Parâmetros genéticos de características reprodutivas de touros e vacas Gir leiteiro

Abstract

RESUMO -Com o objetivo de estimar parâmetros genéticos para a idade ao primeiro parto, perímetro escrotal e características do sêmen e avaliar a tendência genética da idade ao primeiro parto para animais da raça Gir Leiteira, foram analisadas medidas de 7.055 fêmeas e 97 machos de diversos rebanhos brasileiros. Os componentes de covariância foram estimados utilizando-se o método da máxima verossimilhança restrita, sob modelo animal, em análises unicaracterísticas.O modelo para características do sêmen incluiu os efeitos fixos central-ano-época de coleta de sêmen, idade à coleta como covariável, efeitos linear e quadrático. Para o perímetro escrotal, foram incluídos os efeitos fixos de ano do nascimento, classe de idade à medição do perímetro e central de inseminação. Para idade ao primeiro parto, foram incluídos os efeitos fixos de rebanho-ano-estação de nascimento e os efeitos aleatórios de animal e residual. As herdabilidades para perímetro escrotal e idade ao primeiro parto foram, respectivamente, 0,37 e 0,22. A tendência genética da idade ao primeiro parto foi significativa, com valor estimado de -0,018 mês/ano, e mostra que praticamente não houve progresso genético nessa característica ao longo dos anos estudados. As correlações genéticas obtidas em análises bicaracterísticas entre perímetro escrotal com volume, concentração, vigor, motilidade, defeitos maiores, menores e totais, número de doses, número total Genetic parameters for reproductive traits of dairy Gyr breed males and femalesABSTRACT -This work aimed to estimate genetic parameters for age at first calving, scrotal circumference, and seminal traits, and to evaluate genetic trend for age at first calving for dairy Gyr breed animals by analyzing data of 7,055 females and 97 males from several Brazilian herds. Covariance components were estimated by using the restricted maximum likelihood method under animal model in univariate analyses. The model for seminal traits included the company-year-season of semen collection fixed effects, age at the collection as a covariate, linear and quadratic effects.For scrotal circumference, it was included year of birth, age class at measurement, and insemination company fixed effects.For age at first calving, it was included herd-year-season of birth fixed effects and animal and residual random effects.The heritabilities for scrotal circumference and age at first calving were, respectively, 0.37 and 0.22. The genetic trend of age at first calving was significant, with estimated value of -0.018 month/year and it shows that genetic progress in this trait practically did not occur over the studied years. The genetic correlations from bivariate analyses among scrotal circumference with volume, concentration, vigor, motility, major, minor, and total defects, number of doses, total number of feasible spermatozoid and age at first calving were 0. 33, 0.22, 0.91, 0.86, -0.07, -0.03, -0.04, 0.30, 0.23 and -0.37, respectively. These results suggest improvements in reproductive efficiency of females when they are used in...

Genetic parameters of milk production and reproduction traits of Girolando cattle in Brazil

“…The heritability for AFC that was obtained in this study ($0.20) was within the range from 0.17 to 0.22 that was reported for Gyr cattle (Balieiro et al 2003;Santana J unior et al 2010). Nevertheless, it was lower than the estimates of 0.33, 0.48 and 0.70 that were reported for Holstein  Gyr, Brazilian dairy crossbred females (Bos taurusÂBos indicus), and Holstein  Boran cows, respectively (Vercesi Filho et al 2007;Fac o et al 2008;Haile et al 2009) and the estimates of 0.23-0.35 that were reported for Holstein cows in Brazil (Val et al 2004;McManus et al 2008a).…”

Estimates of genetic parameters and genetic trends for reproductive traits and weaning weight in Tabapuã cattle1,2

“…The mean observed for W210 (Table 1) was higher than those obtained by other authors (ranging from 167.71 to 175.91 kg) for the same breed, (Guimarães et al, 2003;Sakaguti et al, 2003;Ribeiro et al, 2007;Ventura et al, 2012;Campos, 2013) and lower than the mean obtained by Silva Filho et al 2013, which was 212.4 kg. The mean AFC obtained in the present study was similar to that found by Pereira et al (2005) for the same breed and similar to the values obtained for the Nelore, Gir, and Guzerá breeds (Grossi et al, 2009;Panetto et al, 2010;Santana Júnior et al, 2010;Boligon and Albuquerque, 2011;Barrozo et al, 2012).…”

Genetic study of litter size and litter uniformity in Landrace pigs

“…The genetic trend analysis is a useful tool for assessing genetic changes over the years (Santana Júnior et al, 2010), aiding to verify the need for adjustments in breeding programs (Euclides Filho et al, 1997). In this study, NBA and CVB showed linear and positive genetic trends, while the genetic trends for MBW and SDB were quadratic, increasing from the year 2009 until reaching the maximum point between 2012 and 2013, followed by a decreasing trend until 2016 (Figures 3 and 4).…”