Ferris, C. P.

Mayne, C. S.

Porter, M. G.

Yan, Tianhai

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Effects of Grass Growth Stage on Metabolisable Energy Concentration of Fresh Grass Tianhai Yan Agri-Food and Biosciences Institute, UK C. P. Ferris Agri-Food and Biosciences Institute, UK M. G. Porter Agri-Food and Biosciences Institute, UK C. S. Mayne Agri-Food and Biosciences Institute, UK 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/21/2-3/1 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House 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. 瞯 ]396　 瞯 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　Grasslands/Rangelands Resources and Ecology ——— Soil Quality and Plant NutritionEffects of grass growth stage on metabolisable energy concentration of fresh grassT . Y an , C . P . Ferris , M . G . Porter and C . S . MayneA gri‐Food and Biosciences Institute , H illsborough , County Down , Northern I reland BT２６ ６DR , UK , E‐mail : T ianhai .yan＠ af bini .gov .ukKey words : cattle , chemical composition , fresh grass , grass maturity , metaboliisable energyIntroduction Fresh grass is the most important forage for ruminant animals across the world , whilst it is widely recognised thatthe nutritive value of fresh grass varies considerably with stage of grow th . There is little information in the literature on therelationship between stage of grow th and nutritive value within the same sward . The objective of the present study was todevelop a prediction method for ME concentration of fresh grass from chemical composition .Materials and methods Fresh herbage was produced from the primary grow th of perennial ryegrass swards . Swards wereharvested daily at １３ .００ h , for a ７ week period , from early grow th to late maturity , and offered to ２ groups of dry , non‐pregnant dairy cows at a maintenance level of energy intake . Fresh herbage was offered twice daily with one portion given at１４ .００ h and the other stored at ４ ℃ and offered at ０９ .００ h the following day . The first group of ４ cows was on treatment for ４weeks , with total collection of faeces and urine from week ２ to ４ . During the ４th week , grass for the first group was alsooffered to the second group of ４ cows , and faeces and urine collected for the second group for the last ３ days . Measurementswith the second group of cows continued until the end of week ７ . A similar procedure was repeated for the first regrow th fromthe same swards . Grass ME concentration was calculated using methane energy output , predicted from the equation developedusing the same dataset with the present study ( Yan , ２００８) . Weekly mean data were used to examine effects of stage of grassgrow th on ME concentration .　 　 　 　 Figure 1 Relationship between A DF and ME content inf resh grass .Results and discussion Data obtained during week４ ( overlap period) were used to evaluate effectsof cow group . There was no significantdifference in nutrient digestibility between thetwo groups . As expected , increasing grassmaturity from week １ to ６ increased DM (１７６ to２３６) , ADF (２２５ to ２９２) and NDF (４７４ to ５４２ )contents ( g / kg DM ) , while reducing CP (１４５ to６９) , lipid ( ３７ to １７ ) and GE contents ( １８畅５ to１８畅１ MJ/ kg DM ) . Consequently , digestible OMin total DM ( DOMD ) and ME content ( １２ .４ ,１２ .２ , １２ .２ , １１ .８ , １１ .５ and １０ .９ MJ/ kg DM )decreased from week １ to ６ . In the UK energyrationing system ( AFRC , １９９３) , DOMD is usedto predict ME concentration for forage ( ME( MJ/ kg ) ＝ １６ DOMD ( kg / kg ) ) . The samerelationship developed using the present datasetindicates a slightly lower coefficient (１５ .５ , R２ ＝ ０畅７１） ．However , measurement of DOMD requires assessment of digestibility , which is not practical in commercial situations . Analternative option is to predict ME concentration from the chemical composition of the fresh herbage . In the present study , MEconcentration was positively related to ( P ＜ ０ .００１ ) CP ( R２ ＝ ０畅６９） and lipid ( R２ ＝ ０畅６５） concentrations , and negativelyrelated to ADF concentration ( Figure １ , P ＜ ０畅００１ ) . Using a stepwise technique , a strong relationship was developed topredict ME concentration ( Eq . [ １] ) , where WSC ＝ water soluble carbohydrates ; unit for GE and ME is MJ/ kg DM and forother nutrient g / kg DM .ME ＝ ２ .５８７GE ＋ ０ .０２３DM‐０ .０５５ADF‐０ .１３３Lipid‐０ .０１４WSC‐１９ .５( R２ ＝ ０ .９３ ,s .e .＝ ０ .２０ ,P ＜ ０ .００１ ) [１ ]Conclusions The ME concentration of fresh grass was significantly related to DOMD and CP , lipid and ADF concentration . Avery strong relationship was developed to predict grass ME concentration from chemical composition .ReferencesAFRC , (１９９３) . Energy and protein requirements of ruminants . CAB International , W alling f ord , Oxon , UK .Yan , T . and Mayne , C . S . (２００８) . Prediction of methane emission of dairy cows offered fresh grass at maintenance feedinglevel . Presented in the p resent Proceedings .0 13 . s • '§ i 12 C: Q y = -0.017x+l6.3 , R2 = 0.69 ., bl) (J ~ 0 ;:::; 0 11 (J 6 µi ;8 10 200 250 300 350 ADF concentration (g/kg OM) 

Effects of Grass Growth Stage on Metabolisable Energy Concentration of Fresh Grass

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Effects of Grass Growth Stage on Metabolisable Energy Concentration of Fresh Grass

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