Genetic variability of milk components based on mid-infrared spectral data.

in Journal of Dairy Science (2010), 93(4), 1722-1728

The aim of this study was to estimate the genetic parameters of the mid-infrared (MIR) milk spectrum represented by 1,060 data points per sample. The dimensionality of traits was reduced by principal ... [more ▼]

The aim of this study was to estimate the genetic parameters of the mid-infrared (MIR) milk spectrum represented by 1,060 data points per sample. The dimensionality of traits was reduced by principal components analysis. Therefore, 46 principal components describing 99.03% of the phenotypic variability were used to create 46 new traits. Variance components were estimated using canonical transformation. Heritability ranged from 0 to 0.35. Twenty-five out of 46 studied traits showed a permanent environment variance greater than genetic variance. Eight traits showed heritability greater than 0.10. Variances of original spectral traits were obtained by back transformation. Heritabilities for each spectral data points ranged from 0.003 to 0.42. In particular, 3 MIR regions showing moderate to high heritability estimates were of potential genetic interest. Heritabilities for specific wave numbers, linked with common milk traits (e.g., lipids, lactose), were similar to those estimated for these traits. This research confirms the genetic variability of the MIR milk spectrum and, therefore, the genetic variation of milk components. The objective of this study was to better understand the genetics of milk composition and, maybe in the future, to select animals to improve milk quality. [less ▲]

On the value of incorporating dominance effects in genetic evaluation of dairy cattle.

in Proceedings of the 7th World Congress on Genetics Applied to LivestockProduction, Montpellier, France, August, 2002. Session 1 (2002)

Estimation of additive and nonadditive genetic variances in Hereford, Gelbvieh, and Charolais by Method R.

in Journal of Animal Science (2001), 79(12), 2997-3001

Parameters for direct and maternal dominance were estimated in models that included non-additive genetic effects. The analyses used weaning weight records adjusted for age of dam from populations of ... [more ▼]

Parameters for direct and maternal dominance were estimated in models that included non-additive genetic effects. The analyses used weaning weight records adjusted for age of dam from populations of Canadian Hereford (n = 467,814), American Gelbvieh (n = 501,552), and American Charolais (n = 314,552). Method R estimates of direct additive genetic, maternal additive genetic, permanent maternal environment, direct dominance, and maternal dominance variances as a proportion of the total variance were 23, 12, 13, 19, and 14% in Hereford; 27, 7, 10, 18, and 2% in Gelbvieh; and 34, 15, 15, 23, and 2% in Charolais. The correlations between direct and maternal additive genetic effects were -0.30, -0.23, and -0.47 in Hereford, Gelbvieh, and Charolais, respectively. The correlations between direct and maternal dominance were -0.38, -0.02, and -0.04 in Hereford, Gelbvieh, and Charolais, respectively. Estimates of inbreeding depression were -0.20, -0.18, and -0.13 kg per 1% of inbreeding for Hereford, Gelbvieh, and Charolais, respectively. Estimates of the maternal inbreeding depression were -0.01, -0.02, and -0.02 kg, respectively. The high ratio of direct dominance to additive genetic variances provided some evidence that direct dominance effects should be considered in beef cattle evaluation. However, maternal dominance effects seemed to be important only for Hereford cattle. [less ▲]

Covariance estimation with Method-R

in Abstracts from the 2000 ADSA/ASAS joint annual meeting (2000)

Studies on the value of incorporating the effect of dominance in genetic evaluations of dairy cattle, beef cattle and swine

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (1998), 4

Nonadditive genetic effects are currently ignored in national genetic evaluations of farm animals because of ignorance of the level of dominance variance for traits of interest and the difficult ... [more ▼]

Nonadditive genetic effects are currently ignored in national genetic evaluations of farm animals because of ignorance of the level of dominance variance for traits of interest and the difficult computational problems involved. Potential gains from including the effects of dominance in genetic evaluations include “purification” of additive values and availability of predictions of specific combining abilities for each pair of prospective parents. This study focused on making evaluation with dominance effects feasible computationally and on ascertaining benefits of such an evaluation for dairy cattle, beef cattle, and swine. Using iteration on data, computing costs for evaluation with dominance effects included costs could be less than twice expensive as with only an additive model. With Method Â, variance components could be estimated for problems involving up to 10 millions equations. Dominance effects accounted for up to 10% of phenotypic variance; estimates were larger for growth traits. As a percentage of additive variance, the estimate of dominance variance reached 78% for 21-d litter weight of swine and 47% for post weaning weight of beef cattle. When dominance effects are ignored, additive evaluations are “contaminated”; effects are greatest for evaluations of dams in a single large family. These changes in ranking were important for dairy cattle, especially for dams of full-sibs, but were less important for swine. Specific combining abilities cannot be included in sire evaluations and need to be computed separately for each set of parents. The predictions of specific combining abilities could be used in computerized mating programs via the Internet. Gains from including the dominance effect in genetic evaluations would be moderate but would outweigh expenditures to produce those evaluations. [less ▲]

Estimation of the dominance variance for postweaning gain in the US Limousin population

in Journal of Animal Science (1998), 76(10), 2515-2520

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North ... [more ▼]

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North American Limousin Foundation. Parental dominance subclasses were formed and related using the method of Hoeschele and VanRaden. Variance components were estimated using Method R based on six samples of 50%. Fixed effects in the model included contemporary group apd covariates for inbreeding and breed composition (percentage Limousin). Heterozygosity was negatively correlated with breed composition (< -.99) and was therefore not included in the model. Two types of contemporary groups used as original groups from the National Cattle Evaluation were partially based on breed composition. Original contemporary groups that were too homogeneous for breed composition were replaced by herd-year-sex classes. Two models were used with the two data sets. Model 1 contained the fixed effects described above and an additive genetic effect. Model 2 Included a dominance effect in addition to the effects contained in Model 1. In total, four combinations of contemporary group x model were used. Dominance variance was computed as being four times the estimated parental subclass variance. Estimates for inbreeding depression and breed composition (percentage Limousin) were all small and not greatly affected by inclusion of dominance effects or changes in contemporary groups. Estimates of the additive variance (expressed as percentage of the phenotypic variance) were only slightly affected, with values between 20 and 21%. Dominance estimates were highly affected when passing from original (10%) and to alternative contemporary groups (18%). Such large values may indicate that dominance is important for postweaning gain. Results showed the advantage of an individual dominance approach based on sire-dam combinations; therefore, expected gains through the use of specific combination ability as a part of the mating selection criteria for growth might be high. [less ▲]

Relationships among estimates of inbreeding depression, dominance and additive variance for linear traits in Holsteins

in Genetics, Selection, Evolution [=GSE] (1997), 29(4), 319-326

Estimates of dominance and additive variances were obtained for 14 linear traits. The data included 600 678 first parity records on 14 linear traits in Holsteins. The model included management groups, age ... [more ▼]

Estimates of dominance and additive variances were obtained for 14 linear traits. The data included 600 678 first parity records on 14 linear traits in Holsteins. The model included management groups, age at calving, additive and dominance effects, and regression on inbreeding percentage. The estimate of the dominance variance was 9.8% of the phenotypic variance for body depth: 8.0% for strength, 6.9% for stature, and was less than 5% for the remaining traits. The additive variance ranged from 12.2% for foot angle to 45.3% for stature. No clear relationship was found between the estimates of dominance and additive variance. larger negative estimates of the inbreeding depression were associated with higher estimates of the dominance variance. [less ▲]