Understanding and Managing Variation in Meat Tenderness T. L. Wheeler, D. A. King, and S. D. Shackelford U. S. Meat Animal Research Center, Agricultural Research Service, U. S. Department of Agriculture, Clay Center, Nebraska, USA

Presentation Outline Factors affecting tenderness variation Genetic influences on tenderness Predicting tenderness for sorting Tenderization strategies

Why is tenderness so important?

Consumer Rankings of Sensory Traits

Tenderness vs Price $/pound

Biological basis for variation in meat tenderness Contractile state Enzymatic degradation of proteins Connective tissue Marbling

Contractile State Extent of muscle shortening during rigor mortis formation

Rigor mortis

Effect of Muscle and Treatment on Sarcomere Length

Effect of Muscle and Treatment on W-B Shear Force

Effect of muscle on sarcomere length in beef

Enzymatic breakdown of protein (proteolysis) Responsible for tenderization during “aging” of meat Caused by an enzyme that naturally occurs in muscle Regulated by level of that enzyme, it’s specific inhibitor, and calcium

The Calcium-dependent (Calpain) Proteolytic System µ-calpain m-calpain calpastatin

Effect of muscle on desmin degradation in beef

The Toughening and Tenderization Processes of Meat The Toughening Phase The Tenderization Phase

Warner-Bratzler shear force, kg Sarcomere length, µm

Time Postmortem, h Shear Force, kg 12 Changes in Meat Tenderness after Harvest

Connective Tissue Measured as the amount of collagen

Effect of muscle on connective tissue in beef

Marbling/Intramuscular Fat

Slight 00 Moderately Abundant 00 Slightly Abundant 00 Moderate 00 Modest 00 Small 00 Average Prime Average Choice Select Low Choice High Choice Low Prime 3.1% 12.1% 10.2% 4.5%6.0% 7.8%

Marbling score Warner-Bratzler shear force n = 1,083 R 2 = 0.02 W-B Shear Force vs Marbling

The tenderness of a specific muscle primarily depends on: The combination of extent of muscle shortening, collagen content, and the extent of postmortem proteolysis.

Effect of Muscle on Tenderness Rating

Muscle specific strategies can be developed to improve tenderness problems.

Management Factors Age at harvest < 30 months Castration by 7 months Growth enhancement technologies anabolic implants β-adrenergic agonists Time on high energy diet Health Stress before harvest

Anabolic Implants Majority of cattle in the U.S. receive anabolic implants –Classified by active ingredients and strength Many cattle receive multiple implants More potent “aggressive” implant protocols –Greater growth –Deleterious effects on carcass and meat quality

Management Factors Age at harvest < 30 months Castration by 7 months Growth enhancement technologies anabolic implants β-adrenergic agonists Time on high energy diet Health Stress before harvest

Genetics and Meat Tenderness Beef breed studies Genetic markers

Beef Germplasm Evaluation (GPE) Project

SIRE BREEDS USED TO PRODUCE F I CROSSES IN THE GERMPLASM EVALUATION PROGRAM AT MARC a Cycle I Cycle II Cycle III Cycle IV Cycle V Cycle VI Cycle VII Cycle VIII HerefordHerefordHerefordHerefordHerefordHerefordHerefordHereford AngusAngusAngusAngusAngusAngusAngusAngus JerseyRed PollBrahmanLonghornTuliWagyuRed AngusBeefmaster S. DevonBraunviehSahiwalSalersBoranNorweg. RedLimousinBrangus LimousinGelbviehPinzgauerGallowayBelg. Blue Sw. Red&Wh.CharolaisBonsmara SimmentalMaine Anj.TarentaiseNelloreBrahmanFriesianSimmentalRomosinuano CharolaisChianinaShorthornPiedmonteseGelbvieh Piedmontese Charolais Gelbvieh Pinzgauer a With Angus and Hereford Dams. Composite MARC III cows were also included in Cycles V, VI, VI, and VIII.

GPE Breed Summary Pinzgauer Piedmontese Jersey South Devon Red Poll Brangus Charolais Gelbvieh Sahiwal Nellore Brahman Boran Beefmaster Slightly less TenderMore TenderLess Tender

Genetic Standard Deviations HA Nellore Pinzgauer Genetic Variation in Shear Force Within and Among Sire Breeds of Purebred Progeny

Percentage Piedmontese and Myostatin Genotype Ribeye Top sirloin Top round Bottom round

Percentage Retail Product Yield

2 alleles1 allele0 alleles

Effect of Muscle and Myostatin on Tenderness Rating

Effect of Muscle and Myostatin on Collagen Content

Myostatin Conclusions Myostatin Conclusions Use of terminal homozygous Piedmontese sire provides: A 7% increase in saleable product Improved tenderness in all four muscles

BREED SUMMARY Small improvements in tenderness can be made by selection of breed But within breed variation is large Inactive myostatin or “double muscling” has tenderness and muscling advantages

Genetic Markers for Meat Tenderness

Heritability of meat tenderness is estimated to be about 0.30

Traditional genetic selection is a slow process Greater progress in less time may be possible with marker assisted selection

Two µ-calpain and calpastatin markers that affect meat tenderness have been commercialized

We have validated the tenderness markers in commercial populations

Effect of µ-calpain (CAPN4751) genotype on beef tenderness 9% 23%

Effects of CAPN1_316 in cattle treated with differing implant protocols

So far we have found a small number of markers that have small effects It is a time consuming process, but technology is continually improving Marker Conclusions

Some of the variation in tenderness can be controlled by manipulating genetics GENETICS SUMMARY

Predicting and Enhancing Tenderness

It is not likely we will be able to ensure 100% tender meat Thus, we need a technology to sort the carcasses for tenderness

Meat from “Tender” carcasses can be marketed at a premium Meat from “Tough” carcasses can be targeted for tenderizing processes

The USMARC Beef Tenderness System Use of visible and near-infrared reflectance to predict beef tenderness

Validation of Beef Tenderness Prediction

Beef carcass grading

Tenderizing Technologies

Electrical Stimulation

Tenderstretch

Tendercut®

Postmortem aging 14 days or more

Marination

Blade/needle tenderization

Carcass electrical stimulation Postmortem aging Tenderstretch Tendercut® Marination Blade tenderization Tenderizing Technologies

Providing Consumers Lean, Tender Beef Optimize genetics Optimize management Identify tender from tough Tenderizing interventions