Meat Science: Diet, Evaluation, Growth, Grading, and Appraisal

A comprehensive set of practice flashcards covering the nutritional role of meat in human diets, objective evaluations of live animals and carcasses, growth and development biology, USDA grading standards, and carcass value appraisal factors.

According to the Dietary Guidelines for Americans 2025-2030, what are the recommended daily protein serving goals based on body weight?

The serving goal is $1.2\text{ to }1.6\text{ grams}$ of protein per kilogram of body weight per day.

Approximately how much protein is contained in one ounce of cooked lean meat?

Approximately $7\text{ g}$ of protein per $1\text{ ounce}$ of cooked lean.

Based on U.S. meat consumption data, how many ounces of meat do Americans consume per day on a cooked edible portion basis and in total?

Americans consume $2.1\text{ ounces per day}$ on a cooked edible portion basis (assuming $1/2$ of fat is consumed) and $2.5\text{ ounces per day}$ in total (including $0.4\text{ ounces}$ of processed meat).

What key consumer preference regarding fat was revealed by the National Consumer Retail Beef Study?

Consumers wanted leaner beef with less excess or trimmable fat; specifically, they wanted "taste fat" (intramuscular fat/marbling) but not "waste fat" (excess external or intermuscular fat).

What two major industry impacts resulted from the National Consumer Retail Beef Study?

Retailers transitioned to closer-trimmed retail cuts (known as the "1/4-inch Revolution"), and the USDA changed the grade name "Good" to "Select."

According to the National Beef Market Basket Survey, how did the fat content of beef retail cuts compare to USDA Agriculture Handbook 8-13?

Beef steaks and roasts had $27.4\%$ less fat, and ground beef had $10.2\%$ less fat.

What concept is depicted in this figure, and what minimum fat percentage is necessary to avoid undesirable palatability?

The diagram illustrates the "Window of Acceptability" for fat in meat (Savell and Cross, 1988); a minimum of $3\%$ fat in raw meat must be present as marbling fat in retail cuts, with further palatability thresholds occurring at $5\%$ and $7\%$.

What primary physiological roles do zinc, choline, and iron provide as nutrients found in beef?

Zinc helps maintain a healthy immune system, choline supports nervous system development, and iron helps the body use oxygen.

How does heme iron differ from nonheme iron in dietary absorption, and what dietary factor enhances nonheme iron uptake?

Heme iron (found in meat, poultry, and fish) is more readily absorbed by the body than nonheme iron (found in plants); consuming meat, poultry, or fish alongside plant foods helps the body absorb more nonheme iron.

Which dietary items are identified as iron absorption blockers?

Coffee, tea, legumes, and spinach.

What did Bonanome and Grundy (1988) determine regarding the impact of dietary stearic acid ($\text{C18:0}$) on plasma cholesterol?

Stearic acid was found to be as effective as oleic acid in lowering plasma cholesterol levels when either replaces palmitic acid ($\text{C16:0}$) in the diet.

What did Scott et al. (1991) find when comparing lipoprotein profiles of subjects on a lean beef diet versus a chicken and fish diet?

Reductions in low-density lipoprotein ($\text{LDL}$) and total cholesterol were similar between diets containing lean beef ($4\%$ fat) and chicken/fish ($1.7\%$ fat), but the chicken and fish diet produced a greater decrease in high-density lipoprotein ($\text{HDL}$).

What is the approximate accuracy rate of expert evaluators in estimating quality and yield grades in live animals?

Approximately $60\%$ accurate.

Which two yield grade traits are measured in live cattle using ultrasonics?

Subcutaneous fat thickness at the 12th rib and ribeye area at the 12th–13th rib.

Name two optical probes used to assess yield grade components on hot or unribbed carcasses.

The Hennessy Grading Probe and the Fat-O-Meater.

How does Nembutal sleep time distinguish between fat and lean live hogs?

Because anesthetics are preferentially absorbed by adipose tissue, a fat hog sleeps for only $70\text{ minutes}$ compared to $180\text{ minutes}$ for a lean hog following a $12\text{ mg}$ injection.

How does a whole-body $K^{40}$ radiation counter estimate total muscle mass in a live animal?

All potassium ($\text{K}$) in the animal is located in muscle, the ratio of $\text{K}$ to $K^{40}$ is constant, and the detected gamma radiation emitted by $K^{40}$ is directly proportional to total muscle.

What physiological principle allows Total Body Electrical Conductivity (ToBEC) to estimate carcass composition?

Muscle and bone are highly conductive to electrical current, whereas fat is lowly conductive; therefore, less current flows through a fat animal or carcass.

What is Video Image Analysis (VIA) and where has a modified retail unit been implemented?

VIA utilizes a camera, computer, and digitizer to capture and freeze-frame images to evaluate cutability and quality; a modified retail assessment unit is used by Qantas Airlines.

What is the formula for whole body specific gravity, and how does the numerical value correlate with fatness?

$\text{Specific gravity} = \frac{\text{Weight in air}}{\text{Weight in air} - \text{Weight in water}} \times 100$; a higher number indicates a lean animal, while a lower number indicates a fat body.

What three management practices must be followed to produce a desirable carcass?

1. Full feed; 2. Market when ready; 3. Do not hold.

In this growth impetus diagram showing tissue and body area development, what do curves A, B, C, and D represent?

They represent the priority of nutrient utilization: A = Nervous tissue (Head; Perinephric fat); B = Skeletal tissue (Neck and shoulder; Intermuscular fat); C = Muscle tissue (Hind limb; Subcutaneous fat); D = Fat tissue (Rib and loin; Intramuscular fat).

At what live weights do cattle, swine, and sheep attain optimal carcass tissue proportions under typical production conditions?

Cattle at $1{,}300\text{ pounds}$, swine at $280\text{ pounds}$, and sheep at $120\text{ pounds}$.

According to this diagram of optimum carcass composition, at what slaughter weights do small, medium, and large frame steers achieve $65\%$ muscle and $23\%$ fat?

Small frame steers achieve it at $900\text{ pounds}$, medium frame steers at $1{,}100\text{ pounds}$, and large frame steers at $1{,}300\text{ pounds}$.

What three negative biological and economic effects occur when an animal is held past its optimal composition endpoint?

Decreased rate of gain, decreased feed efficiency, and undesirable carcass composition due to excess deposition of perinephric, seam, and external fat.

What five animal factors determine carcass value?

Age, weight, sex, fatness, and muscling.

Why were standardized slaughter animal and carcass grading systems developed in the early 1920s?

To facilitate market news reporting and to enable commercial transactions sight unseen.

What are the USDA quality (estimated palatability) grades for beef, pork, and lamb?

Beef: Prime, Choice, Select, Standard, Commercial, Utility, Cutter, Canner; Pork: U.S. and U.S. Utility; Lamb: Prime, Choice, Good, Utility, Cull.

What are the USDA yield (estimated cutability) grades for beef, pork, and lamb?

Beef: 1, 2, 3, 4, 5; Pork: 1, 2, 3, 4; Lamb: 1, 2, 3, 4, 5.

Under original beef grading concepts, which quality grades were established for elite consumers, retail consumers, and manufacturing beef?

Prime was identified for elite consumers; Choice, Select, and Standard were for retail consumers; and Commercial, Utility, Cutter, and Canner were for manufacturing/further-processed beef.

Which specific carcass traits are measured to predict cutability in beef carcasses?

Carcass weight (size), ribeye area (muscling), adjusted fat thickness at the 12th rib (trimmable fat), and kidney, pelvic & heart ($\text{KPH}$) fat percentage (internal fat).

How do carcass fatness and muscling oppositely influence retail cut yield?

As fatness increases, retail cut yield decreases; as muscling increases, retail cut yield increases.

Based on this Old:Young values chart, what are the relative price indices for beef, swine, and sheep, and which species is most discounted with advancing age?

Swine has an index of $91$, beef is $67$, and sheep is $52$; sheep value is the most severely discounted with advancing age, whereas swine is the least discounted.

What specific meat quality defects develop in beef and sheep as animals increase in age?

Beef becomes less tender, develops more intense flavor, darker lean color, and yellow fat color; sheep develop an undesirable flavor and experience a higher condemnation rate due to disease.

What are the ages at marketing versus puberty for beef cattle, swine, and sheep?

Beef: marketed at $18\text{ months}$, puberty at $12\text{ months}$; Swine: marketed at $7\text{ months}$, puberty at $7\text{ months}$; Sheep: marketed at $8\text{ months}$ (Spring lamb) or $14\text{ months}$ (old crop lamb), puberty at $8\text{ months}$.

How does sex affect carcass dressing percentage in beef cattle?

Dressing percentage decreases by $4\text{ to }10\%$ in heifers (due to pregnancy) and in some bulls (due to heavier hides, heavier heads, and less fat).

What sex-related shifts occur in carcass wholesale cut proportions for bulls, heifers, and old crop rams?

Bulls exhibit chuck $+2\%$ due to crest development; heifers exhibit flank $+2\%$ due to udder fat deposition; old crop rams exhibit shoulder $+3\%$ due to secondary sexual characteristics.

What is the ranking of sex classes in order of cutability for beef, swine, and sheep?

Beef: Bullock > steer > heifer; Swine: Boar > gilt > barrow; Sheep: Ram > wether > ewe.

What chronological sequence governs fat deposition in meat animals?

1. Mesenteric; 2. Kidney; 3. Intermuscular; 4. Subcutaneous; 5. Intramuscular.

How much of the variation in intramuscular fat (marbling) is explained by subcutaneous fat thickness?

Subcutaneous fat thickness correlates at $r = 0.24$, explaining only about $5.8\%$ of the variation in marbling.

Which livestock breeds demonstrate superior ability to deposit marbling, and which demonstrate inferior ability?

Superior: Angus (cattle), Duroc (swine), Southdown (sheep); Inferior: Limousin (cattle), Yorkshire (swine), Merino (sheep).

Which cattle breeds are characterized by predominantly red (Type I) muscle fibers versus white (Type IIB) muscle fibers?

Predominately red (Type I): Angus, Jersey, Longhorn, Shorthorn; Predominately white (Type IIB): Charolais, Limousin, Maine Anjou, Gelbvieh.

According to Butterfield and Berg, what percentage of total muscle weight in cattle is represented by the "Expensive Muscle Group"?

Approximately $56\%$ of total muscle weight.

What are the Muscle:Bone ratios for thinly muscled, normally muscled, thickly muscled, and double muscled cattle?

Thinly muscled: $2.5:1$; Normally muscled: $3.5:1$; Thickly muscled: $4.5:1$; Double muscled: $5.5\text{ to }8.5:1$.

What are the technical definitions of leanness, muscling, and meatiness?

Leanness is the ratio of total muscle to total fat; Muscling is the ratio of total muscle to total bone; Meatiness is the ratio of total muscle plus "acceptable" fat to total bone plus "trimmable" fat.

According to the Dietary Guidelines for Americans 2025-2030, what is the maximum recommended daily sodium intake for individuals aged 14 and older?

Less than $2{,}300\,\text{mg}$ per day.

Under the Dietary Guidelines for Americans, what is the maximum recommended percentage of total daily calories that should come from saturated fats?

Saturated fat consumption should not exceed $10\%$ of total daily calories.

According to the Dietary Guidelines for Americans 2025-2030, what is the established single-meal limit for added sugars?

A single meal should contain no more than $10\,\text{g}$ of added sugars.

What primary physiological function does selenium serve as an essential nutrient found in beef?

Selenium helps protect cells from damage.

In the National Beef Market Basket Survey, what average fat thicknesses were measured across retail cases and major primal cuts?

Retail cuts had an overall fat thickness of $0.11\,\text{inch}$, while cuts from the major primal cuts averaged $0.14\,\text{inch}$.

How does antipyrine dilution objectively estimate total body composition in live animals?

Antipyrine distributes uniformly throughout body water; because total body water is inversely related to total body fat, water volume predicts fatness.

What chemical tracer is utilized in live animal composition appraisal to predict chemical body composition by measuring body water?

Deuterium oxide ($\text{D}_2\text{O}$).

Which two cross-sectional medical imaging technologies can be utilized to evaluate whole-body composition in live animals?

Computerized Tomography (CT-scan) and Magnetic Resonance Imaging (MRI).

How does the plane of nutrition affect the rate at which an animal attains optimum carcass composition?

A higher plane of nutrition allows an animal to achieve optimum carcass composition more rapidly than a low plane.

On a percentage basis, how do muscle, bone, and fat proportions shift as a market meat animal matures over time?

Bone and muscle percentages decrease over time, while fat percentage steadily increases.

How do dichotomous and hierarchical carcass grading schemes differ in structure?

A dichotomous scheme categorizes carcasses into two distinct groups (such as acceptable versus unacceptable), whereas a hierarchical scheme ranks carcasses across multiple quality tiers (such as superior, good, average, and inferior).

Which carcass traits are measured to predict cutability in pork and lamb carcasses under USDA grading frameworks?

Pork cutability is predicted using muscling score and last rib backfat thickness; lamb cutability is predicted using adjusted fat thickness at the 12th rib.

What directional growth pattern describes the developmental gradients of muscling in livestock?

Muscling starts at the extremities (forelimbs and hindlimbs), moves upward toward the chuck and round, progresses forward from the rump and backward from the withers, and terminates at the rib-loin juncture.

Why is the theory that long-bodied, stretchy animals produce higher yields of valuable retail cuts incorrect?

Lengthening the loin and rib sections also lengthens the lower-value flank and plate sections proportionally, resulting in no net percentage increase in high-value steaks.

Why is it biologically impossible to select for heavy muscling exclusively in the loin or round while selecting against the shoulder?

Skeletal muscles grow in concert across the entire body, so genetic selection for increased muscle in the hindquarter inevitably increases muscling in the forequarter.

What specific palatability defect causes intact male boar carcasses to be discounted relative to barrows?

The presence of objectionable sex-related flavor and odor compounds known as "boar odor."

Why are ewe carcasses more frequently classified into older ovine market categories (such as Yearling Mutton) earlier than wethers?

Ewes attain puberty and mature physiological characteristics at an earlier chronological age than castrated males.