<?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>1390-8596</journal-id>
<journal-title><![CDATA[LA GRANJA. Revista de Ciencias de la Vida ]]></journal-title>
<abbrev-journal-title><![CDATA[La Granja]]></abbrev-journal-title>
<issn>1390-8596</issn>
<publisher>
<publisher-name><![CDATA[Universidad Politécnica Salesiana]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1390-85962019000100084</article-id>
<article-id pub-id-type="doi">10.17163/lgr.n29.2019.07</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[EDAD AL PRIMER PARTO E INDICADORES DE EFICIENCIA EN VACAS LECHERAS CON DIFERENTE POTENCIALIDAD PRODUCTIVIDAD EN SISTEMAS A PASTOREO]]></article-title>
<article-title xml:lang="en"><![CDATA[AGE AT THE FIRST CALVING AND EFFICIENCY INDICATORS IN DAIRY COWS WITH DIFFERENT PRODUCTIVE POTENTIAL IN GRAZING SYSTEMS]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Marini]]></surname>
<given-names><![CDATA[Pablo Roberto]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
<xref ref-type="aff" rid="A a"/>
<xref ref-type="aff" rid="A4"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Di Masso]]></surname>
<given-names><![CDATA[Ricardo José]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Nacional de Rosario  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Ecuador</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Universidad Nacional de Rosario  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Argentina</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Universidad Nacional de Rosario  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Argentina</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Universidad Nacional de Rosario  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Argentina</country>
</aff>
<aff id="Af5">
<institution><![CDATA[,Universidad Nacional de Rosario  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Argentina</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>08</month>
<year>2019</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>08</month>
<year>2019</year>
</pub-date>
<volume>29</volume>
<numero>1</numero>
<fpage>84</fpage>
<lpage>96</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://scielo.senescyt.gob.ec/scielo.php?script=sci_arttext&amp;pid=S1390-85962019000100084&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://scielo.senescyt.gob.ec/scielo.php?script=sci_abstract&amp;pid=S1390-85962019000100084&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://scielo.senescyt.gob.ec/scielo.php?script=sci_pdf&amp;pid=S1390-85962019000100084&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen  El objetivo del presente trabajo fue analizar la relación entre la edad al primer parto con la producción láctea e indicadores reproductivos en vacas lecheras, con diferente potencial productivo. Se utilizaron datos retrospectivos de 260 vacas de raza Holstein biotipo Americano-Canadiense con información desde su nacimiento hasta finalizar la lactancia, recolectados entre los años 1992-2012, en el tambo cabaña perteneciente a la Escuela Agrotécnica Gral. San Martín dependiente de la Universidad Nacional de Rosario, ubicado en la localidad de Casilda, Departamento Caseros, provincia de Santa Fe, Argentina. Los animales se dividieron en dos categorías: vacas puras (n=103) y vacas con registro de cría (n=157). Cada una de las vacas pertenecientes a cada uno de los grupos mencionados se caracterizó en función de los valores de dos indicadores reproductivos: edad al primer parto en días e intervalo, parto concepción en días y dos indicadores productivos: producción de leche ajustada a 305 días de lactancia en litros y número de partos. No hubo diferencias significativas entre grupos en su precocidad. Las vacas puras presentaron mayor producción (t = 4; 493; P &lt; 0; 0001) mientras que las vacas con registro de cría fueron más fértiles (t = 2; 039; P = 0; 043). Los grupos no difirieron en el número de partos. Las diferencias en el comportamiento de las vacas puras y las vacas con registro de cría con diferente potencialidad productivo ponen en discusión el objetivo de ejercer presión para lograr un primer parto a los 24 meses como propuesta generalizada en los sistemas a pastoreo.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract  The objective of this study was to analyze the relationship between age at first calving with dairy production and re-productive indicators in dairy cows with different productive potential. Retrospective data of 260 Holstein American-Canadian biotype cows with information from birth to the end of lactation, collected from 1992 to 2012 in the dairy farm belonging to the agro-technical school Gral. San Martín, National University of Rosario, were used. The farm is located in the city of Casilda, province of Santa Fe, Argentina. Cows were divided into two categories: pure cows (n = 103) and cows with breeding records (n = 157). Each cow belonging to each of the aforementioned groups was cha-racterized according to the values of two reproductive indicators: age at first calving in days and calving-conception interval in days and two productive indicators: milk production adjusted to 305 days of lactation in liters, and num-ber of calving. There were no significant differences between groups in age at first calving. The pure cows presented higher production (t = 4;493; P &lt; 0;0001) while the cows with breeding record were more fertile (t = 2;039; P = 0;043). Groups did not differ in the number of calving. Differences in the behavior of pure cows and cows with breeding records with different productive potential puts into discussion the objective of exerting pressure to achieve a first delivery at 24 months as a generalized proposal in the grazing systems.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Producción de leche]]></kwd>
<kwd lng="es"><![CDATA[reproducción]]></kwd>
<kwd lng="es"><![CDATA[longevidad]]></kwd>
<kwd lng="es"><![CDATA[eficiencia]]></kwd>
<kwd lng="en"><![CDATA[Milk production]]></kwd>
<kwd lng="en"><![CDATA[reproduction]]></kwd>
<kwd lng="en"><![CDATA[longevity]]></kwd>
<kwd lng="en"><![CDATA[efficiency]]></kwd>
</kwd-group>
</article-meta>
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