A trial was designed to test the effect of herbage allowance (HA) on live-weight gain (LWG) and grazing behavior of heifers during spring as part of a combined field-modeling research programme. Low HA (L) and high HA (H) of 2.5 and 5.0 kg DM herbage mass 100 kg animal LW-1day-1 were fed respectively. H animals grazed longer and achieved a higher LWG than L (P \u3c 0.05). H animals left a higher residual pasture (P \u3c 0.051) with a significantly (P \u3c 0.05) higher content of green, clover, non-lamina and petiole of a higher digestibility and NSC, with a lower NDF content. The significance of some factors involved in these results on intake and diet selection are discussed in relation to the predictability of animal performance

Auza, N. J.

Di Croce, F.

Gonzalez, F.

Hodgson, J.

Machado, Claudio F.

Morris, S. T.

Wade, M. H.

Zeballos, H.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XIX International Grassland Congress Effects of Herbage Allowance upon Animal Performance and Grazing Behavior of Strip-Grazed Heifers Claudio F. Machado Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina F. Di Croce Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina F. Gonzalez Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina H. Zeballos Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina N. J. Auza Universidad Nacional del Centro de la Provincia de Buenos Aires, Argentina 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/19/8/7 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 Claudio F. Machado, F. Di Croce, F. Gonzalez, H. Zeballos, N. J. Auza, M. H. Wade, S. T. Morris, and J. Hodgson This event is available at UKnowledge: https://uknowledge.uky.edu/igc/19/8/7 ID # 08-09EFFECTS OF HERBAGE ALLOWANCE UPON ANIMAL PERFORMANCE ANDGRAZING BEHAVIOR OF STRIP-GRAZED HEIFERSC. F. Machado1, F. Di Croce1, F. Gonzalez1, H. Zeballos1,2, N.J. Auza1, M.H. Wade1, S.T. Morris3and J. Hodgson31Facultad de Ciencias Veterinarias UNCPBA, Pinto 399, 7000, Tandil, Argentina,cmachado@vet.unicen.edu.ar, 2Escuela Educación Agraria N°1 Dr. Ramón Santamarina, Tandil,Argentina,3 Massey University, Palmerston North, New ZealandAbstractA trial was designed to test the effect of herbage allowance (HA) on live-weight gain(LWG) and grazing behavior of heifers during spring as part of a combined field-modelingresearch programme. Low HA (L) and high HA (H) of 2.5 and 5.0 kg DM herbage mass 100 kganimal LW-1day-1 were fed respectively. H animals grazed longer and achieved a higher LWG thanL (P<0.05). H animals left a higher residual pasture (P<0.051) with a significantly (P<0.05) highercontent of green, clover, non-lamina and petiole of a higher digestibility and NSC, with a lowerNDF content. The significance of some factors involved in these results on intake and dietselection are discussed in relation to the predictability of animal performance.Keywords: herbage allowance; LWG, grazing behavior; heifersIntroductionAnimal performance at grazing is dependent upon levels of daily herbage intake. Thefactors which determine these levels may arise from the animal, the pasture or the physicalenvironment. The complexity of the grazing situation demands approaches in addition totraditional experimentation and simulation models have been suggested to this end (Bywater andCacho 1994; Dove 1996). In Argentina, high producing temperate grasses tend to be morevariable in structure and composition than those of UK or New Zealand. Also in Argentina, Galli(1994) has used a combined modeling-field research approach in order to obtain an understandingof some pasture and animal factors which affect herbage intake. The present report is the first of aseries with the objective of studying a range of factors, particularly of the sward, which may helpto determine herbage intake and performance under different levels of herbage allowance (HA).Material and MethodsDuring spring of 1999, 18 heifers (253±4.8 kg LW) were allotted to a Low HA (L) andhigh HA (H) of 2.5 and 5.0 kg DM herbage mass 100 kg animal LW -1day-1. The trial was carriedout in Tandil, Argentina.  Fifty rising plate meter (RPM) measurements previously calibrated(Earle and Mc Gowan 1979) were taken daily pre- and post-grazing and used to estimate biomassand then dry matter intakes (DMI). Both treatments were allocated to pasture of similarcharacteristics containing ryegrass (Lolium perenne) but dominated by red clover (Trifoliumpratense).  Animals were strip-grazed and moved to a fresh strip daily with no  back-grazing or re-grazing of experimental areas at any time. A 15 day pre-experimental period was used and actualmeasurements were taken over a  42-day period. Animals were de-wormed 48 h prior to allocationto treatments. On day 39, quadrats (0.1 m2) were cut at ground level pre- and post-grazing frompreviously selected and homogeneous tagged areas of 1 m2 (5.treatment-1). Samples were sealed inpolythene bags and sorted into species, green-dead proportion, lamina and petiole (L&P) and non-L&P within the green component. Total DM was estimated separately by oven-drying at 60 °C for48 h. A site adjacent to each pre- and post-grazing quadrat, representing pasture of similarcharacteristics, was also sampled and refrigerated on site. These samples were freeze-dried andground in a mill (1 mm screen) and analysed for in vitro digestibility (Dig), CP, NDF, ADF, NSC.At fortnightly intervals, ten pre-grazing hand-plucked pasture samples per treatment werecollected to be also nutritionally assessed as described above. Animals were weighed fortnightlywithin 1 h of removal from pasture, and at start and end of the trial after a 12 h fasting period.Twice during the trial and related to the pasture measurement (days 32 and 39), 24 h grazingbehavior and biting rates were recorded (Jamieson and Hodgson 1979). Data were statisticallyanalysed by ANOVA with a repeated measures design for LWG. A completely randomised designwas used for analysing separately the pre- and post-grazing herbage component and nutrientlevels.Results and DiscussionThe average pre-grazing pasture quality traits measured during the trial were 0.69, 0.39,0.17 and 0.11 for Dig, NDF, CP and NSC respectively there being no difference betweentreatments.  The calibration equation for the RPM on herbage mass (HM) (DM.ha-1): was:   HM:61.8 x + 661.8    R2 :0.72  P<0.01. Dry matter intake (DMI) as estimated using the RPM were3.5±0.14 and  6.5±0.29 kg.day-1 head-1 for L and H treatments, respectively. On day 39, DMI of8.4±2.6  (SE) and 5.1±1.2  kg DM. head-1 d-1  were  estimated for H and L treatments,respectively. No significant differences were found pre-grazing for HM, plant components ornutrient composition (Table 1). However, H left a  higher   pasture   residual   post-grazing(P<0.051)  with  a  significantly (P<0.05) higher content of green, clover, L&P of a higherdigestibility and NSC, and a lower NDF.  While these results may be explained in terms of agradation in herbage quality as grazing down occurs, clearly there is a possibility that selectivegrazing took place here. This will be investigated using two techniques: microscopic analysis offaeces and n-alkane analysis in this trial. The last mentioned technique may also provide anestimate of the levels of herbage intake in individual animals. Animals at high allowance grazedlonger and achieved a higher LWG (Table 2), which is in agreement with (Jamieson and Hodgson1979). Although some restriction was operating at H group due probably to the low residual HMand high dead content (Table 1), LWG was important and this group achieved a higher degree ofherbage utilisation (52%) than L (36%).  The factors that determine the selection of plantcomponents or nutrients are not well understood (Hodgson 1990). Similarly, (Hodgson 1984)mentioned that no single parameter is likely to provide a reliable basis for predicting animalperformance unless it is applied within well-defined constraints, which highlights the need toidentify locally how different sward conditions contribute to the predictability of intake and LWGin beef systems.ReferencesBywater AC. and Cacho OJ. (1994). Use of simulation models in research. Proceedings of theNew Zealand Society of Animal Production 54:403-12.Dove H. (1996). Constraints to the modelling of diet selection and intake in the grazing ruminant.Australian Journal of Agricultural Research 47:257-75.Earle D. and Mc Gowan A. (1979).   Evaluation and calibration of an automated rising platemeter for estimating dry matter yield of pasture.  Australian Journal of Experimental Agricultureand Animal Husbandry 19:337-43.Galli JR. 1994. CONPAST: un modelo de simulación del comportamiento ingestivo y consumode bovinos en pastoreo. Tesis de Magister Scientiae, U.N.MdP. Argentina.Hodgson J. (1984). Sward conditions, herbage allowance and animal production. Proceeding ofthe New Zealand Society of Animal Production 44:99-104.Hodgson J. (1990). Grazing management: Science into practice. Longman Handbooks inagriculture, Longman Scientific and Technical co-published with John Wiley. New York. 203 p.Jamieson WS and Hodgson J. (1979). The effect of daily herbage allowance and swardcharacteristics upon the ingestive behavior and herbage intake of calves under strip-grazingmanagement. Grass and Forage Science 34:261-71.Table 1 - Effect of herbage allowance (High=H and Low=L) on pre- and post-grazingnutrient and component compositionL H #p.s.e SignificancePRE-GRAZING    Herbage mass (kg DM.ha-1) 3557.5 3927.5 453.6 NS   Components NS          Dead  (DF) 0.33 0.34 0.06 NS          Green (DF) 0.66 0.65 0.06 NS          Clover + 0.58 0.58 0.06 NS          Grass + 0.08 0.07 0.02 NS          Lamina&petiole + 0.19 0.21 0.03 NS          Non-Lamina&petiole + 0.47 0.43 0.04 NS   Nutrients         Dig   (DF) 0.689 0.658 0.013 NS         NDF (DF) 0.353 0.375 0.016 NS         CP   (DF) 0.169 0.159 0.010 NS         NSC (DF) 0.080 0.088 0.014 NSPOST-GRAZINGHerbage mass (kg DM.ha-1) 1707.5 2515 235.3 &   Components          Dead   (DF) 0.84 0.53 0.04 *          Green  (DF) 0.15 0.46 0.04 *          Clover (+) 0.08 0.40 0.03 *          Grass + 0.06 0.06 0.01 NS          Lamina&petiole + 0.02 0.04 0.009 NS          Non-Lamina&petiole + 0.12 0.42 0.03 **   Nutrients          Dig   (DF) 0.505 0.585 0.020 *          NDF (DF) 0.616 0.504 0.027 *          CP   (DF) 0.099 0.113 0.007 NS          NSC (DF) 0.045 0.073 0.006 *# Pooled standard errorDF decimal fraction of dry matter+ Contribution to green componentNS no significant difference (P>0.1)& P<0.1* P<0.05** P<0.01Table 2 -  Effect of herbage allowance (High=H and Low=L) on LW, gut fill loss, LWG andgrazing behavior of heifersL H #p.s.e SignificanceInitial LW (kg.head-1) 249 257 6.9 NSFinal gut fill loss (% full LW in 15 h) 0.07 0.07 0.006 NSFull LWG (kg.head-1day-1) 0.58 0.79 0.05 **15 h empty LWG (kg.head-1day-1) 0.49 0.76 0.07 **Biting rate (bites.min-1) 37.8 35.0 2.4 NSGrazing time(min) 422.6 468.3 12.9 *Ruminating time (min) 379.1 397.2 12.9 NS Idling time (min) 613.2 574.4 17.5 *# Pooled standard errorAll activities expressed as minutes per dayNS no significant difference (P>0.1)* P<0.05** P<0.01

Effects of Herbage Allowance upon Animal Performance and Grazing Behavior of Strip-Grazed Heifers

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=4107&context=igc

Effects of Herbage Allowance upon Animal Performance and Grazing Behavior of Strip-Grazed Heifers

Abstract

Similar works

Full text

Available Versions

University of Kentucky