Presentation on theme: "Selection For Carcass Marbling and Muscling-- Benefits and Pitfalls Jim Gosey University of Nebraska."— Presentation transcript:
Selection For Carcass Marbling and Muscling-- Benefits and Pitfalls Jim Gosey University of Nebraska
Heritability of Reproduction Traits about 20% Conception rate Calving rate Calving ease
Heritability of Production Traits about 30 to 35% Birth, Wean, Year. Wts. Feed Intake Feed Conversion Mature Wt. ~ 50%
Heritability of Product Traits about 40% Fat REA Cutabilty Marbling Shear ?
Highly heritable traits are usually best changed by direct selection…….. Lowly heritable traits are usually best changed by crossbreeding ( heterosis and complementarity)
Carcass Traits can be changed Genetically………. Angus genetic trends for slaughter and ultrasound data indicate breeders have changed carcass traits !
Heritability and Genetic Correlation--Slaughter Data Trait Wt. Marb. REA Fat %RP Weight (Wt) Marbling (Marb.) Ribeye (REA) Fat Thick. (Fat) %Ret.Prod. (%RP).25 *71,273 Angus records, Fall 2003
Heritability and Genetic Correlation--Ultrasound Data Trait Wt. IMF REA Fat %RP Weight (Wt) %IMFat (IMF) Ribeye (REA) Fat Thick. (Fat) %Ret.Prod. (%RP).39 *294,515 Angus records, Fall 2003
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)
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.
Summaries of research data have produced higher genetic correlations than breed carcass data
Genetic Correlations Between Reproduction & Product Traits Female Fat Retail Trait Trim WT. Product Wt. Age Puberty Concept./Service Calv. Difficulty Birth Wt Mature Wt MacNeil, 1984
Carcass EPD of Sort Group (+3sd) - Slaughter Data* Group** Marb. REA Fat %RP YW Milk Angus Av Marbling(46) REA (32) *4,051 Current Angus sires, Fall 2003 **number of bulls in ( )
Carcass EPD of Sort Group (+3sd) - Ultrasound Data* Group** %IMF REA Fat %RP YW Milk Angus Av %IMF (37) REA (32) *4,051 Current Angus sires, Fall 2003 **number of bulls in ( )
Outlier bulls for Marbling tended to be……….. Above average for Milk and Ribeye Mixed result for Fat & % Retail Product
Outlier bulls for Ribeye tended to be……. Average for Marbling (IMF) Above average for % Retail Product, Yearling Wt. and Milk
Number of Outlier Bulls for Marbling and Ribeye* Trait +1sd +2sd +3sd Marb & REA Marb & REA (.50acc) *4,051 Current Angus sires, Fall 2003
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, Std. Dev. = 10 bulls + 2 Std. Dev. = 0 bulls
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
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%).
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
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
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