The objective of this study was to assess the effect of Italian ryegrass (Lolium multiflorum Lam.) sward height on grazing activities. The experiment was carried out at the Research Station of Universidade Federal do Rio Grande do Sul, Brazil. Yearling no-castrated male lambs behavior was assessed in terms of diurnal grazing, ruminating and idling time in three periods: 27 September 11 and 25 October. Sward surface height was monitored using a sward stick and samples of 0.25 m2 were cut to ground level to estimate herbage and leaf lamina mass. The experiment was carried out in a randomised block design with three replications of four treatments: sward surface heights (5, 10, 15 and 20 cm). Grazing time and ruminating time were somewhat interchangeable, decreasing grazing time and increasing ruminating time with increasing sward surface heights. Idling time remained relatively constant. Sward height showed a small effect on biting rate

de F. Carvalho, Paulo C.

Poli, C. H. E. C.

Pontes, L. S.

Ribeiro Filho, H. M. M.

Silveira, E. O.

Soares, A. B.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XIX International Grassland Congress The Effect of Sward Surface Height on Sheep Grazing Activities Paulo C. de F. Carvalho Universidade Federal do Rio Grande do Sul, Brazil E. O. Silveira Universidade Federal do Rio Grande do Sul, Brazil L. S. Pontes Universidade Federal do Rio Grande do Sul, Brazil C. H. E. C. Poli Universidade Federal do Rio Grande do Sul, Brazil A. B. Soares Universidade Federal do Rio Grande do Sul, Brazil See next page for additional authors Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/19/7/11 This collection is currently under construction. The XIX International Grassland Congress took place in São Pedro, São Paulo, Brazil from February 11 through February 21, 2001. Proceedings published by Fundacao de Estudos Agrarios Luiz de Queiroz This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. Presenter Information Paulo C. de F. Carvalho, E. O. Silveira, L. S. Pontes, C. H. E. C. Poli, A. B. Soares, and H. M. M. Ribeiro Filho This event is available at UKnowledge: https://uknowledge.uky.edu/igc/19/7/11 ID # 07-12 THE EFFECT OF SWARD SURFACE HEIGHT ONSHEEP GRAZING ACTIVITIESP.C. de F. Carvalho1, E.O. Silveira1, L.S. Pontes1, C.H.E.C. Poli1, A .B. Soares1 and H.M.M.Ribeiro Filho11D.P.F.A.,Agronomia – UFRGS, Porto Alegre, Brasil. paulocfc@vortex.ufrgs.brAbstractThe objective of this study was to assess the effect of Italian ryegrass (Lolium multiflorumLam.) sward height on grazing activities. The experiment was carried out at the Research Stationof Universidade Federal do Rio Grande do Sul, Brazil. Yearling no-castrated male lambsbehavior was assessed in terms of diurnal grazing, ruminating and idling time in three periods: 27September 11 and 25 October. Sward surface height was monitored using a sward stick andsamples of 0.25 m2 were cut to ground level to estimate herbage and leaf lamina mass. Theexperiment was carried out in a randomised block design with three replications of fourtreatments: sward surface heights (5, 10, 15 and 20 cm). Grazing time and ruminating time weresomewhat interchangeable, decreasing grazing time and increasing ruminating time withincreasing sward surface heights. Idling time remained relatively constant. Sward height showeda small effect on biting rate.Keywords: Italian ryegrass, Lolium multiflorum Lam., grazing time, ruminating time, idlingtime.IntroductionSeveral studies (e.g. Penning, 1986) demonstrate that ingestive behavior, live weight gain,wool production and ovulation rate are affected by forage allowance and sward height. Swardheight is one of the most important pasture characteristics that affect intake of grazing animals.As sward height decrease, there is a direct influence on grazing time, number of bites and bitemass (Hodgson, 1981), the three major constituents of daily intake on pastures. Recently, it hadbeen an agreement that variables concerning intake at lager temporal scales, particularly grazingtime, need to be more studied. The objective of this study was to assess the effect of Italianryegrass sward height on grazing, ruminating and idling time, and biting rate.Material and MethodsThe experiment was carried out at the Experimental Station of Universidade Federal doRio Grande do Sul, Brazil (30º 05’22’’S and 51º39’08’’W). Eleven yearling not castrated lambs(testers) of approximately 35 kg of livewheight grazed an Italian ryegrass (Lolium multiflorumLam.) sward on a continuous variable stocking. Put-and-take animals were used to regulate thesward surface height (SSH). The experiment was carried out in a randomised block design withthree replications of four treatments: 5, 10, 15 and 20 cm of SSH. The sward surface height(SSH) was randomly measured using a sward stick (Barthram, 1986). One hundred readings ineach plot were taken in the following day of the grazing behavior assessment. Herbage mass wasestimated by cutting five 0.25 m2 quadrats to ground level with shearing scissors in each plot inthe same day of the SSH measurements. After cutting, the samples were dissected into categoriesfor morphology (leaf lamina, sheath, stem, and dead tissue) and species. The samples, then, weredried in a draught oven at 65oC and weighed individually. The distribution of individual animalactivity (grazing, ruminating and resting) was recorded from dawn to dusk of three randomlychosen animals/plot, at intervals of 10 minutes, using the method of Jamieson and Hodgson(1979). Rates of biting were also measured using the 20 bite method of Forbes and Hodgson(1985). The grazing behaviour assessment was carried out in three different periods 27September, 11 and  25 October 1999. Statistical analysis were conducted using generalised linearmodel procedure (GLM) and regression procedure (REG) of the statistical analysis system (SAS,1990).Results and DiscussionThere were significant difference in herbage mass, height and leaf lamina mass betweentreatments (Table 1). There was no significant difference in bulk density among treatments. Asexpected, taller swards had greater herbage and leaf lamina mass, however the differencebetween herbage and leaf lamina mass was also greater for the taller swards.There was a significant effect of the treatments on the distribution of grazing activities (grazing,idling and ruminating time - Figure 1). As sward height decreased, the grazing time increased(Y= 681.710 – 12.2622X, R2 = 0.3530, and P = 0.0002) and ruminating time decreased (Y =45.2182 + 8.8925X, R2 = 0.3789 and P = 0.0001) in linear pattern. It shows that as the swardsurface height decreased the animals allocated more time grazing and less time ruminating. Idlingtime remained relatively constant (Y = 86.6899 + 3.4970X, R2 = 0.0532 and P = 0.1895),regarding sward height as pointed out by Penning et al. (1991). The results confirm observationsmade by Penning (1986) with perennial ryegrass that sward availability has an importantinfluence on distribution of grazing activities. As the sward become shorter the animals decreasethe time spent grazing in order to compensate the reductions in intake. The effort required todetach plant material near the ground in short swards may have restricted bite depth, the majorinfluence on variation in bite weight and intake (Laca et al., 1992). However the results also showthat with Italian ryegrass even in situations with high availability the animals still reduce the timespent grazing and increase the time spent ruminating as the sward height increase. There was nosignificant effect of the treatments on biting rate. (56.1 ±1.70, 52.44 ± 1.50, 56.9 ± 1.77 and 51.8± 2.05  bites/min, P-value=0.2391, for the treatments 5, 10, 15 and 20 cm, respectively).Although biting rate and grazing time are often regarded as the primary compensating responsesof the animal to limitations in intake (Hodgson,1981), increases in grazing time were notfollowed by an increase in biting rate to maintain the intake rate. The variations in biting ratewere certainly influenced by the sward structure. The low leaf density in treatments of greaterheight and the difficulties of prehensions (Barthram and Grant, 1994) in short swards couldcompensate the low variance found between treatments. In taller swards the pseudostems andstems may have acted as a deterrent to deep grazing penetration within the sward canopy(Dougherty et al.,1992). In this case, plant structure would be an important factor. It wasobserved a greater proportion of stems in the taller treatments. In conclusion, it can be seen thatthe sward structure of Italian ryegrass has and important influence on the ingestive behaviour.The sward height have a direct influence on the distribution of grazing activities, even at greaterheights (above 15 cm), however biting rate seems to be more strongly influenced by theproportion of pseudostems and stems than sward height.ReferenceBarthram, G.T. (1986). Experimental techniques: The HIFRO sward stick. Biennial Report1984-1985, Hill Farming Research Organisation, Penicuik, pp. 29-30.Barthram, G.T., and Grant S.A. (1994). Defoliation of ryegrass-dominated swards by sheep.Grass and Forage Science,  39: 211-219.Forbes, T.D.A., and Hodgson J. (1985). Comparative studies of the influence of swardconditions on the ingestive behaviour of cows and sheep. Grass and Forage Science,  40: 69-77.Hodgson, J. (1981). Variations in the surface characteristics of the sward and the short-term rateof herbage intake by calves and lambs. Grass and Forage Science, 36: 49-57.Jamieson, W.S. and Hodgson J. (1979)  The effects of variation in sward characteristics upon theingestive behaviour and herbage intake of calves and lambs under a continuous stockingmanagement. Grass and Forage Science, 34: 273-282.Laca, E.A., Ungar E.D., Seligman N., and Demment M.W. (1992). Effects of sward height andbulk density on bite dimensions of cattle grazing homogeneous swards. Grass and ForageScience,  47: 91-102.Penning, P.D., Parsons A.J., Orr R.J. and Treacher T.T. (1991). Intake and behaviourresponses by sheep to changes in sward characteristics under continuous stocking. Grass andForage Science, 46:15-18.Penning, P. (1986). Some effects of sward conditions on grazing behaviour and intake by sheep.In: Gudmundssun, O. (Ed.) Grazing research at northern latitudes. pp. 219-226.SAS (1990). SAS User’s Guide. SAS Institute, Inc. Cary, NC.Table 1 - Characteristics of Italian ryegrass sward according to the treatments (5, 10, 15 and 20 cm of sward height),averages of three periods 28 September, 12 and 26 October 1999, UFRGS-Eldorado do Sul, Brazil.Intended award surface height (cm)Sward characteristics 5 10 15 20 P-value2Surface height (cm) 4.91 10.19 12.27 17.89 0.0001SEM1 0.40 0.36 0.45 0.52Herbage mass (kg/ha) 918.8 2188.3 2287.6 3751.3 0.0001SEM 112.59 100.01 124.64 145.14Leaf lamina (kg/ha) 230.7 533.1 604.4 715.0 0.0001SEM 30.56 27.1 33.8 39.3Bulk density (mg/cm3) 1.8 2.1 1.8 2.1 0.0527SEM 0.1 0.09 0.12 0.141SEM – Standard error of the means2P-value of the treatment main effectTime (minutes)Sward Height (cm)4 6 8 10 12 14 16 18 20 22Time (minutes)01002003004005006007000100200300400500600700grazingruminatingidlingFigure 1 - Grazing behavior activities (grazing, ruminating and idling time)in relation to sward height.

The Effect of Sward Surface Height on Sheep Grazing Activities

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The Effect of Sward Surface Height on Sheep Grazing Activities

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