<?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>0377-9424</journal-id>
<journal-title><![CDATA[Agronomía Costarricense]]></journal-title>
<abbrev-journal-title><![CDATA[Agron. Costarricense]]></abbrev-journal-title>
<issn>0377-9424</issn>
<publisher>
<publisher-name><![CDATA[Universidad de Costa Rica. Colegio de Ingenieros y Agrónomos. Ministerio de Agricultura y Ganadería]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0377-94242019000200009</article-id>
<article-id pub-id-type="doi">10.15517/rac.v43i2.37788</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Factores del animal y el manejo predestete que afectan la edad al primer parto en hatos de lechería especializada de Costa Rica]]></article-title>
<article-title xml:lang="en"><![CDATA[Animal effect and preweanig management on age at first calving in specialized dairy farms of Costa Rica.]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Castillo-Badilla]]></surname>
<given-names><![CDATA[Gloriana]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Vargas-Leitón]]></surname>
<given-names><![CDATA[Bernardo]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Hueckmann-Voss]]></surname>
<given-names><![CDATA[Frank]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Romero-Zúñiga]]></surname>
<given-names><![CDATA[Juan José]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Nacional de Costa Rica Escuela de Medicina Veterinaria ]]></institution>
<addr-line><![CDATA[ Heredia]]></addr-line>
<country>Costa Rica</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Universidad Nacional de Costa Rica  ]]></institution>
<addr-line><![CDATA[ Heredia]]></addr-line>
<country>Costa Rica</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,aff3  ]]></institution>
<addr-line><![CDATA[ Heredia]]></addr-line>
<country>Costa Rica</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Universidad Nacional de Costa Rica Posgrado Regional en Ciencias Veterinarias Tropicales ]]></institution>
<addr-line><![CDATA[ Heredia]]></addr-line>
<country>Costa Rica</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2019</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2019</year>
</pub-date>
<volume>43</volume>
<numero>2</numero>
<fpage>9</fpage>
<lpage>24</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S0377-94242019000200009&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S0377-94242019000200009&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S0377-94242019000200009&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN La edad al primer parto (EPP) correspon- de a uno de los parámetros más importantes para medir la eficiencia productiva de los bovinos, y a su vez, influye en el rendimiento reproduc- tivo y la composición de la leche. El objetivo de este trabajo fue determinar el efecto de los factores del animal y del ambiente, modificables y no modificables, desde el nacimiento hasta el destete sobre la edad al primer parto (EPP) en hatos lecheros especializados de Costa Rica. Se realizó un estudio cohorte retrospectivo para cuantificar el efecto de estas variables sobre la edad al primer parto (EPP), en el estudio se incluyeron, un total de 2980 vacas de razas Jer- sey y Holstein que presentaron su primer parto entre el 2013 y 2015, pertenecientes a 22 hatos lecheros especializados, ubicados en diferentes zonas ecológicas de Costa Rica, con datos en el programa VAMPP Bovino. Se analizaron los datos mediante estadística descriptiva y un modelo lineal generalizado. La EPP promedio, para los animales en estudio, es 27,4 meses (±4,7). Variables no modificables del individuo, como la raza, presentaron efectos significativos en la EPP, con valores de 30,1 (IC95%: 29,8-30,4) y 28,4 meses (IC95%: 28,1-28,8; p&lt;0,001) en la raza Holstein y Jersey, respectivamente. Por otra parte, se determinó un efecto significativo de la variable modificable de manejo (p&lt;0,0001), en aquellas fincas con protocolos de alta calidad de crianza de terneras, se obtuvo una EPP de 27,6 meses (IC95%: 27,2-28,0), significativamente menor a la encontrada en las fincas con desarrollo pobre de reemplazos (EPP: 30,2; IC95%: 29,8-30,6). Esta tendencia se mantuvo, tanto en el análisis de la variable de manejo de forma independiente como en asociación con raza y finca. La eficiencia de las técnicas de crianza se reflejaron en mejores valores de EPP.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT The age at first calving (AFC) correspond to one of the most important parameters to quantify the productive efficiency of bovines, because it influences the productive performance and milk composition. The aim of the study was to quantify the effect of the animal and environmental variables, modifiable and non- modifiable, from birth to weaning, on AFC in specialized dairy herds in Costa Rica. A cohort retrospective study was conducted, including a total of 2980 Jersey and Holstein cows with AFC in the period between 2013 and 2015, belonging to 22 specialized dairy herds located in different ecological zones of Costa Rica, with data in the Bovine VAMPP program. All data in the present research, was analyzed by descriptive analysis and a generalized linear model. The average AFC for the animals in the present study was 27.4 months (&#61617;4.7). Non- modifiable variables, like breed, had significant effect over AFC, with 30,1 (CI95%: 29.8-30.4) and 28.4 months (CI 95%: 28.1-28.8) for Holstein and Jersey respectively. Furthermore, the results showed a significant effect of management as a modifiable variable (p&lt;0.0001) revealing that farms with high quality calf rearing protocols had AFC of 27.63 months (CI95%: 27.24-28.03), contrary to poor quality systems (AFC: 30.20; CI95%: 29.83-30.57). This tendency was consistent whether the management variable was included as independent in the model or associated to breed and herd factors, where high efficiency in calf rearing reflects into better values of AFC]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Variables modificables]]></kwd>
<kwd lng="es"><![CDATA[variables no modificables]]></kwd>
<kwd lng="es"><![CDATA[sistemas de crianza]]></kwd>
<kwd lng="es"><![CDATA[desempeño reproductivo]]></kwd>
<kwd lng="es"><![CDATA[lechería especializada]]></kwd>
<kwd lng="en"><![CDATA[Modifiable variables]]></kwd>
<kwd lng="en"><![CDATA[non-modifiable variables]]></kwd>
<kwd lng="en"><![CDATA[rearing systems]]></kwd>
<kwd lng="en"><![CDATA[reproductive performance]]></kwd>
<kwd lng="en"><![CDATA[specialized dairy]]></kwd>
</kwd-group>
</article-meta>
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