Genetics

Genetics of Pork Quality (Word '97 format)

STAGES

Determination of Pork Quality Traits

1. Color

   1. Quantitative Measurements

      1. Hunter L dark to light
          

         Color Score	Minolta L
         0 = black	100 = white
         1	61
         2	55
         3	50
         4	45
         5	35

         
          
      2. Hunter a + b
         1. red positive to green negative
         2. yellow positive to blue negative

   2. Color Score
      1=light to 5=dark
      • 1 and 5 are eliminated from carcass contests

2. Firmness/Wetness Score

   1. Very soft and very wet fluid accumulations
   2. Soft and watery
   3. Slightly firm and moist
   4. Firm and moderately dry
   5. Very firm and dry
   
   • 1 and 2 are eliminated from carcass contests

3. Ultimate ph
   24 hrs. post-slaughter
   range usually 5.0-6.2
   5.8 mean value
   Hampsires average 5.7

4. Marbling

   1. % intramuscular fat within the loin muscle
   2. Marbling score
      1=devoid, 2=traces, 3=small to modest, 4=moderate to slightly abundant, 5=moderately abundant
      1 and 5 are eliminated from carcass contests.

5. Tenderness

   1. Panel scores
   2. Instron score - force to move star shaped probe
   3. Warner Bratzler Sheer

Genetic Selection for Pork Quality

Pork Quality Traits

1. Are low to moderately heritable,
2. Tend to have desirable correlations with growth, undesirable correlations with backfat thickness.

Table 1

Loin Meat Quality Traits

Table 2

Results (2) & (3)

Table 3

Parameter Estimates

Table 4

Characteristics of pork form RN^- and rn⁺ animals

Quality of the Longissumus lumborum

Water holding characteristics

Methods of Selection

1. Individual selection
   Biopsy of a small core sample from live animal

   1. Information on the individual animal is desirable, but mixed results with low repeatability and low relationship with ultimate pork quality except for intramuscular fat.
   2. Marbling estimates based on Real-time ultrasound, or MRI

2. Calculation of EBV's based on sib and progeny information

   • Obtain carcass information at a pork processor
   • Easy measurements - marbling, firmness, color scores, moderately cut/measurements, PH, bioelectric impedance, hunter A and B
   • Difficult measurements, instron score, W-B shear % intra muscular fat, drip loss

3. Choice of Breeds or Lines

   • Choose breeds which combine to form a terminal cross pig with acceptable lean content and pork quality re: 1/4 Duroc in the terminal cross pig
   • Combine US and European lines

Problems

1. With different processing methods and rate of chill, phenotype and genetic variances may differ

2. Fat - type may affect visual marbling scores. More saturated fat may result in higher marbling scores at some percent intramuscular fat.

3. Dark muscle may score higher marbling scores at the same intramuscular fat.

4. Selection based on EBV's estimated from sib information is sib selection.  Sib selection requires a large number of sire familites and full-sib families (litters). This is especially true if backfat is undesirably relevant to pork quality because then very few sires will be desirable for both traits.

Other Pork Quality Traits of Concern

Some very lean European lines under .6 in backfat have very soft fat, separation of muscle groups and separation of the fat and lean over the loin? Some of these producers are feeding avian fat/vegetable oil blends.

Genetic or diet problem? Interaction between diet, genotype and feed intake?

Table of Economic Values

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