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INFLUENCE OF BETA-AGONIST (ZILPATEROL) AND AGE

ON TENDERNESS OF BEEF LOIN AND SILVERSIDE

MUSCLES

E. Moholisa1, P E. Strydom1, M. Hope-Jones1, A. Hugo2

1Animal Production Institute, Agricultural Research Council, 2Department of Microbial, Biochemical and Food Biotechnology,

University of Free-State

TABLE OF CONTENTS

1. Introduction

2. Aim

3. Materials and methods

4. Results and discussion

5. Conclusions

6. Acknowledgements

Meat tenderness Most important palatability attribute of meat

Most challenging factor in the meat industry

Influenced by combination of Pre-slaughter

Post-slaughter

Interventions

(Thompson, 2002; Koohmaraie, Veiseth, Kent, Shackleford, & Wheeler, 2003; Tatum, Gruber & Schneider, 2007)

INTRODUCTION

*Therefore, it is difficult to describe/predict product quality

based on single factor like age or feeding regime

Pre-slaughter factors

Genetics, stress, gender, animal age, feeding practices

Post-slaughter factors

Rigor mortis development, electrical stimulation, aging, etc

(Thompson, 2002; Koohmaraie, Veiseth, Kent, Shackleford, & Wheeler, 2003;Tatum, Gruber & Schneider, 2007)

INTRODUCTION

INTRODUCTION

Beta-agonists-metabolic modifiers- cellular level

Bind to certain -receptors on fat and muscle cell surfaces

thereby modifying biochemical processes of tissue growth

lipolysis & lipogenesis

protein accretion subsequently promoting muscular

development

(Moody, Hancock & Anderson, 2000; Warris, 2000; Randuz, 2011)

(Strydom et al., 2009)

Affect beef tenderness negatively:

High calpastatin activity (enzyme inhibitor)

Reduction in calpain activity

*Subsequently leading to meat toughness

Used largely in SA feedlot – Zilpaterol

Studies on SA beef

Increased shear force of loin from 1.2-1.9 kg (tenderness )

depending on post mortem ageing

(Zilmax®)

As the animals age, meat becomes tougher- higher connective tissue

In SA feedlot cattle the problem is uncommon as the

animals are slaughtered younger

INTRODUCTION

ANIMAL AGE

SA Beef Carcass Classification - Age by dentition

(RSA Government Gazette Notice No. R.342 of 19 March 1999)

Younger animals

A-Age 0

Permanent incisors

Older animals

AB-Age 1-2

Permanent incisors

B-Age 3-6

Permanent incisors

C-Age >6

Permanent incisors

(RSA Government Gazette Notice No. R.342 of 19 March 1999)

It is clear that the recent introduction of beta-agonists in

the feedlot production system may have a huge impact on

quality independent of age or by interacting with age,

therefore contributing to variation in final quality

AIM

Investigate the effect of beta-agonist (zilpaterol) on

tenderness of 2 beef muscles

Longissimus dorsi (LD) -Loin

Biceps femoris (BF)-Silverside

AIM

Feedlot weaners - A age

Grass fed steers -AB & B age

MATERIALS AND METHODS

SOURCING OF ANIMALS

Pasture phase

40 Bonsmara steers

AB and B age group – (n = 20 ea)

SOURCING OF ANIMALS

Feedlot phase

40 Bonsmara weaners

A-age group

Grain fed ~110 days

(n=20) Beta agonists (AZ)

supplemented steers–30 days,

2 days withdrawal

Control group (n=20) (AC)

SLAUGHTER AND SAMPLING

All animals were slaughtered at an optimum market condition

(fat code 2-3)

Electrical stimulation applied (30s 400 V peak, 5 ms p @ 15 p/s)

Carcasses chilled at 0-5°C

pH and temperature taken every hour (4hrs) & after 24hrs

Each slaughter day was followed by a sample collection

Samples were vacuum aged for 3 & 14 days @ 4°C

Collagen properties

Collagen content and solubility were determined according

to the methods of Weber (1966), Bergman and Loxley

(1963), Boccard et al. (1979), and Hill (1966)

LABORATORY ANALYSIS

Myofibres extraction

Olympus BX40 system microscope

(Culler et al.,1978; Heinze & Bruggemann,1994)

Myofibrillar fragmentation lengths (MFL)

400X magnification

Warner-Braztler shear force measurements (WBSF)

(AMSA,1995)

@160°C Internal temp 70°C

Universal Instron Machine,

(Model 4301)

6 cores per cut

Cooled

16°C

Differences between treatments were determined by using a

one-way analysis of variance (ANOVA) procedure.

Age groups were used for collagen.

Age and post mortem aging were used for MFL and WBSF.

Tukey-Kramer multiple comparison test (α =0.05) was used to

determine differences between treatment means.

STATISTICAL ANALYSIS

(NCSS,2007)

RESULTS

AND

DISCUSSIONS

Collagen characteristics of M. Longissimus dorsi Age AC AZ AB B

Collagen content1 1.92b 1.33a 1.78b 1.74b

% Collagen solubility 10.48c 11.17c 8.89b 7.33b

Age AC AZ AB B

Collagen content1 2.81b 2.32a 3.04b 3.09b

% Collagen solubility 9.09c 9.93c 6.74b 6.22b

Collagen characteristics of M. Biceps femoris

P<0.001 a,bmeans with different superscripts differ significantly 1Hydroxy-proline N/ x 103

Collagen content and amount of heat stable collagen is related to the age of the animal, but it is also muscle dependent

COLLAGEN PROPERTIES

3 days post mortem ageing 14 days post mortem ageing

Shorter ageing period - longer MFL - tough meat

Longer ageing period - shorter MFL - tender meat - proper aging

Measures the amount of myofibrillar breakdown

(Olson, 1976)

MYOFIBRILLAR FRAGMENTATION LENGTHS (MFL)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

AC AZ AB B AC AZ AB B

m

Longissimus dorsi (LD) Biceps femoris (BF)

Dark: 3 days Light: 14 daysp<0.001

c bc

ab

d

bc

c

a

c

ab

Means with different superscripts differ significantly. Error bars represent standard deviation.

MFL measurements

a a

c

ab

c

bc

d

Lower shear force values - tender meat

Higher shear force values - tough meat

OBJECTIVE-WARNER- BRATZLER SHEAR FORCE (WBSF)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

AC AZ AB B AC AZ AB B

WBSF(k

g)

Longissimus dorsi (LD) Biceps femoris (BF)

Dark: 3 days Light: 14 days

ab

a

c

ab ab

cd

d

a

P<0.001

Means with different supercripts differ significantly. Error bars represent standard deviation.

WBSF Measurements

a a

bc bc

cd

ab

bc

bc

CONCLUSIONS

If age classification is intended to distinguish between classes of

tenderness based on number of incisors, then the South African

Beef Carcass Classification System will fail to distinguish between

certain cuts among A-age carcasses if zilpaterol is used or not.

Zilpaterol caused variation in tenderness - LD muscle -A age group

Zilpaterol did not have the same effect on high connective tissue cuts

Age played a dominant role in WBSF of high connective tissue cuts

ACKNOWLEDGEMENTS

Prof Arno Dr Strydom

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