Contemporary groups in the genetic evaluation of Nellore cattle using Bayesian inference

Abstract

-The objective of this work was to evaluate the criteria for the formation of contemporary groups (CGs) in the genetic evaluation of body weight at weaning in Nellore cattle. A total of 713,474 records from 3,066 herds located in Midwestern and Northern Brazil were used. Data were obtained from the genealogical registry of zebu breeds of the Brazilian association of zebu breeders. Data structures were defined based on the number of standard deviations (SDs) for outlier removal (±2.0, ±2.5, ±3.0, and ±3.5) and on the minimal number of animals per CG (3, 7, and 15). Genetic evaluation was performed with an animal model using Bayesian inference. Data structures with ±3.5 SDs and CG with at least 15 animals presented the highest additive genetic variance (82.65±2.93), and those with ±2.0 SDs and CG with at least 3 animals showed the lowest one (60.23±1.96). The proper formation of CGs results in better-quality data archives, allowing to obtain more trustable estimates for the genetic parameters. Better selection responses are obtained when the following criteria are adopted for the removal of outliers: 2.5, 3.0, and 3.5 standard deviations and a minimum of 15 animals per contemporary group.

Genetic and environmental factors that affect tick infestation in Nelore x Angus crossbreed cattle

“…There is no consensus on the size of the group of animals and the common conditions needed to form the cG (SIlVa et al, 2017). These criteria aim to maximize homogeneity within the cG, resulting in a smaller number of animals per group.…”

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

“…As fêmeas do rebanho foram divididas em dois grupos, de forma que, nos dois semestres do ano a estação de acasalamentos de um grupo coincidiu com a lactação no outro grupo, garantindo assim animais contemporâneos em relação a estágios fisiológicos, tanto no período seco quanto no período chuvoso do ano. Com essa estratégia houve um aumento na quantidade de animais por grupo contemporâneo, consequentemente, os parâmetros foram melhor estimados (SILVA et al, 2017). O manejo sanitário teve como base o resultado da avaliação do número de ovos por grama de fezes (OPG), que foi registrado em média oito vezes ao ano em todas as fêmeas do rebanho.…”

Genetic evaluation of age at first calving for Guzerá beef cattle using linear, threshold, and survival Bayesian models

“…Initially, the data were composed by 121,352 records, with mean of 1,277.27 ± 245 d, ranging from 740 and 1,860 d. Data from females with AFC out of the range of two SD within contemporary groups (CG) were considered as missing observations. The removal of outliers within CG varying from 2.5 to 3.5 SD has been used for growth traits in Nellore cattle (Silva et al, 2017). However, given the inconsistency of AFC trait in Zebu cattle under tropical conditions, we opted to be more restrictive by using 2 SD.…”