Genetic analysis of productive and reproductive traits in multiple-breed dairy cattle populations

Abstract

-The objective of this work was to determine whether the random regression model using linear splines (RRMLS) is suitable to estimate the genetic parameters for productive and reproductive traits of a multiple-breed dairy cattle population, as well as to investigate the effect of the genetic group of the progeny on the genetic merit of the sire. The multiple-trait model (MTM) and the RRMLS with one knot fitted for every genetic group were used to obtain the genetic parameters. Records of 1/2 Holstein + 1/2 Gyr (1/2HG), 5/8 Holstein + 3/8 Gyr (5/8HG), and 3/4 Holstein + 1/4 Gyr (3/4HG) crossbreed dams were considered. The RRMLS showed better fitting. The additive and residual variances estimated by the MTM and the RRMLS were similar. Heritability varied from 0.20 to 0.33 for age at first calving, from 0.09 to 0.22 for first lactation length, and from 0.15 to 0.35 for first lactation 305-day milk yield, according to the genetic composition of the dams. The RRMLS is suitable to estimate the genetic parameters for productive and reproductive traits of multiple-breed dairy cattle populations. The genetic merit of the sires is affected by the genetic group of the progeny by which they are evaluated.Index terms: Gyr, heritability, heterosis, Holstein, selection. Análise genética de características produtivas e reprodutivas em populações multirraciais de bovinos leiteirosResumo -O objetivo deste trabalho foi verificar se o modelo de regressão aleatória com polinômios lineares do tipo spline (MRAPLS) é adequado para estimar os parâmetros genéticos de características produtivas e reprodutivas em uma população multirracial de bovinos leiteiros, bem como investigar o efeito do grupo genético da progênie sobre o mérito genético do touro. Foram utilizados o modelo multicaracterístico (Mult) e o MRAPLS com nós ajustados aos grupos genéticos, para obtenção dos parâmetros genéticos. Foram considerados os registros de vacas 1/2 Holandesa + 1/2 Gir (1/2HG), 5/8 Holandesa + 3/8 Gir (5/8HG) e 3/4 Holandesa + 1/4 Gir (3/4HG). O MRAPLS apresentou os melhores ajustes. As variâncias aditivas e residuais estimadas por Mult e MRAPLS foram semelhantes. As herdabilidades variaram de 0,20 a 0,33 para idade ao primeiro parto, de 0,09 a 0,22 para duração da primeira lactação e de 0,15 a 0,35 para produção de leite em até 305 dias na primeira lactação, de acordo com a composição genética das vacas. O MRAPLS é adequado para estimar parâmetros genéticos de características produtivas e reprodutivas em populações multirraciais de bovinos leiteiros. O mérito genético do touro é influenciado pelo grupo genético da progênie por meio do qual ele é avaliado.Termos para indexação: Gir, herdabilidade, heterose, Holandesa, seleção.

Single-step genome-wide association studies (GWAS) and post-GWAS analyses to identify genomic regions and candidate genes for milk yield in Brazilian Girolando cattle

“…In the current study, the heritability estimate for 305MY was 0.11 ± 0.005, and the repeatability estimate was 0.33 ± 0.003. In previous studies with Girolando cattle, heritability and repeatability estimates were higher than the estimates found in this study, with reported heritability values ranging from 0.15 to 0.35 (Ribeiro et al, 2017;Canaza-Cayo et al, 2018) and repeatability values ranging from 0.37 to 0.47 (Facó et al, 2008(Facó et al, , 2009.…”

Multiple trait and random regression models using linear splines for genetic evaluation of multiple breed populations

“…The correlation among the random regression coefficients used to adjust the sires BV did not differ from zero (Table 7), as found by Vallée et al (2013) and Ribeiro et al (2017). Those authors demonstrated that the sire BV is related to the breed composition of their progeny and the BV obtained by purebred progeny records differs from that of crossbred progeny.…”

“…Multiple-breed variance and heritability is specific to each breed group (Figure 2 VanRaden et al, 2011); therefore, RRMLS are suitable to estimate the genetic parameters of productive and reproductive traits in multiple-breed populations, once it provides distinct estimates of sire BV for each progeny breed group (Ribeiro et al, 2017). The heritability for AFC, LL, and MY-305 has shown moderate magnitude ( Figure 2); thus, the selection process could modify the phenotypic means of these traits over the generations.…”

“…Multiple-trait models (MULT) consider the same phenotype as different traits when measured in different breed groups and can incorporate heterogeneity of variances and covariances in multiple breed evaluations (Vallée et al, 2013;Lukaszewicz et al, 2015;Ribeiro et al, 2017). However, it is important to validate alternatives that can handle the genetic evaluation of multiple breed populations with several breed groups and with groups with few records.…”

“…In RRMLS, BV of selection candidates are obtained for specific points (knots) distributed along the gradient for a continuous variable of interest, so that the covariances and solutions of random regression coefficients directly represent the variances and BV for the traits of interest in each knot (Misztal, 2006). In this way, breed compositions can be expressed in multiple-breed genetic evaluations as a continuous variable, represented by the expected percentage of a particular breed for each animal with available data (Ribeiro et al, 2017). This means that solutions for the same trait are specific to the breed group, and the BV of sires are predicted regarding the specific breed group of the progeny.…”