Heritability Of Maternal Effects Research Articles

Direct and maternal genetic effects for preweaning growth in Retinta cattle estimated by a longitudinal approach throughout the calving trajectory of the cow

The direct and maternal genetic effects were estimated for the preweaning growth of Retinta calves with a multitrait model across parities, using a longitudinal approach with random regression models (RRM). The 120 (P120) and 180 days (P180) weights (5972 calves) were considered as different traits in each calving. The heritability of direct effect across parities was on average 0.37 for P120 and 0.58 for P180, slightly higher than the estimates by univariate (0.30 and 0.56) and bivariate models (0.30 and 0.51, respectively). The heritability for maternal effects was 0.16 for P120 and 0.26 for P180 and very similar by uni- (0.16 and 0.23) and multivariate model (0.16 and 0.22, respectively). The correlation between direct and maternal effects by RRM showed a pronounced antagonism -0.64 for P120 and -0.78 for P180), likewise uni- (-0.62 and -0.72) and multivariate case (-0.64 and -0.74, respectively). The preweaning weights should be considered as different traits across parities, because the genetic correlations were different from unity. The RRM also allowed us to estimate all the parameters throughout the calving trajectory of the cow. The use of multiple traits RRM across parities can provide very useful information for the breeding programmes.

Genetic parameters for direct and maternal calving ability over parities in Piedmontese cattle.

Estimates of heritabilities and genetic correlations for calving ease over parities were obtained for the Italian Piedmontese population using animal models. Field data were calving records of 50,721 first- and 44,148 second-parity females and 142,869 records of 38,213 cows of second or later parity. Calving ability was scored in five categories and analyzed using either a univariate or a bivariate linear model, treating performance over parities as different traits. The bivariate model was used to investigate the genetic relationship between first- and second- or between first- and third-parity calving ability. All models included direct and maternal genetic effects, which were assumed to be mutually correlated. (Co)variance components were estimated using restricted maximum likelihood procedures. In the univariate analyses, the heritability for direct effects was .19 +/- .01, .10 +/- .01, and .08 +/- .004 for first, second, and second and later parities, respectively. The heritability for maternal effects was .09 +/- .01, .11 +/- .01, and .05 +/- .01, respectively. All genetic correlations between direct and maternal effects were negative, ranging from -.55 to -.43. Approximated standard errors of genetic correlations between direct and maternal effects ranged from .041 to .062. For multiparous cows, the fraction of total variance due to the permanent environment was greater than the maternal heritability. With bivariate models, direct heritability for first parity was smaller than the corresponding univariate estimate, ranging from .18 to .14. Maternal heritabilities were slightly higher than the corresponding univariate estimates. Genetic correlation between first and second parity was .998 +/- .00 for direct effects and .913 +/- .01 for maternal effects. When the bivariate model analyzed first- and third-parity calving ability, genetic correlation was .907 +/- .02 for direct effects and .979 +/- .01 for maternal effects. Residual correlations were low in all bivariate analyses, ranging from .13 for analysis of first and second parity to .07 for analysis of first and third parity. In conclusion, estimates of genetic correlations for calving ease in different parities obtained in this study were very high, but variance components and heritabilities were clearly heterogeneous over parities.

Estimates of genetic parameters for litter size in six strains of Iberian pigs

Additive direct and maternal, permanent environmental and residual variances for total number of pigs born and number born alive in six closed strains of Iberian pigs were estimated by univariate restricted maximum likelihood using an animal model. Data were analyzed within strain, and also including all strains together. The largest data set analyzed included 8057 records and 3655 animals. Results were similar for both traits, irrespective of whether crossfostered dams were included in the analysis or not. Within-strain estimates of heritability of direct effects ranged from 0 to 13%, whereas heritability of maternal effects did not exceed 4%; permanent environmental effects accounted for between 0 to 18% of the phenotypic variance. Across strains, heritability of direct effects was 4% for total number born and 6% for number born alive, heritability of maternal effects was nil for both traits, and the variance of permanent environmental effects accounted for 7% of the phenotypic variance. The covariance between direct and maternal genetic effects, expressed as a percent of the total variation was negligible. The evidence suggests that maternal genetic effects and their covariance with direct genetic effects can be ignored in selection programs aimed to increase prolificacy in the Iberian pig.

Genetic parameters for liveweights of beef cattle in the tropics

This paper describes a genetic analysis of 20000 weighings from 1980-1988 on the progeny of more than 210 sires from three straightbred Brahman and one crossbred herd (Brahman or SahiwalxBritish breeds) in the Australian tropics. 200 day weight averaged 192 kg, very slightly less than 200 day weight in temperate Australia with similar phenotypic variance of 520 kg2. Mean 550, 700, and 900 day weights of 310, 350 and 450 kg and phenotypic variances of 800, 800 and 1485 kg2 were lower than in temperate regions at the same ages. Direct heritabilities for weight averaged 41% in the Brahmans and 31% in the crossbred herd. Genetic correlations amongst 200 day and later weights were 81-92%, except for an estimate of 63% between 200 and 900 day weights. Estimates of heritabilities for maternal effects were quite high in the crossbred herd for 200 and 365 day weights (19 and 14%), but only 4-5% for Brahmans. Models and statistical analyses are discussed and results compared with other published estimates from subtropical and temperate regions.

Estimates of genetic parameters for direct and maternal effects on embryonic survival in swine

Survival of 16,838 potential embryos was determined by counting corpora lutea and fetuses at 50 d of gestation for 1,081 litters by 225 sires. These data, coded as 1 or 0 depending on whether an ovulation was represented by a fetus, were used to estimate direct and maternal additive genetic variances and their covariance for embryonic survival. Data were from first-parity gilts of a Large White-Landrace composite population subdivided into two lines, one selected for an index of ovulation rate and embryonic survival for seven generations and a contemporary control line. Variance components were obtained by ANOVA and expectations of covariances among relatives and by derivative-free restricted maximum likelihood (DFREML) in an animal model. As a trait of the embryo, heritability of direct effects obtained with ANOVA was 3.8%, heritability of maternal effects was 1.5%, and the genetic correlation between them was -.51. After adjustment of embryonic survival for ovulation rate, lower estimates of each parameter were obtained with ANOVA. Heritability of embryonic survival as a trait of the dam was 9 to 10%. Estimates of heritability of both direct and maternal effects obtained with DFREML were less than 1% and the genetic correlation between them was -.64. When survival of embryos from only those dams with 15 or more ovulations was analyzed, heritability of maternal effects was 4.4%. Estimates of common environmental effects on embryonic survival ranged from 5 to 7%.

Genetic parameters of growth of Ethiopian Boran cattle

ABSTRACTRecords on birth weight and pre-weaning growth of 3959 Boran calves, which were progeny of 51 sires and 979 dams, were analysed by least-squares analysis of variance. The variance components for sires, dams and maternal grandsires were estimated from the data. On the basis of assumed genetic correlations −0·44 and −0·55 between direct and maternal effects on birth weight and weaning weight, respectively, the maternal genetic component and the genetic covariance between direct and maternal effects were estimated. The heritabilities for direct effects on birth weight and weaning weight were 0·11 and 0·22, respectively, while the heritabilities of maternal effects were estimated as 0·02 and 0·11, respectively for the same traits. Selection indices for direct and maternal genetic components of weaning weight were constructed for practical use. These selection indices combined information on the individual, the parents and sibs.

Genetic Variance Components of Birth Weight in a Herd of Unselected Cattle

Two replicates of a randomly selected herd of Hereford cattle have been developed at the Livestock and Range Research Station in Miles City, Montana. Dams were first bred to a random selection of bulls in 1976. For this study, birth weights of 1,012 calves born in 1977 through 1983 were adjusted for sex, age of dam and year effects. Analyses were on the entire data set and a series of subsets. Subsets were determined by parental birth weights, either above (H) or below (L) the overall mean for parents of that sex. Subsets were: H sires X random dams; L sires X random dams; random sires X H dams; random sires X L dams; H sires X H dams; H sires X L dams; L sires X H dams and L sires X L dams. Two additional subsets were termed assortative (H X H and L X L) and disassortative (H X L and L X H) matings. Genetic variance components including additive direct effects (sigma 2A), additive maternal effects (sigma 2M) and a covariance between transmitted and maternal effects (sigma AM) were estimated by solving simultaneous equations after estimating coefficients for offspring-sire, offspring-dam and offspring-midparent mean regressions and a paternal half-sib covariance. Estimates for heritability of direct effects, heritability of maternal effects and the genetic correlation between transmitted and maternal effects (h2 A, h2M and rAM) were .36, .82 and -.51, respectively, in the overall data set but varied considerably when estimated in the subsets.(ABSTRACT TRUNCATED AT 250 WORDS)

Inheritance of maternal immunoglobulin G1 concentration by the bovine neonate.

Serum samples were collected between 24 and 48 h of age from 408 Herefored calves of a Selection Experiment and from 200 Angus, Hereford and Red Poll calves of another experimental population (Germ Plasm Utilization Project). Concentrations of immunoglobulin G1 (IgG1) were determined by single radial immunodiffusion. Breed or selection line of calf and age of dam were the most important factors influencing IgG1 concentrations (P less than .01). In the Germ Plasm Utilization (GPU) herd, Angus calves were highest, Red Polls were intermediate and Herefords were lowest in serum concentrations. Calves from Hereford lines selected for weaning weight, yearling weight or an index based on yearling weight and muscling score were lower in IgG1 concentration than calves from the randomly selected control line. In both populations immunoglobulin levels in the calf increased as age of dam increased. In Selection Experiment Herefords, increased calving difficulty was associated with a decrease in calf IgG1 levels (P less than .05). Heritabilities of calf serum IgG1 concentration, estimated from paternal half-sib analysis on a within line or breed basis, were .03 +/- .09 and .13 +/- .19 in the two populations. In the Selection Experiment Herefords, when the component of variance for selection line was added both to the numerator and denominator of heritability, the revised estimate was .09 +/- .09. Heritabilities of maternal effects on IgG1 concentration were also estimated (by nesting calves within maternal grandsires) on a within line or breed basis. These heritabilities were .23 +/- .17 and -.07 +/- .27 for the Selection Experiment and GPU populations, respectively. In the Selection Experiment population, when the variance component for selection line was added to the numerator and denominator of maternal effects heritability, the estimate was .27 +/- . .17. Those calves that died had a lower mean IgG1 concentration than the population average (P less than .01).