4. Statistics is important to understand if you want to become a Ph.D. animal breeder. Covariances and correlations are important for calculating genetic correlations, for example.
A) What is one important application of the regression coefficient in animal breeding?
B) Animal breeders can estimate breeding values, but their accuracy in part depends on the quality of performance testing by producers in the livestock industry. Why is contemporary grouping important for estimating breeding values? Can you have a contemporary group that is too small?
1 Q/A
Random regression models (RR) have become a popular methodology for the genetic study of longitudinal data since the last decade. The first objective of the current study was to investigate the application of RR models for the genetic analysis of egg production in turkeys. Data collected from a heavy dam line were used to estimate genetic parameters with 2 RR models, one having second-order Legendre polynomials as regression over time (RR2) and another with third-order polynomials (RR3). The second objective was to benchmark the performance of RR models with more conventional methods, so genetic parameters were reestimated using a multitrait (MT) and a repeatability model. To assess the model efficiency of predicting missing values, a reduced data set was used, and for each model, the predicted values of the deleted records were compared with the true values. The RR models were further compared against each other by eliminating the last period and estimating the MS error of the predictions for both models. The repeatability model had the poorest performance in predicting missing values. Heritability estimates from RR2 and MT models were close, whereas the RR3 model estimates were different. Both RR models demonstrated better prediction ability than the MT model. However, when RR models were compared solely, the RR2 model resulted in the smallest MS error.
2 Q/A
The routine reporting of accuracies for EBV’s was prompted by the development of across herd genetic evaluation procedures. In this scenario, it was important to give breeders the ability to discriminate between animals both in EBV and in how much information contributed to that EBV (herds differed vastly in their contributions of data to the analysis). This information could then be used to lessen the risk of importing inferior animals between herds which participate in an across herd analysis. An offshoot of this development will be the provision of accuracies for EBV’s in PIGBLUP V4.01. However, in general information on accuracies is of less benefit for within herd selection decisions. This is because breeding replacements are usually chosen from youngstock whose EBV’s will be estimated with similar accuracies. Further, considering accuracy in selection decisions may result in reductions to response through exclusion of younger animals from the selection process which have less information contributing to their EBV’s.
4. Statistics is important to understand if you want to become a Ph.D. animal breeder. Covariances and correlations are...
4. Statistics is important to understand if you want to become a Ph.D. animal breeder. Covariances and correlations are important for calculating genetic correlations, for example. A) What is one important application of the regression coefficient in animal breeding? B) Animal breeders can estimate breeding values, but their accuracy in part depends on the quality of performance testing by producers in the livestock industry. Why is contemporary grouping important for estimating breeding values? Can you have a contemporary group that...