N.Z.J. Agr ic. I 13, 2a.

practice. Hence, some forms of rotationwith larger areas of pasture and longergrazing interval need to be scrutinised.Further, the productivity of a mixed grass-legume pasture under rotational manage-ment system needs to be studied. Economicaspect of rotat ional graz ing managementinvolved in the overall production needs tobe assessed before one could reallv practiseat the farm level.

ACKNOWLEDGEMENTS

The authors would l ike to express theirappreciat ion to Dr. C.S. Lee for the stat is-t ica l analyses, the Centra l Analyt ica lServices for the plant chemical analyses andDr. Abas Mazni Othman for the health careof the animals.

Lew, W.M. and T , r r . M .H . ( 197 -5 ) . Range i n p ro -perties of Peninsular Malaysia soils. Proc. 3rdAsean Soil Conf ., Kuala Lumpur, 1975, pp. 43-68 .

MeNrp r :E . L .T . . JoNES. R . J . and S rosss . T .H .(1976). Pasture evaluat ion by grazingexperiments. ln Tropical Pasture Research (ed.S t t nw , N .H . and BnynN . W.W. ) pub . by CAB.Bu l l . No .5 / . Chap . 9 pp . 202 -10 .

McKnv . A .D . ( 197 ' l ) . Seasona l and managemen tef fects on the composi t ion and avai labi l i ty ofherbage, steer d iet and l iveweight gains in aThemeda triandra grassland in Kenva. II.Resul ts of herbage studies, d iet selected andf iveweight gains. J.agric. Sci. 76,9-26.

ABSTRACT

An exper iment was designed to study the ef fects of stocking rate and grazing management onpasture dry matter and animal product ion. botanical and chemical composi t ion of n i t rogen-fcr t i l izedDigitaria setivalva pasture over a period of four vears at Serdang.

Higher animal product ion resul ted f rom an increased number of animals in pasture was obtainedunder rotational grazing - a system with one week on and three weeks off grazing. This svstem conservedmore pasture dry matter on offer, maintained higher percentage of digit grass in the sward and reducedvolunteer weeds invasion compared wi th that under cont inuous grazing.

Rotat ional grazing at 6.7 heads/ha and cont inuous grazing at 5.3 heads/ha maintained stablepasture to achieve highest animal product ion per hectare as wel l as dai ly l iveweight gain per head.However. h igher p lant mineral levels were detected in cont inuously grazed pasture than in rotat ional lygrazed pasture.

REFERENCES

79

SroBBs, T.H. (1969). The effect of grazing manage- WHttrtr,lrr, P.C. (197'7). Tropical Pasture Science (ed.

ment upon pasture productivi ty in Uganda. L WHITEMAN, P.C.), Chap 5, p.277 New York:

Stocking rate. Trop. Agric., Trin. 46,78'7-94' Oxford University Press.

Wrlxtn, B. and Scorr, G.D. (1968). Grazingexperiments at Ukir iguru, Tanzania. L WoNc, C.C. (1980). Productivi ty and chemical

Comparisons of rotational and continuous composition of twenty improved tropical grasses

grazing systems on natural pastures of hardpan in the humid tropics. MARDI Res. Bull. 8(2),

soi ls. E. Afr. agric. For. J.34,224-34' 163-'73.

Accepted for publication on 15 lanuory 1986

80

@Copyright Malaysian Agricultural Research and Development Institute, 1986.

First Published 1986"

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Dicetak oleh Unit Percetakan MARDI, Serdang, Selangor.