References

Genetic Parameters of Pork Quality Loin-Ham Traits

One of the great challenges to the pork industry is to restore value to hams. The ‘Meat- Type’ hog era started in the 1950’s with a great emphasis on increasing loin and ham yields. At that time the ham was a premium cut and added much value to the total hog income. Today we find hams worth less than fat bellies and sometimes less than shoulders. Geneticists have been very successful in increasing the ham yield of carcasses even as market hog weights increased. Selection of seedstock for increased carcass lean has reduced the intramuscular fat or marbling of loins and hams. Food service operators complain that lack of marbling reduces the value of modern pork.

 

As loin and ham yields increased problems with processing and eating qualities became evident. Two major genes, HAL 1843 and Rendement Napole, are known to decrease pork quality. Modern slaughter plant speeds have challenges with uniform slaughter and chilling methods.

 

The National Pork Board (NPB) has conducted extensive pork quality research including loins (National Barrow Show Sire Progeny Tests, Terminal Sire Line National Genetic Evaluation Program, Maternal Line National Genetic Evaluation Program), loins and hams (1996-1997 National Barrow Show Sire Progeny Tests), loins and bellies (Genetics of Lean Efficiency Project, 1999-2000 National Barrow Show Sire Progeny Tests) loins, hams, and bellies (Quality Lean Growth Modeling Project).

 

Table 1. Pigs from NBS and GLE with known Rendement Napole and HAL 1843 genotypes

Breed Number pigs Number Sires Freq of RN-, % Freq of n, %
Berkshire 981 133 .024 .021
Chester White 326 43 .017 .014
Duroc 820 117 .003 .004
Hampshire 114 18 .590 .018
Landrace 253 34 .004 .079
Poland China 219 30 .096 .235
Spot 79 12 .038 .146
Yorkshire 641 106 .005 .011

 

Laboratory methods have been developed by scientists and commercially licensed to identify HAL 1843 and Rendement Napole genotypes. Tissue samples from most of the pigs from the 1996-2002 National Barrow Show Sire Progeny Tests (NBS) and the check-off funded Genetics of Lean Efficiency Project (GLE) have been evaluated by GeneSeek Labs to determine genotypes for both loci. All barrows and gilts were purebred. Gene frequencies for the mutant alleles (n for HAL 1843, RN- for Rendement Napole) are shown in Table 1.

 

Traits of growth, leg soundness, carcass yield, and loin quality are evaluated in each National Barrow Show Sire Progeny Test. During the 1996 and 1997 NBS tests a ham was taken from each carcass and sent to the Texas A&M University Meats Laboratory for yield, quality and cooking evaluation. Loins were sent to the Iowa State University Meats Laboratory for quality evaluation. The breed and sex representation of those pigs are shown in Table 2.

 

Table 2. Pigs from 1996-1997 NBS Ham Tests with known Rendement Napole and HAL 1843 genotypes

Breed Number pigs Number Sires Barrows Gilts
Berkshire 152 25 90 62
Chester White 30 43 21 9
Duroc 68 13 40 28
Hampshire 57 10 30 27
Landrace 101 15 62 39
Poland China 55 10 29 26
Spot 41 7 21 20
Yorkshire 106 18 64 42

 

Loin-Ham Traits

 

The muscles evaluated were:

  • Loin: Longissimus muscle at 11-12 rib
  • Inside Ham: Semimembranous muscle
  • Knuckle Ham: Quadriceps group
  • Outside Ham: Biceps femoris and semitendenosis muscle

 

A mixed linear model (SAS, 1999) included the fixed effects of slaughter date, breed, sex, breed by sex, HAL 1843 genotype, Rendement Napole genotype and the random effects of sire within breed, dam within breed. Results are shown in the following tables.

 

Table 3. Least Squares Means for Breed Effects of Loin L color score and Ham L* color score

  Loin L Inside ham L* Knuckle ham L* Outside ham L*
Berkshire 50.8a 54.4a 50.3a 54.7a
Chester White 52.1b 53.3a 51.8ab 54.6a
Duroc 52.3b 56.7b 54.5c 57.0b
Hampshire 49.7a 55.6ab 52.9bc 56.8b
Landrace 55.3d 54.7a 52.2b 55.1ab
Poland China 52.1b 53.7a 51.1ab 54.7a
Spot 53.4c 56.4b 52.7b 56.6b
Yorkshire 53.7c 54.8a 51.3ab 54.4a

* Means with the same superscript are not different (P< .05). Traits without superscripts have no differences among means (P<.05).

 

The largest color differences were found in loins where the range is from Hampshire, darkest at 49.7, to Landrace, pale at 55.3.

 

Table 4. Least Squares Means of Rendement Napole and HAL 1843 genotypes

Genotype Loin L Inside ham L* Knuckle ham L* Outside ham L*
. rn+/rn+ 51.6a 55.0 50.1a 55.5
RN-/rn+ 53.0b 55.4 53.8b 56.1
RN-/RN- 52.7b 54.4 52.5b 54.9
N/N 49.7a 54.9 51.8 54.7a
N/n 51.5b 55.0 52.4 56.3b

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

Loins become paler when they have either mutant gene.

  • Loin IMF: Percent total lipid by Fulch method
  • Inside IMF: Percent total lipid by Fulch method
  • Knuckle IMF: Percent total lipid by Fulch method
  • Outside IMF: Percent total lipid by Fulch method

 

Table 5. Least Squares Means for Breed Effect of Total Lipid Percent of Loin and Ham Muscles

Breed Loin, % Inside ham, % Knuckle ham, % Outside ham, %
Berkshire 2.58b 8.4a 4.3a 8.7a
Chester White 2.46b 5.7cd 4.1a 6.9bc
Duroc 3.12a 6.8bc 4.1a 7.8ab
Hampshire 2.08c 4.1d 3.5ab 7.8ab
Landrace 1.99c 4.2d 3.2b 7.1b
Poland China 2.18c 6.2c 4.2a 7.5ab
Spot 2.44b 7.7ab 4.3a 8.2ab
Yorkshire 1.77d 4.8d 3.3b 5.7c

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

There is a great deal of breed variation in total lipid content of the muscles. Loins and inside hams showed the greatest breed variation.

 

Table 6. Least Squares Means of Rendement Napole and HAL 1843 genotypes

Genotype Loin, % Inside ham, % Knuckle ham, % Outside ham, %
. rn+/rn+ 2.50a 6.1 3.7 8.8
RN-/rn+ 2.27b 6.0 3.9 6.8
RN-/RN- 2.22b 5.8 4.0 6.8
N/N 2.40a 6.2 3.9 7.5
N/n 2.19b 5.8 3.8 7.4

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

Mutant genes reduce total lipid content of loins.

  • Loin WHC: Filter paper exudate in grams
  • Loin cooking loss: Percent weight loss from cooking to 70 C
  • Inside WHC: Percent hanging drip loss
  • Knuckle WHC: Percent hanging drip loss
  • Outside WHC: Percent hanging drip loss

 

Table 7. Least Squares Means for Breed Effect for drip loss and cooking loss

Breed Loin exudate,g Loin cooking loss, % Inside ham drip loss,% Knuckle ham drip loss, % Outside ham drip loss, %
Berkshire .059a 21.4a 8.9a 9.4a 8.1a
Chester White .065b 22.7b 10.7bc 10.4ab 9.5bc
Duroc .072c 23.6c 11.5bc 11.2b 10.0c
Hampshire .062ab 23.4bc 10.7bc 10.6ab 8.4ab
Landrace .092e 24.4d 11.5c 11.4b 9.7c
Poland China .070bc 23.0bc 10.0b 9.7ab 9.2bc
Spot .084d 23.4bc 10.9bc 10.9b 9.8c
Yorkshire .082d 24.0cd 10.3b 10.6ab 9.0b

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

Large breed differences exist in these measures of water holding capacity. Case ready product and further processed product are better when quality pork is used.

 

Table 8. Least Squares Means for Rendement Napole and HAL 1843 genotypes

Genotype Loin exudate, g Loin cooking loss, % Inside ham drip loss, % Knuckle ham drip loss, % Outside ham drip loss, %
rn+/rn+ .060a 21.6a 9.7 9.0a 7.8a
RN-/rn+ .081b 24.2b 10.6 11.6b 9.5b
RN-/RN- .080b 23.8b 11.4 11.0b 10.3b
N/N .061a 22.3a 10.6 10.3 9.3
N/n .076b 23.8b 10.6 10.8 9.1

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

Mutant genes reduce the water holding capacity of loins and ham muscles.

  • Loin pH: Taken 24-36 hours postmortem
  • Inside pH: Taken 7 days postmortem
  • Knuckle pH: Taken 7 days postmortem
  • Outside pH: Taken 7 days postmortem

 

Table 9. Least Squares Means for Breed Effect of Ultimate Loin and Ham Muscle pH

Breed Loin pH Inside ham pH Knuckle ham pH Outside ham pH
Berkshire 5.67a 5.74a 5.85a 5.71a
Chester White 5.70a 5.69ab 5.74ab 5.62b
Duroc 5.58b 5.63b 5.59c 5.59b
Hampshire 5.59b 5.55b 5.63bc 5.53b
Landrace 5.47c 5.62b 5.68bc 5.59b
Poland China 5.59b 5.68b 5.77ab 5.60b
Spot 5.52c 5.60b 5.65bc 5.57b
Yorkshire 5.49c 5.57b 5.71b 5.57b

* Means with the same superscript are not different (P<.05). Traits without superscripts have no differences among means (P<.05).

 

Higher pH is associated with better processing quality. There are large breed differences for loins and smaller but consistent breed differences for ham muscles.

 

Table 10. Least Squares Means of Rendement Napole and HAL 1843 genotypes

Genotype Loin pH Inside ham pH Knuckle ham pH Outside ham pH
. rn+/rn+ 5.70a 5.68 5.85a 5.67a
RN-/rn+ 5.51b 5.58 5.65b 5.56b
RN-/RN- 5.51b 5.64 5.61b 5.56b
N/N 5.60a 5.64 5.71 5.60
N/n 5.56b 5.63 5.70 5.60

* Means with the same superscript are not different (P<.05). Traits without superscripts have no
differences among means (P<.05).

 

The mutant Rendement Napole allele causes a large reduction in ultimate pH for most muscles.

 

Heritabilities and genetic correlations

 

A mixed linear multivariate animal model (Miztal, Lin, Berger) was used to estimate variance and covariance components of loin and ham quality traits. Fixed effects were slaughter date, breed, and sex. Data was adjusted to normal HAL 1843 and Rendement Napole genotype. A three generation genetic relationship matrix was included in the model.

 

Heritabilities are shown on the diagonals and genetic correlations above the diagonals of the following matrices. Trait abbreviations are :

  • IMF: Total lipid percent
  • HUNT: Hunter L* color score
  • PH: Ultimate pH
  • WHC: Loin filter paper exudate or ham drip loss
  • CLSS: Percent cooking loss
    •   LOIN INSIDE HAM
    IMF HUNT _PH WHC CLSS IMF WHC _PH HUNT
    LOINIMF 0.496 0.085 0.219 -0.172 -0.139 0.81 -0.286 0.041 0.138
    LOINHUNT 0.143 0.343 -0.168 0.191 0.095 0.3 -0.335 -0.182 -0.074
    LOIN_PH 0.044 -0.456 0.477 -0.364 -0.667 0.02 0.226 0.682 -0.529
    LOINWHC -0.056 0.39 -0.278 0.441 0.341 -0.299 -0.234 -0.281 -0.363
    LOINCLSS -0.147 0.146 -0.315 0.099 0.197 -0.012 0.004 -0.552 0.42
    IHAMIMF 0.418 0.093 0.034 -0.082 -0.088 0.495 -0.019 0.07 0.425
    IHAMWHC -0.012 0.112 -0.11 0.029 0.1 -0.01 0.355 0.1 0.254
    IHAM_PH -0.03 -0.291 0.482 -0.115 -0.126 0.018 -0.169 0.247 -0.48
    IHAMHUNT 0.132 0.21 -0.218 0.037 0.061 0.28 0.104 -0.346 0.205
    KHAMIMF 0.116 0.001 0.02 -0.002 -0.031 0.261 -0.011 0.069 0.056
    KHAMWHC -0.026 0.149 -0.187 0.127 0.069 -0.061 0.276 -0.201 0.142
    KHAM_PH 0.033 0.088 0.093 0.095 -0.062 0.035 0.087 -0.05 -0.017
    KHAMHUNT 0.067 0.117 0.055 0.108 -0.059 0.062 0.126 -0.079 0.03
    OHAMIMF -0.037 -0.062 -0.101 -0.091 0.07 -0.043 -0.088 0.031 0.099
    OHAMWHC 0.078 0.132 0.027 0.126 -0.008 0.087 0.182 -0.105 0.02
    OHAM_PH -0.063 -0.045 -0.058 -0.073 0.05 -0.085 0.067 0.073 -0.051
    OHAMHUNT 0.08 -0.026 0.05 -0.011 0.007 0.086 -0.164 0.292 -0.017

     

    Conclusions

     

    The genetic correlations among loin and ham muscle traits indicate selection for loin quality would have favorable effects on ham quality.

     

    Both HAL 1843 and Rendement Napole mutant alleles reduce the processing quality of loins and hams.

     

    Breed differences of pork quality are large enough to exploit in both loins and hams.

      KNUCKLE HAM OUTSIDE HAM
    IMF WHC _PH HUNT IMF WHC _PH HUNT
    LOINIMF 0.204 -0.257 -0.045 0.01 0.008 -0.012 0.208 0.32
    LOINHUNT 0.256 -0.148 0.213 0.239 -0.21 0.283 -0.077 -0.034
    LOIN_PH -0.324 -0.343 0.208 0.176 -0.189 0.183 -0.275 -0.002
    LOINWHC -0.304 0.168 0.084 0.067 -0.082 0.093 0.261 -0.185
    LOINCLSS 0.2 0.109 -0.034 -0.011 -0.001 0.081 -0.149 -0.166
    IHAMIMF 0.519 -0.105 0.017 0.122 -0.061 0.069 0.199 0.245
    IHAMWHC 0.406 0.191 0.142 0.183 -0.11 0.189 -0.251 -0.348
    IHAM_PH -0.481 -0.087 -0.08 -0.086 0.097 -0.153 -0.01 0.277
    IHAMHUNT 0.774 0.342 -0.22 -0.143 0.187 -0.129 0.208 0.093
    KHAMIMF 0.124 0.29 0.016 0.104 -0.009 0.155 -0.003 -0.153
    KHAMWHC -0.019 0.263 -0.101 -0.081 0.16 -0.012 0.052 0.007
    KHAM_PH 0.016 0.189 0.534 0.992 -0.988 0.967 -0.458 -0.833
    KHAMHUNT 0.038 0.237 0.979 0.53 -0.986 0.969 -0.418 -0.821
    OHAMIMF -0.007 -0.157 -0.972 -0.962 0.475 -0.956 0.404 0.815
    OHAMWHC 0.051 0.273 0.904 0.888 -0.888 0.316 -0.524 -0.838
    OHAM_PH -0.106 0.076 -0.347 -0.317 0.332 -0.358 0.129 0.379
    OHAMHUNT 0.066 -0.181 -0.409 -0.377 0.351 -0.365 0.105 0.173