1. Selection For Carcass Marbling and Muscling-- Benefits and Pitfalls Jim Gosey University of Nebraska

2. Heritability of Reproduction Traits about 20% Conception rate Calving rate Calving ease

3. Heritability of Production Traits about 30 to 35% Birth, Wean, Year. Wts. Feed Intake Feed Conversion Mature Wt. ~ 50%

4. Heritability of Product Traits about 40% Fat REA Cutabilty Marbling Shear ?

5. Highly heritable traits are usually best changed by direct selection…….. Lowly heritable traits are usually best changed by crossbreeding ( heterosis and complementarity)

6. Carcass Traits can be changed Genetically………. Angus genetic trends for slaughter and ultrasound data indicate breeders have changed carcass traits !

13. Heritability and Genetic Correlation--Slaughter Data Trait Wt. Marb. REA Fat %RP Weight (Wt).30 -.02.52.13 -.14 Marbling (Marb.).36 -.09.09 -.11 Ribeye (REA).28 -.22.59 Fat Thick. (Fat).25 -.85 %Ret.Prod. (%RP).25 *71,273 Angus records, Fall 2003

14. Heritability and Genetic Correlation--Ultrasound Data Trait Wt. IMF REA Fat %RP Weight (Wt).57 -.07.40.18 -.19 %IMFat (IMF).31 -.04.22 -.16 Ribeye (REA).38.18.59 Fat Thick. (Fat).39 -.49 %Ret.Prod. (%RP).39 *294,515 Angus records, Fall 2003

15. 1. Heritabilities higher for Ultrasound 2. Selection for Marbling (%IMF) will …decrease Ribeye (-.09) (-.04) …increase Fat (.09) (.22) …decrease %Ret. Prod. (-.11) (-.16) 3. Selection for Ribeye will …increase % Ret Prod. (.59) (.59) …change Fat (-.22) or (.18)

16. Selection to change Net Carcass Merit will require selection for both Marbling(IMF) and Ribeye area Genetic Correlation between Marbling (IMF) and Ribeye is low enough to allow simultaneous change in both traits.

17. Summaries of research data have produced higher genetic correlations than breed carcass data

18. Antagonistic Genetic Correlations Calving ease & Birth wt. -.74 Marbling & Cutability -.25 Marbling & Year. wt. -.33 Marbling & REA -.21 Marbling & Backfat.35 Marbling & Shear Force -.31 ? Koots, 1994

19. Genetic Correlations Between Reproduction & Product Traits Female Fat Retail Trait Trim WT. Product Wt. Age Puberty -.29.30 Concept./Service.21.28 Calv. Difficulty -.31 -.02 Birth Wt. -.07.30 Mature Wt. -.09.25 MacNeil, 1984

20. Carcass EPD of Sort Group (+3sd) - Slaughter Data* Group** Marb. REA Fat %RP YW Milk Angus Av..14.09.003.03 65 17 Marbling(46).68.20.003.18 66 21 REA (32).12.61 -.017.67 76 20 *4,051 Current Angus sires, Fall 2003 **number of bulls in ( )

21. Carcass EPD of Sort Group (+3sd) - Ultrasound Data* Group** %IMF REA Fat %RP YW Milk Angus Av..05.07.00 -.01 65 17 %IMF (37).50.14.02 -.04 72 21 REA (32).08.74.00.58 88 20 *4,051 Current Angus sires, Fall 2003 **number of bulls in ( )

22. Outlier bulls for Marbling tended to be……….. Above average for Milk and Ribeye Mixed result for Fat & % Retail Product

23. Outlier bulls for Ribeye tended to be……. Average for Marbling (IMF) Above average for % Retail Product, Yearling Wt. and Milk

24. Number of Outlier Bulls for Marbling and Ribeye* Trait +1sd +2sd +3sd Marb & REA 164 22 4 Marb & REA (.50acc) 140 22 4 *4,051 Current Angus sires, Fall 2003

25. Multiple trait selection slows response in any one trait…... How many Angus bulls are above average for Marbling, Ribeye, Wean Wt., Year. Wt., SC, & below average for Birth Wt. ? 32 out of 3,172 + 1 Std. Dev. = 10 bulls + 2 Std. Dev. = 0 bulls

26. What about Marbling and Tenderness ? 102 Simmental bulls with progeny Tenderness data. Tender 10 bulls =.16 Marb. EPD Simm. Average =.09 Marb. EPD Tough 10 bulls =.03 Marb. EPD …Marbling is a crude predictor of tenderness, not a guarantee

27. DNA Testing to the Rescue ? DNA tests for the “Marbling” gene and the “Tenderness” gene only account for a small portion of the genetic variation (perhaps 10-15%).

28. Benefits of selection for Marbling / Muscling 1. Marbling alone = faster change 2. Muscling alone = faster change 3. Marbling and Muscling = check and balance, slows increases, reduces non-conforming cattle

29. Pitfalls of selection for Marbling / Muscling 1. Marbling = risk too much milk Tenderness more important 2. Muscling = risk too much mature size risk too much birth wt. risk lowered fertility

30. Summary 1. Marbling & Muscle respond 2. Outlier balance trait bulls scarce 3. Ultrasound database increases 4. DNA tests to screen seedstock 5. Threshold marbling important 6. Crossbreeding can help solve genetic antagonisms