(Co)variance components, genetic parameters and annual trends for calf weights in a pedigree Brahman herd under selection for three decades

Abstract

A 300 cow Brahman herd kept on improved pasture was subjected to a selection and management programme based on a limited breeding season. Artificial insemination using mainly progeny tested bulls was used in part of the herd and the rest were bred in single sire herds. Of the 200 sires used during the 30 year period, 82% were homebred and selected principally for high estimated breeding value of 18‐month weight. Variance components of birth (BW), weaning (205 W) and 18‐month (548 W) weights of 6130 calves born 1968 through to 1997 were estimated by the Restricted Maximum Likelihood method (REML) using uni‐ and bivariate animal models. For each weight the animal's direct and maternal genetic and the dam's permanent environmental effects were considered random and those of sex, year and month of birth and age of cow were considered fixed, but the models differed as far as the number of significant interactions included. Adjusted least squares means for BW, 205 W and 548 W were 28, 158 and 292 kg. Phenotypic and direct and maternal genetic trends from univariate analysis were for BW: 0.156, 0.061 and −0.001 kg; for 205 W: 0.471, 0.126 and 0.044 kg; for 548 W: 1.973, 0.486 and 0.251 kg per year. Direct and maternal heritabilities from univariate analyses were for BW, 205 W and 548 W, 0.33 and 0.08; 0.07 and 0.14; 0.13 and 0.08, respectively. Genetic direct‐maternal correlations for the three weights were −0.37, −0.13 and 0.49 and permanent environmental variance of the dam as proportion of phenotypic variance (c2) had values of 0.03, 0.16 and 0.01, respectively. Direct and maternal genetic correlations were for BW: 205 W, 0.64 and 0.74; for BW: 548 W, 0.35 and 0.74; and for 205 W: 548 W, 0.64 and 0.96. Future genetic work in the herd should put more emphasis on the improvement of cow efficiency for sustainable beef production on native and improved pasture.

Breed variation and genetic parameters for growth and body development in diverse beef cattle genotypes

“…In most previous studies, heritability and genetic correlations estimates for growth have been based on weight (Meyer, 1992;Koots et al, 1994a and b;Dodenhoff et al, 1998;Plasse et al, 2002). Few studies included additional body measurements like hip height and body length mostly at post-weaning (Gilbert et al, 1993;Vargas et al, 2000).…”

“…Evaluation of growth based on weight and weight gains abound in the scientific literature (Jenkins et al, 1991;Meyer et al, 1993;Plasse et al, 2002). However, there are limited available references to genetic factors affecting live developmental traits that define body composition which would assist beef producers to breed cattle that consistently achieve market targets and hence reward them with increased carcass values.…”

Parámetros y tendencias genéticas para características de crecimiento en el ganado criollo colombiano Romosinuano

“…Por el contrario, las heredabilidades directa y total presentan valores intermedios, mostrando un moderado efecto del factor genético sobre la variación de este carácter. La estimación de heredabilidad directa del PD fue superior a la reportada por Manrique et al (1999) El efecto de ambiente permanente (r 2 = 8,6%) sobre el PD fue bajo, pero similar al promedio reportado por Mercadante y Lobo (1997) (0,11) y Plasse et al (2002) (0,1), lo cual indica que el ambiente permanente es de relativa importancia a diferencia de lo que se ha encontrado en varios estudios con razas cebuinas (Plasse et al, 2002). Para la característica 'peso al destete' (PD) se obtuvieron valores de heredabilidad directa, materna y total, así: h = 0,435; en este caso, el efecto materno presentó un valor bajo, lo que demuestra que los genes maternos ejercen escazo efecto sobre el PD en terneros Romosinuano.…”

“…Por el contrario, las heredabilidades directa y total presentan valores intermedios, mostrando un moderado efecto del factor genético sobre la variación de este carácter. La estimación de heredabilidad directa del PD fue superior a la reportada por Manrique et al (1999) =0,10±0,04, inferiores a los registrados para el PD, debido a que en esta edad las variaciones del potencial de producción de leche de las vacas impactan menos el desarrollo de los teneros (Plasse et al, 2002). La mayoría de trabajos que registran caracteres posdestete se realizan solamente hasta el año de edad y por esto son difíciles las comparaciones, a causa de que en el trópico, el periodo de estrés posdestete se extiende hasta el año de edad.…”

“…La mayoría de trabajos que registran caracteres posdestete se realizan solamente hasta el año de edad y por esto son difíciles las comparaciones, a causa de que en el trópico, el periodo de estrés posdestete se extiende hasta el año de edad. Por eso, generalmente se considera que el pesaje a los 16 ó 18 meses es más apropiado para el estudio de diferencias genéticas y como criterio de selección (Plasse et al, 2002).…”