Cavali, J.

de Souza, J. C.

Fernandes, H. J.

Paiva, L. M.

Paulino, M. F.

Porto, M. O.

Rocha, A. A.

Silva, A. G.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Nutritional Parameters of Grazing Calves in Milking Phase 2: Protein Metabolism H. J. Fernandes State University of Mato Grosso do Sul, Brazil A. A. Rocha Federal University of Viçosa, Brazil J. Cavali Federal University of Viçosa, Brazil A. G. Silva Federal University of Viçosa, Brazil M. F. Paulino Federal University of Viçosa, 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/21/9-1/30 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. Presenter Information H. J. Fernandes, A. A. Rocha, J. Cavali, A. G. Silva, M. F. Paulino, L. M. Paiva, M. O. Porto, and J. C. de Souza This event is available at UKnowledge: https://uknowledge.uky.edu/igc/21/9-1/30 瞯 ]46　 瞯 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅱ 　Grasslands/Rangelands Production Systems——— Livestock Production SystemsNutritional parameters of grazing calves in milking phase 2 : protein metabolismH .J .Fernandes1 ,2 ; A .A .Rocha2 ; J .Cavali2 ; A .G .Silv a2 ; M .F .Paulino2 ; L .M .Paiva1 ,2 ; M .O .Porto2 and J .C .Souz a31 S tate University o f Mato G rosso do Sul / FUNDECT ,A quidauana‐CERA road ,Km 12 ,A quidauana ,MS ,79200‐000 ,Braz il ,email : ike .f ernandes＠ hotmail .com ; 2 A nimal Science Department ,Federal University o f V i毕osa ,V i毕osa ,MG ,36570‐000 ;3 Federal University o f Parana .Key words : calves ,milking ,grazing ,protein supplement ,nutritional parametersIntroduction Approximately ９５％ of the beef production in Brazil came from grazing animals .Despite this ,there are a smallnumber of studies about the physiological effects of the interaction between pasture conditions ,animal life phase and fedsupplement .Protein supplementation has been the main tool used to increase the productive capacity of animals because itpotential to also increase the energy input to the animal ,when improving the pasture digestibility .In young bovine ,however ,little has been studied about the adequate protein levels in the supplement in order to increase animal performance ,withoutallowing that protein excess in the diet could lead to waste and even environmental problems .The excess protein in bovine dietis metabolized by the liver ,transformed into urea ,and then eliminated into the urine ,could to form potentially water‐pollutingcompounds .The objective of this study was to evaluate the responses of the protein metabolism of grazing nursing calves todifferent protein levels supplementation in tropical pastures in Brazil .Materials & Methods This work was carried out in the region of Vi毕osa ,MG ,Brazil .A total of ５２ Nellore beef calves with initialage of １００ days and initial weight of １２９ kg were used in the study .The animals with their mothers were separated into fourgroups that received different concentrate supplement in a �Creep‐Feeding" system .The animals were raised in Brachiariadecumbens Stapf pastures .The evaluated supplements were : ad libtum mineral salt ( control treatment ) ,and rations with ８ ,２２and ３２％ of crude protein ( CP) formulated with corn and soybean meal ,daily fed at １ .２ kg / animal . The pastures were sampledevery ２８ days ( McMeniman ,１９９７ ) .On the ６５th day of the experiment ,spot urine samples were collected to determine the dailyurea excretion as suggested by Valadares et al .( １９９９ ) .Immediately after urine collection ,blood samples were collected fromeach animal ,centrifuged and analyzed for plasmatic urea level .The significance level used was ５％ .Results & Discussion Supplementation with concentrated rations with up to ２２％ of CP had no effect on the plasmatic urea or N‐urea levels ( Table １ ) . However ,concentrated supplements with ３２％ of CP increased plasmatic urea levels . This can beexplained by an action of the liver that ,seeking to metabolize a possible excess of diet protein ,increases the urea production .This urea is carried ,through blood ,to the kidneys ,and eliminated from the body via urine .Although the differences observed indaily urea excretion in the urine ( expressed as total excretion per day or per kg of live weight ) are not significant , thesupplementation with rations with ３２％ of CP produced up to ５０％ more urea excreted via urine .Table 1 Levels and coe f f icient o f v ariation o f p lasmatic urea ( PU) and N‐urea ( PNU) ,and daily excretion o f urea in totalurine (UU) and per kg o f live weight (UUlw ) .Level of Protein in Supplements１ 骀Salt ８％ CP ２２％ CP ３２％ CP CV ( ％ )PU２ I２５ 排.０４b ２０ 浇.７３b ２３ 创.６９b ３５ �.６９a ３７ 殮.９PNU２ l１１ 排.６７b ９ Ζ.６６b １１ 创.０４b １６ �.６３a ３７ 殮.９UU３ R１６ 乔.２５a １８ 靠.２１a １６ 抖.９１a ２５ �.０３a ５９ 殮.９UUlw４ 亖９０ 乔.６９a ９５ 靠.１８a ８９ 抖.６６a １２１ 排.６０a ４７ 殮.３１ Means in the same row followed by the same letter are not significantly different by the t test ( p ＜ ０ .０５) ; ２ mg/ dl ; ３ g / day ; ４ mg/ kg LW/ day .Larger urine excretions of this metabolite were expected because of the largest plasmatic urea levels in these animals .In thiscase ,the lack of significance in the observed differences can be explained by the high coefficient of variation ( CV ) of thischaracteristic ,here associated to the individual variability observed among animals .Conclusion The use of concentrated supplements with protein level below ３２％ of CP did not increase the urea excretion ingrazing nursing calves ,in Brazilian autumn conditions .ReferencesMcMeniman ,N .P .１９９７ .Methods of estimating intake of grazing animals . In : Reuni本o Anual da Sociedade Brasileira deZootecnia ,３４ ,Juiz de Fora .A nais . . .Juiz de Fora : SBZ . p .１３１‐１６８ .Valadares ,R .F .D . ; Broderick ,G .A . ; Valadares Filho ,S .C .et al . ,１９９９ .Effect of replacing alfalfa silage with high moisturecorn on ruminal protein synthesis estimated from excretion of total purine derivatives . Journal o f Dairy Science ８２ ( １１ ) :２６８６‐２６９６ .

Nutritional Parameters of Grazing Calves in Milking Phase 2: Protein Metabolism

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Nutritional Parameters of Grazing Calves in Milking Phase 2: Protein Metabolism

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