Beef Cattle Carcass Assessments

3.11 Carcass assessments

The ultimate goal of all beef cattle production systems is to efficiently produce a high yield of palatable beef. Meat quality and the quantity of edible portion are basic factors used to assess carcass merit. However, the relative emphasis to be placed on quality and quantity are subject to change with changing market demands.

Not all beef producers need complete carcass data. Careful thought should be given to the specific information that will be useful. Increasing the amount of traits to be recorded on large numbers of carcasses adds to the time required, costs, and likelihood of errors and may reduce beef processors’ interest in cooperating. Only trained personnel should be contracted to do this in the large processing plants. Carcass weight, composition and quality are essential traits to be recorded at the slaughterhouse.

An essential prerequisite for gaining records in the slaughterhouse is that the ID of the live animal stays with the carcass or that a system is used, that allows the reporting carcass data with the ID of the corresponding live animal.

The following traits, as illustrated in table 4, are recommended as mandatory traits for breeding purposes.
Table 4. Mandatory traits for breeding purposes.

Trait	Recorded as ….		Comments
Carcass weight	Weight	Kansas State	Requires Software for IMF
Estimated meat yield	Percent; score	Iowa State	Requires software (Iowa State)
Carcass classification/Scoring system	Score	Australia, US	Includes software for IMF

Carcass weight

Carcass weights are unaffected by variation in shrinking and therefore – apart from the scaling effect - show less variation than live weights. Compared to live weights they relate more to meat yield and to the consumers endpoint. Calculation of net gain is based on slaughter weight.

Typically, carcass weights are collected by commercial abattoirs; additionally experimental abattoirs come into consideration. Carcass weights should be collected consistently to ensure an informative data analysis.

Usually, carcass weight is defined by appropriate national legislation which clearly specifies which parts of the carcass are to be removed prior to taking the weight.

In the case of no legal definition, carcass weight should be defined as the hot weight of both half carcasses after removal of skin, bled and eviscerated and after removal of external genitalia, the limbs at the carpus and tarsus, head, tail, kidneys and kidney fats and the udder.

Preferably the unit of measurement should be metric to the nearest of 500 grams.

Carcass grade

Carcass grades significantly affect the market value of the carcass. Therefore they form a trait with big economic impact and should be used for the analysis of progeny productivity. Grading mostly is done according to national standards that frequently are based on appropriate legislation.

1. However, according to different market demands, national grading schemes frequently target different objectives and therefore are composed of different traits. On a global level there are two predominant types of grading schemes:
2. USDA grading scheme including the following components
   • Class (steer, bullock, bull, heifer, cow)
   • Maturity
   • Meat colour
   • Texture of lean meat
   • Quality grade: 8 levels (Prime; Choice; Select; Standard; Commercial; Utility; Cutter; Canner)
   • Marbling
   • Firmness
   • Yield grade
   • External fat
   • Kidney, pelvic and heart fat
   • Ribeye area
   • Carcass weight
3. EU grading scheme including the following components
   • Class (calf, young bull (=bullock), bull, steer, heifer, cow)
   • Conformation grade: 6 levels (S-E-U-R-O-P)
   • Fat grade: 5 levels (1-2-3-4-5)

As a consequence meat reports are almost incomparable across big market regions like e.g. North America, Europe and other continents. Therefore the grading system should be clearly indicated on reports provided for use outside the country where the grading scheme is applied. In order to provide useful information that might be used outside the market region, it is recommended additionally to record each of natural components forming the grade.

Dressing percentage

Dressing percentage describes the percent ratio between carcass weight and the live weight taken immediately before slaughter. Although dressing percentage mainly is used for the estimation of carcass weights of live animals, it provides additional information on the animal’s type even if carcass weight is measured directly.

A scale that measures in increments of 1 kg or 2 lb., or less, should be used for taking the live weight immediately before slaughter. As live weight is largely influenced by shrinking, dressing percentage should account for this effect, by standardisation of the live weight to 12-hours shrinking time. The correction factors should apply in the special production environment of the animals.

Dressing percentage should be described as percentage with 1 decimal place.

Meat yield

Meat yield means the percentage of lean meat in the beef carcass as obtained by dissection. However, - with regard to high costs arising from carcass dissection - meat yield frequently is estimated on the base of surrogate traits, that can be easily measured in the course of the slaughter process.

In some areas meat yield refers to the whole lean meat contained in the carcass, whereas other regions account for specified retail cuts forming the most evident part of the carcass value.

Meat yield should be described as percentage with 1 decimal place.

Some areas apply yield grades rather than meat yield itself; e.g. the USDA yield grade is a numerical score from 1 to 5 expressed as a whole number. It represents the yield of the boneless, closely trimmed retail cuts from the round, loin, rib and chuck. These cuts represent about 75% of the carcass weight and about 90% of the carcass value.

Y.G.=2.5 + (2.5 X adjusted fat thickness, in inches) + (0.2 X per cent kidney-, pelvic-, heart fat) + (0.0038 X hot carcass weight, in pounds) - (0.32 X Ribeye area)

The relation between yield grade and meat yield is described in table 3.5.
Table 3.5. USDA yield grade and meat yield.

Yield grade	Boneless, closely trimmed retail cuts
1	> 53.3
2	52.3 - 50.0
3	50.0 - 47.7
4	47.7 - 45.4
5	< 45.4

Meat quality

Definition of meat quality

In broader terms, quality refers to palatability, appearance, nutritional value and food safety. In practice, quality refers to the overall appearance and palatability of the edible portion of the carcass. Quality can be determined by evaluation of animal maturity, tenderness, subcutaneous fat, intramuscular fat (marbling), meat colour, fat colour, firmness of meat (lean) and texture of meat. Factors such as juiciness, flavour, aroma and undesirable flavours (off-flavours), are also quality traits, but can only be assessed through sensory taste panels and are therefore rarely recorded and evaluated.

Meat quality can be assessed on the basis of a subjective score (including e.g. a marbling score), through taste panels, or by using technical devices to measure the meat colour, tenderness, intramuscular fat, physiological parameters like the pH at different points of time, etc.

Meat quality can probably be defined as comprising four aspects of importance:

1. Visual quality: Factors evaluated in classifying carcasses and/or factors that affect consumers’ decisions when purchasing meat (e.g. subcutaneous fat cover, bone content and meat and fat colour).
2. Eating quality.
3. Tenderness, juiciness, odour and flavour intensity of the cooked product.
4. Nutritional quality.
5. Proportions of proteins, vitamins and minerals relative to energy density.
6. Safety. Negligible risk from food-borne illness or poisoning and absence of drug, chemical, antibiotic or hormone residues. (Dikeman, 1990). In this section, the focus will be on visual quality and eating quality (palatability).

Maturity

Maturity can be defined as an estimation of the physiological age of the carcass, which can be determined by evaluating the size, shape, and ossification of the bones and cartilage, the number of permanent incisors and the colour and texture of the lean. Alternatively, the chronological age of the animal may be used although physiological and chronological age are not necessarily the same. Where the chronological age of the animal is unknown, maturity score is a useful unit of measurement. Maturity is usually classified according to the percentage ossification of the cartilage of thoracic buttons. In case maturity scoring, the following scores apply (Table 3.6).
Table 3.6. Numerical scores and maturity/age groupings.

Maturity	Score	Chronological age	Percentage ossification of the cartilage of thoracic buttons
A	1.0 – 1.9	9 – 30 months	<10
B	2.0 – 2.9	30 – 42 months	10
C	-	-	35
D	-	-	70
E	-	-	90

In some maturity classifications, numerical scores are given within the chronological age groupings, for a more accurate approximation of maturity. A numerical score of 1.5 would suggest that the carcass was in the middle of “A” maturity, while a score of 1.9 would be appropriate for a carcass at the upper end of “A” maturity but not quite into “B” maturity.

Initial maturity score is determined by the skeletal characteristics with adjustments made according to characteristics of the lean tissue. However, lean characteristics cannot be used to adjust final maturity of the carcass more than one full maturity group.

Marbling

Marbling can be defined as the flecks of fat in the lean. Marbling is usually evaluated visually in the rib-eye muscle, which is exposed between the 12th and 13th ribs. Marbling contributes to meat tenderness and is also associated with the palatability traits of juiciness and flavour.

Marbling is usually assessed by classification (e.g. 9 degrees of marbling, ranging from Practically Devoid to Abundant) related to the estimated percentage of intramuscular fat. Marbling scores and intramuscular fat percentages are specific to carcass assessments performed in North America and are not necessarily applicable to other countries.

As a consequence, marbling should be recorded according to BIF standards, where each degree of marbling is divided into tenths within each degree of marbling as in the table 3.7.
Table 3.7. Descriptive and numerical marbling scores for quality grades of “A” maturity carcasses.

Quality grade1	Marbling	Score
Prime	Abundant	10.0 – 10.9
Prime	Moderately abundant	9.0 – 9.9
Prime	Slightly abundant	8.0 – 8.9
Choice	Moderate	7.0 – 7.9
Choice	Modest	6.0 – 6.9
Choice	Small	5.0 – 5.9
Select	Slight	4.0 – 4.9
Standard	Traces	3.0 – 3.9
Standard	Practically devoid	2.0 – 2.9

1:B-maturity carcasses with Small or lower degrees of marbling cannot be graded Choice or Select.

Quality grades may vary in the number of degrees of marbling within a grade. If marbling is the primary determinant of quality grade, the numerical scores for grade should be the same as the marbling scores, except in cases in which they are discounted for maturity, colour, firmness of lean, or texture of lean.

The average relationship between marbling scores and intramuscular fat percentages is shown in the table 3.8.
Table 3.8. Marbling and intramuscular fat.

Marbling score	Intramuscular fat, %
Slightly abundant	10.13
Moderate	7.25
Modest	6.72
Small	5.04
Slight	3.83
Traces	2.76

It is recommended that a highly trained and certified person be used to assess quality grade factors when collecting carcass data.

Colour firmness and texture of lean

Colour of the rib eye muscle is used as an additional indicator of maturity or physiological age. The visual appeal of beef at the retail counter is highly dependent on desirable colour. Dark cutters are carcasses that produce lean tissue that is dark red to almost black and often result from cattle that have been stressed prior to slaughter. Dark cutters are safe to eat and their palatability is not seriously affected. However, the colour reduces consumer acceptability and lowers carcass value dramatically

Firmness of lean refers to the relative firmness or softness of the rib-eye muscle, whereas texture of lean refers to the apparent fineness or coarseness of muscle fibres within the rib-eye muscle.

Colour, firmness, and texture of lean are widely used in North America, and are not necessarily applicable to other countries. Accordingly, those traits should be recorded according to the following BIF standards reported in table 3.9.
Table 3.9. Scores for lean tissue.

Score	Colour	Firmness	Texture
7	Light cherry red	Very firm	Very Fine
6	Cherry red	Firm	Fine
5	Slightly dark red	Moderately firm	Moderately fine
4	Moderately dark red	Slightly soft	Slightly fine
3	Dark red	Soft	Slightly coarse
2	Very dark red	Very soft	Coarse
1	Black	Extremely soft	Very coarse

Standardized Warner- Bratzler shear force procedures for sire evaluation

More direct measures of palatability than quality grade include Warner-Bratzler shear tests for tenderness assessment, and trained sensory panel evaluation for tenderness, flavour, and juiciness. However, cost and availability will restrict usage of these alternative methods.

An initiative to standardize the protocol for Warner-Bratzler shear force determinations was identified at the National Beef Tenderness Plan Conference in April, 1994. The purpose of this protocol is to facilitate consistent collection of Warner-Bratzler shear force determinations across institutions for comparative evaluation. These data can be used in progeny testing and in the development of carcass breeding values to improve meat tenderness. Any institution abiding by these guidelines can be certified to collect Warner-Bratzler shear force determinations for the beef industry.

Conversion of live animals to carcasses

The process of conversion of the live animal to the carcass can have a significant effect on meat tenderness; therefore, the slaughter process and the environmental conditions during slaughter should be controlled as closely as possible. Conditions that should be monitored and that could affect Warner-Bratzler shear force values include electrical stimulation and post mortem chilling. Although these factors can affect the ultimate tenderness of beef, these variables are probably not controllable by the researcher. Whenever feasible, chilling temperatures and the type of electrical stimulation used (if any) should be noted.

Sample preparation

Consistent sample collection and preparation are critical to obtaining repeatable and consistent Warner-Bratzler shear force determinations. The following procedures are to be utilized when preparing steaks for shear force determinations:

1. Steaks, 25 mm thick, should be removed from the longissimus lumborum between the 12th rib and the 5th lumbar vertebrae of the carcass. Only one steak per animal is needed for evaluation. Steaks should be trimmed free of fat and bone.
2. After removal from the carcass, steaks should be vacuum-packaged, aged 14 days then frozen at day 14 post mortem to -20 °C or lower until they can be evaluated at a later date. Steaks should be stored at 0 to 3 °C during the 14-day aging process. All steaks should be vacuum-packaged during refrigerated storage after removal from the carcass (assuming that they are cut from sub primals before the end of the 14-day period) and during frozen storage. Steaks should be frozen individually without stacking (rather than after boxing) to ensure uniform, rapid freezing.
3. Internal temperature of the sample at the initiation of cooking can affect tenderness; thus, this variable must be standardized. Frozen samples should be thawed at 2 to 5 °C until an internal temperature of 2 to 5 °C is reached. For steaks, 1.0 in. thick, the time frame is approximately 24 to 36 hours (thawing time depends largely on the ratio of frozen meat to refrigerator/cooler size). During thawing, avoid steak overlap and stacking to improve the consistency of the thawing process.
4. Internal temperature of steaks will be determined prior to cooking. Steaks should not be cooked until a temperature of 2 to 5 °C is obtained throughout each steak. Steaks should not be thawed at room temperature.
5. To enhance consistency among institutions, steaks must be broiled on a Farberware Open Hearth Electric broiler (Kidde, Inc., Bronx, NY) or oven-broiled. Samples should be cooked to an internal temperature of 40 °C, turned and cooked to a final internal temperature of 71 °C (removed from the heat at 71 °C). For consistency in cooking, do not cook more than four steaks at a time on each Farberware grill.
6. Temperature will be monitored with iron- or cooper-constantan thermocouple wires with diameters less than 0.02 cm., and special limits or error of less than 2 °C. A metal probe, such as a 15-gauge spinal needle with a stylet (plunger), should be used to insert the thermocouple into the geometric center of the steak. Push the probe (with the stylet inside) completely through the meat, remove the stylet and thread the thermocouple wire into the needle through the pointed end. Remove the needle and pull the end of the thermocouple back into the center of the meat. Temperature can be monitored using a potentiometer or hand-held temperature recorder.
7. Steaks should not be held in foil or other types of containers prior to chilling because these processes affect chilling and cooling rates.

Core preparation

1. Cooling temperature and time after cooking, before coring, should be standardized. Two methods of cooling are recommended. Either chill samples overnight at 2 to 5 °C before coring (wrap with plastic wrap to prevent dehydration) or cool samples to room temperature prior to coring. Cooling samples to room temperature should be conducted so that a uniform temperature is obtained throughout the sample before coring. At least a 4-hour cooling time is required for 25 mm -thick steaks. Both procedures will remove variation in shear force caused by core temperature at shearing. Laboratories should intermittently check to assure that the chilling or cooling method they are using is providing an even temperature throughout the steak prior to cooling. Adjustment by lengthening the cooling or chilling time should be implemented if the previous time intervals are not long enough.
2. Cores should be 1.27 cm. in diameter and removed parallel to the longitudinal orientation of the muscle fibres so that the shearing action is perpendicular to the longitudinal orientation of the muscle fibres. Cores can be obtained using a hand-held coring device or an automated coring device. Coring devices must be in good condition and sharp; otherwise the core diameters will vary, causing an increase in variation of shear values.
3. A minimum of six and maximum of eight cores will be obtained from each steak. Cores that are not uniform in diameter, that have obvious connective tissue defects, or that otherwise would not be representative of the sample, should be discarded. If samples are chilled before coring, cores should be kept refrigerated (2 to 5 °C) until they are sheared. All values obtained should be used for mean calculation, unless visual observation indicates that a value should be discarded (e.g., a piece of connective tissue).
4. Shear each core once in the centre to avoid the hardening that occurs toward the outside of the sample.
5. Shearing must be done by using a Warner-Bratzler shear machine or an automated testing machine with a WBS attachment and crosshead speed set at 20 cm./min.

Certification of Warner-Bratzler shear force

Certification of institutions that perform Warner- Bratzler shear force measurement is important in determining that the above procedures are being adhered to and to ensure that consistent, reliable data on meat tenderness are being collected. Certification requires that individuals performing Warner-Bratzler shear force tests at each institution maintain a shear force repeatability of 0.65 or higher on duplicate steaks from the same animal.

In the absence of a standard material, cooked meat from the same animal must serve as the standard. All shear force values will be adjusted to a MARC-shear-force equivalent. Institutions interested in certification should obtain four steaks from each of 15 animals, arrange to send one pair of steaks to MARC personnel for shear force determination, and analyse the second pair of steaks themselves. The coefficient of variation of shear force for the certification steaks must range between 20% and 35%, because the amount of variation affects repeatability. MARC personnel will calculate a repeatability value and an adjustment factor, if needed, to equate each institution’s mean shear force to a MARC basis.

Data to be recorded

For the purpose of genetic evaluations on meat quality traits from data collected at abattoirs, it is necessary to collect all relevant data that could influence the particular recorded meat quality data. These additional data may relate to pre-slaughter management and feeding (e.g. growth promoting implants), slaughter (e.g. electric stimulation), chilling (e.g. period), aging process (e.g. period) and cooking process (e.g. cooking method).

1. Feedlot recordings
   • Regular data as specified in the section relating to tests in “Finishing Herds”, and additionally:
   • Implantations (where administered)
     • Date
     • Type
     • Dose/amount
     • Single or re-implant
   • Beta-agonist (in case of application)
     • Start date
     • End date
   • Pre-slaughter conditions:
     • Distance transported
     • Weather conditions
     • Time from loading to off-loading
     • Time from arrival at abattoir to slaughter
2. Slaughter and warm carcass recordings
   • Regular data as specified in the section relating to “Commercial Slaughter Data”, and additionally:
   • Fat colour assessment
   • Meat colour assessment
   • Marbling assessment
   • Kidneys and channel fat weight
   • Eye muscle area
   • Electric stimulation:
     • (Yes/No)
     • Type of stimulator
     • Voltage
     • Duration/period
   • Ph 1.5h after slaughter
3. Cold carcass recordings
   • Fat thickness (e.g. back fat and P8)
   • Chilling
     • Temperature
     • Period
   • pH 24h after slaughter
4. Palatability recordings
   • Aging
   • Temperature
     • Duration/period
   • Frozen weight
   • Thawed weight
   • Thawed temperature
   • Time-on
   • Time-off
   • Cooking method
   • Final (meat core) temperature
   • Cooked weight
   • Shear force
     • Type of measurement
     • Sample core diameter
     • Shear force value
   Frozen weight, thawed weight, thawed temperature, time-on, time-off, final temperature and cooked weight will be collected on each steak, in addition to the Warner-Bratzler shear values. Warner-Bratzler shear force should be reported as the mean of all core values.
   • Sensory scores
     • Maximum
     • Minimum
   • Sensory attributes
     • Juiciness score
     • Flavour score
     • Tenderness score
     • Aroma score
     • Off-flavour score
   • Chemical measurement of marbling