Genetic trends for mature body weight, visual scores, and growth traits in Nellore cattle

Abstract

Mature weight (MW) of cows is related to the costs of their production. Usually, cows with moderate MW are more efficient in challenging environments, such as those available in the production systems in Brazil. In the present study, the selection index comprises the following traits: conformation, finishing precocity, musculature at weaning (WC, WP, WM) yearling (YC, YP and YM), scrotal circumference at yearling (SC), days to gain 160kg from birth to weaning (D160) and 240kg after weaning (D240). This are related to birth weight gain at weaning (WG) and from weaning to yearling (YG). The mature (MW) and birth weight (BW) traits were not considered in the selection index. The aim of this study was to estimate the values for the genetic trends (GT) of some important selection (MW) and economic traits (BW). A bi-character analysis of MW and other characteristics was performed to estimate the (co)variance components and genetic parameters. The GT results obtained for MW were null (0.0065% or 0.02718kg per year) in the period 1990-2007. The GT values were determined for BW (-0.0650% or -0.02017kg), WG (0.0758% or 0.0865kg), YG (0.1051% or 0.11377kg), and MW (0.0393% or 0.11276kg) per year. The visual score values (in score units) were also determined for GTat weaning [WC (0.2310%; 0.00707), WP (0.3624%; 0.3623%),aWM (0.01149; 0.01087)] yearling [YC (0.3256%; 0.00990), YP (0.4795%; 0.01496),YM (0.5041%; 0.01457)] per year. Index-based selection was effective to promote genetic progress in WG, WC, WP, WM, YG, YC, YP, and YM characteristics keeping BW and MW constant.

Genetic-Quantitative Uni- and Bi-Trait Analysis for Growth Traits in the Colombian Creole Breed Blanco Orejinegro (BON)

“…The genetic correlations for the direct genetic effect between the BW, WW, YW, and DWG traits with T120%, indicate that a large part of the genes with additive action that make individuals show positive genetic merit for those traits, influence these individuals to present favorable genetic merit with negative breeding values for T120, which is desirable in beef cattle. The contrary was found by Koetz Júnior et al, (2017) and Santana et al, (2017), where the genetic correlations were high and positive between the speed of growth traits (T180 or T160) with daily weight gains before and after weaning.…”

Índice De Seleção Para Reposição De Fêmeas Em Rebanhos De Caprinos De Corte / Selection Index for Replacement of Females in Herd of Cut Goats

“…Ressalta-se que, a capacidade da cabra gestar partos múltiplos demanda maior tamanho corporal (SANTOS et al, 2013) e isso também justificou incluir o Frame no índice de seleção do rebanho, mesmo sendo um critério que não se baseia em output (GRION et al, 2014). Porém, nos caprinos é diferente dos bovinos, onde maior peso da vaca está relacionado com maior custo de produção (KOETZ JÚNIOR et al, 2017).…”