Stochastic simulation was carried out to access the consequences of combined use of assortative mating and sexed semen in a beef cattle population under selection. Six generations of selection were simulated under three different scenarios of mating strategy and sexed semen use. The first was characterized by random mating and no use of sexed semen. The second was simulated using positive assortative mating (PAM) for the 40% top dams and negative assortative mating (NAM) for the remainder, with no use […]

The objective of this work was to evaluate forage production and seasonal distribution of locally adapted ryegrass populations in comparison to commercial cultivars. Two experiments were carried out in two different locations of Rio Grande do Sul (Eldorado do Sul – EEA and Veranópolis – EEV), in 2004. Forage production of seven annual ryegrass populations, one Uruguayan cultivar (LE-284), one New Zealand cultivar (Eclipse) were compared to the commercial cultivar, in a total of ten treatments. The experimental design was […]

Data comprising 263,390 test-day (TD) records of 32,448 first parity cows calving in 467 herds between 1991 and 2001 from the Brazilian Holstein Association were used to estimate genetic and permanent environmental variance components in a random regression animal model using Legendre polynomials (LP) of order three to five by REML. Residual variance was assumed to be constant in all or in some classes of lactation periods for each LP. Estimates of genetic and permanent environmental variances did not show […]

Data consisting of 263.390 test day records (PDC) of 32.448 first lactation Holstein cows were used to compare three random regression test-day models (RR), a repeatability test-day model (RM) and a 305-d lactation model (P305) for breeding value (EBV) prediction of milk yield. One RR model used the logarithmic function of Ali & Schaeffer (AS) and the other two models used the exponential Wilmink function in its standard form (W) and a modified form (W*). The required covariance parameters were […]

Data from 44 bulls of the genetic groups Selection Nellore (NeS), Control Nellore (NeC) and Caracu (Ca) herds born in 1999 were used to evaluate the effects of selection for post weaning weight on carcass traits and meat cuts yields at 378 days of age (P 378). The animals were randomly distributed into two experimental classes: restricted feeding (AR) and ad libitum feeding (AL) including 8 animals from the NeS and Ca groups and 6 animals from the NeC group. […]

Data from 56 bulls of the genetic groups Selection Nellore (NeS), Control Nellore (NeC) and Caracu (Ca) herds born in 1999 were used to evaluate the effects of selection for weight at 378 days of age (P 378) on the chemical composition of empty body weight. The animals were randomly distributed to three experimental classes: initial slaughter (AI), restricted feeding (AR) and ad libitum feeding (AL). The AI class included 4 animals of each genetic group and the AR and […]

The aim of this study was to evaluate the performance and the variability between parental lines of broiler chicken reared in different environments, considering the genotype and environment interaction. Performance and morphometric traits of parental lines of commercial broiler chicken reared up to the age of 42 days in a complete-controlled environment of a breeding farm, in usual conditions of broiler chicken production system and in stress environment conditions were evaluated. Indexes of thermal comfort (temperature and humidity and enthalpy) […]

This study aimed to evaluate the inbreeding coefficient, alleles fixation and selection limit in a population selected during 20 generations. Selection was based on breeding values predicted by classical best linear unbiased prediction (BLUP), BLUP associated with molecular markers (BLUPM) and individual selection (IS) using different mating designs. The genetic similarity matrix used in BLUPM was obtained by simulating 100 micro satellite markers (simple sequence repeats) using a similarity coefficient corresponding to the mean Euclidean distance between quantitative data. The […]

This study aimed to estimate genetic and phenotypic parameters and trends for adjusted 305 days milk yield of Murrah buffaloes, which were born from 1982 to 2003. Variance components, genetic parameters and breeding values were obtained using the MTDFREML program. Genetic trends were estimated by regression of breeding values on birth year of the animals by two methodologies: 1) linear regression and 2) articulated polynomial regression using a spline smoothing function. Heritability and repeatability estimates were 0.20 and 0.36, respectively. […]

This study aimed to: a) to compare the covariance components obtained by Restricted Maximum Likelihood (REML) and by bayesian inference (BI); b) to run genetic evaluations for weights of Canchim cattle measured at weaning (W240) and at eighteen months of age (W550), adjusted or not to 240 and 550 days of age, respectively, using the mixed model methodology with covariance components obtained by REML or by BI; and c) to compare selection decisions from genetic evaluations using observed or adjusted […]