Two Panicum maximum cultivars were studied with respect to forage leaf blade availability and extrusa through chemical parameters, tissue proportion and degradation. It was concluded by observing digestive residues that the studies qualitative parameters did not show indication of higher fragility of the cultivar ‘Aruana’ in relation the cultivar ‘Vencedor’

Cattelan, F.J W

Damiao, C F

Dantos, J.M dos

deFigueuredo, L.F C

Ezequiel, J.M B

Favorette, V

Lempp, B

Martins, A P, Jr

Zimmer, A H

English

University of Kentucky

Session 17 - Forage Quality 17-57ID NO. 994QUALITATIVE PARAMETERS OF TWO CULTIVARE OF PANICUM MAXIMUM,JACQ. UNDER GRAZINGB. Lempp, J.M.B. Ezequiel, J.M.dos Dantos, A.H. Zimmer, V. Favoretto, C.F. Damião F., J.W. Cattelan, L.F.C.de Figueiredo and A.P. Martins Jr.Universidade Estadual Paulista, 14870000, Jaboticabal - SP, BrazilABSTRACTTwo Panicum maximum cultivars were studied with respect to forageleaf blade availability and extrusa through chemical parameters,tissue proportion and degradation. It was concluded by observingdigestive residues that the studies qualitative parameters did not showindication of higher fragility of the cultivar ‘Aruana’ in relation thecultivar ‘Vencedor’.KEYWORDSExtrusa, anatomy, microscopy, chemical compositionINTRODUCTIONThe desirable qualitative characteristics of forage plants are thosethat favor the utilization of cell walls by rumen microorganisms,since their ability to degrade is seen as a digestibility index.Differences in anatomical structure, chemical composition and typeof lignification in grass cells have been related to the rate and extentof cell wall degradation in the rumen (Akin and Robinson, 1982).The inaccessibility of cell walls for microbial attack limits digestiveweakening (Wilson and Kennedy, 1996). Plant anatomy andstructural features related to physical disruption and reduction inparticle size by mastication may be important in forage intake (Laredoand Minson, 1975). Our purposes were to: 1) characterize leaf bladeanatomy and extrusa chemical composition of two cultivars ofPanicum maximum under grazing and report residual dry matter afterdefoliation and 2) to observe differences in tissue degradation forthe two forage cultivars.METHODSFour 400 m2 grazing areas of P. maximum were used, two that wereestablished with the cultivar ‘Aruana’ and the other with the cultivar‘Vencedor’, managed at two dry matter residues: 1880 (RGDM1)and 3000 (RGDM2) kilograms of green dry matter (GDM) per hectar.Before grazing a square of 0.50 x 0.50 m was located at three pointsalong a transect within each grazing area. A portion of each samplewas divided into leaf blade, stem plus leaf sheath and dead herbage.In January 1995, two oesophagally-fistulated steers were usedto collect additional samples (four collection per grazing area).Each 200 g samples was separated into leaf blade and stem plussheath portions.Random samples from the leaf blade of extrusa were prepared forhistological observations (Daykin an Hussey, 1985). The proportionalareas of bundle sheath (BS), vascular bundle (VAS) adaxial epidermis(ADE), abaxial epidermis (ABE) and sclerenchyma (SCL) weremeasured over a cross-secitonal area between the two major vascularbundles with digitized images (KONTRON ELEKTRONIC-ZEISS).The mesophyll (MES) was determined by the difference.The SCL cells were isolated from the 10 fractions of leaf bladesfrom available herbage sample and extrusa samples in Jeffrey’ssolution. Then 90 cells from each sample were measured throughoptical microscopy.Nylon bags were filled with approximately 0.5 g of extrusa leaf bladeson a dry matter basis. Each replicate was incubated in natura and invitro using the one-stage procedure of Tilley and Terry (1963) andtaken out after 48 h incubation. The residue was prepared by theprocedure of Santos (1995) for the scanning electron microscope(JEOL JMS 25SII observations.The available herbage leaf blades of and extrusa samples wereanalysed crude protein (CP; N concentration x 6.25), neutral detergentfiber (NDF), acid detergent fiber (ADF), and lignin (L) (Van Soestand Wine 1968).Statistical analysis was conducted using SAS.RESULTS AND DISCUSSIONThe available forage showed a mean of 76.7% leaves per GDM(P>0.05); 933.2 g GDM/kg of DM and its mean leaves 11.3% CP;76.2% NDF; 37.7% ADF and 4.6% L, (P>0.05) in DM basis.The extrusa presented a mean of 872.1 g leaves per kg GDM (P>0.05)and its leaves showed no differences (P>0.05) chemical composition(Table 1). It was observed a difference (P>0.05) related to the RGDMonly for the L variable, RGDM1 = 3.6% and RGDM2 = 4.8% inDM basis.There were observed no differences (P>0.05) in the extrusa tissueproportion among the RGDM. Aruana extrusa exhibited a higherproportion (P<0.05) of ABE and ADE and lower (P<0.05) BS inrelation to Vencedor (Table 1). The otehr proportions were as follows:SCL = 1.0; VAS = 3.4 and MES = 37.9 (P>0.05).The SCL cell length for herbage leaf blades for Aruana showedsimilarities for the two RGDM at 58.5% in general with 500 to 900µm, 38.9% with 900 to 1300 µn and 2.2% above 1300 µm. Thosefrom the extrusa ehibited 85% of the cells from 100 to 700 µn and15% from 700 to 1100 µm. The Vencedor cells were longer foravailable herbage and extrusa in relation to Aruana. For availableherbage, 45% from 500 to 900 µm and 55% from 900 to 1500 µmand for extrusa, 53.5% from 300 to 700 µm and 46.5% from 700 to900 µm.The Aruana extrusa fractions had smaller particles when comparedto those of Vencedor. Particle size along with SCL cell length,possibly indicates a higher fragility for Aruana. Observationsdemonstrated that the Aruana leaf structure was less rigid than thatof Vencedor (Fig. 1a and Fig. 1d) after 48 h incubation.The structures in the Vencedor residue were kept bound to theepidermis (i.e.; BS, VAS and SCL) (fig. 1b), this reduced thesusceptibility of BS cell walls to enzymatic hydrolysis and thusreduced the extent and rate of digestion. Bowman and Firkins (1993)suggested that the differences in the colonization rate of particles bybacterium particle-associate may account for differences in the rateof fiber digestion.The Aruana BS cells were highly colonized and degraded, and insome residue fractions showed xylem secondary wall exposition (Fig.1e). Comparing the Aruana undegraded BS to those of Vencedorwas a uniform colonization in the Vencedor BS was observed onlyat the cut end region (Fig. 1c) while for the Aruana it took place forthe whole extenuation.Session 17 - Forage Quality 17-58Observations indicate that a better medium lamells dissolution occurredin the Aruana residue fraction. This can be further demonstrated by thespread of the SCL cells from the SCL strands to the medium, being themost colonized and some showing a destroyed pattern (Fig. 2f).The qualitative studies parameters from the digestion residues, since itschemical origin or the tissue proportion seem not to indicate a higherfragility of the Aruana as compared to the Vencedor. On the other handthe SCL cell measurements indicate that the physical action of biting/masticating increase the total colonization area by microorganisms ofAruana when compared to the Vencedor.REFERENCESAkin, D.E. and Robinson, E.L. 1982. Structure of leaves and stems ofarrowleaf and crimson clovers as related to in vitro digestibility. CropSci. 22:24-29.Bowman, J.G.P. and Firkins, J.L. 1993. Effects of forage species andparticle size on bacterial cellulolytic activity and colonization in situ. J.Anim. Sci. 71:1623-1638.Daykin, M.E. and Hussey, R.S. 1985. Staining and histopathologicaltechniques in nematology. Pages 39-48 in K.R. Barker, C.C. Carter andJ.N. Sasser eds. An advanced treatise on Meloidogyne; Methodology.Vol. II. Raleight, NC, North Carolina University Graphics.Laredo, M.A. and Minson, D.J. 1975. The effect of pelleting on thevoluntary intake and digestibility of leaf and stem fractions of threegrasses. Br. J. Nutr. 33:159-150.Santos, J.M. dos. 1995. Microscopia de varredura aplicada às ciênciasbiológicas. Funep, FCAV/UNESP, Jaboticabal, 27p.Tilley, J.M.A. and Terry, R.A. 1963. A two-stage technique for the invitro digestion of forage crops. J. Brit. Grassl. Soc. 18:104-111.Wilson, J.R. and Kennedy, P.M. 1996. Plant and animal constraints tovoluntary feed intake associated with fibre characteristics and particlebreakdown and passage in ruminants. Aust. J. Agric. Res. 47:199-225.Figure 1Scanning electron micrographis of chewed leaf blades incubated 48h in vitro for Panicum maximum (a-c) cultivar ‘Vencedor’ and (d-f)cultivar ‘Aruana’, a. digestion residue (x 58), b. connected structuresresidues (x 800) and c. colonized bundle sheath cell cut end (x 2500),d. digestion residue (x 60), e. residue showing xylem secondary wall(x 800 and f. sclerenchyma cell (x 3800).Figure 2Scanning electronmicrographs of Panicummaximum cultivar Aruana leafblades incubated 48 h in vitro:a. digestion residue ( x 60), b.residue showing xylemsecondary wall ( x 800) and c.sclerenchyma cell (x 3800).CULTIVARSVariables Vencedor Aruana SD% of Dry MatterCrude protein 9.8 10.5 0.8Neutral detergent fiber 73.9 74.7 2.3Acid detergent fiber 34.5 37.0 3.4Lignin 4.3 3.9 1.4Tissue proportions (%)Abaxial epidermis 9.8b 10.9a 0.3Adaxial epidermis 16.7b 18.6a 0.5Bundle sheat 32.0a 28.1b 0.6Sclerenchyma 1.0 1.0 0.1Vascular bundle 3.6 3.1 0.2Mesophyll 36.5 39.2 1.1a, b, Different letters in rows indicate significant differences (P<0.05).Table 1Chemical composition and tissue proporations in leaf blades crossof Pannicum maximum cultivars ‘Vencedor’ and ‘Aruana’.

Qualitative Parameters of Two Cultivare of Panicum Maximum, jacq. Under Grazing

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Qualitative Parameters of Two Cultivare of Panicum Maximum, jacq. Under Grazing

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