No abstract

No abstract

<p class="CORPOICA"><span lang="ES-CO">Se obtuvieron predicciones acerca de los efectos genéticos aditivos y no aditivos relativos al peso al destete en terneros pertenecientes a un rebaño multirracial Angus x Brahman, valiéndose de un procedimiento de evaluación animal multirracial; estos valores se compararon frente a predicciones de los efectos genéticos basadas en evaluaciones que contemplaban únicamente los efectos aditivos. Se encontraron cambios substanciales en las predicciones de los efectos genéticos cuando se incluyeron los efectos genéticos no aditivos en la evaluación. Éstos originaron diferencias en el ordenamiento de los toros para los efectos genéticos aditivos y totales. Por lo tanto, en la selección de toros destinados a programas de cruzamiento, se recomienda usar evaluaciones genéticas multirraciales que involucren los efectos genéticos no aditivos.</span></p><p class="CORPOICA"> </p><p class="CORPOICA"><strong>Prediction of Additive and Nonadditive Genetic Effects for Weight at Weaning Using a Multibreed Animal Evaluation Procedure</strong></p><p class="CORPOICA"><span lang="EN-US">Additive and nonadditive genetic effects were predicted for weaning weight in an Angus-Brahman multibreed herd by using a multibreed animal evaluation procedure and were compared to the predictions of genetic effects based only on additive genetic effects. Changes in the prediction of genetic effects were found when nonadditive genetic efects were included in the genetic evaluation procedure. </span><span lang="ES-CO">These changes caused differences in the ranking of sires for additive and total genetic effects. </span><span lang="EN-US">Therefore, when bulls used in crossbreeding programs are to be chosen, it should be valuable to use multibreed genetic evaluations that involve nonadditive genetic effects.</span></p>

<p>Se obtuvieron predicciones de efectos genéticos aditivos y no aditivos para peso al destete en un rebaño Angus x Brahman usando un procedimiento de evaluación animal multirracial incluyendo un macromineral en la evaluación. Se encontraron cambios en las predicciones de efectos genéticos cuando se incluyó calcio, fósforo o magnesio sérico. La exactitud en las predicciones de los efectos genéticos aditivos y no aditivos fue mayor o igual a la reportada cuando se realizó el análisis de peso solamente. Las correlaciones entre las predicciones de valores genéticos aditivos basados en un análisis simple, y aquellos obtenidos cuando se incluyó un macromineral fueron altas (P &gt;.96). Para los efectos genéticos no aditivos, las correlaciones fluctuaron entre .65 y  .99. Por lo tanto, el uso de caracteres genéticamente relacionados con el crecimiento que pueden ser medidos al mismo tiempo que los pesos, pueden mejorar la exactitud de las predicciones genéticas del peso.</p><p> </p><p><strong>Changes in the Prediction of Genetic Effects for Weight at Weaning Including Serum Levels of Calcium, Phosphorus or Magnesium</strong></p><p>Additive and nonadditive genetic effects were predicted for weaning weight in an Angus x Brahman multibreed herd by using a multibreed animal evaluation procedure that included a macromineral trait. Changes in the prediction of genetic effects were found when serum Calcium, Phosphorus or Magnesium was included in the evaluation. Accuracy of predictions of additive and nonadditive genetic effects were higher than, or equal to, those reported when a single trait analysis was used. Correlations between predictions of additive genetic effects based on single trait analysis and those obtained when a macromineral is involved were high (P &gt;.96). For non additive genetic effects, correlations fluctuated from .65 to .99. Therefore, the use of traits genetically related to growth that can be measured at the same time as weights may improve the accuracy of prediction for weight traits.</p>

Forage responses to stocking rates and seasons were determined over a one-year period. The experimental design consisted of three stocking rates namely, light (2.0ha LSU -1 ), moderate (1.25ha LSU -1 ) and heavy (0.5ha LSU -1 ) and four seasons (autumn, winter, spring and summer) combined factorially in a Randomised Complete Block Design with three replicates per treatment. Data collected included aboveground available phytomass production, botanical composition and crude protein content.Total aboveground available phytomass production of forages at the end of the study period was significantly (P<0.05) lower in the heavy stocking rate than in the moderate and light stocking rates. Season significantly (P<0.05) reduced crude protein (CP) from 5.6% CP in summer and 7.8% CP in autumn to 4.2% CP in winter and 4.3% CP in spring. It is concluded that season exerted greater impact on sward productivity than stocking rate.