<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1659-1321</journal-id>
<journal-title><![CDATA[Agronomía Mesoamericana]]></journal-title>
<abbrev-journal-title><![CDATA[Agron. Mesoam]]></abbrev-journal-title>
<issn>1659-1321</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Costa Rica]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1659-13212017000300643</article-id>
<article-id pub-id-type="doi">10.15517/ma.v28i3.26897</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Suplementación con hidroxianálogo de metionina: efecto sobre el desempeño productivo en vacas lecheras]]></article-title>
<article-title xml:lang="en"><![CDATA[Supplementation of methionine hydroxy analog: effect on dairy cow performance]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Vargas-Villalobos]]></surname>
<given-names><![CDATA[Omar]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Cambronero-Castro]]></surname>
<given-names><![CDATA[Oscar]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Elizondo-Salazar]]></surname>
<given-names><![CDATA[Jorge Alberto]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Costa Rica  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>CR</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Costa Rica  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>CR</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Universidad de Costa Rica Facultad de Ciencias Agroalimentarias Estación Experimental Alfredo Volio Mata]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>CR</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2017</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2017</year>
</pub-date>
<volume>28</volume>
<numero>3</numero>
<fpage>643</fpage>
<lpage>655</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S1659-13212017000300643&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S1659-13212017000300643&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S1659-13212017000300643&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen Suplementar vacas lecheras con dietas bajas en proteína con aminoácidos específicos, es una estrategia promisoria para contrarrestar el potencial efecto negativo de una deficiencia de proteína metabolizable en la productividad. El objetivo del presente estudio fue cuantificar el desempeño productivo de vacas lactantes y la calidad de la leche ante dos dietas con diferente concentración de proteína cruda (PC) y el suministro de hidroxianálogo de metionina (HMTBA). El estudio se realizó en una finca lechera comercial en la localidad de Alfaro Ruiz, Alajuela, Costa Rica, durante el primer semestre del 2014. Veinte vacas multíparas de la raza Holstein bajo un sistema de pastoreo, fueron agrupadas de acuerdo con los días de lactancia y número de parto. Dos dietas con diferentes concentraciones de PC (alto 16,6% y estándar 15,8%) con o sin inclusión de HMTBA (25 g/tm) fueron estudiadas en un arreglo factorial 2x2. No se encontraron efectos significativos (P&gt;0,05) sobre la producción de leche, leche corregida al 4% de grasa, grasa láctea, proteína láctea, lactosa, sólidos totales o nitrógeno ureico en leche (NUL) al incluir HMTBA. Alimentar las vacas con alta concentración de PC incrementó significativamente (P&lt;0,05) la concentración de NUL de 18,33 a 20,70 mg/dl. Suplementar HMTBA a vacas en pastoreo no tuvo una respuesta significativa (P&gt;0,05) en las diferentes variables estudiadas y tampoco se encontró una retribución económica, debido a que no se incrementó la cantidad de leche ni los sólidos totales.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract Supplementing dairy cows with low in protein diets with specific amino acids is a promising strategy to counteract the potential negative effect of metabolizable protein deficiency on productivity. The objective of this study was to quantify the productive performance of lactating dairy cows and their milk quality when they are offered two diets with different crude protein (CP) concentration and when they are supplemented with methionine hydroxy analog (HMTBA). This study was carried out in a commercial dairy farm located in Alfaro Ruiz-Alajuela, Costa Rica, during the first semester of 2014. Twenty multiparous Holstein cows under a grazing system were grouped according to days in lactation and calving number. Two diets with different concentrations of CP (high 16.6% and 15.8% standard), with or without inclusion of HMTBA (25 g/TM) were studied in a 2x2 factorial arrangement. No significant effects (P&gt;0.05) on milk production, 4% fat corrected milk, milk fat, milk protein, lactose, total solids or milk urea nitrogen (MUN) were found when including HMTBA. Feeding cows with high CP concentration significantly increased (P&lt;0.05) MUN concentration from 18.33 to 20.70 mg/dl. Supplementing HMTBA to grazing cows did not have a significant response (P&gt;0.05) regarding the different variables, and no financial return was found due to the fact that neither total milk production nor total solids were increased.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[aminoácidos esenciales]]></kwd>
<kwd lng="es"><![CDATA[análogo de metionina]]></kwd>
<kwd lng="es"><![CDATA[sólidos lácteos]]></kwd>
<kwd lng="es"><![CDATA[producción de leche]]></kwd>
<kwd lng="en"><![CDATA[essential amino acids]]></kwd>
<kwd lng="en"><![CDATA[methionine analog]]></kwd>
<kwd lng="en"><![CDATA[milk solids]]></kwd>
<kwd lng="en"><![CDATA[milk production]]></kwd>
</kwd-group>
</article-meta>
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