Project Number: 5434-31000-016-06
Project Type: Trust

Start Date: Feb 01, 2006
End Date: Dec 31, 2009

Objective:
To provide Angus breeders and their customers accurate EPD for carcass traits consistent with the recently approved Beef Improvement Federation guidelines by incorporating direct measures and indicator traits in a single analysis. New objectives: a. To estimate the genetic correlations between "molecular breeding values" (MBV), indicator traits, and carcass traits; and b. To evaluate trade-offs in accuracy of genetic predictions using varying amounts of information derived from phenotypic and genomic data.

Approach:
1. Compare EPD from ultrasound and carcass as produced in current structure. 2. Migrate current carcass trait analyses to animal model. This sets the base from which to move forward. May need to re-estimate genetic parameters (e.g. Ferreira et al (1999) JAS 77:2641-2650 indicate potential for differences between those estimated in sire/maternal grandsire models and those estimated with animal models. These differences are potentially large enough to compromise genetic evaluation and improvement). 3. Provide comprehensive description of data available from ultrasound evaluation and structured sire evaluation programs. 4. Consider the inference endpoint desired, e.g. 16 month old steer. This helps establish the structure of the mixed model equations. 5. Pedigree - how much? Connections between datasets? 6. Consider (theoretically) alternative models for each carcass unit. This is important because it sets the direction for work to follow. a. CW: joint analysis with 365-d weight? Sexes separate? Joint analysis with REA? Additional parameter estimates needed? b. REA: joint analysis of ultrasound and carcass. Sexes separate? Joint analyses with CW? Additional parameter estimates needed? c. MS: joint analysis of ultrasound IMF and carcass MS. Sexes separate? Additional parameter estimates needed? d. FAT: joint analysis of ultrasound and carcass. Sexes separate? Additional parameter estimates needed? Give the literature (reviewed by Bertrand et al (2001) JAS 79:E190-E200) suggesting quite modest genetic correlations between carcass traits, with the exception of CW and REA, it might be appropriate to consider three analyses: 1) carcass MS and ultrasound intramuscular fat, 2) carcass and ultrasound FAT, and 3) CW, 365-d weight, and ultrasound and carcass REA. Genetic parameters will be estimated as appropriate given the above strategy guidelines.